Sharif Digital Repository

The strength of welded joints is determined by the lower value of the weld metal and base metal strength. In welded bracing connections, the latter includes the connecting element (i.e., the gusset plate) and the bracing member. According to the American steel design standard AISC 360, the base metal strength is determined based on the limit states of tensile rupture, shear yielding, shear rupture, and block shear. While extensive research has been conducted on the limit state of tensile rupture, limited attention has been given to the limit states of shear yielding, shear rupture, and block shear in welded bracing connections. Furthermore, the design strength equations adopted by AISC 360... 

Choosing and designing a suitable lateral force resisting system in areas with high seismicity has always been one of the main challenges of structural engineers. Therefore, many systems have been developed and implemented over the past decades. Among them, we can mention reinforced concrete and steel moment frames, concrete and steel shear walls, bracing systems and even their combination under the title of dual systems. The choice of each of the above depends on many factors such as the importance of the building, the seismicity of the region, height of the building, architectural restrictions and also cost. Although the evidence of past earthquakes shows that, for a well-designed... 

Recently, corrugated steel plate shear walls (CSPSWs) have been shown to be an efficient lateral force resisting system for building structures. Corrugated plates have higher out-of-plane stiffness and improved buckling stability in comparison with flat plates which result in improved hysteretic behavior. The application of CSPSWs in tall buildings requires a wide range of thicknesses for the infill plates. Yet, the available range of thicknesses of corrugated plates is limited because of the restrictions associated with the process of cold forming. One solution to this problem is to use two corrugated plates as an infill plate. In this research, the cyclic performance of double corrugated... 

It is very common to use moment frame system in earthquake-prone areas in the two main directions of buildings. This system is very popular among architects due to the creation of unobstructed openings between the columns and the possibility of using openings in them.The column is one of the main components in the design of orthogonal moment frame systems and plays an important role in the performance of this system. The columns that are in the two main directions of the intersection of two moment frame systems, due to the existence of the 30-100 rule in seismic design regulations, must be able to withstand 100% of the design earthquake force in one direction and 30% of the same force in the... 

The purpose of the current study is to investigate the base metal capacity of stiffened seated angle connections and to inspect their behaviour. The effect of different parameters on the capacity of connections is examined, considering the damage in the column. This research is important since for welding design, codes require the designer to control the base metal capacity to check the connection capacity, while the method of calculating this capacity is not provided, and this issue is not considered in the design. In this research, ABAQUS finite element software was used to model and analyze the results. A total of 90 stiffened seated angle connections, which were connected to the flange... 

In this study, several novel cable-pipe damper brace (CPDB) systems are introduced. The CPDBs consist of steel cables wrapped around supporting pipes and arranged as cross-bracing in steel frames. The arrangements are such that the cables are always in tension when a lateral load is applied to the steel frames. The wrapping of cables around pipes makes the systems act like a friction damper in a seismic event. In addition, the possibility of energy dissipation by plastic pipe deformation and yielding of cables is investigated. Each system is analyzed by nonlinear finite element method to investigate its lateral strength and cyclic behavior. The primary results of this study showed that some... 

Nowadays, using perimeter steel moment frames in combination with interior gravity frames have become common practice in structural building design. One of the key benefits of this system is the open space that it provides for the architects. In active seismic regions, special details are required in the design of the seismic force resisting systems to make these frames ductile. However, these details cause excessive displacement for the gravity force resisting system. Although the gravity frames are not designed to endure seismic forces, they collaborate in the system’s response as they are connected to the same floor diaphragm and withstand lateral displacements. Therefore, these systems... 

In the seismic design of steel special moment frames, it is necessary to ensure that columns are generally stronger than beams. This reduces the probability of a weak story failure mechanism of the frame, and ensures the formation of beams' plastic hinges earlier than the columns’. This criterion is known as strong column-weak beam (SCWB) in seismic design codes and is checked by a formula in the form of a ratio of total flexural strengths of columns to beams framing at each joint. It is common practice to ignore the column’s section change at the splice location and to use the flexural strength of the column’s larger section in evaluating this ratio. In this paper, several 20-story steel... 

Nowadays, many structural engineers use fillet welds in their designs because of their high strength and affordability. In these welds, eccentric loadings either out-of-plane or in-plane create complex condition in welds from stress point of view. To determine the capacity of such fillet welds different methods have been proposed over time. For instance, the method approved by AISC is the Elastic method. This method when combined with load factors, as required by the LRFD design method, yields very conservative designs for fillet welds. Therefore, in this project, we try to propose the plastic method for welds under eccentric loadings. This method is more economical than the elastic method... 

Performance-based design (PBD) has been accepted as one of the most reliable design methods in the past few decades. PBD can overcome inherent deficiencies associated with force-based design (FBD) and has advantages over this traditional method. Various PBD methods have been developed, which Displacement-based design (DBD) has been considered as one of the effective design approaches of the PBD method. In this study, the Displacement coefficient method (DCM) is developed for stub-type integral abutment bridges (IABs). For this purpose, two coefficients are proposed to determine the target displacement of these types of bridges. Validation of this method by nonlinear time-history analysis... 

The purpose of this research is to evaluate skew integral abutment bridges. A bridge with an integral abutment bridge system is a type of bridge in which the expansion joint is removed so the connection between the abutment and the superstructure is rigid. Therefore, the superstructure and the substructure are integrated with each other and both participate in the lateral load of the structure under seismic or thermal forces. One of the important challenges in this type of bridges is the lack of analysis, tests and limited three-dimensional modeling. According to this, the understanding of the behavior of skew integral abutment bridges and the effects of soil-structure interaction in these... 

In recent years, steel tub girder superstructures have been exceedingly used in long span superstructures due to their significant torsional and flexural stiffnesses. In such superstructures, end diaphragms made of plates are one of the most important members in transferring seismic forces to the substructure. Despite the importance of end diaphragms, limited number of studies have been conducted on their behaviour and as a result, their design procedure is not clear. In this dissertation, different configurations of end diaphragms in elastic steel tub girder superstructures were evaluated using finite element models and the required equations for stiffness and strength were derived.... 

Steel cylindrical silos are one of the most practical structures in handling and storage of bulk solids in many industries and agricultural sectors. Steel silos may be composed of flat or corrugated sheets. Due to small wall thickness, shell structures are vulnerable to buckling failure. Unsymmetrical loading conditions rising from frequent filling and discharge cycles during the lifetime of these storages are almost the main reason for local or global instability of silos. However, they may experience additional lateral loads such as, wind load and seismic load that essentially impose unsymmetrical pressure on shell walls and can lead to buckling, as well. Under wind pressure, steel... 

In order to design buildings such as industrial structures, which use multi-tiered braced frames as their lateral load resisting system, it is required to know seismic performance factors, including the response modification coefficient (R), the overstrength factor (Ω0), and deflection amplification factor (Cd). The main purpose of this study is to assume initial seismic performance factors and evaluate their accuracy based on Fema-P695 methodology. This methodology provides a reliable basis for determining seismic performance factors of different lateral load resisting systems. In this study 8 archetypes have been chosen and designed with initial factors of 6, 2 and 5 as R, Ω0 and Cd,... 

Live load distribution factors for bridge superstructures on which live load is first transmitted through concrete slabs to transverse beams and then through transverse beams to longitudinal beams (three-element superstructure), is expressed in the AASHTO LRFD, only as a function of the distance between the beams; however, in slab-beam superstructures (two-element superstructure), the live load distribution factors depend on many parameters, including slab thickness, clear span, longitudinal beam stiffness as well as the distance between longitudinal beams. This study investigates the factors affecting live load distribution factor and the relationships among these factors in three-element... 

This study examines the safety and economics concerns in seismic design of column splices in steel concentrically braced frames. The importance of column splices in steel frames is that in structures with high columns, due to the limited length of existing profiles or economic issues, we have to use column splices. Error in the design and implementation of the column splice can affect the stability and overall performance of the structure. In this regard, the Seismic Provisions for Structural Steel Buildings has provided rules for designing column splices in the braced frame. The purpose of this research is to evaluate the criteria presented in the regulation and obtain seismic demand and... 

Fillet welds are widely used in steel construction due to their high strength and economy. In the joints used in construction, eccentricity loads in complex weld stress. The current research involves 72 bending specimens and 16 torsion specimens being modeled to study different design code relationships regarding the plastic properties of welds. In line with an even comprehensive study, the previous experimental programs in this field have been added to the modeling results.Reliability analysis has been applied to examine code relationships more precisely. The analysis involved examination of various uncertainties which showed that applying elastic methods proves more conservative than other... 

Purpose of this research is evaluation of response modification factor for integral abutment bridges in longitudinal direction in which substructure and superstructure both act as a unit system in resisting of lateral loads and no expansion joints are used in them. One of the most important challenges in design of IABs, is lack of response modification factor for their seismic design in longitudinal direction. Another challenge in these bridges, is modeling of soil-bridge structure interaction that affects not only abutment and piles’ seismic performance, but deck performance too. The other challenge is lack of adequate knowledge about their behavior and seismic performance which is of great... 

Regarding available structural codes, for designing of buildings with dual lateral force resisting system which includes special moment frames and ordinary concentrically braced frames, we need to determine seismic performance factors. Seismic performance factors embraces of response modification (R), over strength (Ω0) and displacement amplification (Cd) factors. The goal of this research is to evaluate aforementioned factors using the method presented with FEMA P-695. This method represents a reliable framework to assess the seismic performance factors of various kinds of lateral force resisting systems. In this approach, first, archetypes are designed with assuming certain values for... 

This research is studying seismic behavior of bridges with spill-through abutments. There is a lot of studies in the literature about the behavior of piers and different types of them in the field of seismic assessment of bridges. But seismic behavior of abutments has paid less attention. In addition, most researches in this field are about common types of abutments like wall-type or integral abutments and also there are few standards and design guidelines about spill-through abutments.However spill-through abutments had been used by designers, especially they are common in Iran.In this research, a bridge with a spill-through abutment is designed as a benchmark. The benchmark bridge is...