Study On Seismic Design Measures Of RC Frame Cliff-structures

The cliff-structure，widely built in mountainous cities, is a kind of special structurebuilt on slopes. Cliff-structures’ seismic response is different from that of regularstructures because of its special consolidated bases, so it needs special design measures.At present, there is no relevant specification or codes for cliff-structure, so structuralengineers designing cliff-structure mainly consult engineering experience. However, theresults of the present study on the cliff-structure are mainly about its seismicperformance, and lack detailed seismic design measures.This paper is aimed to present some reasonable suggestions and provide theoreticalbasis for the piling of the book REGULATIONS FOR DESIGN OF MOUNTAINOUSBUILDING STRUCTURES through discussing the weak parts of cliff-structure, whichdiffers from normal frame structures. Thus, this paper summarizes many formerresearch works concerning cliff-structure, analyzes the elastic and plastic performanceof cliff-structure during earthquake with the software PERFORM-3D, evaluates itsseismic performance in the ways of story drift, plastic energy dissipation and thedistribution of structural damage, and points out the weak points possibly existed incliff-structure; then it comes up with corresponding improving measures, confirms theireffectiveness through building analyzing models with the help of SAP2000andPERFORM-3D, analyzes their sensitiveness to overall structure, and points out thedetailed seismic design measures.By studying and analyzing the cliff-structure in this paper, the main conclusionsare achieved as follows:①Under the action of earthquake, weak parts in the non-tie-beam lie in the slab ofthe upper ground floor and the upper ground floor columns, especially the floorconnecting the non-tie-beam and tie-beam; while in the cliff-structure equipped with tiebeam, the weak parts lie in the slab of the first off-layer story, the tie-beam and theupper ground floor columns.②To the weak slab, because its mechanics characteristics are similar to transitionfloor slab, the seismic design measures of transition floor slab can be referred to indesigning. So the floor is proposed to be thickened, and the reinforcement ratio of theslab is suggested to increase by arranging two-storey-two-direction rebar.③The tie-beam mainly coordinates the deformation of the upper ground floor and the off-layer story in the tie-beam of the cliff-structure, and its axial force being large,its tensile strength should be designed.④When there are a large number of the upper ground floor columns, the strengthand ductility can be strengthened by increasing the ratio of longitudinal reinforcementand stirrup densification of the upper ground floor columns. When there are a smallnumber of the upper ground floor columns, according to codes, if the storey lateraldisplacement is allowed, the sliding support and isolation bearings are proposed to use.⑤At the same time, the seismic performance of cliff-structure can be improved byincreasing the lateral stiffness of the off-layer story. The lateral stiffness is proposed toincrease by setting shear wall which can reduce the stiffness difference of the upperground floor columns and other columns.