The Temperate Crack And Control Techniques Of Ultra-long Concrete Constructions

Present research status about the crack control in ultra-long concrete construction in home and abroad is generalized in the paper, the reasons of crack generation are analyzed, the temperature stress and temperature field theory of ultra-long concrete constructions are introduced. Then, three methods are put forward to solve the crack problem of ultra-long concrete, they are: breathing method, prestresse and later poured band, which are simulated and analyzed through the FEA software —ANSYS.The research contents mainly include: First, the influence of foundation constraint condition to the temperature stress is analyzed, the temperature stress formula of ultra-long concrete anchor plate is deduced, then the influence of length to structure crack can be gotten from the formula. Second, a breathing method is set up to solve the problem of temperature stress in ultra-long concrete constructions. By setting the sliding floor, a breathing system is built up and the temperature stress reduced distinctly. Third, the effect of prestress technique in the control of temperature stress is analyzed, it is simulated and calculated through FEA to get the right way to apply the prestress. Forth, the delay of temperature field and unsteady conduction is considered, the temperature field of ultra-long concrete structure with later poured band is simulated, then temperature stress distribution after casting the concrete is calculated, finally the effect of later poured band to temperature stress of ultra-long structure is analyzed.As the research displayed, utilize two of the three methods at the same time, which can better prevent ultra-long concrete structure from cracking. Moreover, as to the detailed structure design, it should avoid from great variation of structure size, which will result in discontinuation of stiffness. Some conclusions are summarized and the problems what should be studied further are put forward in the end of the dissertation.