The Detection And Evaluation Of A Library Building And The Analysis And Reinforcement Of The Cantilever Beams With Cracks

Reinforced concrete structures have more advantages than steel structures, wood structures and masonry structures. For example reinforced concrete structures perform much better in mechanical property, durability and fire resistance. Moreover, reinforced concrete structures are more convenient in getting raw materials. Therefore, the type of reinforced concrete structures is used most widely. However, reinfoeced concrete structures crack easily, and their dead load is very heavy. So working with cracks is the normality of the reinforced concrete structures, and the reasons are always complicated.In this paper a library building was used as an example. We detected the loads of the concrete, the size of the components, the number of the reinforcement, the width of the cracks and the deformation of the cantilever beams. Then we found that the main problem was that there were too many cracks of the cantilever beams in the third floor to the ninth floor. The cracks mainly distributed near the fixed end of the cantilever beams, and they were typical flexural-shear cracks. Finally, according to the detection results, the library’s security level was rated as Dsu grade, and the risk level as C grade.Based on the detection results, we can found that the main reasons for the cracks might be insufficient reinforcement, removing the formwork too early or the overloaded construction loads. We thought that the thermal expansion of the exterior wall had the influence on the cracks. After analyzing with some computational analysis software, we found that what we speculated were all right.Finally, according to the detection results and analysis results, this paper came up with three kinds of reinforcement methods which included increasing steel tie rods, enlarging the size of sections and pasting steel plate. By comparison between this three reinforcement methods, we decided to combine the two methods incresing steel tie rods and pasting steel plates to reinforce the cantilever beams.