研究目的:混凝土构件的芯表最大温差是确定最大温度梯度的关键参数,混凝土构件芯表最大温差受太阳辐射以及气温的影响。太阳辐射强度等数据难以直接测得,但太阳辐射以及气温影响导致的构件周边环境温度可以方便地监测。本文对位于北京的某一混凝土空心柱各壁板温度进行长期监测并统计分析监测数据,提出以构件周边环境温度最大值、环境温度变化幅值及环境温度升温速率计算混凝土空心柱芯表最大温差的预测模型,并对预测模型的准确性进行F检验和T检验。
研究结论:(1)混凝土空心柱各测点温度呈现以24 h为周期的周期性变化规律,靠近外表面的测点温度变化受构件周边环境温度影响明显;(2)不同季节条件下,混凝土空心柱南壁板芯表最大温差及表面开裂风险均大于其余壁板,东侧、西侧及南侧壁板芯表最大温差起伏明显,北侧壁板芯表最大温差起伏较小;(3)一天内,南壁板芯表温差变化与构件周边环境温度变化规律相似且达到峰值的时间相近,芯表温差变化速率与构件周边环境温度升温速率相近;(4)一天内,混凝土空心柱芯表最大温差与构件周边环境温度最大值、环境温度变化幅值、环境温度升温速率的相关性均较大;(5)构建的芯表最大温差预测模型能够较为准确地计算混凝土空心柱壁板芯表最大温差,对确定混凝土空心塔柱温度作用具有参考价值。

Research purposes: The maximum temperature difference between the core and surface of the concrete member is the key parameter to determine the maximum temperature gradient. The maximum temperature difference between the core and surface of the concrete member is affected by solar radiation and air temperature. Data such as solar radiation intensity are difficult to measure directly, but the ambient temperature near the member influenced by the solar radiation and air temperature can be directly measured. The temperature of each wall of concrete hollow column located in Beijing is monitored for a long time and the monitoring data are statistically analyzed. A prediction model for calculating the maximum temperature difference between the core and surface of the concrete hollow column based on the maximum ambient temperature, the amplitude of the ambient temperature change and the heating rate of the ambient temperature near the member is proposed, and the F test and T test are carried out for the accuracy of the prediction model.
Research conclusions:(1) The temperature of each measuring point of the concrete hollow column presents a 24-hour period of periodic change, and the temperature change of the measuring point near the outer surface is obviously affected by the ambient temperature that near the member. (2) Under different seasonal conditions, the maximum temperature difference between the core and surface and surface cracking risk of the south wall of the concrete hollow column is greater than that of the rest of walls, and the maximum temperature difference of the core and surface of the east, west and south walls fluctuates significantly, while the maximum temperature difference of the core and surface of the north wall fluctuates less. (3) In one day, the changes of the temperature difference between the core and surface of the south wall is similar to the changes of the ambient temperature near the member, and the peak times are similar, and the change rate of temperature difference between the core and surface of the south wall is similar to the temperature rises rate of the ambient temperature that neat the member. (4) In one day, the maximum temperature difference between the core and surface of concrete hollow column is highly correlated with the maximum ambient temperature, the amplitude of the ambient temperature change and the heating rate of the ambient temperature near the member. (5) The constructed prediction model can calculate the maximum temperature difference between the core and surface of concrete hollow column more accurately, which has a reference value for determining the temperature effect of the concrete hollow tower column.