Sharif Digital Repository

Actin filaments are the most abundant component of the cellular cytoskeleton and provide shape for the most eukaryotic cells. Actin constitutes 1-10% of the total protein in most cells and is present at even higher concentrations in muscle cells. The functions of actin are directly connected to its mechanical properties, therefore both experimental and computational understanding of the mechanical properties of actin filaments are essential to elucidate their functions in cells and muscles. Actin exists in two forms, actin monomers (G-actin) and actin filaments (F-actin), which have continuous polymerization and depolymerization processes. In the polymerization process, different... 

The main goal of this research is to evaluate the vertical and slant bolted endplate connections performance in steel moment frame structures under thermal effect in elastic range for two cases. In the first case, frictionless and in the second case slips with friction are considered. By finite element analysis, the connections are simulated to study the performance and verify simplified models of vertical and slant bolted endplate connections due to increase in temperature. The results of a vertical bolted endplate connection and a slant bolted endplate connection due to increase in temperature are compared the effect of slope of end plate reduction of axial force on beam is investigated.... 

Design of thick-walled spherical and cylindrical vessels as fluids containers of high gradient thermal loading is a challenging issue. Using these tanks in high pressure and temperature gradient, particularly in chemical industries, needs to use new methods in design. Elasto-Plastic solution for thick-walled hollow spherical and cylindrical tanks made of FG materials subjected to internal pressure and temperature loading is presented. The power law modeling is used for through-the-thickness variation of mechanical properties. This method is using the new advanced materials with high pressure and thermal strength in fabricating these vessels. One of these materials is functionally graded (FG)... 

The fiber-reinforced composite materials are used widely because of their high strength-to-density and stiffness-to-density ratios. The laminated composites are susceptible to delamination. When a delaminated composite plate is subjected to in-plane compression, buckling in the delaminated region may occur. In this thesis, after verification and validation of the models, the effect of the length of the longest and near surface delamination and beneath delaminations on critical buckling load of composite laminates are investigated. Numerical study is carried out to determine the buckling load of clamped composite plates with different symmetric and anti symmetric stacking sequences. The... 

This thesis investigates the performance of concentrically braced frames through numerical simulation approaches. During a moderate to severe earthquake, the bracing members and their connections are expected to undergo significant inelastic deformations into the post-buckling range. Recently, provisions for special concentrically braced frames (SCBFs) were developed to exhibit stable and ductile behavior in the event of a major earthquake. Special Concentrically Braced Frames (SCBFs) are distinguished from Ordinary Braced Frames in that they possess improved post-buckling capacity. Performance based evaluation of SCBF system as well as ordinary concentrically braced frame (OCBF) system... 

The use of unbonded post-tensioned precast concrete walls with horizontal joints as the primary lateral load resisting system in seismic zones has been considered in several previous studies. These walls are constructed by post-tensioning precast wall panels across horizontal joints using post-tensioning steel which is not bonded to the concrete. The behavior of the unbounded post-tensioned precast structural wall under lateral loads strongly depends on base panel geometry and concrete confinement properties. In this research an analytical parametric investigation on base panel design parameters is conducted using DRAIN-2DX software. Fiber beam-column elements are used to represent the... 

This study deals with the monotonic behavior of reinforced concrete membranes. In the first step, small reinforced concrete membrane panels were studied. Examining the available test results on reinforced concrete panels, a new set of stress-strain relations for normal strength concrete and mild steel bars embedded in concrete. The salient features of the proposed constitutive laws are: 1) considering the effect of reinforcement ratio on average stress-strain relationships of cracked concrete; and 2) considering the gradual reduction of average stiffness of steel bars embedded in concrete. Equilibrium, compatibility, and constitutive relationships were incorporated into an algorithm to... 

In this thesis the performance of anew energy dissipative device, slit steel damper (SSD) is investigated. The slit steel damper is manufactured with I-shaped, wide flange H-shaped profiles with a number of slits cut from the web. The device is installed between beam and chevron brace and fastened by four bolts on each side, which enables the replacement of the device due to strong earthquake.A numerical study is conducted to studythe nonlinear behavior of the SSD systems by using a nonlinear FE program. It is found that the numerical modeling results have a good agreement with the existing test results.In the next step a parametric study is performed to study the effects of the number of... 

Density matrix of graphs as defined -for the first time- in [S. Braunstein and et al. The laplacian of a graph as a density matrix, Annals of Combinatorics, (2006)], is obtained through dividing the Laplacian matrix by the degree sum. This matrix is also semi-positive and trace one. Therefore one may talk about the Von Neumann entropy of this matrix. In [F. Passerini, S. Severini. Quantifying complexity in networks: The Von Neumann entropy. IJATS, (2009)], authors have claimed that this quantity can be consisered as a measure of regularity. Here, using a geometric interpretation of Von Neumann entropy, expresed in [G. Mitchison, R. Jozsa, Towards a geometrical interpretation of quantum... 

Cold-formed steel sections are lightweight materials and suitable for building construction owing to their high structural performance. Conventionally, they are used as purlins and side rails in the building envelopes of industrial buildings. The most common sections are lipped C and Z sections, and the thickness typically ranges from 1.2 to 3.2 mm, and sections with yield strengths at 280, 350 and 450 MPa are commonly available. For connection design, codes of practice for design of cold-formed steel structures only provide design rules for the load carrying capacities of individual fastenings with bolts, screws and welds while no guidance on the structural behavior of connectors such as... 

In recent years, composite systems comprised of reinforced concrete columns and steel beams, have taken consideration. This system took its own advantages both from steel and concrete systems. Joints of this system categorized into through-beam-type and through-column-type. In this research, after reviewing past studies, two kinds of the joints were modeled in ABAQUS finite element program and seismic performance of these two joints were evaluated. These two selected joints were tested by Chin-Tun Chen and Cheng-Chih Chen ( ) and also Hiroshi Kuramoto and Isao Nishiyama ( ). After verifying the finite element model with the experimental studies, a parametric study were conducted on the steel... 

Progressive collapse in the structures can be happened as a result of many events such as terrorist attack, planes or vehicle collision to the structures and etc. Researchers’ attention to this phenomenon after occurring progressive collapse in Ronan Point building attracted and by happening terroristic attacks in Alfred P. Murrah and WTC buildings, studies in this field has developed extensively, meanwhile some of the codes, including UFC 4-023-03 or GSA, have proposed general instructions and analytical methods for increasing the strength of the structure against progressive collapse. If the structure in this analysis, does not meet the acceptance criteria of the code, the structure must... 

Concrete structures may become weak and damage due to different reasons and need retrofitting or strengthening. Strengthening means increasing strength and resistance of members that injured to resist the design loads. The weakness of these structures may due to change in the design code provisions, administrative error, change in the usage of the building and damage caused by different events. In the last decade substantial research has been conducted on this field most of which were on the upgrading of RC beams under different loading. There are few studies in strengthening works of RC beams under static loads of torsion. Most researchers in this field have been used polymer fibers to... 

Light cold formed steel structures have a wide use in building constructions and industrial projects due to their economical advantages, rapid erection and installation and capability for industrial mass production. The main objective of this thesis is to investigate the seismic behavior and to study the seismic requirements for design of Light steel frames (LSF) structures. The cold forming technique, and the basic concepts of cold formed steel members design have been investigated and the basic concepts of seismic design of light cold formed steel structures is discussed. In order to investigate the performance of steel strap framed wall systems and estimate its response modification... 

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... 

Nowadays in high-tech industries there is a serious demand for using advanced materials. Functionally graded materials (FGMs) are in the last generations of these group of materials. FGMs have shown good behavior in special conditions. According to sensitive applications of FGMs , there is a large amount of effort to understand it’s behavior in the presence of crack. Finite element method and other numerical methods, in recent years are widely used in modeling fracture problems.Remeshing requirements and mesh sensitivity are among the disadvantages of analyzing crack growth using the conventional FEM. Recent finite element methods such as extended finite element method, are proposed to model... 

These days steel frames are among the most widespread structural systems, and apart from this, tendency for using slender members in these frames, shows the need for study of effects of axial force and in other words stability of the structure and its members. When secondary effects due to axial gravity forces which results in lateral displacement of the structure come in action, they will reduce strength significantly; as a consequent ductility demand with raise. If this decreased strength exceeds the existing redundant strength, displacements will increase significantly and cause instability of the structure and its collapse. AISC 360-10 has introduced 3 methods for analyzing stability of... 

Fiber Reinforced Polymer (FRP) tendons are suitable to be used in concrete beams exposed to aggressive environments. This study proceeds the design and it presents the flexural capacity (in relation to the moment-curvature) for composite sections (reinforced with steel bars and pre-stressed FRP) rectangular, T-section which has been bent and broken. The failure is in attending with strain softening, stress hardening of fiber reinforced concrete (FRC) and reinforcing with steel bars and polymer. Using the predicted moment-curvature relationship, a numerical method is used to estimate the load deflection response at sample beams under concentrated and uniform loads. A parametric study will be... 

Blind source separation methods such as independent component analysis (ICA) and second order blind identification (SOBI) have shown considerable potential in the area of ambient vibration system identification. The objective of these methods is to separate the modal responses, or sources, from the measured output responses, without the knowledge of excitation. Several frequency domain and time domain methods have been proposed and successfully implemented in the literature. Whereas frequency-domain methods pose several challenges typical of dealing with signals in the frequency-domain, popular time domain methods such as NExT/ERA and SSI pose limitations in dealing with noise, low sensor... 

Computational Nano Mechanics growth has led researchers towards the development of new multi-scale models. Accordingly, in this dissertation, a step was taken towards introduction, presentation and creation of a new concurrent multi-scale by studying the feasibility of coupling of molecular dynamics methods and temperature related Cauchy-born.To do so, firstly, the above mentioned methods have been studied and then in order to perform molecular dynamics simulations, a program written in C++ language has been used. The accuracy of the written code has been confirmed through studying intuitive phenomenon of gas perfect particle exit from cylinder with an open end. The interpretation of out put...