Analysis Of Vertical Acceleration Floor Spectra Of Multistory Reinforced Concrete Frame Structures

As one of the important components to maintain the building function,the proportion of investment in non-structural elements in buildings is increasing year by year and it has long exceeded the proportion of investment in the main structural load-bearing elements.At present,since it is generally assumed that the structure is relatively rigid in the vertical direction,the seismic design of the structure and nonstructural members mainly focuses on the horizontal direction,the effect of vertical ground motion on the structure is ignored,and the attention paid to the study of vertical acceleration response of the structure and the vertical seismic design of nonstructural members is not enough.Significant amplification of vertical acceleration of the structure has been observed in the earthquakes and the completed shaking table tests,and due to the development of seismic isolation technology and TOD(Transit Oriented Development)projects,more and more buildings have started to adopt seismic isolation(vibration)measures to control the horizontal acceleration response of the structure under seismic,and the impact of rail transit vibration.Therefore,when the horizontal seismic safety of the structure is effectively guaranteed,the vertical acceleration response of the structure becomes an important factor in controlling non-structural safety.In recent years,reinforced concrete frame structures have accounted for the majority of newly built building structures in China,and there is no specific definition of the amplification factor for vertical response of structural floors in national codes.There is a lack of research on the vertical acceleration response of structures under seismic action.In response to the aforementioned research gaps,this article adopts the finite element numerical simulation method to analyze the multi-layer reinforced concrete frame structure.The main research content is as follows:1.The research on vertical acceleration response of the structure and the corresponding codes for vertical seismic design of nonstructural members at home and abroad were compiled,and it was found that the current research is relatively scattered,and there is no systematic consideration of the significant amplification of the vertical acceleration response of the structure caused by the vertical flexibility of the floor in the structure and the change of the vertical acceleration response of the structure by using seismic isolation(vibration)measures,and there is no specific definition of the amplification factor of the vertical acceleration response of the structure along the height of the structure in the codes of various countries,the amplification of the vertical acceleration response along the height of the structure is ignored,and only a rough definition is given for the vertical seismic design of non-structural members without considering the influence of the height of the structure.2.For the study of the vertical acceleration response of the structure,a total of 80 three-way actual ground shocks of four types were selected,taking into account the different response spectrum shapes,the characteristics of impulsive ground shocks and the effects of broadband ground shocks on the vertical acceleration response of the structure,and the spectral characteristics of the horizontal and vertical response spectra of the four types of ground shocks are analyzed.In order to take into account the real proportion of vertical ground shaking in the earthquake,the analysis is based on the natural three-way ratio of ground shocks for amplitude modulation.3.Under the premise of compliance with the code,a three-dimensional reinforced concrete frame structure was established using the finite element software ETABS,and the selected three-way ground shaking were used for elastic time course analysis.Based on the self-vibration frequency,as many floor slabs as possible were selected and the vertical acceleration time course data were extracted from the middle point of the floor slab and the side column points of the floor slab,and the MATLAB software was used to calculate the vertical acceleration amplification coefficient(PFAv/PGAv)and the vertical acceleration response spectrum of the structure.The spectral characteristics of the vertical acceleration response of floor slabs and structural column points with different selfvibration frequencies under earthquake action and its amplification laws along the height were compared and analyzed,and the floor slabs were divided into flexible floor slabs and rigid floor slabs with 25 Hz as the boundary,and the differences between the vertical acceleration amplification coefficients of the two types of floor slabs and structural column points and the horizontal floor amplification coefficients given by various countries were compared,and the relationship between the vertical acceleration response of the floor and self-vibration frequency of floor slab,the height of the floor and the different positions on the floor is given.4.The structural calculus models with conventional seismic isolation measures(rubber isolation bearings)and 3D seismic isolation(vibration)measures are established in ETABS,in which the vertical self-vibration frequencies of 3D seismic isolation(vibration)structures are controlled at 7 Hz,5 Hz and 3 Hz,respectively.Analyzed and compared the impact of different isolation measures on the vertical acceleration response of the structure,and provided reference suggestions for vertical isolation of the structure.5.Based on the vertical acceleration amplification characteristics exhibited by the floor slab with different self-vibration frequencies,the influence of the self-vibration frequency of the floor slab on the vertical acceleration response of the structure is considered,and the vertical acceleration response spectrum of the floor slab is normalized to 25 Hz and divided into two categories for envelope fitting,and the vertical design spectrum that can be used for subsequent research and design reference is given.