scholarly journals A simple method for determining seismic demands on gravity load frames

2017 ◽  
Vol 44 (8) ◽  
pp. 661-673 ◽  
Author(s):  
J. Beauchamp ◽  
P. Paultre ◽  
P. Léger
Keyword(s):  
Response Spectrum ◽  
Time History ◽  
Bending Moment ◽  
New Method ◽  
Simple Method ◽  
Seismic Demands ◽  
Gravity Load ◽  
Comparison Results ◽  
Seismic Force ◽  
Nonlinear Time History

This paper presents a simple method based on modal response spectrum analysis to compute internal forces in structural elements belonging to gravity framing not part of the seismic force resisting system (SFRS). It is required that demands on these gravity load resisting system (GLRS) be determined according to the design displacement profile of the SFRS. The proposed new method uses the fact that if the linear stiffness properties of the GLRS not part of the SFRS have negligible values compared to those of the SFRS, only the latter will provide lateral resistance. Displacements of the GLRS then correspond to those of the SFRS alone. The new method is illustrated by computing the seismic responses of a symmetric and an asymmetric multi-storey reinforced concrete building. These results are compared to those obtained from the application of the simplified analysis method proposed in the Canadian standard for the design of concrete structures. Nonlinear time history analyses are also performed to provide a benchmark for comparison. Results show that the new method can predict shear and bending moment in all members at once with ease. Therefore, this new simplified method can effectively be used to predict seismic forces in elements not considered part of the SFRS.

Adaptive Spectra-Based Pushover Procedure for Seismic Evaluation of Structures

2000 ◽  
Vol 16 (2) ◽  
pp. 367-391 ◽  
Author(s):  
Balram Gupta ◽  
Sashi K. Kunnath
Keyword(s):  
Response Spectrum ◽  
Pushover Analysis ◽  
Nonlinear Dynamic Analysis ◽  
Time History ◽  
Northridge Earthquake ◽  
Seismic Evaluation ◽  
Seismic Demands ◽  
Ground Shaking ◽  
Motion Characteristics ◽  
Nonlinear Time History

The estimation of inelastic seismic demands using nonlinear static procedures, or pushover analyses, are inevitably going to be favored by practicing engineers over nonlinear time-history methods. While there has been some concern over the reliability of static procedures to predict inelastic seismic demands, improved procedures overcoming these drawbacks are still forthcoming. In this paper, the potential limitations of static procedures, such as those recommended in FEMA 273, are highlighted through an evaluation of the response of instrumented buildings that experienced strong ground shaking in the 1994 Northridge earthquake. A new enhanced adaptive “modal” site-specific spectra-based pushover analysis is proposed, which accounts for the effect of higher modes and overcomes the shortcomings of the FEMA procedure. Features of the proposed procedure include its similarity to traditional response spectrum-based analysis and the explicit consideration of ground motion characteristics during the analysis. It is demonstrated that the proposed procedure is able to reasonably capture important response attributes, such as interstory drift and failure mechanisms, even for structures with discontinuities in strength and/or stiffness that only a detailed nonlinear dynamic analysis could predict.

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.

Seismic response analysis of steel–concrete hybrid wind turbine tower

2021 ◽  
pp. 107754632110075
Author(s):  
Junling Chen ◽  
Jinwei Li ◽  
Dawei Wang ◽  
Youquan Feng
Keyword(s):  
Wind Turbine ◽  
Response Spectrum ◽  
Ground Motions ◽  
Time History ◽  
Seismic Action ◽  
Response Spectrum Method ◽  
Spectrum Method ◽  
Wind Turbine Tower ◽  
Ground Types ◽  
Nonlinear Time History

The steel–concrete hybrid wind turbine tower is characterized by the concrete tubular segment at the lower part and the traditional steel tubular segment at the upper part. Because of the great change of mass and stiffness along the height of the tower at the connection of steel segment and concrete segment, its dynamic responses under seismic ground motions are significantly different from those of the traditional steel tubular wind turbine tower. Two detailed finite element models of a full steel tubular tower and a steel–concrete hybrid tower for 2.0 MW wind turbine built in the same wind farm are, respectively, developed by using the finite element software ABAQUS. The response spectrum method is applied to analyze the seismic action effects of these two towers under three different ground types. Three groups of ground motions corresponding to three ground types are used to analyze the dynamic response of the steel–concrete hybrid tower by the nonlinear time history method. The numerical results show that the seismic action effect by the response spectrum method is lower than those by the nonlinear time history method. And then it can be concluded that the response spectrum method is not suitable for calculating the seismic action effects of the steel–concrete hybrid tower directly and the time history analyses should be a necessary supplement for its seismic design. The first three modes have obvious contributions on the dynamic response of the steel–concrete hybrid tower.

Seismic Analysis of High Pier Three-Span Continuous Bridge

2015 ◽  
Vol 744-746 ◽  
pp. 890-893
Author(s):  
Xun Wu ◽  
Yong Lan Zhang
Keyword(s):  
Seismic Analysis ◽  
Linear Time ◽  
Time History ◽  
Response Spectra ◽  
Elastic Response ◽  
Modeling And Analysis ◽  
Continuous Beam Bridge ◽  
Comparison Results ◽  
Elastic Response Spectra ◽  
Nonlinear Time History

In this paper, SAP2000 and ANSYS software are used to modeling and analysis athree-span continuous beam bridge with high piers case study.By using differentbearing types and combinations to form different options, create two finiteelement models.Analysis dynamic characteristics ,elastic response spectra,linear time history and nonlinear time history .And focus on comparing dynamiccharacteristics of the earthquake response of the two programs .Running outputdata processing and comparison results show that the application of thedifferent parameters of the rational combination of rubber bearing basin bridgearrangement has better seismic performance.

Direct Displacement Procedure for Performance-Based Seismic Design of Mid-Rise Wood-Framed Structures

2009 ◽  
Vol 25 (3) ◽  
pp. 583-605 ◽  
Author(s):  
Wei Chiang Pang ◽  
David V. Rosowsky
Keyword(s):  
Seismic Design ◽  
Response Spectrum ◽  
Design Procedure ◽  
Time History ◽  
Time History Analysis ◽  
Nonlinear Time History Analysis ◽  
Framed Structures ◽  
History Analysis ◽  
Performance Based Seismic Design ◽  
Nonlinear Time History

This paper presents a direct displacement design (DDD) procedure that can be used for seismic design of multistory wood-framed structures. The proposed procedure is applicable to any pure shear deforming system. The design procedure is a promising design tool for performance-based seismic design since it allows consideration of multiple performance objectives (e.g., damage limitation, safety requirements) without requiring the engineer to perform a complex finite element or nonlinear time-history analysis of the complete structure. A simple procedure based on normalized modal analysis is used to convert the code-specified acceleration response spectrum into a set of interstory drift spectra. These spectra can be used to determine the minimum stiffness required for each floor based on the drift limit requirements. Specific shear walls can then be directly selected from a database of backbone curves. The procedure is illustrated on the design of two three-story ATC-63 archetype buildings, and the results are validated using nonlinear time-history analysis.

Optimization Design of Large Span Cable-Stayed Bridge in High Seismic Risk Zone

2013 ◽  
Vol 353-356 ◽  
pp. 2015-2019
Author(s):  
Zhi Hua Xiong ◽  
Yun Cheng Feng ◽  
Song Lin Song ◽  
Jiang Bo Wang
Keyword(s):  
Optimization Design ◽  
Time History ◽  
Nonlinear Time History Analysis ◽  
Seismic Safety ◽  
Seismic Demands ◽  
Large Span ◽  
Cable Stayed Bridge ◽  
History Analysis ◽  
Ductile Steel ◽  
Nonlinear Time History

To ensure seismic safety of a large span cable-stayed bridge, two alternative pylon shapes and section types were studied. Nonlinear time history analysis was performed in the context. It is found that the A-shaped pylon is much stiffener than the H-shaped pylon in terms of deformation. The steel A-shaped pylon can significantly reduce the seismic demands of the key member including tower drift and moment. A ductile steel link between towers is proposed for the optimization of design in the paper. The A-shaped reinforced concrete tower with ductile steel link was proved to be a relatively balanced plan considering engineering, aesthetic and economic factors.

Influence of Earthquake Attack Angle on Seismic Demands for Structures under Bi-Directional Ground Motions

2011 ◽  
Vol 255-260 ◽  
pp. 2330-2334 ◽  
Author(s):  
Yu Zhang ◽  
Quan Wang Li ◽  
Jian Sheng Fan
Keyword(s):  
Seismic Design ◽  
Ground Motions ◽  
Time History ◽  
Earthquake Excitation ◽  
Seismic Demands ◽  
3 Dimensional ◽  
Nonlinear Time History Analyses ◽  
Modification Factor ◽  
Structural Responses ◽  
Nonlinear Time History

The earthquake may attack the structural building from any angle, but in current seismic design codes, this type of uncertainty is seldom accounted. The uncertainty associated with the direction of earthquake excitation was considered in this paper, and its effect on structural responses was investigated. For this purpose, a simple 3-dimensional model with symmetric plan was established, which had fundamental periods ranged from 0.1s to 5.0s, and was subjected to a set of 30 ground motion pairs for which both linear and nonlinear time history analyses were performed. Analyzing results showed that, on average, the elastic roof acceleration is 32% underestimated, and the inelastic roof displacement is 18% underestimated if the variation of earthquake excitation direction is not consider. Recognizing this, a modification factor for the seismic demand was proposed thorough a statistical analysis, which guarantees a probability of 95% design safety

scholarly journals Seismic and Time History Performance of RCC Framed Buildings with and without Passive Energy Dissipators

2020 ◽  
Vol 9 (3) ◽  
pp. 2230-2240
Keyword(s):  
Base Isolation ◽  
Lateral Displacement ◽  
Response Spectrum ◽  
Time History ◽  
Base Shear ◽  
Viscous Dampers ◽  
Fluid Viscous Dampers ◽  
Seismic Force ◽  
Energy Dissipators ◽  
Lateral Displacements

Base isolation is an effective way to protect large structures from earthquake damage. It is a costly approach, as the entire structure must be supported on elastomeric or sliding bearings. Viscous dampers distributed throughout an otherwise conventional structure can achieve the same result at a significantly lower cost. Dampers are used to resist lateral forces coming on the structure. Dampers are the energy dissipating devices which also resist displacement of Reinforced Concrete (RC) buildings during an earthquake. These dampers help the structure to reduce buckling of columns thereby increasing the stiffness of the structure. During earthquakes, multi-storeyed buildings get damaged and as a result, large deformation occurs. Dampers reduce vibration and deformation of structural elements during an earthquake. Retrofitting buildings with fluid viscous dampers (FVDs) can improve Interstorey drifts and floor accelerations. In the present study, an RC framed building is modelled and analysed under Southern Sumatra and Chile earthquakes to evaluate the performance of the structure and its elements with and without energy dissipators. For the study, a model (G+19) with and without energy dissipators is modelled in ETABS. The seismic force is applied based on the time history data of the models pertaining to Southern Sumatra and Chile Earthquake. Response Spectrum analysis has been carried out to find the lateral displacements, storey shear and Base shear for the model with and without dampers. The lateral displacement, storey drift, storey shear and Base shear are found to less for the model with Linear FVDs when compared to the model with Non-Linear FVDs and without FVDs.

Modal Superposition Technique to Predict the Seismic-Pushover Load for Jacket-Type Structures

2002 ◽  
Author(s):  
Kanthi Srirengan ◽  
Partha Chakrabarti ◽  
Rupak Ghosh
Keyword(s):  
Response Spectrum ◽  
Pushover Analysis ◽  
Time History ◽  
Nonlinear Time History Analysis ◽  
Elastic Response ◽  
Preliminary Evaluation ◽  
Inelastic Behavior ◽  
Linear Superposition ◽  
Linear Elastic ◽  
Nonlinear Time History

Two novel methods namely the Dominant Modes method and the All Modes method to predict the seismic-pushover load for the jacket-type structures are presented. Both of these methods are based on the linear superposition of the modal reactions. As a preliminary evaluation, the linear elastic response of a jacket structure subjected to seismic-pushover loads is compared with that obtained from the response spectrum analysis. Furthermore, the nonlinear inelastic behavior obtained from the seismic-pushover analysis is compared with that obtained from the nonlinear time-history analysis, for a portal frame subjected to El Centro earthquake motion. When more than one mode is dominant in an excitation direction, both the linear elastic and the nonlinear inelastic responses obtained using the loads generated from the All Modes method are representative of the reference solutions.

scholarly journals Seismic Demands in Column Base Connections of Steel Moment Frames

2018 ◽  
Vol 34 (3) ◽  
pp. 1383-1403 ◽  
Author(s):  
Pablo Torres-Rodas ◽  
Farzin Zareian ◽  
Amit Kanvinde
Keyword(s):  
Time History ◽  
Base Plate ◽  
Moment Frames ◽  
Steel Moment Frames ◽  
Seismic Demands ◽  
Axial Forces ◽  
Plate Connections ◽  
Nonlinear Time History ◽  
Base Connections ◽  
Column Base

Methods for the seismic design of base connections in steel moment frames are well-developed and routinely utilized by practicing engineers. However, design loads for these connections are not verified by rigorous analysis. This knowledge gap is addressed through nonlinear time history simulations using design-level seismic excitation that interrogate demands in column base connections in 2-, 4-, 8-, and 12-story steel moment frames, featuring base connections that reflect current U.S. practice. The results indicate that: (1) for exposed base plate connections, lower bound (rather than peak) estimates of axial compression are suitable for design because higher axial forces increase connection strength by delaying base plate uplift; (2) even when designed as pinned (as in low-rise frames), base connections carry significant moment, which can be estimated only through accurate representation of base flexibility; and (3) the failure of embedded base connections is controlled by moment, which may be estimated either through overstrength or capacity-based calculations.

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