Sharif Digital Repository

Endurance Time (ET) is a fairly comprehensive analytical method based on time history analysis applied for evaluating structural systems excited by dynamic loading of earthquake. In such evaluation assessment measure is based on endurance time of structure versus applied accelerogram function and parameters such as stiffness, lateral resistance, period of vibration and dynamic characteristics are not used directly. In this research nonlinear dynamic analysis of elevated steel tanks with laterally braced framed tower under the loading of earthquake records and ET accelerograms was studied and effectivity of ET method in analyzing such elevated tanks was verified. Due to complication of... 

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,... 

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... 

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... 

The phenomenon of aging causes a great deal of damage to the airborne structures for which there is a specific maintenance instruction, or if an unexpected damage occurs in specific area of a structure, this damage must be repaired and a special repair process must be designed for it. However, due to the diversity of damages and also variations of the implemented loads, the load is transferred to other structural elements, hence, it is necessary to extend the life of the structure in order to identify these loaded elements and reinforce the applied forces. First, this phenomenon involves a design of a large number of metal patches, where a large number of drills have to be made in the body... 

Dams are huge structures in which safety is a very important issue because a failure will result in loss of lives and finance. Several approximate equations for the approximate analysis of arch dams already exist. These equations are usually obtained by considering the behavior of the dam as a shell. Approximate methods are much faster in comparison to the exact methods and give young design engineers who do not have the experience of designing inside view of displacements, stresses and strains. The aim of this project is to compare the results of approximate analysis of arch dams with the results of finite element models and clarify the points of dams in which approximate analysis methods... 

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... 

Connections have a crucial role in the behavior of every structure. Amongst various types of connections used in steel structures are those used to connect the columns to the foundations, namely Base Plates. As other types of connections, base plates control the behavior of the structure in various respects including affecting the effective length of columns. The main task of any base plate is to distribute the forces of the column on the foundation in such a manner that the stresses in concrete are below their allowable values. Different configurations, with or without various attachments, are used for designing the base plates hence achieving various types of behavior with various levels... 

The objective of this project is to study the behaviour and performance of an innotative floating offshore platform. Such Platform not only can be used for exploring oil from offshore fields, but for creating artificial islands, where land is in short supply. Due to its specific and, at the same time, simple geometry (symmetric), its fabrication does ont involve much complexity. Studies carried out on this platform include the investigation into its structural behaviour under gravitational (including self weight) and bouyancy forces. Studied cases include a number of platforms with different (geometrical) sizes and under 3 various bouyancy conditions (percentage), namely 1) 50% of the height... 

Due to the important role of base plates, both in transferring forces from the structure to the foundation, and also in transferring vibrations from soil to the structure, it is necessary to have sufficient knowledge on their behaviour and performance under monotonic and cyclic loading regimes. In fact, the behaviour of the supports of any structure cannot be identified without identifying the behaviour of its base plates. Numerous configurations with/without various types of attachments have been proposed and used for base plates. In this work, altogether six commonly-used types of base plates were studied and their behaviour under monotonic and cyclic loadings was obtained using commercial... 

Metallurgical phenomena modeling help the researchers to understand the influence and contribution of different factors on the alloys properties. One of the most interesting phenomenon is the aging process occuring in age-hardenable alloys like 2xxx aluminium series. A factor which has high impact on aging and there are not proper models for evaluating that, is the contribution of plastic deformation. This factor has contribution not only on the dynamic precipitation (during deformation) but also on the natural aging after plastic deformation. So in this research a model containing the role of plastic deformation on dynamic precipitation and the contribution of dynamic precipitation on total... 

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 have important role in preventing injuries and improving working conditions.
In the present study, the parametric model of lumbar motion segment is presented, for this purpose, 12 different CT scan pictures were analyzed... 

Spine column is the most important musculoskeletal structures. One of the serious health problems in societies, especially among aged population is osteoporosis. Loss of bone density in bone structures is called osteoporosis which increases the risk of fracture due to a decrease of bone stiffness and bone strength. Spine is the most common sites for osteoporosis-related fractures. Current assessment of osteoporosis status is based on bone densitometry tools like QCT (Quantitative Computed Tomography) or DEXA (Dual Energy X-ray absorptiometry). With these methods it is only possible to estimate density without any consideration the morphology of trabecular making parts like rods and plates.... 

Nowadays, the structural health monitoring is considered as an essential element in improving the performance of the structures. The role and importance of the issues in this area have been reached to the point that different ideas and policies are developed for the safety margin over the useful life of the structures. To analyze more accurately, a real model of a turbine blade is required. This issue would be taken into more consideration when the scale of the turbine gets larger. Changing of the design philosophies over time results in effective changes in the design process and maintenance procedures. Any single of these inspections has different importance according to users' demands. In... 

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... 

The study of bolted moment end-plate connections, both beam to column and beam to beam connections, is quite general and standard nowadays. Buildings which utilize such connections are widely being used and the reorganization of their significant benefits is growing. The research work reported in this thesis presents the results of several parametric analyses to determine the moment–rotation curve of bolted moment end-plate connections utilizing Rectangular Hollow Sections (RHS) and two rows of bolts using Finite Element Modeling (FEM). Previous experimental studies have focused on the moment-rotation relationship under pure bending. This project particularly involves further numerical... 

Etiological studies proves the fact that Low Back Pain (LBP) is one of the most expensive and prevalent desease all over the world. This fact illustrates the reqiurment of the special effort in ordet to reducing the pain due to this problem. Finite element modeling of human spine is one the suitable methods to simulate the behavior of human spine in different loading conditions. These conditions could be different daily occupational tasks. There is two general viewpoint toward finite element modeling of human spine. The fisrt method focuses on the detailed geometry and mechanical properties of spine, while the other complexities such as detailed muscle forces are overlooked. The latter... 

Several geometrically-detailed passive finite element (FE) models of the lumbar spine have been developed and validated under in vitro loading conditions. As these models are devoid of muscles, they are either not used to simulate in vivo activities or muscle forces are modeled by a hypothetical compressive follower load (FL). A number of symmetric and asymmetric static tasks were first simulated using a validated musculoskeletal model of the thoracolumbar spine to predict trunk muscle forces. The predicted muscle forces along with the gravity loading were then applied to a passive FE model of the L4-L5 motion segment (developed and validated here) to estimate load sharing among the disc,... 

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,... 

Coatings are used in order to prevent wear, corrosion, thermal gradient reduction, surface strength improving and many other applications in industries. One of the common applications of coatings, is to prevent wear and surface abrasion. Hardness and friction coefficients are two parameters that determine the wear properties of a coating. Determining these parameters in very thin films is only possible by nanoindentation and nanoscratch tests. Surface hardness, young modulus and fracture toughness can be obtained using nanoindentation and friction coefficient is calculated from nanoscratch.
Finite element method is widely used for simulating the nanoindentation and nanoscratch...