Assessment on the deflection amplification factor of steel buckling-restrained bracing frames

2021 ◽  
pp. 136943322110439
Author(s):  
Mussa Mahmoudi ◽  
Mohammad Jalili Sadr Abad
Keyword(s):  
Earthquake Engineering ◽  
Amplification Factor ◽  
Time History ◽  
Braced Frames ◽  
Ground Motion Simulation ◽  
Nonlinear Time History Analyses ◽  
Deflection Amplification Factor ◽  
Ductility Capacity ◽  
Nonlinear Time History ◽  
Factor C

Researchers in the field of earthquake engineering are always looking for new ways to improve the seismic behavior of structures. The buckling-restrained brace (BRB) is one of these exciting innovations that are employed to increase the ductility capacity of traditional steel braced frames. Understanding the nonlinear response of these novel systems in estimating maximum displacements due to an earthquake has been of significant importance for structural designers. Accordingly, this research is carried out to study of deflection amplification factor ( C d) in BRBs, which have recently been presented in seismic design provisions as one of the seismic lateral-resisting systems. To this end, five 3-, 5-, 7-, 10-, and 15-story BRBs are modeled in the software framework of OpenSees. Ground motion simulation is performed by selecting several scaled earthquake records, and the values of elastic and ultimate displacements of structural systems are computed through pushover and nonlinear time-history analyses. The results showed that the deflection amplification factor suggested within famous building codes (such as ASCE-7-16) compared to the obtained values is, in some cases, for certainty; conversely, it is underestimated under some conditions. In fact, the findings indicate that the magnitude of C d in these systems is strongly related to the height of the building.

scholarly journals Quasi-static tests on RC building columns strengthened with CFRP

2021 ◽  
Vol 73 (08) ◽  
pp. 805-818
Keyword(s):  
Earthquake Engineering ◽  
Time History ◽  
Shear Strengthening ◽  
Static Tests ◽  
Flexural Strengthening ◽  
Strength Capacity ◽  
Rc Building ◽  
Carbon Fibre Reinforced Polymers ◽  
Ductility Capacity ◽  
Nonlinear Time History

To explore the possibilities and benefits of using CFRP (Carbon Fibre Reinforced Polymers) in strengthening RC building columns, quasi-static tests (compression and bending) were carried out at the Institute of Earthquake Engineering and Engineering Seismology - IZIIS, Skopje by variation of concrete class, reinforcement percentage and by using various strengthening technologies. Some recommendations and outcomes regarding the approach, technology and conclusions drawn from practical application of these materials, are given. Based on the analysis of values obtained from nonlinear static and nonlinear time history analyses, it can be concluded that the ductility capacity for displacement of model strengthened with CFRP is greater by 60 %, while its strength capacity is greater by 7.7 % when compared to the values obtained for the model without CFRP. It can generally be concluded that CFRP systems are a very practical tool for strengthening and retrofitting concrete structures, as they can extensively improve flexural strengthening, shear strengthening, column confinement, and ductility.

scholarly journals Evaluation of seismic performance measures for MDOF RC structures subjected to simulated and real ground motions

2020 ◽  
Vol 323 ◽  
pp. 02003
Author(s):  
Shaghayegh Karimzadeh ◽  
Aysegul Askan ◽  
Ahmet Yakut
Keyword(s):  
Ground Motion ◽  
Seismic Performance ◽  
Performance Measures ◽  
Ground Motions ◽  
Time History ◽  
Motion Simulation ◽  
Ground Motion Simulation ◽  
Nonlinear Time History Analyses ◽  
Nonlinear Time History ◽  
Simulated Ground Motions

Nonlinear time history analyses of structures require full time series of ground motion records. For regions with sparse seismic networks or potential large earthquakes, ground motion simulation has gained more attention in recent years. Simulated records are required to be generated using regional input dataset and then verified against existing recorded ground motions of past events. To use simulated ground motions in engineering applications, estimation of reliable seismic demand parameters is essential. In this study, the real and simulated records of the 2009 L’Aquila, Italy earthquake with (Mw=6.3) are investigated for their use in engineering practice. In the first step, misfits are evaluated for alternative seismological measures (peak values, duration and frequency as well as energy content of the time histories). Next, varying multi-degree-of-freedom reinforced concrete structures with different number of stories are selected. Numerical models of the structures are performed in the OpenSees platform. Seismic performance measures in terms of inter-story drift ratio for the selected structures are assessed through nonlinear time history analyses for both the real and simulated ground motions. Then, the misfits are estimated in terms of structural demand parameters. Results reveal a good fit between the seismological and engineering demand misfits for the selected ground motion simulation approaches.

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 Seismic Performance of a Green Roof Structure

2021 ◽  
Vol 13 (8) ◽  
pp. 4278
Author(s):  
Svetlana Tam ◽  
Jenna Wong
Keyword(s):  
Green Roof ◽  
Time History ◽  
Green Roofs ◽  
Moment Frame ◽  
Steel Moment Frame ◽  
Roof Structure ◽  
Nonlinear Time History Analyses ◽  
Vegetated Roofs ◽  
Nonlinear Time History ◽  
The Impact

Sustainability addresses the need to reduce the structure’s impact on the environment but does not reduce the environment’s impact on the structure. To explore this relationship, this study focuses on quantifying the impact of green roofs or vegetated roofs on seismic responses such as story displacements, interstory drifts, and floor level accelerations. Using an archetype three-story steel moment frame, nonlinear time history analyses are conducted in OpenSees for a shallow and deep green roof using a suite of ground motions from various distances from the fault to identify key trends and sensitivities in response.

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 A Wavelet-based Approach for Truncating Pulse-like Records

2021 ◽  
Author(s):  
Vicky Dimakopoulou ◽  
Michalis Fragiadakis ◽  
Ioannis Taflampas
Keyword(s):  
Ground Motion ◽  
Near Field ◽  
Time History ◽  
Response Spectra ◽  
Degree Of Freedom ◽  
Seismic Performance Assessment ◽  
Analysis And Design ◽  
Nonlinear Time History Analyses ◽  
Ground Motion Records ◽  
Nonlinear Time History

Abstract The seismic performance assessment of structures using truncated pulse-like ground motion records is discussed. It is shown that it is possible to truncate pulse-like signals using a novel wavelet-based definition that identifies the duration of the predominant velocity pulse. The truncated time history can efficiently reproduce the increased seismic demand that near-field records typically produce. Substituting the original ground motion with the truncated signal, significantly accelerates structural analysis and design. The truncated signal is the part of the original accelerogram that coincides with the duration of the predominant pulse, which is identified using a wavelet-based procedure, previously proposed by the authors. Elastic and inelastic response spectra and nonlinear time history analyses for SDOF (single-degree-of-freedom) systems are first studied. Subsequently a nine-storey steel frame is examined in order to demonstrate the performance of the proposed approach on a multiple-degree-of-freedom system. The proposed approach is found very efficient for pulse-like ground motions, while it is also sufficient for many records that are not characterized as such.

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