钢-混凝土组合梁桥的温度梯度作用——作用模式与极值分析

为建立适用于钢-混组合梁桥的竖向温度梯度作用模式和取值方法，对一组合梁节段模型开展超过一年的长期温度测试与有限元数值模拟，以温度场分解得到的竖向线性温差和残余温度作为温度评价指标，根据指标达到极值时的竖向温度分布特征建立适用于组合梁桥的温度梯度模式体系。利用气象站23年的历史气象数据计算组合梁桥的长期温度梯度，采用基于广义帕累托分布(GP分布)的超阈值模型进行温度梯度代表值极值分析。研究结果表明：竖向线性温差和残余温度可反映温度作用在结构产生的次生效应和自生效应，是判断竖向温度梯度模式合理性的有效评价指标；考虑中梁和边梁腹板的日照条件差异，建立了适用于多主梁组合梁桥的竖向温度梯度模式体系，包括了2种升温模式和1种降温模式，对不同铺装厚度和桥面板板厚均有较好的适用性；钢梁形状对各温度梯度模式的影响并不显著，桥面板厚度、沥青铺装厚度对组合梁顶部的温差影响显著，钢表面吸收率则对升温模式1、2中钢梁部分的温差影响显著；在边梁的升温模式2中，钢梁温度渐变段高度与组合梁的悬高比(桥面板悬臂宽度与钢梁高度的比值)有直接关系，当悬高比大于1.51时，钢梁完全处于阴影之中；建立了西安组合梁桥各温度梯度中温差的GP分布模型，计算得到了各温差50年重现期的代表值，通过与中国通规和欧洲规范中的温度梯度模式对比，发现提出的3种温度梯度模式可以更好地包络住组合梁桥中梁和边梁长期运营期间产生的正负线性温差和拉压应力状态，对于中国规范组合梁桥温度作用相关条款的补充具有重要意义。

Temperature Gradient Action of Steel-concrete Composite Girder Bridge: Action Pattern and Extreme Value Analysis

Long-term temperature measurements and finite element simulations were performed on a composite girder segment for more than one year to establish the vertical patterns of temperature gradients and develop a method for measuring values for steel-concrete composite girder bridges. The vertical linear temperature difference and residual temperature were selected as the temperature evaluation indices and then decomposed from the temperature fields. Temperature gradient patterns were systematically established based on the vertical temperature distributions when these evaluation indexes achieved the most unfavorable values. The temperature gradients of the composite girder bridge were calculated using historical meteorological data for 23 years. The super-threshold model based on the generalized Pareto (GP) distribution was adopted to determine the representative values of the temperature gradient. The results show that the vertical linear temperature difference and residual temperature can reflect the secondary and autogenous effects caused by temperature gradient actions; thus, they effectively evaluate the rationality of the vertical temperature gradient patterns. Three temperature gradient patterns were established for multigirder composite girder bridges, considering different sunshine conditions between the interior and exterior girders webs. Three temperature gradient patterns were established for the multigirder composite girder bridges. These temperature gradient patterns, comprising two heating patterns and one cooling pattern, show good applicability to different pavement and concrete slab thicknesses. The shape of the steel girder does not influence the temperature gradient patterns. The pavement thicknesses and concrete slab thickness significantly influence the temperature difference at the top of the composite girder, and the steel absorptivity significantly influence the temperature difference of the steel girder in the heating patterns. In heating pattern 2 of the exterior girder, the height of the variable-temperature section of the steel girder is directly influenced by the cantilever-height ratio of the composite girder. When the cantilever-height ratio exceeds 1.51, the steel girder is completely shadowed. The GP distribution models of each temperature gradient were established for composite girder bridges in Xi'an City, and the corresponding representative value in a 50-year return period was calculated. A comparison of the temperature gradient patterns between the Chinese code and Eurocode shows that the proposed temperature gradient patterns satisfactorily reflects the positive-negative linear temperature difference and tensile-compressive stress state of the interior and exterior girders during the long-term operation period. Thus, these findings are valuable in supplementing the relevant provisions of the temperature action of composite girder bridges in China.