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... 

Airport Traffic Control Towers (ATCTs) are among the most critical structures in an airport that are expected to keep their level of serviceability after severe strong earthquakes. Therefore analysis and design of these structures need a detailed investigation on the seismic behavior of the structure based on the structural characteristics. In this study three different existing reinforced concrete ATCTs have been investigated. As important parameters of earthquake design of structures, response modification factor (R-factor) of these towers will be determined. R-factor reduces elastic force level to design force level and contains the effect of ductility, overstrength. In Iranian seismic... 

Recently in civil engineering prestressed concrete slab applications is increasing, and typically results in overall economy and provides satisfactory structural performance. In The present work, two-way prestressed concrete slabs have been considered and during designing process with the ACI-2005 code and due to economic plan, prestressed slabs were studied in transfer, service and final conditions. ACI code insists that two-way prestressed slabs shall be classified as class U (without cracking) that means section must be untracked in all conditions (code reference 18.3.3). In addition, two-way prestressed slabs must be prestressed in both directions for 100% of load, and this means that... 

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... 

In recent years, the use of fibers has found considerable attention in concrete structures as in spillways, basins of dams, shell structure, industrial floors, and bridge pedestrians. Fibers modify the brittle nature of concrete and make the composite behave ductile under various types of loading. Fibers have numerous advantages such as higher impact resistance, less shrinkage, smaller crack width, higher durability and low expense for repair and maintenance.
Till now, no adequate data has been reported on concrete beams reinforced with high volume fiber. In this study, flexural behavior of concrete beams reinforced with high volume steel fibers is experimentally investigated. Concrete... 

Tunnel form structures have been proposed in building industry during 40 years for financial saving, suitable structural performance and seismic behavior, and the possibility of performance in an industrial form; and they have also been brought up as one of the innovative technologies of construction in Iran for a couple of years. So far, these structures have been subject to study by the researchers less than frame structures. In comparison to the common structures, evaluating the behavior of these structures is analyzable as two or three-dimensional elements. In this research, the nonlinear behavior of these structures has been simulated and evaluated by using three-dimensional elements;... 

Concrete filled double-steel-plate (CFDSP) composite wall is a new lateral resisting system that recently used in design and strengthening of high-rise buildings. This CFDSP composite wall is composed of concrete filled steel tubular columns at the two boundaries and concrete filled double-steel-plate wall body. The main advantage of this system is the interaction between steel and concrete which delays local buckling of steel plates. Also, steel jacket increases the strength of concrete in result of confinement effects. Furthermore, these systems have lower thickness compared to ordinary concrete shear walls. Hence, they have less structural weight which reduces the earthquake force.... 

The aim of the present study is to investigate the effects of using hybrid fibers on rheological, mechanical and durability properties of the high-strength Self-Consolidating Concrete (SCC). For this purpose, two types of fibers including hooked-end steel fibers and polypropylene fibers were used. In this study, a total of eleven mixtures were used: one as a control mix, one containing 0.5% steel fibers, four containing 0.5% hybrid fibers (steel and polypropylene), one containing 1.0% steel fibers and the four containing 1.0% hybrid fibers (steel and polypropylene). For investigating the rheological properties, slump flow, J-ring and V-funnel tests were performed. Mechanical properties were... 

Structural elements are exposed to different types of loading which may cause excessive deformations during their life cycle. These deflections may cause damage to the structure .Therefore; reduction of dynamic response of structures can be achieved by exploiting active control system.
In this research, the dynamic behavior of prestressed Eulthemer Bernollli concrete beam under moving Load, support excitation and multi support excitation, controlled by active tendon is studied.The control algorithm employed in this thesis is closed loop linear classical optimal control with displacement-velocity feedback. R and Q matrices are chosen in order to balance the source energy consumption and... 

The experience from the performance of buildings during past earthquakes has shown that asymmetric buildings often sustain more extensive damages as compared to the symmetric buildings. The rules of seismic design codes about these buildings are based on investigation of single story buildings in the elastic range and they use rigidity eccentricity as main irregularity criterion. Inasmuch as during damaging earthquakes some lateral force resisting elements will not remain elastic and they reach yield, rigidity eccentricity will no longer be an appropriate parameter to represent the asymmetry of structure; thereby, in these building all centers of mass, rigidity, and strength should be paid... 

Even though a considerable amount of research has been conducted on composite wall system during past years, very limited research has been reported on shear walls strengthened by steel plates. In 2008, the composite shear wall, which consisted of reinforced concrete wall, retrofitted by steel plates, attached to both sides of RC walls using mechanical connectors in form of shear studs, bolts or lateral ties tested under axial load and lateral force. In this research, seismic behavior of RC shear walls strengthened by vertical strips of steel plates is going to be studied. The result will be compared with RC shear wall which fully covered by steel plates. The behavior of RC shear wall will... 

In this paper, the response of low-rise shear walls with smart rebars under static lateral loading has been numerically studied, using Finite Element Method. The material used in this study is Shape Memory Alloys (SMAs) which contains nickel and titanium elements. During lateral loading, rebars yield or concrete crushes in compression zone in some parts of the RC shear walls and also residual deflections are created in the structure. The SMA exhibits little residual strains under cycles of loading and unloading even after passing the yielding zone. In addition, SMAs have a good energy dissipation capacity that helps reduce damage while increasing structural capacity. In this study, SMA... 

Although the issue of separation is studied frequently in the last few decades, in presence of numerous parameters and unknown effects of earthquakes and soil condition, scientists confront with remarkable difficulties. It was supposed that performance of structures which are secluded from soil remains in the elastic region and doesn’t bear nonlinearity. But according to recent studies, scientist assert that nonlinear performance might be possible as a result of various soil condition and ingredients of earthquake(magnitude and frequency). General procedure for seismic improvements of structures includes increasing the strength and resistance, capability of structure to absorb energy and... 

There is a requirement for strengthening of steel structures due to undesirable design, wrong implementation, bad maintenance and changes in design codes. Many studies have been done on strengthening of concrete specimens but there is a need for reinforcement of steel specimens yet. In the present paper, results of an experimental study on strengthening and reinforcing of steel beams under mechanical loads have been presented. Totally, Sixteen steel specimens with span’s lengths of 0.2, 0.5 and 1 meter were reinforced by carbon laminates and subjected to -point bending load. Three failure modes of shear yielding, flexural yielding and lateral_torsional buckling in the beams were examined.... 

The purpose of this research is evaluating of how the concrete filled composite tube column performs. Nowadays in the construction industry, a new kind of composite column called concrete filled composite tube (CFCT) columns, have become very common. Concrete and composite tubes posses’ complementary performance. Because on one hand, the composite tube makes proper confinement for concrete, on the other hand the concrete prevents internal and local buckling of the composite tube. One of the major advantages of the concrete filled composite tube columns compare to the reinforced concrete column is that there is no further need for reinforcement and molding, which results in swifter... 

Increasing the population of cities has led to the more construction of high-rise buildings. In design of high-rise buildings, stability of structure plays a significant role in its final design.According to the fourth edition of 2800 standard (The Iranian code of practice for seismic resistant design of buildings), for buildings with height of more than 50 meters, only using dual system and special moment resisting frame system is allowed, whose stability condition will increase the final cost of the structure. Systems such as outrigger system have been created to overcome this weakness. Outrigger is a rigid, horizontal system that is perpendicular to the shear core and connects the shear... 

The increased height of high-rise structures has made the effects of reduced stability a crucial factor in structural analysis and design. There are a variety of methods for analyzing the stability of high-rise structures. This thesis discusses nonlinear finite element method for analyzing the stability of a three-dimensional 50-storey concrete structure with a height of 150 meter using increment dynamic analysis (IDA). The IDA was first proposed by Bertero.v and it has been adopted in a variety of manners by researchers. In recent years, this method has been confirmed by EEMA. Moreover, FEMA350, FEMA351 and FEMA P695 guidelines have paid special attention to this method for determining... 

In the last decades, noticeable experimental and analytical investigations have been carried out on cast-in-place Reinforced Concrete column to Steel beam (RCS) connections, however rarely have been conducted on the precast RCS. In this reaserch, test results of five half-scale interior precast RCS connections with variable joint configurations are presented. The steel beams were connected to the precast column, using face bearing plates, embedded in the connection zone. The flanges of beams were strengthened with respect to scaled section, in order to increase the load transfer to the joint. All samples were loaded under reversed displacement controlled condition. The failure mode, joint... 

In this study, the flexural behavior of simple concrete beams with rectangular section (depth 20cm and width 18 cm) reinforced with perforated steel plates is evaluated. Perforated steel plates are used as an alternative for steel bars in the tension region. Because of special geometry, these plates are more integrated with surrounding concrete as compared with steel rebars. The holes in the plates caused local confinement on the surrounding concrete. Concrete beams are modeled with different number of perforated steel plates (one or two or four layer) in Abaqus software. Also beams with different patch lengths are modeled to evaluate patch length of perforated steel plates. Results of... 

In recent years, more attention has been paid to the development of lightweight concrete (LWC). Study of such this material had been marked due to more importance of use of it.It is now well known that in order to model cracks the finite element model is more suitable.The fracture of quasi-brittle material such as concreteincludesthe fracture process zone (FPZ).Cohesive zone model is considered the most common model used for FPZ modeling.Therefore, in this article the propagation of cohesive cracks inLWC is modeled using the extended finite element method (XFEM). In this study, modeling showed fastgrowth and propagation of cracks inLWC. Due to its cavities and pores, LWC shows to be more...