Research On Influence Of Reinforcement In Beam And Column And Flare Tube On Local Compression Bearing Capacity Of Concrete

Engineering practice and scientific research in latest years show that there are some problems in the calculation method of local compression bearing capacity in the current Code for Design of Concrete Structures ("the Current Code"for abbreviation) and they need to be improved. According to the requirements of local compression, a large number of indirect reinforcement should be placed in the anchorage zone in the node of the prestressed frame. Which cause that the reinforcement in the node is very dense, so it is difficult to cast concrete compactly, and this will seriously affect the quality and efficiency of construction. However, in the outside of node, the longitudinal-steel in beam and the longitudinal-steel in column as well as the stirrup in node will increase the local compression bearing capacity of concrete. But the influence of the reinforcement has not been taken into account in the calculation formula in the Current Code. In addition, the calculation formula of local compressing in the Current Code is based on the loading tests of anchorage only with plate. It is worth researching that how to choose the duct area when calculating the local compression bearing capacity with flare tube. To solve these problems, two research works are accomplished in this dissertation.(1)In consideration of the problem that the influence of longitudinal-steel in beam, longitudinal-steel in column and stirrup in node on the concrete strength for local compression has not been taken into account in the calculation formula in the Current Code, the idea that the reinforcement which is intersected with anchor plate in the beam and column is regarded as equivalent plate is brought forward. Researches show that the length of longitudinal-steel in beam, longitudinal-steel in column and stirrup in node which is regarded as equivalent plate is three times diameter of the steel bar and the new added local compression area is longitudinal area of this section that the length is three times the diameter of the steel bar. The dissertation has put forward the determining method of local compression area and calculated bottom area for local compression and then the method for calculation of local compression bearing capacity considering the effect of longitudinal-steel and stirrup. In connection with actual projects, the application of calculation formula of local compression bearing capacity using this method has been introduced.(2)The influence of flare tube to the concrete strength for local compression has not been taken into account in the calculation formula in the Current Code. Considering this problem, analysis of selection of duct area when local compression bearing capacity is calculated about the anchorage with flare tube has been made. Researches show that duct area equals to the minimal area of the hole of the flare tube, that is cross sectional area of bellow when local compression bearing capacity is calculated with flare tube. And some advices of acceptance test is given.