Criteria for Restoration of Longitudinal Barriers, Phase II (2021)

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155 CHAPTER 8 – EVALUATION OF GUARDRAIL POST DETERIORATION FOR THE G4(2W) The guardrail post is a fundamental component of a guardrail system and its response during a crash event is important to the overall performance of the system. The posts are intended to absorb energy as they rotate through the soil during collisions. If the posts do not have sufficient strength they will fracture prematurely, resulting in excessive deflection of the w- beam rail element which may lead to rail forces that exceed its capacity. As posts deteriorate, the strength of the posts decline; thus, it is important to develop a field-assessment procedure for correlating strength degradation of guardrail posts to its effects on the crash performance of the guardrail system. The focus of this chapter is the evaluation of the G4(2W) guardrail with various levels of post deterioration to quantify their effects on system performance. Wood posts are subject to decay and rot from several causes. The area at and just below the ground line is of great concern because the combination of moisture and air greatly promotes decay. Wood posts are also subject to inhabitation by ants and other small insects. The degradation of wood fibers takes place because insects create living spaces within the wood or by ingesting wood fibers for nutrients; in which case damage can occur within any portion of the wood post. There is no particular standard at this time for quantifying the degree of rot or deterioration in a guardrail post. The approach typically used is to simply replace any post with visible deterioration under the assumption that if rot is visible there is probably also a great deal of non-visible rot, especially just below the groundline. In many, if not most, cases however the rot begins just underneath the outer shell of the post and is thus hidden from view. The power industry has experienced similar problems with wooden utility poles. Like guardrail posts, utility poles remain in service for many years and can sometimes rot and deteriorate, often below ground. There are some destructive test techniques that involve drilling multiple large (e.g., ¾-inch diameter) holes in the pole and probing the interior but this would too greatly compromise strength if applied to guardrail posts. Several non-destructive techniques have been developed which have demonstrated reasonable accuracy in predicting breaking strength of utility poles based on the modulus of elasticity of the pole. These methods include static bending tests, stress wave propagation techniques, near infrared spectroscopy, and ultrasound to name a few.[Hron11; Tallavo09; Green06; Hendrick03; Hascall07] Another type of “non-destructive” test involves the use of a resistograph, which measures the torque of a 1/16” diameter drill bit as it is inserted into the wood. The torque is measured as a function of length along the drill bit so any interior rot, voids or areas of low density are reflected in the torque measurement. The results are compared to a baseline reading on healthy wood to determine level of degradation. The resistograph can also drill at a 45 degree angle to obtain an indication of the subsurface condition of the post. Since the drill bit is only 1/16-inch diameter it is not considered a destructive test and there is little negative effect on the post strength due to the very small size hole. The objectives of this study task were to develop a process for estimating the degree of deterioration of a guardrail post and to quantify the effects of various levels of post deterioration on the crash performance of the guardrail system.

156 Scope The scope of this study included: (1) obtaining field-extracted wood guardrail posts from State DOT maintenance garages, (2) measuring the degree of deterioration of the posts with a Resistograph, (3) performing pendulum impact tests to measure the strength and capacity of the posts with various levels of deterioration, (4) processing the pendulum tests and resistograph data to correlate levels of deterioration to strength degradation, and (5) using FEA to quantify the effects of various levels of post deterioration on overall guardrail crash performance. Procurement of Guardrail Post Test Articles The Ohio Department of Transportation (ODOT) provided 140 guardrail posts with various levels of deterioration for the test program. These posts were extracted from the ground from damaged guardrail installations in Ohio. It has not been confirmed, but all the posts are assumed to be of the Southern Yellow Pine (SYP) species, which is the post type primarily used in Ohio. The posts all had round cross-section with nominal diameter size of 8 inches. The actual diameter size varied from 6.45 inches to 9.15 inches with standard deviation of 0.62 inches. In some cases the smaller diameters were a result of shell loss due to deterioration. The post lengths varied from approximately 5 to 6 ft, with the two most common lengths being 5 ft – 6 inches and 5 ft – 10 inches. Figure 104 shows a photo of the guardrail posts provided by the Ohio DOT for use in the physical test program. In addition to the deteriorated posts, ODOT also donated three new (or unused) guardrail posts to the project so that the Resistograph measurements from the in-service posts could be compared directly to the corresponding values for new posts. Figure 104. Posts from Ohio DOT procured for the Physical Test Program.

157 Resistograph Measurements and Processing Resistograph Measurements The deterioration of each post was measured using an IML Resi-F400 S Resistograph, shown in Figure 105. The resistograph was equipped with a 1/16 inch in diameter drilling needle 19 5/16 inches long. The resistograph measurements were recorded at increments of approximately 0.004 inches of drilling depth. The measurements were taken just below, or at, the groundline where the highest levels of deterioration were visually evident. With the posts extracted from ground, this critical area of the post was readily accessible, so the measurements were made at 90 degrees to the post. Figure 105. IML Resi-F400 S Resistograph. Data Processing and Interpretation The data from the resistograph was then processed to develop a procedure to yield a single quantitative value representing the strength or capacity of the posts. The pendulum test program, which will be discussed later, involved the post mounted in a rigid foundation, in which the guardrail post was essentially a cantilevered beam with a concentrated load applied at the end of, and normal to, the post. The stresses in the post arise from the resulting bending moment, where the stress profile through the cross-section of a beam in pure bending can be calculated from the following equation: 𝜎 = 𝑀𝑐 𝐼 Where M is the bending moment, I is the moment of inertia of the beam, and c is the distance from the neutral axis of the beam. Since M and I are constants, the strain varies linearly through the cross-section, increasing from zero at the neutral axis to a maximum value at the outermost fiber of the beam. If the material is elastic and homogeneous then the stress also varies linearly through the cross-section. For a non-homogeneous material such as wood, on the other hand, the stress values vary through the cross-section as a function of the local wood modulus, as illustrated in the schematic in Figure 106.

158 Figure 106. Schematic of typical (a) Free-body and (b) strain and stress diagrams for non- homogeneous beam under bending load. From the free body diagram in Figure 106, equilibrium is achieved when the sum of the moments due to the internal forces at Point A are equal to the moment created by the applied force P times its distance L, as described by: ∫ 𝐹𝑑𝑦 = 𝑃𝐿 𝑟 −𝑟 If the internal force at Point A in Figure 106 is approximated in terms of discrete forces, Fi, acting at fixed increments, yi, through the cross-section of the post, as illustrated in Figure 107, then the equilibrium condition can be re-written as: ∑ 𝐹𝑖𝑦𝑖 = 𝑃𝐿 𝑁 𝑖=1 Figure 108 shows the resistograph results for one of the new posts (i.e., Post A), illustrating a typical drill-torque vs. depth plot through the cross section of a guardrail post. Note that the torque resistance is not constant through the cross-section due to the non-homogeneous nature of wood, and also tends to oscillate considerably at each increment as the needle passes through each ring (or layer) of the post. For the following calculations, the data is used in its raw form (i.e., unfiltered). P RA N.A. N.A. L ϵ σ N.A. N.A. (a) Free Body Diagram (b) Strain and Stress Diagram r-r r-r F

159 Figure 107. Schematic illustrating internal force distribution through cross-section of a circular shaped post. Figure 108. Resistograph results for Post A. The resistograph data is measured along the centerline of the post’s cross-section. It is assumed that the torque resistance amplitude at each point is directly proportional to the modulus (or strength) of the post fibers at that radial depth within the post. For example, the hashed cross- section of Figure 107 shows the overall area for the representative force, Fi, acting at y = yi. As wood posts age and deteriorate, the properties of the wood will differ depending on its depth within the post. As illustrated in Figure 109, the crosshatched region at y = yi includes points at multiple depth locations through the post, where the number of points increases as yi approaches zero (i.e., the neutral axis). Each of these points is associated with a local modulus, Ej, and a representative subarea, Aij, as illustrated in Figure 109. For example, the shaded area in Figure 109(a) is representative of the subarea bounded by the two outermost rings which correspond to radii r = y1 and r = y2 and the two vertical lines y = yi and y = yi+1. The properties of the post at yi xxxxxxxxx x F1 r yi N.A. N.A. FN Fi Fi+1 r 0 10 20 30 40 50 60 70 80 90 100 0 1 2 3 4 5 6 7 8 R e si st o gr ap h R e su lt s Depth (in)

160 this location are assumed to be the same as that measured at Point 1 (outer most data point circled in Figure 109), which was taken directly from the resistograph data. Likewise Figure 109(b) and Figure 109(c) illustrate the local subareas at y = yi associated with the resistograph data points measured at Point 2 and Point 3, respectively, for i=3. Figure 109. Schematic illustrating the local moduli and subareas associated with the various points through the post thickness at y = yi. Thus, for a given applied load, each data point from the resistograph can be converted to a “pseudo” force value using the following equation: 𝐹𝑖 ∗ = ∑ 𝐸𝑗 ∗𝐴𝑖𝑗 𝑖 𝑗=1 𝑦𝑖 𝑅 𝜖𝑅 Where, 𝐹𝑖∗ are the pseudo forces, 𝐸𝑗∗ are pseudo modulus values associated with the incremental subareas ΔAij, yi is the distance of the force Fi from the neutral axis of the post, R is the radius of the post and 𝜖𝑅is the value of strain at y = R. Note that the term 𝑦𝑖 𝑅 𝜖𝑅is the strain at yi. The total resisting “moment” of the post is then proportional to the pseudo moment defined by: 𝑀∗ = ∑ 𝐹𝑖 ∗𝑦𝑖 𝑁 𝑖=1 = 𝜖𝑅 𝑅 ∑ ∑ 𝐸𝑗 ∗𝐴𝑖𝑗𝑦𝑖 2 𝑖 𝑗=1 𝑁 𝑖=1 (1) The relationship between the strain 𝜖𝑅 and 𝐸𝑗∗ was not determined, so the value for 𝜖𝑅 was set to unity for calculations of M*. The subarea Aij , as illustrated previously in Figure 109, can be computed using the simple formula for defining the area bounded between two circles with limits of yi+1 to yi as: 𝐴𝑖𝑗 = ∫ [√𝑟𝑗 2 − 𝑦2 − √𝑟𝑗+1 2 − 𝑦2] 𝑑𝑦 𝑦𝑖 𝑦𝑖+1 The energy absorbed by the post is also meaningful for quantifying the performance of a guardrail post. The equation calculating internal strain energy is shown below. The constitutive behavior of wood is assumed linear for calculation of the strain energy (for the sake of simplification), which yields: yi 2xxxxxxxx x yi xxxxxxxxx 1 xxxxxxxx x yi (a) (b) (c) 3

161 𝑈 = ∫ 𝜎𝜀𝑑𝑉 ≈ ∑ 𝐴𝑖𝜎𝑖𝜖𝑖 = 𝑖 ∑ ∑ 𝐴𝑖𝑗 𝑖 𝑗 𝐸𝑗𝜖𝑖 2 = ∑ ∑ 𝐴𝑖𝑗 𝑖 𝑗 𝐸𝑗 𝑦𝑖 2 𝑅2 𝜖𝑅 2 𝑖𝑖 Where 𝜎𝑖, 𝜖𝑖and Ei are the stress, strain and modulus, respectively, of the wood post at each increment through the cross-section. Thus, a pseudo strain energy can be computed for the post by substituting E* for E in the above equation and rearranging such that: 𝑈∗ = 𝜖𝑅 2 𝑅2 ∑ ∑ 𝐴𝑖𝑗 𝑖 𝑗 𝐸𝑗 ∗𝑦𝑖 2 𝑖 (2) Statistics for Resistograph Measurement of Test Articles Resistograph measurements were taken for each of the 140 aged post specimens and the three new post specimens obtained from the Ohio DOT. The values for M* ranged from 162 to 3251 with a mean value of 1123 and standard deviation of 11.3. The values for U* ranged from 40.9 to 812.9 with mean of 294.6 and standard deviation of 140.9. Figure 110 and Figure 111 show the cumulative distribution function for M*and U*, respectively, which indicate relatively uniform distribution of scores. Figure 110. Cumulative distribution plot for M*. 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0 500 1000 1500 2000 2500 3000 3500 C D F (P e rc e n t Le ss ) M*

162 Figure 111. Cumulative distribution plot for U*. In some cases the resistograph data did not fall back to zero when the drilling needle passed through the back-side of the post. This indicated that the needle likely encountered a “check” or a knot at some point during the test that turned the needle from its straight path and affected subsequent results (e.g., friction and bending of the needle may have increased the resistance measurements). This was somewhat corrected in the data by estimating the most logical location for the start of the divergence and assuming that the error was increasing linearly for the duration of the test, as illustrated in Figure 112. A logical solution for avoiding this phenomenon would be to drill only half way through the diameter on each side of the post. Figure 112. Resistograph data corrected for drift. 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0 200 400 600 800 1000 C D F (P e rc e n t Le ss ) U* 0 10 20 30 40 50 60 70 80 90 100 0 1 2 3 4 5 6 7 8 9 R e si st o gr ap h R e su lt s Depth (in) Original data Corrected for drift data

163 Pendulum Testing of Post-in-Rigid-Foundation Scope Pendulum tests were conducted at the FOIL to assess the dynamic failure properties of the deteriorated posts. Two series of tests were performed. The target impact conditions for the first series of tests were a 2,372-lb rigid pendulum impacting the posts at an impact speed of 20 mph at a height of 21.5 inches above ground. A review of the tests results indicated that the inertial response of the posts may have significantly influenced the pendulum mounted accelerometer data. The 20 mph impact speed resulted in much more energy than was required to break the post so the excess energy resulted in extraneous signal ringing. Finding an impact speed just fast enough to consistently break the post would help provide a cleaner signal with less noise. Thus, a second series of tests was conducted in which the target impact speed was reduced to 10 mph. A total of 22 tests were conducted at 20 mph and a total of 39 tests were conducted at 10 mph. The complete test matrices are shown below in Table 39 and Table 40. In an earlier study by Hascal et. al t it was stated that, “As the moisture content of a wood post increases up to 23 percent, the strength of the wood fibers within the post decreases. Beyond 23 percent, the wood strength is fairly constant. In their actual use, the moisture content may exceed 23 percent, and therefore the posts would be saturated.”[Hascal07] In order to reduce the effects of moisture content, each wood post specimen was saturated prior to testing. Each specimen was cut to 66 inches long, weighed, and then soaked for several hours in an open water tank as shown in Figure 113. Only the portion of the posts that were to be embedded into the steel sleeve (i.e., below groundline) was submerged in the tank to achieve realistic saturation of the posts (i.e., saturation below the groundline and air-dried above the groundline). The pre-soaked post specimens were again weighed just prior to testing. The circumferences of the posts were measured at the top, at the groundline and at the bottom of the posts to estimate the average diameter of the post. The average diameter, post length and weight of the post were then used to calculate the wet density for each post. The number of rings for each post was counted and used to determine the average ring density for each post. The moisture content was measured immediately after each pendulum test at several points through the cross-section of the post along the break-line using an MT-10 moisture meter developed by AMPROBE. The moisture meter was not able to obtain accurate readings when the moisture content exceeded 50 percent. In those cases the moisture content was reported as “greater than 50 percent”.

164 Table 39. Test Series 13009 Group 1 (2,372-lb pendulum, velocity = 20 mph, impact point = 21.5 inches). bottom mid top (in) (lbs) (hours) (lbs) (in) (in) (in) (in3) (lb/ft3) (in) (rings/in) 13009B 9/24/2013 3 66 - - 61 23.5 24 24.5 3025.2 34.8 7.6 19 5.0 13009C 9/24/2013 1 66 - - 88 23.25 21.25 24.75 2798.5 54.3 6.8 30 8.9 13009D 9/24/2013 2 66 - - 52 22.375 22.38 22.875 2669.1 33.7 7.1 14 3.9 13009E 9/24/2013 7 66 - - 69 23.5 23.5 23.75 2921.1 40.8 7.5 30 8.0 13009F 9/24/2013 12 66 - - 67 22 20.75 22 2446.6 47.3 6.6 23 7.0 13009G 9/24/2013 4 66 - - 85 24.375 24 24.25 3078.0 47.7 7.6 18 4.7 13009H 9/25/2013 36 66 - - 74 23 20.5 22.5 2542.0 50.3 6.5 25 7.7 13009I 9/25/2013 14 66 - - 104 25.5 25.5 25 3370.7 53.3 8.1 30 7.4 13009J 9/25/2013 15 66 - - 58 21.25 22 23.75 2619.6 38.3 7.0 18 5.1 13009K 9/25/2013 B 66 - - 71 23 22.75 22.75 2738.2 44.8 7.2 21 5.8 13009L 9/25/2013 A 66 - - 72 23 22.75 22.75 2738.2 45.4 7.2 34 9.4 13009M 9/25/2013 13 66 - - 87 26.25 24.5 24.5 3304.5 45.5 7.8 25 6.4 13009N 9/26/2013 62 66 37.0 17.0 64 24 24.25 24.25 3067.4 36.1 7.7 25 6.5 13009O 9/26/2013 40 66 60.0 18.0 87 26.25 24.5 24.5 3304.5 45.5 7.8 28 7.2 13009P 9/26/2013 19 66 53.0 19.0 69 24.75 24.75 26.75 3392.9 35.1 7.9 18 4.6 13009Q 9/26/2013 22 66 76.0 19.5 100 28.5 28 28.5 4216.3 41.0 8.9 30 6.7 13009R 9/26/2013 18 66 71.0 20.0 72 24.25 24.5 25 3174.1 39.2 7.8 24 6.2 13009S 9/26/2013 46 66 83.0 20.5 116 28.5 28.75 27.5 4191.5 47.8 9.2 40 8.7 13009T 9/27/2013 74 60 35.0 17.0 42 20 20.75 22 2088.9 34.7 6.6 23 7.0 13009U 9/27/2013 41 60 58.0 17.5 61 24.5 23.5 23 2674.3 39.4 7.5 26 7.0 13009V 9/27/2013 38 66 46.0 18.0 58 20.75 21.25 22.25 2409.0 41.6 6.8 19 5.6 13009W 9/27/2013 39 66 42.0 18.5 53 20.25 20.25 20.25 2153.7 42.5 6.4 14 4.3 Test No. Test Date Post No. Initial Weight Soak TimeLength Number of Rings Ring Density Soak Weight Groundline Diameter Circumference Volume Wet Density

165 Table 40. Test Series 13009 Group 2 (2,372-lb pendulum, velocity = 10 mph, impact point = 21.5 inches). bottom mid top (in) (lbs) (hours) (lbs) (in) (in) (in) (in3) (lb/ft3) (in) (rings/in) 13009Y 10/1/2013 43 66.0 65.0 17.0 85 24.3 23.8 24.3 3046.3 48.2 7.6 22 5.8 13009Z 10/1/2013 56 66.0 71.0 18.5 92 25.5 25.8 24.8 3370.7 47.2 8.1 30 7.4 13009A1 10/1/2013 50 66.0 69.0 19.0 74 24.5 23.0 25.5 3109.8 41.1 7.4 47 12.7 13009B1 10/1/2013 31 66.0 59.0 19.5 70 23.5 24.3 24.3 3025.2 40.0 7.6 17 4.5 13009C1 10/1/2013 47 66.0 69.0 20.0 93 27.0 25.5 24.8 3482.5 46.1 8.0 27 6.8 13009D1 10/1/2013 55 66.0 51.0 20.5 63 22.3 22.5 23.5 2718.3 40.0 7.3 26 7.1 13009E1 10/1/2013 32 60.0 103.0 21.0 119 26.8 26.8 27.8 3502.2 58.7 8.8 26 5.9 13009F1 10/1/2013 88 60.0 41.0 21.5 56 23.0 23.8 24.3 2674.3 36.2 7.6 20 5.3 13009G1 10/2/2013 71 60.0 61.0 18.0 70 26.0 23.5 23.3 2807.8 43.1 7.6 30 7.9 13009H1 10/2/2013 30 60.0 67.0 18.5 73 26.0 25.3 24.5 3044.1 41.4 8.0 28 7.0 13009I1 10/2/2013 76 60.0 70.0 19.0 75 28.3 26.3 25.5 3395.3 38.2 8.4 30 7.2 13009J1 10/2/2013 49 66.0 70.0 19.5 76 26.3 24.3 23.3 3174.1 41.4 7.5 30 8.0 13009K1 10/2/2013 29 66.0 72.0 20.0 80 23.0 22.0 23.3 2718.3 50.9 7.0 25 7.1 13009L1 10/2/2013 92 66.0 74.0 20.5 78 25.5 25.3 23.8 3239.0 41.6 8.0 32 8.0 13009M1 10/2/2013 68 66.0 65.0 21.0 69 24.0 23.3 22.8 2859.5 41.7 7.4 35 9.5 13009N1 10/3/2013 17 66.0 71.0 18.0 76 25.0 25.5 25.5 3370.7 39.0 8.0 30 7.5 13009O1 10/3/2013 94 66.0 37.0 18.5 47 21.3 20.8 20.8 2297.8 35.3 6.6 20 6.1 13009P1 10/3/2013 44 66.0 61.0 19.0 80 24.0 23.3 23.0 2879.9 48.0 7.6 30 7.9 13009Q1 10/3/2013 53 66.0 52.0 19.5 68 25.0 24.3 25.8 3282.6 35.8 7.6 24 6.3 13009R1 10/3/2013 84 66.0 72.0 20.0 84 24.5 22.3 22.5 2798.5 51.9 6.6 30 9.1 13009S1 10/3/2013 21 66.0 97.0 20.5 109 29.0 25.8 23.8 3596.1 52.4 8.0 50 12.6 13009T1 10/3/2013 63 66.0 57.0 21.0 62 24.0 23.5 23.5 2941.8 36.4 7.5 30 8.0 13009U1 10/3/2013 65 60.0 58.0 21.5 68 26.3 24.3 23.5 2905.1 40.4 7.6 32 8.4 13009V1 10/8/2013 90 66.0 37.0 18.0 49 21.8 22.3 22.5 2580.7 32.8 7.0 16 4.6 13009W1 10/8/2013 118 66.0 63.0 18.5 79 25.3 25.5 24.8 3326.5 41.0 7.7 28 7.3 Ring DensityNumber of Rings Soak Weight Groundline Diameter Circumference Volume Wet Density Test No. Test Date Post No. Initial Weight Soak TimeLength

166 Table 40. [CONTINUED] Test Series 13009 Group 2 (2,372-lb pendulum, velocity = 10 mph, impact point = 21.5 inches). bottom mid top (in) (lbs) (hours) (lbs) (in) (in) (in) (in3) (lb/ft3) (in) (rings/in) 13009X1 10/8/2013 81 66.0 69.0 19.0 87 24.0 22.5 22.3 2758.3 54.5 6.7 22 6.6 13009Y1 10/8/2013 123 66.0 74.0 19.5 92 26.0 26.3 25.0 3482.5 45.7 8.3 19 4.6 13009Z1 10/8/2013 61 66.0 73.0 20.0 90 27.0 26.0 27.0 3734.8 41.6 8.2 25 6.1 13009A2 10/8/2013 67 66.0 68.0 20.5 83 25.5 25.5 26.0 3460.0 41.5 8.2 21 5.1 13009B2 10/8/2013 126 66.0 77.0 21.0 93 25.8 26.3 26.0 3550.4 45.3 8.3 29 7.0 13009C2 10/8/2013 91 66.0 76.0 22.5 93 27.5 27.0 25.5 3734.8 43.0 8.6 37 8.6 13009D2 10/9/2013 105 66.0 52.0 17.0 63 24.0 23.0 22.8 2839.1 38.3 7.0 17 4.9 13009 E2 10/9/2013 117 66.0 73.0 17.5 81 27.0 27.0 26.5 3781.7 37.0 8.6 25 5.8 13009F2 10/9/2013 129 66.0 58.0 18.0 79 23.0 23.0 23.3 2798.5 48.8 7.3 28 7.7 13009G2 10/9/2013 24 66.0 81.0 18.5 84 25.3 25.8 27.3 3573.2 40.6 8.4 30 7.1 13009H2 10/9/2013 35 66.0 83.0 19.0 86 26.8 25.5 25.0 3482.5 42.7 8.1 22 5.4 13009I2 10/9/2013 78 66.0 68.0 19.5 78 23.5 24.0 26.0 3152.6 42.8 7.6 24 6.3 13009J2 10/9/2013 111 66.0 68.0 20.0 71 24.0 24.5 24.8 3131.2 39.2 7.6 28 7.4 13009K2 10/9/2013 114 60.0 63.0 20.5 69 24.3 25.0 25.0 2924.8 40.8 8.0 35 8.8 Groundline Diameter Number of Rings Ring Density Soak Time Soak Weight Circumference Volume Wet Density Test No. Test Date Post No. Length Initial Weight

167 Figure 113. Photo of post specimen soaking in tank of water. Test Specimen Mounting Condition The tests were performed with the posts installed in a rigid steel sleeve, as shown in Figure 114. The sleeve was a 12 x 12 x ¼ inch steel tube fabricated from A500 Class B 58,000 psi structural steel. The top of the tube was reinforced with a 5-inch tall 13 x 13 x ½ inch steel tube welded to the main tube sleeve. The foundation sleeve was braced against the steel reinforced concrete wall on the inside of the ground-pit using a 7.4 ft long S20x86 structural steel section. The posts were mounted inside the sleeve at a nominal depth of 38 inches, except for the few cases in which the length of the post was too short (e.g., several of the posts were only 60 inches long, which resulted in an embedment of 32 inches). In all cases, the top mounting height of the posts was nominally 28 inches. The posts were held in place inside the sleeve using structural grade pine boards (e.g., 2x8) that were press-fit against the back-side of the sleeve using a 1.0-inch diameter grade 8 set-screw. Figure 114. Rigid steel sleeve used for post mounting.

168 Equipment and Instrumentation Pendulum Device The striker for the tests was a 2,372-lb concrete pendulum with a semi-rigid nose, as shown in Figure 115. The semi-rigid nose, which was developed by researchers from Virginia Tech during the first phase of this study, was fabricated from a wooden block and covered with sheet metal. [Gabler10] The radius of chamfer at the center of the impactor face was 6 inches, which was based on measurements of a 2006 Chevrolet 1500 pickup truck. [Gabler10] Figure 115. 2,372-lb pendulum device with semi-rigid nose. Accelerometers The pendulum was instrumented with three accelerometers mounted onto the backside of the pendulum mass. Two of the accelerometers recorded data in the x-direction (forward direction) and the third accelerometer recorded data in the z-direction (vertical direction). Figure 116 provides a schematic showing the locations of the accelerometers.

169 Figure 116. Schematic of the accelerometer instrumentation for the pendulum tests. Photography Cameras The tests were also recorded using four high-speed cameras with an operating speed of 500 frames per second and a digital video camera (∼30 fps). Figure 117 provides the specifications and the general placement of the high-speed cameras for the tests. The accelerometers and the high-speed video were triggered using pressure tape switches when the pendulum contacted the post. The test setup and results were also documented with photographs taken before and after each test.

170 Figure 117. High-speed camera specifications and placement. Impact Conditions Two test series were performed. In the first series (i.e., Test Series 13009 Group 1), the 2,372-lb pendulum struck the post at 21.5 inches above grade at an impact speed of 20 mph, which resulted in a total kinetic energy of the striker of 31.7 ft-kips. In the second series of tests (i.e., Test Series 13009 Group 2), the impact velocity was reduced to 10 mph, which resulted in a total kinetic energy of 7.92 kip-ft. The posts were oriented such that the post bolt-hole was in- line with the pendulum; which also coincided with the direction of measurement in the resistograph tests. NO. CAMERA LENS LENS (MM) ZOOM (MM) RESOLUTION (PIXELS) SPEED (FPS) LOCATION 1 K3 Nikon 18-35 35 1280 X 1024 500 Left Rear Iso 2 K3R Nikon 24-85 52 1280 X 1024 500 Right Perp. 3 K3 Nikon 35-105 105 1280 X 1024 500 Left Perp. 4 K3R Nikon 24-85 85 1280 X 1024 500 Right Rear Iso Y Axis X Axis (Y-353.56,X-633.98 cm) 2 3 1 (Y-576.07, X-0.00 cm) Pendulu m (Y-646.17,X-0.0 cm) 4 (Y-646.17,X-0.0 cm)

171 Results The x-channel accelerometer data was processed to obtain the accelerations of the pendulum during impact with the posts. The data was filtered using an SAE Class 60 filter with a cutoff frequency of 100 Hz. The impact force-time history response from each post was approximated by multiplying the acceleration-time history curves by the total mass of the pendulum. The acceleration data was then integrated to obtain velocity-time history, and again integrated to obtain the displacement-time history of the pendulum. This information was then used to generate force-deflection response of the posts during impact. The force-deflection curves were then integrated to obtain the energy-deflection curves. The results for each of the tests are shown in Appendix D for Test Series 1 and Appendix E for Test Series 2. The diameter of the posts varied significantly among the test specimens (i.e., 6.45 inches to 9.15 inches with a standard deviation of 0.61 inches). In some cases the reduction in diameter was due to deterioration, but there were also significant differences regarding the nominal diameter of the posts. Since the effects of diameter have already been incorporated into the weighted resistograph scores (i.e., SMOR* and SU*), it was not necessary to adjust for post diameter in the pendulum test results. Note that the objective was to develop a relationship between the resistograph score and the strength properties of the posts. Although the intent of the rigid foundation tube was to create a “fixed” condition on the post at the groundline, the posts sometimes failed inside the foundation tube below the groundline, as illustrate in Figure 118. As a result, the moment arm (i.e., the distance from the impact point to the break point) was slightly different in each test. It was therefore decided to compute post capacity in terms of maximum resistive moment rather than maximum force. One complication, however, was that the posts do not generally fail along plane sections, let alone a perpendicular plane. To obtain a rough estimate for the length of the moment arm in each test, the average distance from the impact point on the post to the break line on the front and back side of the post was used. Figure 118. Photo of Test 13009G1 showing Post 71 breaking below groundline.

172 Test Series 13009 Group 1 (20 mph Impact Speed) Table 41 provides the peak force, the strain energy at initiation of rupture, peak moment, and the energy at complete rupture for each post in Test Series 1. Figure 119 shows typical force and energy curves annotated to illustrate location of peak force, initial rupture energy, and rupture energy computed from the pendulum impact tests. The test summary sheets for this test series are shown in Appendix D. Figure 119. Typical force and energy curves annotated to illustrate location of peak force, initial rupture energy, and rupture energy computed from pendulum test results. The results from this first series of tests raised a few concerns: 1) the kinetic energy of the striker greatly exceeded the energy required to break the posts, 2) the “inertial effects” of the impact seemed to dominate the impact event and overshadow the bending response of the posts and 3) a significant portion of the energy measured in the impact was transferred into kinetic energy of the broken post. The term “inertial effects” is loosely defined here as the impulse required to initiate movement of the post’s mass upon impact. Also, from the high-speed video it was apparent that the broken posts were moving at significant speeds after the impact. It was not possible to accurately quantify the amount of energy expended in rupturing the post, since there was no convenient way to measure the speed of the broken post. From the test results, the highest energy expended in any test was 37 kip-in, while the majority of the tests expended less than 25 kip-in of energy. This was significantly less than the kinetic energy of the striker, which was 380.4 kip-in. Based on these issues along with the scatter in the test results, it was decided to reduce the impact speed to 10 mph for the second series of tests. The corresponding kinetic energy of the striker in the second series was 95 kip-in. 0 10 20 30 40 50 60 0 2 4 6 8 10 12 14 16 18 20 0 5 10 15 En er gy ( ki p -i n ) Fo rc e ( ki p ) Displacement (in) Force Energy Strain energy at the point of initial rupture Rupture energyPeak force

173 Table 41. Test Results for Test Series 13009 Group 1 (2,372-lb pendulum, velocity = 20 mph, impact point = 21.5 inches). Force Deflection Energy Moment* (in) (%) (lb) SM SU (kip) (in) (kip-in) kip-in (kip-in) 13009B 9/24/2013 3 5.0 7.6 43.0 61 0.2 0.2 5.8 1.5 6.4 131.2 6.7 13009C 9/24/2013 1 8.9 6.8 >50 88 0.1 0.1 9.1 0.8 6.7 205.7 7.4 13009D 9/24/2013 2 3.9 7.1 39.8 52 0.1 0.1 7.1 0.9 8.8 159.8 9.3 13009E 9/24/2013 7 8.0 7.5 - 69 0.6 0.6 9.4 0.8 11.9 212.4 12.0 13009F 9/24/2013 12 7.0 6.6 46.8 67 0.3 0.3 7.6 0.9 7.4 171.9 8.4 13009G 9/24/2013 4 4.7 7.6 - 85 0.8 0.7 10.5 0.8 14.6 235.8 17.8 13009H 9/25/2013 36 7.7 6.5 >50 74 0.3 0.3 8.2 2.4 8.7 184.2 9.3 13009I 9/25/2013 14 7.4 8.1 >50 104 0.3 0.3 13.6 1.0 14.2 305.6 17.7 13009J 9/25/2013 15 5.1 7.0 >50 58 0.2 0.2 8.2 1.0 6.4 184.9 8.5 13009K 9/25/2013 B 5.8 7.2 - 71 0.8 0.9 16.1 1.9 21.3 362.4 25.0 13009L 9/25/2013 A 9.4 7.2 - 72 0.8 0.9 19.1 2.2 32.2 429.4 37.2 13009M 9/25/2013 13 6.4 7.8 >50 87 0.4 0.4 15.0 2.2 16.6 336.9 16.7 13009N 9/26/2013 62 6.5 7.7 >50 64 0.2 0.2 - - - - - 13009O 9/26/2013 40 7.2 7.8 >50 87 0.3 0.3 2.4 1.1 4.9 54.8 7.2 13009P 9/26/2013 19 4.6 7.9 >50 69 0.3 0.3 7.1 0.8 5.1 159.0 6.6 13009Q 9/26/2013 22 6.7 8.9 47.7 100 0.5 0.5 8.5 5.0 31.1 191.1 35.1 13009R 9/26/2013 18 6.2 7.8 >50 72 0.6 0.6 10.1 0.8 11.6 227.2 12.4 13009S 9/26/2013 46 8.7 9.2 >50 116 0.6 0.5 9.5 0.9 7.1 214.2 10.3 13009T 9/27/2013 74 7.0 6.6 >50 42 0.1 0.2 6.4 2.3 8.7 144.8 9.9 13009U 9/27/2013 41 7.0 7.5 28.1 61 0.5 0.6 20.7 2.1 22.4 465.3 22.4 13009V 9/27/2013 38 5.6 6.8 >50 58 0.2 0.2 7.5 0.8 9.0 169.0 9.6 13009W 9/27/2013 39 4.3 6.4 >50 53 0.4 0.4 7.4 0.8 9.3 166.0 9.3 * Moment computed based on estimated moment arm of 22.5 inches. - Data was not collected. Weight Resistograph Score At Peak Force Rupture Energy Test No. Test Date Post No. Ring Density Ground- Line Moisture Content

174 Test Series 13009 Group 2 (10 mph Impact Speed) Table 42 provides the peak force, the strain energy at initiation of rupture, peak moment, and the energy at complete rupture for each post in Test Series 13009 Group 2. The test summary sheets for this test series are shown in Appendix E. For the 39 tests, the peak force ranged from 3.25 kips to 18.4 kips, with a mean of 9.32 kips and standard deviation of 3.75 kips. The strain energy of the post at the point of initial rupture ranged from 4 kip-in to 43.3 kip-in, with mean of 21.4 and standard deviation 11.5. The total energy absorbed by the post at the point of complete rupture ranged from 5.44 kip-in to 80.6 kip-in, with a mean of 27.7 and standard deviation of 16.0. These statistics are summarized in Table 43, and the cumulative distribution functions for these three strength capacity metrics are shown in Figures 120 through 122. Correlation of Resistograph Measurements to Test Results The data from Group 2 of Test Series 13009 were used to assess the relationship between the resistograph measurements to peak force and energy capacity of the posts. Figure 123 shows a plot of the peak impact force vs. M*; Figure 124 shows a plot of the maximum resistive moment vs. M*; Figure 125 shows a plot of the strain at initiation of rupture vs. U*; and Figure 126 shows a plot of the rupture energy vs. U*. The linear regression of the data for the peak force and peak moment curves yielded R2 values of 0.71 and 0.70, respectively, which indicated that both curves fit the data reasonably well. The linear regression fit of the energy at rupture initiation yielded an R2 value of 0.66, which indicated that this curve was also a reasonable fit. The linear regression for the rupture energy data, however, yielded R2 value of 0.43 which indicated a significant scatter in the data. From visual inspection of the resistograph results (see Appendix E), it was apparent that at least two of the resistograph measurements were in error. These were for Post 53 of Test 13009Q1 and Post 21 of Test 13009 S1, as shown in Figure 127 and Figure 128, respectively. The resistograph data for these two posts showed abnormally high readings for very local sections of the posts, which indicate that the drilling needle likely encountered a knot at those locations or an error occurred when performing the resistograph test. This error was not discovered until after the post was destroyed in the pendulum test, so the resistograph reading could not be retaken. Excluding these data from the results yields better correlation with the test results. Figure 129 and Figure 130 show the results for Peak Force vs. M* and Energy at Rupture Initiation vs. U*, respectively, for the revised data set. The resulting R2 values improved to 0.82 and 0.76 for these two correlation plots. In the plot for U* vs. Rupture Energy, there were two data points that appeared to be outliers (see Figure 126). These points correspond to Tests 13009T1 and 13009Y1. The rupture of the post was very ductile in those two cases, resulting in a relatively high energy absorption compared to the rupture energy in all other tests (refer to Appendix E). There were no obvious signs for why those two posts resulted in such marked difference in behavior compared to the other posts. For example, visual inspection of the resistograph data for these two posts did not indicate any apparent error in the data (see Figure 131 and Figure 132). Also, the impact test results did not show significant error regarding the plots for Force vs. M* or Energy at Rupture Initiation vs U* (see circled data points in Figure 129 and Figure 130).

175 Table 42. Test Results for Test Series 13009 Group 2 (2,372-lb pendulum, velocity = 10 mph, impact point = 21.5 inches). Force Deflection Energy Moment (in) (%) (lb) SM SU (kip) (in) (kip-in) kip-in (kip-in) 13009Y 10/1/2013 43 5.8 7.6 -999.0 85 0.6 0.6 9.9 2.5 12.7 230.8 18.1 13009Z 10/1/2013 56 7.4 8.1 45.1 92 0.7 0.6 7.6 3.8 21.3 194.3 24.3 13009A1 10/1/2013 50 12.7 7.4 -999.0 74 0.4 0.4 6.9 2.8 8.2 158.6 12.8 13009B1 10/1/2013 31 4.5 7.6 -999.0 70 0.2 0.2 4.2 2.4 6.4 97.6 7.6 13009C1 10/1/2013 47 6.8 8.0 0.0 93 0.6 0.6 5.2 2.7 16.4 127.3 18.4 13009D1 10/1/2013 55 7.1 7.3 37.7 63 0.6 0.6 8.8 3.0 15.0 228.3 21.6 13009E1 10/1/2013 32 5.9 8.8 -999.0 119 1.1 1.0 15.4 4.7 38.4 402.0 43.8 13009F1 10/1/2013 88 5.3 7.6 -999.0 56 0.1 0.1 4.9 3.6 10.6 108.4 10.8 13009G1 10/2/2013 71 7.9 7.6 42.2 70 0.7 0.7 9.5 2.5 26.9 230.6 30.9 13009H1 10/2/2013 30 7.0 8.0 43.6 73 0.8 0.8 12.2 3.5 41.2 288.2 45.7 13009I1 10/2/2013 76 7.2 8.4 47.6 75 1.2 1.1 18.4 5.1 42.4 412.7 42.5 13009J1 10/2/2013 49 8.0 7.5 36.6 76 0.3 0.3 9.8 2.4 18.4 247.9 24.8 13009K1 10/2/2013 29 7.1 7.0 50.0 80 0.6 0.7 7.8 3.9 20.7 193.3 24.3 13009L1 10/2/2013 92 8.0 8.0 44.5 78 1.2 1.1 13.7 4.0 36.6 339.1 42.9 13009M1 10/2/2013 68 9.5 7.4 47.2 69 0.9 1.0 14.8 4.4 32.0 354.8 34.9 13009N1 10/3/2013 17 7.5 8.0 48.0 76 0.4 0.4 7.3 2.2 12.9 162.7 16.2 13009O1 10/3/2013 94 6.1 6.6 50.0 47 0.2 0.3 3.8 2.1 5.3 86.7 6.3 13009P1 10/3/2013 44 7.9 7.6 50.0 80 0.4 0.4 9.3 3.5 22.3 257.5 22.9 13009Q1 10/3/2013 53 6.3 7.6 47.6 68 0.7 0.7 4.3 1.1 4.0 97.2 7.8 13009R1 10/3/2013 84 9.1 6.6 49.7 84 0.4 0.5 8.0 2.7 21.7 175.3 23.0 13009S1 10/3/2013 21 12.6 8.0 50.0 109 0.8 0.8 8.5 2.3 12.5 217.8 18.5 13009T1 10/3/2013 63 8.0 7.5 37.3 62 0.7 0.7 9.7 7.6 28.0 213.2 61.5 13009U1 10/3/2013 65 8.4 7.6 50 68 0.3 0.3 8.2 3.6 14.5 186.0 17.8 13009V1 10/8/2013 90 4.6 7.0 50 49 0.1 0.1 3.2 2.4 6.7 70.6 6.8 13009W1 10/8/2013 118 7.3 7.7 50 79 0.3 0.3 5.3 2.1 6.7 121.0 9.7 At Peak Force Rupture Energy Moisture Content Weight Resistograph Score Test No. Test Date Post No. Ring Density Ground- Line

176 Table 42. [CONTINUED] Test Results for Test Series 13009 Group 2 (2,372-lb pendulum, velocity = 10 mph, impact point = 21.5 inches). Force Deflection Energy Moment (in) (%) (lb) SM SU (kip) (in) (kip-in) kip-in (kip-in) 13009X1 10/8/2013 81 6.6 6.7 50 87 0.3 0.4 6.1 4.0 18.0 141.3 30.7 13009Y1 10/8/2013 123 4.6 8.3 50 92 0.7 0.6 9.2 3.2 19.4 217.8 80.6 13009Z1 10/8/2013 61 6.1 8.2 45.5 90 0.7 0.7 11.6 4.4 35.2 294.2 43.5 13009A2 10/8/2013 67 5.1 8.2 50 83 0.8 0.8 10.6 3.5 22.2 239.5 26.0 13009B2 10/8/2013 126 7.0 8.3 50 93 1.0 0.9 13.1 5.0 43.3 304.2 47.2 13009C2 10/8/2013 91 8.6 8.6 46.16 93 1.1 1.0 17.5 3.8 28.6 364.1 36.8 13009D2 10/9/2013 105 4.9 7 50 63 0.2 0.2 5.0 2.2 5.4 121.1 5.4 13009 E2 10/9/2013 117 5.8 8.6 46.2 81 0.4 0.4 9.6 3.5 18.2 227.5 18.3 13009F2 10/9/2013 129 7.7 7.25 50 79 0.4 0.4 6.5 3.4 13.4 165.0 19.9 13009G2 10/9/2013 24 7.1 8.4 50 84 0.6 0.6 12.6 3.6 27.4 290.4 29.6 13009H2 10/9/2013 35 5.4 8.1 50 86 0.7 0.7 7.0 2.2 22.2 160.3 25.8 13009I2 10/9/2013 78 6.3 7.6 36.28 78 0.9 0.9 13.8 5.0 39.5 330.4 44.5 13009J2 10/9/2013 111 7.4 7.6 50 71 0.7 0.8 12.8 4.0 28.8 309.3 40.4 13009K2 10/9/2013 114 8.8 8 47.84 69 0.8 0.8 11.6 4.6 31.9 268.8 33.3 Moisture Content Weight Resistograph Score At Peak Force Rupture Energy Test No. Test Date Post No. Ring Density Ground- Line

177 Table 43. Statistics for Post Strength Capacity from Pendulum Test Series 13009 (Group 2). Figure 120. Cumulative distribution plot for the peak force values measured in Test Series 13009 (Group 2). Figure 121. Cumulative distribution plot for the strain energy in the post at initiation of rupture measured in Test Series 13009 (Group 2). Mean Std. Dev. Min Max Peak Force 9.32 3.75 3.25 18.44 Energy at Initial fracture 21.42 11.47 4.00 43.30 Energy at Complete Rupture 27.68 16.04 5.44 80.60 Post Strength Statistics Capacity Measure 0% 20% 40% 60% 80% 100% 0 5 10 15 20 C D F (P e rc e n t Le ss ) Peak Force (kips) 0% 20% 40% 60% 80% 100% 0 10 20 30 40 50 C D F (P e rc e n t Le ss ) Energy at Initiation of Rupture (kip-in)

178 Figure 122. Cumulative distribution plot for the total energy absorbed by the post at complete rupture measured in Test Series 13009 (Group 2). Figure 123. Peak Force vs. M* for Test Series 13009 Group 2 (all data). 0% 20% 40% 60% 80% 100% 0 20 40 60 80 100 C D F (P e rc e n t Le ss ) Energy at Complete Rupture (kip-in) y = 0.0051x + 2.8429 R² = 0.7131 0 2 4 6 8 10 12 14 16 18 20 0 500 1000 1500 2000 2500 3000 P e ak F o rc e C ap ac it y (k ip s) Pseudo Moment, M*

179 Figure 124. Peak Moment vs. M* for Test Series 13009 Group 2 (all data). Figure 125. Energy at rupture initiation vs. U* for Test Series 13009 Group 2 (all data). y = 0.1187x + 69.3504 R² = 0.7041 0 50 100 150 200 250 300 350 400 450 0 500 1000 1500 2000 2500 3000 P e ak M o m e n t C ap ac it y (k ip -i n ) Pseudo Moment, M* y = 0.0610x + 1.2423 R² = 0.6571 0 5 10 15 20 25 30 35 40 45 50 0 100 200 300 400 500 600 700 En e rg y at In it ia l B re ak ( ki p -i n ) Pseudo Energy, U*

180 Figure 126. Rupture Energy vs. U* for Test Series 13009 group 2 (all data). y = 0.0698x + 4.4814 R² = 0.4297 0 10 20 30 40 50 60 70 80 90 0 100 200 300 400 500 600 700 En e rg y at R u p tu re ( ki p -i n ) Pseudo Energy, U* 13009T1 13009Y1

181 Figure 127. Test Summary Sheet for Test 13009Q1. Test Information_______________________ Test Number: 13009Q1 Test Date: 03-Oct-2013 Post Properties________________________ Post Number: 53 Post Type: Round SYP Post Length: 66 inches Post Diameter: 7.64 inches Moisture Content: 47.62% Ring Density (avg.): 6.2 per inch Resi Score SMOR: 0.68 Resi Score SU: 0.67 Pendulum Properties___________________ Weight: 2,372 lb Impact Speed: 10 mph Impact Height: 21.5 inches Fractured Post 0.050 sec 0.075 sec 0.100 sec 0.025 sec Ring density at bottom of post

182 Figure 128. Test Summary Sheet for Test 13009S1. Test Information_______________________ Test Number: 13009S1 Test Date: 03-Oct-2013 Post Properties________________________ Post Number: 21 Post Type: Round SYP Post Length: 66 inches Post Diameter: 7.96 inches Moisture Content:  50% Ring Density (avg.): 12.2 per inch Resi Score SMOR: 0.82 Resi Score SU: 0.77 Pendulum Properties___________________ Weight: 2,372 lb Impact Speed: 10 mph Impact Height: 21.5 inches Fractured Post 0.050 sec 0.075 sec 0.100 sec 0.025 sec Ring density at bottom of post Drift Correction Applied

183 Figure 129. Peak Force vs. M* for Test Series 13009 Group 2 (revised data set). Figure 130. Energy at Initial Break vs. U* for Test Series 13009 Group 2 (revised data set). y = 0.0051x + 2.8429 R² = 0.7131 0 2 4 6 8 10 12 14 16 18 20 0 500 1000 1500 2000 2500 3000 P ea k Fo rc e C ap ac it y (k ip s) Pseudo Moment, M* S1x Q1x Y 0. 2 .988 2 = 0.820 T1 Y1 y = 0.0610x + 1.2423 R² = 0.6571 0 5 10 15 20 25 30 35 40 45 50 0 100 200 300 400 500 600 700 En e rg y at In it ia l B re ak ( ki p -i n ) Pseudo Energy, U* Y=0.063x + 1.368 R2 = 0.764 S1x Q1x T1 Y1

184 Figure 131. Test Summary Sheet for Test 13009T1. Test Information_______________________ Test Number: 13009T1 Test Date: 03-Oct-2013 Post Properties________________________ Post Number: 63 Post Type: Round SYP Post Length: 66 inches Post Diameter: 7.48 inches Moisture Content: 37.26% Ring Density (avg.): 8.0 per inch Resi Score SMOR: 0.69 Resi Score SU: 0.75 Pendulum Properties___________________ Weight: 2,372 lb Impact Speed: 10 mph Impact Height: 21.5 inches Fractured Post 0.050 sec 0.075 sec 0.100 sec 0.025 sec Ring density at bottom of post 0 10 20 30 40 50 60 0 2 4 6 8 10 12 14 16 18 20 0 5 10 15 En er gy ( ki p -i n ) Fo rc e ( ki p ) Displacement (in) Force Energy Drift Correction Applied

185 Figure 132. Test summary sheet for Test 13009Y1. 0 10 20 30 40 50 60 70 80 90 100 0 2 4 6 8 10 12 14 16 18 20 0 5 10 15 En er gy ( ki p -i n ) Fo rc e ( ki p ) Displacement (in) Force Energy Test Information_______________________ Test Number: 13009Y1 Test Date: 08-Oct-2013 Post Properties________________________ Post Number: 123 Post Type: Round SYP Post Length: 66 inches Post Diameter: 8.28 inches Moisture Content:  50% Ring Density (avg.): 4.6 per inch Resi Score SMOR: 0.66 Resi Score SU: 0.61 Pendulum Properties___________________ Weight: 2,372 lb Impact Speed: 10 mph Impact Height: 21.5 inches Fractured Post 0.050 sec 0.025 sec Ring density at bottom of post 0.075 sec 0.100 sec Drift Correction Applied

186 Quantifying Wood Post Deterioration Damage Levels The pendulum impact tests conducted in Test Series 13009 were used to establish four levels of damage for deteriorated guardrail posts. For the assessment, only those tests with post diameters ranging from 8.0 to 8.2 inches were selected in order to eliminate the effects of post size. There were a total of 10 tests that met this criterion. These tests were then sorted based on strain energy absorbed by the post at the time of fracture initiation. The results are shown in Table 44 and in Figures 133 - 135. The four deterioration levels are summarized in Table 45 in terms of force capacity and energy capacity. Figure 136 shows examples of aged posts corresponding to deterioration levels DL1 through DL3. For convenience the values for pseudo moment M* and the pseudo energy U* were normalized based on their values at the threshold of Damage Level 1 (DL1), such that for scores greater than 1 the post is considered undamaged. Figure 137 shows a graphical representation of damage levels with respect to resi-score SM* and load capacity; and Figure 138 shows a graphical representation of the damage levels with respect to resi-score, SU, and strain energy capacity. The values for M* and U* are computed slightly differently, but when normalized the resulting scores corresponding to each of the damage levels are essentially identical; thus, either score may be used. The fourth column of Table 45 shows the damage level in terms of resistograph scores and the last column of Table 45 presents the damage levels in terms of relative capacity. Therefore, if post strength is measured or otherwise determined in the field via alternative means (e.g., stress wave techniques, force-deflection techniques, etc.) then the relative capacity may be used to identify damage level.

187 Table 44. Deterioration damage levels for posts in Test 13009 Series 2 based on strain energy. Force Deflection Energy Moment (in) (%) (lb) SM SU (kip) (in) (kip-in) kip-in (kip-in) 13009H1 10/2/2013 30 7.0 8.0 43.6 73 0.8 0.8 12.2 3.5 41.2 288.2 45.7 13009L1 10/2/2013 92 8.0 8.0 44.5 78 1.2 1.1 13.7 4.0 36.6 339.1 42.9 13009Z1 10/8/2013 61 6.1 8.2 45.5 90 0.7 0.7 11.6 4.4 35.2 294.2 43.5 13009K2 10/9/2013 114 8.8 8.0 47.8 69 0.8 0.8 11.6 4.6 31.9 268.8 33.3 13009H2 10/9/2013 35 5.4 8.1 50.0 86 0.7 0.7 7.0 2.2 22.2 160.3 25.8 13009A2 10/8/2013 67 5.1 8.2 50.0 83 0.8 0.8 10.6 3.5 22.2 239.5 26.0 13009Z 10/1/2013 56 7.4 8.1 45.1 92 0.7 0.6 7.6 3.8 21.3 194.3 24.3 13009C1 10/1/2013 47 6.8 8.0 0.0 93 0.6 0.6 5.2 2.7 16.4 127.3 18.4 13009N1 10/3/2013 17 7.5 8.0 48.0 76 0.4 0.4 7.3 2.2 12.9 162.7 16.2 13009S1 10/3/2013 21 12.6 8.0 50.0 109 0.8 0.8 8.5 2.3 12.5 217.8 18.5 Rupture EnergyDamage Level DL1 Test No. Test Date Post No. Ring Density Ground- Line Moisture Content DL2 DL3 Weight Resistograph Score At Peak Force

188 Figure 133. Pendulum impact tests from Series 13009 corresponding to deterioration damage level 1 (DL1). Figure 134. Pendulum impact tests from Series 13009 corresponding to deterioration damage level 2 (DL2). Figure 135. Pendulum impact tests from Series 13009 corresponding to deterioration damage level 3 (DL3). 0 2 4 6 8 10 12 14 16 0 2 4 6 8 10 12 14 16 Fo rc e ( lk ip ) Displacement (in) Damage Level 1 Z1 (8.2 in) L1 (8.0 in) K2 (8.0 in) H1 (8.0 in) 0 2 4 6 8 10 12 14 16 0 5 10 15 20 Fo rc e ( lk ip ) Displacement (in) Damage level 2 H2 (8.1 in) A2 (8.2 in) Z (8.1 in) 0 2 4 6 8 10 12 14 16 0 5 10 15 20 Fo rc e ( lk ip ) Displacement (in) Damage Level 3 S1 (8.0 in) N1 (8.0 in) C1 (8.0 in)

189 Table 45. Damage levels for guardrail post deterioration. Figure 136. Examples of aged posts corresponding to deterioration levels DL1 through DL3. General Resi Score Peak Force Strain Energy (kips) (kip-in) 0 (new) > 14 > 35 >1 100% 1 12 - 15 26 - 40 0.83 - 1.0 83% 2 7 - 13 20 - 30 0.57 - 0.83 57% 3 < 9 < 20 < 0.57 < 57% Damage Level Capacity 8-inch Round Posts (nominal) SU or SM Relative Capacity DL2 7.6 21.3 0.67 7-13 20-30 0.57 - 0.83 Force (k): Energy (k-in): Resi: DL3 3.8 5.3 0.24 < 9 < 20 < 0.57 DL1 14.8 32 0.95 12-15 26-40 0.83 - 1.0 Score Criteria Score CriteriaScore Criteria

190 Figure 137. Graphical representation of damage levels with respect to resi-score, SM, and load capacity. Figure 138. Graphical representation of damage levels with respect to resi-score, SU, and strain energy capacity. DL0 DL1 DL2 DL3 0 2 4 6 8 10 12 14 16 18 20 0 0.2 0.4 0.6 0.8 1.2 Fo rc e C ap ac it y (k ip s) Normalized Score (SM*) 1.00.57 0.83 7-13 FC >14 12-15 Fc < 9 0 500 1000 1500 2000 25002104 Pseudo Moment, M* 0 5 10 15 20 25 30 35 40 45 50 0 0.2 0.4 0.6 0.8 1.2 DL0 DL1 DL2 DL3 1.00.57 0.83 15-30 EC > 36 26-40 EC < 20 En e rg y C ap ac it y (k ip -i n ) 0 100 200 300 400 500 600 Normalized Score (SU*) Pseudo Energy, E*

191 Visual and Auditory Cues If strength and/or deterioration measurement tools are not available, then visual inspection and “sounding” procedures should be utilized by experienced maintenance personnel to assess the soundness of the posts. Refer to Figure 136 in regard to the following damage assessment cues. DL3: Significant deterioration at top of post is usually evident. Deterioration is often deep (>1”) and covers the full cross-section of the post. Mildew or mold is often present on the side of the post near the ground line; and the post is audibly very soft (punky) when struck with a hammer near the groundline. DL2: Often marked by shallow deterioration at top of post (<1”), extending over most if not all the cross-section. Post is audibly soft but not punky when struck by a hammer. DL1: Generally there is no deterioration evident at the top of the post. In some cases, however, signs of deterioration may exist near the top-center of post, but will not extend to the outer shell. The post is relatively sound when struck with a hammer. Pendulum Testing of Posts-in-Soil Scope The tests were categorized into two groups. Group 1 was conducted to establish a baseline soil density, percent compaction and moisture content to be used throughout the remainder of the study. The purpose of this group of tests was to ensure consistency in soil stiffness and also to confirm that the soil conditions met the minimum strength requirements set forth in MASH.[MASH09] The second group of tests were designed to evaluate the impact response of the post-soil system for various levels of post degradation. Based on the results from the first group of tests; however, it was decided that the second group of tests would not provide additional information and was therefore not performed. The target impact conditions for Test Group 1 included a 2,372-lb rigid pendulum impacting the posts at an impact speed of 20 mph at a height of 24.88 inches above ground, which was consistent with the test procedures in MASH for measuring soil strength. The posts were 72 inches long and embedded 40 inches in the soil. Two types of posts were used in the study: 1) a steel W6x16 post and 2) round wood posts with diameters ranging from 7.2 to 8.4 inches. The target impact conditions for Test Group 2 included a 2,372-lb rigid pendulum impacting the posts at an impact speed of 20 mph at a height of 21.5 inches above ground; a post-length of 68-72 inches, and a post-embedment depth of 40 inches in the soil. The post specimens in these tests were to include both new and used posts. Several additional new posts were donated to the study by Road Systems, Inc. The used posts were to be drawn from the lot of guardrail posts extracted from damaged guardrail systems in Ohio (refer to Figure 104). The test specimens were sub-categorized based on their resistograph scores. DL0 in Table 47 denotes damage level 0, which corresponds to new post conditions. DL1 denotes damage level 1 which represents a low level of deterioration. Likewise, DL2 and DL3 represent increasing levels of deterioration. The test matrices for the two test groups are shown below in Table 46 and Table 47.

192 The soil for all tests conformed to Grading B of AASHTO M147-95 and was compacted in 6-inch lifts using a pneumatic tamper. The density, moisture content and degree of compaction of the soil was measured in front of and behind the post after each compaction process using a Troxler-model 3440 Surface Moisture-Density Gauge. There were a total of twelve readings which were averaged to determine the effective soil conditions.

193 Table 46. Post-in-Soil Test Group 1 (2,372-lb pendulum, v = 20 mph, impact point = 24.88 inches, embedment 40 inches). Table 47. Post-in-Soil Test Group 2 (2,372-lb pendulum, v = 20 mph, impact point = 21.5 inches, embedment 40 inches). Impact Weight Speed Point SM SU (in) (lbs) (hours) (lbs) (in3) (lb/ft3) (in) (rings/in) (pcf) (%) (%) (lbs) (mph) (in) Preliminary Tests 13010A 10/23/2013 102 0.63 0.69 68.0 96.0 18.0 106 1936.7 94.6 7.6 8.4 148.3 4.0 98.7 2372 20 21.5 13010B 10/24/2013 54 1.04 0.95 68.0 90.0 N/A 90 2179.5 71.4 8.4 12.0 2372 20 21.5 13010C 10/29/2013 C 0.51 0.54 68.0 65.0 17.0 69 1683.9 70.8 7.3 8.2 142.1 3.6 94.7 2372 20 21.5 Soil Strength Tests 13010D 10/31/2013 W6x16 - - 72.0 - - - - - - 0.0 143.5 3.8 95.6 2372 20 24.9 13010E 11/4/2013 W6x16 - - 72.0 - - - - - - 0.0 132.4 3.1 88.1 2372 20 24.9 13010F 11/6/2013 W6x16 - - 72.0 - - - - - - 0.0 138.4 3.3 92.1 2372 20 24.9 13010G 11/8/2013 57 0.86 0.97 68.0 71.0 17.0 69 1671.7 71.3 7.2 9.2 138.6 3.4 92.3 2372 20 24.9 13010H 12/16/2013 D 72.0 81.0 - 81 1745.4 80.2 7.5 6.4 142.4 6.2 94.8 2372 20 24.9 13010I 12/18/2013 E 72.0 82.0 - 82 1770.4 80.0 7.4 4.1 - - - 2372 10 24.9 Test Date Impact Conditons PendulumDry Density Moisture Content Compaction Soil Data Test No. Ring DensityResi Score Post Data Post No. Length Initial Weight Soak Time Soak Weight Volume Wet Density Groundline Diameter Impact Weight Speed Point SMOR SU (in) (lbs) (hours) (lbs) (in3) (lb/ft3) (in) (rings/in) (pcf) (%) (%) (lbs) (mph) (in) 13010J TBD TBD DL0 2372 20 21.5 13013L TBD TBD DL0 2372 20 21.5 13013M TBD TBD DL0 2372 20 21.5 13013N TBD TBD DL1 2372 20 21.5 13013O TBD TBD DL1 2372 20 21.5 13013P TBD TBD DL1 2372 20 21.5 13013Q TBD TBD DL2 2372 20 21.5 13013R TBD TBD DL2 2372 20 21.5 13010S TBD TBD DL2 2372 20 21.5 13010T TBD TBD DL3 2372 20 21.5 13010U TBD TBD DL3 2372 20 21.5 13010V TBD TBD DL3 2372 20 21.5 Impact Conditons Pendulum Test No. Test Date Post Data Resi Score BASELINE SOIL STIFFNESS Density ≈ 138 pcf Compaction ≈ 92% Moisture Content ≈ 3.4% Soil Data Post No. Length Initial Weight Soak Time Soak Weight Volume Wet Density Groundline Diameter Ring Density Dry Density Moisture Content Compaction

194 Soil Strength Tests Preliminary Tests The first three tests (i.e., 13010A, 13010B and 13010C) involved wooden posts selected from the lot of used posts obtained from the Ohio DOT. The resistograph score for Post No. 54 in Test 13010B was relatively high, as shown in Table 47. As such, it was expected that the post would rotate through the soil during the test without fracturing the post, and that the results could then be used to quantify soil stiffness. All the tests, however, resulted in complete rupture of the posts with relatively little disturbance of the soil, as illustrated in Figure 139. Additional results can be found in Appendix F. The soil for these tests was compacted to a dry density of 142-148 pcf, corresponding to 95-99 percent soil compaction. It was apparent from these results that the soil was considerably stronger than the standard soil conditions recommended in MASH. It was then decided that soil stiffness tests would be carried out using the recommended procedures in MASH (which involves a rigid W6x16 steel post) to establish the baseline soil conditions to be used in the remainder of the study. Figure 139. Tests 13010A, B and C resulted in relatively little soil displacement. Steel W6x16 Post Tests Tests 13010 D, 13010E and 13010F were performed using a W6x16 steel section post. The post was 72 inches long and embedded 40 inches in the soil. The 2,372-lb pendulum struck the posts at 24.88 inches above ground at an impact speed of 20 mph. Three levels of soil compaction were evaluated:  Test 13010D: 96 percent soil compaction with an average soil density of 144 pcf.  Test 13010E: 88 percent soil compaction with an average soil density of 132 pcf.  Test 13010F: 92 percent soil compaction with average soil density of 138 pcf. The results of these tests are shown in Figure 140 and Figure 141. The dashed line in Figure 140 represents the minimum strength requirements for the soil. The soil test with 96 percent compaction resulted in a peak impact force of 24 kips with total energy absorption of 317 kip-in. The soil test with 92 percent compaction resulted in a peak impact force of 13.2 kips with total energy absorption of 244 kip-in. The soil test with 88 percent compaction resulted in a peak Test 13010B Test 13010CTest 13010A

195 impact force of 12.3 kips with total energy absorption of 86.6 kip-in. The results clearly show that for 96 percent soil compaction (i.e., soil conditions used in the preliminary tests) the soil strength greatly exceeded the minimum strength conditions specified in MASH; at 92 percent soil compaction, the soil strength exceeded the minimum strength conditions by approximately 30 percent; and at 88 percent soil compaction the resulting strength was significantly less than MASH specifications. The soil conditions corresponding to 92 percent compaction were selected as the baseline for the remainder of the study. Figure 140. Force vs. deflection results for soil strength tests. Figure 141. Energy vs. deflection results for soil strength tests. 0 5 10 15 20 25 30 0 10 20 30 40 Fo rc e ( ki p ) Displacement (in) 13010D - 96% Compaction 144 pcf 13010F - 92% Compaction 138 pcf 13010E - 88% Compaction 132 pcf MASH Minimum 0 100 200 300 400 500 600 0 10 20 30 40 En e rg y (k ip -i n ) Displacement (in) 13010D - 96% Compaction 144 pcf 13010F - 92% Compaction 138 pcf 13010E - 88% Compaction 132 pcf

196 Round Wood Post Tests Tests 13010G, 13010H and 13010I were performed using a round wood posts. Test 13010G involved a 68-inch long post with a low level of deterioration (e.g., Resi Scores SM = 0.86 and SU = 0.97). Tests 13010 H and 13010I, involved new, unused posts 72 inches long. The posts were embedded 40 inches in the soil for all cases. The soil conditions for Test 13010G conformed to the baseline soil conditions with dry density of 138.6 pcf, moisture content of 3.4 percent and soil compacted to 92.3 percent. The soil conditions for Test 13010H, however, exceeded the baseline values with soil density equal 142.4 pcf, 6.2 percent moisture content and 94.8 percent compaction. The soil conditions were not measured for Test 13010I due to problems with soil density gauge; however, the same compaction procedure used in Test 13010G was followed. In Tests 13010G and 13010H, the 2,372-lb pendulum struck the posts at 24.8 inches above ground at an impact speed of 20 mph. For Test 13010I, the impact speed was reduced to 10 mph. The results of these tests are shown in Figure 142 through Figure 144. The posts ruptured in each of the three tests. The peak force at rupture was 9.8 kips, 8.6 kips and 10.7 kips for Tests G, H, and I, respectively, compared to a maximum resistive force of 13.2 kips for the soil (refer to Figure 140). Based on the results of these tests, it appears that the round wood post with nominal diameter of 8 inches does not have sufficient strength to properly rotate through the soil, for this baseline soil strength. Further, it should be noted that these tests were conducted with an embedment depth of 40 inches, whereas the construction drawings in the AASHTO- AGC-ARTBA Barrier Hardware Guide show the standard embedment depth for the G4(2W) guardrail system to be 44 inches.[ AASHTO04] Wood Post Strength Test Based on the results of Tests 13010G, 13010H and 13010I, which involved two new posts and one used (but very sound) post, it was decided that it would not be meaningful to perform the second group of tests. Over 85 percent of the posts tested in Test Series 13009 resulted in peak impact forces that were less than 13.2 kips (e.g., peak resistance of baseline soil), as shown in Figure 120; and those that exceeded this strength had very low deterioration and/or relatively large cross-section diameters. Effects of Post Shape (Round vs. Rectangular) on Load Capacity The bending load capacity of a guardrail post is proportional to its section modulus, which for a circular cross-section post is: 𝑆𝑟𝑜𝑢𝑛𝑑 = 𝜋𝑟3 4 For 6x8 rectangular posts, the section modulus is defined for the strong and weak directions by: 𝑆6𝑥8(𝑠𝑡𝑟𝑜𝑛𝑔) = 𝑏ℎ2 6 = 64𝑖𝑛3 𝑆6𝑥8(𝑤𝑒𝑎𝑘) = ℎ𝑏2 6 = 48𝑖𝑛3

197 Figure 142. Summary sheet for Test 13010G. 0 10 20 30 40 50 60 70 80 90 100 0 1 2 3 4 5 6 7 8 R e si st o gr ap h R e su lt s Depth (in) -10 -5 0 5 10 15 20 0 0.01 0.02 0.03 0.04 0.05 A cc el er at io n ( G 's ) Time (sec) (UNF) (FIL) 0 10 20 30 40 50 60 0 2 4 6 8 10 12 14 16 18 20 0 10 20 30 40 En e rg y (k ip -i n ) Fo rc e ( ki p ) Displacement (in) Force Energy Test Information_______________________ Test Number: 13010G Test Date: 8-Nov-2013 Post Properties________________________ Post Number: 57 Post Type: Round SYP Post Length: 68 inches Post Diameter: 7.2 inches Embedment Depth: 40 inches Moisture Content: 39 percent Ring Density (avg.): 9.2 per inch Resi Score SM: 0.86 Resi Score SU: 0.97 Soil Properties________________________ Dry Density: 138.6 pcf Moisture Content: 3.4 percent Compaction: 92.3 percent Pendulum Properties___________________ Weight: 2,372 lb Impact Speed: 20 mph Impact Height: 24.8 inches Fractured Post 0.050 sec 0.075 sec 0.100 sec 0.025 sec

198 Figure 143. Summary sheet for Test 13010H. -10 -5 0 5 10 15 20 0 0.01 0.02 0.03 0.04 0.05 A cc el er at io n ( G 's ) Time (sec) (UNF) (FIL) 0 10 20 30 40 50 60 0 2 4 6 8 10 12 14 16 18 20 0 10 20 30 40 En er gy ( ki p -i n ) Fo rc e ( ki p ) Displacement (in) Force Energy Test Information_______________________ Test Number: 13010H Test Date: 16-Dec-2013 Post Properties________________________ Post Number: D Post Type: Round SYP Post Length: 72 inches Post Diameter: 7.5 inches Embedment Depth: 40 inches Moisture Content: 35 percent Ring Density (avg.): 6.4 per inch Resi Score SM: Resi Score SU: Soil Properties________________________ Dry Density: 142.4 pcf Moisture Content: 6.2 percent Compaction: 94.8 percent Pendulum Properties___________________ Weight: 2,372 lb Impact Speed: 20 mph Impact Height: 24.8 inches Fractured Post 0.050 sec 0.075 sec 0.100 sec 0.025 sec

199 Figure 144. Summary sheet for Test 13010I. -10 -5 0 5 10 15 20 0 0.01 0.02 0.03 0.04 0.05 A cc el er at io n ( G 's ) Time (sec) (UNF) (FIL) 0 10 20 30 40 50 60 0 2 4 6 8 10 12 14 16 18 20 0 10 20 30 40 En er gy ( ki p -i n ) Fo rc e ( ki p ) Displacement (in) Force Energy Test Information_______________________ Test Number: 13010I Test Date: 18-Dec-2013 Post Properties________________________ Post Number: E Post Type: Round SYP Post Length: 72 inches Post Diameter: 7.4 inches Embedment Depth: 40 inches Moisture Content: 19 percent Ring Density (avg.): 4.1 per inch Resi Score SM: Resi Score SU: Soil Properties________________________ Dry Density: - pcf Moisture Content: - percent Compaction: - percent Pendulum Properties___________________ Weight: 2,372 lb Impact Speed: 10 mph Impact Height: 24.8 inches Fractured Post 0.050 sec 0.075 sec 0.100 sec 0.025 sec

200 Figure 145 shows a plot of section modulus vs. post diameter for the round wood post. The two dashed lines in the plot represent the section modulus for the 6x8 rectangular post in the strong direction (thick dashed line) and the weak direction (thin dashed line). The calculations show that a round post with a diameter of 8.67 inches has the same section modulus (i.e., strength) as the 6x8 rectangular post in the strong direction. Recall that the nominal diameter for the round wood post is 8 inches ± 1 inch; thus, most of the round post sizes have less strength than the 6x8 post and in some cases half the strength. In the weak direction, on the other hand, the strength of the round post with 7.9-inch diameter is equal to that of the 6x8 post. When guardrail posts are struck on their side (e.g., wheel snag on the post) it is desired that the post readily breakaway in order to minimize impact forces. It is also important, however, for the posts have sufficient strength to sustain the lateral loading of the guardrail during impact to minimize guardrail deflections. Since the bending strength of a round post is equal in all directions, it is not possible to obtain optimum strength for the post in both the lateral and longitudinal directions. Finite Element Analysis Finite element models of wood guardrail posts with various levels of deterioration damage were developed. These models were then used in full-scale crash simulations of the G4(2W) guardrail under Report 350 Test 3-11 impact conditions to quantify the effects of post degradation on the performance of the guardrail system. The development and validation of the finite element model of the G4(2W) guardrail was presented in Chapter 7. The various components of the validated G4(2W) guardrail were modeled according to their baseline conditions, including the wood post model. For example, the material properties for the baseline guardrail post model were determined through the process of trial and error by comparing the dynamic impact response of the post model to the results of full- scale pendulum impact tests on new guardrail posts (i.e., Tests 13009K and 13009L). This same approach was adopted here for calibrating the material properties for the posts with various levels of deterioration damage. Calibration of FE Models for Deteriorated Posts Damage Level 1 (DL1) The impact conditions for Tests 13009 Series 2 were simulated using the finite element model shown in Figure 146. The guardrail post was modeled with a diameter of 8 inches. Two sets of material properties were developed for simulating damage level 1. One set was developed based on comparison to Test 13009H1 which resulted in a relatively low peak force with ductile post-peak failure response. Another set of material properties was developed based on comparison to Test 13009L1, which resulted in a relatively high peak force and brittle post-peak failure. The specific property values for these models are shown in Table 48 which correspond to material model *MAT_WOOD in LS-DYNA.

201 Figure 145. Section modulus for round posts with radius ranging from 7 to 8 inches compared to the 6x8 rectangular post. The results of the model are compared to the full-scale impact tests in Figure 147 through Figure 150. Figures 147 and 148 show the force vs. deflection and energy vs. deflection results, respectively, for the FE model compared to Test 13009H1. The peak impact force from the analysis was 13 kips compared to 12.2 kips in the test. The total energy absorbed in the analysis at 13 inches displacement was 57 kip-inches compared to 56 kip-inches in the test. Figure 149 and Figure 150 show the force vs. deflection and energy vs. deflection response for the FE model compared to Test 13009L1. In this case the FE model resulted in a peak force of 17.3 kips compared to 13.6 kips in the test. The total energy absorbed in the analysis at 13 inches displacement was 46.5 kip-inches compared to 49.7 kip-inches in the test. Figure 151 and Figure 152 show sequential views comparing analysis results to dynamic impact tests 13009H1 and 13009L1, respectively. An important point to consider regarding the differences between the tests and simulations is that the analyses and the tests have essentially the same number of peaks leading up to initiation of rupture, but the distance between peaks is considerably different. The reason for the differences is not well understood. From a review of the test video, the impact speed was confirmed to be 10 mph, which is the same as the impact speed that was simulated in the models. The most logical explanation is that the boundary conditions for the tests were effectively less “rigid” than those of the model. Thus, the test specimens were allowed greater movement upon impact at, and below, groundline, which consequently resulted in a greater distance between the initial inertial spike (i.e., first peak) and the start of the actual loading on the post (i.e., second peak). For comparison of the analysis results with the tests, the test data was shifted such that the initial loading of the second peak was coincident with that of the analysis. 0 10 20 30 40 50 60 70 80 7.0 7.5 8.0 8.5 9.0 Se ct io n M o d u lu s (i n 3 ) Post Diameter (in) Round Post 6x8 Strong Dir. 6x8 Weak Dir. 7.9 8.7

202 Table 48. Material properties for wood post model corresponding to damage levels 1 through 3. Variable Description DL1(a) DL1(b) DL2 DL3(a) DL3(b) General lower force more ductile higher force more brittle lower force more ductile more ductile more brittle RO Density (Mg/mm3) 6.73E-10 6.73E-10 6.73E-10 6.73E-10 6.73E-10 NPLOT Parallel damage written to D3PLOT 1 1 1 1 1 ITERS Number of plasticity iterations 1 1 1 1 1 IRATE Rate effects (0=off; 1=on) 1 1 1 1 1 GHARD Perfect plasticity override (0=perfect plasticity) 0.05 0.05 0.05 0.05 0.05 IFAIL Erosion perpendicular to grain (0=No; 1=Yes) 1 1 1 1 1 IVOL Erode on negative volume (0=No; 1=Yes) 0 0 0 0 0 Stiffness EL Parallel Normal Modulus (MPa) 11352 9082 567.6 4540.8 4540.8 ET Perpendicular Normal Modulus (MPa) 246.8 197.4 123.4 98.7 98.7 GLT Parallel Shear Modulus (MPa) 715.2 572.2 357.6 286.1 286.1 GTR Perpendicular Shear Modulus (MPa) 87.5 70 43.8 35 35 PR Parallel Major Poisson's Ration 0.157 0.157 0.157 0.157 0.157 Strength XT Parallel Tensile Strength (MPa) 35.8 35.8 30.7 27.3 25.5 XC Parallel Compressive Strength (MPa) 12.7 13.7 8.88 7.83 7.4 YT Perpendicular Tensile Strength (MPa) 0.86 0.86 0.74 0.66 0.61 YC Perpendicular Compressive Strength (MPa) 2.5 2.7 1.7 1.5 1.4 SXY Parallel Shear Strength (MPa) 3.8 3.8 3.3 2.9 2.7 SYZ Perpendicular Shear Strength (MPa) 5.3 5.3 4.6 4.1 3.8 Damage GF1∥ Parallel Fracture Energy in Tension (MPa-mm) 35.8 35.8 15.4 13.7 12.8 GF2∥ Parallel Fracture Energy in Shear (MPa-mm) 74.1 74.1 31.8 28.2 26.5 BFIT Parallel Softening Parameter 30 30 30 30 30 DMAX∥ Parallel Maximum Damage 0.9999 0.9999 0.9999 0.9999 0.9999 GF1⊥ Perpendicular Fracture Energy in Tension (MPa-mm) 0.8 0.8 0.4 0.4 0.4 GF2⊥ Perpendicular Fracture Energy in Compression (MPa-mm) 1.6 1.6 0.83 0.83 0.83 DFIT Perpendicular Softening Parameter 30 30 30 30 30 DMAX⊥ Perpendicular Maximum Damage 0.99 0.99 0.99 0.99 0.99 Rate Effects FLPAR Parallel Fluidity Parameter Tension/Shear 3.96E-06 3.96E-06 3.39E-06 3.02E-06 2.83E-06 FLPARC Parallel Fluidity Parameter Compression 5.65E-06 6.13E-06 3.96E-06 3.49E-06 3.30E-06 POWPAR Parallel Power 0.107 0.107 0.107 0.107 0.107 FLPER Perpendicular Fluidity Parameter Tension/Shear 8.29E-05 8.29E-05 7.10E-05 6.31E-05 5.92E-05 FLPERC Perpendicular Fluidity Parameter Compression 1.18E-04 1.04E-04 8.29E-05 7.30E-05 6.91E-05 POWPER Perpendicular Power 0.104 0.104 0.104 0.104 0.104 Hardening NPAR Parallel Hardening Initiation 0.50 0.50 0.50 0.50 0.50 CPAR Parallel Hareding Rate (/s) 111.1 500.0 226.8 292.2 326.5 NPER Perpendicular Hardening Initiation 0.40 0.40 0.40 0.40 0.40 CPER Perpendicular Hardening Rate (/s) 277.8 400.0 566.9 730.5 816.3 Units: Mg, mm, sec, N, MPa

203 Figure 146. Finite element model used for calibrating material property values for various deterioration levels of wood posts. Figure 147. Force vs. deflection for DL1(a) wood post model corresponding to Test 13009H1 (ductile response). 0 2 4 6 8 10 12 14 16 0 5 10 15 Fo rc e ( lk ip ) Displacement (in) Damage Level 1a H1 (8.0 in) FEA Q42-60 GF*2

204 Figure 148. Energy vs. deflection for DL1(a) wood post model corresponding to Test 13009H1 (ductile response). Figure 149. Force vs. deflection for DL1(b) wood post model corresponding to Test 13009L1 (brittle response). 0 10 20 30 40 50 60 0 5 10 15 En e rg y (l ki p -i n ) Displacement (in) Damage Level 1a H1 (8.0 in) FEA Q42-60 GF*2 0 2 4 6 8 10 12 14 16 18 20 0 5 10 15 Fo rc e ( lk ip ) Displacement (in) Damage Level 1b L1 (8.0 in) FEA Q42-65 GF*2

205 Figure 150. Energy vs. deflection for DL1(b) wood post model corresponding to Test 13009L1 (brittle response). 0 10 20 30 40 50 60 0 5 10 15 En e rg y (l ki p -i n ) Displacement (in) Damage Level 1b L1 (8.0 in) FEA Q42-65 GF*2

206 Figure 151. Sequential views of Test 13009H1 and FE analysis DL1(a). 13009H1 0.03 sec 0.04 sec 0.05 sec 0.02 sec FEA DL1(a) 0.03 sec 0.04 sec 0.05 sec 0.02 sec

207 Figure 152. Sequential views for Test 13009L1 and FE analysis DL1(b). 13009L1 0.03sec 0.04 sec 0.05 sec 0.02 sec FEA DL1(b) 0.03sec 0.04 sec 0.05 sec 0.02 sec

208 Damage Level 2 (DL2) A single set of material properties were developed for simulating damage level 2. These properties, shown in Table 48 under heading DL2, correspond to predefined values for *MAT_WOOD_PINE with QT=0.36 and QC=0.42, with the elastic properties scaled by 50 percent of the default undamaged wood values. The impact response for this model was very similar to the results from Tests 13009Z1 and 13009H2. Figure 153 and Figure 154 show the force vs. deflection and energy vs. deflection results for the FE model compared to the pendulum tests. The peak impact force from the analysis was 8.8 kips and the total energy absorbed in the analysis at 15 inches displacement was 27.3 kip-inches. Thus, response falls within the criteria defined for damage level 2. Figure 153. Force vs. deflection for DL1(a) wood post model corresponding to Test 13009H1 (ductile response). 0 1 2 3 4 5 6 7 8 9 10 0 5 10 15 20 Fo rc e ( lk ip ) Displacement (in) Damage Level 2 Z (8.1 in) H2 (8.1 in) FEA DL2

209 Figure 154. Energy vs. deflection for DL1(a) wood post model corresponding to Test 13009H1 (ductile response). Damage Level 3 (DL3) Two sets of material properties were developed for simulating damage level 3. The properties shown in Table 48 under heading DL3(a), correspond to predefined values for *MAT_WOOD_PINE with QT=0.32 and QC=0.37, with the elastic properties scaled by 40 percent of the default undamaged wood values. The impact response for this model was very similar to the results from Test 13009S1. The properties shown in Table 48 under heading DL3(b), correspond to predefined values for *MAT_WOOD_PINE with QT=0.30 and QC=0.35, with the elastic properties scaled by 40 percent of the default undamaged wood values. The impact response for this model was very similar to the results from Test 13009N1. Figure 155 and Figure 156 show the force vs. deflection results for model DL3(a) and DL3(b), respectively, compared to the pendulum tests; and Figure 157 and Figure 158 show the energy vs. deflection results for model DL3(a) and DL3(b), respectively, compared to the pendulum tests. The peak impact force from the analysis was 8.4 kips for both models, and the total energy absorbed at 15 inches displacement was 19.4 kip-inches for model DL3(a) and 17.8 kip-inches for model DL3(b). Thus, the response of both models falls within the criteria defined for damage level 3. 0 5 10 15 20 25 30 0 5 10 15 20 En e rg y (l ki p -i n ) Displacement (in) Damage Level 2 Z1 (8.1 in) H2 (8.1 in) FEA Q42-60 GF*2

210 Figure 155. Force vs. deflection for DL3(a) wood post model and Tests 13009S1 and 13009N1 (more ductile response). Figure 156. Force vs. deflection for DL3(b) wood post model and Tests 13009S1 and 13009N1 (more brittle response). 0 1 2 3 4 5 6 7 8 9 10 0 5 10 15 20 Fo rc e ( lk ip ) Displacement (in) Damage Level 3 S1 (8.1 in) N1 (8.1 in) FEA DL3 0 1 2 3 4 5 6 7 8 9 10 0 5 10 15 20 Fo rc e ( lk ip ) Displacement (in) Damage Level 3 S1 (8.0 in) N1 (8.0 in) FEA DL3

211 Figure 157. Energy vs. deflection for DL3(a) wood post model and Tests 13009S1 and 13009N1 (more ductile response). Figure 158. Energy vs. deflection for DL3(b) wood post model and Tests 13009S1 and 13009N1 (more brittle response). 0 5 10 15 20 25 0 5 10 15 20 En e rg y (l ki p -i n ) Displacement (in) Damage Level 3 S1 (8.1 in) N1 (8.1 in) FEA DL3 0 5 10 15 20 25 0 5 10 15 20 En e rg y (l ki p -i n ) Displacement (in) Damage Level 3 S1 (8.0 in) N1 (8.0 in) FEA DL3

212 Evaluate Effects of Post Deterioration on Guardrail Performance The effects of post strength degradation on the crash performance of the G4(2W) guardrail was evaluated using FEA. Two damage scenarios were investigated. The first involved evaluation of the G4(2W) with uniform deterioration of the guardrail posts throughout the impact region. This scenario is analogous to an aged guardrail system with deteriorated posts, but otherwise the guardrail is undamaged. The second scenario involved evaluation of the G4(2W) in which a number of new posts were installed downstream and adjacent to a line of deteriorated posts. This scenario is representative of a local repair on an aged guardrail system, where a small number of the posts in a line of deteriorated posts have been replaced with new posts. The analysis matrix for the study is shown in Table 49. The impact conditions were set to those of full-scale crash test 471470-26 and involved the 4,568-lb C2500D pickup model impacting the guardrail at 62.6 mph (100.8 km/hr) at an angle of 24.3 degrees.[Mak99] Due to time and budget constraints, the critical impact point (CIP) for each individual guardrail damage case was not determined. The impact point for all analysis cases was set at 22 inches upstream of Post 14, which corresponded to the CIP for the baseline G4(2W) guardrail in Test 471470- 26.[Mak99] The analyses were conducted for 0.6 seconds of the impact event. Table 49. Analysis matrix for deteriorated wood post study. Uniform Post Deterioration in Impact Region The analysis model used for evaluating the effects of uniform deterioration of the guardrail posts is shown in Figure 159. The posts located within the impact region were modeled using MAT143 with material properties defined according to Table 48; while the posts located outside the impact region were modeled using MAT13, which was a much simpler, less computationally demanding material model. MAT13 was not calibrated for the various levels of post deterioration. Instead, the material parameters used for MAT13 were adopted from the earlier work by Plaxico, et.al.[Plaxico98] In effect, the posts outside the impact zone should be considered undamaged, or new. The boundary conditions for the ends of the rail were modeled using non-linear springs with force-deflection response corresponding to a standard two-foundation-tube-and-strut type anchor, which was the type of anchor used in the baseline full-scale crash test.[Mak99]. The stiffness of the anchor for these analyses were notably less than that of the validation model in which the stiffness properties of the boundary springs were defined based on previous work presented in [Plaxico03]. As a result, the baseline model (i.e., model with Damage Level 0 posts) showed slightly higher deflections than the validation model. Both cases are included in the results below for relative comparisons. (Baseline) DL0 DL1 DL2 DL3 Uniform Post Deterioration in Impact Region x x x x Derteriorated Posts Upstream of Undamged Posts x x x x Damage Level for Guardrail Posts Damage Case Scenario

213 Figure 159. Analysis setup for evaluation of uniform deterioration of posts in the impact region. Sequential views of the FE analysis results for each case are provided in Appendix G. Table 50 provides a summary of barrier damage from the analyses related to rail deflections, anchor movement and splice damage. This information is also presented graphically in Figure 160 and Figure 161. The maximum rail deflection increased significantly for each damage level. The deflections for DL2 and DL3 cases were more than 75 percent higher than the baseline case. Table 50. Summary of barrier damage evaluation from uniform post deterioration analyses. For strong-post w-beam guardrails with rail splices located at the guardrail posts, the critical impact point is determined based on achieving maximum loading on a w-beam splice connection. This generally occurs when the maximum rail deflection occurs just upstream of the splice. Regarding the “location of maximum deflection” in Table 50, a negative number indicates that the maximum deflection occurred upstream of the splice at Post 16, while a positive number indicates that maximum deflection occurred downstream of the splice. The maximum rail deflection for the baseline DL0 case occurred at 14.8 inches upstream of the w-beam splice at Post 16 and can therefore be considered a critical impact case. The location of maximum deflection for the damaged post cases, on the other hand, all occurred downstream of the splice Deteriorated Posts (MAT143) Undamaged Posts (MAT13) Undamaged Posts (MAT13) Validation DL0 DL0 DL1 DL2 DL3 Maximum Rail Deflection (in) 27.3 32.0 45.1 56.1 58.9 Location of Max Defl. (in) (Relative to Post 16) -30.5 -14.8 23.8 64.4 75.0 Rail Deflection at Post 13 (in) 1.2 1.8 4.7 5.6 6.5 Rail Deflection at Post 14 (in) 11.3 13.1 20.4 22.8 24.1 Rail Deflection at Post 15 (in) 24.8 27.8 33.7 38.1 40.5 Rail Deflection at Post 16 (in) 25.4 31.1 44.3 51.4 53.9 Rail Deflection at Post 17 (in) 9.1 17.5 42.9 56.1 58.9 Rail Deflection at Post 18 (in) 0.3 1.2 32.3 54.2 56.2 Rail Deflection at Post 19 (in) 0.0 0.0 7.3 42.2 50.9 Upstream Anchor Deflection (in) 0.5 1.4 1.4 1.4 1.4 Downstream Anchor Deflection (in) 0.2 0.9 1.3 1.7 1.9 Maximum Strain in splice 0.89 0.84 1.05 1.13 1.10 Event Analysis

214 connection; particularly for cases DL2 and DL3. Thus, the results for the deteriorated post cases would likely have been more severe had critical impact conditions been used. Figure 161 shows the longitudinal displacement of the upstream and downstream ends of the w-beam at the anchor locations. For the validation case, the maximum deflection was only 0.5 inches compared to 1.4 inches computed for the baseline analysis case due to different anchor stiffness. For the deteriorated post cases, the loading on the upstream anchor was the same as the baseline analysis. The longitudinal rail deflections at the downstream anchor, however, increased significantly with each level of post deterioration. In general, higher lateral deflections in the impact region are associated with higher anchor forces. The fact that only the downstream anchor resulted in increased anchor forces is not clearly understood, but it was in part attributed to the fact that the location of maximum lateral deflection occurred father downstream for each increase in post deterioration level. Figure 160. Summary of barrier damage evaluation from analysis of uniform post deterioration. -40.0 -20.0 0.0 20.0 40.0 60.0 80.0 Barrier Damage: Uniform Posts Validation DL0 Analysis DL0 Analysis DL1 Analysis DL2 Analysis DL3

215 Figure 161. Summary of anchor displacement at rail height from analysis of uniform post deterioration. A summary of occupant risk measures computed from the acceleration and angular rate time-histories at the vehicle’s center of gravity is provided in Table 51. This data is also presented graphically in Figures 163 through 165. The difference in results between the validation case and the baseline case was considered minimal. The results of the analyses involving deteriorated posts indicated that as post deterioration increases (i.e., post strength decreases) the vehicle decelerations decreased, thereby reducing the occupant risk metrics. This seems logical since the system is effectively becoming less stiff, similar to weak-post w-beam systems. The potential for rail rupture was assessed by comparing the plastic strains in the w-beam rail with those from the baseline case. Figure 162 shows the effective plastic strain contours for the w-beam splice connection at Post 16 from one of the analysis cases. As illustrated in the figure, the highest strains occurred at the splice-bolt holes while the strains in all other regions of the w-beam splice were relatively benign (note that the splice-bolt nuts were removed from view in Figure 162 in order to more clearly show the strains in the material around the bolt holes). 0.0 0.5 1.0 1.5 2.0 2.5 DL0 DL0 DL1 DL2 DL3 Validation Analysis A nc ho r D ef le ct io n (in ) Anchor Deflection: Uniform Post Deterioration Upstream Anchor Deflection (in) Downstream Anchor Deflection (in)

216 Figure 162. Effective plastic strain contour plot for w-beam in splice connection at Post 16. A summary of the maximum effective plastic strains around the splice-bolt holes in the w-beam is shown in Figure 166. The results indicate that the plastic strain values were relatively high even for the baseline case with a magnitude of 0.84, while for analysis Case DL1, the plastic strain values were 25 percent higher with a magnitude of 1.05. It is assumed that the baseline G4(2W) guardrail case is near its performance capacity under these impact conditions, thus as the plastic strains increase beyond those of the baseline case, the potential for rupture increases accordingly.

217 Table 51. Summary of occupant risk measures from evaluation of uniform post deterioration analyses. Test 471470-26 DL0 (Validation) DL0 (Baseline) DL1 DL2 DL3 Occupant Impact Velocity x-direction 4.6 5.3 5.2 4.4 3.8 3.3 (m/s) y-direction 5.8 5.8 5.3 4.8 4.3 4.3 at time (0.1437 sec) (0.1442 sec) (0.1519 sec) (0.1618 sec) (0.1727 sec) (0.1782 sec) 6.9 7.4 7 6.1 5.6 5.4 (0.1404 sec) 0.1398 0.1471 (0.1559 sec) (0.1667 sec) (0.1723 sec) Ridedown Acceleration 11.5 10.2 10.3 7.9 7.0 5.8 (g's) (02025 - 0.2125 sec) (0.1791 - 0.1891 sec) (0.1519 - 0.1619 sec) (0.1968 - 0.2068 sec) (0.3578 - 0.3678 sec) (0.27148 - 0.2814 sec) 11.2 11.1 10.7 8.0 6.9 7.3 (0.2381 - 0.2481 sec) (0.2152 - 0.2252 sec) (0.2198 - 0.2298 sec) (0.2143 - 0.2243 sec) (0.2825 - 0.2925 sec) (0.5641 - 0.5741 sec) 11.7 13.6 13.7 8.5 8.1 8.7 (0.2025 - 0.2125 sec) (0.2148 - 0.2248 sec) (0.2003 - 0.2103 sec) (0.2047 - 0.2147 sec) (0.3571 - 0.3671 sec) (0.2695 - 0.2795 sec) 1.01 0.99 0.93 0.66 0.63 0.65 (0.2176 - 0.2676 sec) (0.1172 - 0.1672 sec) (0.1219 - 0.1719 sec) (0.2062 - 0.2562 sec) (0.2822 - 0.3322 sec) (0.2651 - 0.3151 sec) Max 50-ms moving avg. acc. 6.1 6.2 7.6 4.6 3.8 3.2 (g's) (0.1382 - 0.1882 sec) (0.1390 - 0.1890 sec) (0.1216 - 0.1716 sec) (0.1166 - 0.1666 sec) (0.3448 - 0.3948 sec) (0.1808 - 0.2308 sec) 6.8 7.7 6.5 5.4 5.5 5.4 (0.0945 - 0.1445 sec) (0.1179 - 0.1679 sec) (0.1976 - 0.2476 sec) (0.2071 - 0.2571 sec) (0.2825 - 0.3325 sec) (0.2661 - 0.3161 sec) 9.0 2.4 2.4 1.9 1.5 1.9 (0.2174 - 0.2674 sec) (0.4155 - 0.4655 sec) (0.3344 - 0.3844 sec) (0.3900 - 0.4400 sec) (0.3383 - 0.3883 sec) (0.2985 - 0.3485 sec) PHD Occupant Risk Factors THIV (m/s) x-direction y-direction (g's) x-direction y-direction z-direction ASI

218 Figure 163. Summary of occupant impact velocity evaluation of uniform post deterioration. Figure 164. Summary of maximum occupant ridedown acceleration evaluation of uniform post deterioration. 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 O IV ( m /s ) Occupant Impact Velocity x-direction y-direction 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 O R A ( g) Occupant Ridedown Acceleration x-direction y-direction

219 Figure 165. Summary of 50-ms running average acceleration evaluation of uniform post deterioration. Figure 166. Summary of maximum effective plastic strains occurring at the splice-bolt locations at Post 16. For analysis case DL2 and DL3 the plastic strains were slightly higher than the DL1 case. It is possible, although not confirmed, that the splice damage for cases DL2 and DL3 may be higher if evaluated at their critical impact points. 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 5 0 -m s A ve ra ge A cc . ( g) 50-ms Avg. Acceleration x-direction y-direction 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 DL0 DL1 DL2 DL3 Analysis Splice Strains: Uniform Posts

220 Deteriorated Posts Upstream of Undamaged Posts The analysis model used for evaluating the effects of deteriorated posts upstream of undamaged posts is shown in Figure 167. Figure 167. Analysis setup for evaluation of mixed deterioration of posts in the impact region. Sequential views of the FE analysis results for each case are provided in Appendix H. Table 52 provides a summary of barrier damage from the analyses related to rail deflections, anchor movement and splice damage. This information is also presented graphically in Figure 168 and Figure 169. The maximum rail deflection increased only slightly for the DL1 case, compared with the baseline; while the maximum rail deflection for cases DL2 and DL3 were 46 percent and 56 percent higher, respectively, than the baseline analysis case. The location of maximum rail deflection for analysis Case DL1 was at 21.5 inches upstream of the splice connection at Post 16; thus the impact conditions for this analysis were representative of the critical impact conditions. The location of maximum rail deflection for cases DL2 and DL3, on the other hand, was at Post 16; thus, the critical impact point for these cases was probably not achieved. It is assumed that the results for Cases DL2 and DL3 would likely have been more severe had critical impact conditions been used. Based on the results from the evaluation of uniform deterioration of guardrail posts, the CIP for Case DL2 was estimated to be at approximately 20.8 feet upstream of the splice connection at Post 16, and the CIP for DL3 was estimated to be at approximately 21.7 feet upstream of the splice connection at Post 16. These impact conditions should result in maximum rail deflection occurring just upstream of the splice connection located at the first undamaged post at Post 16. Figure 169 shows the longitudinal displacement of the upstream and downstream ends of the w-beam at the anchor location. For Case DL1 the loading on both the upstream and downstream anchors were essentially the same as those of the baseline analysis case. As the deterioration levels increased, the loading on the upstream anchor increased slightly, although deflections were not that significant (e.g., maximum deflections of 1.8 to 2 inches). The loading on the downstream anchor was essentially the same in all cases. Deteriorated Posts (MAT143) Undamaged Posts (MAT13) Undamaged Posts (MAT143) Undamaged Posts (MAT13)

221 Table 52. Summary of barrier damage evaluation from mixed post deterioration analyses. Figure 168. Summary of barrier damage evaluation from mixed post deterioration analyses. Validation DL0 DL0 DL1-DL0 DL2-DL0 DL3-DL0 Maximum Rail Deflection (in) 27.3 32.0 35.5 46.6 49.8 Location of Max Defl. (in) (Relative to Post 16) -30.5 -14.8 -21.5 0.0 0.0 Rail Deflection at Post 13 (in) 1.2 1.8 3.1 23.9 31.1 Rail Deflection at Post 14 (in) 11.3 13.1 14.2 33.2 40.3 Rail Deflection at Post 15 (in) 24.8 27.8 29.6 41.1 46.0 Rail Deflection at Post 16 (in) 25.4 31.1 34.9 46.6 49.8 Rail Deflection at Post 17 (in) 9.1 17.5 25.0 39.9 44.4 Rail Deflection at Post 18 (in) 0.3 1.2 4.6 18.9 24.6 Rail Deflection at Post 19 (in) 0.0 0.0 0.0 1.4 3.1 Upstream Anchor Deflection (in) 0.5 1.4 1.4 1.8 2.0 Downstream Anchor Deflection (in) 0.2 0.9 1.0 1.0 1.1 Maximum Strain in splice 0.89 0.84 1.00 1.16 1.27 Event Analysis -40.0 -20.0 0.0 20.0 40.0 60.0 80.0 Barrier Damage: Mixed Posts Validation DL0 Analysis DL0 Analysis DL1-DL0 Analysis DL2-DL0 Analysis DL3-DL0

222 Figure 169. Summary of anchor displacement at rail height from mixed post deterioration analyses. A summary of occupant risk measures computed from the acceleration and angular rate time-histories at the vehicle’s center of gravity is provided in Table 53. This data is also presented graphically in Figures 170 through 172. The results indicate that the vehicle decelerations were very similar for all cases, with a slight trend toward decreasing values as post deterioration increased. These results seem counter intuitive and should be reassessed using a more appropriate impact point for the analyses. A summary of the maximum effective plastic strains around the splice-bolt holes in the w-beam for each analysis case is shown in Figure 173. The results indicated that the potential for splice rupture increased as post deterioration increased. For example, the plastic strains at the splice-bolt holes reached magnitudes of 1.0, 1.2 and 1.3 for cases DL1, DL2 and DL3, respectively. It is assumed that the results for cases DL1 and DL2 actually under-predict the maximum strain values, since the critical impact point for these two cases was not evaluated. 0.0 0.5 1.0 1.5 2.0 2.5 DL0 DL0 DL1-DL0 DL2-DL0 DL3-DL0 Validation Analysis An ch or D ef le ct io n (in ) Anchor Deflection: Mixed Posts Upstream Anchor Deflection (in) Downstream Anchor Deflection (in)

223 Table 53. Summary of occupant risk measures from mixed post deterioration analyses. Test 471470-26 DL0 (Validation) DL0 (Baseline) DL1 - DL0 DL2 - DL0 DL3 - DL0 Occupant Impact Velocity x-direction 4.6 5.3 5.2 4.3 5.1 5.1 (m/s) y-direction 5.8 5.8 5.3 5.1 5.0 4.9 at time 0.1437 (0.1442 sec) (0.1519 sec) (0.1535 sec) (0.1683 sec) (0.1701 sec) 6.9 7.4 7 6.4 6.7 6.7 (0.1404 sec) 0.1398 0.1471 (0.1484 sec) (0.1629 sec) (0.1646 sec) Ridedown Acceleration 11.5 10.2 10.3 11.2 11.0 9.1 (g's) (02025 - 0.2125 sec) (0.1791 - 0.1891 sec) (0.1519 - 0.1619 sec) (0.1546 - 0.1646 sec) (0.1962 - 0.2062 sec) (0.1988 - 0.2088 sec) 11.2 11.1 10.7 10.2 10.5 7.2 (0.2381 - 0.2481 sec) (0.2152 - 0.2252 sec) (0.2198 - 0.2298 sec) (0.2124 - 0.2224 sec) (0.2142 - 0.2242 sec) (0.2836 - 0.2936 sec) 11.7 13.6 13.7 13.6 11.2 10.0 (0.2025 - 0.2125 sec) (0.2148 - 0.2248 sec) (0.2003 - 0.2103 sec) (0.1547 - 0.1647 sec) (0.1964 - 0.2062 sec) (0.1996 - 0.2096 sec) 1.01 0.99 0.93 0.89 0.74 0.72 (0.2176 - 0.2676 sec) (0.1172 - 0.1672 sec) (0.1219 - 0.1719 sec) (0.1936 - 0.2436 sec) (0.1142 - 0.1642 sec) (0.1145 - 0.1645 sec) Max 50-ms moving avg. acc. 6.1 6.2 7.6 6.1 5.9 5.8 (g's) (0.1382 - 0.1882 sec) (0.1390 - 0.1890 sec) (0.1216 - 0.1716 sec) (0.1174 - 0.1674 sec) (0.1583 - 0.2083 sec) (0.1939 - 0.2439 sec) 6.8 7.7 6.5 7.1 5.6 5.5 (0.0945 - 0.1445 sec) (0.1179 - 0.1679 sec) (0.1976 - 0.2476 sec) (0.1919 - 0.2419 sec) (0.2037 - 0.2537 sec) (0.2818 - 0.3318 sec) 9.0 2.4 2.4 2.7 2.3 3.0 (0.2174 - 0.2674 sec) (0.4155 - 0.4655 sec) (0.3344 - 0.3844 sec) (0.3158 - 0.3658 sec) (0.3944 - 0.4444 sec) (0.4245 - 0.4745 sec) (g's) ASI x-direction y-direction z-direction PHD Occupant Risk Factors THIV (m/s) x-direction y-direction

224 Figure 170. Summary of occupant impact velocity evaluation of uniform post deterioration. Figure 171. Summary of maximum occupant ridedown acceleration evaluation of uniform post deterioration. 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 O IV ( m /s ) Occupant Impact Velocity x-direction y-direction 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 O R A ( g) Occupant Ridedown Acceleration x-direction y-direction

225 Figure 172. Summary of 50-ms running average acceleration evaluation of uniform post deterioration. Figure 173. Summary of maximum effective plastic strains occurring at the splice-bolt locations at Post 16. 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 5 0 -m s A ve ra ge A cc . ( g) 50-ms Avg. Acceleration x-direction y-direction 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 DL0 DL1 DL2 DL3 Analysis Splice Strains: Mixed Posts

226 Summary and Discussion The purpose of this study task was to quantify the effects of various levels of wood post deterioration on the crash performance of the G4(2W) strong-post guardrail system. The first phase involved (1) procuring guardrail post specimens with deterioration levels ranging from severe to essentially undamaged, (2) developing a procedure for quantifying the degree of deterioration, and (3) correlating the degree of deterioration to the dynamic properties of the posts. The Ohio DOT provided 140 wooden guardrail posts for use in this study. The posts were extracted from damaged guardrail installations and represented a wide range of wood deterioration. A resistograph device was used to quantify the degree of deterioration of each post by drilling a 1/16th inch diameter drill bit through the full diameter of each post at groundline and recording the torque resistance on the drilling needle as a function of drilling depth. This information was then processed to determine a deterioration score that represented the effective degradation of post strength. The deterioration score was developed assuming that the resistograph data (i.e., torque amplitude on the drill bit) was linearly proportional to the local fiber strength (e.g., modulus) of the wood at each data point measured through the cross-section of the post. Accordingly, the resistograph data points were then processed to compute a pseudo moment and energy capacity value based on the effects of the measured strength and location within the cross-section with regard to the bending resistance and strain energy capacity of the post. Pendulum tests were conducted to measure the dynamic impact response of the posts. Two series of tests were performed. The first series involved a 2,372-lb rigid pendulum impacting the posts at an impact speed of 20 mph at a height of 21.5 inches above ground. A review of the test results indicated that the inertial response of the posts may have significantly influenced the pendulum-mounted accelerometer data. The 20 mph impact speed resulted in much more energy than was required to break the post so the excess energy resulted in extraneous signal ringing. Thus, a second series of tests was conducted in which the target impact speed was reduced to 10 mph. A total of 22 tests were conducted for the first series at 20 mph and, a total of 39 tests were conducted for the second series at 10 mph. The test data from the second series of tests was found to correlate reasonably well with the resistograph scores. Based on a least-squares regression analysis of the data it was determined that the peak force, peak moment and energy at rupture initiation all increase as a linear function of the resistograph scores. There was some scatter in the data which was expected to be due to the many variables that affect wood strength. The effects of moisture, however, were minimized in the tests by soaking all the posts to saturation levels prior to testing. Other possible causes for error may have been the result of faulty resistograph measurements. The resistograph measurements were made by drilling through the full diameter of the posts at the groundline at the front of the post. There were some cases in which the resistance did not fall back to zero when the drilling needle passed through the back-side of the post. This indicated that the needle likely encountered a “check” or a knot at some point during the test that turned the needle from its straight path and affected subsequent results. This was somewhat corrected in the data by estimating the most logical location for the start of the divergence and assuming that the error was increasing linearly for the remainder of the test. To minimize the effects of this drift phenomenon, it is recommended that the resistograph be used to drill only half way through the diameter on each side of the post. Due

227 to equipment cost and complexity of this method it may not be feasible for use in routine maintenance assessments for quantifying the degree of post degradation; thus future work should include development of more practical procedures for quantifying post deterioration. Pendulum impact tests were also performed to evaluate the effects of various levels of post deterioration on the impact response of the post-soil system. The objectives for these tests were to determine the critical level of deterioration in which a guardrail post ruptures rather than rotates through the soil, and to gather data for validation/calibration of the finite element models. The soil was compacted to 92 percent with a moisture content of approximately 3.4 percent resulting in a dry density of 138 pcf. These soil conditions resulted in a stiffness response that exceeded the minimum strength requirements specified in MASH by approximately 30 percent. The results of the tests showed that the round wood post with nominal diameter of 8 inches does not have sufficient strength to properly rotate through the soil for these soil-strength conditions with post embedment depth of 40 inches or greater. Recall, that the embedment depth for the posts in full-scale crash Test 471470-26 was 36 inches.[Mak99a] The 6x8 inch wood posts used in that test were able to properly rotate through the soil without rupturing. The current standard embedment depth for the G4(2W) guardrail system is 44 inches. That version of the system, however, has not been tested under Report 350 conditions; and when it was tested under MASH conditions, it failed.[Bullard10] Finite element models of round wood posts with various levels of deterioration damage were then developed and the constitutive behavior was calibrated based on the results of the test data from the pendulum impact study. These constitutive material models were incorporated into the validated G4(2W) guardrail model and the system was evaluated under NCHRP Report 350 Test 3-11 impact conditions to quantify the effects of post degradation on the performance of the guardrail. Two damage scenarios were investigated. The first involved evaluation of the G4(2W) with uniform deterioration of the guardrail posts throughout the impact region. This scenario would be analogous to an aged guardrail system in which the posts are deteriorated but the guardrail is otherwise undamaged. The second scenario involved evaluation of the G4(2W) in which a number of new posts were installed adjacent to a line of deteriorated posts. This scenario is representative of a local repair on an aged guardrail system where a small number of the posts in an aged guardrail system have been replaced with new posts. Regarding the first scenario, the analyses indicated that the lateral deflection of the rail increased significantly as post deterioration increased. As lateral rail deflection increased, the tension in the rail also increased and, consequently, resulted in higher loads on the downstream end-anchor. In this scenario, there were no indications that pocketing would be an issue. That is, as post deterioration levels increased, the system behaved more and more like a weak-post guardrail, where the posts upstream of the vehicle failed at an appropriate time, thereby preventing pocketing. However, the analyses did show that the loading on the w-beam splice at Post 16 (i.e., critical splice location for the analysis) resulted in relatively high local strains at the edges of the splice-bolt holes. The magnitude of these strains, for all cases, exceeded the failure strain of the material indicating a potential for a tear initiation. As post deterioration levels increased, the strain magnitudes increased to levels that indicated a high potential for rail rupture. In the second damage scenario, the stiffer posts located downstream of the impact point helped to limit the lateral deflections of the rail, compared to those of the first damage scenario. In this case, the loading on the downstream anchor increased only slightly as the post

228 deterioration levels increased, while the loading on the upstream anchor was somewhat more notable. The potential for pocketing was higher for this damage scenario and increased as post deterioration levels increased. The critical impact point (CIP) for the undamaged G4(2W) guardrail was used for all cases. That is, the CIP was not determined for the various guardrail damage cases; thus the results presented herein are to be considered less severe than they might otherwise have been. Recommendations Four levels of deterioration for wood guardrail posts were defined in terms of load and energy capacity of the post data, as well as in terms of relative capacity. Therefore, if post strength is measured or otherwise determined in the field (e.g., stress wave techniques, force- deflection techniques, resistograph, etc.) then the relative capacity may be used to identify damage level.[Hron11] As a result of this study, the authors recommend that the repair threshold for wood post deterioration be those exceeding DL2 deterioration levels. If there are fixed/rigid objects located within 42 inches behind the guardrail, then posts with damage levels of DL2 or greater should be replaced with high priority. Otherwise, posts with damage level DL2 are considered to be of medium priority for replacement. Posts with damage level DL3 are essentially non-functional and are considered to be of high priority for replacement. If strength and/or deterioration measurement tools are not available, then visual inspection and “sounding” procedures should be utilized by experienced maintenance personnel to assess the soundness of the posts. If it is determined that replacement of guardrail post(s) is warranted, (e.g., in a crash damaged section), then the posts immediately upstream and downstream of the repair section should also be checked for damage/deterioration to ensure stiffness compatibility of the repair section with the existing guardrail. If the adjacent posts are DL1 or better then only the posts in the damaged region need to be replaced. If the adjacent posts are DL2, then either (1) all posts in the system should be replaced with new posts or (2) the damaged posts in the immediate repair section should be replaced with posts of equivalent strength to DL1 (e.g., new posts with reduced cross-section). From available test data, new round wood posts with a diameter of 7.2 to 7.6 inches meet this condition. These diameters also meet the minimum size criteria for round posts (i.e., 8 ± 1 inches). If the adjacent posts are DL3 then, according to the aforementioned criteria, all posts in the system should be replaced since the deterioration state of the existing system renders it non-functional. A summary of the recommendations regarding wood post deterioration are presented in Table 54.

229 Table 54. Recommendations for wood post deterioration damage. Damage Mode Relative Priority One or more posts: High - Missing - Cracked across grain - Broken High High Medium - - - Damaged posts should be replaced with posts of equivalent strength to DL1 (e.g., posts with reduced cross-section)** - OR, all posts in the system should be replaced with new posts. - - Young's modulus = TBD Repair Threshold Posts with damage level 3 (DL3) should be replaced with high priority (i.e., rotted posts). These cases include:* - Resi Score < 25 - Break strength < 9 kips - Rupture energy < 20 kip-in - Relative strength capacity < 45% - Young's modulus = TBD If a hazard is located within 42 inches behind the face of the w-beam rail, then posts with damage level 2 (DL2) or worse should be replaced with high priority. If adjacent posts are DL3, then the repair section should be expanded to include those posts as well (see above). If strength and/or deterioration measurement tools are not available, then visual inspection and "sounding" procedures should be utilized by experienced maintenance personnel to asses the soundness of the posts. Any posts with visual rot, mildew, or mold at the groundline should be further inspected for soundness. From available test data, new posts with diameters equal 7.2 - 7.6 inches meet this condition. These diameter values also meet the minimum size criteria for round posts (e.g., 8 ± 1 inches). Missing or Broken Posts Rot or Insect Damaged Posts ! Otherwise, posts with damage level DL2 should be replaced with medium priority. – If Repair is Warranted: – If post replacement is warranted (e.g., in a crash damaged section) then the posts immediately adjacent to the repair section should also be checked for damage/deterioration to ensure stiffness compatibility. If adjacent posts are DL1 or better then only the posts in the damage region need be replaced. If adjacent posts are DL2, then: These cases include:* - Resi Score < 35 - Break strength < 12 kips - Rupture energy < 26 kip-in - Relative strength capacity < 55%