Sharif Digital Repository

In this paper the performance of light weight K-braced cold formed steel (CFS) shear panels under cyclic loading is experimentally evaluated. It is generally known that the brace-stud connection details has an important effect on the performance of the braced CFS shear panels in terms of lateral stiffness, energy dissipation, and ductility factor. In this study, four full-scale, 2.4 m × 2.4 m, braced CFS shear panels made of C-sections were tested. It was observed that proper modification of the currently utilized braced to stud connections in K-braced, CFS shear panels could enhance their performance considerably by increasing their ultimate shear resistance up to 7 folds. Furthermore,... 

Damage detection of a full-scale nine-story reinforced concrete building is investigated using forced vibration test (FVT). The building was the former Civil and Architecture Department of Tohoku University located in Sendai Japan. Earthquake resistance elements of this building were severely damaged in 1978 Miyagi-Ken Oki earthquake and the building was retrofitted on 2001. FVT was performed on the structure before and after retrofitting with same sensor arrangement. Using data acquired from sensors, system identification was performed using rational fraction polynomial and the damage assessment (detection and location) was done by modal assurance criterion and its derivatives. The results... 

Different values have been assigned to the ratio of the deflection amplification factor (Cd) to the response modification factor (R) for a specified force-resisting system in the seismic design provisions while the same application is defined for it. An analytical study of the seismic responses of several reinforced concrete frames subjected to a suite of earthquake records performed in this research indicate that the stories’ overstrength and stiffness distribution along the structural height can affect local deflections more than global ones. Therefore, the Cd/R ratio is calculated based on the ratio of both maximum inelastic to maximum elastic displacements and... 

In this paper, a new sensitivity-based model updating method is presented based on the changes of principal components (PCs) of frequency response function (FRF). Structural damage estimation, identification of damage location and severity, is conducted by an innovative sensitivity relation. The sensitivity relation is derived by incorporating PC analysis (PCA) data obtained from the incomplete measured structural responses in a mathematical formulation and is then solved by the least square method. In order to demonstrate the performance of the proposed method, it is applied to a truss and a frame model. The results prove the ability of the method as a robust damage detection algorithm in... 

Although the use of artificial-markers improves the performance of the image-based procedures, there is a problem with the access to their installation place. Moreover, increasing the accuracy and efficiency of the available methods for structural-health-monitoring (SHM) is an important issue in recent years. Therefore, the purpose of this study is to enhance the image-based, full-field displacement measurement using new template-matching and camera-calibration methods. Furthermore, considering practical methods to increase the number of pixels in the images, the possibility of using free markers and improving the camera-calibration methods are investigated. The suitability of the proposed... 

In this study, a nonlinear absorber that works with a negative stiffness mechanism is suggested to mitigate vibration, and its effect on the reduction of vibration is investigated. The negative stiffness, which is inherently nonlinear, creates internal resonance; therefore, the vibration energy can be transmitted from low-frequency to high-frequency vibrating modes, causing vibration suppression. The nonlinear absorber is added to the primary nonlinear system, and when the main system is subjected to external resonance due to harmonic excitation, the negative stiffness parameter of absorber is so adjusted that autoparametric resonance occurs and vibration is reduced. First, the mathematical... 

In this study, a nonlinear absorber that works with a negative stiffness mechanism is suggested to mitigate vibration, and its effect on the reduction of vibration is investigated. The negative stiffness, which is inherently nonlinear, creates internal resonance; therefore, the vibration energy can be transmitted from low-frequency to high-frequency vibrating modes, causing vibration suppression. The nonlinear absorber is added to the primary nonlinear system, and when the main system is subjected to external resonance due to harmonic excitation, the negative stiffness parameter of absorber is so adjusted that autoparametric resonance occurs and vibration is reduced. First, the mathematical... 

The optimal distribution of fluid viscous dampers (FVD) in controlling the seismic response of eccentric, single-storey, moment resisting concrete structures is investigated using the previously defined center of damping constant (CDC). For this purpose, a number of structural models with different one-way stiffness and strength eccentricities are considered. Extensive nonlinear time history analyses are carried out for various arrangements of FVDs. It is shown that the arrangement of FVDs for controlling the torsional behavior due to asymmetry in the concrete structures is very dependent on the intensity of the peak ground acceleration (PGA) and the extent of the structural stiffness and... 

The governing differential equation of motion for an undamped thin rectangular plate with a number of bonded piezoelectric patches on its surface and arbitrary boundary conditions is derived using Hamilton's principle. A moving mass traveling on an arbitrary trajectory acts as an external excitation for the system. The effect of the moving mass inertia is considered using all the out-of-plane translational acceleration components. The method of eigenfunction expansion is used to transform the equation of motion into a number of coupled ordinary differential equations. A classical closed-loop optimal control algorithm is employed to suppress the dynamic response of the system, determining the... 

In order to evaluate the seismic behavior of confined masonry buildings, based on Iranian seismic code design, a single storey full-scale unreinforced confined brick masonry building has been constructed on the shaking table facility at the Earthquake Engineering Research Center (EERC) of Sharif University of Technology. The 4 by 4 meter model consists of four brick masonry walls confined with reinforced mortar tie-columns and steel bond beams, with a traditional jack-arch roof system. Three of the wall panels contained openings of different sizes and geometries. The model was subjected to the scaled earthquake records of Bam, Tabas and El Centro, as well as a harmonic acceleration with... 

Seven half-scale reinforced concrete (RC) columns with supporting beam were experimentally studied under combined axial and lateral cyclic loading. The specimens were categorized in two groups based on reinforcement ratios. Three specimens were strengthened with carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP) sheets. Other specimens were strengthened using a high strength mortar reinforced with textile mesh (textile reinforced concrete (TRC)). Strengthening of specimens were carried out using a vertical layer and a horizontal layer of FRP sheet or two vertical and two horizontal layers of textile meshes for TRC specimens. Since the weight of each layer of... 

A simple Dynamic-based Pushover analysis for Plan Asymmetric buildings (DPPA) is proposed with the aim of properly considering the effects of torsional behavior as well as the higher modes in the applied lateral load pattern. According to the proposed method, the peak story drifts obtained from the response spectrum analysis (RSA) can be resolved into their translational and rotational components, and the related equivalent static lateral forces and torsional moments can be calculated. Consequently, for accurate estimation of the maximum drift demands of plan-asymmetric buildings, it is proposed that the drift responses obtained from the RSA for the stiff and flexible edges of the building... 

Dynamic deformations of beams and plates under moving objects have extensively been studied in the past. In this work, the dynamic response of geometrically nonlinear rectangular elastic plates subjected to moving mass loading is numerically investigated. A rectangular von Karman plate with various boundary conditions is modeled using specifically developed geometrically nonlinear plate elements. In the available finite element (FE) codes the only way to distinguish between moving masses from moving loads is to model the moving mass as a separate entity. However, these procedures still do not guarantee the inclusion of all inertial effects associated with the moving mass. In a prepared...