Sharif Digital Repository

The present paper proposes a micromechanical damage model for two and three dimensional Representative Volume Element (RVE) with randomly distributed cohesive rough slit-like and penny-shaped micro cracks (Barenblatt-Dugdale type). First, the influence of crack roughness on the crack opening under macro hydrostatic stress state is studied and then the energy release contribution to material damage process is estimated. Considering the fractality of the crack trajectories yields to lower values of the volume crack opening. This will result in lower energy release rate in RVE and higher levels of material resistance. Based on the energy release rate of RVE, the effective material properties... 

In this research, a single degree of freedom (SDOF) system equipped with a telescopic damper is analyzed under earthquake excitations. In order to assess the effectiveness of telescopic damper, some SDOF systems equipped with other types of dampers including viscous damper, friction damper, T-ADAS damper, and Curadelli’s lead damper(CLD) are also analyzed under similar excitations. Inspired by CLD damper, this TLSD damper is primarily introduced, developed and tested at Sharif University of Technology in Tehran by Mr. Pournamazian in 2016. Results shows that the telescopic lead shear damper can increase the CLD damper displacement by 100%. To get better results in terms of damper’s behavior... 

The purpose of this thesis is the optimal retrofitting of the moment resisting frames with telescopic dampers, using the adaptive approach. In this regard, numerical modeling of the telescopic behavior has been presented firstly. Also, a 3,9,20 story (sac) moment resisting frame has been modeled in the OpenSees environment and the time history analysis has been carried out under a specific earthquake record. It is shown that inter-story drifts of the frame exceed the acceptance criteria which has been assumed 2.5% according to the Life Safety limit. Then, the optimal retrofitting of the frame has been done. It is demonstrated that the maximum inter-story drift of all stories is 2.5% or less,... 

Conventional lateral resisting systems can provide sufficient strength and ductility for design based earthquakes, although the considerable residual deformation remaining in the plasticized regions undermines the resiliency of the structures. In order to resolve this problem, various self-centering systems have been proposed and tested in recent years, most of which are specified for new buildings and are not simply suitable for retrofitting applications. Moreover, the available self-centering systems are costly and complex to assemble, which can be considered as a serious barrier for practical application. To address these drawbacks, an innovative core-less self-centering (CLSC) brace is... 

In computational mechanic, paying attention to new methods of problem solving is very important. These approaches can offer more desirable results than the standard finite element method. The extended finite element method (X-FEM) is one of them, which is applied in modeling of discontinuities, singularities, crack propagation and etc. In this method, we do not need to align the element edge with the boundary of discontinuity. It means that the elements can be cut by interface (enriched elements) in the discontinuity boundary. One of the difficulties in (X-FEM) is blending elements, which happens in elements that are blended to enriched element that can decrease the convergence rate. The... 

This thesis investigates the dynamic response of a viscoelastic plate resting on a viscoelastic Winkler foundation subjected to the excitation of a moving mass. Through application of the Laplace transform, the governing equation of the problem is derived for a general viscoelastic material. Thereafter, an analytical-numerical method is proposed in order to determine the dynamic response of the viscoelastic 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... 

In recent decades, restoring residual deformations and adding the capability of returning to initial deformed state was investigated by many researchers. Steel Plate Shear Wall (SPSW) is one of structural earthquake resisting system that have high ductility capacity and good energy absorption property. On of major issues in SPSW systems is intense nonlinear deformation in panel’s infill web plate and this panels vertical and horizontal boundary elements. By incorporating Shape Memory Alloy (SMA) connections we can add returning to first deformed condition (self-centering) and sustain high ductility capacity to many structures. In this research the addition of SMA connections to SPSW system... 

Most regions in Iran are located on an active plate boundary. Therefore, many parts of the country face a risk of earthquake damage at some point in time. Therefore, anticipating and addressing the consequences of earthquake events in order to minimize loss of life and damage to property is a national issue.There is concern about the ability of a signification fraction of buildings in Iran to withstand earthquake events. The deficiencies in the design and construction of buildings in Iran result in low-quality buildings vulnerable to earthquakes. It is necessary to identify and investigate the parameters that contribute to these deficiencies.Previous research studies indicate that...