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From page 217... ... 217 In Chapter 6, various articles of AASHTO LRFD were identified that would need to be modified to implement the calibrated SLS resulting from this research. This chapter contains the suggested modifications formatted in a form suitable for consideration by the affected technical committees that could be potential AASHTO Highway Subcommittee on Bridges and Structures agenda items. Read the entire page →
From page 218... ... 218 7.1 Foundation Deformations – Service I 7.1.1 Proposed Revisions to Section 3 3.4 -- LOAD FACTORS AND COMBINATIONS 3.4.1 -- Load Factors and Load Combinations • • • • C3.4.1 • Service I -- Load combination relating to the normal operational use of the bridge with a 55 mph wind and all loads taken at their nominal values. Also related to deflection control in buried metal structures, tunnel liner plate, and thermoplastic pipe, to control crack width in reinforced concrete structures, and for transverse analysis relating to tension in concrete segmental girders. Read the entire page →
From page 219... ... 219 expansion forces are included. • • • • The evaluation of overall stability of retained fills, as well as earth slopes with or without a shallow or deep foundation unit should be investigated at the service limit state based on the Service I Load Combination and an appropriate resistance factor as specified in Article 11.5.6 and Article 11.6.2.3. Read the entire page →
From page 220... ... 220 The effects of the foundation deformation on the bridge superstructure, retaining walls, or other load bearing structures shall be evaluated at applicable strength and service limit states using the provisions of Article 10.5.2.2 and the settlement load factor (γSE) specified in Table 3.4.1-4. Read the entire page →
From page 221... ... 221 Table 3.4.1-4 -- Load Factors for Permanent Loads Due to Foundation Deformations, γSE Foundation Deformation and Deformation Estimation Method SE Immediate Settlement • Hough method 1.00 • Schmertmann method 1.25 • Local method * Consolidation settlement 1.00 Lateral Deformation • Soil-structure interaction method (P-y or Strain Wedge) Read the entire page →
From page 222... ... 222 7.1.2 Proposed Revisions to Section 10 10.3 -- NOTATION Ad = angular distortion (10.5.2) Adm = modified angular distortion (10.5.2) Read the entire page →
From page 223... ... 223 The foundations for retaining walls and other load bearing structures such as tunnels may also be evaluated using the provisions of this Article. The design flood for scour is defined in Article 2.6.4.4.2, and is specified in Article 3.7.5 as applicable at the service limit state. Read the entire page →
From page 224... ... 224 the bridge components should consider the effects of cracking, creep, and other inelastic responses Example: In Figure C10.5.2.2-1, a hypothetical 4span bridge structure with span lengths, Ls1, Ls2, Ls3 and Ls4. The relevant total settlement, Str, is computed at each support element and the profile of Str along the bridge is shown by the solid line. Read the entire page →
From page 225... ... 225 values of γSE for lateral deformations. 10.5.2.2.3 -- Walls The procedure for computing angular distortions shall also be applied for evaluating angular distortions along and transverse to retaining walls as well as the junction of the approach walls to abutment walls. Read the entire page →
From page 226... ... 226 and secondary components may be taken as: t e c sS S S S= + + (10.6.2.4.1-1) where: Se = elastic settlement (ft) Read the entire page →
From page 227... ... 227 Figure 10.6.2.4.1-1 -- Boussinesq Vertical Stress Contours for Continuous and Square Footings Modified after Sowers (1979) 10.6.2.4.2 -- Settlement of Footings on Cohesionless Soils 10.6.2.4.2a -- General C10.6.2.4.2a The settlement of spread footings bearing on cohesionless soil deposits shall be estimated as a function of effective footing width and shall consider the effects of footing geometry and soil and rock layering with depth. Read the entire page →
From page 228... ... 228 textbooks and engineering manuals, including: • Terzaghi and Peck (1967) • Sowers (1979) Read the entire page →
From page 229... ... 229 Table 10.6.2.4.2b-1 -- Elastic Shape and Rigidity Factors, EPRI (1983) L/B Flexible, βz (average) Read the entire page →
From page 230... ... 230 Figure 10.6.2.4.2c-1 -- Bearing Capacity Index versus Corrected SPT (Samtani and Nowatzki, 2006, after Hough, 1959) The Hough method is applicable to cohesionless soil deposits. Read the entire page →
From page 231... ... 231 axisymmetric case (Lf/Bf = 1) and the plane strain case (Lf/Bf ≥ 10) Read the entire page →
From page 232... ... 232 (b) Figure 10.6.2.4.2d-1 -- (a) Read the entire page →
From page 233... ... 233 7.2 Live Load Response 7.2.1 Proposed Revisions to Section 2 2.5.2.6 -- Deformations 2.5.2.6.1 -- General • • • • C2.5.2.6.1 • • • • 2.5.2.6.2 -- Criteria for Deflection Live Load Response The criteria in this Section shall be considered optional, except for the following: • The provisions for orthotropic decks shall be considered mandatory. • The provisions in Article 12.14.5.9 for precast reinforced concrete three-sided structures shall be considered mandatory. Read the entire page →
From page 234... ... 234 stiffness determined as specified above, divided by the number of girders; • When investigating maximum relative displacements, the number and position of loaded lanes should be selected to provide the worst differential effect; • The live load portion of Load Combination Service I of Table 3.4.1-1 should be used, including the dynamic load allowance, IM; • The live load shall be taken from Article 3.6.1.3.2; • The provisions of Article 3.6.1.1.2 should apply; and • For skewed bridges, a right cross-section may be used, and for curved and curved skewed bridges, a radial cross-section may be used. In the absence of other criteria, the following deflection limits may be considered for steel, aluminum, and/or concrete vehicular bridges: should meet the criteria shown in Figure 2.5.2.6.1-1 for the anticipated level of pedestrian usage. Read the entire page →
From page 235... ... 235 and tub girders, the provisions of Articles 6.10.4.2 and 6.11.4, respectively, regarding the control of permanent deflections through flange stress controls, shall apply. For pedestrian bridges, i.e., bridges whose primary function is to carry pedestrians, bicyclists, equestrians, and light maintenance vehicles, the provisions of Section 5 of AASHTO's LRFD Guide Specifications for the Design of Pedestrian Bridges shall apply. Read the entire page →
From page 236... ... 236 analysis relating to tension in prestressed concrete superstructures with the objective of crack control and to principal tension in the webs of segmental concrete girders. reflects, among other things, current exclusion weight limits mandated by various jurisdictions. Read the entire page →
From page 237... ... 237 Table 3.4.1-1 -- Load Combinations and Load Factors Load Combination Limit State DC DD DW EH EV ES EL PS CR SH LL IM CE BR PL LS WA WS W L FR TU TG SE Use One of These at a Time EQ BL IC CT CV Strength I (unless noted) γp 1.75 1.00 -- -- 1.00 0.50/1.20 γTG γSE -- -- -- -- -- Strength II γp 1.35 1.00 -- -- 1.00 0.50/1.20 γTG γSE -- -- -- -- -- Strength III γp -- 1.00 1.40 -- 1.00 0.50/1.20 γTG γSE -- -- -- -- -- Strength IV γp -- 1.00 -- -- 1.00 0.50/1.20 -- -- -- -- -- -- -- Strength V γp 1.35 1.00 0.40 1.0 1.00 0.50/1.20 γTG γSE -- -- -- -- -- Extreme Event I γp γEQ 1.00 -- -- 1.00 -- -- -- 1.00 -- -- -- -- Extreme Event II γp 0.50 1.00 -- -- 1.00 -- -- -- -- 1.00 1.00 1.00 1.00 Service I 1.00 1.00 1.00 0.30 1.0 1.00 1.00/1.20 γTG γSE -- -- -- -- -- Service II 1.00 1.30 1.00 -- -- 1.00 1.00/1.20 -- -- -- -- -- -- -- Service III 1.00 0.80 1.00 -- -- 1.00 1.00/1.20 γTG γSE -- -- -- -- -- Service IV 1.00 -- 1.00 0.70 -- 1.00 1.00/1.20 -- 1.0 -- -- -- -- -- Service V 1.00 1.50 -- -- -- -- -- -- -- -- -- -- -- -- Fatigue I -- LL, IM & CE only -- 1.50 -- -- -- -- -- -- -- -- -- -- -- -- Fatigue II -- LL, IM & CE only -- 0.75 -- -- -- -- -- -- -- -- -- -- -- -- Read the entire page →
From page 238... ... 238 7.3 Premature Yielding and Slip of Bolts – Service II 7.3.1 Proposed Revisions to Section 3 3.4 -- LOAD FACTORS AND COMBINATIONS • • • • • Service I -- Load combination relating to the normal operational use of the bridge with a 55 mph wind and all loads taken at their nominal values. Also related to deflection control in buried metal structures, tunnel liner plate, and thermoplastic pipe, to control crack width in reinforced concrete structures, and for transverse analysis relating to tension in concrete segmental girders. Read the entire page →
From page 239... ... 239 • Service IV -- Load combination relating only to tension in prestressed concrete columns with the objective of crack control. The 0.70 factor on wind represents an 84 mph wind. Read the entire page →
From page 240... ... 240 7.4 Cracking of Prestressed Concrete – Currently Service III 7.4.1 Proposed Revisions to Section 3 3.4 -- LOAD FACTORS AND COMBINATIONS 3.4.1 -- Load Factors and Load Combinations The total factored force effect shall …………….. Read the entire page →
From page 241... ... 241 currently-specified Refined Estimates of TimeDependent Losses method, an increase in the load factor for live load from 0.8 to 1.0 was required to maintain the level of reliability against cracking of prestressed concrete components inherent in the system. Components which design satisfies all of the following conditions: • A refined time step method is used for calculating the time-dependent prestressing losses • The section properties are determined based on the concrete gross section, and, • The force in prestressing steel is determined without taking advantage of the elastic gain, were not affected by the changes in the prestressing loss calculation method introduced in 2005. Read the entire page →
From page 242... ... 242 Table 3.4.1-4 -- Load Factors for Live Load for Service III Load Combination, γLL Component γLL Prestressed concrete components designed using a refined time step method to determine the time-dependant prestressing losses in conjunction with the gross section properties and without taking advantage of the elastic gain 0.8 All other prestressed concrete components 1.0 Read the entire page →
From page 243... ... 243 7.5 Fatigue 7.5.1 Proposed Revisions to Section 3 3.4 -- LOAD FACTORS AND COMBINATIONS • • • • Table 3.4.1-1 -- Load Combinations and Load Factors Load Combination Limit State DC DD DW EH EV ES EL PS CR SH LL IM CE BR PL LS WA WS WL FR TU TG SE Use One of These at a Time EQ BL IC CT CV Strength I (unless noted) γp 1.75 1.00 -- -- 1.00 0.50/1.20 γTG γSE -- -- -- -- -- Strength II γp 1.35 1.00 -- -- 1.00 0.50/1.20 γTG γSE -- -- -- -- -- Strength III γp -- 1.00 1.4 0 -- 1.00 0.50/1.20 γTG γSE -- -- -- -- -- Strength IV γp -- 1.00 -- -- 1.00 0.50/1.20 -- -- -- -- -- -- -- Strength V γp 1.35 1.00 0.4 0 1.0 1.00 0.50/1.20 γTG γSE -- -- -- -- -- Extreme Event I γp γEQ 1.00 -- -- 1.00 -- -- -- 1.00 -- -- -- -- Extreme Event II γp 0.50 1.00 -- -- 1.00 -- -- -- -- 1.00 1.00 1.00 1.00 Service I 1.00 1.00 1.00 0.3 0 1.0 1.00 1.00/1.20 γTG γSE -- -- -- -- -- Service II 1.00 1.30 1.00 -- -- 1.00 1.00/1.20 -- -- -- -- -- -- -- Service III 1.00 0.80 1.00 -- -- 1.00 1.00/1.20 γTG γSE -- -- -- -- -- Service IV 1.00 -- 1.00 0.7 0 -- 1.00 1.00/1.20 -- 1.0 -- -- -- -- -- Fatigue I -- LL, IM & CE only -- 1.50 2.0 -- -- -- -- -- -- -- -- -- -- -- -- Fatigue II -- LL, IM & CE only -- 0.75 0.80 -- -- -- -- -- -- -- -- -- -- -- -- 7.5.2 Proposed Revisions to Section 5 5.5.3 Fatigue Limit State • • • • Read the entire page →
From page 244... ... 244 5.5.3.2 -- Reinforcing Bars The constant-amplitude fatigue threshold, (ΔF) TH, for straight reinforcement and welded wire reinforcement without a cross weld in the high-stress region shall be taken as: ( ) Read the entire page →
From page 245... ... 245 6.6.1.2.3 -- Detail Categories Components and details shall be designed to satisfy the requirements of their respective detail categories summarized in Table 6.6.1.2.3-1. Where bolt holes are depicted in Table 6.6.1.2.3-1, their fabrication shall conform to the provisions of Article 11.4.8.5 of the AASHTO LRFD Bridge Construction Specifications. Read the entire page →
From page 246... ... 246 The procedures for load-induced fatigue are followed for orthotropic deck design. Although the local structural stress range for certain fatigue details can be caused by distortion of the deck plate, ribs, and floorbeams, research has demonstrated that load-induced fatigue analysis produces a reliable assessment of fatigue performance. Read the entire page →
From page 247... ... 247 Table 6.6.1.2.3-1 -- Detail Categories for Load-Induced Fatigue Description Category Constant A (ksi3) Threshold (ΔF) Read the entire page →
From page 248... ... 248 Table 6.6.1.2.3-1 (continued) -- Detail Categories for Load-Induced Fatigue Description Category Constant A (ksi3) Read the entire page →
From page 249... ... 249 Table 6.6.1.2.3-1 (continued) -- Detail Categories for Load-Induced Fatigue Description Category Constant A (ksi3) Read the entire page →
From page 250... ... 250 Table 6.6.1.2.3-1 (continued) -- Detail Categories for Load-Induced Fatigue Description Category Constant A (ksi3) Read the entire page →
From page 251... ... 251 Table 6.6.1.2.3-1 (continued) -- Detail Categories for Load-Induced Fatigue Description Category Constant A (ksi3) Read the entire page →
From page 252... ... 252 Table 6.6.1.2.3-1 (continued) -- Detail Categories for Load-Induced Fatigue Description Category Constant A (ksi3) Read the entire page →
From page 253... ... 253 Table 6.6.1.2.3-1 (continued) -- Detail Categories for Load-Induced Fatigue Description Category Constant A (ksi3) Read the entire page →
From page 254... ... 254 Table 6.6.1.2.3-1 (continued) -- Detail Categories for Load-Induced Fatigue Description Category Constant A (ksi3) Read the entire page →
From page 255... ... 255 Table 6.6.1.2.3-1 (continued) -- Detail Categories for Load-Induced Fatigue Description Category Constant A (ksi3) Read the entire page →
From page 256... ... 256 Table 6.6.1.2.3-1 (continued) -- Detail Categories for Load-Induced Fatigue Description Category Constant A (ksi3) Read the entire page →
From page 257... ... 257 Table 6.6.1.2.3-1 (continued) -- Detail Categories for Load-Induced Fatigue Description Category Constant A (ksi3) Read the entire page →
From page 258... ... 258 Table 6.6.1.2.5-1 -- Detail Category Constant, A Detail Category Constant, A times 108 (ksi3) Read the entire page →
From page 259... ... 259 Table 6.6.1.2.5-3 -- Constant-Amplitude Fatigue Thresholds Detail Category Threshold (ksi) Read the entire page →

From page 217...

... 217 In Chapter 6, various articles of AASHTO LRFD were identified that would need to be modified to implement the calibrated SLS resulting from this research. This chapter contains the suggested modifications formatted in a form suitable for consideration by the affected technical committees that could be potential AASHTO Highway Subcommittee on Bridges and Structures agenda items.