大体积混凝土热学参数反分析新方法

基于线性传热理论 ,对大体积混凝土“气温变化 -表层温度响应”进行了研究。将单调变化的环境温度以较小的时间步长分段线性化 ,利用叠加原理 ,提出了混凝土热学参数反分析的新方法。利用 40 0 mm× 40 0 mm×2 2 0 mm混凝土块进行室外模型试验。在给定的临界扰动贡献率下 ,将实测资料区分为有效扰动与无效扰动 ,得到了混凝土的热学参数 ,验证了该方法的可行性。该方法具有测点数量少、测量时间短等优点 ,还可以同时得到导温系数与混凝土 -空气热交换系数 ,特别适合在反馈设计中应用

A new method for back analysis on thermal parameters of mass concrete needs

Traditionally, the thermal parameters for mass concrete by back analysis needs two strict conditions: one is periodically changed with surrounding temperature, another is a huge long measuring time. In order to get the thermal information of mass concrete not long after the concreting started, a quicker method is necessary. Based on the linear conduction theory of mass concrete, the relationship between temperature change of air and the response of concrete is studied. By multi linearizing the temperature process of air, and taking the advantage of superposition, a new method for the back analysis on the thermal parameters of mass concrete is presented. The continuous disturbance of air to concrete is dispersed into a series of independent unit disturbance. The temperature response of concrete to each unit disturbance may decline to a very small percent when measuring time is going on. Then, if a disturbance standard is designed in advance, the effective disturbance and ineffective disturbance of air are distinguished. Only the effective disturbance controls the final temperature of concrete, thus the thermal parameters connoted in the final temperature can be determined by optimization. The concrete specimens shaped in mold were used to carry out the test, which has performed the new method and obtained the thermal diffusivity and thermal exchange coefficient simultaneously. The way put forward needs less testing points and expends less time, so it is valuable in back design of large civil engineering.