Lessons Learned from Recent Earthquakes and Research and Implications for Earthquake-Resistant Design of Building Structures in the United States

1986 ◽  
Vol 2 (4) ◽  
pp. 825-858 ◽  
Author(s):  
Vitelmo V. Bertero
Keyword(s):  
Lateral Force ◽  
The United States ◽  
Lessons Learned ◽  
Structural Quality ◽  
Building Structures ◽  
Response Modification Factor ◽  
Earthquake Resistant Design ◽  
Earthquake Resistant ◽  
Modification Factor ◽  
Recent Earthquakes

Following an overview of the special problems inherent in the design and construction of earthquake-resistant buildings in regions of high seismic risk, the techniques that will be required to solve these problems in the U.S. are discussed. Some lessons learned from recent earthquakes, particularly those in Chile and Mexico in 1985, are discussed as are some results of integrated analytical and experimental research at the University of California, Berkeley. The implications of the ground motions recorded during the 1985 Mexican and Chilean earthquakes, the performance of buildings during the Mexican earthquake, and the research results previously discussed are then assessed with respect to seismic-resistant design regulations presently in force (UBC) as well as those formulated by ATC 3-06 and the Tentative Lateral Force Requirements recently developed by the Seismology Committee of SEAOC. The rationale for and reliability of the values suggested by the ATC for the “Response Modification Factor R” and by the SEAOC Seismology Committee for the “Structural Quality Factor Rw” are reviewed in detail. In the conclusion to the paper, two solutions for improving the earthquake-resistant design of building structures are proposed: an ideal (rational) method to be implemented in the future, and a compromise solution that can be implemented immediately.

Proposal of orientation-independent measure of intensity for earthquake-resistant design

2021 ◽  
pp. 875529302110382
Author(s):  
Alan Poulos ◽  
Eduardo Miranda
Keyword(s):  
United States ◽  
Ground Motion ◽  
The United States ◽  
Design Codes ◽  
Intensity Measure ◽  
Independent Measure ◽  
Earthquake Resistant Design ◽  
Earthquake Resistant ◽  
Ground Motion Records ◽  
Structural Engineers

A new measure of ground motion intensity in the horizontal direction is proposed. Similarly to other recently proposed measures of intensity, the proposed intensity measure is also independent of the as-installed orientation of horizontal sensors at recording stations. This new measure of horizontal intensity, referred to as MaxRotD50, is defined using the maximum 5%-damped response spectral ordinate of two orthogonal horizontal directions and then computing the 50th percentile for all non-redundant rotation angles, that is, the median of the set of spectral ordinates in a range of 90°. This proposed measure of intensity is always between the median and maximum spectral ordinate for all non-redundant orientations, commonly referred to as RotD50 and RotD100, respectively. A set of 5065 ground motion records is used to show that MaxRotD50 is, on average, approximately 13%–16% higher than Rot50 and 6% lower than RotD100. The new measure of intensity is particularly well suited for earthquake-resistant design where a major concern for structural engineers is the probability that the design ground motion intensity is exceeded in at least one of the two principal horizontal components of the structure, which for most structures are orthogonal to each other. Currently, design codes in the United States are based on RotD100, and hence using MaxRotD50 for structures with two orthogonal principal horizontal components would result in a reduction of the ground motion intensities used for design purposes.

scholarly journals Dual Equivalent Lateral Force Method for Low-Rise Wooden Horizontal Hybrid Structure with Rigid Core

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Di Wu ◽  
Yoshihiro Yamazaki ◽  
Hiroyasu Sakata
Keyword(s):  
Shear Force ◽  
Design Procedure ◽  
Lateral Force ◽  
Hybrid Structure ◽  
Rigid Core ◽  
Seismic Shear ◽  
Earthquake Resistant Design ◽  
Earthquake Resistant ◽  
Building Systems ◽  
Structural Mass

Hybrid structure has shown some great features in the earthquake-resistant design. However, due to the different properties between the combined building systems, the distributions of structural mass and stiffness are prevalently irregular in breadth or height, which makes the widely used equivalent lateral force (ELF) method powerless to predict the seismic shear force of such hybrid structure. This study proposed a simple design procedure for determining the concerned seismic shear force of low-rise wooden horizontal hybrid structure in the preliminary linear design. The dual equivalent lateral force (DELF) method is presented that permits the extension of the ELF method by separating the hybrid structure into two independent substructures. It is shown that the proposed DELF method is sufficient to provide a reasonable estimation of the seismic shear force with satisfied accuracy.

Lessons Learned from Evaluating the Responses of Instrumented Buildings in the United States: The Effects of Supporting Building Characteristics on Floor Response Spectra

2019 ◽  
Vol 35 (1) ◽  
pp. 159-191 ◽  
Author(s):  
Hamidreza Anajafi ◽  
Ricardo A. Medina
Keyword(s):  
Response Spectra ◽  
Lateral Force ◽  
The United States ◽  
Lessons Learned ◽  
Seismic Demands ◽  
Nonstructural Components ◽  
Floor Response Spectra ◽  
Building Models ◽  
American Society ◽  
Instrumented Buildings

Floor spectra of many instrumented buildings are evaluated to identify and quantify influential parameters on the horizontal seismic responses of acceleration-sensitive nonstructural components (NSCs). It is shown that many of these parameters are not explicitly incorporated into the American Society of Civil Engineers ASCE 7-16 design equations and are challenging to capture through numerical building models. Significant torsional responses are identified, even for nominally regular buildings, which can increase seismic demands on NSCs located at a floor periphery. For many instrumented buildings, especially single-story ones, floor diaphragms behave as flexible in their plane. This behavior, while mitigating torsional responses, can increase demands on NSCs located away from elements of the lateral-force resisting systems. An evaluation of floor acceleration responses of instrumented buildings with basements reveals that in many cases, even with the presence of perimeter concrete basement walls, accelerations at grade level could be significantly larger than those at lower basement levels. Consideration should be given to establishing the seismic base at the lowermost basement elevation.

scholarly journals Response Modification Factors for Reinforced Concrete Structures Equipped with Viscous Damper Devices

2017 ◽  
Author(s):  
Heshmatollah Abdi ◽  
Farzad Hejazi ◽  
Mohd Saleh Jaafar ◽  
Izian Binti Abd Karim
Keyword(s):  
Reinforced Concrete ◽  
Seismic Design ◽  
Concrete Structures ◽  
Design Parameters ◽  
Reinforced Concrete Structures ◽  
Building Structures ◽  
Viscous Damper ◽  
Response Modification Factor ◽  
Finite Element Software ◽  
Modification Factor

The response modification factor is one of the seismic design parameters that determine the nonlinear performance of building structures during strong earthquakes. Most seismic design codes lead to reduced loads. Nevertheless, an extensive review of related literature indicates that the effect of viscous dampers on the response modification factor is no longer considered. In this study, the effect of implementing viscous damper devices in reinforced concrete structures on the response modification factor was investigated. Reinforced concrete structures with different stories were considered to evaluate the values of the response modification factors. A nonlinear statistic analysis was performed with finite element software. The values of the response modification factors were evaluated and formulated on the basis of three factors: strength, ductility, and redundancy. Results revealed that the response modification factors for reinforced concrete structures equipped with viscous damper devices are higher than those for structures without viscous damper devices. The number of damper devices and the height of buildings have significant effects on response modification factors. In view of the analytical results across different cases, we proposed an equation according to the values of damping coefficients to determine the response modification factors for reinforced concrete structures furnished with viscous damper devices.

QUANTIFYING GLOBAL SEISMIC PERFORMANCE FACTORS IN DUAL SYSTEMS WITH BUCKLING RESTRAINED BRACED FRAMES

2015 ◽  
Vol 2 (1) ◽  
Author(s):  
Sipan Yavarian ◽  
Rais Ahmad
Keyword(s):  
Nonlinear Models ◽  
Lateral Force ◽  
Dual System ◽  
Dual Systems ◽  
Response Modification Factor ◽  
Seismic Force ◽  
Modification Factor ◽  
Buckling Restrained Braced Frames ◽  
Collapse Behavior ◽  
Factor C

Dual structural systems are commonly used in high rise buildings for various architectural reasons. Buckling Restrained Braced Frame (BRBF) is an emerging seismic force-resisting system that is currently being permitted by American Society of Civil Engineers (ASCE) to be used either as a single seismic force-resisting system or in combination with other seismic force resisting systems. In conventional practice, ASCE suggests that while using BRBF in conjunction with other lateral force resisting systems in a dual configuration, the lowest Response Modification Factor (R) pertaining to the softer system shall be used. This may result in significant overdesigning of structures as higher contribution from the BRBF system are often remain unutilized. This research aims at developing a methodology for calculating modified Response Modification Factor, R for structures where dual system occurs horizontally. This research investigates the effect of using the newly suggested Response Modification Factor (R) for dual systems, where a BRBF system is combined with an Intermediate Moment Frame (IMF). The study aims at proposing an innovative way of calculating Response Modification Coefficient (R), Over-strength Factor (Ωo) and Deflection Amplification Factor (Cd) pertaining to the dual system. A wide variety of archetype sets are designed following FEMA guidelines with modified R as trial values for different seismic zones. To validate the trial values for R, system over-strength and period-based ductility, nonlinear 3D static (pushover) analyses were performed. The nonlinear models directly simulate essential deterioration modes that contribute to collapse behavior. Afterwards, for collapse assessment, nonlinear incremental dynamic analyses are conducted.

scholarly journals Response Modification Factor of RC Frames Strengthened with RC Haunches

2020 ◽  
Vol 2020 ◽  
pp. 1-18
Author(s):  
Junaid Akbar ◽  
Naveed Ahmad ◽  
Muhammad Rizwan ◽  
Sairash Javed ◽  
Bashir Alam
Keyword(s):  
Reinforced Concrete ◽  
Numerical Models ◽  
Lateral Force ◽  
Roof Displacement ◽  
Response Modification Factor ◽  
Capacity Curves ◽  
Displacement Capacity ◽  
Rc Frames ◽  
Modification Factor ◽  
Force Displacement

This paper presents experimental and numerical studies carried out on two-story reinforced concrete (RC) frames having weaker beam-column joints, which were retrofitted with reinforced concrete haunches to avoid joint panel damage under seismic actions. The design philosophy of the retrofit solution is to allow beam-column members to deform inelastically and dissipate seismic energy. Shake table tests were performed on three 1 : 3 reduced scale two-story RC frame models, including one model incorporating construction deficiencies common in developing countries, which was retrofitted with two retrofit schemes using RC haunches. The focus of the experimental study was to understand the seismic behaviour of both as-built and retrofitted models and obtain the seismic response properties, i.e., lateral force-displacement capacity curves and time histories of model response displacement. The derived capacity curves were used to quantify overstrength and ductility factors of both as-built and retrofitted frames. Finite element- (FE-) based software SeismoStruct was used to develop representative numerical models, which were calibrated with the experimental data in simulating the time history response of structure roof displacement and in predicting peak roof-displacement and peak base shear force. Moreover, the FE-based numerical models were subjected to a suite of spectrum natural accelerograms, linearly scaled to multiple intensity levels for performing incremental dynamic analysis. Lateral force-displacement capacity and response curves were developed, which were analyzed to calculate the structure ductility and overstrength factors. The structure R factor is the product of ductility and overstrength factors, which exhibited substantial increase due to the proposed retrofitting technique. A case study was presented for the seismic performance assessment of RC frames with/without RC haunches in various seismic zones using the static force procedure given in seismic code and using response modification factor quantified in the present research.

Seismic Performance Evaluation of Buildings in Taiwan

2014 ◽  
Vol 638-640 ◽  
pp. 1854-1857 ◽  
Author(s):  
Jeng Hsiang Lin
Keyword(s):  
Hazard Analysis ◽  
Building Structures ◽  
Design Standards ◽  
Seismic Performance Evaluation ◽  
Code Calibration ◽  
Reinforced Masonry ◽  
Earthquake Resistant Design ◽  
Earthquake Resistant ◽  
Cast Concrete ◽  
Probability Information

Integrating the available research results from fragility analysis of building structures and seismic hazard analysis, this study explored some probability information for current earthquake resistant design for general buildings and examined structural performance of buildings under the action of earthquake motions. The results of this study show that performance objectives suggested by FEMA are not realized for the buildings of light steel, pre-cast concrete, reinforced masonry, and un-reinforced masonry, designed according to the Taiwan seismic design standards. The results may provide some valuable information for future code calibration in Taiwan.

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