Analysis Of Cracks In Cast-in-place Beam Slab Structures

With the rapid development of our country’s economy, civil engineering construction has been advancing by leaps and bounds, and cast-in-place reinforced concrete structure is becoming more and more mature. Some practical engineering problems, however, still occurs to such structure, such as cracking. A lot of experiments have shown that hydration heat and temperature fluctuation are the main factors affecting the cracks. But in normal design, only the dead load, live load, wind load, snow load and earthquake action are considered, and the influence of temperature, shrinkage and creep are often neglected. The current Chinese Code, "Design of Concrete Structures"(GB50010-2010), points out that the effect of indirect actions on a concrete structure, such as creep and temperature changes, could jeopardize the safety or normal use of the structure. To ensure the serviceability, safety and durability of a building structure, cracks with excessive width should be prevented. This paper, therefore, mainly analyzes effect of temperature, shrinkage and creep on the crack width in an actual project, a cast-in-place beam slab structure. The research mainly includes the followings:1.Based on the existing research, the calculation theory of crack width and the significance of the research on the cast-in-place concrete beams and slab cracks were summarized. Introductions were mainly given to the concept of concrete cracks, their pattens, mechanism and control method. The analysis was mainly conducted on the effect of temperature, shrinkage and creep on concrete cracks.2. With finite element analysis software, ABAQUS, the effect of temperature transfer process and temperature difference on the tensile stress in the bottom fibers of a concrete beam was analyzed, and the crack width was determine in terms of stress in concrete. The damage degree of the concrete beam was analyzed with concrete plastic damage module.3. By using the construction phase module in finite element analysis software, SAP2000, a real cost-in-place concrete beam slab project was analyzed to investigate the effect of difference in temperature, shrinkage and creep on crack width of the structure. The crack widths calculated with this method were compared with those measured at the site, indicating the reliability of the method.4.The method for the finite element simulation get the value of internal force of cast in situ beam and slab, according to the concrete specification formula calculated specific crack values and compare crack width of crack width of the measured value and the calculated value, and made a number of quantitative results, provide a reference for the future to solve crack problems of the project.