Showing 13–24 of 807 results
A Teaching Guide for Structural Steel Connections
Connection design inرایگان!
Connection design in an introductory steel course is often difficult to effectively communicate. Time constraints and priority of certain other topics over connection design also tend to inhibit sufficient treatment of connection design. The Steel Connections Teaching tool kit is an attempt to effectively incorporate the fundamentals of steel connection design into a first course in steel design. The tool kit addresses three broad issues that arise when teaching students steel connection design: visualization, load paths, and limit states. In structural analysis classes, students are shown idealized structures. Simple lines represent beams and columns, while pins, hinges, and fixed supports characterize connections. However, real structures are composed of beams, girders, and columns, all joined together through bolting or welding of plates and angles. It is no wonder that students have trouble visualizing and understanding the true threedimensional nature of connections! The steel sculpture provides a convenient means by which full-scale steel connections may be shown to students. The steel sculpture exhibits over 20 different connections commonly used in steel construction today. It is an exceptional teaching instrument to illustrate structural steel connections. The steel sculpture’s merit is nationally recognized as more than 90 university campuses now have a steel sculpture modeled after Dr. Ellifritt’s original design. In addition to the steel sculpture, this booklet provides illustrations, and each connection has a short description associated with it.
Active Earth Pressure of Modeled Strip Load Surcharge on Rigid Walls
In determination of ...رایگان!
In determination of the active earth pressure of strip load surcharge, we would always do elastic supposition, and for that, we used boussinesq. In this essay, by supposition of plastic environment of the earth, a new formula was presented for the effect of strip load surcharge on the wall. In this new formula, effects of gradient, and the friction angle between earth and wall, and gradient of the wall, and friction angle of earth, is considered. In this essay, by MATLAB software, a program is presented for calculation of the pressure on the wall in different situations of setting strip load surcharge. Also this essay considers the distance of the effect of strip load surcharge, and by mean of that, we can determine the length of the surcharge and the distance of surcharge from wall which has taken effects from the imported pressure. It should be pointed out that imported pressure totally consists of earth pressure and surcharge pressure. This essay expresses the considered stress distribution, under the effect of strip load surcharge on the wall having the effect of the earth behind it. And dependent on the situation of strip load surcharge, we present four kinds of distribution.
ADAPTING BUILDINGS AND CITIES FOR CLIMATE CHANGE
The war against climرایگان!
The war against climate change pitches mankind against a global threat that vastly eclipses that of terrorism,1 in battles that have already claimed the lives of hundreds of thousands of ordinary men and women from every continent. Climate change has led us into an era in which war and conflict are endemic,2 the widespread extinction of species approaches catastrophic proportions,3 andwhole regions and countries will be lost beneath the swelling seas and the expanding deserts of a rapidly warming world. And the really bad news is that ‘the world has only one generation, perhaps two, to save itself’.4 We all instinctively know, already, that the climate is changing, from the small noticed things like the unseasonable patterns of the flowering of plants, the falling of snow and the growing in strength of the wind and the rain. With this knowledge comes a growing apprehension of danger. Deep down, in quiet moments, we ask ourselves questions that a year or two ago were unthinkable: ● What will I do when the lights do go out? ● Will the house flood next year? ● Will my home get so hot this summer that I won’t be able to stay in it? ● How long could I survive in this building without air conditioning? ● Where will we go? ● Will we survive? This book is written to enable you, the reader, to get a clearer view of the ways in which the climate is changing and how these changes will affect your life tomorrow and the day after, in the buildings, settlements and regions in which you live and work.
Adaptive boundary control of a flexible marine installation system
In this paper, boundرایگان!
In this paper, boundary control of a marine installation system is developed to position the subsea payload to the desired set-point and suppress the cable’s vibration. Using Hamilton’s principle, the flexible cable coupled with vessel and payload dynamics is described as a distributed parameter system with one partial differential equation (PDE) and two ordinary differential equations (ODEs). Adaptive boundary control is proposed at the top and bottom boundaries of the cable, based on Lyapunov’s direct method. Considering the system parametric uncertainty, the boundary control schemes developed achieve uniform boundedness of the steady state error between the boundary payload and the desired position. The control performance of the closed-loop system is guaranteed by suitably choosing the design parameters. Simulations are provided to illustrate the applicability and effectiveness of the proposed control.
Advanced Structural Dynamics and Active Control of Structures
Flexible structures in motion have specific features that are not a secret to a structural engineer. One of them is resonance—strong amplification of the motion at a specific frequency, called natural frequency. There are several frequencies that structures resonate at. A structure movement at these frequencies is harmonic, or sinusoidal, and remains at the same pattern of deformation. This pattern is called a mode shape, or mode. The modes are not coupled, and being independent they can be excited separately. More interesting, the total structural response is a sum of responses of individual modes. Another feature—structural poles—are complex conjugate. Their real parts (representing modal damping) are typically small, and their distance from the origin is the natural frequency of a structure.
An Adaptive IHS Pan-Sharpening Method
The goal of pan-sharرایگان!
The goal of pan-sharpening is to fuse a low spatial resolution multispectral image with a higher resolution panchromatic image to obtain an image with high spectral and spatial resolution. The Intensity-Hue- Saturation (IHS) method is a popular pan-sharpening method used for its efficiency and high spatial resolution. However, the final image produced experiences spectral distortion. In this letter, we introduce two new modifications to improve the spectral quality of the image. First, we propose imageadaptive coefficients for IHS to obtain more accurate spectral resolution. Second, an edge-adaptive IHS method was proposed to enforce spectral fidelity away from the edges. Experimental results show that these two modifications improve spectral resolution compared to the original IHS and we propose an adaptive IHS that incorporates these two techniques. The adaptive IHS method produces images with higher spectral resolution while maintaining the high-quality spatial resolution of the original IHS .
Analytical solution for axisymmetric thermoelastodynamic problems in a transversely isotropic half-space under a surface loading
In the present studyرایگان!
In the present study, the theory of coupled thermoelastodynamic is applied to determine the displacement, temperature and stress (DTS) fields of a torsionless axisymmetric transversely isotropic half-space under a surface loading. The basic equations of coupled thermoelasticity consist of the equations of motion and the energy equation, which forms a set of completely coupled partial differential equations for the displacement and temperature fields. Potential method is employed for uncoupling the set of basic equations of coupled thermoelasticity. With the aid of a potential function existed in the literature, the system of equations are uncoupled, where a sixth order partial differential equation is received. Displacement components and temperature are written with respect to the potential function in cylindrical coordinate system. The Laplace and Hankel integral transforms are employed to suppress the time and radial variables, respectively. One may apply the inverse Hankel and Laplace transforms to determine the DTS fields and other quantities of interest in physical (space-time) domain. Eventually, the integrand functions of DTS components are obtained analytically.
Analyzing Uncertainty in Civil Engineering
The characteristic sرایگان!
The characteristic shear strength parameters of soil are obviously decisive for the geotechnical design. Characteristic parameters are defined as cautious estimates of the soil parameters affecting the limit state. It is shown how geotechnical engineers interpret this cautious estimate. Due to the inherent lack of data in geotechnical investigations there is always a certain degree of subjectivity in assessing the characteristic soil parameters. The range of characteristic shear parameters assigned to the same set of laboratory experiments by 90 geotechnical engineers has been used to design a spread foundation. The resulting geometrical dimensions are remarkably different. It is concluded that geotechnical calculations are rather estimates than exact predictions. Thus for intricate geotechnical projects a sensitivity analysis should be performed to find out critical scenarios. Furthermore a continuous appraisal of the soil properties during the construction process is indispensable.
APPLICATION OF SEISMIC BASE ISOLATION TECHNOLOGY IN IRAN
Application of baseرایگان!
Application of base isolation techniques in Iran goes back to hundreds of years ago and even to ancient times. Installing pieces of wood between the foundation and the walls of buildings is among the earthquake resistant construction techniques that have been applied in some areas of Iran in the past. However, contrary to other technologies which are generally adapted soon after their development, modern seismic base isolation technology took almost a quarter of a century to be adapted and utilized in Iran. This paper presents the historical as wells as the modern application of seismic base isolation technology in Iran.
APPLICATION OF SPECTRAL FINITE ELEMENT METHOD IN ANALYSIS OF TRANSIENT ELASTODYNAMIC PROBLEMS
Dealing with wave prرایگان!
Dealing with wave propagation phenomena using classical finite element method (FEM) results in some inefficiencies and inaccuracies in the solution. Spectral finite element method (SFEM) as a method based on FEM, presents some new features that makes it much more suitable and useful for solving wave propagation problems. The excellent characteristic of SFEM is that the mass matrix is diagonal because of the choice of the Lagrange interpolation function supported on Legendre-Gauss-Lobatto (LGL) points in conjunction with LGL integration rule. Therefore numerical calculations can be significantly efficient in comparison with the classical FEM. On the other hand choice of high order elements using specific shape functions gives us the possibility to increase the accuracy of the solution while decreasing the total number of elements used for the domain of the problem thus decreasing the analysis time. In this paper, a SFEM-based code is represented and verified, and then some wave propagation problems in elastic solid domains are solved using this code showing the capabilities of SFEM in solving elastodynamic problems.Some problems are solved using different spectral elements, and analysis time, accuracy of the solution and costs of analysis in different solutions is compared to analytical and/or numerical solutions available in the literature.
Applied Structural and Mechanical Vibrations
It is now known fromرایگان!
It is now known from basic physics that force and motion are strictly connected and are, by nature, inseparable. This is not an obvious fact; it has taken almost two millennia of civilized human history and the effort of many great minds to understand. At present, it is the starting point of almost every branch of known physics and engineering. One of these branches is dynamics: the study that relates the motion of physical bodies to the forces acting on them. Within certain limitations, this is the realm of Newton’s laws, in the framework of the theory that is generally referred to as classical physics. This is Newton’s second law which defines the unit of force once the fundamental units of mass and distance are given. An important part of dynamics is the analysis and prediction of vibratory motion of physical systems, in which the system under study oscillates about a stable equilibrium position as a consequence of a perturbing disturbance which, in turn, starts the motion by displacing the system from such a position. This type of behaviour and many of its aspects—wanted or unwanted— is common everyday experience for all of us and is the subject of this book . However, it must be clear from the outset that we will only restrict our attention to ‘linear vibrations’ or, more precisely, to situations in which vibrating systems can be modelled as ‘linear’ so that the principle of superposition applies. Future sections of this chapter and future chapters will clarify this point in stricter detail.
ASPHALT MATERIALS AND MIX DESIGN MANUAL
The purpose of the Mرایگان!
The purpose of the Manual for Asphalt Materials and Mix Design (hereafter referred to as The MANUAL) is to familiarize students with the technology of asphalt in its several forms namely asphalt cement, cutback asphalt, and asphalt emulsions. The laboratory work is designed to develop an understanding of asphalt properties, characteristics, testing procedures, and specifications. For engineering purposes three properties of asphalt are paramount: consistency (usually referred to as viscosity), purity, and safety. Before asphalt cement can be used for construction purposes it must be liquefied. This implies heating. Asphalt cement must be liquefied before it can be pumped through pipes, mixed with aggregates to make asphalt concrete, or sprayed through nozzles. Once the heat is dissipated, the asphalt cement reverts to its amorphous, semi- solid state. There are other ways to liquefy asphalt. Selected petroleum based solvents can dissolve the asphalt cement to create a family of materials known as cutback asphalts. Another method is to combine asphalt cement with water in the presence of a catalyst to form various kinds of asphalt emulsions. The procedures outlined herein are all derived from ASTM designations and practice as recommended by the Asphalt Institute. Where the particular ASTM method permits alternate rocedures, the one more applicable to the available equipment and the teaching situation was chosen. In the preparation of this MANUAL, the inherent time constraints of an academic laboratory was considered, whenever possible.