Study On The Rigidity Of The Basement's Top Slab And Its Effect To The High-Rise Building's Performance

The basement is an important transition part between the superstructure and the infrastructure of high buildings. Therefore, the top slab of the basement is one of the main components connecting the superstructure and the basement. It is significant to investigate the effect of the top slab's rigidity of the basement to the performance of the superstructure. This paper have studied the effect of the top slab's rigidity of the basement to the structural capability of tall buildings by making use of the Finite Element Method, and the investigations mainly include three aspects as follows:â‘ Analysed the rigid requirement of the floor. Investigated the factors and regulations that affect the rigidity of the floor through the process that analysed the variation of the internal force and the displacement of the floor under the hypothesis of rigidity and elasticity respectively.â‘¡Analysed the effect of the top slab's rigidity of the basement to the structural capability of tall buildings. Studied the tall buildings'requirement to the top slab's rigidity of the basement through analyzing and comparing the influence of the variation of the top slab's rigidity of the basement on the dynamic characters, the deformation and the internal force of the whole structure.â‘¢Analysed the rigid requirement of the basement's top slab which is usually regarded as the superstructure's build-in position. Analysed and compared the superstructure's dynamic characters, deformation and internal force using the whole structural model including the basement and the apart structural model taking the basement's top slab as the build-in position respectively, and then analysed the rigid requirement of the basement's top slab.From this text, we can acquire conclusion as following:â‘ About the rigid of the basement's top slab1) The rigidity elements about the top slab of the basement include autologous elements consisting of the slab's thickness, the ledger's interval, openings'ratio of slabs and extrinsic elements consisting of the structure's form, space's layout and so on. When the extrinsic elements are determinate, the influence of the floor rigidity is different, and the thickness and ratio is more obvious than the ledger. The number and layout of the ledgers are not obvious to the influence of the rigidity elements about the top slab of the basement. 2) We can know when the thickness increase, the outputs of calculating slab's elasticity and rigidity vary little. When the thickness is greater than 180mm,the difference between these two results is less than 10 percents, and we can calculate it by rigidity assumption if the difference goes gently.3) The analysis indicate when the number of the slabs'openings increase, the outputs of calculating slab's elasticity and rigidity vary more. If the openings'ratio reach 30 percents, the difference between these two results will break, that is the rigidity of slabs abates obviously, so we can not calculate the force and shift by rigidity assumption.â‘¡The influence about the rigidity of the basement's slabs relating to the performance of the upper structure1) With the rigidity of the basement's slabs varying, the basic period, the top shift and the shift between the floor are not influenced obviously, but have its regulars. When the rigidity increase, both of the basic period and the top shift decrease.2) With the rigidity of the basement's slabs varying, the inner force of the upper structure varies obviously, but influence others'floors little.â‘¢Relating to the stiff requirement when the top slab of the basement is the upper partial fixing1) If the top slab of the basement is the upper partial fixing, I suggest that the openings'ratio be less than or equal to 30 percents except for according with the norm.2) If the top slab of the basement is the upper partial fixing, the basic period and the top shift about will diminish but be a little changed comparing to the whole body.3) If the top slab of the basement is the upper partial fixing, the inner force about the bottom columns which locate in the upper structure divided has more changes comparing to the whole body. When calculating, we need more study to analyse the model about the lateral rigidity's variety and the inner force's adjustment ,but we must accord to the fact.