Sharif Digital Repository

Fire is one the events which threatens the very existence of every building, residential, office, industrial or else. However, this threat is more serious with regard to buildings with steel structures. Steel, despite its many advantages over other structural materials, such as having high strength to weight ratio, ductility, toughness and resilience, has the disadvantage of rapidly losing its strength at elevated temperatures, i.e. in fire. Therefore, it is the responsibility of the designer to make the serious decision of whether to use steel, concrete, timber, or other materials for the structure of the building to be designed. Observations made during full-scale fire tests as well as... 

Past earthquakes show that irregular structures have been more vulnerable than their regular counterparts. One of the common types of irregular buildings in urban areas is split-level ones. On the other hand, beam-to-column connections in steel structures are mostly of "semi-rigid" type. In this work, effects of different levels of rigidity of connections, 100%, 75%, 50% and 25%, on the behavior of a number of two-dimensional split-level steel structures, with 1.5 m difference in levels of floors, 2, 3, 5 and 6 bays, and 5, 10 and 15 stories, were studied. All frames were analyzed “with” and “without” considering the P-∆ phenomenon, with two methods, ‘equivalent static load,’ and ‘modal... 

Abstract- Due to vulnerability of metallic structures to fire, to have an advance estimate of the behaviour and performance of the structure during fire, can greatly assist the designers to make preparations and take precautionary measures to prevent excessive damage to the building. The study of the behaviour of a structure at high temperatures can be divided into two parts, that of its members, and that of its joints. The survey of the literature reveals that most of the previous work concentrated on the former, and it seems that there has not been much work on the latter. The objective of this project was to study the behaviour of structural joints at elevated temperatures, in general,... 

The critical strain energy release rate for the solder joint fracture was measured as a function of cooling rate, time above liquidus (TAL) and soldering temperature. The specimens were prepared at 4 different levels of cooling rate, 3 varying levels of TAL, and 3 soldering temperature levels. Then, experiments were designed using the Taguchi method. Fracture tests were performed under bending at a strain rates of 10-5 and 0.5 s-1 and mode I loading conditions. It was found that the effect of soldering temperature insignificant on the Jci, but the cooling rate and the TAL due to their many effects were also studied by their interaction effects. It was observed that at the cooling rate of... 

The behaviour of a semi-rigid connection with appreciable shear deformation capacity was studied experimentally. The tests carried out on the specimens of this connection composed of ‘monotonic’ and ‘cyclic’ tests. The monotonic tests results showed the high shear deformation capacity of this connection as well as its high energy dissipation capacity. The cyclic tests, however, indicated the ability of this connection to endure large number of ‘well-rounded’ hysteresis cycles, which led to the dissipation of great amount of energy before failure  

Recent studies show that the most efficient connections are those which have more flexibility and energy dissipation capacity in addition to their strength and stiffness. While their flexibility reduce the earthquake-induced forces, their energy dissipation capacity, by dissipating some of the energy at connections, can reduce the share of structural members of the total energy that has to be dissipated, hence increasing their chance to remain intact and undamaged during an earthquake. Since conventional connections, even semi-rigid ones, have great shear rigidity, there is not any article in the literature about shear behavior of beam-to-column connections. However, due the fact that the... 

In this thesis, the shearing behaviour of a semi-rigid connection is studied experimentally. Due to high shear rigidity of existing connections, even those which demonstrate semi-rigid behaviour under bending, their shear characteristics have not been studied yet. Regarding the concerned semi-rigid connection, it was necessary to examine its behaviour under shear, experimentally. Altogether, five series of specimens were tested under shear loading. Tests on two of these series, due to fabrication deficiencies, twice had to be halted before reaching the final stage—each time the specimens were sent to the fabricator to fix the improper welds. The results of these tests clearly show the high... 

This thesis is concerned with studying several aspects of the generalized isoperimetric problems on weighted graphs. In this regard, as a generalization of well-known Cheeger constant, we define k-th isoperimetric constant as the minimum of normalized outgoing flow over all k-subpartitions (disjoint subsets) of the vertex set. Also, we investigate basic properties of these parameters and particularly we prove a Federer-Fleming-type theorem. We then introduce a generalized Cheeger conjecture which is a generalization of celebrated Cheeger inequality and relates defined isoperimetric constants to higher eigenvalues of Laplace operator. In order to find a partial proof for this conjecture, we... 

Lateral forces on structures are transferred to braces as tensile and compressive loads. These loads enter the beams and columns through the gusset plates. The gusset connections to the beams and columns must be such that they be able to pass the loads through themselves. So far, five analytical models have been proposed for this connection and only one of them is recommended by AISC. These models estimate the existing forces and moments on the connection. The analytical models are: model 1 (KISS), model 2 (2A-AISC), model 3 (Thornton), model 4 (Ricker) and model 5 (Richard). Among these models, only model 3 is recommended by AISC because the others are more conservative. It should be noted... 

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... 

To investigate the accurate performance of a structure, the knowledge of the way its connections function, is of great importance. Moreover, cognition of the actual behavior of connections which is often semi-rigid can lead to better apprehension of the actual and more accurate behavior of structures, whilst it is often considered to be pinned or fully-rigid.Therefore, in this study a new semi-rigid steel connection of beam to column will be introduced, and its behavior will be investigated using commercial finite element packages along with mathematical approximate modeling methods. One of the features of this connection is that its behavior mainly depends uponfolding of top and bottom... 

Steel structure with saddle connections constitutes a portion of the old steel structures in Iran. During past strong ground motions such as Manjil and Bam earthquakes, these structures were vulnerable and experienced significant damages. These structures were widely used due to their easy installation. However, according to their unpromising behavior, they need an appropriate lateral force-resisting system. A concrete shear wall is one of the suitable lateral force resisting systems that can improve the behavior of steel frames with saddle connections. To find the coefficients of seismic performance factors including response modification factor, overstrength factor, and deflection... 

let T4 = C2/ be a complex torus with induced flat Kähler metic. The quotient X = T4/Z2 (where the generator of Z2 acts by multiplication by −1) is an orbifold with 24 singularities, called a singular Kummer Surface. Locally any of the singularities are modelled on the singularity of C2/Z2. We can describe the minimal resolution X of X by resolving all of the singularities as : TCP1 ! C2/Z2.There is a well known Calabi–Yau metric on TCP1 named the Eguchi–Hanson metric, with the important property that far from the exceptional divisor −1(0) the metric is asymptotically locally Euclidean (ALE). We identify a small annulus around any singular point of X/Z2 with a large annulus over TCP1 far... 

Stochastic Algebraic Topology studies stochastic or less known spaces that depend on many random variables from the perspective of algebra. Examples of such spaces included random graphs of Erdos and Renyi and random simplicial spaces of higher dimension . In this thesis , we study algebraic aspects of these spaces such as homotopy groups and homology groups from probabilistic point of view , when the number of vertices of these spaces tend to infinity . The study of these spaces have a lot of applications, since the data for a given space can be incomplete . They are also used in big system structures. We have given a collection of new results in stochastic algebraic topology of two... 

The Riemann- Hilbert correspondence theorem is a higher dimensional generalization of Hilbert’s 21st problem. The main problem was about existence of differential equations with regular singularities on Riemann sphere with a specific monodromy group. Deligne generalized the problem to algebraic connections with regular singularities. Kashiwara and Mebkhout independently generalized the theorem for derived category of D-modules. In this thesis, we will begin by studying this theorem in simple cases.In chapter 3 generalized version of the theorem by Deligne,will be introduced. At the end of the third chapter a proof of Riemann-Hilbert correspondence for the special case of projective curves... 

Composite systems consisting of concrete columns and steel beams are introduces as structural systems in recent years. These structural systems enjoy merits of both steel and concrete frames by efficiently combining the advantages of them. This study is allocated to lateral force resistance system using armed concrete and structural steel. Advantages of composite structures rather to those of two other conventional ones are among performance characteristics under ultimate loads, economical conservation, and higher speed of construction.In this research the aim is to study these frame under earthquake induced loads. The seismic performances of these composite frames with through column beams,... 

After the 1994 Northridge earthquake when investigations show clear results for brittle failure near Beam-Column rigid Connections, research on these connections begun and various theories were suggested for better performance under cyclic loads. One of the appropriate ways is shifting yield beam location from beam-column connection to the beams only. Reducing the capacity of the beam through the beam flange or web far enough from the column, creating special ductile region in the beam. In this thesis, weakening is made by creating an elliptical opening in web beams. If the correct design criteria for this type of connection are suggested, it can satisfy the "weak beam - strong column" and... 

The Concept of causation plays a major role in Hume’s philosophy and as yet has been debated between philosophers. This Thesis aims to Consider the main part of Hume’s view about Causation, but it also Ventutes into more recent approaches in this subject. In first chapter, we attend to Consider The project of Hume named "Seience of man" and The associative mechanism of causation is expressed. In Second chapter, We turn to three famous interpretations of Hume’s view and the meaning of two definitions of Causation is discussed. In third chapter, we try to analyse the real nature of necessary Connection. According to fourth chapter, we again attend to three interpretations and recognize the... 

Let G be a graph. A P3-factor of graph G is a subgraph of G such that each component is isomorphic to P3. In 1985 Akiyama and Kano conjectured that every 3-connected 3-regular graph of order divisible by 3 has a P3-factor. In this thesis we conjecture that every 3-connected 4-regular graph of order divisible by 3 has a P3-factor and also show that this conjecture concludes the previous one. Moreover, we investigate connected factors and some 3-vertex induced factors in graphs and show that every r-regular graph of order n (3 j n) has a P3-induced factor, if r _> 8n/ 9-1  

Brain states analysis during consciousness is emerging research in brain-computer interface(BCI). Emotion recognition can be applied to learn brain states and stages of neural activities. Therefore, emotion recognition is crucial to the analysis of brain functioning. Electrical signals such as electroencephalogram (EEG), electrocardiogram (ECG) and functional magnetic resonance imaging(fMRI) are frequently used in emotion recognition researches. Convenience in recording, non-invasive nature and high temporal resolution are the factors that have made EEG popular in brain researches. EEG can be used to identify brain region activity solely or the connectivity of various regions in time in the...