Showing 25–36 of 807 results
Assessment of Equivalent Static Earthquake Analysis Procedure for Structures with Mass Irregularity in Height
Sudden changes in st...رایگان!
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 action
Autoclaved aerated cرایگان!
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 Interaction
This paper investigaرایگان!
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.
Bearings are structuرایگان!
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.
The level of automatرایگان!
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)
This commentary discرایگان!
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 SYSTEMS FOR INTERIOR DESIGNERS
This book owes its eرایگان!
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 .
Combining contemporary and traditional project management tools to resolve a project scheduling problem
In this paper we exaرایگان!
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.
Comparison between Seismic Behavior of Suspended Zipper Braced Frames and Various EBF Systems
Zipper frames are in...رایگان!
Zipper frames are intended to improve on the behavior of conventional inverted-V-braced frames, which show poor performance taking place from the early buckling of braces in the lower story. A zipper frame affords better performance by forcing simultaneous buckling of all braces. In this article, seismic behaviors of zipper braced frames and three types of eccentrically braced frames are evaluated using finite element simulation. Two dimensional finite element models have been created for three-story onebay frames for various bay lengths and different arrangement of braces. Seismic response of frames subjected to near-fault ground motions (LA21) has been studied through dynamic analysis, considering no nlinearity of geometry and materials. For this purpose, SAP2000 has been used. Results have been ompared and structural response of steel frames and some other parameters such as ductility of frames, maximum base shear and optimized link length have been investigated. Against other researches, in this article, the ratio of maximum shear over the weight of structure and its relation to behavior of structure has also been studied. It was found that optimized link length in EBF systems which caused to maximum du ctility of frame is about 30 percent of the bay length. Moreover, the results showed that zipper frames provide desirable post buckling behavior and exhibit more ductility.
Compliance of Rigid Arbitrary Shape Foundations Using 1 DOF BEM
In this study the reرایگان!
In this study the relationship between the dynamic force and displacement (impedance or compliance) is evaluated for rigid foundations with arbitrary shape resting on a half-space medium, consisting of homogeneous, isotropic, linear elastic materials with constant Boundary Element Method, (1 DOF). Green’s function is computed for half-space and presented in explicit form. By using BEM formulation the stress beneath foundations and compliance of them are obtained. The vertical compliance of a rigid circular disc which is calculated by this method is compared by semi-closed form solution and verifies the accuracy and efficiency of this method. the vertical and rocking compliance functions for rigid rectangular and some arbitrary shape foundations are obtained. And also, the variation of stress distribution pattern beneath square and circular foundations with frequency is studied and these results are compared with the results of the other methods.
Critical appraisal of piping phenomena in earth dams
This paper presentsرایگان!
This paper presents a comprehensive review of published literature on soil piping phenomena. The first tools to design earth dams to resist piping were developed during 1910–1935. Filter criteria for dispersive soils was refined in the 1970’s. Piping phenomena are generally defined as: (1) heave, (2) internal erosion, (3) backwardserosion, although other modes are possible. Recent work on piping highlights the limitations of the occurrence of piping and the role that design and construction may play in a large percentage of piping failures. Standardized laboratory procedures are available to assess piping potential in cohesive materials, but no such methods exist for noncohesive soils. However, methods are available for evaluation of self-filtration potential. Recent advances in computer technology have facilitated the evaluation of seepage and deformation in embankments but computational methods for evaluation of piping potential are currently limited.
Cyclic axial response and energy dissipation of cold-formed steel framing members
This paper summarizeرایگان!
This paper summarizes results from an experimental program that investigated the cyclic axial behavior and energy dissipation of cold-formed steel C—sections structural framing members. Fully characterized cyclic axial load–deformation response of individual members is necessary to facilitate performancebased design of cold-formed steel building systems. Specimen cross-section dimensions and lengths were selected to isolate specific buckling modes (i.e., local, distortional or global buckling). The cyclic loading protocol was adapted from FEMA 461 with target displacements based on elastic buckling properties. Cyclic response showed large post-buckling deformations, pinching, strength and stiffness degradation. Damage accumulated within one half-wave after buckling. The total hysteretic energy dissipated within the damaged half-wave decreased with increasing cross-section slenderness. More energy dissipation comes at the cost of less cumulative axial deformation before tensile rupture.