变截面圆端空心桥墩抗震性能目标及性能水准量化

Seismic Performance Target and Performance Level Quantification for Variable-section Round-end Hollow Piers

基于结构性能的抗震设计理论已经被多个国家接受并列入规范中,这些规范对结构的抗震性能目标做出了定义及要求,但对其性能水准的量化尚处于研究阶段。多数研究针对实心墩或等截面桥墩,根据不同延性类别(位移延性、位移角延性及曲率延性等)提出不同的性能水准量化指标,但考虑因素较为单一(性能指标的表达式无法兼顾多种构件设计参数),对变截面圆端空心墩的适用性还有待验证。鉴于变截面圆端空心墩特殊的力学性能(由于墩底存在实心与空心过渡倒角段,导致其墩身曲率分布情况与常见规则桥墩不同,塑性铰的位置和长度可能发生变化,且结构偏柔,一阶振型质量参数系数较低等),基于OpenSees有限元软件,结合材料本构关系及构件承载力-位移曲线,针对该种结构提出了明确的性能水准的定义,并以自定义漂移率(可兼顾构件的位移、曲率、高度、剪跨比)作为性能指标。考虑多种常见桥墩设计参数及其变化范围,通过大量数值模拟结果的回归统计分析,给出该种桥墩在不同设计参数下不同性能水准的相关量化值,并以圆端空心墩拟静力试验结果进行对比分析验证。结果表明,提出的漂移率作为性能指标及其量化值具有一定的可靠性,可作为类似结构研究与计算的参考。

The seismic design theory based on structural performance has been accepted and included in specifications by many countries, and the seismic performance targets of the structure have been defined and required, but the quantification of its performance level is still in the research stage. Most studies have proposed different performance level quantization indicators for solid or equal-section piers according to different ductility categories(displacement ductility, displacement angle ductility and curvature ductility, etc.), but the considerations are relatively single(the expression of performance indicator cannot take into account many design parameters of components), and its applicability to variable-section round-end hollow piers needs to be verified. In view of the special mechanical properties of variable-section round-end hollow piers(due to the existence of solid and hollow transition chamfering at the pier bottom, the curvature distribution of the piers body is different from that of the common regular piers, the position and length of the plastic hinge may change, the structure is flexible, and the mass parameter coefficient of the first mode is low), based on OpenSees software, combining the constitutive relation of material and bearing capacity-displacement curve of components, a clear definition of performance level is proposed for this kind of structure, and the custom drift rate(which can consider displacement, curvature, height and shear-span ratio) is taken as the performance indicator. Considering a variety of common pier design parameters and their variation ranges, through regression statistical analysis on the result of numerous numerical simulations, the relevant quantitative values of different performance levels of this pier with different design parameters are given, which are compared with the quasi-static test result of round ended hollow piers. The result shows that the proposed drift rate is reliable as a performance indicator and its quantized value, which can be used as a reference for similar structure research and calculation.