Study On The Bearing Behavior Of Space Frame Structure Based On Foundation’s Unequal Settlement

There is some collapsible loess foundation and foundation of mountainous area inShandong area.In particular, the soil located in the Yellow River Delta belongs to special soil,which has big deformation, uneven distribution and low shear strength.Designers oftenincrease the safety factor or use more conservative design idea in the process of design. Itobviously increases the cost, and there still exist cracks in the upper structure caused by theuneven settlement of foundation. In addition, although the various structures emerge inendlessly, the frame structure is still visible everywhere in reality. Therefore, it is verynecessary to study the mechanical characteristics of frame structure based on the unevensettlement of foundation. The subject has important social and economic significance, and italso has important guiding significance for structural strengthening design.Model experiments of space frame structure have been carried out in this paper, which isbased on uneven settlement of foundation. Test model are two groups of single-story spaceframe structure, whose long stories is three and transverse spans is one. One group is used tosimulate the settlement of lateral column, and the other group is used to simulate thesettlement of middle column. Through comparing termination of side column settlementwith termination of middle column settlement,(the settling of middle column is84mm; thesettling of side column is97mm), it is found that the influence of upper structure whenmiddle column occurring settlement is more serious than when side column occurringsettlement. Settlement occurring, the part of the in great influence of the upper structure is thebeam which linked to settling column, and the column adjacent to settlement column. Beforethe concrete cracking, although there is a settlement, no obvious phenomenon of internalforce redistribution shows.Once the concrete cracking, beams which connected withsettlement column will have complex internal force redistribution. For the column adjacent tosettlement column, its side back to settling column is always under tension, and its side in theface of subsidence column is always under pressure. The first tensile fracture of columnoccurs on the column which is closest to settling column and it is located on the side back to settling column.A program is designed with a frame got out from the space framework. Foundation in theprogram is regarded as the fixed end. The fixed end is given one displacement to simulate theuneven foundation deformation.The program is based on matrix displacement method, usingFortran language, and used for calculation of fixed-end nodal displacement and force whenoccure uneven settlement. Use VB calling Fortran computer program to make visual interface.Based on the test models and program results, the feasibility of program is proved. It is foundthat the place where has a larger internal force in the program is where cracks in the modeltest.