Research And Design Of Raft Foundation In Multi-storey Building Based On Interaction Method In The Soft Soil

Atpresent, superstructure and foundationare consider independently inthedesign of building, the superstructure was consider as no stiffness, thefoundation is consider as the fixed support of superstructure, then the internalforce in superstructure and the reaction in foundation under the load is beingsolved, internal force in foundation under the reaction force in the method ofbeam on elastic foundation is also being solved. The conventional designmethod of the above-mentioned only considered the interaction of foundationand foundation, neglecting the constraint function of upper part structure to thefoundation,causing bending moment of foundation and longitudinal bending tobe greatly, causing the foundation design to be conservatively and the creationwaste; at the same time, we did not consider that the secondary stress ofcausation of the differential settlement to the superstructure, so some parts insuperstructure may unsafe,evenmore there will be some engineering accident.Only consider the interaction function between foundation-raft-superstructure,the real compatible condition of the building and the foundation can bereflected.Therefore, there are some questions in the conventional design method, theinteraction design function problem of foundation-raft-superstructure inengineeringpracticeexistsobjectivelyandshouldbestudiedandapplied.The conventional design method and the interaction design method aredifferent. Conventional design methods first isolated from the superstructure,usedtosubstitutethefixedsupportbaseforsoil foundation,solveinternalforcesand deformation of superstructure and support force, the fixed support is nodeformation. Thenput reaction on the basement of mechanics of materials, andon the assumption that the ground reaction force is linear to analyze thefoundation, thus obtaining the internal forces and deformation in foundation.Then put reaction on the foundation or pile to check the foundation for thestrength and deformation. This conventional design method based on artificialseparation of the superstructure and foundation, neglect deformation anddisplacement of foundation, calculated results and experimental results areobviousdifferences.The interaction design method is a method which is design as a mutualcoordination of thesuperstructure and foundation. And the connecting point onthe meeting point of contact deformation conditions for the whole systemdeformationandinternalforces.The interaction design method involving to the superstructure,foundationand foundations with their own characteristics, because there are too manyfactors in the interaction design andthey integrating into awhole, so the designmethod is actually very complicated and difficult, This paper is confined to astudyof multi-storeybuildings together with the non- interaction design methodandinteractiondesignmethod.Asthe interactiondesignofthesuperstructure,raft andthefoundationthatinvolves many complicated calculation, and data volume is so huge, fullyutilizing computer calculation advantages not only made the basis for designshort time, and the accuracy and reliability has been a good guarantee. Butaccess tothe structural design oftheexistingprocedures, orlackofa systematicbasis, or does not pay sufficient attention to the theoreticalresearch, even if theapproach is too one-sided and single. Consider this; it is necessary to study theresultsofdesignsoftware.This paper based on a multi-storey building in Shanghai as an example,using different finite element software, numerical simulation to explore themechanism of the two parts workingbased on international analyticmethod andconventional method. The results of both lateral displacement and stressmechanism in the two raft foundation analytic method are subject to thecomparativeanalysis.Manyaspectsstillneedfurtherstudytobeimproved.Themainconclusionsinthispaper:1.Displacementofraftfoundationdisciplinarian:inbothcases,settlementof the raft foundation have shown marginal larger, central smaller. Afterconsidering the interaction design method, the biggest and the leastdisplacementofraftfoundation willdiminish.2.Afterconsideringtheinteractiondesignmethod,thetensilestressoftopraftwillincrease,compressionstress will reduce,thatis,inpractical application,we should reduce the percentage of reinforcement in the bottom of raftfoundation.3.In both cases, the central force of raft foundation is similar. On bothsidesthecentralforceisdefinitelydifferent.4.The result of PKPM design software and ANSYS software is thesame,in practical engineering design, it is easy to use our familiarPKPM software tomeetthedesignaccuracyofmulti-storeybuildingraftfoundation.