scholarly journals Evaluation of Seismic Response Modification Factor (R) for Moderate-Rise RC Buildings with Vertical Irregular Configurations

2021 ◽  
Author(s):  
Momen Mohamed Ahmed ◽  
Mohamed Abdel-Basset Abdo ◽  
Waleed Abo El-Wafa Mohamed
Keyword(s):  
Seismic Performance ◽  
Seismic Design ◽  
Numerical Models ◽  
Lateral Load ◽  
Design Stage ◽  
Design Codes ◽  
Rc Buildings ◽  
Response Modification Factor ◽  
Modification Factor ◽  
R Value

Abstract Most international design codes consider the nonlinear seismic performance of a structure by the concept of reduction/modification factor (R). Then, an elastic static force-based method can be normally used for seismic design to create earthquake resistant RC buildings. The response modification factor (R) is sensitive to many aspects such as overall ductility, over-strength, damping, and redundancy levels. Indeed, these factors are severely affected by geometric irregularity of the structural system. So, R-value does not become a constant number for the all types of structures with the same lateral load resisting system, as many standard codes noted. It depends on types, combination, and degrees of geometric vertical irregularity. This research assesses the actual values of R for regular and familiar vertical irregularity cases in RC buildings with moment-resisting frames (MRF) systems. Also, it takes into account the reduction percent that may occurs in R-value due to these studied vertical irregularities. The vertical irregularity cases, such as set-back and soft story, are essentially needed to be studied greater than ever due to the wide propagation of these types of buildings in Egypt, recently. In addition, the potential analytical methods that may be used to calculate R-value in comparison with Egyptian code’s value. Nonlinear static pushover analysis is carried out using ETABS via three-dimensional numerical models. The findings prove that vertical irregular models have poor seismic capacities, in comparison with regular one, due to their sudden change in lateral stiffness than that with regular aspect. So, the response modification factor (R) must be re-calculated or even scaled-down before design stage with 15% and 25% for single and combined vertical irregularity, respectively. In addition, this investigation derives a vital equation between R values with vertical irregularity ratios in each studied model. This equation shall be a guide for seismic design codes, structural design engineers, and researchers. Accordingly, the response modification factor R does not become a fixed value regardless vertical irregularity aspects of the buildings, but it has a variable value that depend on their inelastic seismic performance of the lateral load resisting systems.

Response Modification Factor of Steel Frames with and Without Dampers

2020 ◽  
Vol 9 (6) ◽  
pp. 950-953
Keyword(s):  
Static Analysis ◽  
Seismic Design ◽  
Numerical Models ◽  
Steel Structures ◽  
Design Stage ◽  
Design Parameters ◽  
Element Analysis ◽  
Response Modification Factor ◽  
Numerical Studies ◽  
Modification Factor

Response modification factor (R) performs as one of the main seismic design parameters of new structures during earthquake and is considered as significant parameter of nonlinear equivalent static analysis which is a widely used method to evaluate the seismic response of a structure. A review of the literature illustrates that although various numerical studies have investigated the effect of viscous dampers on the response modification factor (R), lack of experimental study has been conducted to verify the numerical models. This study evaluates the response modification factor of steel frame with and without viscous damper. Experimental and numerical analysis have been conducted in the present research. It is found that results from finite element analysis agree well with the experimental results. Besides, the use of damper increases significantly the response modification factors of steel structures, e.g., the factor of structures with dampers are approximate 32% higher than the structures without dampers. The determined response modification factors for the different structures used in this study can be applied to conduct equivalent static analysis of buildings as an initial design stage.

scholarly journals Coupling Ratio-Based Design and Seismic Performance of Modular Prefabricated Hybrid Coupled Walls

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Yun Shi ◽  
Yumin Zhang ◽  
Jianbo Dai ◽  
Guangyuan Weng
Keyword(s):  
Finite Element ◽  
Seismic Performance ◽  
Seismic Design ◽  
Structural Damage ◽  
Design Procedure ◽  
Steel Structure ◽  
Design Stage ◽  
Lateral Stiffness ◽  
Coupling Ratio ◽  
Element Analysis

Based on the advantages of modular prefabricated multistory steel structure, a full-bolt-connected modular steel coupling beam-hybrid coupled wall system is presented. Further, a method of estimating the coupling ratio (CR) is proposed according to the continuous link method. A CR-based seismic design procedure is determined such that the structure utilizes the lateral stiffness of the shear wall, which is necessary to avoid structural damage under frequently occurring earthquakes. However, it also exhibits excellent ductility of the coupling beams, which is necessary for dissipating energy under infrequent earthquakes. Subsequently, nonlinear hysteretic analyses are conducted from finite element analysis software ABAQUS, and a parametric study based on the finite element technique is performed to identify the optimal value of the coupling ratio. Results indicate that the seismic performance of modular prefabricated HCWs was excellent, and the basic requirements for ductile behavior and lateral stiffness were satisfied for CR values from 50% to 60%. The obtained results confirm the accuracy of the CR-based seismic design method proposed in this study and are supported by the selection of the design parameter at the initial design stage.

A Comparative Study of Design Base Shear for RC Buildings in Selected Seismic Design Codes

2012 ◽  
Vol 28 (3) ◽  
pp. 1047-1070 ◽  
Author(s):  
Vijay Namdev Khose ◽  
Yogendra Singh ◽  
Dominik H. Lang
Keyword(s):  
Seismic Design ◽  
Response Spectrum ◽  
Cumulative Effect ◽  
Building Design ◽  
Site Classification ◽  
Eurocode 8 ◽  
Design Codes ◽  
Base Shear ◽  
Rc Buildings ◽  
Design Response Spectrum

Modern seismic building design codes tend to converge on issues of design methodology and the state-of-the-art. However, significant differences exist in basic provisions of various codes. This paper compares important provisions related to the seismic design of RC buildings in some of the major national seismic building codes viz. ASCE 7, Eurocode 8, NZS 1170.5, and IS 1893. Code provisions regarding the specification of hazard, site classification, design response spectrum, ductility classification, response reduction factors, and minimum design base shear are compared and their cumulative effect on design base shear is studied. The objective component of overstrength contributed by the material and load factors is considered to normalize the design base shear. It is observed that every code has merit over the other codes in some aspect. The presented discussion highlights the major areas of differences which need attention in the process of harmonization of different codes of the world.

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.

The behaviour, overview of damage and retrofit of steel buildings after the earthquakes of September 1985

1987 ◽  
Vol 20 (1) ◽  
pp. 30-41 ◽  
Author(s):  
Enrique Martinez-Romero
Keyword(s):  
Mexico City ◽  
Seismic Performance ◽  
Seismic Design ◽  
Steel Structures ◽  
The Other ◽  
Design Codes ◽  
Steel Buildings ◽  
Steel Construction ◽  
History Of

A brief introduction on the earthquake history of Mexico is made. A description of the various types of steel structures built in Mexico City is made, including comparisons of the other types of steel construction with more modern practices. Performance of steel buildings in the September 1985 earthquake are discussed and related to the local geotechnical conditions, including foundation behaviour. The evolution of seismic design Codes in Mexico City is presented and the Emergency Provisions recently issued, are discussed. Finally, some ideas of repairing damaged steel structures to improve their seismic performance meeting the higher demands of the reformed Code, are given as a retrofit.

scholarly journals Evolution of Seismic Site Classification According to the Criteria in Chilean Design Codes

2021 ◽  
Vol 11 (22) ◽  
pp. 10754
Author(s):  
Edgar Giovanny Diaz-Segura
Keyword(s):  
Seismic Design ◽  
Numerical Models ◽  
Site Classification ◽  
Design Codes ◽  
Design Code ◽  
Seismic Demands ◽  
Distinctive Features ◽  
The Usa ◽  
Soil Foundation ◽  
Lateral Heterogeneities

Design codes establish seismic site classifications to determine the seismic demand of a structure according to the response of the soil foundation under the action of earthquake ground motions; the site classification can even condition the feasibility of a project. The occurrence of great earthquakes in Chile has tested its design codes, generating much information and experience regarding the seismic design of structures that have allowed researchers to identify variations in seismic demands according to the kind of ground foundation and to propose seismic site classification methods in Chilean regulations since the 1930s; countries in the vanguard of seismic design, such as the USA, Japan, and New Zealand, proposed methods even earlier. In this document, the evolution of methodologies for seismic site classification according to the criteria in Chilean codes is analysed from their implementation in the 1930s to the most recently proposed design code NCh 433, 2018–2021. Although the distinctive features of each country shape the criteria in their design codes, clear knowledge of the evolution of established criteria from their origins is considered an important tool that contributes to the better understanding, interpretation and application of the seismic site classification methodologies contained in a design code with better criteria. Likewise, the review indicates a distinct need to conduct a continuous evaluation of the classification criteria supported by records of new earthquakes, as well as by physical and numerical models that allow incorporating variables which condition the response of the terrain such as topography, lateral heterogeneities, and basic effects.

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.

Determination of Modification Factor R for Seismic Design of Pressure Vessels Using ASME and Eurocodes

2005 ◽  
Author(s):  
N. Kokavesis ◽  
Ch. Botsis
Keyword(s):  
Seismic Design ◽  
Pressure Vessel ◽  
Structural Design ◽  
Response Spectrum ◽  
Pressure Vessels ◽  
Design Codes ◽  
Allowable Stress ◽  
Design Response Spectrum ◽  
Modification Factor ◽  
External Loads

The design of pressurized equipment such as columns, towers and reactors, heaters subjected to external loads is important from a safety point of view. Pressure vessel design codes provide guidelines for the combination of membrane stresses due to external loads and hoop stress. Customarily the seismic loads imposed by pressure vessel design codes are functions of allowable stress. The factor R is a modification factor of the design response spectrum. Its numerical value is based the capacity of a structural system to resist seismic actions in the nonlinear range. It generally reduces the seismic design forces to be smaller than those corresponding to a linear elastic response. The Uniform Building Code (UBC) has been used extensively for the seismic design of pressure vessels. With the advent of EUROCODES [2], the values proposed by UBC for factor R (usually 3 or 4) are not automatically accepted by local authorities. The pressure vessel mechanical designer must select a factor R that satisfies both the requirements of the pressure vessel code and the structural design code (local code) where the vessel is installed. This problem has also been acknowledged by several collogues in the past PVP conferences. In this paper the factor R is examined using ASME [10] codes and the guidelines provided by EUROCODES. A common basis for the selection of the factor R that satisfies both allowable stress design philosophies and structural design codes is established.

scholarly journals Effect of ‘X’ Type Bracing on Response Modification Factor for R.C. Building with Special Shaped Column Cross Sections

2021 ◽  
Vol 9 (VI) ◽  
pp. 4755-4762
Author(s):  
Baviskar Vinita
Keyword(s):  
Seismic Design ◽  
Cross Sections ◽  
Pushover Analysis ◽  
Lateral Force ◽  
Developed Countries ◽  
Structural Aspect ◽  
Damping Factor ◽  
Base Shear ◽  
Response Modification Factor ◽  
Modification Factor

Earthquake is the most destructive natural hazard in the world. While designing any earthquake resistant structure, actual forces developed are much higher than designed forces. Therefore, to get design lateral force, the actual base shear force should be reduced by the factor known as response modification factor(R). Response modification factor plays vital role in seismic design of structures. Components of response modification factor (R) are ductility factor, over strength factor, redundancy factor and damping factor. Generally, value of response modification factor is adopted from seismic design codes of developed countries such as Europe, United States and India. Column is important part of Reinforced concrete building as overall load is transferred through column. Not only from aesthetical point of view, but also from structural aspect special shaped columns performs better than rectangular columns. So this study aims at calculating components of response modification factor(R) for column cross section with special shapes (L, T, +) for ‘X’ type bracing. In this study total 16 models of different number of storeys i.e. 5,10 are analysed using Pushover analysis for different seismic zones. The study also involves comparison of response modification factor (R) for structures designed with Indian code IS1893:2016(Part1) and American code ASCE 7-16.

scholarly journals The Response Modification Factor for Seismic Design of Integral Abutment Bridges

2021 ◽  
Vol 10 (3) ◽  
pp. 140-153
Author(s):  
Shervin Maleki ◽  
Alireza Siadat
Keyword(s):  
Seismic Design ◽  
Longitudinal Direction ◽  
Integral Abutment ◽  
Response Modification Factor ◽  
Integral Abutment Bridges ◽  
R Factor ◽  
Abutment Bridges ◽  
Bridge Structures ◽  
Modification Factor ◽  
Rigid Connection

The response modification factor (R factor) is a crucial parameter for calculating the design seismic forces applied to a bridge structure. This factor considers the nonlinear performance of bridges during strong ground motions. Conventional bridge structures rely on the substructure components to resist earthquake forces. Accordingly, there are R factors available in the design codes based on the type of bridge substructure system. Lateral load resisting system of Integral Abutment Bridges (IABs) in the longitudinal direction is more complex than ordinary bridges. It involves the contributions from soils behind the abutments and soil/structure interaction (SSI) in addition to existing rigid connection between the superstructure and abutments. There is no R factor available in any design code throughout the world for IABs in the longitudinal direction that considers all these parameters. In this research, the Federal Emergency Management Agency publication  FEMA P695 methodology has been applied to estimate the R factor for IABs. It is found that 3.5 could be a safe and valid R factor in the longitudinal direction for seismic design of such bridges.

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