scholarly journals Spectral Assessment of the Effects of Base Flexibility on Seismic Demands of a Structure

2016 ◽  
Vol 2016 ◽  
pp. 1-8
Author(s):  
J. Borzouie ◽  
J. G. Chase ◽  
G. A. MacRae ◽  
G. W. Rodgers ◽  
G. C. Clifton
Keyword(s):  
Lateral Displacement ◽  
Time History ◽  
Nonlinear Time History Analysis ◽  
Seismic Demand ◽  
Rotational Stiffness ◽  
Earthquake Excitation ◽  
Seismic Demands ◽  
Fixed Base ◽  
Linear And Nonlinear ◽  
Nonlinear Time History

Base flexibility of structures changes and can increase the demands on structural elements during earthquake excitation. Such flexibility may come from the base connection, foundation, and soil under the foundation. This research evaluates the effects of column base rotational stiffness on the seismic demand of single storey frames with a range of periods using linear and nonlinear time history analysis. The base rotational stiffness ranges considered are based on previous studies considering foundation and baseplate flexibility. Linear and nonlinear spectral analyses show that increasing base flexibility generally increases frame lateral displacement and top moment of the column. Furthermore, moments at the top of the columns and the nonlinear base rotation may also increase with increasing base flexibility, especially for shorter period structures. Since many commonly used baseplate connections may be categorized as being semirigid, it is essential to design and model structures using realistic base rotational stiffness rather than simply use a fixed base assumption. The overall results also illustrate the range of increased seismic demand as a function of normalized rotational stiffness and structural period for consideration in design.

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.

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

A Drift Pushover Analysis Procedure for Estimating the Seismic Demands of Buildings

2014 ◽  
Vol 30 (4) ◽  
pp. 1601-1618 ◽  
Author(s):  
Arash Sahraei ◽  
Farhad Behnamfar
Keyword(s):  
Lateral Displacement ◽  
Plastic Hinge ◽  
Pushover Analysis ◽  
Time History ◽  
Relative Displacement ◽  
Analysis Procedure ◽  
New Method ◽  
Nonlinear Time History Analysis ◽  
Displacement Based ◽  
Nonlinear Time History

Relative displacement is a parameter that has a very high correlation with damage. The objective of this article is to develop an analysis procedure founded on the displacement-based seismic design methodology. Generalized interstory drift spectrum is applied as an essential tool in this new method called drift pushover analysis. In order to evaluate the behavior of structures, three demand parameters—lateral displacement, story shear, and plastic hinge rotation—are computed with conventional pushover analysis (CPA), modal pushover analysis (MPA), and drift pushover analysis (DPA), and are compared with those of the nonlinear time history analysis (NTA). It is observed that the new method, DPA, predicts the peak response measures more precisely and with less effort than the other nonlinear pushover procedures investigated in this study.

scholarly journals Response control of structures under Seismic and Blast induced ground motions

2021 ◽  
Vol 309 ◽  
pp. 01137
Author(s):  
Vamshisheela Siripuram ◽  
Atulkumar Manchalwar
Keyword(s):  
Base Isolation ◽  
Ground Motions ◽  
Time History ◽  
Nonlinear Time History Analysis ◽  
Base Shear ◽  
Rubber Bearing ◽  
Lead Rubber Bearing ◽  
Fixed Base ◽  
Isolation Device ◽  
Nonlinear Time History

In the present paper an investigation is carried out to evaluate the efficiency of Base Isolation device in a building subjected to both seismic and blast induced ground motions. A 5-story building is modelled with different story stiffness and floor masses is considered in this study. In SAP 2000 software two buildings, one with fixed base and the other with isolated base are designed and nonlinear time history analysis is conducted. The structural responses of these two models subjected to four recorded earthquakes and four different blast ground accelerations is compared in this study. The base isolated device such as lead/rubber bearing have proved to be effective in reducing the base Shear and Top story acceleration, and also increase in Hysteresis energy in the base isolated structure subjected to seismic and blast vibrations.

Sensitivity analysis of the influence of ground motion intensity levels on the seismic behavior of steel frames in assessment of the target displacement considering near-fault effects

2020 ◽  
Vol 47 (4) ◽  
pp. 470-486
Author(s):  
Alireza Esfahanian ◽  
Ali Akbar Aghakouchak
Keyword(s):  
Ground Motions ◽  
Steel Frames ◽  
Time History ◽  
Time History Analysis ◽  
Nonlinear Time History Analysis ◽  
Seismic Demands ◽  
Near Fault ◽  
History Analysis ◽  
Nonlinear Time History ◽  
Far Fault

Nonlinear time-history analysis conducted as part of a performance-based seismic design approach often require that the ground motion records are selected and then scaled to a specified level of seismic intensity. In such analyses, besides an adequate structural model, a set of acceleration time-series is needed as the most realistic representation of the seismic action. In this paper, the effects of scaling procedure on seismic demands of steel frames are investigated. To this, two special steel moment-resisting frames with considerable higher mode effects, and two sets of ground motions, including near-fault and far-fault motions are considered. Moreover, three scaling procedures are introduced for performing nonlinear dynamic time-history analysis of structures. Among different demands, lateral roof displacement and interstory drift are selected as seismic demands. The height-wise distribution of demands shows that the inelastic seismic demands of the near-fault pulse-like ground motions differ considerably from those of far-fault ones. These results show that the story drifts are mostly larger for far-fault motions in the upper story levels in comparison to near-fault records and in the lower floors, the reverse is true. Thus, the scaling procedures directly affect the results of seismic demands and choosing different methods would result in varying responses. Moreover, a low-cost and fairly effective procedure is proposed to estimate the target displacement demands of buildings from response-spectrum analyses, considering near-fault effects. The precision of this method is verified by nonlinear time-history analysis results, as the benchmark solution, and acceptable improvements have been achieved.

Applicability of Modal Pushover Analysis on Bridges

2011 ◽  
Vol 255-260 ◽  
pp. 806-810
Author(s):  
Biao Wei ◽  
Qing Yuan Zeng ◽  
Wei An Liu
Keyword(s):  
Seismic Analysis ◽  
Pushover Analysis ◽  
Time History ◽  
Seismic Demand ◽  
Seismic Demands ◽  
Modal Pushover Analysis ◽  
History Analysis ◽  
Bridge Structures ◽  
Scope Of Application ◽  
Modal Pushover

Taking one irregular continuous bridge as an example, modal pushover analysis (MPA) has been conducted to judge whether it would be applicable for seismic analysis of irregular bridge structures. The bridge’s seismic demand in the transverse direction has been determined through two different methods, inelastic time history analysis (ITHA) and MPA respectively. The comparison between those two results indicates that MPA would be suitable only for bridges under elastic or slightly damaged state. Finally, some modifications are used to improve the MPA’s scope of application, and the results illustrate that the adapted MPA will be able to estimate bridges’ seismic demands to some extent.

Probabilistic Peak Displacement Analysis of Bridge Structures with P-Δ Effect

2013 ◽  
Vol 405-408 ◽  
pp. 1674-1677
Author(s):  
Bo Yu ◽  
Di Liu ◽  
Lu Feng Yang
Keyword(s):  
Time History ◽  
Dynamic Responses ◽  
Nonlinear Time History Analysis ◽  
Bridge Structure ◽  
Vibration Period ◽  
Peak Displacement ◽  
Sdof System ◽  
Bridge Structures ◽  
Performance Based Seismic Design ◽  
Nonlinear Time History

Peak displacement is one of the most important parameters for the performance based seismic design of bridge structure, while the peak displacement is often significantly impacted by the P-Δ effect. In this study, the influence of the P-Δ effect on the statistics of peak displacement of bridge structure was quantificationally investigated based on a series of nonlinear time-history analysis. The bridge structure was idealized as the single degree of freedom (SDOF) system and the hysteretic behaviour was represented by the improved Bouc-Wen model. The statistic analysis was implemented based on the inelastic dynamic responses of the SDOF system under 69 selected earthquake records. The results show that the P-Δ effect has significant impact on the mean and dispersion of peak displacement of bridge structures, especially if the normalized yield strength and the natural vibration period are small.

scholarly journals Performance of an Existing Reinforced Concrete Building Designed in Accordance to Older Indonesian Seismic Code: A Case Study for a Hotel in Kupang, Indonesia

2018 ◽  
Vol 20 (1) ◽  
pp. 35
Author(s):  
Pamuda Pudjisuryadi ◽  
Benjamin Lumantarna ◽  
Ryan Setiawan ◽  
Christian Handoko
Keyword(s):  
Plastic Hinge ◽  
Time History ◽  
Nonlinear Time History Analysis ◽  
Seismic Load ◽  
Ground Acceleration ◽  
Seismic Code ◽  
Damage Level ◽  
History Analysis ◽  
Nonlinear Time History ◽  
Seismic Hazard Map

The recent seismic code SNI 1726-2012 is significantly different compared to the older code SNI 1726-2002. The seismic hazard map was significantly changed and the level of maximum considered earthquake was significantly increased. Therefore, buildings designed according to outdated code may not resist the higher demand required by newer code. In this study, seismic performance of Hotel X in Kupang, Indonesia which was designed based on SNI-1726-2002 is investigated. The structure was analyzed using Nonlinear Time History Analysis. The seismic load used was a spectrum consistent ground acceleration generated from El-Centro 18 May 1940 North-South component in accordance to SNI 1726-2012. The results show that Hotel X can resist maximum considered earthquake required by SNI 1726-2012. The maximum drift ratio is 0.81% which is lower than the limit set by FEMA 356-2000 (2%). Plastic hinge damage level is also lower than the allowance in ACMC 2001.

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