日照温差在箱梁顶板产生的横向应力实测与分析

发布时间：2019-01-05 21:54

【摘要】：混凝土薄壁箱梁具有良好的结构整体受力性能和跨越能力，20世纪70年代以来，在现代大跨桥梁结构中得到广泛应用。然而，不论是施工阶段还是使用阶段，经常会在这类桥梁顶板中线下缘发现一条或多条纵向裂缝。之前有学者研究表明，造成这种裂缝的主要原因是温度应力和活载作用。温度应力要达到甚至超过活载产生的应力。由于施工阶段的箱梁纵向的预应力筋一般先于横向预应力筋张拉，，所以在纵向预应力筋张拉完毕而横向预应力筋尚未张拉时，泊松效应降低了箱梁顶板下缘的抗拉储备，从而削弱了顶板的横向抗裂性。施工阶段箱梁没有铺装层的隔热作用，日照温差的影响更大。研究施工阶段日照温差作用下箱梁顶板的受力情况对预防顶板开裂具有实际工程意义。本文以陡下大桥为工程背景，通过现场温度测量并结合温度梯度经验公式，拟合得到实际温度梯度，通过现场应力测量得到顶板横向温度应力。应用ANSYS分析软件建模对比了实测拟合温度梯度下以及几种不同规范温度梯度下箱梁顶板下缘的温度应力，分析了箱梁不同截面参数下竖向温度梯度引起的横向温度应力的变化规律，比较了日照温差应力和自重作用对顶板开裂的影响，对施工阶段箱梁顶板开裂的可能区域进行了分析，表明公路钢筋混凝土及预应力混凝土桥涵设计规范(JTG D62-2004)中只给出纵向温度应力的计算公式是不充分的。
[Abstract]:Concrete thin-walled box girder has been widely used in modern long-span bridge structures since 1970s. However, one or more longitudinal cracks are often found at the lower edge of the middle line of the bridge roof, both in construction and in use. Previous studies have shown that the main causes of this crack are the effect of temperature stress and live load. The thermal stress should reach or even exceed the stress generated by live load. Because the longitudinal prestressing tendons of the box girders in the construction stage are usually prior to the transverse prestressing tendons, the Poisson effect reduces the tensile reserve at the lower edge of the roof of the box girders when the longitudinal prestressing tendons are completed and the transverse prestressed tendons have not yet been tensioned. Thus, the transverse crack resistance of the roof is weakened. In the construction stage, the box girder does not have the thermal insulation effect of the surfacing layer, and the effect of sunshine temperature difference is greater. It is of practical engineering significance to study the stress on the roof of box girder under the action of sunshine temperature difference in construction stage. In this paper, the actual temperature gradient is obtained by field temperature measurement and empirical formula of temperature gradient, and the transverse temperature stress of roof is obtained by field stress measurement. In this paper, the temperature stress of box girder roof is modeled and compared by using ANSYS analysis software under the measured fitting temperature gradient and several different code temperature gradients. The variation law of transverse temperature stress caused by vertical temperature gradient under different cross-section parameters of box girder is analyzed, and the effects of sunshine temperature difference stress and gravity on roof cracking are compared. This paper analyzes the possible area of roof cracking of box girder in construction stage, and shows that the calculation formula of longitudinal temperature stress in the design code of reinforced concrete and prestressed concrete bridge and culvert (JTG D62-2004) is insufficient.
【学位授予单位】：湖南科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U441;U448.213

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