scholarly journals Seismic Response of Ground-Supported Circular Concrete Tanks

2021 ◽  
Author(s):  
Ahmed Hafez
Keyword(s):  
Seismic Response ◽  
Prestressed Concrete ◽  
Time History ◽  
Nonlinear Behavior ◽  
Elastic Behavior ◽  
Seismic Loads ◽  
Fe Method ◽  
Aspect Ratios ◽  
Fixed Base ◽  
Flexible Base

This study is focused on the nonlinear behavior of ground-supported open top circular concrete tanks under the effect of seismic loads. The tank support conditions are considered in this study where both flexible and nonflexible supports are investigated. A comparison between the behavior of reinforced concrete (RC) and prestressed concrete (PC) tanks is undertaken for flexible base condition. The finite element (FE) method is used to study the nonlinear response of circular tanks under dynamic time-history and push-over analysis. Furthermore, the response modification factors (R) included in current practice are evaluated based on the results of nonlinear dynamic and push-over analysis. Several tank configurations with different aspect ratios, construction method, and base conditions are used in this study to attain reliable results and to validate the Rvalues. The behavior of circular RC tanks under shrinkage effect is also investigated. Moreover, an innovative approach is presented in this study for flexile base tanks in order to further reduce the seismic response of these structures by using passive energy dissipation systems such as fluid viscose dampers (FVD). The results of this study show that higher R-values could be applied to fixed base tanks as compared to hinged base tanks. Also, shallower concrete tanks can be assigned higher R-values as compared to tall tanks. The results of this study show that the type of construction affects the tanks ductility. PC tanks show lower ductility as compared to RC tanks. Furthermore, this study shows that the flexible base tanks with seismic cables do not dissipate the seismic forces, as expected, due to the elastic behavior of the seismic cables. Based on the results of the FE analysis, it is shown that, using FVD reduces the tank response under seismic loads. The use of FVD improves the tank serviceability by reducing the concrete cracking. It is concluded that flexible based tanks equipped with FVD can be used as an economically feasible system in high seismic zones.

scholarly journals Seismic Response of Ground-Supported Circular Concrete Tanks

2021 ◽  
Author(s):  
Ahmed Hafez
Keyword(s):  
Seismic Response ◽  
Prestressed Concrete ◽  
Time History ◽  
Nonlinear Behavior ◽  
Elastic Behavior ◽  
Seismic Loads ◽  
Fe Method ◽  
Aspect Ratios ◽  
Fixed Base ◽  
Flexible Base

This study is focused on the nonlinear behavior of ground-supported open top circular concrete tanks under the effect of seismic loads. The tank support conditions are considered in this study where both flexible and nonflexible supports are investigated. A comparison between the behavior of reinforced concrete (RC) and prestressed concrete (PC) tanks is undertaken for flexible base condition. The finite element (FE) method is used to study the nonlinear response of circular tanks under dynamic time-history and push-over analysis. Furthermore, the response modification factors (R) included in current practice are evaluated based on the results of nonlinear dynamic and push-over analysis. Several tank configurations with different aspect ratios, construction method, and base conditions are used in this study to attain reliable results and to validate the Rvalues. The behavior of circular RC tanks under shrinkage effect is also investigated. Moreover, an innovative approach is presented in this study for flexile base tanks in order to further reduce the seismic response of these structures by using passive energy dissipation systems such as fluid viscose dampers (FVD). The results of this study show that higher R-values could be applied to fixed base tanks as compared to hinged base tanks. Also, shallower concrete tanks can be assigned higher R-values as compared to tall tanks. The results of this study show that the type of construction affects the tanks ductility. PC tanks show lower ductility as compared to RC tanks. Furthermore, this study shows that the flexible base tanks with seismic cables do not dissipate the seismic forces, as expected, due to the elastic behavior of the seismic cables. Based on the results of the FE analysis, it is shown that, using FVD reduces the tank response under seismic loads. The use of FVD improves the tank serviceability by reducing the concrete cracking. It is concluded that flexible based tanks equipped with FVD can be used as an economically feasible system in high seismic zones.

Lateral-Torsional Coupled Seismic Response of Asymmetric Multi-Tower Base Isolated Structures with Large Floors

2011 ◽  
Vol 243-249 ◽  
pp. 3975-3979 ◽  
Author(s):  
Yu Dang ◽  
Kai Cheng Huo ◽  
Fang Fang Qin
Keyword(s):  
Seismic Response ◽  
Shear Force ◽  
Time History ◽  
Torsional Response ◽  
Mass Eccentricity ◽  
Fixed Base ◽  
In Series ◽  
Isolated Structures

The special type isolated building defined as asymmetric multi-tower base isolated structure with large floor is discussed in this paper. The rigid layers in series models are obtained and the elastic time history method is used to analyze the performance and seismic response of the structure. With the objective of studying the influence of the mass eccentricity in the towers and the asymmetric towers, coefficients of shear force, the ratios of period and the ratios of drift are discussed. The following conclusions have been attained: Torsional drift can be significant depending on the isolated layer in the asymmetric multi-tower with large floor. Comparing with the fixed base structures, this special type isolated building still can be reduced torsional response. The effect of isolation is reduced with the mass eccentricity in the towers and the asymmetric towers increases. It is concluded from the study that the multi-tower base isolated building with large floor should be symmetric and central in order to increase performance of isolation.

scholarly journals Seismic Response Analysis of Prestressed Concrete Rocking Frame

2021 ◽  
Vol 11 (2) ◽  
pp. 585
Author(s):  
Zixiang Zhao ◽  
Xiaozu Su
Keyword(s):  
Theoretical Model ◽  
Seismic Response ◽  
Prestressed Concrete ◽  
Seismic Behavior ◽  
Time History ◽  
Equation Of Motion ◽  
Parameter Analysis ◽  
Response Analysis ◽  
Seismic Response Analysis ◽  
History Analysis

In order to investigate the seismic performance of prestressed concrete rocking frame (PCRF), a theoretical model based on rigid body is established for a one-story single-span PCRF. The PCRF studied in this paper has the connecting interfaces set at the column feet and at the inner faces of the beam–column joints, allowing the columns to be uplifted with the accompanying separation of the beam–column interface and rotation of the beam and column around the interface. The tendons are arranged along the centerline of the beam and columns. The connections between the beam and columns and the anchoring of columns are accomplished by prestressing the tendons. The theoretical model consists of a rigid beam, rigid columns and elastic tendons. The governing motion equation of the PCRF is derived based on the model and a numerical solution of the equation of motion is obtained. The energy dissipation of the PCRF is analyzed and the calculation method for the coefficient of restitution is derived. Time history analysis and parameter analysis of seismic response of the PCRF are conducted and the results show that the PCRF has promising seismic behavior.

scholarly journals Effects of Soil-Structure Interaction on the Inelastic Seismic Response of Continuous Bridges on Piled Foundation

2019 ◽  
Vol 8 (6) ◽  
pp. 1282-1290
Keyword(s):  
Seismic Response ◽  
Soil Structure ◽  
Pushover Analysis ◽  
Time History ◽  
Fundamental Period ◽  
Soil Structure Interaction ◽  
Structure Interaction ◽  
Fixed Base ◽  
Ductility Capacity ◽  
Nonlinear Time History

Effect of soil-structure interaction (SSI) on seismic response of bridges is not clearly understood, and in general practice, bridge design is carried out ignoring its effect. This is due to the general consensus that fixed base leads to a more conservative design despite the fact that many researchers indicate that ignoring soil-structure interaction may lead to underestimation of seismic response. The current paper aims to investigate the effect of SSI on the nonlinear seismic behavior of 9-span continuous bridge supported on pile foundation penetrating sandy soils. Three types of soils were investigated representing medium to stiff sandy soil. Both pushover analysis and nonlinear time history incremental dynamic analysis are carried out using Opensees to investigate the effect of SSI on the seismic response parameters (namely, fundamental period, pushover curves, foundation rigid body motions, global ductility capacity and demand, and maximum drift ratio) of the bridge and to compare it to fixed base assumption (i.e., SSI ignored). The results indicate that although SSI increases the flexibility of the structure (accordingly increasing fundamental period), the seismic demand of the bridge increases. This increase is more pronounced as the soil becomes softer.

scholarly journals Assessment of the Seismic Behavior of Selective Storage Racks Subjected to Chilean Earthquakes

Metals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 855 ◽  
Author(s):  
Eduardo Nuñez ◽  
Catalina Aguayo ◽  
Ricardo Herrera
Keyword(s):  
Numerical Models ◽  
Time History ◽  
Reduction Factor ◽  
Elastic Behavior ◽  
Inelastic Behavior ◽  
Base Shear ◽  
Aspect Ratios ◽  
The Cross ◽  
Selective Storage ◽  
Storage Racks

A seismic performance evaluation of selective storage racks subjected to Chilean Earthquakes was conducted using nonlinear pushover and nonlinear dynamic time-history analyses. Nine seismic records with two horizontal components and magnitude Mw > 7.7 were applied to numerical models of prototype rack structures. The prototype racks were designed considering two types of soil and two aspect ratios. The inelastic behavior of beam connections was included in the models. The results showed a predominantly elastic behavior, mainly in the cross-aisle direction, in comparison to the down-aisle direction. The inelastic action was concentrated in pallet beams and up-rigths. Higher values of base shear were reached, due to elevated rigidity in rack configurations, and an acceptable performance was obtained. A response reduction factor was reported in both directions, reaching values larger than the limit imposed by the Chilean standard. However, values below this limit were obtained in the cross-aisle direction, in some cases. Finally, in all cases, the calculated response modification factor is highly influenced by the overstrength obtained from seismic design.

Nonlinear Behavior of Circular Concrete Storage Tanks: History Pushover and Dynamic Loadings by Providing an Innovative Technique to Reduce the Seismic Response of Semi-Buried Tanks

2018 ◽  
Vol 878 ◽  
pp. 54-60
Author(s):  
Omid Reza Baghchesaraei ◽  
H.H. Lavasani ◽  
Alireza Baghchesaraei
Keyword(s):  
Control System ◽  
Vibration Control ◽  
Seismic Response ◽  
Nonlinear Behavior ◽  
Seismic Loads ◽  
Viscous Damper ◽  
Storage Tanks ◽  
Passive Vibration Control ◽  
Flexible Support ◽  
Support Conditions

This study has concentrated on the nonlinear behavior of semi-buried concrete cylindrical storage tanks not subjected to seismic loads such as earthquakes. The support conditions of the tank in this study were investigated in both flexible and rigid conditions. A comparison between the behavior of reinforced concrete and pre-stressed concrete of the tanks has been done for flexible support conditions. Finite Element Method (FE) has been used in order to determine the nonlinear response of cylindrical tanks under dynamic time history analysis and pushover. In addition, in this study a new approach has been provided for tanks with flexible support in order to reduce the seismic response of structures with the seismic rehabilitation method using a passive vibration control system of the viscous damper. it has been shown that using FVD the tank’s response subjected to the seismic loads is reduced. Another achievement of a passive vibration control system of the viscous damper (FVD) in concrete tanks, is the improvement of the system by reducing the cracking of concrete. It can be concluded that flexible-based tanks equipped with FVD can be used as an economical and practical system used in earthquake-prone areas.

Experimental Evaluation of Piecewise Exact Solution for Structure Isolated With Sliding Type Isolators Under Bidirectional Earthquake

2008 ◽  
Author(s):  
C. S. Tsai ◽  
Tsu-Cheng Chiang ◽  
Yung-Chang Lin
Keyword(s):  
Exact Solution ◽  
Rigid Body ◽  
Exact Solutions ◽  
Seismic Response ◽  
Experimental Evaluation ◽  
Base Isolation ◽  
Nonlinear Behavior ◽  
Simple Method ◽  
Fixed Base ◽  
Base Structure

In recent years, the base isolation technology has been recognized as a popular and an efficient way to upgrade the earthquake proof capability of a conventional fixed-base structure. Because the first mode of a base-isolated structure participates the most part of the seismic response from the point view of the modal analysis, it is reasonable to develop a simple method to evaluate the seismic responses of a base-isolated structure by assuming that the superstructure behaves as a rigid body during earthquakes. In this study, a piecewise exact solution for a structure isolated with a sliding type of isolators under bidirectional earthquakes has been developed. The comparisons between the experimental results and the piecewise exact solutions show that the proposed method can well simulate the nonlinear behavior of a structure equipped with sliding-type isolators when subjected to bidirectional earthquakes.

scholarly journals Investigating the Use of Natural and Artificial Records for Prediction of Seismic Response of Regular and Irregular RC Bridges Considering Displacement Directions

2021 ◽  
Vol 11 (3) ◽  
pp. 906
Author(s):  
Payam Tehrani ◽  
Denis Mitchell
Keyword(s):  
Seismic Response ◽  
Radial Displacement ◽  
Time History ◽  
Good Prediction ◽  
3D Analysis ◽  
Combination Rules ◽  
Principal Axes ◽  
Artificial Records ◽  
The Mean ◽  
Irregular Bridges

The seismic responses of continuous multi-span reinforced concrete (RC) bridges were predicted using inelastic time history analyses (ITHA) and incremental dynamic analysis (IDA). Some important issues in ITHA were studied in this research, including: the effects of using artificial and natural records on predictions of the mean seismic demands, effects of displacement directions on predictions of the mean seismic response, the use of 2D analysis with combination rules for prediction of the response obtained using 3D analysis, and prediction of the maximum radial displacement demands compared to the displacements obtained along the principal axes of the bridges. In addition, IDA was conducted and predictions were obtained at different damage states. These issues were investigated for the case of regular and irregular bridges using three different sets of natural and artificial records. The results indicated that the use of natural and artificial records typically resulted in similar predictions for the cases studied. The effect of displacement direction was important in predicting the mean seismic response. It was shown that 2D analyses with the combination rules resulted in good predictions of the radial displacement demands obtained from 3D analyses. The use of artificial records in IDA resulted in good prediction of the median collapse capacity.

scholarly journals Numerical Study of the Seismic Response of an Instrumented Building with Underground Stories

2021 ◽  
Vol 11 (7) ◽  
pp. 3190
Author(s):  
Edmundo Schanze ◽  
Gilberto Leiva ◽  
Miguel Gómez ◽  
Alvaro Lopez
Keyword(s):  
Seismic Response ◽  
Soil Structure ◽  
Numerical Study ◽  
Time History ◽  
Building Design ◽  
Average Height ◽  
The Real ◽  
Vibration Data ◽  
Finite Element Software ◽  
Stiffness Reduction

Engineering practitioners do not usually include soil–structure interactions in building design; rather, it is common to model and design foundations as embedded joints with joint–based reactions. In some cases, foundation structures are modeled as rigid bodies, embedding the first story into lower vertical elements. Given that the effects of underground floors on the seismic response are not generally included in current building design provisions, it has been little explored in the literature. This work compares and analyzes models to study the effects of different underground stories modeling approaches using earthquake vibration data recorded for the 16–story Alcazar building office in downtown Viña del Mar (Chile). The modeling expands beyond an embedded first story structure to soil with equivalent springs, representing soil–structure interaction (SSI), with varying rigid soil homogeneity. The building was modeled in a finite element software considering only dead load as a static load case because the structure remained in the framing stage when the monitoring system was operating. The instruments registered 72 aftershocks from the 2010 Maule Earthquake, and this study focused on 11 aftershocks of different hypocenters and magnitudes to collect representative information. The comparisons between empirical records and models in this study showed a better fit between the model and the real vibration data for the models that do consider the SSI using horizontal springs attached to the retaining walls of the underground stories. In addition, it was observed that applying a stiffness reduction factor of 0.7 to all elements in deformation verification models for average–height buildings was suitable to analyze the behavior under small earthquakes; better results are obtained embedding the structure in the foundation level than embedding in the street level; the use of horizontal springs with Kuesel’s model with traction for the analysis of the structure yields appropriate results; it is necessary to carefully select the spring constants to be used, paying special attention to the vertical springs. Even though the results presented herein indicate that the use of vertical springs to simulate the SSI of the base slab can result in major differences concerning the real response, it is necessary to obtain more data from instrumentation across a wider variety of structures to continue to evaluate better design and modeling practices. Similarly, further analyses, including nonlinear time–history and high–intensity events, are needed to best regulate building design.

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