Sharif Digital Repository

Jacket type offshore platforms are classified as expensive and also strategic structures, and the cost of their maintanace is considerable. Therefore, any inspection and retrofit plans for life extension of the existing structures is economically and logically preferable rather than making decision for design and construction of new structures. The first stage of assessment plan is monitoring the performance of structure during critical loadings for which the structure is designed. One of the critical loads that should be considered in assessment of jacket structures is seismic loading. Due to dynamic nature of the applied loads in seismic assessment of jacket structures the accuracy of... 

Lateral spreading due to liquefaction and resulting destruction of buildings is important in Iran because of high seismicity and important infrastructure near south and north coasts of Iran. Lateral spreading is vast lateral movement of sloping ground or level ground ending in an opening like river which is caused by earthquake inducedliquefaction. For considering the effects of lateral spreading during design of deep foundations of structures in a susceptible area, one needs to determine the lateral loads on piles under lateral spreading. Present study investigates the behavior of a 3x3 pile group against lateral loads due to lateral spreading with numerical methods using OpenSees software.... 

This study focuses on the risk assessment of reinforced concrete tall buildings subjected to ground motion excitation. In order to assess the vulnerability of tall buildings, twelve-, and twenty-four-story four-bay reinforced concrete moment resisting frames are studied. This evaluation is done through developing fragility curves. These fragility curves provide the probability of exceeding the multiple damage states for a given intensity (e.g. CAV) of ground motion excitation. To develop the fragility curves, a great number of nonlinear dynamic analyses were conducted in the open-source platform OpenSees. Since the PEER Guidelines for Performance-Based Seismic Design of tall buildings (PEER,... 

Beam to column connections affect on the performance of the steel frames. Connections are assumed pin, semi rigid or rigid based on rigidity. Previously most steel structures designed as pin or rigid connections but lately many studies have been done on structures with semi rigid connections and these studies show that semi rigid connections have excellent properties that makes this connection a superior response such as less base shear, more economic, ability to absorb more energy and etc. In this study semi rigid connection with torsional plate has been studied. In addition to previous characteristics, this connection has special properties such as simple implementation, Dimension... 

Reinforced concrete buildings with open ground storey are vulnerable to accumulate of large lateral displacement at the ground story. This is due to drastic reduction in the relative stiffness of the ground story compared to the upper stories, a phenomenon known as soft storey effect. Furthermore inevitable Existence of Opening in masonry infill and increasing it’s area reduces both the lateral strength and stiffness of the fully infilled RC frames so when percentage of the central opening is very high, the behaviour of the infilled frame approaches the bare frame. It is a perception about open ground storey buildings that openings in the upper stories infilled frame offset the soft storey... 

In recent earthquakes piles have been severely damaged due to liquefaction-induced lateral spreading. Liquefaction causes lateral spreading in gently sloped saturated soft granular soils, leading to significant damage in structures and deep foundations. Although in recent years many studies have focused on different aspects of this phenomenon, the complex nature of the dynamic interaction between piles and liquefied soil is not yet fully understood. This potential damages are of high degree of importance in southern and northern coastal areas of Iran where several ports and critical facilities are located. The present study focuses on the behavior of a 2x2 pile group against lateral loads... 

A numerical framework is proposed to estimate the liquefaction-induced settlement of the fully saturated sandy layers in the free fields due to earthquake excitation and the results of the proposed method are compared with those of the empirical or probabilistic methods suggested by the previous researchers. Liquefaction is a sudden transformation of saturated sandy soil into a viscous fluid which is caused by the increase in the pore pressure and decrease in the effective stress and results in the reduction of the shear strength of the soil. One of the most important consequences of liquefaction is the liquefaction induced settlement which has caused severe damages in many places in the... 

The purpose of this thesis is the optimal retrofitting of the moment resisting frames with friction dampers, using the adaptive approach. In this regard, numerical modeling of the frictional behavior has been presented firstly. Also a 6-story moment resisting frame has been modeled in the OpenSees environment and the time history analysis has been carried out under a specific earthquake record. It is shown that inter-story drifts of the frame exceeds the acceptance criteria which has been assumed 2.5% according to the Life Safety limit. Then, the optimal retrofitting of the frame has been done. It is demonstrated that the maximum inter-story drift of all stories is 2.5% or less, while the... 

The purpose of this study was to find the optimal position and slip force of friction dampers, for improving the seismic performance of regular and irregular steel structures and comparison of dampers final pattern of these buildings.In this regard, one to six floor regular and irregular buildings were designed. These buildings were modeled three-dimensionally in the OpenSees Software, and were subjected to horizontal components of seven far field accelerogram in order to investigate the need for their rehabilitation. The results of the time history analysis of these buildings showed that inter-story drifts exceeds the acceptance criteria which has been assumed 2.5% according to the Life... 

Base-isolated structures are known for their effectiveness in performance improved of structures subjected to earthquake excitations. The limitations on the base displacements of these isolations systems, however, limit the amount of performance improvement that can be practically obtained. In fact, this is among the most important design parameters of base isolation systems. In this study, tuned liquid dampers have been employed to reduce the displacement demands at the isolated bases of structures, while maintaining performance.
For this purpose, structural models including three-, six-, and nine-story buildings are considered. Furthermore, “Housner Model” is employed in order to... 

Despite all the developments of construction industry, there are some limitations in this important industry. For example, one of the common limitations of buildings is restrictions of architectural designs that often rise due to location of lateral load-resisting systems of buildings and usually rise disagreement between structure and architecture engineers. The lateral load-resisting systems and location of them are very important, therefore, in this study we attempt to investigate the changes of their location in structure’s stories. Due to architectural restrictions, the removal and movement of lateral load-resisting systems have been done only in some stories or from a story to the... 

For the preliminary design of isolated structures, it is necessary to select the appropriate damping ratios in each mode. The inherent modal damping in this type of structures is small. On the contrary, a significant value of damping is induced by dampers in isolator system into structural modes. The purpose of this study is to determine the Modal damping ratios in isolated structures. In this regard, shear structures of 2 to 10 floors with linear behavior in both superstructure and isolation level have been analyzed. The Structures have been modeled taking advantage of OpenSees. Samples are analyzed under sinusoidal loading applied to each floor. In order to achieve modal damping, an... 

Based on special properties of metal dampers such as high energy dissipation, stable hysteric cycles and simple application, low cost, insensitivity to changes of temperature and ability to be substituted after occurring of earthquakes, they are being used for structures control. ADAS and SSD are two kinds of metal dampers which are connected to top of the chevron braces and under the middle of beams. When shear forces are applied, these dampers yield and enter the plastic zone. In Endurance Time (ET) method gradually intensifying acceleration functions are created in a manner that the linear and nonlinear response spectra of them, while being proportional to average of real earthquakes... 

In seismic regions, the construction of structures with appropriate seismic performance and re-centering capability that can reduce residual displacement and damage, are necessary. As an alternative, prestressed columns were developed in recent years which can limit the permanent deformation and structural damage effectively. After severe damage and residual displacement of bridge piers and building’s columns, extensive research was carried out on prestressed columns. Most researches have been conducted on the prestressing of bridge piers and precast columns in self-centering system but prestressed columns in common moment resisting frame and comparing their advantages and disadvantages with... 

Shape memory alloys (SMA) are materials with shape memory effect and high recentering capacity. Recently, application of SMAs in building structures and for the purpose of structure control during earthquake has been considered by many researchers. Researchers have tried to reduce the residual displacement of the structure after earthquake and also increase the dissipated energy by using this material in different forms such as wire, spring, bolt, etc.. In this research the seismic performance of steel structures equipped with SMA connection has been studied, considering the soil and structure interaction. The purpose of this research is to investigate the amount of required SMA bolts in... 

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... 

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... 

Ordinary structures absorb a large amount of input energy by structural elements whereas failure in these elements causes a huge loss in structure and it’s really difficult to repair or unrepairable. Nowadays a wide range of metallic dampers is used in structures as fuse elements. this research evaluates the response of structures that are equipped with a novel steel damper named Telescopic Lead Yield Damper (TLYD) which was introduced by Eskandari in 2018. As TLYD has a different yielding plateau it can tolerate large deformations. In this research firstly this novel damper was introduced and the performance of the damper under cyclic loading was demonstrated. Then a numerical model of 6,... 

In this paper the predictive equations for collapse assessment of shear links used in eccentric braced frames are developed. An extensive database including results of over 70 cyclic tests on steel wide flange shear links is collected and the structural parameters governing the hysteresis behavior are calibrated using a simplified numerical model. The methodology of calibration is to minimize the discrepancy between the experimental hysteresis loops and the corresponding numerical results using Particle Swarm Optimization (PSO) algorithm. The objective function of PSO algorithm is minimized by iterating parameters that govern the hysteresis behavior of the numerical model. Stepwise... 

The purpose of this thesis is the optimal retrofitting of the moment resisting frames with telescopic dampers, using the adaptive approach. In this regard, numerical modeling of the telescopic behavior has been presented firstly. Also, a 3,9,20 story (sac) moment resisting frame has been modeled in the OpenSees environment and the time history analysis has been carried out under a specific earthquake record. It is shown that inter-story drifts of the frame exceed the acceptance criteria which has been assumed 2.5% according to the Life Safety limit. Then, the optimal retrofitting of the frame has been done. It is demonstrated that the maximum inter-story drift of all stories is 2.5% or less,...