Download or read book Seismic Response of Diagonally Reinforced Coupling Beams with Headed Bars written by Dean G. Dugas and published by . This book was released on 2002 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Ductile coupled walls are important elements in resisting seismic loads in tall buildings. Ductile coupling beams must possess excellent energy absorption characteristics and significant ductility. Coupling beams with small span-to-depth ratios typically utilize diagonal bars to resist the shear and flexure. The present method for the confinement of the diagonal reinforcement requires closely spaced seismic hoops. This type of coupling beam is difficult to assemble and has several areas of congested steel bars. To simplify construction and ease the steel congestion, it is proposed that the confinement of the diagonal bars be provided by headed bars." --

Download or read book Seismic Response of Diagonally Reinforced Coupling Beams with Varied Hoop Spacings written by Brian Howard and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "Reinforced concrete shear walls are commonly used seismic force-resisting systems in high-rise structures. Shear walls with regular openings for elevators or staircases at floor levels act as a system of two shear walls linked by concrete beams located above and below the openings. These shear wall systems are referred to as coupled walls. Ductile coupling beams are important components of ductile coupled walls due to their inherent high energy dissipation properties and stable failure mechanisms. Coupling beams with low span to depth ratios typically include diagonal reinforcement to resist shear and flexural forces induced by wind or seismic loads. In order to achieve the necessary ductility, the current CSA Standard A23.3-14 (CSA, 2014) limits the spacing between the buckling prevention ties (hoops) which confine the diagonal reinforcing bars to the lesser of 24dhoop, 6db or 100 mm. These stringent requirements for ductile diagonally reinforced coupling beams are commonly applied to moderately ductile and conventional construction cases. To simplify the construction of the coupling beams and provide realistic alternatives for the moderately ductile and conventional construction cases, the effect of an increased spacing of the buckling prevention ties in the coupling beams is investigated. Reversed cyclic loading tests were carried out on fifteen reinforcing bar specimens as well as four full-scale coupled shear wall specimens. The hysteretic response of the full-scale coupled wall specimens determined that an increased spacing of the buckling prevention ties performs adequately for the moderately ductile and conventional construction cases. Further research should be carried out to investigate the increase in resistance due to the longitudinal restraint of the coupling beams offered by the structure's floor slabs." --

Download or read book Seismic Behavior of Steel Fiber reinforced Concrete Coupling Beams Without Diagonal Bars written by Angel Luis Perez Irizarry and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Medium- to high-rise buildings in regions of high seismicity in the USA often rely on coupled wall systems for lateral load resistance. The strength, stiffness, as well as deformation and energy dissipation capacities of coupling beams greatly influence the response of coupled wall systems. However, the high shear stresses and deformation demands coupling beams are expected to sustain during strong ground motions require the use of complex reinforcement detailing that includes large amounts of transverse and diagonal reinforcement, which makes them difficult and time-consuming to construct. Previous studies have shown that the use of a tensile strain-hardening, steel fiber-reinforced concrete (SFRC) reinforced with high-strength (330 ksi) hooked fibers at a 1.5% volume fraction allowed significant reductions of transverse reinforcement and the elimination of diagonal bars in coupling beams with span-to-depth ratios of 2.2 or greater. Despite the substantial reinforcement reduction and observed adequate coupling beam behavior, the use of SFRCs for coupling beam design has been limited in practice, in part due to experimental data on the behavior of SFRC coupling beams without diagonal bars being limited to a single fiber type and dosage. In this study, the behavior of SFRC coupling beams without diagonal bars, constructed with various SFRCs, was experimentally investigated. To this end, eight large-scale precast SFRC coupling beams without diagonal bars were tested under large displacement reversals. The main experimental variables considered were coupling beam span-to-depth ratio (3.0 and 2.0) and peak shear stress [7 to 12 [sqrt]f'[c]], fiber type, and fiber dosage. Three different hooked steel fibers and fiber volume fractions (1.0, 1.25, and 1.50%) were considered in this study for a total of six different SFRCs. Test results showed that coupling beams without diagonal bars can achieve drift capacities exceeding 5% while subjected to peak shear stresses between 6 and 10 [sqrt]f'[c]. Based on results from this and previous investigations, performance criteria for SFRCs based on ASTM C1609-12 test results were proposed. The proposed SFRC performance criteria were tied to coupling beam span-to-depth ratio and peak shear stress demand to achieve a target coupling beam drift capacity of 6%. Additionally, design recommendations that include reinforcement detailing, calculation of flexural and shear strength, and a lumped plasticity model for simulating the shear versus drift envelope response of SFRC coupling beams were proposed. The proposed model accounts for inelastic flexural rotations, concentrated rotations due to reinforcement slip, and shear sliding. The simple model showed good agreement with experimental results from this and other studies.

Download or read book Experimental Study on Seismic Performance of Reinforced Concrete Coupling Beams and Rectangular Squat Walls with Innovative Reinforcement Configurations written by Poorya Hajyalikhani and published by . This book was released on 2016 with total page 213 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reinforced concrete core walls, coupled by diagonally reinforced coupling beams (DCBs), are a very efficient seismic force resisting system for medium- to high-rise buildings. The diagonal reinforcing bars in DCBs are most effective when the beam has a span-to-depth ratio, ln/h, less than 2. Modern construction, due to architectural requirements, typically requires span-to-depth ratios between 2.4 to 4, which leads to a very shallow angle of inclination of the diagonal reinforcement (generally between 10 to 20 degrees). The lower angles of inclination, combined with the detailing requirements specified in ACI 318, results in reinforcement congestion as well as design and construction difficulties. These issues with DCBs can be considerably minimized by utilizing an innovative and simplistic reinforcing scheme as investigated in this study. This reinforcement scheme consists of two separate cages similar to those used for typical beams in RC special moment frames. The proposed coupling beam has high elastic stiffness and acts like a conventional coupling beam under small displacements. Upon large displacements, cracks begin developing at the mid-span and mid-height of the beams where the narrow gap is located, gradually propagating towards the beam's ends. The cracks eventually separate the coupling beam into two slender beams where each has nearly twice the aspect ratio of the original coupling beam. This essentially transforms the shear-dominated behavior into a flexure-dominated behavior, as conventional slender beams. Because damage initiates from the center of the beam; then spreads towards the ends, the beam's ends maintain their integrity even under very large displacements, thereby eliminating the sliding shear failure at the beam-to-wall interface. Preliminary testing results on half-scale coupling beam specimens with span-to-depth ratio of 2.4 showed that coupling beams with the proposed reinforcement scheme were able to sustain high shear stresses and large rotations before strength degradation occurred. Subsequently, six rectangular squat wall specimens with height-to-length ratio 0.5 and 1, which were designed based the second innovative design concept using discrete confining cages to reinforce the web of the walls, were tested under lateral displacement reversals. Each wall consisted of several separate cages similar to those used for typical beams in RC special moment frames. The response of squat wall specimens showed very high shear strength and stiffness, while maintain adequate ductility due to well confinement of the wall.

Download or read book Proceedings of the Canadian Society of Civil Engineering Annual Conference 2022 written by Rishi Gupta and published by Springer Nature. This book was released on 2023-08-05 with total page 1180 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book comprises the proceedings of the Annual Conference of the Canadian Society of Civil Engineering 2022. The contents of this volume focus on specialty conferences in construction, environmental, hydrotechnical, materials, structures, transportation engineering, etc. This volume will prove a valuable resource for those in academia and industry.

Download or read book Experimental Study of Reinforced Concrete Coupling Beams with Axial Restraint written by Bahaa Ahmad Burhan Al-Khateeb and published by . This book was released on 2021 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt: Coupled shear walls are a lateral load resisting system used in buildings to resist seismic and wind loads. In coupled walls, coupling beams span between adjacent shear walls and are typically located at floor level. Coupling beams are designed to yield and form plastic hinges before the wall piers. Damage patterns observed after the 2010-2011 Canterbury earthquake sequence in New Zealand showed instances in which coupled walls did not behave as intended in design, as plastic hinges formed at the base of the wall piers but not at the beam ends. The Canterbury Earthquakes Royal Commission suggested that this undesirable response may have been caused by coupling beam axial restraint from walls and floors increasing the strength of the coupling beams.To better understand the effect of axial restraint on coupling beam behavior, seven one-half-scale reinforced concrete coupling beams were designed using ACI 318-19 and were constructed and tested. The main test variables were span-to-depth ratio, reinforcement configuration (conventional or diagonal), primary reinforcement ratio and bar diameter, and level of axial restraint. Six beams consisted of three identical pairs, with the two beams in each pair tested at a different level of constant stiffness axial restraint.Test results indicated that axial restraint, which is not included in the ACI 318-19 equation for nominal shear strength of diagonally reinforced coupling beams, increased the beam strength. Axial restraint also influenced the load-displacement responses of the beams and the observed damage patterns. The conventionally reinforced beams were observed to yield in shear, while damage concentrated at the ends of the diagonally reinforced beams. The onset of significant strength degradation in the diagonally reinforced beams was associated with buckling of diagonal reinforcement rather than crushing of confined concrete, such that variation in axial compression on identical pairs of beam did not lead to a significant difference in deformation capacity. Test beams with #6 diagonal reinforcement had improved deformation capacity over those with #4 diagonal reinforcement, due to the influence of the ratio of transverse reinforcement spacing to diagonal bar diameter (s/db) on bar buckling.

Download or read book Effect of Hoop Spacing on the Seismic Response of Coupling Beams written by Nicholas Adomat and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "Coupled walls are among the most commonly used seismic force resisting systems within mid-to-high rise reinforced concrete structures in Canada. Coupling beams are a crucial component of the coupled wall system due to their effective energy dissipation capabilities and high ductility. In situations where coupling beams have a span-to-depth ratio greater than 4.0, conventional longitudinal reinforcement and transverse hoops are typically used to resist the applied moments and shear forces. The 2014 version of the CSA A23.3 Standard provides specific hoop spacing requirements which help ensure that flexural members subjected to seismic loading are designed to avoid brittle failure modes. However, these hoop spacing requirements are identical for both ductile and moderately ductile flexural members. As ductile and moderately ductile systems are meant to have significantly different energy dissipation capabilities and inelastic behaviour, a differentiation in hoop spacing between these two systems is proposed. Specifically, this differentiation would be accomplished by a relaxation in hoop spacing requirements for moderately ductile members as well as stricter hoop spacing requirements for ductile members. In order to investigate the validity of this proposal, four coupling beam specimens with varying ductility and hoop spacing were subjected to reversed cyclic loading. The performance of the coupling beams was based on the following metrics: predicted capacity and maximum load achieved, displacement ductility, cumulative energy dissipation, stiffness degradation, and load sustainability. In addition to the coupling beam specimens, reversed cyclic tests were carried out on "bare" 15M, 20M, and 25M reinforcing steel specimens. The results of the "bare" bar tests were used to provide insight on how the unbraced length of reinforcement affects buckling.The hysteretic response of the coupling beam specimens showed that a relaxation in hoop spacing requirements for moderately ductile members may be possible. In terms of the ductile specimens, the current hoop spacing requirements seem appropriate. It is suggested that further research be carried out in this area to confirm the validity of the results. " --

Download or read book Influence of Coupling Beam Axial Restraint on Analysis and Design of Reinforced Concrete Coupled Walls written by Kamiar Kalbasi Anaraki and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reinforced concrete coupled shear walls are effective systems for resisting lateral loads, often used in mid to high-rise buildings in earthquake-prone areas. These walls usually feature openings for doors and windows, dividing a solid wall into two separate piers. The strength of these walls comes not just from the sum of two individual piers, but from wall piers cross-section and the framing action between the wall piers through the coupling beams. In an earthquake, coupling beams serve as fuse elements, distributing seismic energy throughout the height of the building. This not only reduces the bending stress at the base of the shear walls but also improves their overall strength, stiffness, and resistance to lateral forces. Properly designed coupling beams, with sufficient longitudinal, diagonal, and confinement reinforcement, can effectively absorb energy while maintaining significant strength and stiffness, even under large deformations.The objective of this study was to develop, calibrate, and validate a new coupling beam model that integrates axial and lateral interactions under cyclic loading conditions. This model aims to reliably predict the elastic and inelastic responses of diagonally reinforced coupling beam elements. The proposed analytical model incorporates a fiber-based concrete cross-section, and diagonal trusses to account for axial interactions between the nonlinearity in the steel and concrete along the beam's length. This feature allows the model to capture additional axial force developed in the element due to the axial restraint from the wall piers, thereby increasing or decreasing the lateral strength of the beam. Additionally, the model includes the slip-extension behavior between the coupling beam and the supporting wall through zero-length fiber-based elements at both ends of the beam. Finally, with the development of the new analytical model and recent advancements in understanding the shear strength of RC shear walls, a new coupled/core wall design approach has been introduced to optimize the design of RC core walls. A variety of archetypes have been designed, based on both current design practices and the proposed approach. Detailed analytical models have been developed, and the efficiency of the proposed design has been evaluated through nonlinear static and dynamic analyses. To conduct the dynamic analysis, suites of ground motions were selected using the CMS approach and scaled to the MCER level of hazard. It has been demonstrated that the designed archetypes based on proposed procedure provide a more reliable shear responses under seismic loading compared to current design practices.

Download or read book Effect of Inclined Reinforcement on Seismic Response of Coupling Beams written by Jian Zhou and published by . This book was released on 2003 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: "In this research program two coupling beam specimens were constructed and tested under reversed cyclic loading. One specimen was reinforced with horizontal reinforcing bars and hoops in accordance with the design and detailing requirements for ductile beams. Another specimen was reinforced with diagonal reinforcing bars in addition to the horizontal reinforcing bars and hoops. The diagonal reinforcing bars were not locally confined by closely spaced hoops to see if there would be adequate confinement and anti-buckling resistance. Both the specimens had an identical span-to-depth ratio of 3.0. The testing results showed that the diagonally reinforced coupling beam had better performance than the conventionally reinforced coupling beam when subjected to reversed cyclic loading. It is also concluded that the use of diagonal reinforcing bars is easier to construct than the diagonal reinforcement with closely spaced hoops." --

Download or read book Seismic Behavior of Coupling Beams with Multi hook Steel Fiber Reinforced Concrete written by Mohamed Al-Tameemi and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Seismic design provisions in the ACI 318-19 Building Code for coupling beams with span-to-depth ratio ranging between 2.0 and 4.0 require to be designed either with heavily-confined diagonal reinforcement proportioned to resist the entire shear demand or as beams in Special Moment Resisting Frames. Although diagonally-reinforced coupling beams are labor-intensive and time-consuming to construct, they are the preferred reinforcement scheme selected by design engineers because of their seismic performance and higher allowable shear stress. Because of the difficulties associated with constructing diagonally-reinforced coupling beams, researchers and structural engineers paid attention to the use of steel fiber reinforcement to simplify reinforcement detailing in coupling beams. Results from research conducted in the past two decades (Setkit, 2012 and Pe̹rez-Irizarry, 2020) have indicated that it is possible to eliminate diagonal reinforcement in coupling beams with span-to-depth ratio greater than or equal to 2.0 when adding hooked steel fibers to the concrete mix. Three types of single-hook short (1.2 or 1.4 in.) steel fibers, mostly at a fiber volume content of 1.5%, were evaluated, which has imposed a significant limitation in the application of steel fiber reinforced concrete coupling beams. In this study, Twelve large-scale coupling beams were tested under displacement reversals. The coupling beams span-to-depth ratio was either 2.0, 2.25, or 3.0. Test specimens were designed to reach a peak shear stress ranging between 68́(f'c (psi) and 108́(f'c (psi). Two types of double-hook steel fibers, at fiber volume contents of 1.0% or 1.25%, were evaluated. These fibers are almost double the length and diameter of the steel fibers used in past studies. The use of larger fibers leads to a smaller number of fibers for a given fiber volume content, which facilitates concrete mixing and pouring. Further, the production cost of the double-hook steel fibers is less expensive compared to that of the short single-hook steel fibers.

Download or read book Test Data Processing of Conventionally and Diagonally Reinforced Concrete Coupling Beams Subjected to Wind and Seismic Loading Protocols written by Shahab Jaberansari and published by . This book was released on 2019 with total page 162 pages. Available in PDF, EPUB and Kindle. Book excerpt: Strong wind events are the major factor governing the structural design of many tall buildings in regions with low-to-moderate seismic hazard; however, unlike seismic design, where performance-based design of tall buildings has become common in regions impacted by strong shaking, wind design is still based on linear elastic response under ASCE 7 strength-level demands. Application of performance-based wind design, where modest nonlinear responses are allowed in ductile elements at prescribed locations, has been hampered in part by the lack of experimental data on the performance of key elements subjected to wind loading protocols. For tall concrete buildings subjected to strong wind, allowing modest nonlinearity in coupling beams is an attractive option; therefore, four 2/3-scale reinforced concrete coupling beams were tested under a simulated windstorm loading protocol, which consists of a large number of elastic load cycles and a dozen mildly-inelastic displacement cycles. The test parameters included aspect ratio, presence of floor slab, level of detailing (seismic versus standard), and loading protocol (wind versus seismic). The test results indicate that rotational ductility demands of 1.5 can be achieved with only small residual crack widths (less than 1/16 in.; 1.6 mm) and no concrete spalling or bar buckling, indicating that allowing modest inelastic responses in strong wind may be a viable approach.

Download or read book Seismic Behavior of High performance Fiber Reinforced Cementitious Composite Coupling Beams written by Bekir Afsin Canbolat and published by . This book was released on 2004 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Collapse Assessment of Reinforced Concrete Coupled Walls written by Negin Aryaee Tauberg and published by . This book was released on 2019 with total page 273 pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT OF THE DISSERTATION Collapse Assessment of Reinforced Concrete Ductile Coupled Walls by Negin Aryaee Tauberg Doctor of Philosophy in Civil Engineering University of California, Los Angeles, 2019 Professor John Wright Wallace, Chair Reinforced concrete coupled shear walls are efficient lateral load resisting systems commonly constructed as part of core walls in mid to high-rise buildings. Coupled walls are constructed as a result of openings accommodating doorways and windows, thus separating a solid wall segment in two piers. Instead of summing the strength of two individual wall piers, the efficiency of the individual wall piers is improved by proper coupling of two adjacent walls linked by coupling beams. During earthquake shaking, coupling beams act as ductile fuses and dissipate seismic energy over the building height. This coupling action reduces the flexural demand at the base of the shear walls and results in increased strength, stiffness, and lateral load resistance. Coupling beams can dissipate energy well in the system and retain significant strength and stiffness through large displacement reversals when they are detailed to retain ductility with adequate longitudinal, diagonal, and confinement reinforcement. As part of this study, important parameters affecting the behavior of coupling beams and coupled wall systems are assessed. A thorough coupling beam database is compiled consisting of 104 individual beam specimen and 11 coupled wall system level tests. The database is used to derive trends for coupling beam effective stiffness and shear-deformation backbone relations. Based on a review of past experimental results, an expression is derived relating the coupling beam effective stiffness as a function of the beam aspect ratio, i.e., EcIeff/EcIg = 0.07ln/h, which represents the secant stiffness to yield and includes the stiffening impact of the slab and the post- tensioning stress. This expression has been adopted in the PEER TBI (2017) and LATBSDC (2017) guidelines. Experimental shear-deformation information from the database is also used to quantify plastic rotations at peak coupling beam shear strength and at strength loss. The subsequent part of this study focuses on proposing appropriate seismic response parameters for coupled wall systems. Current ASCE 7-16 and ACI 318-14 design provisions specify the same seismic response parameters to be used for coupled walls as are for special structural walls. However, well-designed coupled walls can have improved lateral performance and energy dissipation compared to uncoupled walls since part of the total overturning moment is resisted by coupling action and energy dissipation is distributed along the height of structure. In coordination with ASCE 7 and ACI 318, a new lateral system is introduced for Reinforced Concrete (RC) Ductile Coupled Walls as an assembly of walls with aspect ratio (hwcs/lw) greater than 2.0 which are linked by coupling beams having aspect ratios (ln/h) between 2.0 and 5.0. This study employs the FEMA P695 methodology to validate the proposed response modification factor of R = 8, deflection amplification factor of Cd = 8, and an overstrength factor of 0 = 2.5 for RC Ductile Coupled Walls. The collapse assessment studies include forty-one Archetypes designed using ASCE 7-16 and ACI 318-19 including new provisions that require wall shear amplification and a drift capacity check. The Archetypes vary in building height (6 to 30 stories), wall cross section (planar and flanged/core), coupling beam aspect ratio (ln/h = 2.0 to 5.0), and coupling beam reinforcement arrangement (conventionally reinforced and diagonally reinforced). Collapse of the Archetypes is evaluated using failure criteria models that account for flexural failure (concrete crushing, bar buckling, wall lateral instability, bar fracture), shear, and axial failures. In comparison to previous studies that have assumed failure to occur at a roof drift ratio of 5%, this study uses a conservative approach to define flexural failure as a 20% drop in lateral strength. Overall, nonlinear static pushover and incremental dynamic analysis results indicate that R = 8 and 0 = 2.5 are appropriate parameters for RC Ductile Coupled Wall systems that are designed per ASCE 7-16 and ACI 318-19 provisions.

Download or read book Cyclic Shear Strength and Seismic Design of Reinforced Concrete Coupling Beams written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Analytical Evaluation of Diagonally reinforced Concrete Coupling Beams Under Lateral Loads written by Steven M. Barbachyn and published by . This book was released on 2011 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Use of Structural Steel Diagonal Reinforcement in Coupling Beams written by Katharine Lai and published by . This book was released on 2002 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The hysteretic responses of the two specimens showed that the specimen containing the structural steel diagonal reinforcement had a higher ductility and was able to dissipate more energy than those using headed reinforcing bars or traditional hoops. This indicates that the use of structural steel is a viable alternative for the diagonal reinforcement of coupling beams. In addition, these results also demonstrated that the use of headed reinforcing bars as confinement for diagonal reinforcement is similar to, and therefore a feasible replacement for, diagonal reinforcement confined with closely spaced hoops." --

Download or read book Nonlinear Behavior of Diagonally Reinforced Coupling Beams written by Hassan, Midhat A. and published by . This book was released on 2004 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt: