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Author : Justin Binder
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (13 download)
Download or read book Seismic Performance of New Hybrid Ductile-rocking Braced Frame System written by Justin Binder and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Lydell Wiebe
Publisher :
ISBN 13 : 9780473335267
Total Pages : 96 pages
Book Rating : 4.3/5 (352 download)
Download or read book Design Guide for Controlled Rocking Steel Braced Frames written by Lydell Wiebe and published by . This book was released on 2015 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Following the 2011 Christchurch earthquake, there has been significant interest in using better performing seismic load-resisting systems. Controlled Rocking Steel Braced Frames (CRSBFs) are a special form of structural system that sustains less damage than conventional ductile approaches. The system dissipates ductile energy by controlled rocking, forming part of a low damage or recoverable structural solution. Selecting and using rocking structural systems requires specialist knowledge of their behaviour, key parameters, and suitable analysis and design techniques to deliver the intended performance. Within New Zealand, only a handful of companies have successfully undertaken research and development to enable them to deliver CRSBFs as part of building projects. Sponsored by SCNZ and industry, the Design Guide for Controlled Rocking Steel Braced Frames (SCNZ - 110:2015) was conceived to facilitate the use of CRSBFs, enabling experienced structural engineers to consider and harness the potential benefits of this type of alternative structural system. This Guide summarises recent research developments and gives designers general guidance on application, limitations and key considerations. It includes two worked preliminary design examples, relating to a load bearing and a non-load bearing steel braced frame, which will aid designers in the preliminary design to achieve frame sizes and consider the appropriate design effects."--Publisher's website.
Author : Keith D. Palmer
Publisher :
ISBN 13 :
Total Pages : 638 pages
Book Rating : 4.:/5 (874 download)
Download or read book Seismic Behavior, Performance and Design of Steel Concentrically Braced Frame Systems written by Keith D. Palmer and published by . This book was released on 2012 with total page 638 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation describes a research program on special concentrically braced frame (SCBF) and buckling-restrained braced frame (BRBF) systems. The study builds upon previous work performed as part of a research program supported by the George E. Brown Network for Earthquake Engineering Simulation (NEES) entitled "International Hybrid Simulation of Tomorrow's Braced Frame." This program was initiated due to practical and experimental evidence that SCBFs were not performing as intended by current seismic design provisions. The current study includes a comprehensive experimental and analytical program which included two first-of-its-kind, two-story, one-bay by one-bay SCBF and BRBFs experiments. The experiments were performed at the University of Minnesota NEES laboratory to take advantage of its ability to apply large-displacement bi-directional loading. The two specimens were configured with braces in two orthogonal bays framing into a ``shared'' column with a floor system designed and constructed to simulate realistic conditions. The first specimen, the SCBF, employed HSS3x3x1/4 braces in a single-story X-configuration with one continuous brace and a pair of spliced braces in the opposing direction. The second test specimen, the BRBF, employed pin-ended, collared BRBs in a single-diagonal configuration. The analytical study consisted of a large suite of finite element simulations aimed at identifying the main parameters that influence the damage at the beam-column-gusset connection region in BRBFs and to make recommendations for the design and detailing of this connection region. This research has resulted in a number of findings including the observation that out-of-plane loading and deformation had little impact on the drift and ductility capacity of the system when compared to planar frame test results. In fact, the drift capacity of the SCBF test frame was only 6% less than that of comparable planar frames while the ductility and cumulative ductility capacities of the BRBF exceeded that of many of the planar BRBF system tests. Based on the experimental and analytical findings, design and detailing recommendations were developed for the connection at the brace splice point in the single-story, X-configured system. Design and detailing recommendations were also made for the corner gusset plate connection region in BRBFs.
Author : Federico M. Mazzolani
Publisher : Springer Nature
ISBN 13 : 3031628888
Total Pages : 1034 pages
Book Rating : 4.0/5 (316 download)
Download or read book Proceedings of the 11th International Conference on Behaviour of Steel Structures in Seismic Areas written by Federico M. Mazzolani and published by Springer Nature. This book was released on with total page 1034 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Jiun-Wei Lai
Publisher :
ISBN 13 :
Total Pages : 1023 pages
Book Rating : 4.:/5 (94 download)
Download or read book Experimental and Analytical Studies on the Seismic Behavior of Conventional and Hybrid Braced Frames written by Jiun-Wei Lai and published by . This book was released on 2012 with total page 1023 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation summarizes both experimental and analytical studies on the seismic response of conventional steel concentrically braced frame systems of the type widely used in North America, and preliminary studies of an innovative hybrid braced frame system: the Strong-Back System. The research work is part of NEES small group project entitled "International Hybrid Simulation of Tomorrow's Braced Frames." In the experimental phase, a total of four full-scale, one-bay, two-story conventional braced frame specimens with different bracing member section shapes and gusset plate-to-beam connection details were designed and tested at the NEES@Berkeley Laboratory. Three braced frame specimens were tested quasi-statically using the same predefined loading protocol to investigate the inelastic cyclic behavior of code-compliant braced frames at both the global and local level. The last braced frame specimen was nearly identical to one of those tested quasi-statically. However, it was tested using hybrid simulation techniques to examine the sensitivity of inelastic behavior on loading sequence and to relate the behavior observed to different levels of seismic hazard. Computer models of the test specimens were developed using two different computer software programs. In the software framework OpenSees fiber-based line elements were used to simulate global buckling of members and yielding and low-cycle fatigue failure at sections. The LS-DYNA analysis program was also used to model individual struts and the test specimens using shell elements with adaptive meshing and element erosion features. This program provided enhanced ability to simulate section local buckling, strain concentrations and crack development. The numerical results were compared with test results to assess and refine and the ability of the models to predict braced frame behavior. A series of OpenSees numerical cyclic component simulations were then conducted using the validated modeling approach. Two hundred and forty pin-ended struts with square hollow structural section shape were simulated under cyclic loading to examine the effect of width-to-thickness ratios and member slenderness ratios on the deformation capacity and energy dissipation characteristics of brace members. The concept of a hybrid system, consisting of a vertical elastic truss or strong-back, and a braced frame that responds inelastically, is proposed herein to mitigate the tendency of weak-story mechanisms to form in conventional steel braced frames. A simple design strategy about member sizing of the proposed Strong-Back System is provided in this study. To assess the ability of the new Strong-Back System to perform well under seismic loading, a series of inelastic analyses were performed considering three six-story hybrid braced frames having different bracing elements, and three six-story conventional brace frames having different brace configurations. Monotonic and cyclic quasi-static inelastic analyses and inelastic time history analyses were carried out. The braced frame system behavior, bracing member force-displacement hysteresis loops, and system residual drifts were the primary response quantities examined. These indicated that the new hybrid system was able to achieve its design goals. Experimental results show for the same loading history that the braced frame specimen using round hollow structural sections as brace members has the largest deformation capacity among the three types of bracing elements studied. Beams connected to gusset plates at the column formed plastic hinges adjacent to the gusset plate. The gusset plates tend to amplify the rotation demands at these locations and stress concentrations tended to result in early fractures of the plastic hinges that form. To remedy this problem, pinned connection details used in the last two specimens; these proved to prevent failures at these locations under both quasi-static and pseudo-dynamic tests. Failure modes observed near the column to base plate connections in all of the specimens suggest the need for further study. Both OpenSees and LS-DYNA models developed in this study predict the global braced frame behavior with acceptable accuracy. In both models, low-cycle fatigue damage models were needed to achieve an acceptable level of fidelity. Shell element models were able to predict local behavior and the mode of failures with greater but not perfect confidence. OpenSees analysis results show that the proposed hybrid braced frames would perform better than conventional braced frames and that the story deformations are more uniform. Finally, future research targets are briefly discussed at the end of this dissertation.
Author : Derek Slovenec
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (945 download)
Download or read book Seismic Evaluation, Rehabilitation, and Improved Design of Sub-standard Steel Concentrically Braced Frame Buildings written by Derek Slovenec and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Seismic design of multi-story buildings requires capacity design principles that allow for distributed damage (plastic member deformations) to occur over the building height while preventing soft-story failure mechanisms that may lead to collapse. Seismic evaluation of steel concentrically braced frame (CBF) buildings has revealed that they exhibit soft-story behavior due to non-uniform brace degradation and non-ductile failure modes. This research proposes a rehabilitative design procedure for existing buildings that uses a stiff rocking core to redistribute plastic deformations along the structure's height. Additionally, an improved design procedure for braced frame columns is proposed for new frame design. Several representative frames were designed and evaluated using nonlinear transient seismic finite element analysis and large-scale hybrid experimental testing. Predicted, analytical, and experimental response results show reasonable agreement, and the proposed techniques are believed to be reliable for achieving desirable seismic performance in low- to mid-rise steel braced frame structures.
Author : Gary Satwika Djojo
Publisher :
ISBN 13 :
Total Pages : 390 pages
Book Rating : 4.:/5 (19 download)
Download or read book The Centralised Rocking Concentrically Braced Frame written by Gary Satwika Djojo and published by . This book was released on 2018 with total page 390 pages. Available in PDF, EPUB and Kindle. Book excerpt: Conventional ductile structures rely on system ductility involving inelastic action in selected components in their lateral load resisting systems to dissipate earthquake energy. When subjected to severe earthquakes, the lateral load resisting systems are expected to undergo large deformations without losing their strength and structural integrity. However, the extent of damage caused by these severe earthquakes can be considerable, requiring extensive structural repairs or demolitions and causing significant ongoing social and economic disruption. In order to minimise the disruption, a low damage design philosophy is adopted. Low damage structures are expected to withstand severe earthquakes without requiring extensive structural repairs, using either or both isolating systems or sacrificial systems which either do not need repair or are readily replaceable. In order to respond the performance targets for low damage design, an innovative Centralised Rocking Concentrically Braced Frame (CRCBF) system has been developed in this thesis. The CRCBF system utilises a free-base V-braced Concentrically Braced Frame and a centralised rocking system with Ringfeder® - Friction ring springs as its energy dissipation devices. The CRCBF system does not rock under gravity loading, Ultimate Limit State (ULS) wind loading, and Serviceability Limit State (SLS) earthquake loading, remains essentially elastic under ULS earthquake loading by undergoing controlled rocking, and dependably returns to its initial position following the ULS earthquake. As the CRCBF system rocks back-and-forth about the central base of the CRCBF, the ring springs are arranged to work as a double acting system to accommodate cyclic vertical movements of the CRCBF columns and to dissipate earthquake energy during rocking. Additionally, the ring springs are partially prestressed to provide a high initial stiffness for the CRCBF system in order to prevent rocking at the SLS earthquake level. Two designs of double acting ring springs systems have been developed for the CRCBF system. The first design (Type I) of the double acting ring springs system generates a parallelogram-shaped hysteresis response, whereas the second design (Type II) of the double acting ring springs system generates a flag-shaped hysteresis response. Upon the lock-up of the ring springs in the MCE event, structural fuses, such as machined-down threaded rods and - ii - column baseplates, are designed to yield. The yielding of the machined-down threaded rods and the column baseplates prevents yielding of the other CRCBF components, which have less dependable inelastic behaviour. Then, after the MCE event, the yielded machined-down threaded rods can be replaced and the deformed column baseplates are repaired if necessary, allowing a structure designed with the CRCBF system to be fully operational. To maintain the lateral stiffness of the CRCBF and to transfer internal forces between those components at all time, all joint connections for the CRCBF system are designed as rigid connections, especially for the beam-brace-column joint connections. Therefore, two advanced pass-through beam-brace-column connections are developed for the CRCBF system. A Square Hollow Section (SHS) column has been designed with pass-through beam and brace slots, allowing a collector beam and a brace to pass through the SHS column. The collector beam and the brace are then welded to the SHS column faces. Finally, the SHS column is filled with concrete. These joint connections are not only cost-effective, when compared to bolted connections, but also easy to fabricate with modern equipment. The behaviour of the CRCBFs has been validated by numerical analyses and a series of experimental tests. Two CRCBF models were developed with the Type II double acting ring springs system and two different types of pass-through beam-brace-column connections where each CRCBF model represented each type of pass-through beam-brace-column connections. The numerical analyses were conducted using SAP2000 and Abaqus/CAE. Linear static analysis, non-linear pushover analysis, and non-linear time history analyses were undertaken using SAP2000, while finite element analyses (FEA) for investigating the complex behaviour of the two pass-through beam-brace-columns were undertaken using Abaqus. Then, a series of experimental tests were undertaken, comprising component testing, energy dissipation device testing, and centralised rocking frame testing. Lastly, the test results were compared with the analysis results derived from SAP2000 and Abaqus. The numerical analyses and experimental testing of the CRCBF systems showed that the CRCBF systems exhibit stable and repeatable flag-shaped hysteresis responses. A good agreement in axial forces is achieved between the SAP2000 analysis results and the test results. Also, a good agreement in Von Mises stresses in the beam-brace-column panel zones is achieved between the Abaqus FEA results and the test results. Lastly, the Abaqus FEA results showed that column baseplates, which were optimised with mild steel square supports, - iii - perform well as structural fuses for the CRCBF systems. The column baseplates developed a yieldline when the CRCBF columns are in compression. The results derived from the experimental testing and the numerical analyses have determined the behaviour of the CRCBF systems and have shown that the CRCBF systems meet the performance criteria required for a low damage system.
Author : Xiang Ma
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (666 download)
Download or read book Seismic Design and Behavior of Self-centering Braced Frame with Controlled Rocking and Energy-dissipating Fuses written by Xiang Ma and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This research aims to develop a self-centering controlled rocking structural system for earthquake resistant buildings that provides significantly improved performance through reduction in structural damage, repair costs, and downtime of buildings subjected to severe earthquakes. The controlled rocking system primarily consists of a post-tensioned steel braced frame that is designed to rock upon its foundation during an earthquake, elastic post-tensioning strands to provide overturning resistance and self-centering action, and replaceable structural fuses to dissipate earthquake energy. The system can minimize earthquake-induced damage and facilitate quick and economical post-earthquake repairs through its self-centering capability and concentration of inelastic deformation in the replaceable fuses. Steel shear plates with butterfly-shaped links are employed as structural fuses, and their ductile performance was verified by quasi-static cyclic tests. A two-thirds scale shaking table test of a three-story rocking system was conducted at the E-Defense facility in Japan. Test results demonstrated that the system responds predictably to earthquake excitation with column uplifting and frame rigid-body rotation. Under input motions scaled to the level of the Maximum Considered Earthquake, the resulting roof drift ratio stayed below the implied building code limit of 3%, and the braced frame completely self-centered without any damage. Effectiveness of key design details and behavior of the major structural components are examined, and a numerical model is validated through comparison with the test results. Analytical case studies are conducted and a general design procedure is proposed, which is compatible with current building code approaches. Simple methods are formulated to predict the earthquake-induced rocking frame drifts and member force demands. The proposed methods are validated through nonlinear dynamic analyses of various case buildings subjected to a set of 22 earthquake ground motions.
Author : Shahrzad Dastmalchi
Publisher :
ISBN 13 :
Total Pages : 177 pages
Book Rating : 4.:/5 (122 download)
Download or read book Performance-Based Design and Assessment of Controlled Rocking Steel Braced Frames written by Shahrzad Dastmalchi and published by . This book was released on 2020 with total page 177 pages. Available in PDF, EPUB and Kindle. Book excerpt: Controlled rocking steel braced frames (CRSBFs) have been developed with the goal of minimizing the post-earthquake impact of primary building functions. While there has been significant research to date to demonstrate the viability of the CRSBF as a high-performance system, much less has been accomplished in the development of performance-based design and assessment methods. This research is focused on developing models, tools and techniques for practicing engineers to analyze, design and assess the performance of CRSBFs. To avoid the computational expense of nonlinear response history analyses, an approximate method is formulated to estimate the CRSBF drift demands using the primary design parameters. Additionally, a reliability-based methodology for establishing the load and resistance factors for the force-controlled (braced frame) members is formulated. A key departure from previously developed capacity design approaches is the development of an explicit link between the effect of the failure of the force-controlled components and system level performance limit states (collapse and post-earthquake structural safety). The results from a case study applied to 3-, 6- and 9-story building cases show that the effect of force-controlled components is more significant for the collapse limit state compared to post-earthquake structural safety. Also, even when the resistance to load factor ratio ( / ) is increased to 1.8, the 50-year collapse probability remained below the 1% threshold prescribed by current building codes. The effect of record-to-record and modeling uncertainty on the seismic response and performance assessment of CRSBFs is also studied. The results showed that the impact of modeling uncertainty on seismic performance increases with the building height. To enable practitioners to estimate the service life costs of potential designs, surrogate models are developed to assess earthquake-induced life cycle economic loss and environmental impacts. The effectiveness of the surrogate models is demonstrated by evaluating their accuracy on "unseen" (i.e., not used in the development of the surrogate models) designs.
Author : Aid Jnaid
Publisher :
ISBN 13 :
Total Pages : 247 pages
Book Rating : 4.:/5 (113 download)
Download or read book Design, Modelling, and Seismic Performance of Outrigger Braced Frame Steel Buildings Subjected to Crustal and Subduction Earthquakes written by Aid Jnaid and published by . This book was released on 2018 with total page 247 pages. Available in PDF, EPUB and Kindle. Book excerpt: Concentrically braced frames (CBFs) are widely used in North America. The CBFs possess high stiffness and moderate ductility, while braces are designed to buckle in compression and yield in tension. However, after a brace experiences buckling, its compression strength diminishes and the system undergoes asymmetrical response, while the distribution of internal forces and deformations is influenced by the frequency content of ground motions. Despite the system's stiffness, CBFs are prone to concentrate damage within a floor which leads to the formation of storey mechanism. To preserve the stability of the system during the nonlinear seismic response, the National Building Code of Canada (NBCC) imposes limits on a building's height which depends on the selected ductility-related force modification factor, Rd. Thus, the height limit for buildings with moderately ductile concentrically braced frames, MD-CBFs, is 40 m and for limited ductility concentrically braced frames, LD-CBFs, is 60 m. To safely increase the height limit of ductile braced frame buildings, a system labelled Outrigger Braced Frame, OBF, is proposed and developed in this study. According to the Council on Tall Buildings and Urban Habitat (CTBUH), a building with more than 14 stories or more than 50 meters in height may be considered a high-rise building. The aim of this research is to develop, design, model, and study the seismic performance of mid-rise (e.g. tweleve-storey) and high-rise (e.g., sixteen-storey) OBF buildings subjected to dynamic loads. It is noted that the outrigger system functions by tying together a core system and a perimeter system. Herein, the core system is made of MD-CBFs and the perimeter system is made of gravity columns. Furthermore, only the core braces are designed to dissipate energy, while the outrigger's diagonals are designed to respond in the elastic range. The performance of OBF system is controlled by the amount of added stiffness and optimum location of outriggers across the building's height, the number of levels with outriggers and the intensity of seismic zone. All multi-storey buildings are located in high-risk seismic zone of Victoria, B.C. Canada, on Site Class C. The selection of ground motions was made to capture the seismic characteristics at buildings location. Herein, two sets of crustal and subduction ground motions were considered such as California records and the mega-thrust magnitude 9 Tohoku records, respectively. The nonlinear time-history dynamic analyses were conducted using the OpenSees software. The main objectives of this thesis are three-fold: i) to identify the effect of subduction versus crustal ground motions on the seismic response of low-rise, mid-rise and high-rise MD-CBF buildings and to study their seismic performance from yielding to failure, ii) to provide design method and optimum location for outriggers of OBF steel buildings, iii) to assess the collapse safety of the proposed mid-rise and high-rise OBF steel buildings using FEMA P695 procedure and to compare their seismic performance against that resulted for MD-CBF buildings. It is concluded that the OBF buildings are slightly stiffer than the corresponding MD-CBF buildings, and they experienced lower interstorey drift and residual interstorey drift than the MD-CBF buildings. In all case studies considered here, the collapse margin ratio (CMR) is greater for buildings subjected to crustal ground motions than subduction ground motions. Evaluation of seismic performance of sample 12-storey and 16-storey OBF buildings shows that these buildings are able to pass the collapse safety acceptance criteria, ACMR ≥ ACMR10%, when subjected to both sets of ground motions. On the other hand, the corresponding MD-CBF buildings are not able to pass the collapse safety acceptance criteria when subjected to subduction records set. Hence, special attention should be given when designing buildings in seismic regions which are prone to both types of earthquakes.
Author : Mona Rais Esmaili
Publisher :
ISBN 13 :
Total Pages : 148 pages
Book Rating : 4.:/5 (111 download)
Download or read book Seismic Performance of Eccentrically Braced Frames Designed According to Canadian Seismic Provisions written by Mona Rais Esmaili and published by . This book was released on 2015 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt: Eccentrically braced frames (EBFs) are very effective lateral load resisting systems against earthquakes because of their hybrid behavior that includes great stiffness corresponding to the bracing actions, and considerable ductility owing to the inelastic activity of a small part of the floor beam called link. Current capacity design approach of EBFs is to confine the inelastic behavior of the frame primarily to the link such that other members remain essentially in elastic range. Limited research works are available in the literature studying the behavior of multi-storey EBFs designed according to the current Canadian seismic provisions. This thesis was aimed to study seismic performance of EBFs through nonlinear time history analysis (NLTHA) of three 4-, 8- and 14-storey chevron eccentrically braced frames. The selected EBFs were subjected to real and artificial ground motion records scaled to match the response spectrum of Vancouver. All the EBFs, designed according to current capacity design provisions, exhibited excellent seismic performance in terms of stiffness, strength, and ductility. It was observed that the inelastic link rotations of all EBFs were lower than the design limit of 0.08 rad, except for the two upper floors in 14-storey EBF where the link rotation slightly exceeded the limit. Seismic analysis also showed that maximum inelastic link shear forces exceeded the values recommended in design for many earthquake records. Although NLTHA can precisely estimate structural seismic responses, it requires high computational demands making it impractical for engineering design offices. On the other hand, the conventional pushover analysis does not consider contributions of higher modes to the structural responses and thus it often does not provide good estimation of seismic responses for taller buildings. Capacity-Spectrum Method (CSM) and modal pushover analysis (MPA) are two simple nonlinear static methods that have been proposed and recently used for seismic performance evaluation of few lateral load-resisting systems. This research further studies the application of CSM and MPA as alternatives for rigorous NLTHA to estimate seismic performance parameters of EBFs. The three selected EBFs were analyzed using MPA and CSM and the results were compared with nonlinear seismic analysis results. It was observed that both CSM and MPA predicted the peak top displacements of EBFs with sufficient accuracy.
Author : Fokruddin Ahmad
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.3/5 (799 download)
Download or read book Performance Evaluation of Steel Buckling Restrained Braced Frames Subjected to Far-Field, Near-Field, and Long-Duration Earthquakes written by Fokruddin Ahmad and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The use of Buckling Restrained Brace Frames (BRBFs) has been increasing in recent decades due to their ability to provide superior seismic performance and enhance the resilience of buildings against earthquakes. However, not many studies have extensively and thoroughly investigated the response and resiliency of prescriptively designed BRBF buildings to varying types of earthquake hazards. This study fills that research gap by investigating the seismic performance of two code-designed BRBFs prototype buildings subjected to far-field, near field with pulse and without pulse, and long-duration ground motion sets. The first phase of the study investigated the seismic resiliency of the prescriptively designed BRBF buildings and compared them to identical prototypes designed with mass timber PT-CLT rocking walls using the FEMA P-58 methodology to compare seismic losses. The seismic loss investigation was part of a larger study evaluating the two types of structural systems using multiple criteria decision analysis across four performance categories of seismic resiliency, global warming potential, superstructure cost, and durability. The global warming potential and superstructure cost estimate was completed by others, but this study completed the seismic resiliency assessment and multiple criteria decision analysis.The second phase of this dissertation work analyzed the structural response of the two BRBF prototype buildings across four sets of ground motions representing different hazard levels in Seattle, WA. The two prototype buildings were modeled in 3D using OpenSeesPy to understand the effect of different ground motion types on the structural responses. The analysis results showed that near-field motions increase the deformation demands, such as inter-story drift and maximum ductility in the pulse direction. Though BRBFs are not a self-centering systems, only the upper two floors of the mid-rise building experienced residual drift higher than 0.2%, which is the threshold for expecting minor repair and structural realignment. None of the stories had residual inter-story drift exceeding 0.5% drift for any motion sets. Overall, the code minimum based BRBF buildings showed excellent performance across all the different hazard types. However, the one caveat of this analysis was that long-duration motions had significantly higher cumulative ductility demand than other motion sets.Therefore, the final phase of this dissertation works further investigated the cumulative deformation demand on BRBF braces under long-duration motions. It is important to verify the ductility of the braces through analysis or testing because they act as the primary structural fuse to dissipate the earthquake energy. The final study compared different loading protocols from different countries to the nonlinear modeling results of long-duration motions. It was determined that the long duration motions had over 80% probability of exceeding the current AISC 341 required testing protocol. To rectify these issues, a new loading protocol appropriate for long-duration earthquakes was proposed that accounts for the increased plastic deformation demand and matches the cyclic content of the nonlinear dynamic analyses.In conclusion, these studies have demonstrated that prescriptively designed BRBFs that meet code minimum requirements are a high performing lateral force resisting system to a range of earthquake hazards. They have excellent seismic resiliency, even when not optimized during design through nonlinear time history analysis, as is common in performance-based earthquake engineering. Additionally, the code-designed BRBF buildings were not predicted to have high residual inter-story drifts, which means they are highly likely to be repairable with minor adjustments and re-alignment. However, it was identified that long-duration earthquakes will increase the ductility demand on the braces significantly compared to far-field and near-field earthquakes and that current minimum testing requirements do not account for this increase. A new protocol was proposed to rectify this one challenge with BRBFs.
Author : Andrew D. Sen
Publisher :
ISBN 13 :
Total Pages : 328 pages
Book Rating : 4.:/5 (95 download)
Download or read book Seismic Performance of Chevron Concentrically Braced Frames with Weak Beams written by Andrew D. Sen and published by . This book was released on 2014 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt: Steel concentrically braced frames are lateral seismic force resisting systems that have been historically popular. Despite extensive deployment and continued service of these systems, little research has focused on the seismic performance and rehabilitation of older braced frames, termed non-seismic concentrically braced frames (NCBFs). Such frames were designed prior to the advent of capacity design standards and lack details and brace section geometry that promote ductility and sustain resistance, such as adequate gusset plate rotational clearance, minimum weld toughness, and brace compactness limits. Beams in NCBFs with braces in chevron configurations (V and inverted V) are commonly unable to develop the design brace unbalanced load specified in the 2010 AISC Seismic Provisions that arises after brace buckling. NCBFs with these weak beams are the primary subject of this research program. Two-story experimental specimens with braces in the inverted V configuration were tested at the National Center for Research on Earthquake Engineering in Taiwan to examine the seismic response of a prototypical existing NCBF and three rehabilitation schemes. The results show that poor brace compactness and connection details can be highly detrimental to system performance, but weak beam braced frames with ductile details can achieve good ductility while maintaining strength. Numerical models of the specimens, developed in Abaqus, simulate the observed response well and provide a validated basis for future analyses.
Author : Tim S. Lim
Publisher :
ISBN 13 :
Total Pages : 83 pages
Book Rating : 4.:/5 (862 download)
Download or read book High-performance Braces for Seismic Design written by Tim S. Lim and published by . This book was released on 2013 with total page 83 pages. Available in PDF, EPUB and Kindle. Book excerpt: The fundamental challenge for the structural engineer in designing earthquake-resistant structures is to design buildings with both adequate ductility and sufficient stiffness. Traditional lateral force resisting systems such as the moment resisting frame and the concentrically braced frame are both conventional structural schemes that have been implemented for many years, but result in only mediocre performance levels. The lacking stiffness of a moment resisting frame as well as the limited ductility of a concentrically braced frame gave impetus for engineers to direct significant research efforts into the development of new lateral resisting systems that embody a more stable hysteretic behavior, adequate ductility, control of damage, and energy dissipating capacity. Fortunately, several recent developments have allowed engineers to move one step closer to designing more efficient earthquake-resistant structures. "High-performance braces," as this thesis calls them, are new and improved bracing systems that combine the economy and stiffness of a concentrically braced frame with the ductility and energy dissipating capacity of a moment resisting frame. This thesis analyzes and evaluates three different types of high-performance braces: (i) the buckling-restrained brace frame, (ii) the self-centering energy dissipating brace frame, and (iii) the hybrid brace frame, with regards to their structural performance and economy. The primary goal of the thesis is to provide useful insights into the current developments of high-performance braces for practicing engineers in the hope that such systems can be more widely adopted and utilized in the contemporary design of earthquake-resistant structures. Keywords: High-performance braces, earthquake-resistant structures, seismic design
Author : Stephen A. Mahin
Publisher :
ISBN 13 :
Total Pages : 14 pages
Book Rating : 4.:/5 (123 download)
Download or read book Seismic Performance of Buckling Restrained Braced Frame Systems written by Stephen A. Mahin and published by . This book was released on 2004 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Andrew D. Sen
Publisher :
ISBN 13 :
Total Pages : 290 pages
Book Rating : 4.:/5 (19 download)
Download or read book New Methods for Seismic Performance Evaluation and Retrofit of Nonductile Concentrically Braced Frames written by Andrew D. Sen and published by . This book was released on 2018 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt: Concentrically braced frames (CBFs) have been used in steel construction as seismic-force-resisting systems for many decades and constitute a substantial proportion of existing building infrastructure. Until about 1990, CBFs were designed without the codified capacity-based and other ductile design provisions that ensure safety in today's special CBFs (SCBFs) used in regions with high seismic risk. Thousands of these older and potentially nonductile CBFs (NCBFs) remain in service in the high-seismicity areas of the west coast of the US and other more moderately seismically vulnerable regions. These NCBFs utilize a wide variety of connections, components, and frame configurations with deficiencies expected to lead to significant damage and potential collapse in earthquakes. Seismic retrofit of NCBFs may be necessary to ensure occupant safety and building functionality, but current engineering guidance for determining retrofit need and type is limited. The state of practice evaluates the seismic vulnerability of CBFs using simplistic models for braces, beams, and columns, and the nonlinear behavior of connections is typically not considered; it is clear that the vulnerability depends on more complex component behavior. To develop more comprehensive engineering methods that can accurately estimate the vulnerability of NCBFs and the improved performance of retrofitted NCBFs, integrated experimental and computational research programs were conducted. First, two series of large-scale experiments of existing and retrofitted NCBF subassemblages were performed to investigate brace, connection, and beam deficiencies common to NCBFs. The experiments identified critical deficiencies but also beneficial yielding mechanisms (e.g., bolt-hole elongation, beam yielding in the chevron configuration, etc.) which could be retained in retrofit. Experimentally validated, nonlinear modeling approaches capable of simulating brace fracture, connection fracture, weak frame elements, and post-fracture response of components with secondary yielding mechanisms were then developed to advance numerical simulation capabilities. These models were used to enable system-level response-history analysis for seismic performance evaluation. Specifically, the seismic performance (including collapse) of three- and nine-story buildings were investigated at multiple (5) hazard levels. The models were also used to evaluate retrofit strategies; these results combined with the experimental work were used to develop a cost-effective seismic retrofit methodology based on balancing yielding mechanisms and suppressing severe failure modes.
Author : Paolo Gardoni
Publisher : Springer
ISBN 13 : 3319297139
Total Pages : 568 pages
Book Rating : 4.3/5 (192 download)
Download or read book Multi-hazard Approaches to Civil Infrastructure Engineering written by Paolo Gardoni and published by Springer. This book was released on 2016-06-22 with total page 568 pages. Available in PDF, EPUB and Kindle. Book excerpt: This collection focuses on the development of novel approaches to address one of the most pressing challenges of civil engineering, namely the mitigation of natural hazards. Numerous engineering books to date have focused on, and illustrate considerable progress toward, mitigation of individual hazards (earthquakes, wind, and so forth.). The current volume addresses concerns related to overall safety, sustainability and resilience of the built environment when subject to multiple hazards: natural disaster events that are concurrent and either correlated (e.g., wind and surge); uncorrelated (e.g., earthquake and flood); cascading (e.g., fire following earthquake); or uncorrelated and occurring at different times (e.g., wind and earthquake). The authors examine a range of specific topics including methodologies for vulnerability assessment of structures, new techniques to reduce the system demands through control systems; instrumentation, monitoring and condition assessment of structures and foundations; new techniques for repairing structures that have suffered damage during past events, or for structures that have been found in need of strengthening; development of new design provisions that consider multiple hazards, as well as questions from law and the humanities relevant to the management of natural and human-made hazards.
