Proposed Modification to AASHTO Cross-Frame Analysis and Design (2021) / Chapter Skim
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Pages 134-142
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From page 134... ...
134 Conclusions and Suggested Research Up until the 1990s, specifications included a spacing limit that effectively standardized the design of cross-frames. AASHTO LRFD Specifications have since eliminated a spacing limit for straight bridges and instead require the design to be based on a rational analysis.
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Conclusions and Suggested Research 135 synthesized from the "Major Outcomes" sections in Chapter 3, are then provided to address each question individually. Proposed changes to the corresponding AASHTO LRFD Articles are subsequently presented in Section 4.2 based on the commentary herein.
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136 Proposed Modification to AASHTO Cross-Frame Analysis and Design [Fatigue loading – Article 6.7.4.2] What is the influence of composite bridge geometry (e.g., support skew, horizontal curvature)
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Conclusions and Suggested Research 137 the system. The stiffness modification approach accounts for these limitations by adjusting the axial stiffness of the cross-frame members in the analysis model.
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138 Proposed Modification to AASHTO Cross-Frame Analysis and Design post processing (e.g., considering various shear force distributions in the design of X-frame diagonals or considering the contributions of the concrete deck when evaluating grillage model results similar to Figure 2-17)
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Conclusions and Suggested Research 139 In terms of organization, each specific AASHTO LRFD Article is listed in italicized font herein followed by bulleted items that expound on the proposed modifications. Articles 3.4.1 and 3.4.5 (proposed)
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140 Proposed Modification to AASHTO Cross-Frame Analysis and Design Article 4.6.3.3.4a (proposed) • For 2D modeling of cross-frames, the proposed postprocessing tools that improve the accuracy of the force predictions are introduced with figures, as are analysis strategies that consider the transverse stiffness effects of the concrete deck in grillage-type models.
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Conclusions and Suggested Research 141 connectivity index limits established previously (Ic > 1, Is > 0.15, or Ic > 0.5 and Is > 0.1) are introduced in the commentary language to expound on the minimum design considerations in this article.
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142 Proposed Modification to AASHTO Cross-Frame Analysis and Design 4.3 Future Research Needs Although this project significantly advances cross-frame analysis and design practices in a wide range of areas, there are a number of related studies that merit additional investigation. These additional research topics are identified below.
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