Sharif Digital Repository

Flexible steel frame system is the most common structural system for mid-rise buildings. Northridge earthquake is turning point in designing flexible steel frames and their connections. During this earthquake a large number of beam-column connections in such structures were ruptured in a brittle manner. After this earthquake many researches were conducted on a variety of beam-column connections with an aim of improving their behavior during earthquake. One such connection which have been studied extensively both experimentally and analytically is a connection with Reduced Beam Section (RBS). The most important advantage of this connection is its high ductility and its ability to dissipate... 

A significant amount of research on self-consolidating concrete (SCC) technology has been devoted to evaluating the suitability of the material for its use in structural applications. However, more research is required to confirm the adequacy of SCC structural members for resisting gravity and seismic loads. This study focuses on the experimental investigation of the seismic performance of interior reinforced concrete beam-column connections with SCC. Four beam-column connection specimens, three with SCC and one with normally vibrated concrete (NC), were designed for this experimental study. Factors such as concrete type (SCC or NC) and axial load ratio (0, 7.5 and 15 % of column section... 

The presented studies have been conducted on the scope and magnitude of damages inflicted by earthquakes over the years. Many RC buildings, designed and constructed in the 1960s and 1970s, have serious structural deficiencies, especially in their beam-column joints. Such deficiencies result from inadequate joint shear strength or confinement of column reinforcement. The joints require elaborate retrofit measures to ensure the performances comparable to those of new designed structures. In this research, a new seismic retrofitting method is presented for beam-column joints based on the two-dimensional enlargement of the joint by using steel plate, angles, and posttensioning rods. The seismic... 

Vibration behavior of adaptive laminated composite beams integrated with magnetorheological (MR) fluid layer has been investigated using layerwise displacement theory. In most of the existing studies on the adaptive laminated beams with MR fluids, shear strain across the thickness of magnetorheological (MR) layer has been assumed a constant value, resulting in a constant shear stress in MR layer. However, due to the high shear deformation pattern inside MR layer, this assumption is not adequate to accurately describe the shear strain and stress in MR fluid layer. In this work a modified layerwise theory is employed to develop a Finite Element Model (FEM) formulation to simulate the laminated... 

We used an extension of the Variable Material Property method for materials with varying elastic and plastic properties to evaluate the residual stresses in an autofrettaged thick vessel made of functionally graded metal-ceramic composite. It is shown that the reinforcement of the metal vessel by ceramic particles, with an increasing ceramic volume fraction from inner to outer radius, increases the magnitude of compressive residual stresses at the inner section of an autofrettaged vessel and thus, could lead to better fatigue life and load-carrying capacity of the vessel. A parametric study is carried out to highlight the role of ceramic particle strength and spatial distribution, as well as... 

Laminated composite beams with non-uniform thickness are being used as primary structural elements in a wide range of advanced engineering applications. Tapered composite structures, formed by terminating some of the plies, create geometry and material discontinuities that act as sources for delamination initiation and propagation. Any small damage or delamination in these structures can progress rapidly without any visible external signs. Due to this reason early detection of damage in these systems during their service life is receiving increasing attention. The presence of a crack in a component or structure leads to changes in its global dynamic characteristics results in decreases in... 

Two new displacement potential functions are introduced for the general solution of a three-dimensional piezoelasticity problem for functionally graded transversely isotropic piezoelectric solids. The material properties vary continuously along the axis of symmetry of the medium. The four coupled equilibrium equations in terms of displacements and electric potential are reduced to two decoupled sixth- and second-order linear partial differential equations for the potential functions. The obtained results are verified with two limiting cases: (i) a functionally graded transversely isotropic medium, and (ii) a homogeneous transversely isotropic piezoelectric solid. The simplified relations... 

This research investigates the flexural behavior of a polymer concrete beam/pile encased with carbon fiber sleeve. The mechanical properties of carbon fiber sleeves in tension and cement and polymer concrete in compression were determined. Polymer concrete beams were tested in flexure to determine the bending moment capacity. Then, the test results were compared to the theoretical model results. Finally, a parametric study was conducted to determine the influence of beam/pile parameters on the capacity of the element. Based on the investigation, carbon fiber sleeve filled with polymer concrete exhibits outstanding structural performance including ductility and bending capacity. © 2017 Taylor... 

Thermal cracking is the prevalent type of distress experienced by asphalt pavements in cold regions. It is widely assumed that when thermal stresses induced in the pavement exceed the tensile strength of the asphalt surface layer, cracking occurs; however, the role of thermal fatigue should not be ignored. To better describe the low-temperature (LT) performance properties of modified asphalt binders, a new parameter, normalised tensile stress (NTS), was defined in this research. NTS values were compared with bending beam rheometer (BBR), direct tension (DT) and semi-circular bending (SCB) fracture test results. The m-value parameter of the BBR test specifies the type of asphalt binder. This... 

Double-web angle connection is one of the most rudimentary connections in simple structural systems such as braced frame system. It is essentially presumed in conventional designs that double-web angle connection behaves as a hinge connection. However, in braced frames, due to existence of braces in some bays, in specified locations where gusset plates of brace are placed with beam-to-column connection in one joint, this assumption may not be accurate. This is due to the restraining of the beam from rotation by gusset plates that are placed either on the top and bottom of the beam or only on one side. In such cases, the simple beam-to-column connection may be transformed into a semi-hinge or... 

A modified dynamic-based pushover (MDP) analysis is proposed to properly consider the effects of higher modes and the nonlinear behavior of the structural systems. For this purpose, first, a dynamic-based story force distribution (DSFD) load pattern is constructed using a linear dynamic analysis, either time history (THA) or response spectrum (RSA). Performing an initial pushover analysis with the DSFD load pattern, a nonlinearity modification factor (NMF) is calculated to modify the DSFD load pattern. The envelope of the peak responses of the structure obtained from 2 pushover analyses with the modified DSFD load pattern as well as the code suggested first mode load pattern are considered... 

The bond of fiber-reinforced polymer (FRP) reinforcement is expected to be more sensitive to the strength and geometry of the ribs than conventional steel reinforcement. In this study, the effect of carbon fiber mat anchorage on the pullout behavior of glass fiber-reinforced polymer (GFRP) bars embedded in normal concrete is studied. The studied parameters were the compressive strength of the concrete (16 MPa, 24 MPa, and 37 MPa), and, the length and diameter of the anchorage. In total, 15 variables were studied. Ribbed GFRP bars with 10 mm nominal diameter and 80 mm embedment length, ld, (which is 8 times the bar diameter) were considered. Based on the results for concretes with the... 

This work is aimed to present analysis on the thermal vibrational behavior of two-dimensional functionally graded porous microbeams based on Timoshenko beam theory. According to the power law function, the material composition and so the material properties are varying along thickness and axis of the microbeam. The governing equations are derived on the basis of the couple stress theory and the generalized differential quadrature method is used to solve the equations. The temperature gradient is considered to be uniform and nonuniform across the thickness of the microbeam. The results are presented to show the effect of temperature change, porosity, functionally graded and axially...