Sharif Digital Repository

The main task of the spine from the mechanical point of view, withstand external loads and allow the upper body movements. Hence, as the chief cause of back pain are mechanical parameters. Inability to directly measure the forces acting on the spine as in vivo, further brings us to the use of computer models in various branches of orthopedic biomechanics leads.
The purpose of this project in the first place) to make a detailed finite element model of the L4-L5 spinal motion but, in the second place) loads imposed on it except move in a certain physical activities, taking into account the forces acting muscles (calculated by a musculoskeletal model is available) under which they operate,... 

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... 

Financial losses and casualties due to the collapse of the masonry facade and the infill walls of the building in recent earthquakes were motivators of this research to study seismic performance assessment of masonry facade. One of the main reasons for the collapse of buildings facade is their inadequate connection to the infill walls and structure frame. The mentioned item caused when earthquakes such as Kermanshah earthquake occurred, although a large number of buildings remained undamaged in terms of their structural, facades of these buildings collapsed. The details of the masonry facade, such as the metal wires mentioned in the codes, are not usually applied in Iran, and the connection... 

Spine biomechanical models suffers from either simplification in passive disc components modeling (modeling via torsional spring or beam elements) in musculoskeletal (MS) models or shortcomings in detailed muscles modeling (via a simple force and torque vector) in detailed finite element (FE) models. Considering these, that is aimed in this study to develop a hybrid MS-FE model which the calculated muscle forces by a MS model (developed based on geometrical and mechanical properties of FE model) for a desired static posture, being applied to a detailed FE model. Considering the change of discs stiffness in FE model under the applied muscles and gravity forces, the equivalent stiffness in MS... 

Congenital heart defects are a type of heart diseases that some babies get at birth. These diseases generally have symptoms such as shortness of breath, headache, impaired blood supply, hyperplasia of the lungs, enlarged heart, and so on. In the past, open heart surgery was commonly used to treat such diseases, which was a costly and risky procedure. But over time, occluders made it easier. An occluder is referd to a device that is generally minimally invasive in the area of the fault and could block it. The occluders are usually braided type, with inside polyethylene fibers, where tissues can grow and clogs the defect over time. Although occluders have greatly increased the success rate of... 

In this research, the application of composite patch in the repair of pipes damaged by corrosion has been investigated. Numerical modeling, artificial neural network and Taguchi algorithm are used for this purpose. In the numerical modeling section, the accuracy of modeling performance has been verified by experimental results of other researchers. Then, the effect of various parameters such as depth and, angle of corroded area, fiber orientation in the composite patch and angle of composite patch have been investigated. The depth and the angle of the corroded area and the angle of orientation of the fiber have been shown to have a large effect on the growth life of fatigue cracks. For... 

Preservation of historical monuments is a very important issue for future generations. The importance of this issue is doubled when we know that most of these buildings are traditionally built and do not have a single structure to withstand seismic loads. One of such buildings in our country is Bam Citadel, which was completely destroyed as the oldest brick building in the world during the 2003 Bam earthquake.In this project, we will try to find a model that can determine the structural behavior of the historical dome of Soltanieh for engineers in a case study. This building is a brick dome with a height of 48.5 meters and a diameter of 24.4 meters from the seventh century , which is unique... 

Nowadays, in many of industrial processes, it’s necessary to measure acceleration of a moving object. Among the different type of accelerometers, the piezoelectric type are most useful and the most widely used. These sensors come in various configurations.
In the past, analytical and semi-empirical models have been used to design piezoelectric accelerometers. In these methods, based on some assumptions, the accelerometer nonlinear model is replaced with a linear model and the equivalent circuit model has been used to model accelerometer behavior. In these methods, the behavior of accelerometer become different from the expected one.
Recently, with the invention of efficient computing... 

This study aims to provide a multiscale model of traumatic brain injury including the three levels of macro, meso, and microscale information. In order to do this, a macroscale voxel-baed model of human head was constructed. The model was designed and generated to include mesoscale tissue information as well as a voxel-based approach to include voxel-based microscale data and to be coupled in a multiscale framework. Next, three different microscale models were constructed. The variations of fractional anisotropy within one standard deviation in the regions (including 60% to 70% of voxels) can change the stiffness of the tissue by up to the considerable amount of 40%. The microscale models... 

Passive finite element (FE) models of the spine are commonly used to simulate intact and various pre- and postoperative pathological conditions. Being devoid of muscles, these traditional passive FE models are driven by simplistic loading scenarios, e.g., a constant moment and compressive follower load (FL) that do not properly mimic the complex in vivo loading condition of the spine under muscle exertions. The present works therefore aims to develop novel passive FE models that are driven by more realistic yet simple loading scenarios, i.e., in vivo measured vertebral rotations and pathological-condition dependent FLs (estimated based on detailed musculoskeletal finite element (MS-FE) spine... 

In this study, the behavior of box column subjected to constant axial load with cyclic lateral force have been investigated by Finite Element method. The resulf of FE anslysis are in a good agreement with experimental result in predicting of behavior and performance of box column. In order to investigation of behavior uses of some performance indices such as axial shortening, over strength, plastic hinge length, out of plane deformation and rotation capacity. The effect of significant parameter such as axial force to yield strength ratio, flange whidth to thickness ratio of flange, web whith to thickness ratio of web, global slenderness ratio and loading protocol on performance indices have... 

Tests have shown that concrete post-tensioned slab under heat condition suffer a significant reduction in stiffness and strength. Design and implementation of post-tensioned concrete slabs with large spans of industrial structures exposed to extreme variation in temperature can be possible with detailed research on its behavior under heating condition. In this study numerical modelling of PT concrete slabs with unbonded tendons under heating condition was created based on available test results in the literature. A parametric study has been carried out and the results are presented for concrete coefficient thermal expansion, thermal contact conductance between the concrete and the cables,... 

Gearbox is one of the important components of power transmission chain in the car which the engagement of the gears inside it causes noise. The following thesis, is in line with the project that was defined as "NVH reduction of the Tiba X200 gearbox" and to increase the correlation between university and industry, the aim of which was to improve all the noise sources in the mentioned vehicle. The purpose of this project is to reduce the noise of the gearbox shell by using reinforcing blades called ribs. For this purpose, first the desired changes were made in Solidworks software on the 3D model of the gearbox shell, and then the finite element model of the gearbox shell was prepared in... 

Background: Degeneration of intervertebral joints due to kinetical alterations after fusion surgery is a prevalent back disorder. While in-vivo studies are limited to medical imaging techniques, in-vitro and in-silico (passive FE modeling) investigations lack the crucial role of muscle forces. Available musculoskeletal modeling studies, not only suffer oversimplification of intervertebral joints, but have some shortcomings in incorporation of the contributing factors (that may alter postoperative kinetics). On the other hand, one of the main shortcomings in the available musculoskeletal models is their inability to account for dynamic effects and modeling transient events. Purpose: 1-... 

Millions of people due to factors such as osteoporosis, aging, sports incidents, and accidents face complications from bone fracture injuries every year. Nitinol shape memory alloy and Gyroid metamaterial have attracted researchers to use them as suitable replacements to fill empty areas of broken bones. In this research, numerical modeling and additive manufacturing were used to take advantage of the special properties of both nitinol and gyroid structures. In the modeling section, finite element modeling of the superelastic effect and the one-way shape memory effect of sheet and solid gyroids in cubic and cylindrical geometries with different porosities were done. As a result of the... 

Spinal Column is one of the most important parts of musculoskeletal system. Injuries in this region are so rampant and causing vast expense. Risk factors related to spine injuries included personal related ones such as, age, sex, muscles’ strength and career related ones such as body positions at work place and loads. Since in vivo measurements have many restrictions, developing biomechanical models that simulate the response of a person to given loads and conditions has important role in preventing injuries and improving working conditions. Inputs to current models of the spine are considered to have mean value, therefore muscles’ forces and other outputs of these models have single value... 

The purpose of this research is to monitor the health of structures using the updated finite element model, in which digital images are used to optimize the numerical model. Structural Health Monitoring (SHM) is always an important and significant issue that has attracted the attention of many researchers in recent years. In general, some researches have been conducted in this field using physical sensors that provide discrete data to the system for analysis. Using cameras to monitor the structure makes it possible to extract continuous and integrated data from the structure using digital images, which is a significant advantage compared to physical sensors.In this research, a steel... 

In this dissertation, the location and severity of the damage are obtained using a new robust Power Spectral Density (PSD) sensitivity-based model updating method. PSD of structural response is highly sensitive metric to parameter change and provides vast information about the structure. The proposed damage detection method uses the sensitivities of measured responses in frequency domain, for FE model updating in an efficient way, by developing a quasi-linear sensitivity equation of structural response. The system of equations are solved using Least Square method. Only stiffness parameters were updated through model updating and change in mass parameters were neglected. In this study, proper... 

Spinal fusion surgery is usually followed by accelerated degenerative changes in the unfused segments above and below the treated segment(s), i.e., adjacent segment disease (ASD). While a number of risk factors for ASD have been suggested, its exact pathogenesis remains to be identified. Finite element (FE) models are indispensable tools to investigate mechanical effects of fusion surgeries on post-fusion changes in the adjacent segment kinematics and kinetics. Existing modeling studies validate only their intact FE model against in vitro data and subsequently simulate post-fusion in vivo conditions. The present study provides a novel approach for the comprehensive validation of a lumbar...