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.

scholarly journals Seismic Performance Evaluation of Stone Masonry Houses Constructed with Reinforced Concrete Bands

2020 ◽  
Vol 19 (1) ◽  
pp. 204-214
Author(s):  
Anju Maharjan ◽  
Hari Ram Parajuli
Keyword(s):  
Reinforced Concrete ◽  
Seismic Performance ◽  
Linear Time ◽  
Numerical Models ◽  
Fragility Curves ◽  
Research Work ◽  
Time History ◽  
Stone Masonry ◽  
Base Shear ◽  
Time Histories

 The research work was aimed evaluating the newly built stone masonry houses with mud mortar and with the provision of horizontal reinforced concrete (R.C.) bands. Two recently built stone masonry houses of different geometry were selected, modeled, and analyzed to investigate the seismic performance of stone masonry houses constructed with horizontal bands. Linear time history analysis was used and performance of the selected buildings was checked with the help of various numerical models. The top roof displacement, maximum drift ratio, base shear, and shell stress were compared between two selected models using three earthquake time histories. The fragility curves were also developed to identify the probability of the failure of the buildings at different peak acceleration values using three earthquake time histories.

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 Nonseismically Designed Reinforced Concrete Low Rise Buildings

2018 ◽  
Vol 24 (4) ◽  
pp. 112
Author(s):  
Thamir K. Mahmoud ◽  
Hayder A. Al-Baghdadi
Keyword(s):  
Reinforced Concrete ◽  
Numerical Model ◽  
Three Dimensional ◽  
Nonlinear Dynamic Analysis ◽  
Time History ◽  
Inelastic Behavior ◽  
Base Shear ◽  
Earthquake Excitation ◽  
Inelastic Responses ◽  
Concrete Damage

In this paper, the time-history responses of a square plan two-story reinforced concrete prototype building, considering the elastic and inelastic behavior of the materials, were studied numerically. ABAQUS software was used in three-dimensional (3D) nonlinear dynamic analysis to predict the inelastic response of the buildings. Concrete Damage Plasticity Model (CDPM) has been used to model the inelastic behavior of the reinforced concrete building under seismic excitation. The input data included geometric information, material properties, and the ground motion. The building structure was designed only for gravity load according to ACI 318 with non-seismically detailing requirements. The prototype building was subjected to El Centro 1940 NS earthquake at different amplitudes (PGA=0.05g, PGA=0.15g, and PGA=0.32g). The elastic and inelastic responses of the 3D numerical model of the same building were evaluated. The differences between the elastic and inelastic displacements and base shear forces were analyzed. It was found from the results that base shear responses are significantly more sensitive to the numerical model of analysis than displacement responses. The evaluation showed that the base shear force and displacement responses of a two-story R.C. building subjected to severe earthquake excitation are very sensitive to the numerical model used whether it is elastic or inelastic.  

scholarly journals Numerical study on the seismic performance of hybrid steel moment frames with CLT balloon shear walls

2020 ◽  
Author(s):  
◽  
Mehdi Khajehpour
Keyword(s):  
Numerical Study ◽  
Time History ◽  
Shear Walls ◽  
Shear Wall ◽  
Hybrid Structure ◽  
Reduction Factor ◽  
Base Shear ◽  
Moment Frames ◽  
Response Modification Factor ◽  
Capacity Curves

A proposed hybrid lateral load resisting system combining a moderately ductile steel moment resisting frame (SMRF) with Cross-laminated Timber (CLT) balloon-framed shear walls is investigated on 8, 12 and 16-storey case-study buildings using equivalent static, linear dynamic (modal), nonlinear static (push-over) and nonlinear dynamic (time history) analyses. First, a SMRF is designed using ETABS, then the hybrid structures are analysed in OpenSees. By adding the CLT shear wall to steel moment frame, the period of structure decreased and its stiffness increased. The time history analyses result revealed that by adding the CLT shear wall the maximum drift decreased, while the maximum base shear in hybrid structure slightly increased. The hold down uplift forces under earthquake records are reported and compared to each other. Using push-over capacity-curves, a ductility reduction factor of 3.6, an over strength factor of 1.57 and a seismic response modification factor of 5.67 are derived.

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 Comparison of Novel Seismic Protection Devices to Attenuate the Earthquake Induced Energy

Actuators ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 73
Author(s):  
Osman Hansu ◽  
Esra Mete Güneyisi
Keyword(s):  
Lateral Displacement ◽  
Time History ◽  
Seismic Protection ◽  
Base Shear ◽  
Seismic Demands ◽  
Nonlinear Time History Analyses ◽  
History Of ◽  
Protection Devices ◽  
Nonlinear Time History ◽  
Better Than

This study addresses an alternative use of viscous dampers (VDs) associated with buckling restrained braces (BRBs) as innovative seismic protection devices. For this purpose, 4-, 8- and 12-story steel bare frames were designed with 6.5 m equal span length and 4 m story height. Thereafter, they were seismically improved by mounting the VDs and BRBs in three patterns, namely outer bays, inner bays, and all bays over the frame heights. The structures were modeled using SAP 2000 software and evaluated by the nonlinear time history analyses subjected to the six natural ground motions. The seismic responses of the structures were investigated for the lateral displacement, interstory drift, absolute acceleration, maximum base shear, and time history of roof displacement. The results clearly indicated that the VDs and BRBs reduced seismic demands significantly compared to the bare frame. Moreover, the all-bay pattern performed better than the others.

scholarly journals Tuned Mass Damper Design for Slender Masonry Structures: A Framework for Linear and Nonlinear Analysis

2021 ◽  
Vol 11 (8) ◽  
pp. 3425
Author(s):  
Marco Zucca ◽  
Nicola Longarini ◽  
Marco Simoncelli ◽  
Aly Mousaad Aly
Keyword(s):  
Nonlinear Analysis ◽  
Linear Time ◽  
Design Procedure ◽  
Time History ◽  
Tuned Mass Damper ◽  
Second Phase ◽  
Masonry Structures ◽  
Base Shear ◽  
Mass Damper ◽  
Linear And Nonlinear

The paper presents a proposed framework to optimize the tuned mass damper (TMD) design, useful for seismic improvement of slender masonry structures. A historical masonry chimney located in northern Italy was considered to illustrate the proposed TMD design procedure and to evaluate the seismic performance of the system. The optimization process was subdivided into two fundamental phases. In the first phase, the main TMD parameters were defined starting from the dynamic behavior of the chimney by finite element modeling (FEM). A series of linear time-history analyses were carried out to point out the structural improvements in terms of top displacement, base shear, and bending moment. In the second phase, masonry's nonlinear behavior was considered, and a fiber model of the chimney was implemented. Pushover analyses were performed to obtain the capacity curve of the structure and to evaluate the performance of the TMD. The results of the linear and nonlinear analysis reveal the effectiveness of the proposed TMD design procedure for slender masonry structures.

Effect of Geometry on Droplet Generation in a Microfluidic T-Junction

2013 ◽  
Author(s):  
Katerina Loizou ◽  
Wim Thielemans ◽  
Buddhika N. Hewakandamby
Keyword(s):  
Aspect Ratio ◽  
Cross Section ◽  
Droplet Formation ◽  
Continuous Phase ◽  
Main Channel ◽  
Superficial Velocity ◽  
Droplet Generation ◽  
Dispersed Phase ◽  
Aspect Ratios ◽  
The Cross

The main aim of this study is to examine how the droplet formation in microfluidic T-junctions is influenced by the cross-section and aspect ratio of the microchannels. Several studies focusing on droplet formation in microfluidic devices have investigated the effect of geometry on droplet generation in terms of the ratio between the width of the main channel and the width of the side arm of the T-junction. However, the contribution of the aspect ratio and thus that of the cross-section on the mechanism of break up has not been examined thoroughly with most of the existing work performed in the squeezing regime. Two different microchannel geometries of varying aspect ratios are employed in an attempt to quantify the effect of the ratio between the width of the main channel and the height of the channel on droplet formation. As both height and width of microchannels affect the area on which shear stress acts deforming the dispersed phase fluid thread up to the limit of detaching a droplet, it is postulated that geometry and specifically cross-section of the main channel contribute on the droplet break-up mechanisms and should not be neglected. The above hypothesis is examined in detail, comparing the volume of generated microdroplets at constant flowrate ratios and superficial velocities of continuous phase in two microchannel systems of two different aspect ratios operating at dripping regime. High-speed imaging has been utilised to visualise and measure droplets formed at different flowrates corresponding to constant superficial velocities. Comparing volumes of generated droplets in the two geometries of area ratio near 1.5, a significant increase in volume is reported for the larger aspect ratio utilised, at all superficial velocities tested. As both superficial velocity of continuous phase and flowrate ratio are fixed, superficial velocity of dispersed phase varies. However this variation is not considered to be large enough to justify the significant increase in the droplet volume. Therefore it can be concluded that droplet generation is influenced by the aspect ratio and thus the cross-section of the main channel and its effect should not be depreciated. The paper will present supporting evidence in detail and a comparison of the findings with the existing theories which are mainly focused on the squeezing regime.

Modes of Wave Propagation and Dispersion Relations in Inclusion Reinforced Composite Plates

2010 ◽  
Author(s):  
Yu Cheng Liu ◽  
Jin Huang Huang
Keyword(s):  
Composite Plate ◽  
Elastic Moduli ◽  
Lamb Waves ◽  
Plate Thickness ◽  
Composite Plates ◽  
Dispersion Relations ◽  
Elastic Behavior ◽  
Effective Elastic Moduli ◽  
Aspect Ratios ◽  
Reinforced Composite

This paper mainly analyzes the wave dispersion relations and associated modal pattens in the inclusion-reinforced composite plates including the effect of inclusion shapes, inclusion contents, inclusion elastic constants, and plate thickness. The shape of inclusion is modeled as spheroid that enables the composite reinforcement geometrical configurations ranging from sphere to short and continuous fiber. Using the Mori-Tanaka mean-field theory, the effective elastic moduli which are able to elucidate the effect of inclusion’s shape, stiffness, and volume fraction on the composite’s anisotropic elastic behavior can be predicted explicitly. Then, the dispersion relations and the modal patterns of Lamb waves determined from the effective elastic moduli can be obtained by using the dynamic stiffness matrix method. Numerical simulations have been given for the various inclusion types and the resulting dispersions in various wave types on the composite plate. The types (symmetric or antisymmetric) of Lamb waves in an isotropic plate can be classified according to the wave motions about the midplane of the plate. For an orthotropic composite plate, it can also be classified as either symmetric or antisymmetric waves by analyzing the dispersion curves and inspecting the calculated modal patterns. It is also found that the inclusion contents, aspect ratios and plate thickness affect propagation velocities, higher-order mode cutoff frequencies, and modal patterns.

scholarly journals Dynamic Response Evaluation of Long-Span Reinforced Arch Bridges Subjected to Near- and Far-Field Ground Motions

2018 ◽  
Vol 8 (8) ◽  
pp. 1243 ◽  
Author(s):  
Iman Mohseni ◽  
Hamidreza Lashkariani ◽  
Junsuk Kang ◽  
Thomas Kang
Keyword(s):  
Ground Motion ◽  
Dynamic Performance ◽  
Time History ◽  
Bending Moment ◽  
Element Model ◽  
Structural Performance ◽  
Far Field ◽  
Inelastic Behavior ◽  
Earthquake Loads ◽  
Arch Bridges

This study assessed the structural performance of reinforced concrete (RC) arch bridges under strong ground motion. A detailed three-dimensional finite element model of a 400 m RC arch bridge with composite superstructure and double RC piers was developed and its behavior when subjected to strong earthquakes examined. Two sets of ground motion records were applied to simulate pulse-type near- and far-field motions. The inelastic behavior of the concrete elements was then evaluated via a seismic time history analysis. The concept of Demand to Capacity Ratios (DCR) was utilized to produce an initial estimate of the dynamic performance of the structure, emphasizing the importance of capacity distribution of force and bending moment within the RC arch and the springings and piers of the bridge. The results showed that the earthquake loads, broadly categorized as near- and far-field earthquake loads, changed a number of the bridge’s characteristics and hence its structural performance.

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