Sharif Digital Repository

The AASHTO Standard Specification defines diaphragms as a transverse member between girders in order to maintain sectional geometry. Some of the reasons in favor of using a diaphragm are that it prevents the girders from twisting during the process of construction and helps in distributing vertical live loads between girders and transfers lateral loads (wind or earthquake) to supports. It also provides restraint for the lateral-torsional buckling of the girders. While diaphragms at the ends of bridges are called end diaphragms, the diaphragms away from the bridge ends are called intermediate diaphragms. These members are usually made of steel or cast-in-place concrete. Based on their... 

Numerous research is available in the literature regarding shear walls. These have considered parameters like wall cross-section, Reinforcement configuration, boundary elements, etc. In addition, seismic and wind loading behavior has been discussed. Currently, the software ETABS is used extensively in automatic design of shear walls, The programs design bases are investigated in this thesis in ragards to flexural, shear and boundary elements of shear walls under seismic loading. The attachment of wall elements to frame (column) elements is of particular interest in this study  

Tension members are widely used in steel construction, in trusses or in the braces etc. To design a tensile member with connection to the gusset plate a phenomenon called shear lag must be considered. Shear lag effect is introduced as a coefficient in the design codes. AISC code has proposed formulas to calculate the shear lag coefficient of different sec-tions but there is no equation for the double channel section. By considering double chan-nel as a two-separate-single-channel section the design would be very conservative. In this thesis, shear lag coefficient is parametrically investigated by numerical simulation of the double channel section. Different parameters like weld length, out... 

The steel-concrete composite beams are increasingly used in bridge and building construction in recent years. A shear connection between the steel and concrete should be provided to effectively transfer the shear force and to make the two materials act as a single unit. The mechanical shear connectors provide this means. They are the essential component of any composite beam system. Many studies have been performed on shear connectors and many different steel shapes have been suggested for connectors. The steel studs and channels are the most popular code accepted connectors. However, economic considerations continue to motivate the development of new products.
Present knowledge of the... 

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... 

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... 

According to recent researches, angle-shape shear connectors are appropriate to transfer longitudinal shear forces across the steel-concrete interface. This study investigates the effect of tilted angle on capacity and behavior of angle-shape shear connectors. In this study, we consider two different tilted angles. Push-out tests consisting of eight specimens made of reinforced concrete and different angle-shapes were conducted. Specimens have tilted anglesof 112.5 and 135 degrees between the angle leg and steel beam. Two different failure modes were observed consisting of concrete crushing-splitting and angle fracture. In addition, a nonlinear finite element model of these push-out... 

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... 

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... 

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... 

Cable-stayed bridges are the most economical solution for spans ranging from about 200 to 1000 meters. They have become more popular in recent decades due to their efficiency and appearance. The need to understand their seismic beahvior is apparent and any improvement can be useful. The main purpose of this study is to determine the effect of using three lateral cable arrangement groups namely, cross system, pulley system and spatial lateral cable system with two transversally inclined cable planes on seismic performance of cable-stayed bridges. In this research, the seismic consequences of these arrangements with interactions of key parameters like, the main span length and deck to pylon... 

Cable stayed bridges have been used extensively in recent years for long span bridges up to 1000m. Although seismic behavior of these bridges has been researched in the last decade, however, the effect of vertical component of earthquake on cable-stayed bridges has not been studied before. In this thesis, the geometric nonlinear static analyses on dead loads followed by linear direct integration dynamic analyses have been used to study this effect. The results of analyses with three-component earthquakes are compared with two-component earthquakes. Fourteen models of cable-stayed bridges with different main span length, shape of pylons and the deck-pylon connection are employed. The errors... 

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... 

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... 

Shear walls are constructed to counter the effects of lateral load acting on a structure. In residential construction, shear walls are straight walls that typically form a box which provides all of the lateral support for the building. When shear walls are designed and constructed properly, and they will have the strength and stiffness to resist the horizontal forces. Thus shear walls are one of the most effective building elements in resisting lateral forces during earthquake. By constructing shear walls damages due to effect of lateral forces due to earthquake and high winds can be minimized. Shear walls construction will provide larger stiffness to the buildings there by reducing the... 

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... 

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... 

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...