混凝土箱体桥梁自控温装置设计与温度分析

Design and Temperature Analysis of Automatic Temperature Control Device for Box Structure of Concrete Bridge

为解决混凝土箱体结构的温度裂纹问题,基于太阳辐射与来自近环境表面低红外辐射之间的能量密度失配,研发出一种可以在白天用于混凝土箱体桥梁表面的自控温装置。该装置采用辐射降温涂层和复合定形相变材料相结合,多层控温的方式,外挂在腹板表面,从外向内依次分为滤波器、反射层、封装层、潜热层和连结层5个部分。以陕西神沙河大桥为例,通过现场实测和理论分析相结合的方法,研究了自控温装置安装前、后混凝土箱体腹板外侧的温度和温度应力。结果表明:自控温装置是一种能够避免太阳辐射等因素导致混凝土箱体表面开裂的有效措施。对未安装自控温装置的箱体,腹板外侧对外界环境温度敏感,温度波动区间较大,最大温度应力较大;对已安装自控温装置的箱体,由于辐射降温涂层反射了部分太阳辐射,以及复合定形相变材料的相态转变向外界环境释放或吸收了部分潜热,腹板外侧温度波动区间较小,最大温度应力较小。

In order to solve the cracking problem of concrete box structure caused by temperature,an automatic temperature control device,which can be used on the surface of concrete box bridge in daytime,was designed based on the energy density mismatch between the solar radiation and the low infrared radiation from the near environment surface.Combining radiation cooling coating with composite shape setting phase change material and adopting multi-layer temperature control mode,the device was hung on the web surface.Besides,it was divided into five parts from the outside to the inside,which were filter,reflecting layer,packaging layer,latent heat layer and connecting layer.Taking Shenshahe bridge in Shaanxi Province as an example,the temperature and temperature stress outside the concrete box web before and after the installation of the automatic temperature control device were analyzed by using the method of field measurement and theoretical analysis.The results show that the automatic temperature control device is effective to avoid the surface cracking of concrete box structure caused by solar radiation and other factors.Specifically for the box without the automatic temperature control device,the outside of the web is highly influenced by the external environment temperature,the temperature fluctuation range is larger and the maximum temperature stress is larger.For the box with the automatic temperature control device,the temperature fluctuation range of the outer side of the web is smaller and the maximum temperature stress is smaller,since the radiation cooling coating reflects part of the solar radiation and the phase transition of the composite shape setting phase change material releases or absorbs part of the latent heat.