Sharif Digital Repository

Elevated water tanks are one of the most critical elements in civilized society to provide safe servicing resources of drinking water after natural and human-made disasters. Dynamic analysis plays a vital role in investigating structural behavior of the elevated storage system subjected to the earthquake-induced vibration. The main scope of this paper is to address the structural stability analysis of the Kish Island’s elevated reinforced concrete water tank employing finite element method. A complete solid model of the structure with detailed design was constructed, and finite element analysis was carried out utilizing ABAQUS software. To investigate the dynamic behavior of the structure, a... 

The injection process on cell is a very accurate and sensitive operation. This method is used for several new invented approaches such as tracytoplasmic Cell Injection or drug delivery. Controlling the injection force in micro scale is one of the problems of mentioned operations. Current huge and expensive laboratorial devices are helping the operators to do injection operation with :nore success. In this study a simple and novel microelectromechanical (MEMS) mechanism for doing injection process automatically on the biological cells is proposed. In order to controlling this device properly, we should model and simulate the operation condition from initial position to final condition. This... 

In recent decades, metal nanoparticles have been used in medicine for example in cancer treatment. There have always been debates on the nanoparticles specifications such as particle size, amount of surface charge and the particle material. Meanwhile, the study on selecting appropriate properties of nanoparticles for this purpose is very essential and expensive in medical science. In order to access the best efficiency and the least mortality of the patients in treatments, simulation studies can support the medical scientists. In this thesis, the goal is to study transferring nanoparticles as a drug or included drugs through created hypothetical micro-channels in cancerous cells membrane.... 

Most engineering components must be manufactured so they are safe to use and are ‘‘fit for purpose’’. However despite all the efforts, cracking of the engineering components is inevitable. Residual stresses play an important role in either increasing or decreasing the possibility of failure. For instance, enhancement in apparent toughness following pre-loading arises principally because of the creation of local crack tip compressive residual stresses. Introducing compressive residual stresses can also slow the fatigue crack growth. Yet, the dilemma is choosing an efficient method growth to introduce such stresses for retardation of fatigue crack growth. There are many methods available in... 

During the past two decades, laminated composite structures have been used for many engineering applications, including aerospace, automotive, sport equipment and pressure vessels.
In spite of the excellent properties of strength to weight ratio, composite structures are vulnerable to failure when subjected to impact and vibration. It is well known that impact damage may severely degrade the strength and stability of laminated composite structures. For this reason the effect of impact on composites has been a subject of extensive research.
There are several ways of decreasing the vibration energy of structures, such as diminishing the source energy, designing structures... 

Residual stresses are stress fields that exist in the absence of any external loads. All mechanical processes can cause deformation that may lead to residual stresses. It is well established that virtually no material, no component and no structure of technical importance exists free of residual stresses. However, in practice, the knowledge of the true distribution of exiting residual stress is rare. The residual stress fields are very challenging to evaluate, independent of the measurement techniques. The important aspect about the residual stress determination is that often true distribution is unknown in the engineering specimen. A simple and non-destructive method to measure residual... 

A heat exchanger is a piece of equipment is built for efficient heat transfer from one medium to another. They are widely used in air conditioning, chemical plants and petrochemical plants, so studying the different failures and problems of them is important.
One of the common problems is fracturing of the tubes. This will allow the hot water to enters them and then hit the refractory of the tubesheet. This coating slowly washing away and that will lead to direct contact between the hot fluid and the tubesheet. Tubesheet is not designed for such a hot thermal load so cracks will initiate on it due to this new situation. They will shut the fractured tube by shut it down and welding a... 

In this paper, a finite element formulation is presented to study the thermoelastic behavior of Functionally Graded (FG) axisymmetric coating in shell structures. The power law distribution model is assumed for the composition of the constituent materials in thickness direction. The Plasma Spray with multi steps coating method is considered for coating method. The procedure adopted to derive the finite element formulation contains the analytical through-the-thickness integration inherently. So the explicit through-the-thickness integration becomes possible after defining a two-noded, three parameters degenerated axisymmetric FG element. The nonlinear heat transfer equation is used for... 

Photostrictive type of opto-thermo-electro-mechanical materials, called PbLaZrTi (PLZT), are a recently emerged family of smart materials, that are able to generate strains under illumination of near violet light and attract much attention in a variety of wireless and remote control applicati-ons, including the areas of material science and engineering, micro-electro-mechanical system (MEMS) and Optical MEMS, and smart structures. This research presents an analytical and finite element investigation into ultraviolet photo-induced multi-physics responses of 0-3 polarized PLZT photocantilever and a comparison of the measured bending displacement. The finite element formulation of the... 

Structures that change shapes are often called morphing structures. Smart morphing composites refer to the morphing structures that can detect the change in conditions and, through a control mechanism, command the actuators to maintain the stability and/or perform a new task. The present report provides a framework on the eld of smart morphing composite structures. The emphasis on this work is on, particularly, multi-stable composite structures with capability to detect the new conditions and adapt themselves to properly respond to them. Due to cycling nature of applied load on morphing, these structures are vulnerable to failure due to fatigue. A failure control mechanism utilizing a... 

Minimally Invasive Surgery (MIS) is a modern surgical technique in which the operation is performed through small incisions in the body. Therefore, the surgeon looses his/her sense of touch which is of high importance in any medical operation. In the present work, a novel smart grasper is presented in which the surgeon can virtually acquire a feeling of force/momentum experienced by the organ/tissue. The smart grasper uses piezoelectric sensors bonded at desired locations to detect the applied force/momentum applied by surgeon and to measure the transmitted force/momentum to the tissue/organ. First, an accurate electro-mechanical model of the smart grasper is developed and the relations... 

Neural prostheses (NPs) based on capacitive coupling method including sur-face NPs, implanted or subcutaneous NPs and Stimulus Route System (SRS) are the common NPs used for rehabilitation applications. SRS is a kind of capacitive coupling and the latest version of the mentioned neural prosthesis used for restoring sensory and motor functions caused by spinal cord and brain disorders. In addition to some superiorities of capacitive coupling compared to other methods (inductive coupling, batteries, energy harvesters and so on) such as at plates structure and consequently ease of manufacturing, ability to transfer data and power with different operating frequency and hence remov-ing... 

Bridges play a vital role in road-related transport industries. Significant changes to contemporary bridge design specifications have also been mainly related to strength issues. The transitions from allowable stress design to load factor design, and more recently to load and resistance factor design (LRFD), reflect this line of thinking. It is important to note that in the early 1970s, bridge engineers developed criteria for steel bridge details to protect against fatigue and fracture failure. These were indeed service life design provisions. By industry growth and extensive need for goods transportation, there is a need for the construction of new bridges and renewal of older bridges plus... 

Despite extensive studies on the behavior of reinforced concrete slabs, especially those reinforced with steel rebars, no comprehensive studies have been conducted on the behavior of concrete slabs reinforced with FRP rebars. Therefore, there are some ambiguities regarding the tensile and compressive behavior of these rebars in the load-bearing capacity of reinforced concrete slabs (depending on their amount in the slab and their combination with steel rebars). Hence, in this study, in order to ensure the accuracy of numerical simulations, the numerical 3D simulation of a one-way concrete slab reinforced with tensile FRP rebars was performed using the finite element Abaqus software.... 

In this study, a pioneer multiscale hierarchical molecular dynamics (MD) – finite element (FE) coupling method is proposed to illustrate the influence of large deformation on mechanical properties of heterogeneous nano-crystalline structures. The embedded-atom method (EAM) of many-body interatomic potential is applied to evaluate pairwise interactions between atoms in the metallic alloys with face-centered-cubic (FCC) lattice structure at room temperature. In addition, the Nose-Hoover thermostat is used to control the instability of temperature. A weight average between the lattice parameters of atomic structures is utilized in order to calculate the equivalent lattice parameter. The... 

The increased height of high-rise structures has made the effects of reduced stability a crucial factor in structural analysis and design. There are a variety of methods for analyzing the stability of high-rise structures. This thesis discusses nonlinear finite element method for analyzing the stability of a three-dimensional 50-storey concrete structure with a height of 150 meter using increment dynamic analysis (IDA). The IDA was first proposed by Bertero.v and it has been adopted in a variety of manners by researchers. In recent years, this method has been confirmed by EEMA. Moreover, FEMA350, FEMA351 and FEMA P695 guidelines have paid special attention to this method for determining... 

Since the main weight of structures comes from the weight of floor systems, it is desirable to use tin and light floor system in order to reduce gravity and seismic force induced in the structure. However architectural aspects limit the application of short spans in the structural system. The objective of this work was to analyze the adequacy of a design method widely used in the modeling of waffle slabs interaction with steel columns as its supports in steel frames, and to verify if it represents the slab behavior satisfactorily. A real scale waffle slab was laid on a steel column and submitted to service loads. Subsequently it was analyzed with FE method for measuring specific stress,... 

Building weight reducing idea and implementation of Lightweight Structures were always attractive for structural engineering experts, scholars and researchers around the world and its proven effects on improving behavior and reducing the forces acting on the structure, has urged researchers to create new designs. Concrete slabs are of a significant portion of the overall weight of the structure. Nowadays, waffle slabs are a demand for structural designers, as a consequence of architectural design evolution and new building management concepts, in spite of its laborious numerical modeling. The objective of this work was to analyze the adequacy of a design method widely used in the modeling of... 

Concrete Filled Polyvinyl Chloride (PVC) Tube (CFCT) technique has attracted significant research attention in recent years. PVC offers a number of advantages such as low costs and excellent properties like 1- high electrical insulation; 2- high resistance for abrasion; 3- low diffusion for humidity; 4- remarkable resistance to water, bases, acids, alcohols, oils; 5- large elongation at break; 6- low creep deformation; 7- workability including (cutting); 8- consistency; and 9- excellent corrosion resistant, durability and mechanical stability. The PVC tube acts as a longitudinal and transverse reinforcement and serves as a formwork which simplifies construction and reduces erection time. The... 

In this study, a modern multiscale sequential molecular dynamics (MD) – finite element (FE) coupling method is proposed to represent the role of grain boundary (GB) planar defect on mechanical properties of crystalline structures at various temperatures. Different Grain Boundary misorientation angle is considered and the temperature varies from 0 up to 800 K. The embedded-atom method (EAM) many-body interatomic potential is implemented to consider pairwise interactions between atoms in the crystalline structures with face-centered-cubic (FCC) lattice structure at different temperatures. In addition, the Nose-Hoover thermostat is employed to adjust the fluctuation of temperature. The atomic...