Thin-walled Cabinets Mold Poured Hollow Raft Foundation Stress Analysis And Design Method

The cast-in-situ reinforced concrete hollow structure is complied with our country's basic national policy of sustainable development, and it is a kind of new-style structure that is developed with the advent of new building materials and new construction technology. The cast-in-situ concrete hollow raft foundation is a new type foundation system in which the lightweight filling materials such as tube fillers and box fillers are laid as internal mold. It has application prospect in multi-storey buildings for its advantages: reducing concrete amount, abating volume contraction and heat of hydration in solidification process of concrete, and decreasing temperature cracks and shrinkage cracks. At present the biggest weakness in application is the stress property analysis in design of the cast-in-situ concrete hollow raft foundation.After summarizing the researching works of earlier scholar, the thesis accomplished the main subjects as follows.1 The cast-in-situ concrete hollow floor system and raft foundation system used widely in the factual engineering are summarized comprehensively so as to put forward the plate type thin-wall core box cast-in-situ reinforced concrete hollow raft foundation system , and analyzes its superiority.2 The stress properties of solid and hollow raft foundation under the ideal constraint condition are studied in this thesis by using finite element method ANSYS. The result of analysis shows that:1) The stress performance of hollow and solid raft foundation is similar. The distribution of stresses, displacement, and reaction of spring on hollow raft foundation are similar to the solid raft foundation . The cavity in the hollow raft foundation leads to the decrease of flexural rigidity. It has the phenomenon of stress concentration at the intersection of hollow box and solid rib, and the deflection increases slightly.2) The moment distribution in interior panel, edge panel and comer panel are analyzed. The result shows that the distribution of section moment and strip moment of the hollow raft foundation is close to the solid raft foundation. And the moment shift to the support saddle.3) The enhancement of concrete intensity can improve the stress property of raft foundation , and reduce uneven settlement. The thesis proposed that the concrete intensity ranks between C30-C40 is suitable.4) The enhancement of coefficient of subgrade reaction can increase the stiffness of ground, and it has advantage of reducing uneven settlement.3 According to the specify of related code and specification in our country, this paper gives some suggestions about design of the plate type thin-wall core box cast-in-situ reinforced concrete hollow raft foundation, and proposes some special measures in construction. Finally, one simple raft foundation is analyzed by using PKPM which is an engineering design software, and the calculation results of PKPM are compared with the analysis results of ANSYS, and also revision is carried on. Thus it provides design reference to the common designers.