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Evaluation of Steel Coupling Beams in Low Seismic and Wind Applications /

Record Type:	Electronic resources : Monograph/item
Title/Author:	Evaluation of Steel Coupling Beams in Low Seismic and Wind Applications // Sushil Kunwar.
Author:	Kunwar, Sushil,
Description:	1 electronic resource (231 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 86-12, Section: A.
Contained By:	Dissertations Abstracts International86-12A.
Subject:	Architectural engineering. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=32142655
ISBN:	9798315779544

Evaluation of Steel Coupling Beams in Low Seismic and Wind Applications /
Kunwar, Sushil,

Evaluation of Steel Coupling Beams in Low Seismic and Wind Applications /Sushil Kunwar. - 1 electronic resource (231 pages)

Source: Dissertations Abstracts International, Volume: 86-12, Section: A.

Coupled structural walls, also known as coupled shear walls, are widely used as lateral force-resisting systems to resist seismic and wind loads for medium and high-rise structures. These systems consist of two or more structural walls connected by steel, concrete, or composite coupling beams. The coupled wall systems with steel or steel-concrete composite coupling beams are classified as Composite Shear Walls (CSW). CSWs can be further categorized into Composite Ordinary Shear Wall (COSW) or Composite Special Shear Wall (CSSW), depending on the expected level of inelastic deformation. During wind or low seismic events, the structural walls are expected to undergo limited inelastic deformations and are classified under COSW. The design and detailing of steel coupling beam-wall connection in COSW is the focus of this dissertation.In the 2010 and earlier versions of AISC 341 Seismic Provisions, the coupling beam-wall connection was designed to develop the coupling beam's expected capacity. However, in the 2016 version and recent seismic provision, AISC 341-22, this provision was replaced by the requirement that the connection be designed and detailed to develop the linear elastic shear demand of the coupling beam. This change in seismic provision leads to a shorter embedment length for the coupling beams. Although these shorter embedment lengths meet code requirements, they have the potential of adversely affecting the local and global structural responses.Analytical studies conducted at the University of Cincinnati revealed that shorter embedment lengths could accelerate the degradation of coupling beam-wall connection, reducing the level of coupling action between the wall piers. The loss of coupling action will affect the demands in the wall piers, and their capacities could be exceeded. Moreover, inter-story and overall drifts could surpass acceptable limits. To remedy these observations, AISC 341 Seismic Provisions was modified in 2022 by specifying a minimum embedment length of not less than the coupling beam's depth and requiring additional longitudinal reinforcement along the embedded region.It is important to note that the current (and previous) AISC Seismic Provisions for coupling beams in COSW and CSSW are solely based on experimental research focused on coupling beam-wall connection details intended to resist high seismic loads. Due to a lack of information regarding the performance of coupled core wall systems subjected to wind and low seismic loads, experimental and analytical studies are necessary to develop much-needed data for such loads.To evaluate the AISC Seismic Provisions 341-16 and AISC 341-22 for steel coupling beams in COSW, coordinated experimental and analytical studies were conducted. The experimental study was conducted in two phases. In the first phase, two half-scale subassemblies were constructed and tested: one represents the 9th story of a prototype from which the test specimens was selected, where elastic shear demand on the coupling beam was high, and another for the 24th story, where shear demand was low Each subassembly consisted of two coupling beam-wall connections, one designed and detailed according to AISC 341-16 and the other according to AISC 341-22. In phase 2, four three-quarter-scale coupling beam-wall subassemblies were constructed and tested, each incorporating different detailing methods. All specimens consisted of face bearing plates, with varying additional detailing for each specimen. This additional detailing method included auxiliary transfer bars, confining bars placed above and below the coupling beam flanges within the embedment region, and a longer embedment length. One of the key differences between phase 1 and phase 2 testing was the load applied: in phase 1, both the wall and coupling beam were subjected to loads, whereas in phase 2, only the coupling beam was loaded.Key findings indicate that the current AISC provisions for COSW result in inadequate embedment lengths for coupling beams, except for the cases where the embedment length to coupling beam depth ratio is less than 1. In such cases, the current equation is found to be conservative, and the use of strut-and-tie models is more appropriate for determining the connection capacity. Furthermore, the current AISC equation for calculating the effective moment of inertia for coupling beams in COSW overestimated connection stiffness by a factor of 0.70, highlighting a need for adjustments in calculating connection stiffness. Therefore, instead of a 60% reduction, a 40% reduction in gross moment of inertia, along with a correction factor for shear deformation, is recommended. The additional longitudinal reinforcement required by AISC 341-22 was found not to enhance the connection strength and stiffness. However, auxiliary transfer bars improved strength and stiffness by providing a direct load transfer path from the coupling beam to the surrounding concrete, which is not offered by longitudinal reinforcement in the embedment region around the steel coupling beam. Furthermore, the use of face bearing plates is recommended to prevent local bending and buckling of coupling beam web and flanges unless it can be demonstrated that the web and flanges can resist the local failure modes. Based on the test results, a revised equation for calculating the embedment length of coupling beams was derived. This revised equation is simpler and results in longer embedment length than the current one.A finite-element-based analytical study was conducted to understand the impact of different parameters that govern the force transfer mechanism between steel coupling beams and the surrounding concrete. A specimen from phase 2 was selected to benchmark the finite element model. The parametric study was conducted on the benchmarked model. The parameters selected for the study were the (a) embedment length, (b) longitudinal reinforcement in the embedded region, and (c) face-bearing plates. Three important conclusions were drawn from the analytical study: (1) the embedment length is the crucial parameter that governs the force transfer mechanism between coupling beam and wall; (2) additional reinforcement in the embedded region does not improve the strength and stiffness of the coupling beam-wall connection, which is consistent with the experimental observation; and (3) the inclusion of face bearing plates can be beneficial as it can help in force transfer by acting as bearing stiffener, thereby increasing connection strength and stiffness to some extent.

English

ISBN: 9798315779544Subjects--Topical Terms:

3174102
Architectural engineering.
Subjects--Index Terms:

Steel coupling beam

Evaluation of Steel Coupling Beams in Low Seismic and Wind Applications /
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520 $a Coupled structural walls, also known as coupled shear walls, are widely used as lateral force-resisting systems to resist seismic and wind loads for medium and high-rise structures. These systems consist of two or more structural walls connected by steel, concrete, or composite coupling beams. The coupled wall systems with steel or steel-concrete composite coupling beams are classified as Composite Shear Walls (CSW). CSWs can be further categorized into Composite Ordinary Shear Wall (COSW) or Composite Special Shear Wall (CSSW), depending on the expected level of inelastic deformation. During wind or low seismic events, the structural walls are expected to undergo limited inelastic deformations and are classified under COSW. The design and detailing of steel coupling beam-wall connection in COSW is the focus of this dissertation.In the 2010 and earlier versions of AISC 341 Seismic Provisions, the coupling beam-wall connection was designed to develop the coupling beam's expected capacity. However, in the 2016 version and recent seismic provision, AISC 341-22, this provision was replaced by the requirement that the connection be designed and detailed to develop the linear elastic shear demand of the coupling beam. This change in seismic provision leads to a shorter embedment length for the coupling beams. Although these shorter embedment lengths meet code requirements, they have the potential of adversely affecting the local and global structural responses.Analytical studies conducted at the University of Cincinnati revealed that shorter embedment lengths could accelerate the degradation of coupling beam-wall connection, reducing the level of coupling action between the wall piers. The loss of coupling action will affect the demands in the wall piers, and their capacities could be exceeded. Moreover, inter-story and overall drifts could surpass acceptable limits. To remedy these observations, AISC 341 Seismic Provisions was modified in 2022 by specifying a minimum embedment length of not less than the coupling beam's depth and requiring additional longitudinal reinforcement along the embedded region.It is important to note that the current (and previous) AISC Seismic Provisions for coupling beams in COSW and CSSW are solely based on experimental research focused on coupling beam-wall connection details intended to resist high seismic loads. Due to a lack of information regarding the performance of coupled core wall systems subjected to wind and low seismic loads, experimental and analytical studies are necessary to develop much-needed data for such loads.To evaluate the AISC Seismic Provisions 341-16 and AISC 341-22 for steel coupling beams in COSW, coordinated experimental and analytical studies were conducted. The experimental study was conducted in two phases. In the first phase, two half-scale subassemblies were constructed and tested: one represents the 9th story of a prototype from which the test specimens was selected, where elastic shear demand on the coupling beam was high, and another for the 24th story, where shear demand was low Each subassembly consisted of two coupling beam-wall connections, one designed and detailed according to AISC 341-16 and the other according to AISC 341-22. In phase 2, four three-quarter-scale coupling beam-wall subassemblies were constructed and tested, each incorporating different detailing methods. All specimens consisted of face bearing plates, with varying additional detailing for each specimen. This additional detailing method included auxiliary transfer bars, confining bars placed above and below the coupling beam flanges within the embedment region, and a longer embedment length. One of the key differences between phase 1 and phase 2 testing was the load applied: in phase 1, both the wall and coupling beam were subjected to loads, whereas in phase 2, only the coupling beam was loaded.Key findings indicate that the current AISC provisions for COSW result in inadequate embedment lengths for coupling beams, except for the cases where the embedment length to coupling beam depth ratio is less than 1. In such cases, the current equation is found to be conservative, and the use of strut-and-tie models is more appropriate for determining the connection capacity. Furthermore, the current AISC equation for calculating the effective moment of inertia for coupling beams in COSW overestimated connection stiffness by a factor of 0.70, highlighting a need for adjustments in calculating connection stiffness. Therefore, instead of a 60% reduction, a 40% reduction in gross moment of inertia, along with a correction factor for shear deformation, is recommended. The additional longitudinal reinforcement required by AISC 341-22 was found not to enhance the connection strength and stiffness. However, auxiliary transfer bars improved strength and stiffness by providing a direct load transfer path from the coupling beam to the surrounding concrete, which is not offered by longitudinal reinforcement in the embedment region around the steel coupling beam. Furthermore, the use of face bearing plates is recommended to prevent local bending and buckling of coupling beam web and flanges unless it can be demonstrated that the web and flanges can resist the local failure modes. Based on the test results, a revised equation for calculating the embedment length of coupling beams was derived. This revised equation is simpler and results in longer embedment length than the current one.A finite-element-based analytical study was conducted to understand the impact of different parameters that govern the force transfer mechanism between steel coupling beams and the surrounding concrete. A specimen from phase 2 was selected to benchmark the finite element model. The parametric study was conducted on the benchmarked model. The parameters selected for the study were the (a) embedment length, (b) longitudinal reinforcement in the embedded region, and (c) face-bearing plates. Three important conclusions were drawn from the analytical study: (1) the embedment length is the crucial parameter that governs the force transfer mechanism between coupling beam and wall; (2) additional reinforcement in the embedded region does not improve the strength and stiffness of the coupling beam-wall connection, which is consistent with the experimental observation; and (3) the inclusion of face bearing plates can be beneficial as it can help in force transfer by acting as bearing stiffener, thereby increasing connection strength and stiffness to some extent.
546 $a English
590 $a School code: 0045
650 4 $a Architectural engineering. $3 3174102
653 $a Steel coupling beam
653 $a Wind load
653 $a Coupling beam wall connection
653 $a Low seismic
653 $a Composite Ordinary Shear Wall
653 $a Coupled structural walls
690 $a 0543
690 $a 0454
690 $a 0462
710 2 $a University of Cincinnati. $b Engineering and Applied Science: Civil Engineering. $e degree granting institution. $3 3824213
720 1 $a Shahrooz, Bahram M. $e degree supervisor.
773 0 $t Dissertations Abstracts International $g 86-12A.
790 $a 0045
791 $a Ph.D.
792 $a 2025
856 4 0 $u https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=32142655