Effect of Vertical Accelerations on the Seismic Response of Highway Bridges

9416525 Breen本项目的主要目标是评估垂直地面加速度与水平运动分量相结合时对公路桥梁地震反应的潜在影响。要检查的影响是桥墩和大梁的应力，或在有非弹性作用时的最大延性要求，以及大梁底座的潜在滑移和永久位移。将建议在桥梁设计规范中纳入适当的规定，以便在抗震设计中考虑到这些规定。将对简化的公路桥梁模型进行一系列参数研究，首先假设完全线性行为，然后考虑与承重垫层行为相关的非线性以及梁端滑动或上浮的可能性，最后包括梁和桥墩中非线性材料行为的可能性。将使用二维、平面内模型和更有限的范围内的三维模型。参数研究将与来自北岭地区的一些选定桥梁的分析相辅相成，以将理论预测与观察到的行为模式和报告的损坏进行比较。设计建议将在咨询桥梁设计师和参与代码编写过程的工程师后提出。这项研究预计将有助于更好地了解垂直地面加速度的潜在影响，以及在什么情况下这些影响可能变得重要并应在设计中考虑在内。如果结果表明应对现行桥梁设计规范进行修订，以提高震中地区公路桥梁的安全性和可靠性，那么工程的结果将对抗震设计产生重大影响。这是一个北岭地震项目。***

9416525 Breen The main objective of this project is the evaluation of the potential effects of vertical ground accelerations, when combined with the horizontal components of motion, on the seismic response of highway bridges. The effects to be examined are the stresses in the piers and girders or the maximum ductility requirements if there is inelastic action, and the potential slippage and permanent displacements at the seats of the girders. Recommendations will be made to incorporate appropriate provisions in bridge design codes to account for them in the seismic design. A series of parametric studies will be conducted on simplified models of highway bridges, assuming first completely linear behavior, incorporating next the nonlinearity associated with the behavior of the bearing pads and the possibility of sliding or uplift of the girders' ends, and including finally the possibility of nonlinear material behavior in the girders and piers. Two-dimensional, in-plane, models and t a more limited extent with three-dimensional models will be used. The parametric studies will be complemented with the analyses of some selected bridges from the Northridge area to compare the theoretical predictions with the observed patterns of behavior and reported damage. Design recommendations will be made in consultation with bridge designers and engineers involved in the code writing process. This study is expected to contribute to a better understanding of the potential effects of vertical ground acceleration and of the conditions under which these effects may become important and should be accounted for in the design. If the results were to indicate that revisions should be made in the present bridge design codes to improve the safety and reliability of highway bridges in the epicentral area, the outcome of the project would have a significant impact on the seismic design. This is a Northridge Earthquake project. ***