Sharif Digital Repository

The objective of this project is to study the behaviour and performance of an innotative floating offshore platform. Such Platform not only can be used for exploring oil from offshore fields, but for creating artificial islands, where land is in short supply. Due to its specific and, at the same time, simple geometry (symmetric), its fabrication does ont involve much complexity. Studies carried out on this platform include the investigation into its structural behaviour under gravitational (including self weight) and bouyancy forces. Studied cases include a number of platforms with different (geometrical) sizes and under 3 various bouyancy conditions (percentage), namely 1) 50% of the height... 

Observations made after previous earthquakes have shown the crucial role of irregularities in initiating damage in buildings with irregularity, either in Plan or in Elevation. Since in existing Building Codes, there is no provision for the distribution of the Equivalent Static Loads for such buildings, designers have no option but to resort to Dynamic Analysis. In this work, the seismic behaviour of a group of two-dimensional steel building structures with irregularity in elevation, namely Split-Level buildings, was studied. The studied structures consist of a series of 5- and 15-storey frames having two parts with splitting distance of 150 cm. Both, moment-resisting and braced frames were... 

Irregular buildings constitute a large portion of the modern urban structures. Based on experiences from past earthquakes, buildings with irregular configuration or asymmetrical distribution of structural properties trigger an increase in seismic demand, causing greater damages. Most of the building codes categorize the irregularities into two major types, ‘horizontal’ (in plan) and ‘vertical’ (in height). In this project the effects of splitting in levels, which could be classified as vertical irregularity, on the seismic behavior of some 3D steel structures are studied. The studied models consist of five-, ten- and fifteen-story 3D steel special moment-resisting frames (SMRF), each having... 

Base plates as the connecting components of steel structures to their foundations, have a crucial role in the behavior of these structures. In order to limit the thickness of base plates hence their cost within reasonable values, various types of attachments (stiffeners) are normally added to them. In this project 6 different configurations, Models, for the base plate and its attachments were considered and studied through finite element analysis. Each Model was studied under the combination of biaxial moments and a range of compressive loads including 0, 0.05 P/Py, 0.10 P/Py and 0.15 P/Py, where Py is the plastic load of the column. The moment-rotation curves of all models under various... 

Connections have a crucial role in the behavior of every structure. Amongst various types of connections used in steel structures are those used to connect the columns to the foundations, namely Base Plates. As other types of connections, base plates control the behavior of the structure in various respects including affecting the effective length of columns. The main task of any base plate is to distribute the forces of the column on the foundation in such a manner that the stresses in concrete are below their allowable values. Different configurations, with or without various attachments, are used for designing the base plates hence achieving various types of behavior with various levels... 

Due to the important role of base plates, both in transferring forces from the structure to the foundation, and also in transferring vibrations from soil to the structure, it is necessary to have sufficient knowledge on their behaviour and performance under monotonic and cyclic loading regimes. In fact, the behaviour of the supports of any structure cannot be identified without identifying the behaviour of its base plates. Numerous configurations with/without various types of attachments have been proposed and used for base plates. In this work, altogether six commonly-used types of base plates were studied and their behaviour under monotonic and cyclic loadings was obtained using commercial... 

Low tensile strength and also low strain capacity make plain concrete a ‘brittle’ material. To overcome this shortcoming, the addition of fibre as a reinforcing material has proved to be a reasonable solution. One of the crucial factors in deciding to make this type of concrete is the cost of fibre, which varies depending on its type. In this project a special type of fibre which does not cost a lot and at the same time has a high strength has been used. To investigate the effect of the fibre on the tensile strength of concrete, splitting tensile test (Brazilian test) was adopted. Altogether, 30 standard cylindrical specimens with dimensions of 15 × 30 cm2 were made (3 of each type) which... 

While there are many advantages associated with concrete, including high compressive strength, durability and so forth, on the contrary, it has several disadvantages which may make engineers somewhat reluctant to use it. These include low tensile strength, high brittleness, low resistance to impact, large dimensions of structural cross sections, etc. In recent years, there have been many attempts to surmount these disadvantages by various means such as adding pozzolans, using FRPs, fibres, etc. In this project, the effects of using a special type of high strength steel fibre is studied. In order to investigate the effect of this fibre on the compressive behavior of concrete, 30 cylindrical... 

Bracing Systems are usually a set of inclined members that are embedded in structures to resist lateral forces and control lateral displacements. There are different types and behaviors for Bracing Systems depending on the way of assembling and locating them in the structure. Braced Frames, such as Concentrically Braced Frames (CBFs), generally have high stiffness and low ductility. Another Type of Braced Frames is Eccentrically Braced Frames (EBFs) which improves CBFs by establishing suitable ductility as well as stiffness. Inelastic behavior of Links involved with EBFs caused this in EBFs. Nevertheless, these systems have no efficiency in next earthquake, because links are parts of beams... 

The behavior of a new steel shear wall, already devised by the supervisor of this project, and tested by other students, was modeled numerically. Such numerical simulation was carried out using the Finite Element Methods of analysis. Hexagonal solid elements were employed in order to discretize the tested specimens and those parts of the test assembly which had to be included in the models. Both, Monotonic and Cyclic tests were simulated numerically. Comparison of the tests results with those of the numerical models showed fair correlation between them. Percentages of error in the dissipated energy for the three monotonic tests were 6.9%, 6.4% and 11.2%, respectively, whereas that of the... 

One of the requirements of designing structures is the properties of their materials. The behavior of the material should be studied under the same conditions (loading regime) as it would be in practice. Regarding the structures which are subjected to cyclic loading, usually the results of monotonic tests on their material are used for their analysis under cyclic loads. Taking this fact into account that the behavior of materials under cyclic loading is normally much different from that under monotonic loading, one should doubt the results of the analyses of structures subjected to cyclic loading for which monotonic test results are used. In this project, the properties of steel rebars under... 

Study of former earthquakes damages reveals that irregular structures are more susceptive to failure than regular ones. Irregular structures are classified into two categories, namely those with irregularity in elevation and the ones with irregularity in plan. Besides, one of the crucial parameters in working out the earthquake’s equivalent static load is response modification coefficient (R). Based on the type of seismic lateral force-resisting system, this parameter can have various values. In this research, using nonlinear static analysis, the response modification coefficient of a great number of 3-D steel frames of 5, 7 and 9 m spans and having 1 to 10 stories with various... 

Studying the performance of irregular structures in past earthquakes reveals that due to their severe vulnerability, we need to accurately assess the behavioral characteristics of such structures. On the other hand, all existing seismic codes recommend the use of response modification factor to determine the base shear, design forces of the members, and the design drift ratios, which seem to have limited comprehensiveness. Moreover, the response modification factor for a structural system is discussed in a general manner and the effect of factors such as number of bays, number of stories, span length, story height and irregularities are not considered. In this research, the effects of... 

Response modification factor is the most crucial factor in the seismic design of structures in which the nonlinear performance of structures during strong and medium earthquakes is considered. This research tries to evaluate the response modification factors of split-level steel moment-resisting frames, which are designed in accordance with AISC 360-10. Since the response modification factor depends on ductility and overstrength, static nonlinear analysis has been performed on a number of building models and the effects of some parameters influencing it, including the height of building and number and length of spans, are studied. The over-strength, ductility and response modification... 

In this thesis, change of the behavior of frames due to adding damping devices to frames is taken into consideration and a non-linear static analysis computer program is developed . In numerical studies a few one and two story frames are used. The results of previous studies have shown that, adding energy damping devices to the structural systems, results in structure damping increase, story drift and base shear decrease. To reveal the behavior of the new bracing system, experimental and numerical studies are made. The main point in design of this bracing system, was the capability of easy replacement and maximum damping with minimum damage. It must be declared that design thought of this... 

Steel is a non-combustible material, but at high temperatures, steel structures, due to their diminishing yield strength, undergo a considerable visco-plastic deflection, which results in a reduction in their load bearing capacity. Thus, to increase safety against fire must be considered as an important objective in the design and construction of steel structures. One of the safety measures which can be taken against fire is to increase the resistance of the structure against heat by using heat-resistant coatings. This decreases the rate of transfer of heat to the structure, and must include the ‘structural members’ and ‘structural joints’. Due to the role of structural connections in... 

Recent studies show that the most efficient connections are those which have more flexibility and energy dissipation capacity in addition to their strength and stiffness. While their flexibility reduce the earthquake-induced forces, their energy dissipation capacity, by dissipating some of the energy at connections, can reduce the share of structural members of the total energy that has to be dissipated, hence increasing their chance to remain intact and undamaged during an earthquake. Since conventional connections, even semi-rigid ones, have great shear rigidity, there is not any article in the literature about shear behavior of beam-to-column connections. However, due the fact that the... 

The behaviour of a semi-rigid connection with appreciable shear deformation capacity was studied experimentally. The tests carried out on the specimens of this connection composed of ‘monotonic’ and ‘cyclic’ tests. The monotonic tests results showed the high shear deformation capacity of this connection as well as its high energy dissipation capacity. The cyclic tests, however, indicated the ability of this connection to endure large number of ‘well-rounded’ hysteresis cycles, which led to the dissipation of great amount of energy before failure  

Fire is one the events which threatens the very existence of every building, residential, office, industrial or else. However, this threat is more serious with regard to buildings with steel structures. Steel, despite its many advantages over other structural materials, such as having high strength to weight ratio, ductility, toughness and resilience, has the disadvantage of rapidly losing its strength at elevated temperatures, i.e. in fire. Therefore, it is the responsibility of the designer to make the serious decision of whether to use steel, concrete, timber, or other materials for the structure of the building to be designed. Observations made during full-scale fire tests as well as... 

Past earthquakes show that irregular structures have been more vulnerable than their regular counterparts. One of the common types of irregular buildings in urban areas is split-level ones. On the other hand, beam-to-column connections in steel structures are mostly of "semi-rigid" type. In this work, effects of different levels of rigidity of connections, 100%, 75%, 50% and 25%, on the behavior of a number of two-dimensional split-level steel structures, with 1.5 m difference in levels of floors, 2, 3, 5 and 6 bays, and 5, 10 and 15 stories, were studied. All frames were analyzed “with” and “without” considering the P-∆ phenomenon, with two methods, ‘equivalent static load,’ and ‘modal...