scholarly journals Proposed development of a damage-resisting Eccentrically Braced Frame with rotational active links

2011 ◽  
Vol 44 (2) ◽  
pp. 99-107 ◽  
Author(s):  
Mahbub H. Khan ◽  
G. Charles Clifton
Keyword(s):  
Time History ◽  
Damage Threshold ◽  
Integration Time ◽  
Maximum Displacement ◽  
Braced Frame ◽  
Axial Extension ◽  
Average Maximum ◽  
Strength And Stiffness ◽  
Ductility Capacity ◽  
Active Link

Eccentrically Braced Frames (EBFs) are widely used seismic-resisting systems, as they allow both strength and stiffness to be optimised while providing good ductility capacity. However, in theory they have a low damage threshold in severe earthquakes and post-earthquake repair of conventional EBFs will be difficult and expensive. This paper presents the Numerical Integration Time-History (NITH) analysis of two ten storey EBF buildings; one with a conventional active link and the other with a new form of low damage active link based on rotational sliding bolted plates. The low damage active link can be designed to allow rotation only, or to allow both rotation and axial extension. The conventional active link response in terms of displacement, rotation and inelastic demand was well within the range of the rotational active links under the records considered. The analysis shows that average maximum displacement of the building and rotation of the link for both the rotational and the rotational+extension active links was almost identical. The extension of the rotational active link permitting axial extension was less than 1.5 mm. Axial load demands on the collector beams and braces were similar in the case all three active links. It can be concluded from the analysis that the rotational active link with extension is not required, as the lateral extensions can be accommodated within the rotational plates with nominal clearances in the bolt holes to accommodate the lateral extension.

Seismic Ratchetting of Single-Degree-of-Freedom Steel Bridge Columns

2018 ◽  
Vol 763 ◽  
pp. 295-300 ◽  
Author(s):  
Khaled Saif ◽  
Chin Long Lee ◽  
Trevor Yeow ◽  
Gregory A. MacRae
Keyword(s):  
Time History ◽  
Steel Structures ◽  
Bridge Columns ◽  
Steel Bridge ◽  
Axial Loads ◽  
Maximum Displacement ◽  
Residual Displacements ◽  
Average Maximum ◽  
Force Reduction ◽  
Nonlinear Time History

Nonlinear time history analyses of SDOF bridge columns with elasto-plastic flexural behaviour which are subject to eccentric gravity loading are conducted to quantify the effect of ratchetting. Peak and residual displacements were used as indicators of the degree of ratchetting. The effects of member axial loads and design force reduction factors were also investigated. It was shown that displacement demands increased with increasing eccentric moment. For eccentric moment of 30% of the yield moment, the average maximum and residual displacements increase by 4.2 and 3.8 times the maximum displacement, respectively, which the engineers calculate using static methods without considering ratchetting effect. Design curves for estimating the displacement demands for different eccentric moments are also developed. The current NZ1170.5 (2016) provisions were found to be inadequate in estimating the maximum displacement for steel structures, and hence, new provisions for steel structures should be presented.

Improving the torsional response of asymmetric buildings with self-centering controlled rocking steel braced frame system

2022 ◽  
pp. 136943322110509
Author(s):  
Maryam Hafezi ◽  
Armin Aziminejad ◽  
Mohammad Reza Mansoori ◽  
Mahmood Hosseini ◽  
Abdolreza Sarvghad Moghadam
Keyword(s):  
Center Of Mass ◽  
Asymmetric Structure ◽  
Maximum Displacement ◽  
Braced Frame ◽  
Asymmetric Buildings ◽  
Frame System ◽  
Strength And Stiffness ◽  
Ground Motion Records ◽  
Energy Absorbing ◽  
Steel Braced Frame

Self-centering controlled rocking steel braced-frame (SC-CR-SBF) is proposed as an earthquake-resistant system with low damage. Pre-stressed vertical strands provide a self-centering mechanism in the system and energy absorbing fuses restrict maximum displacement. Presence of asymmetry in structures can highlight the advantages of employing this structural system. Moreover, these days designing and constructing asymmetric and irregular structures is inevitable and as a result of architectural attractiveness and requirements of different functions of buildings, they are of great importance. Consequently, in these types of structures in order to minimize seismic responses, particular measures should be taken into consideration. Proper distribution of strength and stiffness throughout the plan of structures with self-centering systems can play a considerable role in resolving problems associated with asymmetry in these structures. In this study, the asymmetric buildings with 10% and 20% mass eccentricities and having different arrangements of centers were simulated. The models were analyzed under a set of 22 bidirectional far-field ground-motion records and corresponding responses of maximum roof drift, acceleration and rotation of the roof diaphragms of the structures with different arrangements of the center of mass, stiffness and strength were computed and studied. Results show that proper distribution of stiffness and strength throughout the plan of the structures with SC-CR-SBF system reduces the maximum roof drift as well as the rotation of the roof diaphragm. With appropriate arrangement of the centers, maximum drift response of the asymmetric structure decreases as much as roughly 20% and the ratio of the maximum drift response of the asymmetric structure to the response of the similar symmetric structure with the same overall stiffness and strength was 1.1. In other words, maximum drift response of the asymmetric structure with SC-CR-SBF system is acceptably close to the one for the symmetric building.

Seismic evaluation of single-storey steel buildings

1999 ◽  
Vol 26 (4) ◽  
pp. 379-394 ◽  
Author(s):  
M S Medhekar ◽  
DJL Kennedy
Keyword(s):  
Seismic Performance ◽  
Response Spectrum ◽  
Time History ◽  
Analytical Models ◽  
Steel Buildings ◽  
Concentrically Braced Frames ◽  
Braced Frame ◽  
Seismic Zones ◽  
Concentrically Braced Frame ◽  
Concentrically Braced

The seismic performance of single-storey steel buildings, with concentrically braced frames and a roof diaphragm that acts structurally, is evaluated. The buildings are designed in accordance with the National Building Code of Canada 1995 and CSA Standard S16.1-94 for five seismic zones in western Canada with seismicities ranging from low to high. Only frames designed with a force modification factor of 1.5 are considered. Analytical models of the building are developed, which consider the nonlinear seismic behaviour of the concentrically braced frame, the strength and stiffness contributions of the cladding, and the flexibility, strength, and distributed mass of the roof diaphragm. The seismic response of the models is assessed by means of a linear static analysis, a response spectrum analysis, a nonlinear static or "pushover" analysis, and nonlinear dynamic time history analyses. The results indicate that current design procedures provide a reasonable estimate of the drift and brace ductility demand, but do not ensure that yielding is restricted to the braces. Moreover, in moderate and high seismic zones, the roof diaphragm responds inelastically and brace connections are overloaded. Recommendations are made to improve the seismic performance of such buildings.Key words: analyses, concentrically braced frame, dynamic, earthquake, flexible diaphragm, low-rise, nonlinear, seismic design, steel.

scholarly journals Implementation of the structural performance factor (Sp) within a displacement-based design framework

2018 ◽  
Vol 51 (3) ◽  
pp. 159-165 ◽  
Author(s):  
Dion Marriott
Keyword(s):  
Response Spectrum ◽  
Time History ◽  
Structural Performance ◽  
Integration Time ◽  
Design Framework ◽  
Base Shear ◽  
Structural Behaviour ◽  
Performance Factor ◽  
Design Response Spectrum ◽  
Displacement Based

This paper discusses the application of the Structural Performance factor (SP) within a Direct Displacement-Based Design framework (Direct-DBD). As stated within the New Zealand loadings standard, NZS1170.5:2004 [1], the SP factor is a base shear multiplier (reduction factor) for ductile structures, i.e. as the design ductility increases, the SP factor reduces. The SP factor is intended to acknowledge the better-than-expected structural behaviour of ductile systems (both strength, and ductility capacity) by accounting for attributes of response that designers are unable to reliably estimate. The SP factor also recognizes the less dependable seismic performance of non-ductile structures, by permitting less of a reduction (a larger SP factor) for non-ductile structures. Within a traditional force-based design framework the SP factor can be applied to either the design response spectrum (a seismic hazard/demand multiplier), or as a base shear multiplier at the end of design (structural capacity multiplier) – either of these two approaches will yield an identical design in terms of the required design base shear and computed ULS displacement/drift demands. However, these two approaches yield very different outcomes within a Direct-DBD framework – in particular, if SP is applied to the seismic demand, the design base shear is effectively multiplied by (SP)2 (i.e. a two-fold reduction). This paper presents a “DBD-corrected” SP factor to be applied to the design response spectrum in Direct-DBD in order to achieve the intent of the SP factor as it applies to force-based design. The proposed DBD-corrected SP factor is attractive in that it is identical to the SP relationship applied to the elastic site hazard spectrum C(T) for numerical integration time history method of analysis within NZS 1170.5:2004 [1], SP,DDBD = (1+SP)/2.

scholarly journals Plastic hinge location in columns of steel frames subjected to seismic actions

2008 ◽  
Vol 41 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Brian H. H. Peng ◽  
Gregory A. MacRae ◽  
Warren R. Walpole ◽  
Peter Moss ◽  
Rajesh Dhakal ◽  
...  
Keyword(s):  
Axial Force ◽  
Plastic Hinge ◽  
Time History ◽  
Steel Structure ◽  
Braced Frames ◽  
Moment Frames ◽  
Eccentrically Braced Frames ◽  
Moment Connection ◽  
History Analysis ◽  
Active Link

Several steel structure standards around the world contain an equation to encourage any column flexural yielding during earthquake shaking to occur at the column ends, rather than along the column length. The accuracy of these equations and their applicability to columns of both moment frames and braced frames are examined in this paper. It is shown, using an analytical procedure developed from first principles considering the reduction in member stiffness from axial force due to geometric and material nonlinearity, that the existing code equations are conservative. Less conservative empirical equations are developed based on the analysis results. It is found that these equations are applicable to frames with a braced connection, rather than a moment connection into the column. Time-history analysis of eccentrically-braced frames with inverted V-bracing, where the active link occurs at the centre of the beam, is carried out. The likely column end moment ratio needed for the new equations is determined. The analysis also shows that yielding often did not occur in the bottom story columns during earthquake excitations. A simple check is proposed to relate the axial force limit and the design drift to flexural yielding of columns which can be used in conjunction with the proposed equations.

scholarly journals Seismic Performance of Multistorey RC Frame Building With The Soft Storey and Masonry Infill

2021 ◽  
pp. 650-656
Author(s):  
Kugan K ◽  
Mr. Nandha Kumar P ◽  
Premalath J
Keyword(s):  
Time History ◽  
Seismic Loading ◽  
Rc Frame ◽  
Base Shear ◽  
Maximum Displacement ◽  
Soft Storey ◽  
Masonry Infills ◽  
Frame Building ◽  
History Analysis ◽  
Rc Frame Building

In this study, four geometrically similar frames having different configurations of masonry infills, has been investigated. In this article attempts are made to explain the factors that impact the soft storey failure in a building are compared with different type of infill. That is Four models like RC bare frame, RC frame with brick mansonry infill, RC frame with brick infill in all the storeys exept the firstsoft storey, RC frame with inverted V bracing in the soft storey. Time history analysis has been carried out for a G+8 multistoried building to study the soft storey effect at different floor levels using E tabs software. The behavior of RC framed building with soft storey under seismic loading has been observed in terms of maximum displacement ,maximum storey drift, base shear and storey stiffness as considered structure.

Pseudodynamic Test of a Deficient RC Frame Strengthened with Buckling Restrained Braces

2019 ◽  
Vol 35 (3) ◽  
pp. 1163-1187 ◽  
Author(s):  
Ramazan Ozcelik ◽  
Elif Firuze Erdil
Keyword(s):  
Time History ◽  
Shear Capacity ◽  
Test Method ◽  
Nonlinear Time History Analysis ◽  
Rc Frame ◽  
Test Results ◽  
Base Shear ◽  
Braced Frame ◽  
Pseudodynamic Test ◽  
Buckling Restrained Braces

Three story–three bay reinforced concrete (RC) frames with and without chevron braces were tested using the continuous pseudodynamic test method. New steel–concrete composite lateral load–carrying members called Buckling Restrained Braces (BRBs) were used as chevron brace members while retrofitting the RC frame. The BRBs were fitted to the interior span of the RC frame by using anchorage rods. The chevron braced frame was observed to be effective in controlling interstory drift. The test results indicated that retrofitting with BRBs was beneficial in resisting deformation without significant damage under simulated ground motions. Furthermore, significant yielding that occurred on the core plate of the BRBs enabled the braced frame to dissipate energy induced by dynamic loading. The test results were compared with the results of the nonlinear time-history analysis. The analysis results were capable of estimating the base shear capacity and displacement demands with reasonable accuracy.

An Adaptive Multiscaling Approach for Reducing Computation Time in Simulations of Articulated Biopolymers

2019 ◽  
Vol 14 (5) ◽  
Author(s):  
Ashley Guy ◽  
Alan Bowling
Keyword(s):  
Computational Cost ◽  
Time History ◽  
Computation Time ◽  
Coarse Graining ◽  
Integration Time ◽  
Dynamic Simulations ◽  
Equivalent Time ◽  
Time Histories ◽  
Time Required ◽  
Computational Resources

Microscale dynamic simulations can require significant computational resources to generate desired time evolutions. Microscale phenomena are often driven by even smaller scale dynamics, requiring multiscale system definitions to combine these effects. At the smallest scale, large active forces lead to large resultant accelerations, requiring small integration time steps to fully capture the motion and dictating the integration time for the entire model. Multiscale modeling techniques aim to reduce this computational cost, often by separating the system into subsystems or coarse graining to simplify calculations. A multiscale method has been previously shown to greatly reduce the time required to simulate systems in the continuum regime while generating equivalent time histories. This method identifies a portion of the active and dissipative forces that cancel and contribute little to the overall motion. The forces are then scaled to eliminate these noncontributing portions. This work extends that method to include an adaptive scaling method for forces that have large changes in magnitude across the time history. Results show that the adaptive formulation generates time histories similar to those of the unscaled truth model. Computation time reduction is consistent with the existing method.

Floor Spectra Estimates for an Industrial Special Concentrically Braced Frame Structure

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Roberto Javier Merino Vela ◽  
Emanuele Brunesi ◽  
Roberto Nascimbene
Keyword(s):  
Time History ◽  
Response Spectra ◽  
Frame Structure ◽  
Eurocode 8 ◽  
Industrial Complex ◽  
Braced Frame ◽  
Nonstructural Components ◽  
Floor Response Spectra ◽  
Concentrically Braced Frame ◽  
Concentrically Braced

Nonstructural components play an important role in the correct functioning of industrial facilities, which may suffer greatly from earthquake-induced actions, as demonstrated by past seismic events. Therefore, the correct evaluation of seismic demands acting upon them is of utmost importance when assessing or designing an industrial complex exposed to seismic hazard. Among others, nonlinear time history analyses (NLTHA) of structural systems including nonstructural elements and floor response spectra are well-known methods for computing these actions, the former being more accurate and the latter being less onerous. This work focuses on deriving floor spectra for a steel special concentrically braced frame (SCBF), which is a common type of lateral-load resisting system for industrial frames. The results are used to compute the seismic actions on a small liquid storage tank mounted on the case study frame. Additionally, the results are compared to those obtained by modeling the structure and the tank together, that is, by modeling the tank explicitly and incorporating it within the model of the support structure. To this end, a simple model, consisting of two uncoupled single degree-of-freedom systems, is used for the tank. The floor spectra resulting from both approaches are compared to establish differences in the behavior of the structure and nonstructural element/component. Finally, the seismic demand on the tank—obtained by direct and indirect analyses—is compared to that obtained by applying ASCE 7-10 and Eurocode 8 prescriptions.

Static Strength Analysis on Bus Body Frame Based on I-DEAS Software

2012 ◽  
Vol 263-266 ◽  
pp. 2043-2046
Author(s):  
Yuan Hua Chen ◽  
Guo Fu Wang
Keyword(s):  
Maximum Stress ◽  
Element Model ◽  
Strength Analysis ◽  
Body Frame ◽  
Maximum Displacement ◽  
Static State ◽  
Bus Body ◽  
Strength And Stiffness ◽  
Reliable Basis

On the basis of the established finite element model, the strength and stiffness of structure of bus body frame were analyzed under working conditions of bending and twisting in static state. The nodes of maximum stress and maximum displacement were identified, which could provide a reliable basis for follow-up lightweight structural optimization designs.

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