Volume 2 Issue 2
Authors: A.J. Moutsopoulou; A.T. Pouliezos; G.E. Stavroulakis
Abstract: The paper presents active control of smart structures within a focused frame of piezoelectric applications in active vibration and noise attenuation with potential applications in mechanical and civil engineering. Smart structure has become an increasingly common term describing a structure embedded or bonded with a large number of lightweight active electro-mechanical sensors and actuators. In this paper, we consider the modelling and control issues related to smart structures bonded with piezoelectric sensors and actuators with emphasis on robust control design taking into account structural uncertainties using the H Infinity control theory. The results show that the vibrations can be significantly suppressed by H Infinity controller.
Keywords: Smart Structures; Piezoelectric Composite; H Infinity Control
Authors: Nawari O. Nawari
Abstract: Structure is an essential component of architecture, and has always been. However, studying building structures appears to be deceptively complex. This stems from the roles and meanings that buildings possess in human history and civilizations. Buildings provide shelter, inspire productivity, embody cultural history, and certainly play an important part in many aspects of life. In fact, the role of architectural structures is constantly changing in building design as buildings today are life support systems, communication and data terminals, centers of education, justice, and community, and so much more. Thus, for AEC (Architecture, Engineering, and Construction) students, the subject is quite often marked by difficulty. Knowledge, technology and information sharing encompass areas that have significantly affected the learning process for 21st century students. In this environment, computational and simulation tools play a vital supporting and inspiring role. This research proposes a method to develop and enhance the understanding of fundamental principles of architectural and structural analysis using Building Information Modeling (BIM) tools. Without the traditional teaching emphasis on first understanding single elements such as beams, columns, bearing walls, etc., two dimensionally, using the laws of statics and strength of materials, this research will utilize BIM tools to help students create whole three dimensional structural systems and then investigate structural solutions. BIM tools enhance the understanding of structural analysis fundamentals such as the force equilibrium, support reactions, shear force, and bending moment diagrams in an integrated and much inspiring fashion. This approach will allow AEC students to advance a deep learning and long-term retention in studying architectural structures. Understanding the whole structural systems concepts at an earlier stage will enable students to think and later practice in an integrated fashion to meet the demands of today's as well as tomorrow's high-efficient building structures.
Keywords: Studying Structures; BIM Tools; Revit Structure; Structural Melody; Structural Poetry; Conceptual Thinking
Authors: Chuanxiu Luo; Zhiying Wang; Lin Yang; Mingxi Yang
Abstract: This paper used Landsat ETM images as the main data source, and ENVI, GIS and the mathematical statistics method (dynamic degree, land use transition matrix) to analyze spatiotemporal changes of land use and land cover in Baoan, Shenzhen, from 2000 to 2010. Conclusions were as follows. (1) The major land use in the study area was green land. Industrial and storage land experienced the largest increase among the six land classes; external transport land experienced the second largest increase. Water experienced the largest reduction among the six classes, followed by “other” land and green land. (2) Construction land experienced a slow increase, followed by a rapid increase; green land reduced rapidly between 2000 and 2005, followed by a slower reduction between 2005 and 2010. The area of water increased in the early period and decreased in the later period. (3) The increase in construction land came mainly from industrial and storage land, green land, external transport land, and other lands. The increase in industrial and storage land came mainly from construction land, green land, and other lands. The decrease in green land and water area came mainly from the expansion of industrial and storage land, construction land, other land, external transport land.
Keywords: Land Use/Cover Change; Spatiotemporal Analysis; Baoan District; Shenzhen
Authors: Hamid Yaghoubi; Mahmoud Reza Keymanesh
Abstract: Application of magnetically levitated trains (maglev) has attracted numerous transportation industries throughout the world. Maglev stations are centers for planning, traffic attraction, and preparing the fleet. They definitely play a key role in any maglev system. The annual increase in passenger numbers and increasing willingness to use maglev systems indicates the necessity of professional designs for stations. Despite this necessity, no well-accepted report has been presented for the design and evaluation criteria of maglev stations yet. Therefore, a systematic approach is required for this methodology. For this purpose, the research provides a comprehensive overview of the design and evaluation criteria for maglev stations, including structures, equipment, and facilities. Moreover, primary activities at maglev stations are investigated and evaluated. In addition, this paper has tried to adopt a proposed algorithm considering the needs and volume of passengers. These studies facilitate planning and development of maglev stations. Based on this approach, passengers will face stations with appropriate area, the acceptable service and welfare space. This will answer the growth of passenger traffic in maglev systems and attract more passengers.
Keywords: Magnetic Levitation; Magnetically Levitated Trains; Maglev; Guideway; Station; Design Criteria; Maintenance; Land Use
Authors: Josafath Israel Espinosa Ramos; Roberto A. Vázquez
Abstract: Most of the real world optimization problems are naturally multi-objective problems. In order to simplify the solution, many of them are modelled as mono-objective problems. The purpose of this research is to design a seismic network to maximize the warning time of a particular city; that is, the gap between the time when the alert is launched and the arrival time of the disaster, and minimizing the number of seismic stations in the network. To attack this multi-objective optimization problem, it is proposed to turn it into a mono-objective constrained problem and solve it with a simple genetic algorithm. As a case study, it was considered the region of the State of Guerrero, Mexico, where the seismic network could take place. The main disasters targeted in this paper are earthquakes, but this research can be extended easily to alert systems of tsunamis or volcanic eruptions, for the positioning of telecommunications antennas, etc.
Keywords: Design of Seismic Sensor Networks; Optimization; Artificial Intelligence; Genetic Algorithms; Computer Application; Profitability
Authors: S.A. Nojoumi; M.R. Bahaari; S.M. Ghodratian; M Ghassemieh
Abstract: This paper investigates the effectiveness of Shape Memory Alloys (SMAs) in enhancing the seismic behavior of coupled shear walls. First, SMA braces or strands are implemented in the shear wall openings for repairing and retrofitting purposes. A finite element program, SeismoStruct, is used to evaluate the seismic behavior of the controlled structure. For retrofitting purpose, a multi story concrete shear wall building with and without SMA elements is exposed to El-centro earthquake record for 15 seconds, followed with 25 seconds of damped free vibration. For repairing purpose, the structure in the first 40 seconds, is excited with El-centro earthquake and in the second stage, after adding the SMA braces, the same record is applied in second of 40 to simulate the aftershock. Results indicate that the proposed enhancement can successfully reduce the maximum displacements and permanent residual deflections of the existing shear wall structures. In the second part, as new designing technique, shear wall is reinforced with SMA reinforcement bars instead of conventional steel bars and/or with combination of SMA and steel reinforcement. ABAQUS finite element program is used to capture the seismic behavior of the concrete wall and the SMA material is implemented in the computer program by using FORTRAN as a subroutine material module. The structure is evaluated through nonlinear static as well as dynamic time history analyses. The results show that SMA reinforcement can significantly restore the residual displacement in the shear wall.
Keywords: Shape Memory Alloy; Coupled Shear Wall; Seismic Behavior; Seismostruct Software; ABAQUS Software
Effect of Loading Rate on the Settlement of Axially Loaded Modeled Square and Circular Piles in Clay
Authors: Taiye Adejumo
Abstract: This paper presents the results of experimental investigations of the effect of loading rate on deformation and settlement of axially loaded modeled square and circular piles in clay. The modeled piles were sawn, sharpened and carved from strong wood. The configurations of both square and circular section consist of 20 mm and 200 mm for diameter and length respectively. Single pile as well as pile groups of 2x2 (4 piles) with centre to centre spacing (a) = 4d, and 3x3 (9 piles) with centre to centre (a) = 3d, were driven into clearly marked layered clay soils differentiated by moisture and density of w = 20%, γ = 17 kN/m3 for the weak layer, and w = 10%, γ = 19 kN/m3 for the strong layer), with a third layer of reinforced weak soil having reinforcing bars placed in it. The tests were conducted in a specially designed testing equipment/tank. At the loading rates of 0.01, 0.05, 0.1 and 1mm/min, the modeled piles were subjected to axial compressive loads and the effect on the soils in the inter-pile spacing, as well as those under and around the piles were evaluated. The pile axial capacity increases with the loading rate. Also, the relationship between applied load and pile displacement within the load bearing limit was observed to be linear. The initial settlements of square piles are generally higher than circular piles, but the latter gives an over-all settlement of 14 - 18% higher than the former.
Keywords: Loading Rate; Settlement; Compressive Loads; Deformation; Wooden Piles; Clay