桥梁结构日照温差二次力及温度应力计算方法研究

Study of the method for calculation of the thermal stress and secondary force of bridge structure by solar radiation

根据等效线性化原则,借助一般有限元程序分析预应力混凝土桥梁的非线性日照温差二次力及温度应力;针对两种非线性温度梯度模式及具有不同顶、底板厚度的一般箱梁桥,推导了等效线性化后的特征参数计算公式。对洺河桥预应力混凝土四跨箱形连续梁的非线性日照温差温度应力计算表明:中国现行公路桥规中规定的日照温度梯度模式是偏于不安全的,由日照温差产生的连续梁跨中附近截面下缘拉应力较大,它与预加力等产生的次应力组合会使截面抗裂性降低,设计时应充分重视。

By using the principles of equivalent linearization, the nonlinear thermal stress and secondary force of prestressed concrete bridge by solar radiation are analysed with the help of general finite element programs. The formula of characteristic coefficient for equivalent linearization is derived for two kinds of thermal gradient modes and general box girders with different depths of top and bottom flanges. As a numerical example, the four-span prestressed concrete continuous box girder of Minghe Bridge is provided to calculate and analyze the thermal stress and secondary force by nonlinear thermal gradient. The results show that the mode of thermal gradient in present code of highway bridge tends to be unsafe. The tensile stress produced by nonlinear thermal gradient is large in the lower part of the cross-section near middle span. The thermal stress together with secondary stress by prestressed force,may reduce the performance of anti-cracking. It should be treated seriously in design.