AASHTO Load Rating Provisions for Implements of Husbandry (2020) / Chapter Skim
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From page 5... ...
5 Findings and Applications 3.1 Bridge Owner Survey and the State of the Practice 3.1.1 Survey In the first phase of the study, a questionnaire was developed and a survey was conducted, mainly focusing on state agencies. The questionnaire, included in Appendix D of this report, was finalized based on the comments of NCHRP and the project panel.
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6 Proposed AASHTO Load Rating Provisions for Implements of Husbandry transportation (DOTs) of Iowa, Illinois, Kansas, Minnesota, Nebraska, Oklahoma, and Wisconsin, and the USDA Forest Products Laboratory through the Transportation Pooled Fund Program; and an effort sponsored by the Wisconsin DOT in implementing a new IoH load-rating procedure, for local bridge owners to opt in or out.
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Findings and Applications 7 transportation agency (Quebec)
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8 Proposed AASHTO Load Rating Provisions for Implements of Husbandry Consumer Protection, convened a study group. It involved more than 20 stakeholders representing various transportation and farm organizations, equipment manufacturers, law enforcement, local officials, and the University of Wisconsin -- Madison Division of Extension.
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Findings and Applications 9 Some of the most relevant items are reviewed here, and knowledge gaps to be addressed in this study are identified.
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Table 3.2.1-1. Two-axle IoH vehicles.
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Findings and Applications 11 Total Weight (kips) 1 Grain Semi Semitrailer 68 2 John Deere 8520 & Houle 2-Axle Tank Manure Tanker 85 3 New Holland TD5050 & Houle 2-Axle Tank Manure Tanker 79 4 New Holland T4040 & Houle 2-Axle Tank 76 5 John Deere 8520 & Balzer 6350 Narrow Manure Tanker 95 6 New Holland TD5050 & Balzer 6350 Narrow Manure Tanker 89 7 New Holland T4040 & Balzer 6350 Narrow 86 8 John Deere 8520 & Better-Bilt 3400 Manure Tanker 60 9 New Holland TD5050 & Better-Bilt 3400 Manure Tanker 53 10 New Holland T4040 & Better-Bilt 3400 50 11 John Deere 8520 & Better-Bilt 4950 Manure Tanker 78 12 New Holland TD5050 & Better-Bilt 4950 Manure Tanker 71 13 New Holland T4040 & Better-Bilt 4950 68 14 Versatile 280 & Better-Bilt 4950 Manure Tanker 82 15 Versatile 280 & Better-Bilt 3400 Manure Tanker 65 16 Versatile 280 & Balzer 6350 Narrow Manure Tanker 100 17 Versatile 280 & Houle 2-Axle Tank Manure Tanker 90 18 John Deere 9200 & Better-Bilt 4950 Manure Tanker 92 19 John Deere 9200 & Better-Bilt 3400 Manure Tanker 74 20 John Deere 9200 & Balzer 6350 Narrow Manure Tanker 110 21 John Deere 9200 & Houle 2-Axle Tank Manure Tanker 100 22 Case 380 & Better-Bilt 4950 Manure Tanker 91 23 Case 380 & Better-Bilt 3400 Manure Tanker 73 24 Case 380 & Balzer 6350 Narrow Manure Tanker 109 25 Case 380 & Houle 2-Axle Tank Manure Tanker 99 26 John Deere 9620 & Better-Bilt 4950 Manure Tanker 95 27 John Deere 9620 & Better-Bilt 3400 Manure Tanker 77 28 John Deere 9620 & Balzer 6350 Narrow Manure Tanker 113 29 John Deere 9620 & Houle 2-Axle Tank Manure Tanker 103 30 John Deere 9620 & Balzer 1250 Grain Cart 127 31 John Deere 8520 & Balzer 1250 Grain Cart 110 32 John Deere 9200 & Balzer 1250 Grain Cart 125 33 Versatile 280 & Balzer 1250 Grain Cart 115 34 Case 380 & Balzer 1250 Grain Cart 123 No.
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12 Proposed AASHTO Load Rating Provisions for Implements of Husbandry 41 Case 600 & Balzer 1250 133 42 Versatile 535 & Better-Bilt 4950 100 43 Versatile 535 & Better-Bilt 3400 82 44 Versatile 535 & Balzer 6350 Narrow 117 45 Versatile 535 & Houle 2-Axle Tank 108 46 Versatile 535 & Balzer 1250 132 47 Cotton Module Mover 88 48 T1 -- John Deere 8430 w/Houle Tank 45 49 T2 -- M. Ferguson 8470 w/Husky Tank 31 50 T6 -- John Deere 8230 w/ Husky Tank 46 Total Weight (kips)
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Findings and Applications 13 No. Name Remarks Total Weight (kips)
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14 Proposed AASHTO Load Rating Provisions for Implements of Husbandry 3.2.3 Load Volume and Frequency Load volume and frequency of IoH could greatly affect the live load model and load factor for bridge load rating. The current AASHTO MBE's live load factors were derived using truckload data (Nowak 1999; Moses 2001)
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Findings and Applications 15 distribution factors for IoH in or around the Iowa area by analyzing 121 IoH vehicles and by physically testing five local bridges for finite element model calibration as well as for the dynamic impact of IoH (Seo, Phares, and Wipf 2014; Phares 2015, 2016; Seo and Hu 2015; Abu-Hawash and Phares 2016)
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16 Proposed AASHTO Load Rating Provisions for Implements of Husbandry On the other hand, the dynamic amplification factor or impact factor obtained from physical testing is a percentage (or a fraction) increase from the static response for the total response of the applied load.
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Findings and Applications 17 between the vehicles and the speed bumps, as well as dynamic load allowance factors for the bridge. Szurgott et al.
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18 Proposed AASHTO Load Rating Provisions for Implements of Husbandry c. Vehicle mass and speed are directly proportional to dynamic effects of the vehicle–bridge system that they trigger.
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Findings and Applications 19 Figure 3.2.5-3. Recorded dynamic responses of deflection with (a)
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20 Proposed AASHTO Load Rating Provisions for Implements of Husbandry TerraGator Honey Wagon Tractor Grain Wagon Honey Wagon with two tanks Figure 3.2.5-5. IoH loading vehicles used in pooled fund study (Freeseman et al.
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Findings and Applications 21 Figure 3.2.5-7. Typical road surface of load-tested bridge (Iowa Bridge 68790, with timber beams supporting timber deck)
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22 Proposed AASHTO Load Rating Provisions for Implements of Husbandry Figure 3.2.5-9. Typical road surface of load-tested bridge (Iowa Bridge 126252, with steel beams supporting timber deck)
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Findings and Applications 23 Note that the total response in Equation 3.2.5-3 was referred to as "dynamic strain" and the pseudo-static response was referred to as "static strain" in Phares and Greimann (2015) and Freeseman et al.
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24 Proposed AASHTO Load Rating Provisions for Implements of Husbandry or one point per 0.01 second. Data points had to be converted to distance as shown in Figure 3.2.5-10, using the respective speeds of the two runs.
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Findings and Applications 25 at the third peak (corresponding to the grain cart axle load)
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26 Proposed AASHTO Load Rating Provisions for Implements of Husbandry How to account for the presence of multiple vehicles on the same span has not received attention in previous studies on IoH (Seo, Phares, and Wipf 2014; Dahlberg 2015; Phares 2015; Phares and Greimann 2015; Seo and Hu 2015; Freeseman et al. 2017; Greimann et al.
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Findings and Applications 27 to be overconservative by WIM data in NCHRP Project 12-63 (Sivakumar et al.
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28 Proposed AASHTO Load Rating Provisions for Implements of Husbandry defined as a side-by-side occurrence, its probability is averaged at 0.045% for an ADTT of 4,214. This value is negligible compared with the 1/15 (6.7%)
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Findings and Applications 29 Alabama DOT Study Uddin et al.
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30 Proposed AASHTO Load Rating Provisions for Implements of Husbandry Illinois DOT Study This latest study (Fu, Chi, and Wang 2019) gathered WIM data from all 20 stations in Illinois to calibrate the live load factors for LRFR in the jurisdiction, including permit loads.
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Findings and Applications 31 direction. More specifically, span collapse is an observed risk to the bridge population directly relevant to IoH loads, such as those on local roads.
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32 Proposed AASHTO Load Rating Provisions for Implements of Husbandry 2. Wisconsin DOT IoH permit application records from after the state IoH program was established in 2015; 3.
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Table 3.4-1. Two-axle IoH for developing notional model (all tractors except four agricultural equipment trucks)
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34 Proposed AASHTO Load Rating Provisions for Implements of Husbandry Table 3.4-3. Four-axle IoH for developing notional model (tractors hauling two-axle equipment, tank, or trailer, except one agricultural truck)
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Table 3.4-5. Six-axle IoH for developing notional model (tractors hauling two empty two-axle tanks)
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36 Proposed AASHTO Load Rating Provisions for Implements of Husbandry This model consists of three IoH vehicles designated as (a)
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Findings and Applications 37 vehicles. Its live load distribution factors likely need to be different from those in current AASHTO bridge specifications for design and evaluation.
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38 Proposed AASHTO Load Rating Provisions for Implements of Husbandry 3.5 Live Load Lateral Distribution 3.5.1 Finite Element Modeling for Live Load Distribution Live load distribution among parallel members, such as primary beams, is a significant concern in IoH load rating because the vehicle gauge width is different from the standard 6 ft of typical highway trucks. AASHTO BDS and MBE do not include provisions on how to distribute live load for vehicles with gauge width other than 6 ft.
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Findings and Applications 39 Figure 3.5.1-1. Elevation and bottom views of Swan Road Bridge (Catbas et al.
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40 Proposed AASHTO Load Rating Provisions for Implements of Husbandry Figure 3.5.1-4 displays the finite element model developed using CSiBridge for the present study. Figure 3.5.1-5 compares deflection results measured in the load tests reported in Catbas, Gokce, and Gul (2012)
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Findings and Applications 41 Figure 3.5.1-6. Elevation and end views of Iowa Bridge 78060 (Freeseman et al.
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42 Proposed AASHTO Load Rating Provisions for Implements of Husbandry The bridge's cross section consists of seven interior steel girders and two exterior concrete girders with a spacing between adjacent girders of 2.5 ft, as shown in Figure 3.5.1-7. The steel I girders are approximately 18 in.
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Findings and Applications 43 Figure 3.5.1-10. Bottom view of Iowa Bridge 78060 with steel in facia concrete beams exposed.
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44 Proposed AASHTO Load Rating Provisions for Implements of Husbandry Figure 3.5.1-12. Measured bottom surface strains in beams G1 to G9 of Iowa Bridge 78060, with symmetric beams averaged (pooled fund study, unpublished data set)
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Findings and Applications 45 3.5.2 Scope of Bridge Types and Spans For the derivation of live load distribution factor for IoH vehicles, a scope of span types is needed to ensure that the planned product will be able to address the needs of bridge owners facing the issue of IoH load rating. Table 3.1.1-1, based on the questionnaire responses, has identified those span types of interest.
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46 Proposed AASHTO Load Rating Provisions for Implements of Husbandry Table 3.5.2-3. Timber slab spans.
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Span Length Deck Thickness Bridge Roadway Width Beam Spacing Number of Beams L(ft)
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48 Proposed AASHTO Load Rating Provisions for Implements of Husbandry Span Length Beam Spacing Deck Thickness Roadway Width Number of Beams L(ft)
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Findings and Applications 49 (c) Span length 55 ft.
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(a) Span length 20 ft.
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Findings and Applications 51 (c) Span length 60 ft.
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52 Proposed AASHTO Load Rating Provisions for Implements of Husbandry (a) Span length 20 ft.
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Findings and Applications 53 (b) Span length 40 ft.
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54 Proposed AASHTO Load Rating Provisions for Implements of Husbandry (c) Span length 60 ft.
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Findings and Applications 55 (a) Span length 20 ft.
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56 Proposed AASHTO Load Rating Provisions for Implements of Husbandry (b) Span length 25 ft.
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Findings and Applications 57 As a first step, the standard HL93 truck is compared with the 115% of FBF notional IoH model vehicle in Figures 3.4-1a and 3.4-1b, both with a dual-tire steering axle and GW of 6 ft. Figure 3.5.3-1 displays this comparison showing the respective DF values in the vertical and horizontal axes.
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58 Proposed AASHTO Load Rating Provisions for Implements of Husbandry Accordingly, the live load distribution of IoH load with various GW is treated hereafter as a modified AASHTO live load distribution factor for GW at standard gauge width of 6 ft. This modification needs to account for different GW and possibly other span types and span geometry parameters.
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Findings and Applications 59 where GW = IoH vehicle gauge width in ft S = Beam spacing in ft ts = Deck thickness L = Span length in ft The application ranges for Equations 3.5.3-3 to 3.5.3-6 are 3.5 ≤ S ≤ 14 (ft)
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60 Proposed AASHTO Load Rating Provisions for Implements of Husbandry 3. MFbeam for Spans of Timber Beams Supporting Timber Deck for IoH Vehicles with Dual-Wheel and Multitire Axles: Case (l)
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Findings and Applications 61 For interior longitudinal beams' shear with DFBDS in BDS Table 4.6.2.2.3a-1: 1 0.863 6 12 0.88 (3.5.3-17) 1 0.25 2MF R Ln GW S Rbeam = − = For exterior longitudinal beams' shear with DFBDS in BDS Table 4.6.2.2.3b-1: 1 0.526 6 12 0.78 (3.5.3-18)
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62 Proposed AASHTO Load Rating Provisions for Implements of Husbandry The application ranges for Equations 3.5.3-19 to 3.5.3-22 are 3 ≤ b ≤ 5 (ft)
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Findings and Applications 63 For edge longitudinal strip equivalent width in LRFD Design Article 4.6.2.1.4b: 1 (3.5.3-28) MFslab = The edge strip load effect is dominated by one of the two wheel lines of the vehicle near the edge, and thus is not much affected by the gauge width.
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64 Proposed AASHTO Load Rating Provisions for Implements of Husbandry 3.5.4 Effects of Tracked Wheels Some IoH vehicles are equipped with tracked wheels to distribute load or to facilitate maneuverability. This is particularly true for the tractor, as the hauling power of the IoH.
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Findings and Applications 65 to point (1,1) , they indicate the same DF for the two load models.
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66 Proposed AASHTO Load Rating Provisions for Implements of Husbandry is the live load distribution factor for dual spacing equal to 0, which is the model used in BDS, SSHB, and MBE, as well as that used in this study so far. The vertical axis is the same live load distribution factor for the same member and load effect (moment or shear)
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Findings and Applications 67 3.5.6 Effects of Single-Tire Steering Axle Besides variation in gauge width, IoH axle configurations can be different from typical commercial vehicles in other ways. A unique case of IoH vehicle type in terms of its wheel load distribution is referred to as a "TerraGator." Its steering axle has only one wheel and one tire.
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68 Proposed AASHTO Load Rating Provisions for Implements of Husbandry A notional model has also been developed as shown in Figure 3.4-1c for these TerraGators. This model is intended to envelop typical TerraGators up to 115% of FBF.
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Findings and Applications 69 where GW = IoH vehicle gauge width in ft S = Beam spacing in ft ts = Deck thickness L = Span length in ft The application ranges for Equations 3.5.6-3 to 3.5.6-6 are 3.5 ≤ S ≤ 14 (ft)
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70 Proposed AASHTO Load Rating Provisions for Implements of Husbandry 3. MFbeam for Spans of Timber Beams Supporting Timber Deck for IoH Vehicles with SingleWheel and Single-Tire Steering Axle (TerraGator)
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Findings and Applications 71 For interior longitudinal beams' shear with DFBDS in BDS Table 4.6.2.2.3a-1: 3.013 1 0.70 (3.5.6-17) 2 0.239 0.662 0.597 2MF R GW S S L L Rbeam = = − − For exterior longitudinal beams' shear with DFBDS in BDS Table 4.6.2.2.3b-1: = = − 1.297 6 0.89 (3.5.6-18)
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72 Proposed AASHTO Load Rating Provisions for Implements of Husbandry The application ranges for Equations 3.5.6-19 to 3.5.6-22 are 3 ≤ b ≤ 5 (ft)
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Findings and Applications 73 For edge longitudinal strip equivalent width in LRFD Design Article 4.6.2.1.4b: 1 (3.5.6-28) MFslab = The edge strip load effect is dominated by one of the two wheel lines of the vehicle near the edge, and thus is not much affected by the gauge width.
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74 Proposed AASHTO Load Rating Provisions for Implements of Husbandry In this section, the concept of Fourier filtration is presented first for deriving IM factor from physical load test data. These tests use one or multiple vehicles to load the bridge structure, with bridge components' responses measured.
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Findings and Applications 75 H( f ) in Equation 3.6.1-1 is referred to as the Fourier transform of h(t)
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76 Proposed AASHTO Load Rating Provisions for Implements of Husbandry Here the Fourier transform's amplitude |H( f ) | is used in Figure 3.6.1-2 to show the frequency contents in these two response records.
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Findings and Applications 77 This practice is also illustrated in Figure 3.6.1-3, in which the total response (solid line) is expressed as the sum of static (dashed line)
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78 Proposed AASHTO Load Rating Provisions for Implements of Husbandry Note that in practical application, the total response is physically measured, but the static response and dynamic response are to be identified using the Fourier series via Fourier transform. The latter is widely available as FFT in general software programs such as Excel and Matlab.
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Findings and Applications 79 2. In Stages 1 and 3, there should be no load-induced strains.
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80 Proposed AASHTO Load Rating Provisions for Implements of Husbandry 4. Filter out dynamic response after its major frequency is identified.
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Findings and Applications 81 After the high-frequency oscillation is filtered accordingly, Figure 3.6.1-7 shows the same Fourier transform amplitude for the remaining static component of total strain response. Compared with Figure 3.6.1-6, the second group/bandwidth corresponding to the dynamic component has been removed.
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82 Proposed AASHTO Load Rating Provisions for Implements of Husbandry Frequency f (Hz)
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Findings and Applications 83 and was one of the two girders most severely loaded by the loading vehicle, the other being Girder 6 symmetric to Girder 4. Note also that Girder 5 in the middle was loaded slightly less severely because the two wheel lines were closer to Girders 4 and 6, and farther away from Girder 5 in the middle.
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84 Proposed AASHTO Load Rating Provisions for Implements of Husbandry to the right shows more significant dynamic behavior with oscillating strains at a higher frequency, more visible near the third peak, at the third peak area around Data Point 480. This peak corresponds to the third axle of the loading vehicle being over the strain sensor near midspan.
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Findings and Applications 85 and approach surface significantly affect dynamic amplification in bridge member response to vehicle load in motion. 3.6.3 IM Factor for LRFR and I for LFR Based on Load Test Results Dynamic load allowance IM factor in BDS and impact factor I in SSHB refer to the same physical variable to cover moving vehicles' additional load effect to the static counterpart.
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86 Proposed AASHTO Load Rating Provisions for Implements of Husbandry typical IoH vehicles. The figure shows only about a dozen cases beyond 35 mph, and the vast majority are at or below 20 mph.
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Findings and Applications 87 Steel/Concrete Bridges Figure 3.6.3-3. IM factor extracted from moving load tests for all five steel/concrete bridges.
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88 Proposed AASHTO Load Rating Provisions for Implements of Husbandry steel/timber, and timber/timber bridges. Each figure has both semi and IoH loads plotted for comparison.
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Findings and Applications 89 IoH to travel on public roads, which makes recoding IoH impossible since all WIM stations are on public roads. More specifically, the long-term pavement performance program has gathered WIM data all from Interstate or other principal arterial roads.
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90 Proposed AASHTO Load Rating Provisions for Implements of Husbandry by month. The total ADTT varied from 9 to 69 for both directions, and from 5 to 36 for one direction.
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Findings and Applications 91 criteria with the respective state agencies, was then confirmed. The Ohio records are mainly trucks, including IoH, with much fewer light vehicles.
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92 Proposed AASHTO Load Rating Provisions for Implements of Husbandry load effects, which are calculated using live load models for bridge load rating. For the example of IoH Tier 1 load for bending moment, this is the moment ratio between the notional models in Figure 3.7.2-1 and the AASHTO legal-load model (NRL)
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Findings and Applications 93 This relative calibration approach has been used by Moses (2001) in calibrating the live load factors for load rating.
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94 Proposed AASHTO Load Rating Provisions for Implements of Husbandry 3.7.4 Calibration Results for IoH Load Rating The calibration for IoH live load factors was performed using the collected WIM data. These data have recorded IoH vehicles from Minnesota, Montana, and Ohio, as discussed previously.
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Findings and Applications 95 Figures 3.7.4-1 through 3.7.4-3 display the computed CF for the three respective WIM sites using Equations 3.7.4-2 and 3.7.4-3 for recorded vehicular loads in the individual lanes for simple bridge spans from 20 to 220 ft long. The CF is seen averaged at about 1.0.
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96 Proposed AASHTO Load Rating Provisions for Implements of Husbandry According to these results, IoH Tier 1 load rating is recommended to use a CF of 1.0 along with one-lane loading. For LRFD, the live load factors in Equation 3.7.4-1 are recommended to be used for an IoH Tier 1 load.
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Findings and Applications 97 ' ' for one-lane load ' ' (3.7.4-4) , 2 , , , 2 2,5- ,5- , 2 2,5- ,5- LE LE LE LE LE LE OneLaneLoad sLE OneLaneLoad sLE CF CF LE LE OneLaneLoad sLE OneLaneLoad sLE L IoHTier L ref n ref n ref L ref AnnualPermit IoHTier IoHuptoTier year projected TrucksuptoAnnualPermit year projected L ref AnnualPermit IoHTier IoHuptoTier year projected TrucksuptoAnnualPermit year projected γ = γ = γ × × = γ = × ' ' for two-lane load ' ' (3.7.4-5)
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98 Proposed AASHTO Load Rating Provisions for Implements of Husbandry 0.00 0.50 1.00 1.50 0 50 100 150 200 250 Ca lib ra tio n Fa ct or Span (ft) Minnesota Lane 1 Moment Lane 2 Moment Lane 1 Left Shear Lane 2 Left Shear Lane 1 Right Shear Lane 2 Right Shear Figure 3.7.4-6.
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Findings and Applications 99 0.00 0.50 1.00 1.50 0 50 100 150 200 250 Ca lib ra tio n Fa ct or Span (ft) Ohio EB Moment WB Moment EB Left Shear WB Left Shear EB Right Shear WB Right Shear Figure 3.7.4-8.
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100 Proposed AASHTO Load Rating Provisions for Implements of Husbandry 3.8 Proposed Revisions to Current AASHTO Specifications NCHRP Project 12-110 includes a deliverable of new proposed provisions to the AASHTO BDS and MBE regarding IoH load rating, and possibly permit issuance as appropriate. Review of these two sets of AASHTO specifications has identified areas in MBE to be revised when implementing these findings.
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