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.

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 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.

Effect of LRB Position for Vibration Reduction System of Self-Anchored Cable-Stayed Suspension Bridge

2014 ◽  
Vol 974 ◽  
pp. 346-349
Author(s):  
Feng Miao
Keyword(s):  
Earthquake Engineering ◽  
Vibration Reduction ◽  
Time History ◽  
Suspension Bridge ◽  
Nonlinear Time History Analysis ◽  
Engineering Practice ◽  
Viscous Damper ◽  
Reduction System ◽  
History Analysis ◽  
Nonlinear Time History

Larger displacement and inter-force response of the structure will be produced when self-anchored cable-stayed suspension bridge in longitudinal earthquake. Engineering practice proved that the viscous damper has obviously damping effect for structure. For the vibration reduction system of self-anchored cable-stayed suspension bridge, whose main tower is set viscous damper. This essay does the nonlinear time history analysis under the longitudinal earthquake about the vibration reduction system that considering the LRB putted in different location. Compared with the damping system that only set viscous damper, analysis results show that inter-force and displacement of control section and control node are reduced greatly in hybrid vibration control.

Investigation into the Effects of Foundation Uplift on Simplified Seismic Design Procedures

2006 ◽  
Vol 22 (3) ◽  
pp. 663-692 ◽  
Author(s):  
Chad Harden ◽  
Tara Hutchinson ◽  
Mark Moore
Keyword(s):  
Earthquake Engineering ◽  
Numerical Models ◽  
Time History ◽  
Lateral Force ◽  
Winkler Foundation ◽  
Numerical Comparison ◽  
Design Strength ◽  
Seismic Demands ◽  
Equivalent Sdof System ◽  
Nonlinear Time History

Uplifting of and yielding below shallow foundations supporting rigid lateral force–resisting elements can provide additional nonlinearity into a system's overall force-deformation behavior. While this nonlinearity may be advantageous, potentially reducing seismic demands, displacement compatibility may result in overstress of lateral and/or gravity-resisting elements. Incorporating this balance of benefit versus consequence in structural design is one goal of performance-based earthquake engineering (PBEE). There are a variety of approaches in design codes for estimating seismic demands and incorporating “performance” as a design goal. Such methods generally account for the displacement of an equivalent SDOF system by reducing the design strength, however, not explicitly for the case of foundation uplift. To address this shortcoming, this paper investigates the relationship between the strength ratio R and the displacement ratio C1 using the beam on nonlinear Winkler foundation (BNWF) concept. Numerical models were constructed considering a range of soil-structure natural periods and a range of design R values. Nineteen ground motions with a broad range of characteristics are used to conduct nonlinear time-history analyses. Results from these simulations indicate that current suggestions for C1- R relations are highly unconservative when uplifting foundations are anticipated. Revised C1- R relations for uplifting foundations are presented and an example numerical comparison provided.

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.

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.

scholarly journals Nonlinear time-history earthquake analysis for steel frames

Heliyon ◽  
2021 ◽  
Vol 7 (8) ◽  
pp. e06832
Author(s):  
Phu-Cuong Nguyen ◽  
Thanh-Tuan Tran ◽  
Trong Nghia-Nguyen
Keyword(s):  
Steel Frames ◽  
Time History ◽  
Nonlinear Time History

scholarly journals Displacement Demand for Nonlinear Static Analyses of Masonry Structures: Critical Review and Improved Formulations

Buildings ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 118
Author(s):  
Gabriele Guerrini ◽  
Stylianos Kallioras ◽  
Stefano Bracchi ◽  
Francesco Graziotti ◽  
Andrea Penna
Keyword(s):  
Time History ◽  
Nonlinear Static Analysis ◽  
Equivalent Linearization ◽  
Eurocode 8 ◽  
Masonry Structures ◽  
Equivalent Viscous Damping ◽  
Inelastic Displacement ◽  
N2 Method ◽  
Nonlinear Static ◽  
Nonlinear Time History

This paper discusses different formulations for calculating earthquake-induced displacement demands to be associated with nonlinear static analysis procedures for the assessment of masonry structures. Focus is placed on systems with fundamental periods between 0.1 and 0.5 s, for which the inelastic displacement amplification is usually more pronounced. The accuracy of the predictive equations is assessed based on the results from nonlinear time-history analyses, carried out on single-degree-of-freedom oscillators with hysteretic force–displacement relationships representative of masonry structures. First, the study demonstrates some limitations of two established approaches based on the equivalent linearization concept: the capacity spectrum method of the Dutch guidelines NPR 9998-18, and its version outlined in FEMA 440, both of which overpredict maximum displacements. Two codified formulations relying on inelastic displacement spectra are also evaluated, namely the N2 method of Eurocode 8 and the displacement coefficient method of ASCE 41-17: the former proves to be significantly unconservative, while the latter is affected by excessive dispersion. A non-iterative procedure, using an equivalent linear system with calibrated optimal stiffness and equivalent viscous damping, is then proposed to overcome some of the problems identified earlier. A recently developed modified N2 formulation is shown to improve accuracy while limiting the dispersion of the predictions.

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