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Design of Rectangular Openings in Precast Walls Under Vertical Loads
Abstract
One of the successful precast concrete systems that has emerged from the PRESSS (PREcast Seismic Structural Systems) research program is the unbonded post-tensioned concrete wall system. This paper addresses the use of these walls with rectangular openings to accommodate architectural, mechanical, and safety requirements. The openings can cause large tensile stresses and, thus, cracking in the wall panels. Little information is available to aid in the design of the panel reinforcement around the openings to limit the size of these cracks. This paper describes an analytical investigation of the behavior and design of the walls under vertical post-tensioning and gravity loads. Critical regions in the wall panels where bonded mild steel reinforcement is needed are identified and a design approach is proposed to determine the required panel reinforcement. The effects of opening length, opening height, wall length, and initial stress in the concrete due to post-tensioning and gravity loads are considered. An example is included to demonstrate the proposed design approach.
... For this purpose, the opening size factor is defined by Michael G. Allen and Yahya C. Kurama. [10] The explicated above is issue of the day for the calculation of walls with openings. The tendency to reduce the weight of the buildings leads to the necessity to use high-strength concrete, which, as a rule, has a higher sensitivity to stress concentration. ...
... Design and placement of reinforcement for wall with openings, particularly, described in Design of Rectangular Openings in Precast walls Under Combined Vertical and Lateral Loads. [10] The FEA indicate that the directions of the principal stresses around opening are mostly horizontal. For symmetrical wall the stress at both right and left regions of opening are similar, but the concentration of stresses above opening differs from stresses below opening with connect to different loading and supporting condition. ...
Widely known, that stress concentration in the building elements is a major factor influencing on the design and concequency on the cost. So objective of this paper is to investigate the stress concentration phenomen in the concrete wall. For this reason we decided to study the stress concentration factor in the concrete wall, working in condition of plane stress under vertical load, distributed along above edge. In order to achieve this goal, elastic stress state of concrete walls with variety type of openings was modeled by finite element methodand analyzed by using COMSOL program.
Shear walls play crucial roles in buildings located in the seismically active regions by efficiently mitigating the impact of seismic forces. However, they have drawbacks regarding their non-recoverable deformation and, thus, lack of reusability once damaged during an earthquake. One potential solution to this problem is the use of post-tensioned (PT) shear walls. These walls rock over the base during seismic events and regain their original position after the event, showing self-centering behaviour. The self-centering behaviour makes these walls reusable and reduces the downtime of the structure, thus making them a sustainable solution over conventional shear walls. Often, they are fitted with either internal or external energy dissipators to enhance the energy dissipation capacity. The present study aims at reviewing past analytical and numerical works, design methods, and international codes on reinforced concrete (RC) PT shear walls. The study also focuses on the models used in the past to investigate the behaviour of these walls. The parameters that affect the performance of RC PT shear walls are presented. Also, the global behaviour and the system interaction of RC PT shear walls integrated into buildings have been discussed. Finally, this paper presents the summary and critical observations, along with future recommendations on RC PT shear walls.
Precast concrete facilitates a construction method using durable and rapidly erectable prefabricated members to create cost-effective and high-quality structures. In this method, the connections between the precast members as well as between the members and the foundation require special attention to ensure good seismic performance. Extensive research conducted since the 1980s has led to new precast concrete structural systems, designs, details, and techniques that are particularly suited for use in regions of high seismic hazard. This paper reviews the state of the art of these advances, including code developments and practical applications, related to four different systems: (1) moment frames; (2) structural walls; (3) floor diaphragms; and (4) bridges. It is concluded from this review that the widespread use of precast concrete in seismic regions is feasible today and that the jointed connection innovation introduced through precast research leads to improved seismic performance of building and bridge structures.
Recent research conducted as a part of the PRESSS (PREcast Seismic Structural Systems) research program has shown that unbonded post-tensioned precast concrete walls can be used as primary lateral load resisting systems in seismic regions. This paper investigates the design of rectangular openings in these walls under combined vertical loads due to gravity and post-tensioning, and lateral loads due to earthquakes. The openings can cause large tensile stresses and, thus, cracking in the wall panels. Under lateral loads, cracking can also occur as a result of the gaps that form along the horizontal joints between the wall panels and between the wall and the foundation. Little information is available to aid in the design of the panel reinforcement to limit the size of these cracks. In this paper, critical panel regions where bonded mild steel reinforcement is needed are identified, and a design approach is proposed to determine the required panel reinforcement. The effects of opening length, opening height, wall length, and initial stress in the concrete due to post-tensioning and gravity loads are considered. An example is included to demonstrate the proposed design approach.
Recent research conducted as a part of the PRESSS (PREcast Seismic Structural Systems) research program has shown that unbonded post-tensioned precast concrete walls can be used as primary lateral load resisting systems in seismic regions. This paper investigates the design of rectangular openings in these walls under combined vertical loads due to gravity and post-tensioning, and lateral loads due to earthquakes. The openings can cause large tensile stresses and, thus, cracking in the wall panels. Under lateral loads, cracking can also occur as a result of the gaps that form along the horizontal joints between the wall panels and between the wall and the foundation. Little information is available to aid in the design of the panel reinforcement to limit the size of these cracks. In this paper, critical panel regions where bonded mild steel reinforcement is needed are identified, and a design approach is proposed to determine the required panel reinforcement. The effects of opening length, opening height, wall length, and initial stress in the concrete due to post-tensioning and gravity loads are considered. An example is included to demonstrate the proposed design approach.
This paper addresses the seismic design of unbonded post-tensioned precast concrete walls with supplemental friction dampers. In recent years, a significant amount of research has been conducted on unbonded post-tensioned precast walls because of their construction simplicity and desirable seismic characteristics, such as a self-centering capability, and an ability to undergo large nonlinear lateral displacements with little damage. The greatest disadvantage of these walls in seismic regions is an increase in the lateral displacements as a result of small inelastic energy dissipation. This paper shows that these displacements can be significantly reduced by using supplemental friction dampers along vertical joints between two walls. A simplified performance-based seismic design approach is introduced to reduce the maximum displacement of the walls below an allowable target displacement. Nonlinear dynamic time-history analyses of six-, eight-, and 10-story prototype walls show that the design approach is effective in reducing the lateral displacements to prevent significant damage in the walls under maximum credible ground motions.
Unbonded post-tensioned precast concrete walls are constructed by post-tensioning precast wall panels across horizontal joints using post-tensioning steel which is not bonded to the concrete. This paper describes an analytical investigation of the seismic behavior and design of these walls. Unbonded post-tensioned precast walls with strength and initial stiffness similar to monolithic cast-in-place concrete walls can be designed to soften and undergo large nonlinear lateral drift with little damage. The nonlinear behavior is primarily due to the opening of gaps along the horizontal joints. A performance-based seismic design approach is proposed in which the walls are required to resist design level ground motions with little damage and severe survival level ground motions with damage but without failure. Shear slip along the horizontal joints is prevented by design. Nonlinear dynamic analyses show that, compared to cast-in-place walls, unbonded post-tensioned precast walls undergo larger drift, but accumulate significantly smaller residual drift during an earthquake.
A large-scale five-story precast concrete building constructed to 60 percent scale was tested under simulated seismic loading as the culmination of the 10-year PRESSS (Precast Seismic Structural Systems) research program. The building comprised four different ductile structural frame systems in one direction of response and a jointed structural wall system in the orthogonal direction. The test structure was subjected to seismic input levels equivalent to at least 50 percent higher than those required for UBC (Uniform Building Code) Seismic Zone 4. The behavior of the structure was extremely satisfactory, with only minimal damage in the shear wall direction, and no significant strength loss in the frame direction, despite being taken to drift levels up to 4.5 percent, more than 100 percent higher than the design drift level. The test validated the Displacement-Based Design (DBD) approach used to determine the required strength and confirmed the low damage and low residual drift expected of the building.
A stress‐strain model is developed for concrete subjected to uniaxial compressive loading and confined by transverse reinforcement. The concrete section may contain any general type of confining steel: either spiral or circular hoops; or rectangular hoops with or without supplementary cross ties. These cross ties can have either equal or unequal confining stresses along each of the transverse axes. A single equation is used for the stress‐strain equation. The model allows for cyclic loading and includes the effect of strain rate. The influence of various types of confinement is taken into account by defining an effective lateral confining stress, which is dependent on the configuration of the transverse and longitudinal reinforcement. An energy balance approach is used to predict the longitudinal compressive strain in the concrete corresponding to first fracture of the transverse reinforcement by equating the strain energy capacity of the transverse reinforcement to the strain energy stored in the concrete as a result of the confinement.
Thesis (M.S.)--Lehigh University, 1998. Includes bibliographical references (leaves 199-200). Includes vita. Microfilm : s
Thesis (M.S.C.E.)--University of Notre Dame, 2001. Includes bibliographical references (leaves 169-171). Thesis directed by Yahya C. Kurama for the Department of Civil Engineering and Geological Sciences. "April 2001."
Analytical Modeling and Lateral Load Behavior of Unbonded Post-Tensioned Precast Concrete Walls
- Y Kurama
- S Pessiki
- R Sause
- L Lu
- M Sheikh
Kurama, Y., Pessiki, S., Sause, R., Lu, L., and El-Sheikh, M.,
" Analytical Modeling and Lateral Load Behavior of Unbonded
Post-Tensioned Precast Concrete Walls, " Research Report No.
EQ-96-02, Department of Civil and Environmental Engineering, Lehigh University, Bethlehem, PA, November 1996, 191
pp.