Sharif Digital Repository

Plates on elastic foundations have attracted the attention of many researchers. Some elementary models have been introduced to consider interactions between the plate and its foundation. Other improved models have been proposed to develop basic models. In this work, a model based on the Winkler-foundation theory is proposed, while the constant parameter of Winkler is assumed to be variable; such as non-uniform springs with the functionality of the domain position, along with the plate and beam span in order to consider the non-uniform behavior of the foundation. The governing equation on the system is solved by using the Galerkin method and effects such as the presence of rigid points in the... 

In this paper, a new structural lateral bracing system called 'Chevron Knee Bracing' (CKB) is investigated. This new form of framing system is constructed through the knee and the diagonal brace elements. The knee part is a fuse-like component that dissipates energy by the formation of plastic flexural and/or shear hinges at its ends and mid-span, when the building is subjected to severe lateral loads. However, the diagonal brace component, on the other hand, provides the required level of lateral stiffness and remains in the elastic range without buckling at any time. In this investigation, first, by studying of the system in the elastic region, three new and practical parameters are... 

In this paper a particular structural bracing system, called the Chevron Knee Bracing (CKB), is introduced. In this framing system, a special form of diagonal braces that are connected to knee elements instead of beam-column joints is investigated. The braces provide required stiffness during moderate earthquakes, while the knee elements yield in flexure or shear to dissipate energy during a severe earthquake, whereby buckling of the braces or yielding of the main structure is prevented. First, elastic analysis is applied to the new system and a suitable shape and angle for the knee and the brace elements is proposed, using new and practical parameters. Then, by developing a nonlinear... 

This article extends a procedure that has been used to discretize a continuous flexible beam into a system of rigid bars and joints, which resist relative rotation of the attached bars. The object of this article is to present and formulate a simple and practical approximate technique for determining the time response of beams with internal hinges and different boundary conditions, carrying a moving mass. The results are compared with a general-purpose nonlinear dynamic finite element program, and a good agreement is achieved. © 2000 Elsevier Science Ltd. All rights reserved  

Braced frames are prevalently utilized as lateral load resisting systems in common engineering practice. disposable knee bracing (DKB) frames are categorized as one of the well-known types of these frames. In such systems, braces provide stiffness, while the link elements play an important role as an energy-absorbing fuse. During an extreme loading, link members help the structure to dissipate the imposed energy by plastic deformations. In this research, bracing frames took advantage of shear and/or flexural link elements. The previous experimental results revealed that hysteresis behavior of link elements remains constant until a specific rotation. Hence, employing such links as parts of a... 

This research investigated the long-term environmental effects on bond strength at the interface between fiber- reinforced polymers (FRPs) and timber. A total of 581 timber specimens were bonded with seven types of FRP sheets (unidirectional and bidirectional glass, carbon, aramid, and hybrids) using a wet lay-up technique. The specimens were exposed to acidic, alkaline, fresh water, and sea water solutions with pH of 2.5, 7, 7.25, 10, and 12.5 for 1, 3, 6, 9, and 12 months. A chamber was also used to simulate ultraviolet radiation after 6 months. A series of single-lap shear tests were then conducted to determine the interfacial bond strength reduction. The results showed that bidirectional... 

This study examined the bond at the interface of masonry bricks and fiber-reinforced polymer when exposed to five environments. Three fabrics (aramid, carbon, and glass) and one type of epoxy resin were used. A total of 375 brick-fiber-reinforced polymer specimens were made using wet lay-up technic and exposed to chemical solutions at four pH values (2.5, 7, 10, and 12.5) and substitute seawater. The effect of dry heat on the bond at the interface was also investigated. Single-lap shear tests were then carried out on the samples after 2, 4, 6, 8, 10, and 13 weeks of exposure. The experimental results indicated that freshwater and seawater had a considerable effect on the bond strength of... 

This paper presents an effective approach for the seismic design of off-center bracing systems (OBSs). The nonlinear behavior of an OBS can be specified by evaluation of two yielding stages representing tensile yielding of different bracings. This can be achieved when stiffness of the corner brace member is deliberately considered less enough to act as a fuse-like component. An accurate two-dimensional finite element modeling for the geometric and material nonlinearity of such systems considering buckling behavior of the brace members is developed. Through an extensive parametric study, the optimal ratios of the influential parameters of OBS are obtained, and their effects on the nonlinear... 

In this paper, the vibration of a moderately thick plate to a moving mass is investigated. Pasternak foundation with a variable subgrade modulus is considered to tackle the shortcomings of Winkler model, and an analytical-numerical solution is proposed based on the eigenfunction expansion method. Parametric studies by using both CPT (Classical Plate Theory) and FSDT (First-Order Shear Deformation Plate Theory) are carried out, and, the differences between them are also highlighted. The obtained results reveal that utilizing FSDT without considering the rotary inertia leads to a smaller deflection in comparison with CPT pertaining to a thin plate, while it demonstrates a greater response for... 

Bolted Column Base Plate (BCBP) connections are widely used to connect steel columns to the concrete foundations. This paper conducts a parametric study on the initial stiffness of bolted base plate with Square Hollow Section (SHS) column connection, through an extended 3-D Finite Element Modeling (FEM). Different features of the connection such as material behavior, geometric details, typical contact phenomena and large displacements are also considered in the modeling. A comparison between experimental test and FEM is carried out to illustrate the ability of the numerical method to simulate the connection behavior. An analytical explanation on the initial stiffness of the connection is... 

Coupling beams have had a widespread application as performance enhancing devices within concrete structures and more recently also in steel structures. However, the conventional coupling beams are not so efficient in coupling distant walls. In this paper, a novel form of coupling members, namely, coupling panels is proposed and, then, the application for a nine-story building is investigated. Coupling panels are steel plates which are exerted in the intermediate spans between adjacent shear walls and act as a mega-coupling beam. First, a verified finite element model is constructed to demonstrate coupling panel behavior along with its global structural mechanism. Subsequently, a nine story... 

In this paper, the dynamics of a viscoelastic plate resting on a viscoelastic Winkler foundation and traversed by a moving mass is studied. The Laplace transform is employed to derive the governing equation of the problem. Thereafter, an analytical-numerical method is proposed in order to determine the dynamic response of the plate. The method is based on transforming the governing partial differential equation into a new solvable system of linear ordinary differential equations. To that extent, the proposed solution proves to be applicable to plates made of any viscoelastic material and with various boundary conditions. Moreover, the moving mass may travel at any arbitrary trajectory with... 

An analytical-numerical method to determine the dynamic response of beams with various boundary conditions subjected to a moving mass under a pulsating force is explained. Governing partial differential equations of the system are changed to a convenience type of ordinary differential equations to be solved through a Runge-Kutta scheme. Pulsating force specifications influenced the dynamic response of the beam depending on the moving mass properties. Results showed the significant effect of the boundary conditions on the dynamic response of the beam, which was considered rarely in the past. Stiffening the constraints reduces the maximum stresses in the beams. Results for identical... 

In this paper, the steady-state stresses in a homogeneous isotropic half-space under a moving wheel-type load with constant subsonic speed, prescribed on a finite patch on the boundary, are investigated. Navier's equations of motion in 2D case were modified via Stokes-Helmholtz resolution to a system of partial differential equations. A double Fourier-Laplace transformation procedure was employed to solve the system of partial differential equations in a new moving reference system, regarding the boundary conditions. The effects of force transmission from the contact patch to the half-space have been considered in the boundary conditions. Utilizing a property of Laplace transformation leads... 

Studies on corrugated steel shear walls (CSSWs) generally indicate noticeable increase of energy absorption, as well as increasing shear buckling capacity of corrugated plates being more likely rather than the flat plates. In this paper, the effect of variation in the angle of trapezoidal plate on the behavior of CSSWs has extensively been investigated. Three specimens of CSSW with 1 story and single bay in half scale are tested under cyclic load. The observations of experiment do indicate that stress concentration has been increased in the corner of subpanels, by increasing of the corrugation angle. Development of the tensile field and wall yield and damage depends on the geometry of the... 

This research investigated the long-term environmental effects on the bond at the interface between fiber-reinforced polymer (FRP) and a masonry brick. Seven types of FRP fabrics were used and placed on the masonry brick using the wet lay-up technique. Unidirectional and bidirectional fibers made of aramid, carbon, and glass and also combination of these fabrics were used. A total of 525 specimens were exposed to five chemical solutions with pH values of 2.5, 7, 10, 12.5 and substitution sea water for 1, 3, 6, 9 and 12 months. A chamber was also used to simulate the ultraviolent (UV) radiation on the specimens. A series of single-lap shear tests were performed on these specimens to determine... 

The advantages of fiber reinforced polymer (FRP), such as high specific strength, resistance against corrosion and formability, have made it a more acceptable alternative to conventional materials regarding repairing and retrofitting of structures. Although investigations in recent years have proved the concern of civil engineers about the environmental effects on the bond between FRP and concrete or masonry (especially moisture and temperature), only few researches have been reported on FRP-wood interfaces. This research investigated the effect of five different environments on the bond at the interface between FRP and wood. A series of pull-out tests were performed on 375 wood specimens... 

Analysis of concrete shallow funicular shells of rectangular plan with simply supported boundary conditions under static loads is performed using the Ritz method. Double Fourier series with the unknown constant coefficients are assumed for the displacement components of the shell and their unknown coefficients are determined such that the potential energy of the shell becomes minimum. The solution is presented in a simple form and is suitable for practical applications. The responses of rectangular-plan concrete shallow funicular shells including deflections, strains, internal forces, internal moments and stresses could be easily determined using the proposed semi-analytical method. The Ritz... 

Analysis of concrete shallow funicular shells of rectangular plan with simply supported boundary conditions under static loads is performed using the Ritz method. Double Fourier series with the unknown constant coefficients are assumed for the displacement components of the shell and their unknown coefficients are determined such that the potential energy of the shell becomes minimum. The solution is presented in a simple form and is suitable for practical applications. The responses of rectangular-plan concrete shallow funicular shells including deflections, strains, internal forces, internal moments and stresses could be easily determined using the proposed semi-analytical method. The Ritz... 

In this paper, a new analytical approach is proposed for free vibration and buckling analysis of a rectangular Mindlin plate resting on the Winkler–Pasternak foundation of varying stiffness. According to Mindlin theory, there are three independent governing differential equations. Thus, three Fourier series expansions along with auxiliary polynomial functions are employed to represent the plate's deflection and rotation angle functions. The process of making a set of equations is then completed satisfying the corresponding equilibrium equations and boundary conditions. The proposed method incorporates general elastic supports for all plate's edges, and subsequently can deal with all possible...