scholarly journals On the performance of inelastically responding asymmetric structures designed by the modal response spectrum method of NZS 4203:1992

1994 ◽  
Vol 27 (2) ◽  
pp. 96-106
Author(s):  
A. M. Chandler ◽  
X. N. Duan
Keyword(s):  
Structural Damage ◽  
Response Spectrum ◽  
Regularity Conditions ◽  
Ultimate Limit State ◽  
Response Spectrum Method ◽  
Ductility Demand ◽  
Edge Elements ◽  
Asymmetric Buildings ◽  
Spectrum Method ◽  
Modal Response

The primary objective of this paper is to evaluate the effectiveness of the 3-dimensional modal response spectrum method (MRSM), as specified in the seismic design regulations of NZS 4203:1992, in accounting for torsional effects arising in stiffness-asymmetric buildings. Such buildings are assumed to be excited well into the inelastic range of response, where ultimate limit state design criteria are applicable. Also included is a study of the horizontal regularity conditions of NZS 4203:1992. This preliminary study focuses on the influence that these regularity conditions have on the selection of an appropriate codified approach for the design of torsionally asymmetric buildings. In particular, restrictions on the use of the equivalent static method of design (ESM), leading to a requirement to employ the MRSM to account for dynamic torsional effects, are discussed in some detail. The dynamic response studies indicate that in systems designed by the MRSM, no significant increase in ductility demand arises in flexible-edge elements (compared with symmetric systems). Furthermore, the MRSM may be over-conservative for the design of flexible-edge elements, in cases of structures having intermediate or large eccentricity. However, significant additional ductility demand may arise in the stiff-edge element in highly asymmetric buildings subjected to strong ground motion. In such cases, therefore, structures designed by the MRSM may not achieve the design aim of consistent protection given to symmetric and asymmetric systems against excessive inelastic response and consequent structural damage.

scholarly journals A study on earthquake performances of reinforced concrete buildings with various number of stories

2021 ◽  
Vol 4 (2) ◽  
pp. 83-98
Author(s):  
Yuşa Uğur Çapa ◽  
Ali Ruzi Özuygur ◽  
Zekai Celep
Keyword(s):  
Load Capacity ◽  
Response Spectrum ◽  
Lateral Load ◽  
Seismic Load ◽  
Implicit Assumption ◽  
Response Spectrum Method ◽  
Nonlinear Load ◽  
Seismic Codes ◽  
Spectrum Method ◽  
Modal Response

Seismic codes generally require that the Equivalent Seismic Load Method or the Modal Response Spectrum Method is adopted in the design of buildings. In the equivalent seismic load method, the equivalent seismic static force applied to the building is determined depending on the seismicity of the region where the building is located, the usage class of the building, the fundamental period of the building and the building mass. Later, this equivalent seismic load is reduced by the seismic load reduction factor to take into account the increase in the capacity of the system and the decrease in the seismic demand due to the nonlinear and inelastic behavior of the system, i.e., by accepting limited inelastic deformations in the building subjected to the design earthquake. Then, structural system of the building is analyzed under the reduced seismic forces in addition to the vertical loads by using the load combinations given in the design codes. The process is completed by designing the sections and the structural elements of the building. Similar processes can be implemented by using the modal response spectrum method. The difference between these two methods is consideration of the higher modes of the building instead of the first mode only and the use of the modal masses of the building for each mode, instead of the total mass of the building. In the latter method, the contributions of the higher mode are combined by using specific superposition rules. The codes assume that the structural systems designed in this way will exhibit the almost same level of inelastic deformation, i.e., the controlled damage state, regardless of the building parameters, such as the number of stories. In this study, an attempt is made to investigate the validity of this implicit acceptance. For this purpose, the buildings with a various number of stories are designed by satisfying the bare minimum requirements of the code only, as much as possible. The seismic behavior and the lateral load capacity of these buildings are examined by the static and dynamic nonlinear analyses. The ratio of the nonlinear load capacity to the reduced equivalent seismic load is evaluated depending on the number of the stories of the buildings. The results which are presented in detail yield that the buildings with a low number of stories have relatively larger nonlinear lateral load capacity-to-the reduced elastic seismic load ratio, which is not compatible with the general implicit assumption made in the seismic codes.

Seismic response analysis of steel–concrete hybrid wind turbine tower

2021 ◽  
pp. 107754632110075
Author(s):  
Junling Chen ◽  
Jinwei Li ◽  
Dawei Wang ◽  
Youquan Feng
Keyword(s):  
Wind Turbine ◽  
Response Spectrum ◽  
Ground Motions ◽  
Time History ◽  
Seismic Action ◽  
Response Spectrum Method ◽  
Spectrum Method ◽  
Wind Turbine Tower ◽  
Ground Types ◽  
Nonlinear Time History

The steel–concrete hybrid wind turbine tower is characterized by the concrete tubular segment at the lower part and the traditional steel tubular segment at the upper part. Because of the great change of mass and stiffness along the height of the tower at the connection of steel segment and concrete segment, its dynamic responses under seismic ground motions are significantly different from those of the traditional steel tubular wind turbine tower. Two detailed finite element models of a full steel tubular tower and a steel–concrete hybrid tower for 2.0 MW wind turbine built in the same wind farm are, respectively, developed by using the finite element software ABAQUS. The response spectrum method is applied to analyze the seismic action effects of these two towers under three different ground types. Three groups of ground motions corresponding to three ground types are used to analyze the dynamic response of the steel–concrete hybrid tower by the nonlinear time history method. The numerical results show that the seismic action effect by the response spectrum method is lower than those by the nonlinear time history method. And then it can be concluded that the response spectrum method is not suitable for calculating the seismic action effects of the steel–concrete hybrid tower directly and the time history analyses should be a necessary supplement for its seismic design. The first three modes have obvious contributions on the dynamic response of the steel–concrete hybrid tower.

Comparative Evaluation of Mode Combination Methods in Seismic Analysis Using Response Spectrum Method for Tank Structure Using FEA - Seismic FEA

2011 ◽  
Vol 110-116 ◽  
pp. 5240-5248
Author(s):  
Sujay Shelke ◽  
H.V. Vankudre ◽  
Vinay Patil
Keyword(s):  
Seismic Analysis ◽  
Response Spectrum ◽  
Initial Step ◽  
Relative Displacement ◽  
Geometrical Parameters ◽  
Response Spectrum Method ◽  
Spectrum Method ◽  
Combination Methods ◽  
Eigen Values ◽  
Modes Of Vibration

Typical seismic analysis using response spectrum method involves several steps from the initial step of extracting the modes. At the initial stage Eigen values are extracted corresponding to the modes of vibration. These give us Eigen vectors which are a series of relative displacement shapes; however these do not correspond to real displacements or stresses. Participation factors asses these Eigen vectors and grades them according to contribution they will have to the overall solution. Based on the spectral seismic acceleration, participation factor is used to calculate the mode coefficient, which is more of a scaling factor to give physical meaning to the values. Once the modes are extracted, the key issue is of combining these modes to obtain the seismic response. The modes cannot be added algebraically in reality as all the modes do not occur at the same time. Hence we employ methods which can add the modes in a more realistic manner. The objective of this paper is to do a comparative study of various mode combination methods with a focus on tank structures and study the effect of various geometrical parameters on the combination methods

A modified response spectrum method based on uniform probability spectrum

2018 ◽  
Vol 17 (2) ◽  
pp. 657-680
Author(s):  
Cheng Su ◽  
Zhijian Huang ◽  
Jianhua Xian
Keyword(s):  
Response Spectrum ◽  
Response Spectrum Method ◽  
Spectrum Method ◽  
Uniform Probability

Research on the Seismic Analysis and Optimization of High Flux Reactor Nuclear Power Piping System Based on Multi-Point Response Spectrum Method

2020 ◽  
Author(s):  
Xuan Huang ◽  
Pingchuan Shen ◽  
Shuai Liu ◽  
Jian Liu ◽  
Xiaozhou Jiang ◽  
...  
Keyword(s):  
Seismic Analysis ◽  
Response Spectrum ◽  
High Flux ◽  
Analysis Method ◽  
Response Spectrum Method ◽  
High Flux Reactor ◽  
Reactor Coolant ◽  
Spectrum Method ◽  
Flux Reactor ◽  
Coolant System

Abstract High flux reactor is an important engineering test reactor, which can be used in irradiation research of materials, chemistry, isotopes, medicine and other fields. In the high flux reactor coolant system, there are a large number of nuclear pipes and the layout is complex. The optimization of seismic analysis method for reactor coolant system is an important part in the design process to ensure the nuclear pipes meet the design specifications. The traditional single point response spectrum method needs to envelope the response spectrum of different floors as the analysis input. This method is difficult to give the reasonable seismic load to the numerous nuclear pipes and it will increase the design cost and the difficulty of safety analysis about nuclear pipe. In this paper, an optimized seismic analysis method of reactor coolant system is proposed. By using the multi-point response spectrum method, the optimization of different excitation loading modes for different constrained support points is realized. The analysis results show that the multi-point response spectrum method can solve the problem that different support points are located at different elevation floors in the reactor coolant system, which makes the calculation results more accurate and reasonable. Compared with the traditional method, it can make the design more efficient and practical.

Sign in / Sign up

Export Citation Format

Share Document