Study On Limiting Value Of Key Design Index Limits Of Box-plate Steel Structure

Box-plate steel structure is a kind of box structure system enclosed by ribbed steel plates.The design concept of the structure is derived from the superstructure of large ships,and it has the characteristics of rapid construction and good seismic performance.In order to promote the practical application of the structural system,Midas Gen software was used to study the key design index limits of the box-plate steel structural system,which mainly included the elastic and elastoplastic inter-story drift angle limitation of the structure,and the comfort index and limit of the box-plate steel structure floor.Specific research contents and conclusions are as follows:(1)A total of 24 examples were designed considering the height of the structure,the layout form and the opening rate of the wall panels.Pushover analysis was carried out to obtain the inter-story drift angle at the elastic and elastoplastic limits.Among them,the elastic limit is the first yield of the steel wall,and the elastoplastic limit is the failure of the reinforced structure at the Angle of more than 50%.It is found that when the elastic and elastoplastic limits of the box-plate steel structure are reached,the maximum inter-story displacement angle is less than the current limit,so it isn’t reasonable to apply the limit to the seismic design of the box-plate steel structure.Through the statistical analysis of these data,it is found that the maximum interlaminated displacement angle of the box-plate steel structure in the elastic and elastoplastic limits is in accordance with the lognormal distribution.According to the distribution characteristics of the ultimate interlaminar displacement Angle of the structure and the existing test data,and in combination with the relevant provisions of the seismic code in China,the limit values of the elastic and elastoplastic inter-story displacement angle of the box-plate steel structure system are put forward,which are 1/700 and 1/85 respectively.(2)The vibration characteristics of the box-plate steel floor were studied by using the MIDAS finite element software,and the influences of the parameters on the vibration characteristics of the floor are obtained by considering the thickness of the steel plate,the size of the stiffening ribs,the spacing of the stiffening ribs,the length-width ratio of the floor and the damping ratio.It is found that increasing the thickness of steel plate and the ratio of length to width of floor will reduce the acceleration effect and fundamental frequency of floor simultaneously.Changing the size and spacing of the L-type stiffeners and the flange width of the T-type stiffeners have little influence on the fundamental frequency,but great influence on the acceleration effect.The vertical fundamental frequency of the floor increases and the acceleration effect decreases when the height of the web of the T-stiffener is increased or the spacing is decreased.Among them,the spacing of T-type stiffeners will change the vibration of the floor.Increasing the damping ratio of the floor can effectively reduce the acceleration effect of the floor without changing the structure of the floor itself.(3)According to the parameter analysis results,the comfort evaluation standard of the box-type steel structure floor is analyzed and discussed,and the double control index of vertical fundamental frequency and peak acceleration is determined for the comfort evaluation of the box-type steel structure floor.According to the requirements of vibration intensity and people’s perception of peak acceleration,the limit value of comfort evaluation index of the floor is determined.The limit value of vertical fundamental frequency and peak acceleration are 20Hz and 0.15m/s~2 respectively.In order to facilitate the calculation of the vertical fundamental frequency of the floor system,through analyzing the influence degree of each parameter on the fundamental frequency of the floor system,the regression analysis of the main parameters is carried out,and the calculation formula of the fundamental frequency is put forward.Finally,according to the evaluation index and limit value of the comfort degree of the floor of the box-type steel structure,the calculation method of the comfort degree of the floor structure and the corresponding performance improvement measures are put forward.