Study Of Ground Motion Intensity Measures And Global Damage For High-rise Stack-like Concrete Structures

High-rise concrete structures belong to long and flexible cantilever structures,which can be used as chimney,radio and TV tower,navigation tower,petrochemical tower,exhaust tower and water tower.Compared with building structures,high-rise concrete structures may damage and even collapse under strong earthquakes due to the lack of multi-channel seismic defenses.According to the seismic damage characteristics of the high-rise stack-like structures,this paper focuses on the ground motion intensity measures.The intensity measures and global damage indices are studied based on common high-rise structures such as chimneys,water towers,and high-rise TV towers with theoretical deduction and numerical calculation analysis.The main contents and conclusions are as follows.(1)A spectral-acceleration-based combination-type intensity measure is proposed based on high-rise structures.The main idea of the IM is from modal decomposition method.The modal mass ratio is taken as the linear combination coefficient to allow for the contribution of higher modes.The period elongation effect is considered by exponential product of fundamental spectral acceleration and elongated spectral acceleration.The curvature is calculated by a post-processing in general finite element software ABAQUS based on differential principle.The efficiency and sufficiency of the index are tested under 44 far-field ground motions and 56 near-fault ground motions,respectively.The results show that the proposed seismic intensity index has high validity.(2)Under the three-dimensional ground motion input,the combination form and evaluation method of intensity measures are developed,and the efficiency and sufficiency of the index proposed in this paper as well as other indices are tested.Based on a RC chimney and a RC inverted cone shell water tower,the maximum curvatures distribution along the structures are analyzed under the action of far-field and near-fault pulsed ground motions,respectively.The effects of the combination of higher modes and period elongation effects on the validity of the intensity measure is discussed.Compared with the case in one-dimensional ground motion.The results indicate that after considering the effects of vertical ground motion,the curvature of the structure increases,and the period elongation of the structure is more obvious.Consequently,the ground motion strength index proposed in this paper has certain advantages in evaluating the seismic performance of high-rise RC structures under three-dimensional ground motion.(3)Based on the Windows platform,SABIMS,a calculation software for seismic intensity index has been developed.Based on the investigation of existing similar software,the functions of the existing commercial software have been improved,data import,response spectrum visualization,and the input of structural information is supported to facilitate the post-processing of response spectrum acceleration information.The multi-modal period elongation effects are available,11 earthquake intensity measures could be output with one click.The calculation is accurate and reliable.(4)The correlation study between 37 ground motion intensity measures and the Park-Ang damage index,maximum roof displacement ratio,and maximum floor acceleration of high-rise structures is carried out.Under the far-field ground motion,the period extension effect of the structure is analyzed from the perspective of different structural damage indexes,and the period extension coefficients of the high-rise structure are suggested based on three reinforced concrete chimneys.The correlation of different damage indices of high-rise concrete structures is evaluated.Based on the results,it is recommended to use the maximum roof displacement ratio as the damage index for analyzing and evaluating the seismic performance of high-rise structures.(5)Based on the incremental dynamic analysis(IDA)method,an overall damage model considering the area enclosed by the IDA curve is developed.The selection principle of the ground motion intensity measure in the damage model and the method of determining the collapse state of the structure in the IDA analysis are suggested.Taking a 386-meter high concrete TV tower as the research object,the applicability of the damage index model and other damage models in this paper is compared.The results show that the damage model proposed in this paper solves the problem of partial decline of the curve in some damage models.It is also more in line with the destruction form of high-rise concrete structures.