• Title/Summary/Keyword: post-tensioned slab

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Numerical assessment of post-tensioned slab-edge column connection systems with and without shear cap

  • Janghorban, Farshad;Hoseini, Abdollah
    • Computers and Concrete
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    • v.22 no.1
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    • pp.71-81
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    • 2018
  • Introduction of prestressed concrete slabs based on post-tensioned (PT) method aids in constructing larger spans, more useful floor height, and reduces the total weight of the building. In the present paper, for the first time, simulation of 32 two-way PT slab-edge column connections is performed and verified by some existing experimental results which show good consistency. Finite element method is used to assess the performance of bonded and unbonded slab-column connections and the impact of different parameters on these connections. Parameters such as strand bonding conditions, presence or absence of a shear cap in the area of slab-column connection and the changes of concrete compressive strength are implied in the modeling. The results indicate that the addition of a shear cap increases the flexural capacity, further increases the shear strength and converts the failure mode of connections from shear rigidity to flexural ductility. Besides, the reduction of concrete compressive strength decreases the flexural capacity, further reduces the shear strength of connections and converts the failure mode of connections from flexural ductility to shear rigidity. Comparing the effect of high concrete compressive strengths versus the addition of a shear cap, shows that the latter increases the shear capacity more significantly.

Buckling of post-tensioned composite beams

  • Bradford, M.A.
    • Structural Engineering and Mechanics
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    • v.2 no.1
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    • pp.113-123
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    • 1994
  • A method for computing the elastic buckling prestressing force of a post-tensioned composite steel-concrete tee-beam is presented. The method is based on a virtual work formulation, and incorporates the restraint provided by the concrete slab to the buckling displacements of the steel beam. The distortional buckling solutions are shown to be given by a quadratic equation. The application of the analysis to calculation buckling strengths is given, based on codified rules for beam-columns. Conclusions are then drawn on the importance of distortional buckling when a post-tensioned composite beam is stressed during jacking.

Analysis of Post-tensioned Slab Bridge by Means of Specially Orthotropic Laminates Theory (특별직교이방성 복합적층판 이론을 응용한 포스트텐션된 슬래브 교량의 해석)

  • Han, Bong Koo;Kim, Yun Pyo
    • Journal of Korean Society of Steel Construction
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    • v.14 no.1
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    • pp.105-111
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    • 2002
  • A post-tensioned slab bridge is analyzed by the specially orthotropic laminates theory. Both the geometry and the material of the cross section of the slab are considered symmetrical with respect to the mid-surface so that the bending extension coupling stiffness, $B_{ij}=0$, and $D_{16}=D_{26}=0$. Each longitudinal and transverse steel layer is regarded as a lamina, and material constants of each lamina is calculated by the use of rule of mixture. This bridge with simple support is under uniformly distributed vertical and axial loads. In this paper, the finite difference method and the beam theory are used for analysis. The result of beam analysis is modified to obtain the solution of the plate analysis. The result of this paper can be used for post-tensioned slab bridge analysis by the engineers with undergraduate study in near future.

Behavior of Post-Tensioned Prestressed Concrete Pavement under Prestress Application (포스트텐션드 콘크리트 포장의 프리스트레스 도입 시 거동 분석)

  • Park, Hee-Beom;Kim, Seong-Min;Kim, Dong-Ho
    • Proceedings of the Korea Concrete Institute Conference
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    • 2009.05a
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    • pp.137-138
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    • 2009
  • This study was conducted to analyze the behavior of PTCP (Post-Tensioned prestressed Concrete Pavement) under tensioning by performing field tests when the experimental PTCP slab was being constructed.

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Flexural behavior of post-tensioned precast concrete girder at negative moment region

  • Choi, Seung-Ho;Heo, Inwook;Kim, Jae Hyun;Jeong, Hoseong;Lee, Jae-Yeon;Kim, Kang Su
    • Computers and Concrete
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    • v.30 no.1
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    • pp.75-83
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    • 2022
  • This study introduced a post-tensioned precast concrete system that was developed and designed to improve the performance of joints by post-tensioning. Full-scaled specimens were tested to investigate flexural performances at the negative moment region, where the test variables were the presence of slabs, tendon types, and post-tensioned lengths. A specimen with slabs exhibited significantly higher stiffness and strength values than a specimen without slabs. Thus, it would be reasonable to consider the effects of a slab on the flexural strength for an economical design. A specimen with unbonded mono-tendons had slightly lower initial stiffness and flexural strength values than a specimen with bonded multi-tendons but showed greater flexural strength than the value specified in the design codes. The post-tensioned length was found to have no significant impact on the flexural behavior of the proposed post-tensioned precast concrete system. In addition, a finite element analysis was conducted on the proposed post-tensioned precast concrete system, and the tests and analysis results were compared in detail.

Stiffness Reduction Factor for Post-Tensioned Flat Plate Slabs (포스트 텐션 플랫 플레이트 해석을 위한 강성감소계수)

  • Park, Young-Mi;Park, Jin-Ah;Han, Sang-Whan
    • Proceedings of the Korea Concrete Institute Conference
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    • 2009.05a
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    • pp.125-126
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    • 2009
  • Effective beam width model (EBWM) has been used for analysis of post-tensioned (PT) flat plate slab frames under lateral loads. For analyzing PT flat plate slab structure under lateral loads with good precision, reduction in slab stiffness has to be accurately estimated for Effective beam width model(EBWM). For this purpose, this study collected test results of PT flat plate system conducted by former researches. And this study reduced the width of slab so that the stiffness of the EBWM converged into the lateral stiffness of each test specimens by trial and error. By conducting nonlinear regression analysis, an equation for calculating stiffness reduction factor for the PT flat plate is proposed.

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Seismic Performance of Gravity-Load Designed Post-Tensioned Flat Plate Frames (중력하중으로 설계된 포스트텐션 플랫플레이트 골조의 내진성능)

  • Park, Young-Mi;Rew, Youn-Ho;Han, Sang-Whan
    • Proceedings of the Korea Concrete Institute Conference
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    • 2010.05a
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    • pp.127-128
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    • 2010
  • The purpose of this study is to evaluate the seismic performance of gravity-designed post tensioned (PT) flat plate frames with and without slab bottom reinforcement passing through the column. For the PT flat plate frames, the slab bottom reinforcement is often omitted since the requirement for the slab bottom reinforcement for PT flat plates is not clearly specified in ACI 318-08. This study evaluates the seismic performance of the model frames was evaluated by conducting nonlinear time history analysis. The seismic performance of PT flat plate frames is significantly improved by placing slab bottom reinforcement passing through the column.

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Application of shrinkage prediction models to restraint crack formation in unbonded post-tensioned slabs

  • Gabriela R. Martínez Lara;Myoungsu Shin;Yong-Hoon Byun;Goangseup Zi;Thomas H.-K. Kang
    • Computers and Concrete
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    • v.33 no.4
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    • pp.349-359
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    • 2024
  • This study aims to investigate the effect of restraint configuration on crack formation due to shrinkage-and-creep-induced volumetric change in unbonded post-tensioned slabs. The first part of this study focuses on the comparison of existing shrinkage and creep calculation models that are used to predict the volume-changing behavior of concrete. The second part of this study presents the finite element analysis of a series of architectural configuration prototypes subjected to shrinkage and creep, which comprise unbonded post-tensioned slabs with various restraint configurations. The shrinkage and creep effects were simulated in the analysis by imposing strains obtained from one selected calculation model. The results suggest that a slab up to 300 ft. (90 m) in length does not require a closure strip if it is unrestrained by perimeter walls, and that the most effective restraint crack mitigation strategy for a slab restrained by perimeter walls is a partial wall release.

The Application of Post-tensioned Slab System to Tall Buildings (초고층 건축물의 포스트텐션 슬래브 시스템 적용)

  • Chung, Kwang-Ryang
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.11a
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    • pp.879-882
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    • 2008
  • The market of Korea of post-tension system for building is growing up since 2000 and many engineers and construction companies show interest in it. This paper introduces the structure system and construction of post-tension tall buildings including recent trend in the industry of post-tension system for buildings in Korea and the point to be considered when design post-tensioned tall building. Park Polis is composed of two towers of 39 stories with a level to the top of the roof +144m and is currently under construction at Ulsan in Korea. This building designed as the unbonded post-tension floor system and will be the tallest and first high-rise post-tensioned building in Korea. The structural system is composed of the flat slabs, perimeter columns and core walls. At first, this building had designed as regular RC flat slab with perimeter beams. However, floor structure system was reconsidered because the construction company wants to improve efficiency of construction. As a result, the floor system of PARK POLIS re-designed as PT flat slab.

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Unified equivalent frame method for post-tensioned flat plate slab structures

  • Choi, Seung-Ho;Lee, Deuck Hang;Oh, Jae-Yuel;Kim, Kang Su;Lee, Jae-Yeon;Lee, Kang Seok
    • Computers and Concrete
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    • v.20 no.6
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    • pp.663-670
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    • 2017
  • The post-tensioned (PT) flat plate slab system is commonly used in practice, and this simple and fast construction method is also considered to be a very efficient method because it can provide excellent deflection and crack control performance under a service load condition and consequently can be advantageous when applying to long-span structures. However, a detailed design guideline for evaluating the lateral behavior of the PT flat plate slab system is not available in current design codes. Thus, typical design methods used for conventional reinforced concrete (RC) flat plate slab structures have inevitably been adopted in practice for the lateral load design of PT flat plate structures. In the authors' previous studies, the unified equivalent frame method (UEFM) was proposed, which considers the combined effect of gravity and lateral loads for the lateral behavior analysis of RC flat plate slab structures. The aim of this study is to extend the concept of the UEFM to the lateral analysis of PT flat plate slab structures. In addition, the stiffness reduction factors of torsional members on interior and exterior equivalent frames were newly introduced considering the effect of post-tensioning. Test results of various PT flat plate slab-column connection specimens were collected from literature, and compared to the analysis results estimated by the extended UEFM.