In most seismic design codes, usually two seismic hazard levels are taken into account, for example, Design Earthquake and Maximum Considered Earthquake. Several disastrous earthquakes have proved that seismic safety evaluation may underestimate seismic risks, which would result in serious damage of bridge structures. Therefore, a new higher level of seismic hazard named Very Rare Ground Motion (VRGM for short) is proposed innovatively to be considered in this paper for very important bridges. A novel seismic design method of simply supported girder bridges in the transverse direction for VRGMs is proposed at first. In the proposed method, seismic isolation bearings, tension-only braces and ductile piers are combined to improve the seismic performance and meet seismic requirements of VRGMs. Taking a simply supported girder bridge as a numerical analysis example, the proposed method is compared with two bridge seismic design methods adopted in current seismic codes and its parametric analysis is conducted. It’s shown that the proposed seismic design method can combine the ductility capacities of piers and the functions of seismic isolation bearings and reduce all the concerned structural seismic responses in VRGMs effectively. This work provides an educational demonstration for engineers dealing with similar problems.

在大多数地震设计规范中，通常会考虑两个地震危害等级，例如，“设计地震”和“最大考虑地震”。几次灾难性地震证明，地震安全性评估可能会低估地震风险，这会严重损害桥梁结构。因此，创新性地提出了一种新的更高级别的地震危险等级，称为非常稀有地震动（简称VRGM），可用于非常重要的桥梁。首先提出了一种新型的VRGM简支梁桥横向抗震设计方法。该方法结合了隔震支座，抗拉支架和延性墩，以提高抗震性能并满足VRGM的抗震要求。以一个简支梁桥为数值分析实例，将该方法与目前地震规范中采用的两种桥梁抗震设计方法进行了比较，并对其参数进行了分析。结果表明，所提出的抗震设计方法可以将桥墩的延性承载能力与隔震支座的功能相结合，有效地降低了VRGM中所有相关的结构地震响应。这项工作为处理类似问题的工程师提供了教育上的示范。结果表明，所提出的抗震设计方法可以将桥墩的延性承载能力与隔震支座的功能相结合，有效地降低了VRGM中所有相关的结构地震响应。这项工作为处理类似问题的工程师提供了教育上的示范。结果表明，所提出的抗震设计方法可以将桥墩的延性能力与隔震支座的功能相结合，有效地降低了VRGMs中所有相关的结构地震响应。这项工作为处理类似问题的工程师提供了教育上的示范。