APPLICATION OF SPECTRAL FINITE ELEMENT METHOD IN ANALYSIS OF TRANSIENT ELASTODYNAMIC PROBLEMS0 تومان
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 Statistics and Probability for Engineers0 تومان
An engineer is someone who solves problems of interest to society by the efficient application of scientific principles. Engineers accomplish this by either refining an existing product or process or by designing a new product or process that meets customers’needs. The engineering, or scientific, method is the approach to formulating and solving these problems. The steps in the engineering method are as follows: 1. Develop a clear and concise description of the problem. 2. Identify, at least tentatively, the important factors that affect this problem or that may play a role in its solution. 3. Propose a model for the problem, using scientific or engineering knowledge of the phenomenon being studied. State any limitations or assumptions of the model. 4. Conduct appropriate experiments and collect data to test or validate the tentative model or conclusions made in steps 2 and 3. 5. Refine the model on the basis of the observed data. 6. Manipulate the model to assist in developing a solution to the problem. 7. Conduct an appropriate experiment to confirm that the proposed solution to the problem is both effective and efficient. 8. Draw conclusions or make recommendations based on the problem solution. The steps in the engineering method are shown in Fig. 1-1. Notice that the engineering method features a strong interplay between the problem, the factors that may influence its solution, a model of the phenomenon, and experimentation to verify the adequacy of the model and the proposed solution to the problem. Steps 2–4 in Fig. 1-1 are enclosed in a box, indicating that several cycles or iterations of these steps may be required to obtain the final solution. Consequently, engineers must know how to efficiently plan experiments, collect data, analyze and interpret the data, and understand how the observed data are related to the model they have proposed for the problem under study.
Applied Structural and Mechanical Vibrations0 تومان
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 MANUAL0 تومان
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.
Assessment of Equivalent Static Earthquake Analysis Procedure for Structures with Mass Irregularity in Height0 تومان
Sudden changes in structural dimensions and mass irregularities are inevitable in urban buildings. Most building codes have different analysis and design previsions for such buildings. In this article, such provisions based on the Iranian seismic code of practice (Standard No. 2800), which is to a great extent similar to UBC-97 model code, are verified in order to assess the provisions for different types of structures. Thus, four two-dimensional residential type steel structures with 4, 8, 12 and 16 stories and with different forms of mass irregularities in height are designed using the standard equivalent static procedure per the Iranian Seismic Code of practice. The designed structures, then, were subjected to different nonlinear static (pushover) and dynamic analyses. Two levels of irregularities, i.e. 150 and 300 percents, located at the heights equal to 50% and 75% of the overall height of the structures, have been considered. The results show that the static procedure adapted in the code results in much higher internal forces, story shears and overturning moments in various parts of the structures compared to the dynamic results. Also, this study shows that lateral inter-story drifts obtained using the equivalent static procedure and dynamic analyses are quite comparable for short buildings. For taller buildings, in contrast, dynamic analyses showed less inter-story drifts. It is also observed that mass irregularities in height could be responsible for more contribution of higher modes in seismic response of such structures
Autoclaved aerated concrete behavior under explosive action0 تومان
Autoclaved aerated concrete AAC is widely used in construction, mainly in masonry as infill walls. Exterior AAC walls may Ž . be subjected to different actions including accidental lateral dynamic loading and local fragments’ impact. The present paper studies some of the dynamic characteristics of AAC walls under localized high-intensity impact, such as the number of cracks and their dependence on the boundaries location, the initiation of spalling and the contribution of face treatment and face reinforcement on enhancing the materials response. Some comparisons are made with earlier results on hardened cement paste specimens.
Bee Colony Optimization of Tuned Mass Dampers for Earthquake Vibrations of High-rise Buildings Including Soil Structure Interaction0 تومان
This paper investigates the optimization of Tuned Mass Dampers (TMDs) for high-rise buildings. The model is assumed as a 40 story building with 160m height considering the translation and rotation of foundation. The Soil Structure Interaction (SSI) is considered for the better prediction of building’s response. To illustrate the results, Bam earthquake data is applied to the model. The three soil types, i.e. soft, medium and dense soil are utilized, and the results are compared with the fixed based model. The model is based on time domain analysis, and Newmark method is used to obtain the displacement, velocity and acceleration of different elements. The Artificial Bee Colony (ABC), a heuristic method based on the behavior of bees forage for food, is employed to obtain the best parameters for TMD device. The design variables are assumed as mass, damping and spring stiffness quantity. The objective is to decrease both the maximum displacement and acceleration of the building. The results show that the presented model can be effectively applied to evaluate the response of high-rise buildings including SSI effects. It is indicated that the results obtained by this model is more accurate than the results of fixed based model. The effects of TMD on the oscillations of structures including different soil characteristics are also investigated. It is shown that the TMD is more effective for soft soil foundations. It is also shown that how the bee colony optimization technique can be employed to design the optimum TMD for the minimum displacement and acceleration. This study leads the researchers to the better understanding of earthquake oscillations of the high-rise buildings, and helps the designers to achieve the optimized TMD for the structures.
BRIDGE ENGINEERING0 تومان
Bearings are structural devices positioned between the bridge superstructure and the substructure. Their principal functions are as follows: 1. To transmit loads from the superstructure to the substructure, and 2. To accommodate relative movements between the superstructure and the substructure. The forces applied to a bridge bearing mainly include superstructure self-weight, traffic loads, wind loads, and earthquake loads. Movements in bearings include translations and rotations. Creep, shrinkage, and temperature effects are the most common causes of the translational movements, which can occur in both transverse and longitudinal directions. Traffic loading, construction tolerances, and uneven settlement of the foundation are the common causes of the rotations. Usually a bearing is connected to the superstructure through the use of a steel sole plate and rests on the substructure through a steel masonry plate. The sole plate distributes the concentrated bearing reactions to the superstructure. The masonry plate distributes the reactions to the substructure. The connections between the sole plate and the superstructure, for steel girders, are by bolting or welding. For concrete girders, the sole plate is embedded into the concrete with anchor studs. The masonry plate is typically connected to the substructure with anchor bolts.
BRIDGE ENGINEERING0 تومان
This chapter addresses some of the principles and practices applicable to the construction of mediumand long-span steel bridges — structures of such size and complexity that construction engineering becomes an important or even the governing factor in the successful fabrication and erection of the superstructure steelwork. We begin with an explanation of the fundamental nature of construction engineering, then go on to explain some of the challenges and obstacles involved. The basic considerations of cambering are explained. Two general approaches to the fabrication and erection of bridge steelwork are described, with examples from experience with arch bridges, suspension bridges, and cable-stayed bridges. The problem of erection-strength adequacy of trusswork under erection is considered, and a method of appraisal offered that is believed to be superior to the standard working-stress procedure. Typical problems with respect to construction procedure drawings, specifications, and practices are reviewed, and methods for improvement suggested. The need for comprehensive bridge erection-engineering specifications, and for standard conditions for contracting, is set forth, and the design-andconstruct contracting procedure is described. Finally, we take a view ahead, to the future prospects for effective construction engineering in the U.S. The chapter also contains a large number of illustrations showing a variety of erection methods for several types of major steel bridges.
Building Automation0 تومان
The level of automation in residential and commercial buildings has risen steadily over the years. This is not only due to the increasing demand for more comfort and convenience, but also the benefits building automation brings with regard to saving and managing energy. Security is another important factor, particularly in residential buildings. Whereas in commercial buildings flexibility is high on the agenda – offices buildings, for example, should be designed in such way that they can be easily adapted to meet any change in use or requirements.
BUILDING CODE REQUIREMENTS FOR STRUCTURAL CONCRETE (ACI 318-05) AND COMMENTARY (ACI 318R-05)0 تومان
This commentary discusses some of the considerations of Committee 318 in developing the provisions contained in “Building Code Requirements for Structural Concrete (ACI 318-05),” hereinafter called the code or the 2005 code. Emphasis is given to the explanation of new or revised provisions that may be unfamiliar to code users. In addition, comments are included for some items contained in previous editions of the code to make the present commentary independent of the previous editions. Comments on specific provisions are made under the corresponding chapter and section numbers of the code. The commentary is not intended to provide a complete historical background concerning the development of the ACI Building Code,* nor is it intended to provide a detailed résumé of the studies and research data reviewed by thecommittee in formulating the provisions of the code. However, references to some of the research data are provided for those who wish to study the background material in depth.
BUILDING SERVICES HANDBOOK0 تومان
Acid † a substance containing hydrogen which can be replaced by other elements. Litmus paper in the presence of acidic water turns red. Alkali † a substance which will neutralise acid by accepting its hydrogen ions (H+). Litmus paper in the presence of alkaline water turns blue. More accurate definitions can be obtained by using hydrochemical electric metres. These measure the amount of hydrogen ions (H+) in a relative proportion of water. This measure of acidity or alkalinity in solution is referred to numerically from 0†14 as the pH value. . pH < 7 indicates acidity . pH > 7 indicates alkalinity . pH = 7 chemically pure The quality of processed water is unlikely to be pure due to contamination at source. Rainwater † contaminated by suspended impurities as it falls through the air. These impurities are principally carbon dioxide, sulphur and
nitrous oxides originating from domestic flue gases and industrial manufacturing processes. The mixture of these impurities and rainfall produce `acid rain’, an occurrence frequently blamed for the destruction of plant life. Surface and substrata water sources † contaminated by dissolved inorganic materials such as calcium, magnesium and sodium. These are responsible for water hardness as described on pages 5 and 17. Organic matter from decaying vegetation, animals and untreated waste water can also contaminate ground water supplies. These are normally associated with ammonia compounds in the water or bacteria. Certain types of bacteria present in water can be responsible for outbreaks of typhoid, cholera and dysentery. Chlorination, as described on page 5 is applied to filtered water to destroy any remaining bacterial microbes before general distribution through service reservoirs and mains.
BUILDING SYSTEMS FOR INTERIOR DESIGNERS0 تومان
This book owes its existence to the support and talents of many people. In targeting the needs of interior designers, I began by researching the materials already available for students of architecture and engineering. I am especially indebted to the Ninth Edition of Mechanical and Electrical Equipment for Buildings by Benjamin Stein and John S. Reynolds (John Wiley & Sons, Inc., NY, 2000), whose comprehensive and clear coverage of building systems was both a standard for excellence and a source for accurate information. I would never have started on the road to writing this text without the encouragement of Professor RoseMary Botti- Salitsky IDEC, IIDA of Mount Ida College, and of Thomas R. Consi Ph.D. at the Massachusetts Institute of Technology, a dear friend whose faith in my ability far exceeds my own. Professor Allan Kirkpatrick of Colorado State University shared his contacts and experience as a textbook author, providing the critical link to making this book a reality .
CIVIL ENGINEERING FORMULAS0 تومان
Many engineers, professional societies, industry associations, and governmental agencies helped the author find and assemble the thousands of formulas presented in this book. Hence, the author wishes to acknowledge this help and assistance. The author’s principal helper, advisor, and contributor was the late Frederick S. Merritt, P.E., Consulting Engineer. For many years Fred and the author were editors on companion magazines at The McGraw-Hill Companies. Fred was an editor on Engineering-News Record, whereas the author was an editor on Power magazine. Both lived on Long Island and traveled on the same railroad to and from New York City, spending many hours together discussing engineering, publishing, and book authorship. When the author was approached by the publisher to prepare this book, he turned to Fred Merritt for advice and help. Fred delivered, preparing many of the formulas in this book and giving the author access to many more in Fred’s extensive files and published materials. The author is most grateful to Fred for his extensive help, advice, and guidance.
Combining contemporary and traditional project management tools to resolve a project scheduling problem0 تومان
In this paper we examine a construction project involving the building of large concrete slabs for three buildings in an office park complex. There are finish-to-start (FS) as well as start-to-start (SS) and finishto- finish (FF) precedence relationships among the project activities. We prepare an initial project schedule using Microsoft Project and manually validate the results using the precedence diagramming method (PDM) procedure. When the client informs us that the schedule must be shortened we find that Microsoft Project does not have the capability for resolving our particular time/cost tradeoff issues. So we revert to the traditional approach for resolving time/cost tradeoffs in projects and develop an original linear programming formulation for the time/cost tradeoff problem when a project is modeled as a precedence diagram. By combining contemporary (Microsoft Project) and traditional (a linear programming time/cost tradeoff model) project management tools we are able to successfully resolve the scheduling issues associated with the slab construction project. Further, we demonstrate the anomalous effects of start-to-start (SS) and finish-to- finish (FF) relationships via our construction project example in which the solution to the time/cost tradeoff problem requires that certain activities be lengthened in order to shorten the project duration.
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