The Study Of The Earthquake-resistance And Design Methods For New Sliding Support Of Precast Stair

The cast-in-place stair is commonly used in the traditional engineering.But it has many defects such as complex template,slow construction speed and imprecise construction way.The disadvantage of the cast-in-place stair is just the advantage of the precast stair.At the same time,the standardization degree and the efficiency of industrial production of the precast stair is higher than the other prefabricated components.Therefore,the research of the high-quality precast stair has more value and future application place under the background of highly-promoted construction industry in China.But there existed two following problems in the research before:On the one hand,the research of the earthquake resistance of the precast stair is less.On the other hand,it's not convenient for hoisting when the precast stair is heavy.So this paper mainly revolves to solve around above two problems:(1)Summarizes the earthquake damages and failure mechanism of the stair,and the domestic existing construction measures for earthquake resisting.Combining with the structure characteristics of the early beam precast stair,put forward a new type of beam precast stair.At the same time,after summarizing the up and down connection mode,this paper proposes a bolt connection which is more convenient and concise.(2)This paper establishes a 6 layer frame structure with the finite element software.Based on the up and down connection way of the precast stair,analyses the dynamic time history of "no stair model","the stair solid on both sides model","the stair with solid upside and sliding downside model","the stair with fixed hinge upside and sliding downside model".Analysis results show that whether the upside connection is cast-in-place or fixed hinge,Analysis results show that whether the upper equivalent cast-in-place connection or fixed hinge connection.Set bottom sliding support of precast stairs can effectively release the brace effect,reduce the impact on the overall stiffness.Setting sliding support can effectively reduce the ladder's internal force and the influence of the other components,making the ladder beam,the ladder and the ladder column more accord with the existing design method.At the same time,the sliding support has good ability of deformation.The displacement of the sliding support under strong earthquake can take consideration as elastic-plastic displacement between layers.(3)Based on setting the sliding support precast stairs is not involved in the whole structural calculation,collects the bearing capacity and the design method of the normal service condition of the precast stair under the vertical load.Suggests the method for estimating intensity and length under the earthquake.Optimizes the reinforce arrangement of the new "hollow" precast stair.And also suggests new structural measures for the ladder beam and column.(4)Take a precast concrete stairs project as an example,the plate precast stairs and the new beam precast stairs are compared and calculated.The calculation results show that:under the condition of guarantee the bearing capacity of the stairs,New beam precast stairs compared with plate precast stairs,it effectively reduces the dosage of concrete and reinforcing steel bar,and has the good economic efficiency.