陕西省连续箱梁桥底板实测竖向温度梯度研究

Study on Bottom Plate Measured Vertical Temperature Gradient of Continuous Box Beam Bridge in Shaanxi Province

为建立陕西省不同地区连续箱梁桥实测温度梯度场,选取陕北、关中和陕南地区具有代表性的三座连续箱梁桥进行了连续一年的观测,通过对实测数据的拟合,建立了三个地区实测温度梯度模型.研究表明,陕西省三个地区连续刚构箱梁实测竖向最大温差各不相同,按规范中计集混凝土铺装层后计算得到,陕北地区18.6℃、关中地区21.2℃、陕南地区22.9℃,但均小于规范值25℃;与规范规定不同,实测数据显示:箱梁底板存在竖向温差,三个地区底板实测正(负)最大温差分别为3.5℃(-3.1℃)、2.8℃(-2.9℃)、1.5℃(-1.5℃).基于实测温度梯度,建立箱梁合龙段有限元模型,进行实测温度效应分析,结果表明:在负温度梯度中,不考虑底板竖向温度梯度的作用,对于底板的受力将产生不利的影响,偏不安全.建议在进行连续(刚构)箱梁桥设计验算时应综合考虑底板竖向温度梯度的影响.

In order to establish the measured temperature gradient field of continuous box girder bridges in different areas of Shaanxi Province,three representative continuous girder bridges in northern Shaanxi,central Shaanxi and southern Shaanxi were selected for one year continuous observation.By fitting the measured temperature data,three temperature gradient models were established.The results showed that the vertical maximum temperature difference of continuous box girder bridge in three areas in Shaanxi Province was different.According to the specifications set concrete pavement,the maximum temperature of northern region was 18.6℃;the maximum temperature of central Shaanxi was 21.2℃;the maximum temperature of southern Shaanxi was 22.9℃,but were less than the standard value of 25℃.Different from the normative provisions,the measured data show that there was vertical temperature difference in the bottom plate of the box girder,the maximum positive and negative temperature differences of the bottom plate in the three regions were 3.5℃(-3.1℃),2.8℃(-2.9℃)and 1.5℃(-1.5℃).Based on the measured temperature gradient,the finite element model of the box girder closure section was established,and the measured temperature effect was analysed.The results showed that in the negative temperature gradient,not taking into account the effect of vertical temperature gradient of the bottom plate,the force would have a negative impact for bottom plate,impartial security.It was suggested that the vertical temperature gradient of the bottom plate should be considered comprehensively in the design checking of continuous(rigid frame)box girder bridge.