Analysis And Control Of Temperature Shrinkage Cracks In Cast-in-place Concrete Floor Slabs Of Steel Structure Residences

Steel frames structures are often used in steel residential building,and the floor slabs are often cast-in-place concrete slab or laminated concrete slabs.Due to the large difference in material properties between the steel frame and concrete slab,the floor slabs deforms uncoordinated under the effect of temperature contraction,which may lead to cracks in the concrete slabs and affect the normal use of the structures.Therefore,it is of strong theoretical and engineering practical significance to study cracks and control measures of cracks in cast-inplace concrete slabs under the effect of temperature shrinkage in steel residential buildings,since it can to ensure the construction quality of assembly steel residential buildings.This paper takes the cracking problem of a cast-in-place floor slab in a highrise steel residential building as the research background,and analyzes its cracks under the effect of temperature shrinkage by combining the results of field inspection and measurement.The specific research work is as follows.(1)The basic theory of temperature effect is introduced,according to the type and characteristics of the ambient temperature.The seasonal temperature difference is used to reflect the temperature variation of the structure.In order to consider the effect of concrete shrinkage and creep on temperature action,a concrete shrinkage calculation model is selected and the discount factor of temperature difference is determined considering the concrete creep.(2)The numerical simulation of the whole structure is carried out by using two methods: one-time loading of the whole structure and layered loading of the construction stage.The longitudinal and transverse deformation patterns of the floor slab under the effect of temperature shrinkage and the stress distribution of the concrete floor slabs are obtained.The results of the two methods are compared with the actual measured results,it is concluded that the results of the layered loading in the construction stage is more consistent with the actual measurement results of the project than that of the overall one-time loading.The effect of setting post-cast zone and construction joints on temperature shrinkage cracks of cast-in-place concrete floor slabs during construction is compared and analyzed,and the methods of controlling temperature shrinkage cracks from the perspective of construction technology are proposed.(3)Numerical simulations of the steel beam-cast-in-place concrete floor slabs are conducted to consider the temperature response of the structure temperature shrinkage load,and the stress distribution of the concrete floor slab,headed studs,steel beams and distributed steel bars and the distribution pattern of temperature cracks in the cast-in-place concrete floor slabs are analyzed.(4)Parametric analysis is carried out on the control of temperature shrinkage cracks of the steel beam-cast-in-place concrete floor slab.The parameters include the concrete cover thickness,diameter and spacing distance of distributed reinforcements in the floor slab,spacing distance and diameter of the headed studs and setting temperature steel bars in the concrete slab.Based on the analysis results,measures of controlling cracks are proposed from the design perspective.