Sharif Digital Repository

Iran plateau is situated over the Alpide-Himalaya earthquake belt. Tectonic studies indicate that this plateau has a very high density of active and recent faults; as a result, Iran is at risk of damaging earthquakes. Experience of past severe earthquakes shows previous designed structures do not have enough strength instead of real earthquake forces, therefore vulnerability study of existing structures and give a technical and economical retrofitting plan of them is required. Conventional methods of seismic rehabilitation for example using concrete shear walls or steel braces are not suitable for some buildings. Nowadays, passive control systems have been successfully used for reducing the... 

The Machinable Austempered Ductile Iron (MADI), a new group of Austempered Ductile Iron (ADI), has been developed to remove the problems (hardness and cost) of ADI cast iron. MADI is a special kind of ductile iron which has proper machinabilty properties. This kind of ductile iron can be produced using a specific chemical composition and defined heat treatment process. By providing these conditions, the hardness of the cast iron will be in the range of as-cast cast iron. On the other hand, because of the especial production process, the cost of the final shape casting will be lower than ADI cast iron. In the present work, firstly the effect of heat treatment parameters, including the time... 

Since its discovery in 1943, the use of ductile iron is increasing continuously, this is due to the combination of various excellent mechanical properties. Excessive amount of research has being carried out to improve the properties. Austempererd ductile iron is the most recent development in this field. The application of this material included to automobile, railway, military, agricultural, mining & construction industries. The newly developed austempered ductile iron is now replacing steel in many fields so it has become very important to various aspects of this material. In this thesis, the effect of alloying elements (copper & nickel) and the austempering process variables on the... 

Increasing emissions of greenhouse gases from one hand and decline in the fossile resources of energy on the other hand has raised the motivation of searching for renewable sources. Biodiesel, because of having perfect feature for replacing with petroleum diesel, has been considered as candidate for this purpose. Using enzymatic reaction is one of the methods for biodiesel production. Understanding the kinetics of this reaction is important to achieve higher production rates. In present work, the kinetic of transesterification of castor oil with use of Novozyme 435 (as enzyme) was investigated. Enzymatic biodiesel production is a bi-substrate (oil and alcohol) reaction. Genetic algorithm was... 

Iran requires basic changes in using construction materials and industrial system of house production due to its particular climatic conditions such as being located on the earthquake belt and social conditions such as lack of house. 3D panel is one of the best options for industrial construction and especially mass building.
In this thesis, different suggested designs for L & T shaped wall to wall connections of 3D panel under lateral-cyclic and gravity loading were modeled and analyzed by ANSYS software. Numerical analysis indicates that concrete perpendicular hank and welded wire mesh WWF 3/3/50/50 have positive effect on the ultimate strength and ductility of the connection. Hence,... 

Controlling the structures under seismic excitations is a great challenge in the earthquake engineering. In this regard, bracing systems have been presented and applied to provide additional rigidity for the structures. However, conventional bracing systems are buckled under compressive forces. In this research ribbed bracing system (RBS) is proposed to deal with the buckling problem of conventional bracings. Full capacity of RBS is used under cyclic loading. Ribbed bracing system is constructed by adding a supplement part with a ribbed mechanism to the conventional bracing systems. As the supplement part is locked when the bracing is under tensile forces, the bracing system can absorb... 

In this study, the nano-scale deformation mechanism of cementite was investigated with aid of Molecular dynamics (MD) simulation using MEAM potential. For this purpose, flow localization was evaluated in various structures such as single crystal cementite, nanocrystalline (NC) cementite, and lamellar cementite at various temperatures and different stress conditions. In order to understand the deformation mechanism in the cementite single crystal, two cylindrical samples with 15 nm length and 5 nm diameter oriented along [001] and [011] were constructed. The result of tensile test simulation at 100 K, 300 K, 700 K and 1100 K revealed that the deformation mechanism in single crystal cementite... 

In this thesis different steel plate shear walls have been investigated using ABAQUS software. These investigations have been focused on various topics, including both boundary frame elements and also the in-fill plate. The main results have been gathered by utilizing different steel plate thicknesses and different boundary frame elements. In order to achieve a better understanding of the effects of both of these elements, various aspect ratios have also been investigated. Moment of inertia has been noted as the main property of both beams and columns used in SPSW. Comparison of the gained results is noteworthy. They show a variety of changes in the load-displacement diagrams, due to changes... 

The current work is carried out to characterize welding of AISI 304 Austenitic Stainless Steel to Ductile Cast Iron. The welding method was SMAW and the welds were produced using a Nickel-Buttering by a pure Nickel electrode(ENi1) on Cast Iron side, then by 4 types of filler materials the joints were produced; Ni-base electrode(Ni1), E308 and E309 Austenitic stainless steel electrodes and E7018 electrode. The preheat temperature of Cast Iron has been selected to be 250○ and 500 ○C to avoid crack of weldments. The comparative evaluation was based on metallography, chemical composition, hardness and corrosion behavior on two different preheat temperatures. According to metallography, the best... 

In this research, two-layered sheets of copper and stainless steel 316 were produced by roll bonding. These sheets provide a combination of properties of copper and stainless steel; including high strength, thermal conductivity and corrosion resistance, as well as low weight and cost-efficient means of production. The effects of thickness reduction, different preheat temperatures and varying heating conditions after rolling on bond strength were studied. In some specimens, an aluminum sheet was used as a middle-layer, which significantly improved the bonding quality. In order to observe the interface of the bonded specimens, optical microscope images of the cross sections were studied.... 

In the present study the production of ferrite-martensite dual-phase (DP) Steel was investigated during the bonding process by transient liquid phase method. The effect of martensite morphologies on mechanical properties of bonding zone were also studied. To make the bonding process and DP steel production heat treatment cycle simultaneously, the step in which the isothermal solidification completed, bonding process, was done simultaneously with austenitising of the steel. Homogenizing of the bond zone, was also done with DP steel making at the intercritical temperature. The St52 steel was utilized for producing DP steel and for bonding process, iron base interlayer with melting point of... 

Grillage structures are used at roofs of some buildings and community halls and shopping centers and airports, or structures that used as bowers. The grillages is constructed with steel or concrete beams. In most of the carried out Researchs the twisting effect on these structures has been ignored. In this research the behavior of such structures with considering regulation and softwares limits by some simple programable assumptions is simulated. So with using MATLAB software a program extracted for grillages nonlinear analysis and its results was compared with common engineering software. In This approach in addition to pure bending, bending – torsion interaction is considered too and I... 

Recent earthquakes indicate the importance of retrofitting existing structures to achieve an acceptable level of performance. Use of bracing systems is a cost-effective method for seismic retrofitting of existing steel frames. In particular, Buckling Restrained Braces (BRBs) and Special Concentrically Bracing systems (SCB) are practical choices to be used because of their large energy dissipation capacity especially under moderate to severe earthquakes. Buckling restrained braces which yield in both tension and compression, exhibits stable and predictable hysteretic behavior. In this study several existing steel frames, which are designed based on older versions of the building codes, have... 

In the present study it was intended to evaluate the seismic performance of multi-story EBF structures for designing. When adopting this method, parametric studies are carried out based on the nonlinear performance of such systems whiting the framework of nonlinear static and dynamic analyses. In lines with seismic strengthening of such structures, this study tries to reassess the performance of these systems through increasing ductility and replacing bracing frames with energy damper and special seismic systems. As a result, a fuse type performance is created to protect the other elements of the structure. This study describes the seismic strengthening of this type of dampers using simple... 

In this study, the behavior of diagonally stiffened steel plate shear wall systems which have a new configuration of stiffeners is investigated. This dissertation is divided into three main sections which contain experimental studies, finite element analysis and developing design equations. In the section on experimental studies, 5 single-bay, single-story, one-third scale specimens were tested. An unstiffened specimen as a control sample and two other specimens with different configuration of stiffeners were constructed and tested to study the effect of diagonal stiffeners. Based on the observations during the tests, it was decided to add and study two other specimens too, including one... 

One of the most important connections in a structure is the column base plate connection. In structures subjected to earthquake loading, this connection is usually where a plastic hinge can develop and therefore is of utmost importance. In this paper, behavior of base plates under monotonic and cyclic loading is investigated. The failure modes, that are one of the fundamental targets in this study include base plate yielding, anchor bolt yielding and also failure arising due to crushing of concrete. A parametric study is conducted using nonlinear finite element analysis. Parametes such as plate thickness, anchor bolt size and location and concrete strength are considered. The desired... 

Bulk metallic glasses (BMGs), in contrast to conventional crystalline materials, are defined as metals with an amorphous and disordered atomic-scale structure. Due to the absence of dislocations and grain boundaries, BMGs have considerably unique mechanical properties such as high strength and elastic strain, high wear resistance and desirable corrosion resistance. However, they generally suffer from poor plasticity caused by an inhomogeneous deformation which leads to catastrophic failure by localization of strain into narrow regions, known as shear bands. This factor has extremely restricted their application as advanced structural materials. Furthermore, the recently discovered phenomenon... 

In this study, the flexural behavior of simple concrete beams with rectangular section (depth 20cm and width 18 cm) reinforced with perforated steel plates is evaluated. Perforated steel plates are used as an alternative for steel bars in the tension region. Because of special geometry, these plates are more integrated with surrounding concrete as compared with steel rebars. The holes in the plates caused local confinement on the surrounding concrete. Concrete beams are modeled with different number of perforated steel plates (one or two or four layer) in Abaqus software. Also beams with different patch lengths are modeled to evaluate patch length of perforated steel plates. Results of... 

Every year, fracture imposes high economic costs and casualties to all societies. Since the beginning of the twentieth century, scientific approach to this issue has lead to invention of a new branch in mechanics, called fracture mechanics. In general, fracture problems fall into two categories. Brittle fracture, like what happens in glass, in which, few plastic deformations and energy absorption occurs and ductile fracture, which is preceded by large plastic deformations and energy absorption. This kind of fracture is usual in ductile metals like low carbon steel. Finite Element which is considered as the most important numerical method in the mechanics of materials, is also, widely used in... 

In this thesis, based on the combination of Extended Finite Element Method (X-FEM) and appropriate material constitutive models, an efficient method is proposed to model ductile fracture under quasi-static, cyclic and dynamic conditions. X-FEM is a novel method in which with the use of appropriate enrichment functions, discontinuity geometry is separated from the computational mesh and hence the need for a remeshing step is alleviated. The non-linear material behavior in the crack tip process zone can best be modeled with methods based on continuum damage mechanics. These methods model the ductile fracture mechanisms, phenomenologically. In this thesis, in order to model the ductile...