【正文】 ability of drawing very low, it is apt to present the weak position of the crack. Among armored concrete , draw stress to undertake by reinforcing bar mainly , concrete bear stress of keeping just. Or reinforcing bar mix if edge position gone to to congeal present the stress of drawing in the structure in plain concrete, must rely on the concrete oneself to bear . Require to avoid the stress of drawing or only very small stress of drawing appears of the the general design. But the concrete is cooled from maximum temperature to the steady temperature of operating period in constructing, often cause sizable to draw the stress within the concrete. The temperature stress can exceed other outsides and load the stresses caused sometimes, know change law , temperature of stress for carry on reasonable structural design and construct extremely important.
Analysis of 2 temperature stresses Can be divided into following three stages according to the forming process of the temperature stress: (1)It is early: Build concrete is it is it over basically to send out heat to cement to begin , generally one one day by oneself. Two characteristics at this stage, first, the cement emits a large amount of heat of hydration, second , mix and congeal the changing sharply of elastic model quantity. Because of the change of elastic model quantity , form the remaining stress in the concrete in this period. (2)Middle period: Up till the concrete is cooled until stability temperature from cement send out heat function basically when expiring, in this period, the temperature stress is mainly because the cooling of the concrete and external temperature change cause, these stresses and remnants stresses that is formed in early days are superposed , mix and congeal the elastic mould amount that goes to and does not change much during this period. (3)Later period: Operation period after the plete cooling of concrete. Temperature stress whether external temperature change cause mainly, these stresses and first two kinds of remnants stresseses are changed and added . Can be divided into two kinds according to the reason why the temperature stress causes: (1)Spontaneous stress: There are not any restraint or totally static structure at the border, if inside temperature is nonlinear distribution, temperature stress appearing because structure restrains from each other. For example, the body of mound of the bridge, the physical dimension is relatively large, surface temperature is low when the concrete is cooled, inside temperature is high, present the stress of drawing on the surface, present the stress of pressing in the middle. (2)Restrain the stress: All of the structure ones or it restrain external one some border,can39。Discuss the construction temperature and crack of the concrete lightlyBy G. K. Kululanga, W. Kuotcha, R. McCaffer, Member, ASCE, and F. EdumFotwe ,The American Society of Civil EngineersThe summary , In order to prevent the owners of the concrete work of claims, we must do a good job in the construction process in the temperature and crack control,through observation live for many years, through consulting the monograph about stress within the concrete, explain to concrete temperature reason , onthespot concrete control and measure , prevention of crack of temperature that crack produce. Keyword Concrete Temperature stress Crack Control 1. The concrete occupies the important position in modern engineering construction. But today, the crack of the concrete is paratively general, the cracks are nearly omnipresent in the science of bridge building. Though we take various kinds of measures in constructing, careful, but the crack still occurs now and then. Tracing it to its cause, it is one of them inpletely that our change to concrete temperature stress pays attention to. In the large volume concrete, temperature stress and temperature control are significant. This is mainly because of the reason of two respects. First of all, concrete often appear the temperature crack in not constructing, influence the globality and durability of the structure. Secondly, in the course of operating, the temperature change has remarkable influence that can39。s shoulder or back limit when draw out of shape to have *104 only , is it carry on one39。 (3)Reduce the thickness of building while building the concrete on hot day, utilize and build the aspect to dispel the heat。 The measure of improving condition of restraining is: (1)Divide and sew and divide one rationally 。s best. 3)Prevent the old concrete subcooling , in order to reduce the restraint among the old and new concrete. The early maintenance of the concrete, the main purpose lies in keeping the suitable warm and humid condition , in order to get the result of two respects, on the other hand make the concrete avoid the invasion and attack of the unfavorable and warm , humidity out of shape, the ones that prevent from harmfully are cold to contract and do to contract. On one hand make cement water function go on smoothly , is in the hope of reaching the intensity designed and resisting the ability of splitting. The suitable warm damp condition is interrelated. Mix warm keeping measure paid to congeal often protect wet results too. Analyse , water concrete include moisture can meet demand , cement of water have enough and to spare newly theoretically. But because the reason of evaporating etc. often causes losses of the moisture, thus postpone or hinder water of the cement from, the surface concrete receives this kind of adverse effect easiestly and directly. Key period when maintained in initial a few days after so the concrete is built, should pay attention to conscientiously in constructing. Conclusions Construction temperature and relation of crack in concrete the above carry on preliminary discussion of theory and practice, though the academia has different theories to origin cause of formation and puting