The Study About Fortifications For Column-beam-wall-stairs Structure System Of Frame-shear Wall Structure

The stairs are not only the vertical transportation channel in a building, but also the important way for people to evacuate and escape in earthquake. During WenChuan earthquake, many stairs inside buildings suffered seriously, the damage phenomenon including the broken of staircase plate, the destruction of corner column and the collapse of the filler wall at staircases. Among the various buildings which the stairs are damaged in the earthquake, the frame structure building is the most prominent. Compared with the serious damage of the pure frame structure building stairs (especially the bottom), the damage of the stairs in the frame-shear wall structure buildings is not that serious overall, but also not rare. The primary purpose of seismic design in buildings is to protect the life safety of people, as the stairs should be the "safety island" in buildings which allows people to escape during the earthquake. The stairs should not be the first destroyed one, whether in the frame structure building or other structure building.According to the ideas and control criterion of the multiple fortifications, this paper uses finite element software Midas Gen8.0and certain conceptual analysis, and studies the action of earthquake seismic line by applying the Pushover method of static force elastic-plasticity to three structure models:the frame-shear wall model (A-1), the frame-shear wall and stairs model (A-2) and the frame-shear wall and stairs model (B-2). The study is to exam the yield mechanism of stair system and the order of the plastic hinge, especially for the destruction of the stairs. From that we will know whether the staircase can be the first seismic line, and then make the exact evaluation on the whole performance of structure seismic.The affection of staircase cannot be ignored. In the situation when the stairs are in horizontal earthquake transfer motion, the load-carrying capability of seismic frame wall at the bottom is obviously different from the situation when the stairs are not in the motion. As the stairs bear quite a bit of seismic action and stair components are brittle without proper yield mechanism, it firstly becomes the weak link of the whole system. So the stairs cannot be the "safety island". The whole system doesn’t present the desired reasonable yield mechanism which only yield at some proper positions in the frame beam, column and wall.Aim at the damage of the structure and staircase, some suggestions are proposed in this paper. Half slide of stairs is both simple and efficient. This method makes the stairs do not participate in horizontal earthquake transfer motion by adjusting the constraints in the structure force system, and decorates multiple fortifications of structure reasonably, which makes the stair a "safety island".