陕西地区混凝土无伸缩缝桥梁的温度作用及其区划

Temperature action and zoning of concrete jointless bridge in Shaanxi

为研究混凝土无缝桥温度作用取值的地域差异性,对一整体式无缝桥开展了长期温度测试,基于实测数据验证有限元温度场模拟方法的准确性;调研陕西省及周边省份46个国家基准气象站1993~2015年气象数据,对其中缺失太阳辐射数据的站点进行了补充,并将气象站日值数据分解为逐时数据用于温度场分析;利用气象数据进行了23年长期温度场模拟,并基于新西兰规范温度梯度模式,进一步通过广义帕累托模型计算了有效温度和温度梯度作用具有50年重现期的代表值;采用空间插值方法绘制了温度作用等值线地图,并对等值线地图进行简化得到了温度作用分区地图;考虑不同梁高和铺装厚度参数对温度作用模式进行了修正,并最后给出一个分区地图的应用案例,计算了陕西各分区内整体桥的跨径总长限值。研究结果表明:陕西地区有效温度分区地图分布趋势与《公路桥涵设计通用规范》(JTG D60—2015)基本吻合,但关中和陕南部分地区取值较规范更为不利,而对于温度梯度顶部温差,陕北和陕南的大部分地区均超过规范统一取值14℃;在梁高小于1.4 m时,不存在新西兰规范温度梯度模式中的等温段,修正后的温度梯度模式能准确反映不同梁高下的温度分布规律;沥青铺装厚度仅对顶部温差影响较大,不同铺装厚度情况下的顶部温差可按线性插值进行修正;整体桥主梁纵向变形量随桥长线性增长,可在自由伸缩变形的基础上通过过引入纵向伸缩量折减系数进行简化计算;桥长可通过考虑升温时的桥台弯曲破坏和降温时的桩低周疲劳破坏进行控制,根据实际合龙温度计算;在提出的3种温度分区中,最优合龙温度下的理论桥长最大值分别为290、240和220 m。

In order to study the regional difference of temperature action of concrete jointless bridge, a long-term temperature field test was carried out for an integral jointless bridge. The accuracy of temperature field FEM(finite element model) was verified based on the recorded data. The meteorological data from 1993 to 2015 were collected from 46 national meteorological stations in Shaanxi Province and surrounding provinces, the missing solar radiation data were supplemented, and the daily data of meteorological stations were decomposed into hourly data for temperature field analysis. The long-term temperature field was simulated with the meteorological data for 23 years, and the representative values of effective temperature and temperature gradient with a 50-year return period were further calculated by the generalized Pareto model based on the New Zealand canonical temperature gradient model. The isoline map of temperature action was drawn by the spatial interpolation method and further simplified as a zoning map of temperature action. The temperature action mode was modified by considering different beam heights and pavement thicknesses, and an application case of zoning map was given to calculate the total span limit of the whole jointless bridge in each zoning of Shaanxi Province. Research results show that the effective temperature zoning map in Shaanxi Province coincides well with the General Specification for Design of Highway Bridges and Culverts(JTG D60—2015), while the values in Guanzhong and parts of Southern Shaanxi are more unfavorable than the specification. However, the top temperature differences of temperature gradient in most areas of Northern Shaanxi and Southern Shaanxi exceed the specification value of 14 ℃. There is no corresponding isothermal section recommended in the New Zealand standard temperature gradient model when the beam height is less than 1.4 m. The modified temperature gradient model can reasonably reveal the temperature distribution patterns with different beam heights. The thickness of asphalt pavement only has a great influence on the top temperature difference, and the difference can be corrected by the linear interpolation under different thicknesses. The longitudinal deformation of main girder of integral jointless bridge increases linearly with the length of the bridge, and its calculation can be simplified by introducing the longitudinal expansion reduction coefficient based on the free expansion deformation. The bridge length can be controlled by the bending failure of the abutment under heating and the low-cycle fatigue failure of the pile under cooling, and calculated according to the actual closing temperature. In the proposed three temperature zones, the maximum theoretical bridge length at the optimal closure temperature is 290, 240 and 220 m, respectively. 4 tabs, 20 figs, 30 refs.