Sharif Digital Repository

In this research, an innovative system, called ribbed bracing system (RBS), proposed to deal with poor performance and deficiency of brace buckling under compression loads. RBS is an additional component added to common brace system which prevents the buckling problem of conventional bracing systems. By applying tensile load, the ribs lock together and the system starts enduring tension. Since the compressive force begins, ribs slide on each other and the system endures only a trivial force. Two kinds of RBS mechanism are introduced: completely-closed RBS (CC-RBS) and self-centering RBS (SC-RBS). In the former mechanism, the length of the brace is reduced by applying compression loads; while... 

Statistical studies indicate the fact that in Iran, like many other developing countries, a considerable percentage of houses are in the form of traditional buildings, and major losses due to recent earthquakes are because of masonry building collapse. In the early twentieth century in Iran every ten years a destructive earthquake has been occurred which has resulted in huge human casualties and economic losses. After the Bam 2003 earthquake, a team project was defined to investigate the behavior of rural houses with the aim of providing solutions to lessen seismic hazards, and the current study is the fifth phase of the following line of investigations. Among the existing kinds of rural... 

Ground vibration during pile driving is one the most important factors that limits usage of this kind of piles. It is of great importance to estimate the level of vibration prior to the beginning of pile driving to avoid structural damage or disturbance of building occupants. In this study, an axisymmetric finite element model that utilises an adaptive meshing algorithm has been introduced, using the commercial code ABAQUS, to simulate the full penetration of a pile from the ground surface to the desired depth by applying successive hammer impacts. The model has been verified by comparing the computed particles velocity with those measured in the field. The results indicate that the peak... 

After the heart-rending earthquake in Bam and its severe losses, the engineering community forced to pay special attention to the seismic vulnerability of traditional structures. Therefore, with the aim of reducing of such devastations to minimum, a multi-phase research project was defined at Sharif University of Technology to study the vulnerability and retrofitting of these structures which the current study is the eighth phase of that series research. In the third and fourth phases of this project, a typical adobe building with dome roof was chosen for study making use of shaking table facilities. The tests included both un-retrofitted and retrofitted states and considerable seismic... 

The main purpose in this thesis is the finite element simulation of the stress-strain behavior in an aluminum-silicon-magnesium alloy, subjected to low cycle fatigue and thermo-mechanical fatigue loadings. This finite element modeling is performed in the ABAQUS software. Two time-dependent and time-independent models are used to simulate the behavior of the material. The time-independent model is the combined nonlinear isotropic/kinematic hardening model, which predicts the mean stress relaxation behavior, the cyclic softening or hardening and the translation of the yield surface, while it ignores the effect of the strain rate. Time-dependent models include Johnson-Cook and the two-layer... 

In designing sheet forming processes, finding out the value of the maximum strain before necking in sheets is extremely important. Therefore, many experimental and theoretical efforts have been carried out in order to answer this question. One of the most well-known and useful theoretical methods in this regard is the Marciniak - Kuczynski method which was introduced in 1967 and is still the topic of many researches. In this model, it is assumed that a groove as a defect primarily exists in the sheet and due to the weakness of this region, necking will initiate. Furthermore, the effects of various parameters such as sensitivity to strain rate, strain path, thickness, three dimensional... 

The ossicular chain of the human middle ear has a key role in sound conduction since it transfers vibrations from the tympanic membrane to the cochlea, connecting the outer and the inner part of the hearing organ. This study reports firstly a description of the main anatomical features of the middle ear to introduce a detailed survey of its biomechanics,focused on model development, with a collection of geometric, inertial and mechanical/material parameters. The joint issues are particularly discussed from the perspective of developing a model of the middle ear both explanatory and predictive. Such a survey underlines the remarkable dispersion of ... 

Oil field industry is one of the most challenging engineering subjects. In oil well drilling, undesired motion could raise a lot of problems such as stuck pipes; wash out pipe, and etc. In this industry, motion prediction is very important because a good prediction can avoid instruments failure and as a result considerable amount of time could be saved. Predicting dynamic characteristics of drill-string such as whirl orbit, whirl speed, and axial, lateral, and torsional displacements, accelerations, and velocities, might be useful in avoiding or decreasing failures. A program based on FEM (Finite Element Method) is developed in MATLAB considering deviation of drill-string, contacting with... 

In this study, three dimensional analysis of soil slopes subjected to dynamic loading was conducted in order to investigate the interaction of soil-pipe system. For modeling of soil behavior, strain-dependent nonlinear elasticity along with Mohr-Coulomb plasticity was defined to the material and elasto-plastic behavior was used for the pipes. For dynamic modeling of soil slopes and analysis of buried pipelines, a Finite-Element-based software, ABAQUS was utilized. In this regard, first the numerical model was calibrated and verified based on the results obtained by physical shaking-table tests on a soil slope. Afterwards, a comparison was made between the results of numerical models and some... 

Nowadays, proper design and retrofitting of structures against natural and manmade disasters, is among the main concerns of researchers and designers in order to reduce financial and human costs. Extensive research has been carried out on the structures resistance against earthquake up to now. Although, the vast amount of research has resulted various regulations and guidelines, there is still a long way ahead to achieve the desirable results. Due to high sensitivity of the steel to temperature variations, fire exposure is more destructive for steel structures compared with the concrete ones. The performance of an intermediate three-storey steel moment frame with 4 spans was studied in this... 

In this study, the seismic response analysis of a buried pipeline had been performed using three-dimensional (3D) dynamic analysis of the soil-pipeline interaction under different loading inputs. A number of parameters such as properties of the buried pipeline including diameter and internal pressure and different loading frequencies were used for this investigation. The pipe was considered as an elastoplastic material and a nonlinear elastic material based on the Mohr–Coulomb criterion was used to model the soil behavior. In addition, pipe-soil interaction has been studied in both tangential and vertical directions. The ABAQUS software was utilized for the 3D numerical modeling and... 

This project deals with the global buckling in high pressure/high temperature (HP/HT) subsea pipelines. Some subsea pipelines are laid directly on the seabed. Large axial forces will generally cause an exposed pipeline to buckle sideways, or laterally, on the seabed. Pipelines may significantly expand during start-up and shutdown cycles, resulting in global buckle formation with high out-of-straightness (OOS).This global buckling behavior may be unacceptable if it is not properly managed. Global buckling mitigation can be achieved by providing controlled lateral movements of pipeline. Buckle mitigation devices are installed along the pipeline to provide buckle initiation sites, there by... 

The purpose of this research is to study the effect of using expanded polystyrene (EPS) Geofoam to retrofit buried pipelines in slopes subjected to landslide due to earthquakes.For this purpose, several 3D numerical models were built with ABAQUS/CAE based on physical model tests conducted on shaking table device at Sharif University of Technology by previous research groups. Two parts are considered in this study. in the first part, three tests were simulated. Displacements, acceleration time histories and strains of pipes were compared to the tests results and the effect od EPS block on each pipe pesponse was observed. In the second part, effect of two factors on response of buried pipes... 

One of the lateral-load bearing systems that has been recommended since almost 40 years ago is the steel plate shear wall (SPSW) system, which consists of a steel plate surrounded by beams and columns in each story. As for the performance of SPSWs, it is assumed that the boundary members of the wall’s plate, i.e. beams and columns, have sufficient stiffness and strength, so that they would not yield by the tensile stresses exerted due to the post-buckling behavior of the plate (tension field); and the global stability of the structure is still maintained. This assumption leads to significantly increased dimensions of the sections applied in the wall’s boundary members, particularly its... 

There is many operational problems in the drilling industry. One of these basic problems is stuck pipe. This problem occurs with different intensities in different formations due to particles falling into the well, pressure difference in the formation and drilling mud and instability of the wellbore and creates conditions in which the drilling string can neither rotate nor move, so all Drilling operations are stopped so that according to studies, pipe sticking is one of the most important reasons for stopping drilling operations. This stop imposes millions of dollars of operational damage on oil services companies annually. Therefore, identifying and prediction of stuck pipe as a major... 

The purpose of drilling is to create a safe path to access underground hydrocarbon resources. Therefore, during drilling operations, barriers should be considered to ensure the safety of the well. When drilling a well, if for some reason, brine, gas or oil enter the well, the pressure of the mud column decreases, which will continue to collapse the stability and integrity of the well. In this case, the external fluid may reach the wellhead and blowout. For this reason, blowout preventers should be installed at the wellhead to secure the well with high confidence by closing the valves and preparing for the continuation of the drilling process. Well blowout may lead to loss of personnel lives,... 

Using mixed building system of structural steel and reinforced concrete improves the resistance of the structure in comparison with using either material alone. Coupled shear walls is one of these new systems. Coupled shear walls by definition is a series of walls coupled by beams as a central core structure with opening to accommodate doors, elevator wells, windows and corridors. Coupled shear walls can provide an efficient structural system to resist horizontal force due to axial and seismic loads. One type of coupled beams is Steel Coupling Beams (SCB) which consists of steel beams and reinforced concrete shear walls which represents a cost and time-effective type of construction. Some... 

Tunnel form structures have been proposed in building industry during 40 years for financial saving, suitable structural performance and seismic behavior, and the possibility of performance in an industrial form; and they have also been brought up as one of the innovative technologies of construction in Iran for a couple of years. So far, these structures have been subject to study by the researchers less than frame structures. In comparison to the common structures, evaluating the behavior of these structures is analyzable as two or three-dimensional elements. In this research, the nonlinear behavior of these structures has been simulated and evaluated by using three-dimensional elements;... 

The purpose of presented thesis, is modeling of the buried pipelines in soil slopes under dynamic loading using experiments on the physical model. Hence, numerical models based on five physical models, which are built and experimented on Sharif University of Technology’s shaking table device, have been analyzed using ABAQUS finite element software. In each model, several pipes are buried in slope, and the angle-wise placement of pipes differs with respect to slope slide. For the purposes of modeling, the experiment box has been modeled as rigid body. In order to model the soil behavior, Strain –dependent nonlinear elasticity, and mohr-coulomb criterion, has been employed. In addition,...