Sharif Digital Repository

Post-tensioning is the most versatile form of prestressing, a technique which enables engineers to make the most effective use of the material properties of concrete, and so to design structural elements which are strong, slender, and efficient. Design of post-tensioned concrete structures is not difficult and, if done properly can contribute significantly to the economy and the aesthetic qualities of a structure. Post-tensioned building floors and bridge girders have found widespread use in office buildings, parking structures and bridges. They are also frequently employed in warehouses and public buildings. Now a days bridges and other type of structures, in many countries are designed... 

Due to the growth of population and the increasing number of auto-manufacturing plants in the world, governments have to find ways to decrease traffic, environmental pollution, etc. Providing parking lots is another problem with which we have to deal. It seems that designing and building multi-storey reinforced concrete parking structures is one of the ways to resolve this problem. According to complex behavior of concrete in compression and tension, it was so important to use an appropriate behavior model. In this research damage concept is used instead of crack concept which could models concrete behavior appropriately which causes acceptable results. According to uni-axial, bi-axial and... 

The use of unbonded post-tensioned precast concrete walls with horizontal joints as the primary lateral load resisting system in seismic zones has been considered in several previous studies. These walls are constructed by post-tensioning precast wall panels across horizontal joints using post-tensioning steel which is not bonded to the concrete. The behavior of the unbounded post-tensioned precast structural wall under lateral loads strongly depends on base panel geometry and concrete confinement properties. In this research an analytical parametric investigation on base panel design parameters is conducted using DRAIN-2DX software. Fiber beam-column elements are used to represent the... 

This study evaluated post-tensioned system’s behavior in the steel structure. The post-tensioned system includes post-tensioned frame and gravity system (gravity frame and floor diaphragm) and considers the interaction of post-tensioned frame with gravity frame. Post-tensioned frame is the moment frame that has post-tensioned connections instead of ordinary connections. Bolted top and seat angles are used in the connection, along with post-tensioned high strength strands that run parallel to the beam. The strands compress the beam flanges against the column flange to develop a resisting moment and the friction between the beam and column and the two angles resist shear. Studies showed that... 

The purpose of this thesis is assessment of seismic performance of self-centering concentric braced frames (SC-CBF). In this structures, the column under tension can uplift from the foundation at a specified level of lateral loading and by using some methods such as post-tensioning (PT) bars or tendons, the structure is able to self-center after severe Earthquakes. In this systems, PT bars and energy dissipation elements resist column uplift. The effect of energy dissipation ratio and initial stress in PT bars was investigated in design and performance of four four-story analytical models. Nonlinear static and dynamic analyses were conducted to compare some parameters in these four models... 

Shear wall systems are one of the most commonly used lateral load resistant systems in structures. Duo to preventing immoderate residual displacements after strong earthquakes in these structures and its enormous repairment costs, a novel lateral force resistant system were proposed. In this research self-centered post-tensioned shearwalls known as hybrid shearwalls with post-tensioned tendons and energy dissipator mild rebars were used in concrete structures and seismic behaviour of these structures were studied. In this new system tendons provided essential restoring force in shearwalls and structures to bring them back to theirs vertical shape. Also energy dissipators squandered... 

Although the moment frame can show deformable behavior against seismic loads, but its flexibility and low stiffness, especially in tall structures, cause the governance criterion to be designed. The use of eccentrically braced frames was able to solve the displacement problem to some extent, because it has the characteristics of both flexural frame systems and conccentric bracing. Different methods have been proposed to eliminate residual displacements in this type of system, one of which is the use of post tensioned cables. The aim of this study was to investigate the seismic behavior of a steel structure with a eccentrically braced frame system with post tension cable.The cables are anchor... 

Tests have shown that concrete post-tensioned slab under heat condition suffer a significant reduction in stiffness and strength. Design and implementation of post-tensioned concrete slabs with large spans of industrial structures exposed to extreme variation in temperature can be possible with detailed research on its behavior under heating condition. In this study numerical modelling of PT concrete slabs with unbonded tendons under heating condition was created based on available test results in the literature. A parametric study has been carried out and the results are presented for concrete coefficient thermal expansion, thermal contact conductance between the concrete and the cables,... 

Conventional eccentric braced frames often sustain large residual deformations and significant damages after strong earthquakes which may lead to heavy damages or even destruction of the structure. Here, a self-centering, Y-inverted, eccentrically braced frame (SC-YEBF) is proposed which combines the lateral load resisting benefits of YEBF including strength, stiffness and energy dissipation capacity with the re-centering capacity of post-tensioned (PT) high strength steel strands used at beam-to-column connections. A design procedure is presented assuming that all the seismic input energy is dissipated through inherent damping and plastic deformations of the link-beams. Thus, in the... 

This research describes a numerical investigation on a lateral load resisting system comprising of a pin-supported rocking concrete wall coupled with steel moment resisting frames (MRF) models with different support conditions. Two 4 and 8-story structural models are considered for case study analyses with hinged, half-clamped, and clamped support conditions. Fluid viscous dampers (FVDs) are added to the combined system to provide supplemental energy dissipation under the rocking action of the wall. This study aims to compare the efficiency of the proposed system on shear force distribution, residual drift reduction, decreasing the absolute accelerations, as well as comparison of the support...