scholarly journals Nonlinear seismic response of ground supported cylindrical reinforced concrete tanks

2021 ◽  
Author(s):  
Maryam Rafieeraad
Keyword(s):  
Seismic Behavior ◽  
Time History ◽  
Material Nonlinearity ◽  
Ground Acceleration ◽  
Response Modification Factor ◽  
R Factor ◽  
Earthquake Frequency ◽  
Modification Factor ◽  
Vertical Ground ◽  
Strength And Ductility

Seismic behavior of Liquid Containing Structures has been studied for decades. Being able to have these structures functioning during and after an earthquake is imperative for well-being of a society hence importance of their design. Response Modification Factor known as “R factor” is one of the key parameters in seismic design. However, in case of LCS’s, a justifiable guideline to determine the R factor is yet to be developed and current codes have utilized empirical values in design of these structures. The design intend for LCS’s is to meet the serviceability limits as opposed to life safety and collapse prevention which is the case of design of buildings. This study aims to investigate the effect of various parameters such as material nonlinearity, tank dimensions, base condition, concrete compressive strength, characteristics of seismic excitation records on the seismic behavior of concrete tanks. In this study, a finite element method is developed to investigate the seismic behavior of circular ground supported reinforced concrete tanks. First, the accuracy of current practice is investigated by employing the analytical and numerical methods, experimental studies. Finite element technique and pushover analysis are utilized to set up the pushover curve and achieve over-strength and ductility factors. The response modification factor (R) is then evaluated based on the nonlinear static analysis. Second, using the nonlinear dynamic analysis (time-history), the seismic behavioral aspects of full liquid tanks are studied taking into account the material nonlinearity, wall flexibility, effect of impulsive component, fluid-surface interaction and vertical ground acceleration. Thereafter, a parametric study is conducted to study the influence of tank dimensions, base fixity conditions and earthquake frequency content on the response modification factor. This study shows the over-strength and ductility factor of RC ground-supported tanks are significantly influence by tank size, height, height/diameter ratio and fundamental period. Also, fixed based tanks and shallow tanks have higher R values compared to hinged based and tall tanks respectively. The time history results show that the effect of material nonlinearity, vertical ground acceleration, base condition and earthquake frequency content on the dynamic behavior of liquid ground supported tanks is significant.

scholarly journals Nonlinear seismic response of ground supported cylindrical reinforced concrete tanks

2021 ◽  
Author(s):  
Maryam Rafieeraad
Keyword(s):  
Seismic Behavior ◽  
Time History ◽  
Material Nonlinearity ◽  
Ground Acceleration ◽  
Response Modification Factor ◽  
R Factor ◽  
Earthquake Frequency ◽  
Modification Factor ◽  
Vertical Ground ◽  
Strength And Ductility

Seismic behavior of Liquid Containing Structures has been studied for decades. Being able to have these structures functioning during and after an earthquake is imperative for well-being of a society hence importance of their design. Response Modification Factor known as “R factor” is one of the key parameters in seismic design. However, in case of LCS’s, a justifiable guideline to determine the R factor is yet to be developed and current codes have utilized empirical values in design of these structures. The design intend for LCS’s is to meet the serviceability limits as opposed to life safety and collapse prevention which is the case of design of buildings. This study aims to investigate the effect of various parameters such as material nonlinearity, tank dimensions, base condition, concrete compressive strength, characteristics of seismic excitation records on the seismic behavior of concrete tanks. In this study, a finite element method is developed to investigate the seismic behavior of circular ground supported reinforced concrete tanks. First, the accuracy of current practice is investigated by employing the analytical and numerical methods, experimental studies. Finite element technique and pushover analysis are utilized to set up the pushover curve and achieve over-strength and ductility factors. The response modification factor (R) is then evaluated based on the nonlinear static analysis. Second, using the nonlinear dynamic analysis (time-history), the seismic behavioral aspects of full liquid tanks are studied taking into account the material nonlinearity, wall flexibility, effect of impulsive component, fluid-surface interaction and vertical ground acceleration. Thereafter, a parametric study is conducted to study the influence of tank dimensions, base fixity conditions and earthquake frequency content on the response modification factor. This study shows the over-strength and ductility factor of RC ground-supported tanks are significantly influence by tank size, height, height/diameter ratio and fundamental period. Also, fixed based tanks and shallow tanks have higher R values compared to hinged based and tall tanks respectively. The time history results show that the effect of material nonlinearity, vertical ground acceleration, base condition and earthquake frequency content on the dynamic behavior of liquid ground supported tanks is significant.

Non-linear behavior of ground-supported circular reinforced concrete tanks

2021 ◽  
Author(s):  
Maryam Rafieeraad ◽  
M. Reza Kianoush ◽  
Mehdi Moslemi
Keyword(s):  
Seismic Behavior ◽  
Current Practice ◽  
Time History ◽  
Response Modification Factor ◽  
R Factor ◽  
Linear Behavior ◽  
History Analysis ◽  
Earthquake Frequency ◽  
Modification Factor ◽  
Nonlinear Static

This study aims to investigate the effect of various parameters on the seismic behavior of concrete tanks. A finite element method using pushover and time-history analysis is developed to investigate the seismic behavior of circular ground-supported tanks. The response modification factor (R) is evaluated based on nonlinear static and time-history analyses. R factor is one of the key parameters in seismic design. In liquid containing structures, R-Factor in current codes and standards are based on empirical values. Therefore, a justifiable guideline to accurately determine these values is yet to be developed. This study shows that the effect of tank size, material non-linearity, base condition, and earthquake frequency content is significant. Also, fixed based and shallow tanks have higher R values compared to hinged based and tall tanks, respectively. Based on the results of this study, it is found that the value of R specified in current practice is not appropriate.

scholarly journals Seismic Response Modification Factorof Reinforced Concrete Frames Basedon Pushover Analysis

2019 ◽  
Vol 2 (2) ◽  
Author(s):  
Amira Elyamany Mohamed ◽  
Walid A Attia ◽  
Wael M. El-Degwy
Keyword(s):  
Reinforced Concrete ◽  
Seismic Analysis ◽  
Pushover Analysis ◽  
Fundamental Period ◽  
Concrete Frames ◽  
Reinforced Concrete Frames ◽  
Response Modification Factor ◽  
R Factor ◽  
Modification Factor ◽  
The Given

Response modification factor is an essential factor in seismic analysis to provide economic design of reinforced concrete structures. Base shear force is divided by the response modification factor to consider the ability of the structure to dissipate energy through plastic hinges. The current study investigates the effects of changing some parameters on response modification factor (R-factor). Four groups of reinforced concrete frames were studied with different number of bays, number of stories, load pattern, and fundamental period of vibration. All reinforced concrete frames were analyzed using SAP 2000 then the straining actions results were used at specific excel sheets which are developed to design reinforced concrete members according to the Egyptian code of practice ECP-203 and ECP-201. Frames were analyzed by nonlinear static analysis (pushover analysis) using SAP2000. A sum of thirty two systems of frames was analyzed. According to the results, every frame has its unique value of R-factor. Accordingly, many parameters should be mentioned and considered at code to simulate the actual value of R-factor for each frame. Response modification factor is affected by many factors like stiffness, fundamental period of vibration, number of bays, frame height, geometry of the structure, etc. The given values of R-factor at ECP-201 can be considered conservative; as the accurate values of R-factor is higher than the given values.

Response modification factors for steel buckling restrained braced frames designed as per the 2010 National Building Code of Canada

2016 ◽  
Vol 43 (8) ◽  
pp. 702-715 ◽  
Author(s):  
Moniruzzaman Moni ◽  
Saber Moradi ◽  
M. Shahria Alam
Keyword(s):  
Time History ◽  
Building Code ◽  
Braced Frames ◽  
Response Modification Factor ◽  
Building Frames ◽  
Modification Factor ◽  
Design Values ◽  
Nonlinear Static ◽  
Buckling Restrained Braced Frames ◽  
Dynamic Time

This paper evaluates the overstrength, ductility, and response modification factors for low to mid-rise buckling restrained braced frames (BRBFs) designed as per the 2010 National Building Code of Canada. In addition to nonlinear static pushover analyses, dynamic time history analyses are performed to assess the seismic performance of four-, six-, and eight-story BRBFs. Different bracing configurations, including chevron (inverted-V) and split-X braces, are considered for the building frames with varied frame span lengths of 6 m and 8 m. The results confirm that the prescribed design values for overstrength and ductility factors provide reasonable estimations of the lower bound for these factors. The response modification factor obtained in this study ranged from 4.8 to 6 for different frames. The results also indicate that the response modification factor decreases with the increase of story height and span length. Moreover, bracing configurations may slightly affect the response modification factor for BRBFs.

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.

scholarly journals Seismic Response of Ground Cylindrical and Elevated Conical Reinforced Concrete Tanks

2021 ◽  
Author(s):  
Mehdi Moslemi
Keyword(s):  
Finite Element ◽  
Dynamic Behaviour ◽  
Cone Angle ◽  
Tank Wall ◽  
Frequency Content ◽  
Ground Acceleration ◽  
Earthquake Frequency ◽  
Wall Flexibility ◽  
Elevated Tanks ◽  
Vertical Ground

In this study, the seismic performance of concrete ground-supported cylindrical as well as liquid-filled elevated water tanks supported on concrete shaft is evaluated using the finite element method. The effects of a wide spectrum of parameters such as liquid sloshing, tank wall flexibility, vertical ground acceleration, tank aspect ratio, base fixity, and earthquake frequency content on dynamic behaviour of such structures are examined. Furthermore, the adequacy of current practice in seismic analysis and design of liquid containing structures is investigated. A comprehensive parametric study covering a wide range of tank capacities and aspect ratios found in practice today is also carried out on elevated tanks. Two different innovative strategies to reduce the seismic response of elevated tanks are examined, in the first strategy the inclined cone angle of the lower portion of the vessel is increased while in the second strategy the supporting shaft structure is isolated either from the ground or the vessel mounted on top. The results of this study show that capability of the proposed finite element technique. Using this method, the major aspects in the fluid-structure interaction problems including wall flexibility, sloshing motion, damping properties of fluid domain, and the individual effects of impulsive and convective terms can be considered. The effects of tank wall flexibility, vertical ground acceleration, base fixity, and earthquake frequency content are found to be significant on the dynamic behaviour of liquid tanks. The parametric study indicates that the results can be utilized with high level of accuracy in seismic design applications for conical elevated tanks. This study further shows that increasing the cone angle of the vessel can result in a significant reduction in seismically induced forces of the tank, leading to an economical design of the shaft structure and the foundation system. It is also concluded that the application of passive control devices to conical elevated tanks offers a substantial benefit for the earthquake-resistant design of such structures.

scholarly journals Investigating the Effect of the Number of End-Panel Studs on the Seismic Properties of Cold-Formed Light-Steel Shear-Panel Braces

2013 ◽  
Vol 59 (2) ◽  
pp. 197-214
Author(s):  
Mohammad Reza Javaheri Tafti ◽  
Farhad Behnamfar
Keyword(s):  
Brittle Failure ◽  
Failure Modes ◽  
Load Capacity ◽  
Response Modification Factor ◽  
Seismic Properties ◽  
R Factor ◽  
Modification Factor ◽  
Cold Formed Steel ◽  
Main Factors ◽  
Shear Panel

Abstract Detailed investigation of the effect of the number of end-panel studs on the seismic properties of light-steel shear-panel braces in cold-formed steel frames and in particular the associated response modification coefficients (R) factor, are presented in this paper. A total of 6 full-scale 1200×2400 mm specimens are considered, and the responses investigated under a standard cyclic loading regime. Of particular interest are the specimens’ maximum lateral load capacity and deformation behavior as well as a rational estimation of the seismic response modification factor. The study also looks at the failure modes of the system and investigates the main factors contributing to the ductile response of the tested shear-panel braces in order to suggest improvements so that braces respond plastically with a significant drift and without any risk of brittle failure, such as connection failure or stud buckling.

scholarly journals Seismic Response of Ground Cylindrical and Elevated Conical Reinforced Concrete Tanks

2021 ◽  
Author(s):  
Mehdi Moslemi
Keyword(s):  
Finite Element ◽  
Dynamic Behaviour ◽  
Cone Angle ◽  
Tank Wall ◽  
Frequency Content ◽  
Ground Acceleration ◽  
Earthquake Frequency ◽  
Wall Flexibility ◽  
Elevated Tanks ◽  
Vertical Ground

In this study, the seismic performance of concrete ground-supported cylindrical as well as liquid-filled elevated water tanks supported on concrete shaft is evaluated using the finite element method. The effects of a wide spectrum of parameters such as liquid sloshing, tank wall flexibility, vertical ground acceleration, tank aspect ratio, base fixity, and earthquake frequency content on dynamic behaviour of such structures are examined. Furthermore, the adequacy of current practice in seismic analysis and design of liquid containing structures is investigated. A comprehensive parametric study covering a wide range of tank capacities and aspect ratios found in practice today is also carried out on elevated tanks. Two different innovative strategies to reduce the seismic response of elevated tanks are examined, in the first strategy the inclined cone angle of the lower portion of the vessel is increased while in the second strategy the supporting shaft structure is isolated either from the ground or the vessel mounted on top. The results of this study show that capability of the proposed finite element technique. Using this method, the major aspects in the fluid-structure interaction problems including wall flexibility, sloshing motion, damping properties of fluid domain, and the individual effects of impulsive and convective terms can be considered. The effects of tank wall flexibility, vertical ground acceleration, base fixity, and earthquake frequency content are found to be significant on the dynamic behaviour of liquid tanks. The parametric study indicates that the results can be utilized with high level of accuracy in seismic design applications for conical elevated tanks. This study further shows that increasing the cone angle of the vessel can result in a significant reduction in seismically induced forces of the tank, leading to an economical design of the shaft structure and the foundation system. It is also concluded that the application of passive control devices to conical elevated tanks offers a substantial benefit for the earthquake-resistant design of such structures.

scholarly journals Evaluation of NSP and MPA Methods to Optimize Special Truss Moment Frames (STMF) Using Island Genetic Algorithm

2021 ◽  
Author(s):  
Mohaddese Sadeghpour ◽  
VahidReza Kalatjari ◽  
Hossein Pahlavan
Keyword(s):  
Genetic Algorithm ◽  
Time History ◽  
Accurate Method ◽  
Moment Frames ◽  
Moment Frame ◽  
Response Modification Factor ◽  
Design Variables ◽  
Modification Factor ◽  
Dynamic Time ◽  
Special Truss Moment Frames

The purpose of the present study is to evaluate the Pushover (NSP) and Modal Pushover (MPA) analysis methods in optimizing Special Truss Moment Frames (STMF) using island genetic algorithm. For this purpose, the optimization program is written and developed in Matlab software, and OpenSees software is used for structural analysis. The design variables of truss arrangement, cross section of members, truss height values and length of special zone of truss moment frame are considered. The constraints of the optimization problem are based on the rules and restrictions of AISC341-16. Case studies were performed on five frames of 3, 6, 9, 12 and 15 stories with a story height of 3 meters and span length of 18 meters with the aim of minimizing weight and maximizing the response modification factor. The results of these analyses are compared with nonlinear dynamic time history analyses as the most accurate method available, which could be used to finally identify and introduce the most efficient method in these structures. The MPA method was able to show better performance than the NSP method in estimating the maximum response of the structure. Despite the excellent performance of this method, Evaluation of numerical results of this study indicates the non-economic nature of MPA method for low-rise structures, and the acceptable efficiency of this method for medium-height to high-rise structures.

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