钢筋混凝土桥梁抗震性能目标优化决策

Optimization of seismic performance objectives for reinforced concrete bridges

国内外对过去桥梁震害调查表明,桥墩的破坏是桥梁未来的主要震害。以桥墩在地震灾害的破坏程度为依据将桥梁性能水平划分为五级,并选取桥墩的墩顶漂移率为量化指标,建立了"桥墩破坏程度-桥梁性能水平-墩顶漂移率"之间的对应关系。该划分细化和量化了现行桥梁抗震设计规范规定的三级性能水平,为设计人员和业主提供更多选择,使桥梁抗震设计更加灵活。同时根据最优设防烈度原则与地震危险性分析相结合,建立了基于"投资-效益"准则的RC桥梁全寿命总费用模型。该模型将抗震性能目标的确定问题转化为以桥梁全寿命总费用函数为最小的桥梁优化设计问题,为基于性能的桥梁抗震设计提供了简单、有效的计算方法。

According to the surveys of seismic hazard of both foreign and domestic bridge,it is concluded that the failure of bridge piers is the primary seismic hazard in future.Based on the level of seismic failure of piers in earthquake the bridge performance level is divided into five grades manually quantified by the top drift ratio of bridge piers,and one kind of relationship among failure level of pier,bridge performance level and top drift ratio of pier is established.The five grades quantify the three stages performance regulated by the current bridge seismic design code,which provides more options for bridge designers and bridge owners and also creates a more flexible bridge seismic design.A total lifetime and total cost model for RC bridge is established on the basis of the principle of'invest-benefit'according to the optimal fortification intensity combining with the earthquake hazard analysis.The model has transformed the problem from how to determine the seismic performance objective of the bridge into how to make an of optimal design for the bridge in which the value of the total cost function of the whole life of bridges is the minimum.A simple,efficient calculation method is proposed to achieve the performance based seismic design.