Affection Of Construction Joints To Hysteretic Behavior Of Frame Structure

In process of actual construction, reinforced concrete structure usually can not be moulded continuously, so construction joints are left in structures. For a long time, people neglect the effect of construction joints to structures, although there are some experts who have done some researches about this, this problem is still not paid enough attention. In 2008, wenchuan earthquake happened, we found that there were some typical damages to structure which were caused by construction joints. From then on ,we began to pay much attention to it. For some reason, in actual construction, construction joints are set roughly, so they destroy the integrality and continuity of the structure in some degree. That is why we saw so many damages caused by construction joints. But researches about this are very few, although with time goes by people begin to do more researches , those researches are almost be done by the way of experiment, numerical analysis is little. For this reason, this article begins research of construction joints on the base of experiment of two groups of cantilever pillars, one of each group is moulded continuously, the other is with a construction joint. The main work is to find a suitable way to mould construction joints, then apply it to the structure to explore the way of construction joints to effect the ability of structures.During the process of numerical analysis of cantilever pillars, this article is based on the experimental data of two pairs of columns with the same size, material, volume of ties and load, but the only difference is that one of them has construction joint. The model is built by structure analysis software called OpenSees, which is precise in calculation. The most important thing is that it can consider shear influence in fiber model., then provides a necessary condition for modeling of columns with joint. According to the experimental data and phenomenon, zero-length element is used to simulate the column with joint. The way of simulating construction joints is put forward in two sides, one is considering slip of steel bars, the other is considering restoring shear model of columns with construction joint. The two sides are all realized in the special element (zero-length element). Through the contrast of the experimental result and simulating result, the way of simulating columns with construction joint is validated. It can give us some suggestion in our later work.From the contrast of the experiment data and simulating result, we find that the simulating result accords with the experiment result when the way of simulating construction joint which is suggested by this article is used. The contrast result shows that pillars with construction joint is weaker than pillars without in load and rigidity, and because of construction joint, pillars with construction joint have lower ductility. On the base of the previous work, we build up two plane frames, one is with construction joint, the other is without. Through the contrast of numerical results of this two frames, we can get some conclusions about construction joints'effect to the aseismatic ability of frames: on the aspect of load, existence of construction joints affects load level of frames a little, peak load of frame with construction joints is lower than that of frame without construction joints. On the aspect of ductility, ductility of frame with construction joints is lower than that of frame without, so it shows that the existence of construction joints reduces the ductility of frame. On the aspect of rigidity, initial rigidity of frame with construction joints is lower than that of frame without, rigidity degeneration of anterior one is a bit more serious than posterior one. On the aspect of energy dissipation, existence of construction joints affects this a lot, energy dissipation ability of frame with construction joints is much lower than that of frame without. On the aspect of floor drift angle, effect of construction joints is small. On the aspect of distribution of plastic hinges, existence of construction joints dose not change the law of it.