Conferences, Lectures, & Seminars
Events for January
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SMART BUILDINGS: SYNERGY IN STRUCTURAL CONTROL, HEALTH MONITORING AND ENVIRONMENTAL SYSTEMS
Thu, Jan 08, 2009 @ 02:00 PM - 04:00 PM
Sonny Astani Department of Civil and Environmental Engineering
Conferences, Lectures, & Seminars
Oral Defense By: Tat S. FuSonny AstaniDepartment of Civil and Environmental EngineeringAbstract:
Smart buildings are different from traditional buildings in their ability to react to external and internal building conditions and provide building functions that concern safety, comfort and energy efficiency. The capability to monitor and control different building systems makes a building smart. Efficient cooperation among various building systems is also crucial because of the increasing complexity in buildings. This dissertation focuses on structural control and health monitoring as well as integrating the structural system with an environmental system to create safe, energy efficient and smart buildings.
Structural health monitoring (SHM) aims to assess the health of structures in a systematic and automatic manner. Cost and reliability are the biggest challenges for SHM. A SHM system with a wireless sensor network is studied to reduce cost by avoiding expensive wiring in installation. To reduce radio communication and, thus, battery power usage on the wireless sensors, a distributed algorithm is used to process the data at the sensor nodes for estimating modal parameters. Optimization of a sensor placement is then studied for SHM purposes and wireless sensor networks. Reliability in damage detection is also examined for both global and local excitations. With the measured responses from exciting the structure globally, an SHM algorithm is expanded to conduct multi-directional analysis, providing more information and accuracy on damage detection. By exciting a structural member locally and studying the wave propagation within this member, damage is successfully detected and the effect of sensor placements on damage detection accuracy is analyzed.
Synergy of integrating structural and environmental systems is explored with a proposed Shading Fin Mass Damper (SFMD) system. Traditionally static shading fins are made movable and heavier to function as mass dampers. The added mobility allows the fins to change positions for greater sunlight control, thus minimizing energy consumption on cooling and heating loads. Since the shading fins are placed along the height of the building, the dampers are distributed rather than concentrated in a few locations as in typical tuned mass damper systems. Passive, active and semiactive control strategies are analyzed for the distributed mass damper (DMD) system; results show that the DMD system can reduce structural vibration significantly. Additionally, the actuators controlling the movements of the SFMDs are studied to excite the structure for SHM. It is observed that by using combinations of the multiple actuators, damaged detection can be greatly improved for the DMD system.Location: Kaprielian Hall (KAP) - 209
Audiences: Everyone Is Invited
Contact: Evangeline Reyes
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Exposure Assessment and Source Apportionment of Size Fractions of Airborne Particulate Matter
Tue, Jan 13, 2009 @ 10:30 AM - 01:00 PM
Sonny Astani Department of Civil and Environmental Engineering
Conferences, Lectures, & Seminars
Oral Defense by:Mohammad ArhamiSonny AstaniDepartment of Civil and Environmental EngineeringAdvisor: Prof. Constantinos SioutasAbstract
The aim of this thesis is to enhance the knowledge on exposure to size fractions of airborne particulate matter and their components and to find more intensive information on sources of indoor and outdoor size fractionated particles. In the first part of the study, the physical and chemical characteristics of indoor, outdoor, and personal quasi-ultrafine (In the following, we characterized the physicochemical properties and sources of size fractionated PM and their spatial and seasonal variability at the Los Angeles-Long Beach harbor community, which is the busiest harbor in the US and the fifth in the world. The major mass contributions in the quasi-UF fraction were particulate organic matter, non-sea salt sulfate and elemental carbon; in the accumulation mode fraction were non-sea salt sulfate, sea salt, particulate organic matter and nitrate; and in the coarse fraction were sea salt and insoluble soil. In general, PM and its components in accumulation mode showed relatively lower spatial variability compare to the quasi-UF and the coarse modes. The vehicular sources accounted for almost all of quasi-ultrafine PM and more than 50% fine PM, whereas ship contribution was lower than 5% of total PM mass. Our results clearly indicate that, although ship emissions can be significant, PM emissions in the area of the largest US harbor are dominated by vehicular sources. The results obtained in this study have been/will be used to examine the relationships between outdoor (or ambient), indoor and personal measurements of atmospheric particulate air pollution and health outcomes and to link health effects to certain sources of particulate matter. Such information would be highly valuable for targeting control strategies that protect human health and life.
Location: Kaprielian Hall (KAP) - 209
Audiences: Everyone Is Invited
Contact: Evangeline Reyes
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Three Applications of the Reciprocal Theorem in Soil-Structure Interaction
Fri, Jan 16, 2009 @ 01:00 PM - 04:00 PM
Sonny Astani Department of Civil and Environmental Engineering
Conferences, Lectures, & Seminars
Oral Defense by:Kirsten McKaySonny AstaniDepartment of Civil and Environmental EngineeringABSTRACT: Using the Reciprocal Theorem and the principle of superposition, this dissertation examines three procedures for obtaining the impedance functions and driving force vectors necessary for a soil-structure interaction analysis. The first procedure employs a volume integral of body forces and the displacement Green's Functions to obtain the frequency dependent force-displacement relationship (impedance functions) for a rigid embedded foundation and the generalized force vector required to hold the rigid foundation fixed while subjected to incident waves (driving force). Although a formulation based on a volume integral requires more computation than the others based on surface integrals, this procedure proves to be numerically stable and is an excellent tool for linear soil- structure interaction analyses. The second procedure is based on integrating the surface displacements with the traction Green's Functions and surface tractions with the displacement Green's Function, over the surface of a rigid foundation. This well-known formulation has numerical instability problems at the resonant frequencies of the medium interior to the foundation surface.
This dissertation explains the reason behind the instability using an analytical solution of the Hilbert-Schmidt method and recommends an algorithm which uses the l'Hospitale Rule to obtain the solution at those critical frequencies. The development herein for this method is not meant to be a practical solution, but an academic exercise to explain a long-standing, puzzling problem. The third and final procedure is to design a radiation boundary for a three-dimensional finite element grid using the surface displacements and surface tractions at the discrete artificial boundary, along with the Green's Functions, to calculate outgoing wave motion at nodes immediately outside of the artificial boundary, thereby eliminating unwanted reflection of the outgoing waves. A procedure is recommended to obtain required data from a commercially available software program. A modal method can be employed to maximize the efficiency of the analysis.Location: Kaprielian Hall (KAP) - 209
Audiences: Everyone Is Invited
Contact: Evangeline Reyes
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Fujita & Ogawa Revisited: An Agent-Based Modeling Approach
Wed, Jan 21, 2009 @ 02:00 PM - 03:00 PM
Sonny Astani Department of Civil and Environmental Engineering
Conferences, Lectures, & Seminars
Speaker: Eric J. Heikkila, Professor and Director of International Initiatives; School of Policy, Planning, and Development; Ralph & Goldy Lewis Hall; RGL 301D, University of Southern California, Los Angeles, CA 90089-0626The presentation is based on a paper by the same title, co-authored with Yiming Wang, forthcoming in Environment and Planning B. Absract:
This paper builds on and extends a classic paper (hereafter referred to as "F-O") published by Masahisa Fujita and Hideaki Ogawa in 1982. Their paper models the emergence of urban centers brought about by household and firm location decisions in the context of spatially differentiated labor and land market interactions. Their approach is an analytical one that seeks to characterize the equilibrium values of the system. In contrast, we employ an agent based modeling approach that seeks to replicate the individual household and firm behaviors that lead to equilibrium or non-equilibrium outcomes. The F-O model has little to say about what happens outside of equilibrium, while the ABM approach is pre-occupied with this question and is particularly well suited to address questions of path dependency and bounded rationality that lie well beyond the scope of the F-O original. We demonstrate that the urban outcomes that emerge depend critically upon the bidding behavior of agents and the institutional context within which their decisions are made.Location: Kaprielian Hall (KAP) - 209
Audiences: Everyone Is Invited
Contact: Evangeline Reyes
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Torsional Effects on the Inelastic Seismic Response of Structures
Thu, Jan 22, 2009 @ 01:00 PM - 04:00 PM
Sonny Astani Department of Civil and Environmental Engineering
Conferences, Lectures, & Seminars
Oral Defense by:Mehran Mansuri, Graduate Student, Civil and Environmental EngineeringAbstract:To evaluate inelastic torsional response of buildings due to different parameters such as unsymmetrical distribution of mass or lateral load resisting elements in the plan of the structure or yielding and inelastic behavior of resisting elements and loss of the resistance of such an element during an earthquake, a full three-dimensional nonlinear dynamic analysis is a powerful tool to evaluate such a nonlinear response.
The results of nonlinear dynamic analyses of two actual steel moment frame buildings that were damaged during the 1994 Northridge earthquake subjected to couple of different recorded ground motions from Northridge and Loma Prieta earthquakes are presented and the importance of different parameters such as discontinuity of lateral resisting elements, unsymmetrical distribution of mass or resistance in the plan of structure, intensity and frequency content of earthquake ground motions, accidental eccentricity as prescribed by code and the effect of geometric nonlinearity (P-Delta) on the inelastic lateral-torsional response of structures is discussed. Response parameters considered include lateral story displacement, Interstory drift index, plastic hinge rotation demand and torsional rotation of each floor.
The analysis procedures use three-dimensional nonlinear dynamic analytical models developed for the PERFORM 3-D computer program.
Study of the results for different models with different eccentricities clearly shows the effect of inelastic torsion in comparison with elastic torsion on the response of structures. The torsional rotation of floors considered as a main parameter of torsional response of the building has an average increase of 30 to 60 percent for material nonlinearity. By adding geometric nonlinearity (P-Delta), this increases 70 to 100 percent of elastic torsional rotation. This clearly shows the inelastic torsional response of structures may be significantly underestimated by a linear dynamic analysis, especially for large value of mass or stiffness eccentricity and intensity of the ground motion.
Location: Kaprielian Hall (KAP) - 209
Audiences: Everyone Is Invited
Contact: Evangeline Reyes