Pseudo-static Experimental Study On Seismic Performance Of Staircase In Reinforced Concrete Frame Structure

Stair system is the important part of building structure, it has always beenseriously destroyed in earthquake, especially the staircase of the widely usedreinforced concrete frame structure. However, the research on the stair has a late startat home. Although some research work has been carried out in recent years, and thereare some design codes and criterions for staircase, the study on seismic resistance ofstaircase is not enough. In order to provide some suggestions on the design of framestructure and its staircase, an systematic test and analysis of the stair is a urgent need.Two specimens of single layer frame structure with dog legs plate stair, onespecimen with sliding bearings, the other one is the narmal, were tested under laterallypseudo-static loading to investigate their performance, including their failure mode,seismic load-carrying capacity, deformation capacity, dissipative capacity, stiffnessdegradtion and the effect of the sliding bearings, etc. Based on the experimentalresults, the initial cracking position, cracking shape, developing regularity and brokenpattern for the two kinds of frame structure staircase under horizontal and verticalloading have been found out. The initial cracking load as well as the ultimate load forthe two kinds of frame structure staircase have been determined. Their strength anddeformation behavior as well as seismic behavior have been analyzed.From the experimental results, we can drawed the flollowing conclusion:1、Components of the stair system in the narmal frame structure involved in thelateral resisting work, on one hand, due to these components of the stair systemconstitute a lateral brace, they’re all bearing great forces, being the first seismic lineof defense, first cracking and occuring vary degrees of damage; on the other hand, theframe colums on the platform side show short colum features, the frame beams beargreat lateral force from the stair slabs.2、The sliding bearings prevent the force transfer way from the stair components,which make the failure mechanism of the specimen with sliding bearings similar tothe pure frame structure. There is almost no cracking in the board of staircase laddersand platform board, which guarantees the refuging in evacuation and rescuingfunctions of staircase. The test results show the sliding bearings work well andeffectively change the stress state of the frame structure staircase.3、Comparing and analysising the test result, we can see: stair components of thenarmal frame structure staircase improve its bearing capacity and stiffness, with lowdeformation, energy dissipation capacity and poor ductility. The frame structurestaircase with sliding bearings performance opposite, with beautiful post-seismicperformance.4、The end of the ladder board, where sets the sliding bearing, is tilting along thevertical in the experiment. The displacement along the vertical is increasing withthe lateral of thespecimen. So this paper suggests using a simple sliding bearing.Based on these test result, the corresponding conclusions related to improvementof the seismic design method of the frame structure and its staircase were reached inthis paper.Through this study, the damage model of the two kinds frame structure staircase,the bearing capacity, deformation, stiffness degradation and energy dissipationcapacity of the change have a better understanding, which provide reference to thetheoretical research and engineering applications of frame structure staircase.