• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.03a
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• pp.349-361
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• 2003

For performance-base design using nonlinear static analysis, it is required to predict the inelastic behavior of structural members accurately. In the present study, nonlinear numerical analysis was performed to develop the method describing the moment-curvature relationship of structural wall with boundary confinement. Through the numerical analysis, variations of behavioral characteristics and failure mechanism with the arrangement of vertical reiforcement and the length of boundary confinement were studied. Based on the findings, moment-curvature curves and curvature capacity for walls with a variety of re-bar arrangement was developed. By equalizing curvature capacity to demand, a design method which can determine the length of boundary confinement, was developed and for the effectiveness of boundary confinement and constructability, boundary confinement detail was proposed.

• Computers and Concrete
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• v.2 no.2
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• pp.111-123
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• 2005

The ductility of reinforced concrete bearing walls subjected to high axial loading and moment can be enhanced by improving the deformability of the compression zone or by reducing the neutral axis depth. The current state-of-the-art procedure evaluating the confinement effect prompts a consideration of the spaces between the transverse and longitudinal reinforcing bars, and a provision of tie bars. At the same time, consideration must also be given to the thickness of the walls. However, such considerations indicate that the confinement effect cannot be expected with the current practice of detailing wall ends in Korea. As an alternative, a comprehensive method for dimensioning boundary elements is proposed so that the entire section of a boundary element can stay within the compression zone when the full flexural strength of the wall is developed. In this comprehensive method, the once predominant code approach for determining the compression zone has been advanced by considering the rectangular stress block parameters varying with the extreme compression fiber strain. Moreover, the size of boundary elements can also be determined in relation to the architectural requirement.

• Journal of the Korea Concrete Institute
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• v.11 no.6
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• pp.101-112
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• 1999

Structural walls have been mostly used for the design of reinforced concrete buildings in seismic areas because they play a role as an efficient bracing system and offer great potential for lateral load resistance and drift control. The lateral resistance system for the earthquake load should be designed to have enough ductility and stable hysteretic response in the critical regions where plastic deformation occurred beyond yielding. The behavior of the reinforced concrete element to experience large deformation in the critical areas by a major earthquake is affected by the performance of the confined core concrete. Thus, the confinement of concrete by suitable arrangements of transverse reinforcement results in a significant increase in both the strength and ductility of compressed concrete. This paper reports the experimental results of reinforced concrete structural walls for wall-type apartment structure under axial loads and cyclic reversal of lateral loads with different confinement of the boundary elements. The results show that confinement of the boundary element by open 'U'-bar and cross tie is effective. The shear strength capacity is not increased by the confinement but deformation capacity is improve.

• Journal of the Korea Concrete Institute
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• v.15 no.6
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• pp.877-887
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• 2003

For a performance-based design of structural walls, it is necessary to develop a rational design method for determining the length and detail of boundary confinement so as to satisfy the given ductility demand. In the present study, the curvature capacity of a structural wall with boundary confinement was estimated considering the effects of various design parameters. The curvature demand of the plastic hinge corresponding to the given design displacement was also determined. By equalizing the curvature capacity to the demand, a design method for determining the length of boundary confinement, was developed. According to the design method, the length of boundary confinement increases as axial compressive load and design displacement increase, and as concrete strength, wall thickness, amount of lateral reinforcement and aspect ratio decrease. A study was performed on details for effective lateral confinement of walls with rectangular cross-section. Based on the findings, design guidelines on spacings of ties and cross-ties were proposed.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10a
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• pp.525-528
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• 1998

This paper reports on tests of reinforced concrete shear walls for wall-type apartment structure under axial loads and the cyclic reversal of lateral loads with different confinement of the boundary elements. Confinement of the extreme element by U-stirrups and tie hooks seems to be as effective as closed stirrups. The shear strength capacity seems not to be increased by the confinement but deformation capacity improved.

• Journal of the Korea Concrete Institute
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• v.15 no.2
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• pp.323-334
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• 2003

For performance-based design using nonlinear static analysis, it is required to predict the inelastic behavior of structural members accurately. In the present study, a nonlinear numerical analysis was peformed to develop the method describing the moment-curvature relationship of structural wall with boundary confinement. Through the numerical analysis, variations of behavioral characteristics and failure mechanism with the arrangement of vertical reinforcement and the length of boundary confinement were studied. According to the analysis, the maximum moment-carrying capacity of structural walls with adequately confined boundary elements is developed at the moment the unconfined concrete reaches the ultimate compressive strain. Walls with flexural re-bars concentrated on the boundaries fails in a brittle manner. As vortical re-bars in the web increases, the brittle failure is prevented and a ductile failure occurs. Based on the findings, moment-curvature curves for walls with a variety of re-bar arrangement were developed. According to the proposed relationships, deformability of the structural walls wth boundary confinement increases as the compressive strength of the confined concrete increases compared to the applied compressive force.

• Structural Engineering and Mechanics
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• v.89 no.3
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• pp.323-334
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• 2024

Physical and chemical factors can cause traditional timber constructions to lose structural integrity. Knowing the dynamic properties of the building components is vital to avoid damage to the buildings from dynamic effects, a subset of physical effects. In this work, spruce and scotch pine wooden beams that had been strengthened in three distinct ways with carbon fiber strengthened polymer (CFRP) were investigated for changes in their dynamic properties. For this, CFRP was used to strengthening unstrengthened wooden beams in the form of bottom confinement, U-shaped confinement, and full confinement after the dynamic parameters of the beams were determined. By using experimental modal analysis with both free-free and fixed-fixed boundary conditions, the beams'initial natural frequencies were identified.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.210-215
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• 2003

Seismic capacity of reinforced concrete bearing wall subjected to high axial loading and moment can be attained by improving the deformability of compression zone or by reducing the neutral axis depth. For this two existing options for ductility enhancement were reviewed and improved to conveniently apply to the seismic improvement of compression zone of the wall: (1) end confinement of concrete due to transverse steel and (2) boundary element.

• Computers and Concrete
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• v.22 no.3
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• pp.269-278
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• 2018

In the recent decades, the application of composite materials, due to their desirable properties, has increased dramatically. In the present study, a quasi-encased trapezoidal section composite steel beam encased with concrete is thoroughly examined. Calculation of the load bearing capacity is carried out by finite element modeling of concrete and FRP beams with trapezoidal section under the effect of controlled displacement loading. The results are then validated comparing to the existing experimental results obtained from similar studies. Further on, the materials are changed to steel and concrete, and the section is de-signed in such a way that both concrete and steel reach a high percent-age of their load bearing capacity. In the last step, the parameters affecting the bending capacity and the behavior of the semi-confined composite beam are investigated. Results revealed that the beam diagonal web thickness plays the most effective role in load bearing capacity amongst other studied parameters. Furthermore, by analyzing the results on the effect of different parameters, an optimal model for primary beam section is presented, which exhibits a greater load bearing capacity compared to the initial design with the same amount of materials used for both sections.

• Earthquakes and Structures
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• v.9 no.4
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• pp.831-849
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• 2015

Seismic-design procedures for walls require that the confinement in the critical (plastic hinge) regions should extend over a length in the compression zone of the cross section at the wall base where concrete strains in the Ultimate Limit State (ULS) exceed the limit of 0.0035. In a performance-based framework, confinement is linked to required curvature ductility so that the drift demand at the performance point of the structure for the design earthquake may be met. However, performance of flexural walls in the recent earthquakes in Chile (2010) and Christchurch (2011) indicates that the actual compression strains in the critical regions of many structural walls were higher than estimated, being responsible for several of the reported failures by toe crushing. In this study, the method of estimating the confined region and magnitude of compression strain demands in slender walls are revisited. The objective is to account for a newly identified kinematic interaction between the normal strains that arise in the compression zone, and the lumped rotations that occur at the other end of the wall base due to penetration of bar tension yielding into the supporting anchorage. Design charts estimating the amount of yield penetration in terms of the resulting lumped rotation at the wall base are used to quantify the increased demands for compression strain in the critical section. The estimated strain increase may exceed by more than 30% the base value estimated from the existing design expressions, which explains the frequently reported occurrence of toe crushing even in well confined slender walls under high drift demands. Example cases are included in the presentation to illustrate the behavioral parametric trends and implications in seismic design of walls.