Sharif Digital Repository

Damage detection and rehabiltation is one of the most economical methods of increasing safety and service life of the structures. In this research, a wave-based methodology is introduced for laminar damage location in single axial members and combined axial-flexural members within a structure. Laminar damage is a kind of local damage in which the cross section area of a member decreases within a specific length. In the proposed wave-based methodology, a structure with a laminar damage is analyzed using a Finite Element (FE) software under a high frequency loading, and the strain values in specific points of the structure is collected. Thereafter, using the wave propagation theories and the... 

In this research, seismic loss of eccentrically braced frame buildings is assessed by using reliability methods. For this end, first, Bayesian linear regression is utilized to characterize the epistemic uncertainty of the problem in the form of damage models. The input of these models are mechanical and physical properties of the components, and the outputs are damage ratios. In the second step, by using the developed models and the comprehensive library of probabilistic models of Rt, reliability analysis is conducted on 4, 8, and 16 stories building located in San Jose. The limit state function is seismic loss, including repair loss, collapse loss, and demolition loss, and analysis method... 

Up till now, various contributions of research to soil-structure-interaction context have been primarily focused on structural systems exhibiting elastic-perfectly plastic material behavior. In this paper, combined effects of material degradation, p-delta, and soil-structure-interaction considering foundation uplift have been deemed to determine seismic response of a single degree of freedom system. The system is composed of a column with a lumped mass on top that is placed on a rigid foundation. The foundation is mounted on Winkler springs and dashpots to account for soil-foundation compliance and material/radiational damping. The springs are tensionless to guarantee that uplift phenomenon... 

In this paper the predictive equations for collapse assessment of shear links used in eccentric braced frames are developed. An extensive database including results of over 70 cyclic tests on steel wide flange shear links is collected and the structural parameters governing the hysteresis behavior are calibrated using a simplified numerical model. The methodology of calibration is to minimize the discrepancy between the experimental hysteresis loops and the corresponding numerical results using Particle Swarm Optimization (PSO) algorithm. The objective function of PSO algorithm is minimized by iterating parameters that govern the hysteresis behavior of the numerical model. Stepwise... 

The aim of this study is introducing and assessing two torsion-based metallic dampers which are named Torsional Disc and Torsional Cylinder dampers based on their geometry and energy absorption mechanisms. As expected, a steel disc and a steel cylinder are exposed to torsion in the Torsional Disc and Torsional Cylinder dampers respectively, and energy absorption occurs through torsional yielding of those two elements. In the introduction section, a mechanism is introduced to put the dampers under pure torsion so as to yield a desirable performance. The dampers are designed to be placed between Chevron braces and the floor beam, and the pure torsion is exerted, through the mentioned... 

The purpose of this paper is to quantify the extent of damage of rectangular reinforced concrete shear walls after an earthquake using surface crack patterns. One of the most important tasks after an earthquake is to assess the safety and classify the performance level of buildings. This assessment is usually performed by visual inspection that is prone to significant errors. In this research, an extensive database on the images of damaged rectangular reinforced concrete shear walls is collected from the literature. This database includes more than 200 images from experimental quasi-static cyclic tests. Using the concept of Fractal geometry, several probabilistic models are developed by... 

This study investigates the seismic behavior of eccentrically braced frames (EBFs) taking into account the influence of masonry infill walls. The primary objectives of the study are to predict the seismic global response and develop associated fragility curves using a nonmodel scenario-based machine learning framework. To model the infill walls, equivalent diagonal struts are employed, and a nonlinear pushover analysis is conducted to assess the overall impact of infills on 4- and 8-story EBF structures. An extensive database of 4 bare and 48 infilled EBFs with various infill properties is assembled to predict story-based engineering demand parameters (EDPs) containing peak and residual... 

This study investigates the effect of the variation of the properties of unreinforced brick masonry walls, such as aspect ratio, prism strength, and axial load ratio, on determining the post-earthquake damage states of the walls using fragility curves. A database comprising 245 damaged unreinforced masonry walls is collected that have been tested under the quasi-static cyclic loads up to more than three percent drift ratios. The collected walls are categorized into four damage states according to the resisting lateral force during the cyclic loading obtained from the backbone of the hysteresis curves. Then, multivariable fragility surfaces based on the drift ratio and design properties of... 

The aim of this research is to predict the backbone curve of reinforced concrete shear walls by identifying different failure modes. Failure mode identification is performed by measuring the contribution percentage of flexure, shear, and combined flexure-shear failure modes in the force-displacement response of the wall under cyclic loading. The approach used in this research is a probabilistic and data-driven method, which leads to the calculation of model uncertainty in detecting the wall's failure mode and, consequently, the prediction uncertainty of the backbone curve. The database used in this research consists of 253 reinforced concrete shear walls, obtained from a review of existing... 

Damage detection of civil structures and infrastructures using partial modal information has been an interesting field of research. So far, three main algorithms are introduced for health monitoring of structures. The first method relies on identifying stiffness and mass properties, as physical parameters, of structures using inverse eigenvalue problem considering mass modifications in 2D and 3D shear-frame models of structures. Comparing the identified matrices with the primary values, one can detect the damage occurrence, its level and severity in the structure. Applicability of this method in health monitoring of offshore jacket platforms as one of noteworthy civil infrastructures has... 

The common approach toward soil-pile-structure interaction phenomenon is that it will cause an increase in both effective natural period and damping ratio. Therefore, considering such a phenomenon in design and analysis of piled structures, will lead to smaller displacements. This attitude has gone far in a way that in different suggestions in various practices, this subject is neglected in a conservative manner. In this study, by investigating the response of a single degree of freedom structure founded on a pile group as the first vibrational mode of a structure, by the means of calculating several displacement ratios, has been proved that soil-pile-structure interaction can cause an... 

In order to investigate the behavior of unreinforced masonry buildings and the effects of shotcrete retrofit, a half-scale one-story masonry building was constructed and tested on the shake-table of Earthquake Research Center at Sharif University of Technology (SUT), Iran. The project was jointly founded by SUT and Ecole Polytechnique Fédérale de Lausanne (EPFL), with the support of The Organization for Development, Renovation, and Equipping of Schools of I.R Iran (DRES). The 3.7×3.7×2 [m] specimen was modeled after a typically built classroom, with eccentric window openings on one wall and a door opening on the opposite wall. The walls were constructed using half-scale 10.5×5.0×2.9 [cm]... 

Most of the previous studies as well as codes regarding unreinforced masonry walls overlook the effects of perpendicular walls – called flanges – on their behavior; in reality, these transversal walls significantly affect ultimate strength, stiffness, drift capacity, and most importantly the failure modes. In this thesis, numerical finite element modeling was employed in order to investigate the impact of flanges on unreinforced masonry walls subjected to gravity loads and lateral pushover excitation. Moreover, a sensitivity analysis was conducted concerning the effect of different boundary conditions and axial load ratios on failure mode and crack pattern of the flanged walls. First, the... 

The purpose of this paper is to estimate the stiffness and strength of damaged rectangular reinforced concrete shear walls after an earthquake using surface crack patterns. Assessing the damage severity of buildings after an earthquake is an important part of the emergency inspection operation of buildings. Expert inspectors tag buildings into two categories of safe or unsafe that are usually affected by subjective decisions, which may result in catastrophic events reported in previous earthquakes. In this research, an extensive database on the images of damaged rectangular reinforced concrete shear walls (RCSWs) is collected and used to develop predictive equations for updated stiffness and... 

This study presents a Machine Learning framework for post-earthquake structural damage state and economic loss estimation. The framework is proposed to rapidly determine whether a structure is safe or unsafe to be occupied following a seismic event, to predict the detailed structural response, and finally to evaluate the economic loss of the buildings. An extensive database is developed by analyzing twelve low-rise, mid-rise, and high-rise eccentrically braced frames (EBFs) under 44 scaled ground motion records through incremental dynamic analysis (IDA) to train the Machine Learning algorithms. Machine Learning algorithms are employed to classify the structural damage state of the buildings... 

Although manual crack inspection has been widely used for structural health monitoring over the last decades, the development of computer vision methods allows continuous monitoring and compensates the human judgment inaccuracy. In this study, an image-based method entitled, Arc Length method is introduced for extracting crack pattern characteristics, including crack width, and crack length. The method contains two major steps; in the first step, the crack zones are estimated in the whole image. Afterwards, the algorithm finds the start point, follows the crack pattern, and measures the crack features, such as crack width, crack length, and crack pattern angle. The efficiency of the method... 

This research proposes a damage assessment framework based on the visual features of a damaged reinforced concrete shear wall, such as crack pattern distribution, crushing areal density, aspect ratio, and the presence of the boundary condition. The study contains two parts: identifying the performance level of the damaged walls (i.e., Immediate Occupancy, Life Safety, and Collapse Prevention) and estimating the residual strength and drift ratio of the walls. The research database contains 236 images of 72 reinforced concrete shear walls tested in the laboratory under the quasi-static cyclic loadings at various drift ratios between 0.0 to 4.0. To identify the performance level of a damaged... 

The main objective of this research is to use the visual features of damage in evaluating the post-earthquake status of the damaged structures. Structural health monitoring, as a comprehensive approach, includes methods for identifying the damaged structures, estimating damage location, measuring damage extent, and methods for reconstructing and repairing structures. The present study is specifically focused on the second and third stages of structural health monitoring, including “estimating the location of damage” and “measuring the extent of damage”. Various methods for evaluating the condition of earthquake-damaged structures are available in technical literature; one of the most common... 

Based on the code specifications, in moment-resisting frames the span-to-depth ratio has to be larger than a minimum value to make sure of adequate plastic hinging at beam-ends. This provision poses a restriction on the use of deep beams with short spans, especially for the framed-tube system in tall buildings. In this thesis, a new energy dissipation method is introduced for moment-resisting frames by modifying the mid-span of the beam by two different methods, resulting in: (i) Perforated Shear Links (PSLs) and (ii) Slit Shear Links (SSLs). The links dissipate energy through shear yielding of the web, weakened by perforation or slitting, respectively. A thorough study is conducted on the... 

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...