Sharif Digital Repository

Integral abutment bridges (IABs) are bridges in which the deck is cast monolithically with abutment backwalls. These bridges are also jointless through deck length, due to which they act as a frame in their longitudinal direction. These differences with common seat-type bridge construction, have made IABs more economical to build and maintain and superior in seismic performance. As such, in various countries, this method of construction have been prescribed whenever possible. As an instance, integral construction is mandatory for bridges up to 60 meters in total length in England. IABs have become more of a geotechnical problem rather than simple structural problem of conventional bridges in... 

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... 

Following inadequate performance of bridges during the past earthquakes, serious attention has been drawn to evaluation of seismic vulnerability of existing bridges and retrofit measures. This research surveys seismic performance of existing bridges according to the latest manual for seismic rehabilitation of highway bridges in America (FHWA2006). This manual introduces six different methods which vary considerably in sophistication, rigor and applicability. This research is based on method D2 (Nonlinear Static Procedure or Pushover Method) in which the seismic demands are determined by elastic methods such as multi-mode response spectrum, or elastic time history method and capacity... 

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... 

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,... 

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... 

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... 

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... 

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 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... 

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... 

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... 

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... 

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... 

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...