Sharif Digital Repository

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... 

Various forms of springs are applicable, among which spiral and leaf springs can be named. Definition of leaf springs is conventionally applied to constant-width springs and is consisted of step-like leaves, each leaf having constant width. Leaf springs are largely used in vehicles, where they act as a part of suspension system supporting the weight of the vehicle along with connecting spots axles to the chassis. Springs so installed are capable of handling starting and stopping torques as well as sudden vibrations due to load carrying. Most Conventional method of manufacturing leaf springs is to bend strips of appropriate steel between curved dies, quench the strip while held between the... 

In sliding wear, the process of making debris takes place with different mechanisms. Previous works estimating the wear rate have been carried out based on contact mechanics and material failure mechanisms. In present work, the possibility of existence of low-cycle fatigue as the dominant mechanism in the wear of an as-cast eutectoid steel is investigated. Moreover, wear coefficient and the the volume loss per distance of that steel was predicted. At first, wear tests were done in order to obtain the wear trend of the steel in different loads. Then, regarding the roughness of the disk surface, a finite element model was built to simulate the sliding of the pin surface over the asperities... 

Structural Health Monitoring (SHM) is a multidisciplinary emerging research field. SHM assesses the health state of the structure through processing and interpreting of signals and can predict remain life of the structure. Damage detection with Piezoelectric Wafer Active Sensors (PWAS) is one of the effective and emerging methods of SHM. One of the most critical parts of aerial structures is lap joints in which SHM could be very effective. In this research, damage detection of lap joints using lamb wave propagation has been studied. A 3D model of an aluminum lap joint presented. The PWAS are modeled separately and bonded to the host structure and coupled electromechanically with the... 

Health monitoring of historic structures because of their cultural and economic importance is of great interest; also modeling and investigating the behavior of these structures is needed in rehabilitation procedures. Soltaniye Dome is one of the important masterpieces of Persian-Islamic historic architecture which is constructed during 14th century (1302-1312 AD). The Soltaniye building has an octagonal framework and a great dome. The dome has a diameter of 25 meters and total height of structure is about 54 meters.In this study, the macro modeling of Soltaniye building is performed using finite element software. In order to verify the modeled structure, ambient vibration tests are... 

Existing design methods for steel frames has been improved over the last three decades in order to incorporate the behavior of semi-rigid steel connections in furtherance of frame design and since the analysis and design of structures is often done based on the assumption of completely rigid or pinned behavior,therefore, the actual behavior of connections and their modeling can help to understand the actual behavior of structures.Knowledge of the initial rotational stiffness of the connection is important for elastic analysis of structures. Investigations show that structures with semi-rigid connections have many features which are the causes to prefer these kinds of connections to the... 

Thermal analysis of concrete arch dams is always an important issue in designig these enormous concrete structures. The reason this issue mainly concerns arch dams and not gravity dams is because of little thickness of arch dams which makes them prone to cracking due to thermal loading. To solve any thermal problem we need boundary conditions. In arch dam case, these boundaries are the temperature of the upstream and downstream face of the dam which, depending on circumstances, can be in touch with water or air. Estimating air temperature is a fairly easy task when you have monthly mean temperatures. The challenging part is defining water temperature in any depth of the reservoir whenever we... 

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... 

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... 

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.... 

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... 

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...