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Thermal Stress Study of Hydration Heat of Thick-Walled High Pier

Author: DengShiGui
Tutor: ZhangLiangLiang
School: Chongqing University
Course: Bridge and Tunnel Engineering
Keywords: Heat of hydration Temperature field Stress field Water Concrete
CLC: U445.7
Type: Master's thesis
Year: 2009
Downloads: 113
Quote: 3
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Abstract

Most of the destruction of the bridge from the cracks. Appear before the computer and the finite element calculation theory, design unreasonable is the bridges destroyed the main reason; theory combined with the computer as well as finite element calculation, improper construction often leads to concrete cracking. Today, most of the concrete cracks appear in the construction phase, or construction method is wrong, or conservation measures are not in place. Concrete from pouring into the subsequent week, the concrete will release a lot of heat of hydration, and its temperature is gradually increased, the heat rate gradually decreases, the gradual increase in concrete with the surrounding air temperature difference. Concrete heat transfer by convection and air, concrete and air temperature difference decreases gradually. Concrete internal temperature of the non-linear distribution, from the inside to the outside, the temperature descending distribution. Concrete due to thermal expansion and contraction role in elevating the temperature will cause the volume will increase and narrow. As the temperature was nonlinear distribution, as well as the role of the concrete internal constraints or external constraints, the volume deformation caused by temperature stress. Based on the heat of hydration of concrete analysis of thick-walled high pier early temperature field, stress field of the law, in order to guide the concrete construction. Here are the main content of this article: 1) This paper start from the solid heat conduction equation describes the analysis of the basic relationship of initial conditions, four types of boundary conditions, the temperature field analysis method, described in detail the currently popular finite element method. 2) thermal analysis, the primary task is to determine the necessary thermodynamic parameters. I field measurement and empirical algorithms to determine the the concrete heat rate, thermal conductivity and convection coefficient. 3) analysis of the measured data and found that the law of the temperature field of the heat of hydration; previously determined the thermodynamic parameters of hydration heat temperature field simulation analysis; measured data and simulation analysis and comparison. 4) from the concrete amount of cement concrete center temperature varieties, three aspects into the mold temperature analysis, the central temperature data; through impoundment conservation, sanding, and affixed to the surface of the plastic foam three insulation measures to get the impact specific data, the temperature difference between the inside and outside use for concrete construction. 5) the concrete hydration thermal analysis process, the material properties are rapidly changing. In this paper, the stress increment method of concrete creep stress. The impoundment conservation not only affect the concrete temperature field, also affect stress field. Through the above analysis, we can get the following conclusions: 1) concrete hydration heat inside the concrete temperature rises above 50 ℃, slowly lower the internal temperature in the convection, surface temperature quickly dropped gradually increasing the temperature difference between inside and outside. 2) reduce the concrete consumption, low heat of hydration of cement, and lower into the mold temperature can effectively reduce the maximum temperature of the concrete center. Water storage and conservation, Shop dry sand, affixed to a plastic foam concrete can effectively reduce the temperature difference between inside and outside. 3) concrete hydration heat temperature stress in about 48 hours after pouring the maximum, and then gradually reduce its reasons for the concrete within 48 hours after casting release a lot of heat of hydration, resulting in volume expansion, surface tensile stress. The impoundment conservation can effectively reduce the temperature difference between inside and outside of concrete and maintain the temperature difference between inside and outside is almost constant after 40 hours, it can effectively reduce the temperature difference between inside and outside of the heat of hydration of concrete stress.

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