Study On The Position Coefficient Of Seismic Support Hanger When Calculating Horizontal Seismic Action Using Equivalent Lateral Force Method

In recent years,as the research on seismic design of building structures has become more and more perfect,the seismic capacity of the main structure of buildings has been greatly improved,basically ensuring that the main structure can be used normally after the earthquake,but the phenomenon that its non-structural components and attached electromechanical equipment,etc.are damaged under the condition that the main structure is intact,resulting in the loss of building use function,has not received higher attention.The seismic support hanger can provide important seismic support for electromechanical pipeline equipment,and is an important device to protect such equipment from damage during earthquakes.Regarding the horizontal seismic action calculation of seismic hanger,the most commonly used method is the equivalent lateral force method,which involves a parameter characterizing the amplification effect of each floor of the structure on the ground motion acceleration: the position coefficient.In China’s current Code for Seismic Design of Building Mechanical and Electrical Engineering(GB50981-2014),the position coefficients of the equivalent lateral force method are taken as 2 at the top of the structure and 1 at the bottom,and are linearly distributed along the height,without considering the influence of factors such as building type,self-oscillation period and site characteristic period,which are taken roughly and differ from the common engineering experience and perception.To address the above problems,a simplified analytical model is used to calculate the position coefficients of three types of structures under different site characteristic periods and different self-oscillation periods,and the corresponding formulas are fitted to explore and provide a reasonable basis for the seismic force calculation and code revision of seismic hanger in these types of structures.The main contents and research results of the study include the following aspects:(1)The simplified analysis models(layer shear model)of frame structure,frame shear structure and shear wall structure(bending-shear beam coupling model)were established respectively by using SAP2000 finite element software,and the results of time course analysis were compared with the space bar system model to verify the reasonableness of the simplified analysis models;(2)Six seismic waves with site characteristic periods Tg of 0.25 s,0.35 s,0.45 s,0.55 s,0.65 s and 0.75 s were selected according to the code,and each seismic wave contains 15 natural waves and 5 artificial waves.36 layer shear models and 36bending-shear beam coupled models were analyzed in time,and the results showed that the structure position coefficients take values that increase with the increase of the characteristic period of the site;(3)Based on the results of the time course analysis,the frame structure is divided into three cycle intervals of 0～0.8s,0.8s～1.2s and more than 1.2s according to the first-order self-oscillation period,and the frame shear structure and shear wall structure are divided into three cycle intervals of 0～1.5s,1.5s～2.5s and more than2.5s according to the first-order self-oscillation period,and the equations for the position coefficients of the three types of structures in different cycle intervals are fitted respectively.The results show that the shorter the first-order self-oscillation period of the structure,the larger the position coefficient value and vice versa;the results show that our code seriously underestimates the position coefficient value of the short-period structure and overestimates the position coefficient value of the long-period structure;(4)Three natural waves and one artificial wave with characteristic period of0.45 s were selected to carry out elastic-plastic time analysis on the spatial bar system models of frame structure,frame shear structure and shear wall structure respectively,and the results show that the position coefficient of the structure becomes smaller after entering elasticity,and the frame structure decreases the most,followed by frame shear structure and shear wall structure.