Sharif Digital Repository

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... 

Since mid-twentieth century the shear lag phenomenon has attracted many scientists’ attention which led to a wide range of researches to be carried out on this topic and the results are considered in the design codes. In tension members in which all parts of the member in the vicinity of the connection are not connected, only some parts of the section contribute to load distribution and non-connected parts do not play any role in load transfer and this leads to non-uniform distribution of stress and stress concentration. This phenomenon is called shear lag which causes reduction of tensile strength of the member. The effect of this phenomenon is introduced as a reduction coefficient... 

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 thesis the shear strength of pipe shear connector is investigated experimentally and numerically. The numerical analysis uses a nonlinear finite element model of the push-out specimen. The specimens consist of the pipe shear connector, steel beam, concrete slab and embedded steel rebar for concrete confinement. Eight push-out specimens are constructed with different pipe sizes and concrete strength. The results are used in a finite element parametric study to evaluate the strength of such connectors for all practical ranges of pipe size and concrete strength. It is shown that pipe connectors are more effective in transferring shear forces than angle and channel and stud connectors.... 

This research introduces two new passive control devices for protecting structures against earthquakes: Dual Pipe Damper (DPD) and In-filled Pipe Damper (IPD). The DPD device consists of two welded pipes. The IPD device is a DPD with two smaller pipes inside them and the spaces between the pipes are filled with metals such as, lead and zinc. The DPD device only utilizes plastic deformation of pipes; but the IPD device takes advantage of plastification of the outer and inner pipes, the in-filled metals, and the friction between metals as energy absorption mechanisms. Quasi-static cyclic tests are performed on four specimens of DPD and six specimens of IPD all showing stable hysteresis and... 

Lateral forces on structures are transferred to braces as tensile and compressive loads. These loads enter the beams and columns through the gusset plates. The gusset connections to the beams and columns must be such that they be able to pass the loads through themselves. So far, five analytical models have been proposed for this connection and only one of them is recommended by AISC. These models estimate the existing forces and moments on the connection. The analytical models are: model 1 (KISS), model 2 (2A-AISC), model 3 (Thornton), model 4 (Ricker) and model 5 (Richard). Among these models, only model 3 is recommended by AISC because the others are more conservative. It should be noted... 

One of the most important connections in a structure is the column base plate connection. In structures subjected to earthquake loading, this connection is usually where a plastic hinge can develop and therefore is of utmost importance. In this paper, behavior of base plates under monotonic and cyclic loading is investigated. The failure modes, that are one of the fundamental targets in this study include base plate yielding, anchor bolt yielding and also failure arising due to crushing of concrete. A parametric study is conducted using nonlinear finite element analysis. Parametes such as plate thickness, anchor bolt size and location and concrete strength are considered. The desired... 

Because of their aesthetic appeal, ease of erection, efficient utilization of structural materials, and other notable advantages, cable-stayed bridges have found wide applications all over the world in the last few decades. Bridges of this type have recently entered a new era with main spans exceeding a value of 1000 m.Like all other bridges, cable-stayed bridges are affected by different types of loadings such as dead, live, earthquake, shrinkage, creep and temperature loadings. But, because of large dimensions and high flexibility of cable-stayed bridges, earthquake and temperature loadings would be extremely affective. But design codes such as AASHTO LRFD, EURO Code neglect the... 

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 this research a novel steel connection, named “Doubly Reduced Beam Section”, and a new design procedure for “Reduced Flange Plate (RFP)“ connection are introduced and their seismic performance under cylcic loading is assessed. In order to avoid repetition of calculations, reducing human error and time consumption a computer design file in Microsoft Excel Program has been developed. Then along side the evaluation of the cyclic behavior of the connections utilizing the Finite Element Method (FEM analysis), a parametric study of the influence of various parameters on the connections seismic behavior is carried out. The results show that, following the limitations and guidelines stated in... 

Block shear failure in the parent material is considered as a common potential failure mode in welded connections used in steel structures. However, there is only little research reported on the block shear failure of welded connections under multiaxial loading. Multiaxial loading is defined as loading not parallel or perpendicular to weld lines and in the case of in planar eccentricity results in torsional loads. In this research a nonlinear finite element model is developed to study the effect of connection geometry, weld group configuration, and eccentricity of lap splice connection on block shear capacity. The case studied concerns a 3 milimeter thick structural steel plate (CSA G40.21... 

Tension-Only Concentrically Braced Frame (TOCBF) incorporates very slender bracing members, such as single angles, that are unable to dissipate much energy in compression due to their negligible buckling strength. Alternating tension yielding and elastic compression buckling of the bracing elements result in rapid strength degradation during strong motions, which translates into deteriorating pinched hysteresis loops. Based on this unfavorable behavior, it is not recommended to employ TOCBF system for medium and high-rise buildings located in active seismic areas. However, as a result of its inexpensivity and simplicity to design, the TOCBF system is used prevalently in low-rise steel... 

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... 

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... 

Nowadays seismic designs of building structures are based on a life-safety criterion that made the structures do not collapse to compromise safety of human life in the structure, but they can be designed to experience some damage. However, this design method has permitted large economic losses due to the damage to the structural and non-structural components at rather moderate levels of seismic intensities. This led to a new concept about design approach called performance-based design that satisfies the life-safety objective at the same time, reduces the economic loss to an acceptable level. In this study, the use of energy dissipating damping devices to improve the performance of a... 

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 shear lag phenomenon is one of the effective factors in determining the tensile capacity of tension members. In this phenomenon, there are various factors including the size and type of the cross-section, the type of connection, the length of connection, thickness of gusset plate, etc. are effective. The previous studies which are the basis of the specification equations, have been conducted on the cross-sections with bolted and riveted connections, while no study has been conducted to determine the effects of some of these factors yet. Using numerical methods, the present study investigates and compares each of the effective parameters on shear lag phenomenon on the single and double... 

The application of composite systems has rapidly advanced in bridge and building construction. Shear connectors are the most basic parts of the composite systems.The connectors transfer the shear forces between the slab and the beam. They also prevent separation of the slab from the beam.
Therefore researchers have done widespread studies on the behavior of shear connectors and their load carrying capacity. Steel angles are one of the shear connectors that can be used incompositesystems. Only limited number ofstudies has investigated thebehavior of thistype of connector.
The purpose of this thesis is to investigate the behavior of angle shear connectors embedded in solid concrete... 

Bridges are among the crucial elements of transportation networks and play an important role in facilitating emergency relief efforts following earthquakes. For this reasons, they should have an appropriate performance in earthquakes; Thus, presentation of true design of bridges was necessary. Elastic design of bridges due to the earthquake is uneconomic; hence, during an earthquake, the codes permitted to structures go to their inelastic behavior domain but inelastic analysis of structures are noncommercial and the capability of detail modeling of the inelastic behavior of the material is still impossible. Therefore, designers use response modification factor to consider the inelastic...