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1
Coy, Bradly B. "Buckling-Restrained Braced Frame Connection Design and Testing." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd2030.pdf.
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Matthews, Mark Thurgood. "Impact of Large Gravity Loads on Buckling Restrained Braced Frame Performance." Diss., CLICK HERE for online access, 2009. http://contentdm.lib.byu.edu/ETD/image/etd3286.pdf.
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Burkholder, Margaux Claire. "Performance Based Analysis of a Steel Braced Frame Building With Buckling Restrained Braces." DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/715.
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This paper provides an assessment of the seismic performance of a code-designed buckling restrained braced frame building using the performance-based analysis procedures prescribed in ASCE 41-06. The building was designed based on the standards of the ASCE 7-05 for a typical office building located in San Francisco, CA. Nonlinear modeling parameters and acceptance criteria for buckling restrained brace components were developed to match ASCE 41-06 design standards for structural steel components, since buckling restrained braces are not currently included in ASCE 41-06. The building was evaluated using linear static, linear dynamic, nonlinear static and nonlinear dynamic analysis procedures. This study showed that the linear procedures produced more conservative results, with the building performing within the intended Life Safety limit, while the nonlinear procedures predicted that the building performed closer to the Immediate Occupancy limit for the 2/3 maximum considered earthquake hazard. These results apply to the full maximum considered earthquake hazard as well, under which the building performed within the Collapse Prevention limit in the linear analysis results and within the Life Safety limit in the nonlinear analysis results. The results of this paper will provide data for the engineering profession on the behavior of buckling restrained braced frames as well as performance based engineering as it continues to evolve.
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Oxborrow, Graham T. "Optimized distribution of strength in buckling-restrained brace frames in tall buildings /." Diss., CLICK HERE for online access, 2009. http://contentdm.lib.byu.edu/ETD/image/etd2986.pdf.
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Oxborrow, Graham Thomas. "Optimized Distribution of Strength in Buckling-Restrained Brace Frames in Tall Buildings." BYU ScholarsArchive, 2009. https://scholarsarchive.byu.edu/etd/1794.
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Nonlinear time history analysis is increasingly being used in the design of tall steel structures, but member sizes still must be determined by a designer before an analysis can be performed. Often the distribution of story strength is still based on an assumed first mode response as determined from the Equivalent Lateral Force (ELF) procedure. For tall buckling restrained braced frames (BRBFs), two questions remain unanswered: what brace distribution will minimize total brace area, while satisfying story drift and ductility limits, and is the ELF procedure an effective approximation of that distribution? In order to investigate these issues, an optimization algorithm was incorporated into the OpenSees dynamic analysis platform. The resulting program uses a genetic algorithm to determine optimum designs that satisfy prescribed drift/ductility limits during nonlinear time history analyses. The computer program was used to investigate the optimized distribution of brace strength in BRBFs with different heights. The results of the study provide insight into efficient design of tall buildings in high seismic areas and evaluate the effectiveness of the ELF procedure.
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Prinz, Gary S. "Using Buckling-Restrained Braces in Eccentric Configurations." BYU ScholarsArchive, 2010. https://scholarsarchive.byu.edu/etd/2134.
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Ductile braced frames are often used to resist lateral earthquake loads in steel buildings; however the presence of a brace element can sometimes interfere with architectural features. One common type of ductile braced frame system sometimes used to accommodate architectural features is the eccentrically braced frame (EBF). In order to dissipate seismic forces, EBF beam regions (called links) must sustain large inelastic deformations. EBF links with column connections must transmit large moments and shear forces to facilitate link rotation. Experiments have shown that welded link-to-column connections tend to fracture in the link flange prior to large link rotations. This study investigated methods for improving EBF link-to-column connection performance, and proposed an alternative ductile braced frame system for accommodating architectural features. Several EBF links with reduced web and flange sections were analytically investigated using validated finite element models in ABAQUS. Results indicated that putting holes in the link web reduced stress and strain values in the link flanges at the connection, but increased the plastic strain and stress triaxiality in the web at the edges of holes. Removing area from the link flanges had little effect on connection stresses and strains. Thus, the reduced web section and reduced flange section methods are not a promising solution to the EBF link-to-column connection problem. The alternative braced frame system proposed in the dissertation used ductile beam splices and buckling-restrained braces in eccentric configurations (BRBF-Es) to accommodate architectural features. Design considerations for the BRBF-Es were determined and dynamic BRBF-E performance was compared with EBF performance. BRBF-E system and component performance was determined using multiple finite element methods. Inter-story drifts and residual drifts for the BRBF-Es were similar to those for EBFs. Results indicated that BRBF-Es are a viable alternative to the EBF, and may result in better design economy than EBFs. With the BRBF-E, damage was isolated within the brace, and in the EBF, damage was isolated within the link, indicating simpler repairs with the BRBF-E. Shop welding of BRBF-E members may replace the multiple field welds required in EBF construction.
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Fuqua, Brandon W. "Buckling restrained braced frames as a seismic force resisting system." Manhattan, Kan. : Kansas State University, 2009. http://hdl.handle.net/2097/1131.
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Craft, Jennifer Lorraine. "Reducing Drifts in Buckling Restrained Braced FramesThrough Elastic Stories." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/4430.
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It is possible to reduce residual and maximum drifts in buildings by adding “elastic stories” that engage gravity columns in seismic response. An elastic story is a story wherein the buckling restrained brace frame (BRBF) size is increased to prevent yielding when an earthquake occurs. Buildings ranging from 4–16 stories were designed with various elastic story brace sizes and locations to determine the optimal combination to best reduce drifts. Gravity column stiffnesses were also varied in elastic story buildings to determine the effects on drifts. Computer models were used to analyze these buildings under a suite of earthquakes. Adding elastic stories reduce residual drifts 34% to 65% in 4- to 16-story BRBF buildings. General recommendations are made to achieve optimal reductions in drifts. For buildings with six or more stories, drifts were generally reduced most when an elastic story was added to every 4th story starting at level 1 (the bottom story). The most effective size for the braces in the elastic story appears to be three times the original brace size. For buildings with less than six stories, adding a three times elastic story to the bottom level was observed to reduce drifts the most. Further research is also recommended to confirm the optimal location and size of elastic stories for buildings with differing number of stories. Increasing gravity column stiffnesses in buildings with elastic stories helps to further reduce drifts, however it may not be economical. Residual drifts were observed to decrease significantly more than maximum drifts when elastic stories were added to buildings. Maximum drifts generally decreased at some levels, but also increased at others when elastic stories were used.
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Al-Sadoon, Zaid. "Seismic Retrofitting of Conventional Reinforced Concrete Moment-Resisting Frames Using Buckling Restrained Braces." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34755.
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Reinforced concrete frame buildings designed and built prior to the enactment of modern seismic codes of the pre-1970’s era are considered seismically vulnerable, particularly when they are subjected to strong ground motions. It is the objective of this research to develop a new and innovative seismic retrofit technology for seismic upgrading of nonductile or limited ductility reinforced concrete frame buildings involving the implementation of buckling restrained braces. To achieve this objective, combined experimental and analytical research was conducted. The experimental research involved tests of large-scales reinforced concrete frames under slowly applied lateral deformation reversals, and the analytical research involved design and nonlinear analysis of laboratory specimens, as well as design and dynamic inelastic response history analysis of selected prototype buildings in eastern and western Canada. The research project started with a comprehensive review of the building code development in Canada to assess the progression of seismic design requirements over the years, and to select a representative period within which a significant number of engineered buildings were designed and constructed with seismic deficiencies. A similar review of seismic design and detailing provisions of the Canadian Standard Association (CSA) Standard A23.3 on Design of Concrete Structures was also conducted for the same purpose. Six-storey and ten-storey prototype buildings were designed for Ottawa and Vancouver, using the seismic provisions of the 1965 National Building Code of Canada, representative of buildings in eastern and western Canadian. Preliminary static and dynamic linear elastic analyses were performed to assess the effectiveness of upgrading the ten-storey reinforced concrete building designed for Ottawa. The retrofit methods studied consisted of lateral bracing by adding reinforced concrete shear walls, diagonal steel braces, or diagonal steel cable strands. The results indicated that the retrofit techniques are effective in limiting deformations in non-ductile frame elements to
the elastic range. The numerical analyses were used to demonstrate the effectiveness of Buckling Restrained Braces (BRBs) as a retrofit method for seismically deficient reinforced concrete frame buildings. The experimental phase of research consisted of two, 2/3rd scale, single bay and single storey reinforced concrete frames, designed and constructed based on a prototype sixstorey moment resisting frame building located in Ottawa and Vancouver, following the
requirements of the 1965 edition of the NBCC. One test specimen served as a bare
control frame (BCF) that was first tested, repaired and retrofitted (RRF) to evaluate the effectiveness of the proposed retrofit methodology for buildings subjected to
earthquakes in the City of Ottawa. The control frame was assessed to be seismically
deficient. The second frame served as a companion non-damaged frame (RF) that was retrofitted with a similar retrofit concept but for buildings subjected to earthquakes in the City of Vancouver.
A new buckling restrained brace (BRB) was conceived and developed to retrofit existing sub-standard reinforced concrete frames against seismic actions. The new BRB consists of a ductile inner steel core and an outer circular sleeve that encompasses two circular steel sections of different diameters to provide lateral restraint against buckling in compression of inner steel core. Mortar is placed between the two circular sections to provide additional buckling resistance. The inner core is connected to novel end units that allow extension and contraction during tension-compression cycles under seismic loading while providing lateral restraint against buckling within the end zones. The end units constitute an original contribution to the design of Buckling Restrained Braces (BRBs), providing continuous lateral restraint along the core bar. The new technique has
been verified experimentally by testing four BRBs on the two test structures under
simulated seismic loading. The test results of the BRB retrofitted frames indicate
promising seismic performance, with substantial increases in the lateral load and
displacement ductility capacities by factors of up to 3.9 and 2.6, respectively. In addition, the test results demonstrate that the BRB technology can provide excellent drift control, increased stiffness, and significant energy dissipation, while the reinforced concrete frames continue fulfilling their function as gravity load carrying frames. The above development was further verified by an exhaustive analytical study using SAP2000. At the onset, analyses were conducted to calibrate and verify the analytical models. Two-dimensional, one-bay, one-storey models, simulating the BCF and RRF test frames, were created. The models were subjected to incrementally increasing lateral displacement reversals in nonlinear static pushover analyses, and the results were compared with those obtained in the test program. Material nonlinearity was modeled using “Links” to incorporate all lumped linear and nonlinear properties that were defined with moment-rotation properties for flexural frame members and with force-displacement properties for the diagonal buckling restrained braces. Comparison with test data demonstrated good agreement of the frame behaviour in the elastic and post-elastic ranges, and the loading and unloading stiffness. The research program was further augmented with nonlinear dynamic time history analyses to verify the feasibility of the new retrofit technique in multi-storey reinforced concrete frame buildings located in Canada and their performances relative to the performance-based design objectives stated in current codes. Prior to conducting the analyses, 450 artificial earthquake records were studied to select the best matches to the Uniform Hazard Spectra (UHS) according to the 2010 edition of the NBCC for Ottawa and Vancouver. Furthermore, additional analyses were conducted on buildings for the City of Ottawa based on amplified Uniform Hazard Spectrum compatible earthquake records. The nonlinear time-history response analyses were conducted using a model that permits inelasticity in both the frame elements and the BRBs.The results indicated that reinforced concrete buildings built before the 1970’s in the City of Ottawa do not require seismic retrofitting; they remain within the elastic range under current code-compatible earthquake records. The structural building performance is
within the Immediate Occupancy level, and all structural elements have capacities
greater than the force demands. In the City of Vancouver, buildings in their virgin state experienced maximum interstorey drifts of 2.3%, which is within the Collapse Prevention structural performance level. Improved building performance was realized by retrofitting the exterior frames with multiple uses of the BRB developed in this research project. The seismic shear demands were reduced in the columns, while limiting the deformations in the non-ductile frame elements to the elastic range. The lateral interstorey drift was limited to 0.92%, which lies within the Life Safety structural performance level.
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Anozie, Valencia Chibuike. "Parametric Study of Friction-Damped Braced Frames with Buckling-Restrained Columns using Recommended Frame and BRC Strength Factors." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1500294960127361.
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Al, Ateah Ali H. "NUMERICAL STUDY OF MULTIPLE ROCKING SELF-CENTERINGROCKING CORE SYSTEMS WITH BUCKLING-RESTRAINED COLUMNSFOR MID-RISE BUILDINGS." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1511816354436547.
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Blebo, Felix C. "Damage-Free Seismic-Resistant Self-Centering Friction-Damped Braced Frames with Buckling-Restrained Columns." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1429538820.
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Aukeman, Lisa J. "ASCE 7-05 DESIGN RULE FOR RELATIVE STRENGTH IN A TALL BUCKLING-RESTRAINED BRACED FRAME DUAL SYSTEM." DigitalCommons@CalPoly, 2011. https://digitalcommons.calpoly.edu/theses/464.
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In mid- to high-rise structures, dual systems (DS) enable a structural designer to satisfy the stringent drift limitations of current codes without compromising ductility. Currently, ASCE 7-05 permits a variety of structural systems to be used in combination as a dual system yet the design requirements are limited to the following statement: Moment frames must be capable of resisting 25% of the seismic forces while the moment frames and braced frames or shear walls must be capable of resisting the entire seismic forces in proportion to their relative rigidities.
This thesis assesses the significance of the 25% design requirement for the secondary moment frames (SMF) in dual systems with consideration of current structural engineering practice. Three 20-story buckling-restrained braced frame (BRBF) dual system structures were designed with varying relative strengths between the braced and special moment frame systems. The SMF system wa designed for 15%, 25%, and 40% of seismic demands and the BRBF system design has been adjusted accordingly based on its relative stiffness with respect to the moment frame. These structures were examined with nonlinear static and nonlinear dynamic procedures with guidance from ASCE 41-06.
The drift, displacement and ductility demands, and the base shear distribution results of this study show similar responses of the three prototype structures. These results indicate a secondary moment frame designed to less than 25% of seismic demands may be adequate for consideration as a dual system regardless of the 25% rule.
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Balling, Lukas. "A Comparison of Optimized Nonlinear Time History Analysis and the Equivalent Lateral Forces Method for Brace Design." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd2086.pdf.
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Pham, Huy. "Performance-based assessments of buckling-restrained braced steel frames retrofitted by self-centering shape memory alloy braces." Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/49040.
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Concrete-filled buckling restrained braces (BRBs) was first developed in 1988 in Tokyo, Japan, to prevent the steel plates in the core portion from buckling, leading the steel core to exhibiting a more stable and fully hysteretic loop than conventional steel braces. However, past studies have shown that buckling restrained braced frames (BRBFs) have a large residual deformation after a median or high seismic event due to steel’s residual strain. In order to address this issue, innovative self-centering SMA braces are proposed and installed in the originally unbraced bays in existing BRBFs to become a hybrid frame system where the existing steel BRBs dissipate energy induced by external forces and the newly added self-centering SMA braces restore the building configuration after the steel BRBs yield. A case study of conventional three-story BRBF retrofitted by the proposed self-centering SMA braces is carried out to develop systematic retrofit strategies, to investigate the structural behavior, and to probabilistically assess their seismic performance in terms of interstory drifts, residual drifts, and brace deformation, as compared to the original steel BRB frames. Finally, the developed brace component fragility curves and system fragility curves will be further used for the assessment of downtime and repair cost.
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Prinz, Gary S. "Effect of Beam Splicing on Seismic Response of Buckling-Restrained Braced Frames." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd2126.pdf.
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TRUSCOTT, GREGORY THOMAS. "Retrofit of Double Angles in Concentrically Braced Frames." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1217885861.
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Yeates, Christopher Hiroshi. "Minimizing Base Column Demands in Multi-Story Buckling Restrained Braced Frames Using Genetic Algorithms." BYU ScholarsArchive, 2010. https://scholarsarchive.byu.edu/etd/2901.
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Most structural optimization procedures focus on minimizing the total volume of steel in an attempt to reduce overall costs. However, many other factors can have an effect on the overall cost of a structure. Base column demands in particular, can affect base plate sizes, anchorage, and foundation design. Researchers have found that present methods for estimating column demands are too conservative. Nonlinear time history analyzes were conducted on buckling-restrained braced frames of six heights. Optimized results were found considering three ductility constraints and two optimization objectives. The two optimization objectives were minimized total brace area and minimized base column demands. The results show that designs created by using a minimized column demand objective led to column demands that ranged from 2 to 6% lower than column demands in designs generated by a total brace area minimizing objective. The average brace areas of the designs produced by the total brace area minimizing objective were 25 to 80% less than the designs produced by the column demand minimizing objective. Results showed that large braces in the top stories did not have an effect on column demands in the ground level story. The results indicate that base column demands can be minimized by minimizing braces areas. However, braces areas cannot be minimized by minimizing base column demands.
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Eryasar, Mehmet Emrah. "Experimental And Numerical Investigation Of Buckling Restrained Braces." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610364/index.pdf.
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A typical buckling restrained brace (BRB) consists of a core segment and a buckling restraining mechanism. When compared to a conventional brace, BRBs provide nearly equal axial yield force in tension and compression. Buckling restraining mechanism can be grouped into two main categories. Buckling is inhibited either by using a concrete or mortar filled steel tube or by using steel sections only. While a large body of knowledge exists on buckling restrained braces the behavior of steel encased BRBs has not been studied in detail. Another area that needs further investigation is the detailing of the deboding material. For all types of BRBs a debonding material or a gap has to be utilized between the core brace and the restraining mechanism. The main function of the debonding material is to eliminate the transfer of shear force between the core brace and the restraining mechanism by preventing or reducing the friction. A two phase research study has been undertaken to address these research needs. In the first phase an experimental study was carried out to investigate the potential of using steel encased BRBs. In the second phase a numerical study was conducted to study the friction problem in BRBs. The experimental study revealed that steel encased braces provide stable hysteretic behavior and can be an alternative to mortar filled steel tubes. Material and geometric properties of the debonding layer for desired axial load behavior were identified and presented herein.
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Tinker, John Andrew. "Development of an Ultra-Lightweight Buckling-Restrained Brace Using Analytical and Numerical Methods." PDXScholar, 2011. https://pdxscholar.library.pdx.edu/open_access_etds/447.
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An ultra-lightweight buckling-restrained brace (ULWBRB) is developed using a highly ductile aluminum core and FRP restrainer. Utilization of lightweight materials results in a BRB that is 25% the weight of traditional mortar-filled tube varieties allowing easy installation in small to medium sized buildings requiring seismic retrofit without the need for heavy equipment. Construction utilizes commonly stocked materials able to be customized for required strength, drift, and geometry limitations. Analytical single degree of freedom (SDOF) and Euler buckling models are compared with published equations to determine the required restrainer stiffness (RRS). SDOF models yield RRS values 200% higher than the Euler model. Applied end moments due to frame deformation are incorporated into a modified design method that gives RRS values 50% higher than Euler model without eccentricity. RRS is provided using a bundled and wrapped FRP tube configuration using a developed shear flow method considering composite action. Uniaxial low-cycle fatigue (LCF) testing of a 6061-T6 candidate alloy provides data for a constitutive model using combined kinematic-isotropic hardening. LCF testing of round short gage coupons indicates the candidate alloy is capable of stable cycling to 2%, 3%, and 4% total strain with excellent ductility. Early fracture of specimens at 24, 18, and 11 cycles, respectively, also indicates that other candidate alloys should be examined for improved fatigue life. However, inconsistency is noted between similar tests of 6061-T6 that were able to achieve up to 76 cycles at 2.5% total strain. ULWBRB FEA models loaded monotonically consistently give higher RRS values as compared to the analytical methods. This is due to assignment of initial imperfections, longer more realistic unbraced length, higher axial loads achieved through the post-yield region, and plastic hinging potential. Cyclic simulations of braces with the same RRS values are also able to achieve reliable and stable hysteretic behavior through 21 cycles. If a less stiff restrainer is used, cumulative energy dissipation potential is reduced considerably due to pinched hysteresis loops and strain ratcheting. Applied end moments are found to have a linear effect on the RRS that can be modeled by superposition of the buckling effect plus end moment.
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Atlayan, Ozgur. "Hybrid Steel Frames." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/50562.
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The buildings that are designed according to the building codes generally perform well at severe performance objectives (like life safety) under high earthquake hazard levels. However, the building performance at low performance objectives (like immediate occupancy) under low earthquake hazards is uncertain. The motivation of this research is to modify the design and detailing rules to make the traditional systems perform better at multi-level hazards.This research introduces two new structural steel systems: hybrid Buckling Restrained Braced Frames (BRBF) and hybrid steel Moment Frames (MF). The "hybrid" term for the BRBF system comes from the use of different steel material including carbon steel (A36), high-performance steel (HPS) and low yield point (LYP) steel. The hybridity of the moment frames is related to the sequence in the plastification of the system which is provided by using weaker and stronger girder sections. Alternative moment frame connections incorporating the use of LYP steel plates are also investigated.
The hybrid BRBF approach was evaluated on seventeen regular (standard) frames with different story heights, seismic design categories and building plans. By varying the steel areas and materials in the BRB cores, three hybrid BRBFs were developed for each regular (standard) frame and their behavior was compared against each other through pushover and incremental dynamic analyses. The benefits of the hybridity were presented using different damage measures such as story accelerations, interstory drifts, and residual displacements. Collapse performance evaluation was also provided.
The performance of hybrid moment frames was investigated on a design space including forty-two moment frame archetypes. Two different hybrid combinations were implemented in the designs with different column sections and different strong column-weak beam (SC/WB) ratios. The efficiency of the hybrid moment frame in which only the girder sizes were changed to control the plastification was compared with regular moment frame designs with higher SC/WB ratios. As side studies, the effect of shallow and deep column sections and SC/WB ratios on the moment frame behavior were also investigated.
In order to provide adequate ductility in the reduced capacity bays with special detailing, alternative hybrid moment frame connections adapting the use of low strength steel were also studied.
PhD
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Boston, Megan. "Reducing Residual Drift in Buckling-Restrained Braced Frames by Using Gravity Columns as Part of a Dual System." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3204.
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Severe earthquakes cause damage to buildings. One measure of damage is the residual drift. Large residual drifts suggest expensive repairs and could lead to complete loss of the building. As such, research has been conducted on how to reduce the residual drift. Recent research has focused on self-centering frames and dual systems, both of which increase the post-yield stiffness of the building during and after an earthquake. Self-centering systems have yet to be adopted into standard practice but dual systems are used regularly. Dual systems in steel buildings typically combine two types of traditional lateral force resisting systems such as bucking restrained braced frames (BRBFs) and moment resisting frames (MRFs). However, the cost of making the moment connections for the MRFs can make dual systems costly. An alternative to MRFs is to use gravity columns as the secondary system in a dual system. The gravity columns can be used to help resist the lateral loads and limit the residual drifts if the lateral stiffness of the gravity columns can be activated. By restraining the displacement of the gravity columns, the stiffness of the columns adds to the stiffness of the brace frame, thus engaging the lateral stiffness of the gravity columns. Three methods of engaging the stiffness of the gravity columns are investigated in this thesis; one, fixed ground connections, two, a heavy elastic brace in the top story, and three, a heavy elastic brace in the middle bay. Single and multiple degree of freedom models were analyzed to determine if gravity columns can be effective in reducing residual drift. In the single degree of freedom system (SDOF) models, the brace size was varied to get a range of periods. The column size was varied based on a predetermined range of post-yield stiffness to determine if the residual drift decreased with higher post-yield stiffness. Three and five story models were analyzed with a variety of brace and column sizes and with three different configurations to activate the gravity columns. Using gravity columns as part of a dual system decreases the residual drift in buildings. The results from the SDOF system show that the residual drift decreased with increased post-yield stiffness. The three and five story models showed similar results with less residual drift when larger columns were used. Further, the models with a heavy gravity column in the top story had the best results.
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Kinali, Kursat. "Seismic Fragility Assessment of Steel Frames in the Central and Eastern United States." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14528.
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The Central and Eastern United States (CEUS) is a region that is characterized by low frequency-high consequence seismic events such as the New Madrid sequence of 18111812. The infrequent nature of earthquakes in the region has led to a perception that the seismic risk in the area is low, and the current building stock reflects this perception. The majority of steel-framed buildings in the CEUS were designed without regard to seismic loads. Such frames possess limited seismic resistance, and may pose an unacceptable risk if a large earthquake were to occur in the region. A key ingredient of building performance and seismic risk assessment is the fragility, a term that describes the probability of failure to meet a performance objective as a function of demand on the system. The effects of uncertainties on building seismic performance can be displayed by a seismic fragility relationship. This fragility can be used in a conditional scenario-based seismic risk assessment or can be integrated with seismic hazard to obtain an estimate of annual or lifetime risk. The seismic fragility analyses in this study focus on steel frames that are typical of building construction in regions of infrequent seismicity; such frames have received little attention to date in building seismic risk assessment. Current steel building stock in Shelby Co., TN has been represented by five code-compliant model frames with different lateral force-resisting systems, i.e., braced-frames, partially-restrained moment frames and a rigid moment frame. The performance of model frames under certain hazard levels was assessed using fragility curves. Different rehabilitation methods were discussed and applied. Results indicate that PR frames behave better than expected and rehabilitated frames perform quite well even under severe earthquakes.
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加藤, 基規, Motoki Kato, 昭. 葛西, Akira Kasai, 翔. 馬, Xiang Ma, 勉. 宇佐美, and Tsutomu Usami. "二重鋼管型座屈拘束ブレースの繰り返し弾塑性挙動." 土木学会, 2004. http://hdl.handle.net/2237/8531.
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Kato, Motoki, 勉. 宇佐美, Tsutomu Usami, 昭. 葛西, Akira Kasai, and 基規 加藤. "座屈拘束ブレースの繰り返し弾塑性挙動に関する数値解析的研究." 土木学会, 2002. http://hdl.handle.net/2237/8463.
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宇佐美, 勉., Tsutomu USAMI, 基規 加藤, Motoki KATO, 昭. 葛西, and Akira KASAI. "制震ダンパーとしての座屈拘束ブレースの要求性能." 土木学会, 2004. http://hdl.handle.net/2237/8533.
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葛西, 昭., Akira Kasai, 健太 木戸, Kenta Kido, 勉. 宇佐美, Tsutomu Usami, 尚彦 渡辺, and Naohiko Watanabe. "多径間連続高架橋への制震ブレースの導入効果." 土木学会, 2005. http://hdl.handle.net/2237/8535.
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Liu, Jia-Hau, and 劉佳豪. "Effects of Frame Action on Seismic Performance of Gusset Plate Connections in Buckling-restrained Braced Frames." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/76232211560759535578.
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碩士臺灣大學
土木工程學研究所
98
The present study of this thesis is focus on the seismic performance of a gusset plate subjected to frame action in Buckling-Restrained Braced Frames (BRBF). In order to test the stress concentration effects on gusset palte edges induced by frame action, an equivalent sturt model was proposed to estimate the frame action forces on a gusset plate, and a new design criteria by considering frame action and brace action simultanesly was proposed. In order to interpret the difference of each design methods, i.e. the AISC design method, or the design method by considering frame action presented in this thesis, a totally five full-scale, one story BRBF was tested to investigate the seismic performace of gusset plates under frame action. Single gusset plates was used in Specimen 1 and 2, dual gusset plates was used in Specimen 3 to 5, and edge stiffeners was applied on the gusset plate edges in specimen 1 and 3, so as to identify the contribution of edge stiffeners on gusset plate edges. One of gusset plates in five specimens was buckled after test, which was designed using AISC method, and the others gusset plates, which was designed using the theoretical formula presented from this study, was all fine. From the test observation, the edge of gusset plates will suffer large stains by frame action, but the applying of edge stiffeners can reduce the maginitude of normal strains effectively on the edge of gusset plates, and it seems true that single gusset plates will suffer larger frame action compared with dual gussets. Besides the test results, nonlinear FEM program ABAQUS was used to simulate the responses of specimen. This study describes the detailed analytical model and the modeling techniques, such as material model, boundary conditions, initial imperfections. The cyclic base shear versus the story drift relationships obtained from the test and FEM analytical results are quite agreeable. The analytical result confirm that the magnitude of frame action forces on a gusset plate can be accurately simulated. And baed on the theortical formula presented in this thesis, the edge stresses can also be accurately predicted when compared with FEM analytical results, so as to confirm the proposed design method in this thesis.
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Fahnestock, Larry Alan. "Analytical and large-scale experimental studies of earthquake-resistant buckling-restrained braced frame systems /." Diss., 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3215835.
Full text
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Li, Yuan-Shing, and 李源興. "Analysis of Three-Story Frame with Concrete-Filled Tube Columns and Buckling Restrained Braces." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/72873920289139848681.
Full textAbstract:
碩士國立交通大學
土木工程系所
93
A 3-story frame with concrete-filled tube columns (CFT) and buckling restrained braces was tested in October 2003. The purposes of the test are discussing the seismic behavior of steel beam to CFT column connections and BRB in frame. For frame analysis and comparison of the result, nonlinear structural program, DRAIIN-2DX, is used. First step of analysis is modeling and simulating the sub-structure by DRAIN-2DX, then comparing the results with test. When the results of sub-structure model are matched with experiment, frame analysis is proceeded. Based on comparison of analysis and experiment, the results of simulating sub-structure are excellent, DRAIN-2DX can effectively predict the global stiffness and strength. For the frame analysis, the results of simulation in Phase I are fine. But because of the failure in the detail of frame, the error in simulating is added in Phase II. It is observed that considering the slab effect on the flexural strength of the steel beam leads to more accurate analysis results. Pushover analyses were performed to study the effect of joint stiffness of the panel zone on the nonlinear behavior of the frame. Compared to rigid joint, semi-rigid joint modeling results in slightly lower ultimate strength of the frame, but not the elastic stiffness of the frame.
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Lin, Ting-Li, and 林庭立. "Seismic Design and Tests of Joint in the Buckling Restrained K-Braced RC Frame." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/45beq6.
Full textAbstract:
碩士國立臺灣大學
土木工程學研究所
105
A Buckling-restrained brace (BRB) can develop full yield strength under large tensile and compressive strain reversals through its restraining member by preventing its steel core from undergoing flexural buckling failure. Thus, a BRB can effectively absorb seismic input energy. In recent years, a number of researches have confirmed BRBs can enhance the lateral stiffness, strength and ductility of building structures. Buckling restrained braces (BRBs) have been widely used as energy dissipation members for seismic resistant steel buildings. However, researches on applying BRBs in RC buildings are somewhat limited. The main reason could be that the BRB and RC are two different construction material, issues in the interface between the BRB and RC frame do not seem completely resolved yet. In this study, a beam-to-column joint sub-assemblage in the buckling-restrained K-braced RC frame is tested using cyclically increasing loads and displacements. This study first proposes a twelve-story RC example building with BRBs arranged in a zigzag manner. In order to study the seismic performance of the interface joint, this study select a joint in the tenth-floor and design its gusset plate, U-shape steel cast-in anchor and RC corbels following the provisions in the model steel and RC building codes. The performance of the joint connection details is evaluate through imposing cyclically increasing displacements and loads computed from using a PISA3D analytical model. The test results show that no evident failure of the U-shape steel cast-in anchor or RC corbels is observed. Tests confirm that the use of the proposed U-shape steel cast-in anchor as the interface for the BRB and RC frame can be successfully implemented into real RC frames. Test results show that the proposed BRB-to-RC connection details performed very well in the K-braced RC frame system. This study demonstrates that the proposed design and construction method are effective. In order to further study the seismic performance of the 12-story K-braced RC frame using BRBs, nonlinear response history analyses are conducted using a total of 240 (SLE, DBE and MCE) earthquakes ground motion records. Analysis results indicate that the ratios of maximum total BRB shear to base shear are about 23% (SLE), 21% (DBE) and 20% (MCE). The maximum inter-story drift ratios (IDRs) under the MCE and DBE earthquakes are 2.1% and 1.7%, respectively. Analysis results also suggest that the high mode effect is not very significant. It is found that the peak demand of the horizontal tension force on the steel cast-in anchor can be estimated by considering only 70% of the sum of the two horizontal force components computed from the two BRBs‘ maximum possible tension strengths. This study proposes the construction and design procedures of the joint in the K-braced RC frame using BRBs.
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Yang, Hsun-Horng, and 楊巽閎. "Seismic Design and Tests of a Full-scale 2-story RC Frame with Buckling Restrained Braces." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/34959292109285398718.
Full textAbstract:
碩士國立臺灣大學
土木工程學研究所
103
Buckling-restrained braces (BRBs) have been widely used nowadays in steel structures as it can provide high stiffness, strength and ductility, thereby effectively absorbing seismic input energy. Researches on effectively using BRBs for seismic retrofit of existing RC buildings have been reported. It has been found the construction of BRB and RC member interfaces are often difficult, mostly due to the tensile and shear strengths of post-installed anchors in concrete are limited, the size and effectiveness of the BRBs are restricted. In addition, researches on applying BRBs for new RC building constructions are somewhat limited. This research investigates the seismic design and analysis methods for using the proposed I-shape steel embedment as the interface for the BRB and RC members. Steel embedment must be designed to transfer the BRB normal and shear forces in order to improve the seismic performance of the RC frame buildings. In this study, a full-scaled two-story RC frame with BRBs (BRB-RCF) is tested with four hybrid tests and cyclic loading test. A36 steel BRBs are arranged in zigzag configuration. The design of gussets incorporates the BRB axial and RC frame actions, while the beam and column members comply with ACI318 seismic design provisions. The tasks of this study include: (a) analyze the frame action effect on gussets using the equivalent strut model; (b) develop the design method for the D-region; (c) develop the design and construction methods for the proposed steel embedment; (d) develop the simplified and refined analysis procedures for the BRB-RCF; (e) develop the complete design procedures for the BRB-RCF using the proposed steel embedment. This study is in close cooperation with Ms. Jie-Lun Huang. Details of the specimen response predictions and simulations can be found in Ms. Huang’s thesis. Under the 50/50 hazard level earthquake, the maximum 2nd story’s inter-story drift ratio (IDR) was 0.23%, while all members remained elastic. During the 10/50 level earthquake, BRBs’ and beam ends’ yielding occurred. In the 2/50 earthquake, the maximum 2nd IDR was 2.5%. After three hybrid tests, the specimen’s lateral force vs. deformation responses still remained very stable and the residual IDR was 0.47%. After the same 2nd 2/50 earthquake was applied as an aftershock, the specimen’s stiffness and strength remained pretty much the same, suggesting the BRB-RCF specimen have performed very well under the four, from small to very large, earthquake load effects. During the subsequent cyclic loading test, plastic hinge formed at the 1st-story column base when the IDR reached 1.4%. At this IDR level, all BRBs and RC members yielding have occurred and the sequence agreed well with the predictions. When both two stories reached an IDR of 3.5%, the lateral force vs. deformation response of the specimen was still very stable. In the 3rd IDR=3.5% cycle, because of all bottom bars in the two top beam ends have fractured, the 2nd story shear reduced by 15 %. Up to the 1st IDR=4.5% cycle, 1st story top gusset buckled first, leading to the subsequent flexural buckling of the 1st story BRB to occur also. This is consistent with the predicted results when the gusset’s effective length factor K is assumed 2.0, DCR is 1.05; and steel casing’s DCR is 0.95 for the 1st story BRB. In the 50/50 earthquake, the ratios of peak BRB shear and BRB-RCF shear are 52% and 70% for the 1st and 2nd story, respectively. Similar ratios can be obtained if a factor 0.7 is applied on the gross moment of inertia for RC members in the ETABS elastic model. In the 10/50 and 2/50 events, the ratios become about 60% and 70% for the 1st and 2nd story, respectively. These indicate that BRBs can provide a high lateral stiffness. At the end of 3rd 2.75% IDR cycle, the cumulative plastic deformation CPDs were 476 and 680 for 1st- and 2nd-story BRBs, respectively. The hysteresis energy dissipated ratio in the four hybrid tests are ranging between 60-94% for the 1st and 2nd stories, confirming that BRBs can effectively dissipate seismic input energy. This study demonstrates that the proposed design and construction methods for the steel embedment are effective. No failure of the steel embedment or gusset is observed in the tests. Test results confirmed that the ACI provisions and the softened strut-and-tie model can be effectively applied to prevent the D-region failure. Test results confirm that the gusset force demands are consistent with the predictions. This study proposed the construction and design procedures of the BRB-RCF using the proposed BRB-to-RC member connections.
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Hai, Pham Dinh, and 范廷海. "SEISMIC RESPONSES OF BUCKLING-RESTRAINED BRACED FRAMES AND SELF-CENTERING BRACED FRAMES." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/41018686274570051817.
Full textAbstract:
碩士國立臺灣大學
土木工程學研究所
99
The seismic response of Buckling restrained braced frames (BRBF) and self-centering braced frame (SCBF) is compared when used in building structures of 3 to 6 stories in height. Ten earthquake ground motion records with 10% probability of exceedance in 50 years (DBE level) and 2 % probability of exceedance in 50 years (MCE level) are used in this study. The SCBF system performs better than BRBF system in terms of mean interstory drift, and the SCBF system has significant smaller residual drifts than the BRBF.
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Pan, Kuan-Yu, and 潘冠宇. "Seismic Retrofit of Existing Reinforced Concrete Frames Using Buckling-Restrained Braced Frames." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/67435522159198035390.
Full textAbstract:
碩士國立臺灣大學
土木工程學研究所
102
With the advancement in earthquake engineering technology and seismic provisions, many existing old reinforced concrete (RC) structures do not meet the current seismic standards. Seismic retrofit using steel braced frames has been found as a popular method to improve the seismic performance of RC buildings. For this purpose, closely-spaced post-installed anchors are widely adopted in the interface between the RC and steel frames to transfer the seismic loads. It often requires a substantial amount of on-site work of hole drilling and installation of anchors on the RC members. In this research, three identical strong-beam-weak-column RC frames are retrofitted, each with or without a diagonal buckling-restrained brace (BRB) incorporated into a steel braced frame using WT sections on four sides. Instead of applying the post-installed anchors to transfer the seismic loads, high-strength mortar bearing blocks at the four corners of the RC frame are constructed. The loads in the steel frame are transferred to the RC frame through the bearing blocks. This approach can reduce the usage of large amount of post-installed anchors. The purpose of this research is to evaluate the performance of the retrofitted frame, and investigate the load transfer mechanism between the RC frame and the steel frame. In this study, cyclic loading tests were applied on two RC frames retrofitted with steel braced frames using BRBs (BRB-S-WTF and BRB-D-WTF), and on one RC frame retrofitted with the steel frame without the brace. Test results show that, the lateral strength of BRB-D-WTF continued to increase until reaching 3% drift ratio, and developed 1060kN story shear (3 times of the bare RC frame) before the BRB core fractured at the 5% drift ratio. When the brace is in compression, it imposes a compressive force near the tip of the frame corner. This compressive force may cause an RC joint failure or a corbel-type failure in the RC column. In this research, these two failure modes are evaluated using the softened strut-and-tie model. The strength of the compressive strut in the beam-to-column joint is 810kN. In the BRB-S-WTF specimen, the estimated maximum brace compressive force is 1025kN. Thus, the beam-to-column joint failure was predicted. In the BRB-D-WTF specimen, the estimated maximum brace compressive force is 807kN. Thus, no beam-to-column joint failure was anticipated. The predictions match the test results. The concrete compressive strength of the RC column is 25MPa. In the BRB-S-WTF specimen, the strength demand on the corbel computed using the softened strut-and-tie model is 25.1MPa and approximately equals 25MPa. Thus, it predicted that the corbel failure might occur. In the BRB-D-WTF specimen, the strength demand on the corbel is 19.5MPa and less than 25MPa. The model predicted that the corbel failure should not occur. These two predictions also match the test results. Therefore, it appears that the softened strut-and-tie model is effective in predicting the joint failure and corbel failure of the RC frame. In this research, a simplified method for estimating the lateral strength of the retrofitted structure and the internal forces of RC beams and columns is developed from observing the load transfer mechanism found in the Abaqus finite element model (FEM) analysis results. The estimated lateral strengths for the BRB-S-WTF and BRB-D-WTF specimens are 1120kN and 973kN, predicted the experimental results of 1289kN and 1018kN, respectively. This confirms that the proposed simplified method is effective for estimation of the lateral strength of the retrofitted frame, and computing the estimated internal force demands on RC frame members. This study proposes a design procedure for retrofitting existing RC frames with buckling-restrained braced frames.
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Saputro, Indra Rio, and 英德拉. "Seismic Performance of Braced Frames with Buckling Restrained Slit Pipe Dampers." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/2pkepb.
Full textAbstract:
碩士國立中央大學
土木工程學系
106
A new energy dissipation device that combined the BRB and pipe damper systems to form the buckling restrained slit pipe dampers (BRSPD) is proposed. This device incorporates a slit pipe damper that is limited by the inner tube. The outer tube was used as a restraining mechanism. Slit in the pipe is used to control energy dissipation and deformation capacity. This damper is designed to provide adequate hysteretic performance through core yielding under both tension and compression. A series of cyclic loading tests were conducted on the BRSPD and semi-rigid frames with the proposed devices. It was found that the BRSPD sustained significant strength and energy dissipation capability before reaching 2.5% drift ratio, if adequate number of slits in the core pipe was used. Comparisons of the test results showed that the frame strength was increased when the buckling restrained slit pipe dampers were adopted. Significant gains in strength, stiffness, deformation capacity and energy dissipation for framed structures with BRSPD justified the effectiveness of the proposed design.
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Pham, Thu-Hien, and 範萩賢. "Seismic Analyses of Self-Centering Braced Frames and Buckling-Restrained Braced Frames Using the Computer Program SAP2000." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/49534087029767317185.
Full textAbstract:
碩士國立臺灣大學
土木工程學研究所
100
Self-centering braced frames (SCBFs) and Buckling-restrained braced frames (BRBFs) demonstrate their advantages in seismic response due to no self-centering and buckling, respectively. This investigation focused on developing an improved understanding of challenges associated with computation of nonlinear response of two-dimensional building to recorded ground motions. For this purpose, two-dimensional models of not only self-centering brace along with buckling-restrained brace but also 6-story 10-m beam span of SCBFs and BRBFs – are developed in SAP2000 in order to compared to the result, which achieve from test perform and PISA3D study. The analysis of these models included cyclic pushover analysis for self-centering brace as well as buckling-restrain brace, in additional to nonlinear pushover plus seismic analysis for SCBFs and BRBFs at 4 ground motions recorded. It was found that modeling assumptions as well as different software may lead to significantly different response curves.
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Huang, YenChih, and 黃彥智. "Experimental Responses of Large Scale Buckling Restrained Brace Frammes." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/45089414840560078686.
Full textAbstract:
碩士國立臺灣大學
土木工程學研究所
90
Buckling restrained braced frame (BRBF) has been evolved into a very effective system for severe seismic application. Buckling restrained braces (BRBs) are commonly made from encasing a core steel cross-shape or flat bar member into a steel tube and confined by infill concrete. An unbonding material is placed between the core bracing and the concrete infill in order to reduce the friction while restrain the bracing from buckling. In the practical application of the BRBs, each brace-to-gusset connection requires two set of bolts and eight splice plates. In order to reduce the length and the number of bolts in the brace-to-gusset connection, the double-tee (or double-plate) double-tube (DPDT or DTDT) BRBs have been developed and extensively tested in National Taiwan University in the past few years. However, experimental data on the performance of large scale BRBF specimens is still very limited. Therefore, the objectives of this research include: 1) conducting tests to investigate the elastic stiffness, the inelastic responses of the BRBs and its connection details adopted in the Taipei County Administration Building (TCAB), 2) investigating the experimental and analytical responses of the single bay V-shaped BRBFs constructed with two BRBs in three different aspect ratios in length, 3) investigating the steel BRB core strain versus inter-story drift relationships, and 4) providing guidelines for the analysis and design of BRBF for severe seismic applications. Test results confirm that the elastic axial stiffness of the BRBs adopted in the TCAB can be accurately predicted by the effective axial stiffness considering the variation of the cross-sectional areas along the length of the steel brace. In addition, the inelastic component test results confirm that the strain hardening factors for BRBs made from SN400B and LYP235 steel by Nippon Steel Corporation are about 1.5 and 1.35 respectively for a peak core strain of 0.02. The differences between the peak compressive and tension forces are less than 7%. The two inelastic component test results confirm that, after applying the cyclic increasing strains (peak core strain=0.02) and the simulated near fault cyclic strains (peak core strain=0.06), the SN400B and LYP235 BRBs sustained 36 and 48 cycles, respectively of cyclic fatiguing strains of 0.02 before fracture occurred in the steel cores. Tests conducted on the 0.5-scale one-bay one-story V-shaped BRBF, constructed according to the structural members and connections at16th floor of the TCAB, confirm that the frame specimen can satisfactorily sustain the inter-story drift time history computed from the nonlinear dynamic frame response analysis for two levels (PGA=0.23 and 0.46g) of earthquake. The subsequent three V-shaped DPDT-BRBF tests confirm that the steel brace core strain demands can be satisfactorily predicted from the story drift demand by geometry and incorporating the ratio of the work point-to-work point dimension to the inelastic core length. Test results also reveal that at a large story drift, the tensile strain in the tension brace was always greater than the compressive strain in the compression brace. This somewhat suggests that the peak compression and tension forces have a tendency to self-equilibrate and reach a reduced unbalanced vertical force components resisted by the horizontal beam member.
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Yeng, Chih-Hsiao, and 嚴致孝. "Torsional Response of Welded End-Slot Buckling-Restrained Brace." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/60512069817618296400.
Full textAbstract:
碩士國立臺灣大學
土木工程學研究所
101
The welded end-slot buckling-restrained brace (WES-BRB) features a reduced length of the connection segment thus improving the stability of the BRB end-to-gusset connections. The WES-BRB core member consists of one core plate slotted along the centerline at two ends, and two rib plates welded perpendicular to the core plate along two edges of the slot in opposite surfaces of the core plate. The core plate is oriented perpendicular to the gusset plate. By using the slot on the core plate, the core member can be inserted into the gusset plate before welding the edges of the rib and core plates onto the gusset plate. Numerous brace component and frame tests have confirmed the excellent performance of the WES-BRBs. However, a very slight twisting of about 1.0 to 2.0 degrees along the BRB axis could be detected when it is subjected to an axial strain of 0.03. The objectives of this research are to investigate the WES-BRB twisting mechanism and to develop the improved designs for a reduced twist angle. Under the axial load, it can be found that the WES-BRB twisting is attributed to two reasons: (a) When an axial load passes through the transition segment, a pair of shear forces of equal magnitude but in opposite direction will be developed on the cross sections of the two rib plates due to the tapered transition shape. The shears and their distance form the torque and twist the cross section. (b) Near the connection, the core member can be viewed as two angles. The BRB end-to-gusset welding details result in a shear lag effect for each angle. This means the axial force acts through the centroid of one angle in the core segment, but through the centroid of the welds at the end connection. The eccentricity between the above two centroids will develop two pairs of shear force components, each equal in magnitude and opposite in direction. These would form the torque and twist the cross section. Reducing these eccentricities would reduce the twist angle. Thus, the followings two approaches are proposed to reduce the eccentricities: (a) considering the same end connection length to the gusset, but applying a balanced weld detail in arranging the weld length on different edges; (b) re-arranging the dimensions of the core and rib plates. In this research, past test results of one WES-BRB are firstly analyzed using ABAQUS finite element model (FEM). The analytical axial force versus axial and torsional deformation relationships well agree with the test results. Furthermore, the effectiveness of the proposed methods in reducing the twist angle is confirmed by the FEM analyses. Based on analysis results, a total of five WES-BRB specimens, including two with square restraining steel casing and three with rectangular restraining steel casing, are designed and tested at NCREE by using cyclic loading procedures. One of the WES-BRB with square steel casing adopts the balanced weld, and three with rectangular steel casing adopt two types of transition segment while different thicknesses for the core and rib plates are used. Key test results include: (a) the twist angles of the steel casing are slightly greater than the core section outside the steel casing in all the five specimens. Under the core strain of 0.03, the maximum twist angle and the maximum difference between the positive and negative twist angles in one loading cycle are less than 1.5 and 2.5 degrees, respectively; (b) it is confirmed that a smaller eccentricity results in a smaller twist angle; (c) compared with the weld-all-around connection details, using the balanced weld reduces the maximum twist angle by about 50%; (d) torsional response has no apparent influences on the stiffness, strength or cumulative plastic deformation capacity of all specimens; (e) all specimens possess good fatigue performance and the fatigue life can be predicted using the empirical results proposed by others. This research investigates the twisting mechanism of the WES-BRB and confirms the effectiveness of the proposed designs in reducing the twist angle. Results can be used to advance the seismic design of WES-BRB and the connections.
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Huang, Jie-Lun, and 黃潔倫. "Seismic Design and Response Analysis of RC Frames with Buckling Restrained Braces." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/94553511371981238892.
Full textAbstract:
碩士國立臺灣大學
土木工程學研究所
103
The buckling-restrained brace (BRB) has been evolved into a cost-effective energy dissipation member for seismic resistant steel buildings. A BRB can develop full yield strength under both tension and compression through its restraining member by preventing its steel core from undergoing flexural buckling failure. In recent years, many studies and tests have proved BRBs can improve stiffness, strength, ductility and energy dissipation mechanism for structures. BRBs have been widely applied in steel structures in the past decades. However, researches on applying BRBs to new reinforced concrete frames (RCFs) are somewhat limited. This study consists of two parts. In order to study the performance of RC frame with BRBs (BRB-RCF) under earthquakes, in the first part, an analytical model is constructed using PISA3D for predicting the responses of a two-story BRB-RCF tested at NCREE. The full-scale two-story BRB-RCF has been tested using four hybrid tests and cyclic loading test. Details of the specimen design and test results can be found in Mr. Hsun-Horng Yang’s thesis. Ground motions adopted in the tests are selected by using the prediction model analyses and 60 ground motion records. After the tests, the prediction model is calibrated into a simulation model based on the experimental results. Very satisfactory agreements with the test results can be achieved from the simulation model analyses. In order to further study the seismic performance of low-rise BRB-RCFs, this study uses six-story building design examples, one BRB-RCF and one RC moment resisting frame (MRF). The six-story BRB-RCF and MRF analytical models are constructed using PISA3D and the proposed modeling methods. For the purpose of saving analysis time while achieving accuracy, a simplified model is proposed for the 6-story BRB-RCF response history analyses. The analytical results show that the ratios of maximum total BRB shear and BRB-RCF shear in transverse direction are about 35% (50/50 hazard level earthquake), 40% (10/50 hazard level earthquake) and 40% (2/50 hazard level earthquake). These are larger than those computed for longitudinal direction with 24% (50/50 hazard level earthquake), 26% (10/50 hazard level earthquake) and 28% (2/50 hazard level earthquake). The maximum story drift in the BRB-RCF and MRF under the 2/50 hazard level earthquake are 1.5% and 1.8%, respectively. In order to improve the BRB efficiency in the BRB-RCF, this study propose to configure the RC BRBFs as primary lateral force resisting systems, and treat the remaining RC beam and column members as a gravity system. This scheme can significantly reduce the sizes of a number of RC beams and columns and improve the efficiency of BRBs. This study uses the PISA3D to construct the two-dimensional analytical model of one half of the building structure in transverse direction and perform nonlinear dynamic analysis. Analysis results confirm that the RC-BRBF scheme enables the total BRB shear ratio of the RC-BRBF to increase to 75%, while the story drift responses are similar to the aforementioned BRB-RCF system. This series of experimental and analytical researches has confirmed the effectiveness of the design, fabrication and modeling methodologies for the proposed BRB-RCF. Tests have confirmed that the use of the proposed steel embedment as the interface for the BRB and RC members can be successfully implemented into real RC frames. Analytical results of the 6-story RC-BRBF and BRB-RCF show that a large shear demand exists in the in D-region of the lower floor beams. These beams must be designed wider than those in the upper floor beams. In addition, the BRBs in the proposed RC-BRBF or BRB-RCF are arranged in a zigzag configuration. This should reduce the axial force demand on beams. This paper discusses the axial force demands computed from the response history analyses. Implementing the BRBs into low-rise RC building can somewhat reduce the responses of the structures. However, due the significant stiffness of RC members, the sizes and their effectiveness of the BRBs in reducing the seismic drift response of RC buildings is limited.
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鄭凱中. "Influence of Inspection Windows on Strength of Buckling Restrained Brace." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/68176866850097664177.
Full textAbstract:
碩士逢甲大學
土木工程學系
102
Because countries around the world always have been plagued by earthquake disasters, and meanwhile the unpredictability of earthquakes leads no effective way to deal with earthquake disasters, therefore how to improve structure seismic resistant has been researched wildly. Buckling Restrained Braces is one kind of the damper in structural passive control, it been used at construction recently. It is proved by experiment that Buckling Restrained Braces not only can strengthen stiffness of structure and absorb seismic energy but also can reduce traditional braces buckling caused from axial compression when earthquake happened. But former Buckling Restrained Braces is closed completely, so that it can’t determine if any internal damage after earthquakes. This thesis presents Buckling Restrained Braces with inspection windows which opened in the strong axis and weak axis of the confinement element, observing the forced element deformation through inspection windows, and study the strength of Buckling Restrained Braces affected by inspection windows opened. This is a study for standard and Fatigue experiments about Buckling Restrained Braces specimens with inspection windows. From experimental results, the hysteretic behavior of the specimen is quite stable and full, and the tension and the compression difference is quite small, and the cumulative inelastic axial deformation is much larger than the prescribed norms. These tests also confirmed the Buckling Restrained Brace has a good energy dissipation capacity after inspection windows opened, and deformation of main forced element forced can be observed through inspection windows.
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Huang, Wei-chung, and 黃維崇. "Research on Multi-Curve Buckling Restrained Brace without Lateral Support." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/65956200777328013663.
Full textAbstract:
碩士逢甲大學
土木工程所
97
Recently, engergy absorption and base isolation technolgies in seismic mitigation for structures have been developed to resist earthquakes. Many studies on structural control methods and devices have been unfolded. Different control methods and devices have their own merits and deficiencies. The advanced BRBs proposed in this study include the new multi-curve buckling restrained brace without the lateral support and new multi-curve buckling restrained brace with lateral support. The advanced BRBs were made of the steel material without debonding material or mortart. In addition, it can be found from experiment results that the mechanical behavior of the advanced BRBs were very stable under the cyclic loadings and that the distinction between the tensile and compressive forces was much smaller than the provision requirement. Furthermore, the nonlinear behavior under cyclic loadings can be well simulated by the Wen’s modal in an increment form.
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CHOU, YU-CHIN, and 周郁欽. "Experimental Study of full Scale Buckling Restrained Brace with Inspection Windows." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/emby72.
Full textAbstract:
碩士逢甲大學
土木工程學系
106
The inestimable loss due to earthquakes happened all over the world in recent years; as far as earthquake is still unpredictable, it is an effective action to strengthen constructions to further improve the resistance to earthquakes and the safety within buildings. Buckling Restrained Brace -- BRB is one kind of the damper in structural passive control, which is widely implemented in architectural construction nowadays; however, traditional BRB is fully-enclosed, steel core cannot be directly observed the attrition or damage conditions during the earthquake from the exterior appearance. The study illustrates the BRB with inspection windows and full-scale test under the specifications of AISC Seismic Provisions for Structural Steel Buildings in 2010 (AISC 2010) in order to observe the mechanical behaviors and characteristics of full-scale BRB with inspection windows. Furthermore, the study also utilizes Standard Loading Protocol and Low-Cycle Fatigue Loading Protocol for the purpose of examining residual strains from inspection windows on the BRB to determine whether BRB is damaged in order to have immediate action of maintenance or replacement, making the utmost use of BRB.
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Fang, Pin-Jyun, and 方品鈞. "Experiments and Analysis of Improved Constraining Component of Reinforced Buckling Restrained Brace." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/88988431268947606394.
Full textAbstract:
碩士逢甲大學
土木工程所
97
In recent years, buckling restrained braces have been used in the buildings in seismic mitigation. Many researchers have shown that the buckling retrained brace (or unbonded brace) is able to not only strengthen stiffnesses of a structure but can also absorb seismic energy. After many tests, it has been proven that the BRB can lessen structural responses without buckling. However the conventional buckling restrained brace still has shortcomings such as: (1) complicated assembly procedures (2) long time for curing concrete during manufacturing and (3) problems with fire protection. Therefore, a new type of brace called the Reinforced Buckling Restrained Braces (RBRB) has been develop. Reinforced Buckling Restrained Braces has been proposed to improve the shortcomings of the traditional BRB. In addition to Reinforced Buckling Restrained Braces,the similar concept has been used principle to develop Simplified Reinforce Buckling Restrained Braces (S-RBRB) and Multi-Curved Reinforce Buckling Restrained Braces (MC-RBRB). After the cyclic loading test, it has been proven that the RBRB, S-RBRB and MC-RBRB posses very stable mechanical behavior. The Improved Constraining Component of RBRBs has been proposed in this study to ameliorate manufacturing procedures and to enhance the efficiency of BRBs. It demonstrated from experimental results that the improved constraining component of BRBs remained stable hysteresis loops after yielding. Furthermore, the nonlinear behavior of the new BRB can be well simulated by using the Wen’s model in an incremental from developed by C.S. Tsai.
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李志堅. "Influence of Windowed Lateral Support Element on Strength of All-Steel Buckling Restrained Brace." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/56418993203002263992.
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喬偉崧. "Influence of Angles and Sizes of Enlarged Segment on Buckling Restrained Brace with Inspection Windows." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/87625394862739819036.
Full textAbstract:
碩士逢甲大學
土木工程學系
102
The buckling restrained brace, an energy dissipation device in structural control, has long been widely used in structures, and has been experimentally proven to provide an energy dissipation capacity comprehensively superior to that of the traditional diagonal brace. Because traditional buckling restrained braces are completely enclosed, examination of the exterior following an earthquake cannot reveal internal damage. This paper proposes a buckling restrained brace with inspection windows that enable observation of the interior both during production and after earthquakes. To further improve the energy dissipation capacity of the buckling restrained brace that has inspection windows, testing was performed by changing the size and angle of the central segment. The results of the tests indicated that the central segment exerts little influence on the strength of the buckling restrained brace with inspection windows. When the enlarged segment was short, cumulative deformation of the inelastic axis increased.
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Chang, Chieh-An, and 張捷安. "Research on the Local Bulging Failure of Buckling-Restrained Brace Restraining Members with Flat Steel Core." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/78355159326471620121.
Full textAbstract:
碩士國立臺灣大學
土木工程學研究所
102
Buckling-restrained braced frame systems are widely used for seismic buildings in recent years. In order to increase the usable floor space in the building, developing the thin BRB (nBRB) becomes an important task and challenge. The seismic design methods and performance evaluation of nBRBs are the priorities of this research. When the nBRB using flat core plate is subjected to a large compressive strain, the high mode buckling wave will form. The wave crests would be in contact with the mortar and create lateral forces on the restraining members. The local bulging failure may occur if the steel casing is not strong enough to resist the lateral force. In this study, the lateral force induced by the maximum compressive force of the BRB is computed from the geometry of the high mode buckling considering the buckling wavelength, unbonding layer thickness, and a reduced thickness of the core plate due to Poisson effect. The compressive strength decreases severely when the bulging failure occurs. In order to achieve a conservative design, it is assumed that the infill mortar contributes no resistance but spreads lateral forces out into outward pushing forces on the inner surface of the steel casing. The resistance of the steel casing wall preventing the local bulging failure is calculated by the limit analysis of plates. Three local bulging load stages are considered including uniformly distributed area load, triangularly distributed area load, and line load acting on the inner surface of steel casing, respectively. Fourteen nBRB component tests have been conducted in the previous studies. In this research, eight component tests on specimens varying in the core plate width, cyclic loading procedures, and the mortar strength are conducted at NCREE. There are four different types of loading procedures. Such as increasing, decreasing, and singular with the maximum compressive strain of 3.5%. The constant loading procedure applies the cyclic core strain under 3%. Test results show that the local bulging failures occur after exceeding the maximum core strain of 3.5%. The high mode buckling wavelength is about 9 to 10 times the core plate thickness. It is observed that different loading procedures affect the local bulging failure instants. The proposed design method satisfactorily predicts the occurrence of the local bulging failure of the nBRB under extreme loading procedures. The design method is conservative when the core plate width to the steel casing width ratio increases. It is recommended that the core plate-to-casing width ratio be greater than 0.3 for nBRB. Test results confirm that using 95Mpa-high compressive strength mortar can enhance nBRB’s life. Finite element model (FEM) analysis results indicate that the lateral outward pushing forces from the buckled core plate can be effectively predicted by the proposed design method. The maximum compressive strength of the nBRB and the geometry of high mode buckling waveform can be conveniently incorporated into the calculation of the lateral force. The FEM shear stress distributions in the mortar are similar to the assumptions made for the mortar loading path. Based on the tests and analysis on the 22 nBRB specimens, it is confirmed that the proposed design method can be applied for the seismic design of nBRBs to prevent the local bulging failure of steel casing.