The Study Of Local Pressure Of Open Steel Tube Confined Concrete Column And Iterative Steel Tube Confined Concrete Column

The problem of large concentrated forces acting over limited areas of concrete is one of frequent occurrence in civil engineering design. Past study was most placed emphasis on the distribute stress which is on the bearing surface. With the development of high-building in domestic, the application of Steel Tube Confined Concrete(STCC) and Pile Shut Steel Tube Confined Concrete (PSSTCC) has stood up gradually at present . For sake of the pouring quality at the bottom surface, the cushion has not been carried on the bottom, namely opening. In the case, because of the difference of elastic model between STCC and PSSTCC is great. Some instances will be took into consideration, such as the problem of large concentrated forces acting over limited areas of concrete , the problem of the depth of the STCC which is embeded in the foot. In addition, the degree of the playing bearing capacity is worth thinking .So, tests on 26 specimens and the corresponding non-linear finite element analysis were performed. And some inclusions are the following. (1) The stress on surface is not distribute, and the concentrating phenomenon , which will reduce the bearing capacity of plain concrete , is obvious along the location of steel tube at the foot, and does nothing with the bearing capacity of reinforced concrete. The Chinese code " Concrete Structure Design Code " GB50010-2002 can be kept on using in the latter one . (2) Although the concentrating phenomenon is obvious on the surface, it reduces rapidly with the distance from the surface. In some distance, the form of the distribution of vertical stress is unanimous with that under the distribute stress. (3) The change of thickness of steel tube does nothing with the maximum horizontal stress. And the maximum value occour under surface on the outside of the concrete , which is 20% distance of the length under the surface. (4) The concentrating phenomenon of PSSTCC is alleviated obviously. And the maximum horizontal stress is reduced greatly. (5) The problem of local pressure of PSSTCC can be simplied into the problem the distribute stress. And the bearing area is the area of the whole section of PSSTCC.