公路桥梁基于概率的实用抗震性能设计框架

来源期刊:中南大学学报(自然科学版)2015年第9期

论文作者:卓卫东 杨宁 曾武华

文章页码:3468 - 3475

关键词:公路桥梁;抗震性能设计;概率方法;需求-能力系数;框架

Key words:highway bridge; performance-based seismic design; probabilistic method; demand-capacity factors; framework

摘    要:针对公路桥梁提出实用的基于概率的抗震性能设计框架。在该框架中,针对我国现行规范中同一地震区不同抗震设防类别桥梁遭遇的地震危险性不一致的问题,建议设计基准期统一取为100 a,取超越概率分别为86%,19%,10%和4%的4级设计地震动水平;考虑桥梁震后预期将发挥的使用功能,将其抗震性能水平按正常通行、有限通行、应急通行和禁止通行等功能要求相应地划分为4个等级;抗震性能目标规定为在给定设计地震动水平下结构超过规定的抗震性能水平的条件概率,以期解决我国公路桥梁的抗震设防目标长期没有规定预期的可靠度的问题;采用一次二阶矩法,建立基于需求-能力系数的抗震性能设计的极限状态方程,该方程同时考虑结构地震需求和抗震能力的不确定性。按照本文所提出的设计框架,结合设计算例演示其设计过程。研究结果表明:本文所提出的设计框架可实际应用于公路桥梁基于概率的抗震性能设计。

Abstract: A practical framework of seismic design based on probability and performance for highway bridges was proposed. In the framework, four earthquake design levels were recommended in terms of the exceeding probability of 86%, 19%, 10% and 4% in 100 years, to solve the inconsistency of seismic hazard for highway bridges with different seismic fortification classification at the same earthquake zone in current Chinese guidelines for seismic design of highway bridges. Four seismic performance levels were proposed, i.e. immediately operational, limited operational, emergency traffic only, and closed to traffic, respectively, according to the expected functional requirements of highway bridges after an earthquake shock. The seismic performance objective was defined as the conditional probability of exceeding a specified performance level at the given earthquake design level, to solve the problem that the reliabilities of seismic fortification goals of highway bridges had not been specified. The first order second moment method was used to derive the limit state equation of seismic design based on performance for highway bridges, in which both demand and capacity factors were used to explain the uncertainty in the seismic demand and capacity. On the basis of the proposed framework, the design procedure was demonstrated by an example highway girder bridge. The results show that the proposed framework can be practically applied to seismic design based on probability and performance for highway bridges.

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