Analysis On Mechanism Of The Temperature-shrinkage Cracks Of Cast-in-place Reinforced Concrete Slab And Study On Its Crack Resistance

Varying degree and form of Cracks of cast-in-place reinforced concrete structures appear in the construction or operational phase. While Cast-in-place floor slab be the main form of cover for storey, temperature-shrinkage cracks have become the common quality fault.Therefore, researches on its mechanism, and discusses influencing factors'regularities of crack resistance are very necessary for crack prevention.Base on weather condition of shihezi region, field investigation, theoretical analysis, and numerical simulation have been used to be research techniques in the paper. The characteristics of the temperature-shrinkage cracks of slab have been classified, causes of appearance of cracks have been analyzed, and the regularities of influencing factors have been study, the main research results are as follows:1 Through the medium of field investigation, the main crack forms have been ascertained. The main crack form of construction period is irregular plastic shrinkage cracks, and the main forms of the regular service phase are the temperature-shrinkage cracks, which include longitudinal crack paralleling with the side of the slab and oblique crack at corner of floor slab.2 In the process of theoretical analysis, the compute equations of temperature-shrinkage stress for length wall and anchor plate, which Wang Tie-meng deduces, are used for reference. On the basis of floor slab's boundary condition, the compute equations of temperature-shrinkage stress for cast-in-place reinforced concrete slab have been derived. According to the equations, the mechanisms of longitudinal crack and oblique crack at corner of floor slab have been analyzed.3 By the method of numerical simulation, the whole floor slab model for masonry structure has been built up under its own boundary condition. Cracks of the most unfavoured state for both construction and regular service phase have been simulated, the main developing phase of cracks has been ascertained, and the results of field investigation and theoretical analysis have been verified.4 Both numerical simulation and field experiment have been adopted to study on the floor slab of single room. The regularities of influencing factors that are consist of temperature difference, shrinkage, floor slab thickness, constraint rigidity, and reinforcing bars have been analyzed.