Confirmed speakers
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Dimitrios Lignos - École Polythechnique Fédérale de Lausanne
Earthquake-induced collapse risk and loss assessment of steel frame buildings ABSTRACT
Uncertainties associated with regional construction practices; the input loading and the dynamic response of structures impose the acceptance of a “tolerable” probability of structural collapse. This talk summarizes efforts to quantify with sufficient confidence the earthquake-induced collapse risk of steel frame buildings. State-of-the-art nonlinear deterioration models validated with carefully designed laboratory experiments are presented and utilized for this purpose. Implications associated with the building-specific loss assessment are also presented. Emphasis is placed in cases that steel frame buildings do not explicitly collapse but need to be demolished due to large residual deformations. The findings facilitate the decision-making process for stakeholders, engineers, and (re-) insurers to take proper pre-disaster measures to reduce the effects of seismic hazard for the best interest of our society. Short Biography
Prof. Lignos joined EPFL as a tenured Associate Professor in 2016 from McGill University. He holds a diploma from NTUA (2003), MSc (2004), PhD (2008), post-doc (2009) from Stanford University and a post-doc from Kyoto University (2010). His research involves integrated computational modeling and large-scale experimentation for the fundamental understanding and simulating structural collapse of steel structures under extreme loading as well as the development of metrics and technologies that promote resilient-based design. Prof. Lignos teaches courses in seismic design, nonlinear behavior and analysis of steel structures. He is the recipient of the 2013 ASCE State-of-the-Art in Civil Engineering Award and the 2014 Christophe Pierre Award for Research Excellence - Early Career. Professor Lignos acts as an Associate Editor for Metal Structures and Seismic Effects for the ASCE Journal of Structural Engineering. He serves as an acting member in various national and international technical committees for the further development of the seismic design provisions and the nonlinear modeling guidelines for steel structures in North America, Asia and Europe. |
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Theodore Karavasilis - University of Southampton
Seismic assessment of earthquake-resilient low-damage steel frames in OpenSees ABSTRACT
The presentation will discuss integrated numerical and experimental research carried out by the speaker and collaborators on different earthquake-resilient low-damage steel frames. Examples include steel frames with dissipative braces or post-tensioned beam-column and column-base joints. The talk will focus on the development of appropriate nonlinear models in OpenSees and their exploitation to design level seismic assessment, collapse resistance quantification, and economic seismic loss estimation. Particular emphasis will be given to the development, implementation, and calibration of practical hysteretic models, damage initiation/evolution laws, and fracture criteria for realistic numerical simulations. Gaps in knowledge and research needs in nonlinear model development for this particular class of steel structures will be highlighted. SHORT BIOGRAPHY
Full Professor (Chair in Structures and Structural Mechanics) at the University of Southampton. Previously, he held appointments at the University of Warwick (Assistant and Associate Professor; 2011-2015), University of Oxford (Lecturer; 2010), and Lehigh University (Post-Doctoral Researcher; 2007-2009). He holds a Diploma in Civil Engineering (2002), MSc in Structural Engineering (2004), and PhD in Seismic Design of Steel Structures (2007) from the University of Patras. Author or co-author of 32 papers in journals, 70 papers in conferences, and 4 chapters in books; member of national/international working groups (BSCA steel connections, IABSE WG7); member of the editorial boards of the Steel and Composite Structures and the Earthquakes and Structures Journals; consultant on the conception, design, and implementation of dissipative braces for tall steel buildings; and inventor of a demountable shear connector for precast steel-concrete composite bridges. |
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Asif Usmani - Hong Kong Polytechnic University
Insights on modelling structures in fire and recent developments in OpenSees ABSTRACT
This lecture will provide an overview of modelling structural response to fire, providing insights into the peculiarities of structural response to fire with a discussion of the common pitfalls in modelling it. The most onerous and still unresolved computational challenges that need the attention of the research community will be discussed next in the context of current trends in structures in fire research. The audience will also be provided with an update on the development work on OpenSees aimed at providing an integrated computational platform for simulation of structural response to realistic fires. This development will enable students, researchers and practitioners easy access to a user-friendly tool to carry out simple to moderately complex simulations of structural frames in fire. SHORT BIOGRAPHY
Asif Usmani has been Professor and Head of the Department of Buildings Services Engineering at Hong Kong Polytechnic University since August 2016. Before joining PolyU he was Professor of Structural Engineering at Brunel University London and at University of Edinburgh, Scotland, UK. The key theme of his research has been the development and application of computational methods for solving engineering problems, such as modelling of flow, heat transfer and solidification of castings in his early career to the simulation of the collapse of tall buildings in large fires more recently. His current work is focused on developing an integrated computational environment for simulation of structures in fire on the OpenSees platform. |
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Lu Xinzheng - Tsinghua University
Development and application of explicit methods in OpenSees for collapse simulation of large structures ABSTRACT
Research on the collapse mechanism of tall and super-tall buildings has become a critical issue in structural engineering. A high performance shear wall model (NLDKGQ) and a matrix solver (CuSP) were proposed, and successfully applied to conduct collapse simulation using OpenSees with the implicit method. However, the implicit method encountered numerical difficulties in convergence. Based on the leap-frog method and central difference method, an explicit method is herein proposed and integrated in OpenSees. Furthermore, a modal damping model is also integrated to address the stability problem of explicit method. The stability and reliability of the proposed method are validated, which provides an effective tool for further investigation on the collapse mechanism of large structures. SHORT BIOGRAPHY
Prof. Xinzheng Lu is a full Professor and the Head of the Institute of Disaster Prevention and Mitigation of Tsinghua University. His major research interests cover disaster prevention/mitigation and numerical simulation of civil engineering. He participated in the emergency earthquake reconnaissance after Wenchuan (2008), Yushu (2010), Lushan (2013), Ludian (2014) and Nepal earthquake (2015). Prof. Lu has published more than 200 papers in refereed journals, and 12 books. His publications have received more than 10700 citations, including more than 860 citations in Web of Science, and more than 1800 citations in Scopus. One of his publications was listed by Essential Science Indicators as “Highly Cited Papers”. Fourteen of his publications were listed as “Top 25 hottest articles” of Elsevier or “Most viewed papers” of ASCE. |
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Khalid Mosalam - Pacific Earthquake Engineering Research Center
Efficient Analytical and Hybrid Simulations using OpenSees ABSTRACT
This presentation covers several developments and applications related to analytical and hybrid simulations using OpenSees. The developments for efficient analytical simulations include a progressive collapse simulation implementation, use of adaptive time integration and nonlinear solution algorithms to overcome convergence challenges and development of a novel Lyapunov-based nonlinear solution algorithm with superior convergence features over regular Newton-Raphson and its variants. Applications of these developments on several buildings and bridges are presented. Second part of the presentation include hybrid simulations conducted on a broad range of structures, including bridges, substation electrical equipment, energy efficient structural insulated panels and curtain wall systems. Several developments, related to reduction of computation time and increase of control accuracy, are also discussed. SHORT BIOGRAPHY
Mosalam obtained his BS and MS from Cairo University and his PhD from Cornell University in Structural Engineering. In 1997, he joined the Department of CEE, UC-Berkeley where he is currently the Taisei Professor of Civil Engineering and the PEER Director. He conducts research on the performance and health monitoring of structures. He is active in areas of assessment and rehabilitation of essential facilities, e.g. bridges and electrical substations, and in research related to building energy efficiency and sustainability. His research covers large-scale computation and experimentation including hybrid simulation. He is the recipient of 2006 ASCE Huber civil engineering research prize, 2013 UC-Berkeley chancellor award for public services, and 2015 EERI outstanding paper award in Earthquake Spectra. He was a visiting professor at Kyoto University, Japan, METU, Turkey, and NTU, Singapore. He is a High-end Expert in Tongji University and is a core-PI for “Internet of Things & Societal Cyber Physical System Lab,” a part of the Tsinghua-Berkeley Shenzhen Institute. |
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Anastasios G. Sextos - University of Bristol / Aristotle University of Thessaloniki
Expert systems for advanced FE modelling of bridges and buildings using OpenSees ABSTRACT
SHORT BIOGRAPHY
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Dimitrios Vamvatsikos - National Technical University of Athens
A shared-filesystem-memory approach for running IDA in parallel over informal computer clusters ABSTRACT
Incremental Dynamic Analysis (IDA) is a computer-intensive approach for seismic performance assessment that employs nonlinear dynamic analysis under scaled ground-motion records. As it typically involves multiple runs of low-to-moderate complexity structural models, it can easily benefit from parallel processing. To achieve robust execution with efficient work partitioning, a multi-tier master–slave hierarchy is adopted, employing dynamic task generation and self-scheduling to spread work among any number of dissimilar processors. Using a centralized shared memory with file-locking to prevent race conditions, this scheme offers near-linear scaling while handling large workloads, old computers, unreliable power networks and incompetent system administrators with ease SHORT BIOGRAPHY
Dimitrios holds a Diploma in Civil Engineering from NTU Athens (1997), and an MSc and PhD from Stanford University (1998, 2002). He is now Assistant Professor at NTU Athens specializing in integrating structural modeling, computational techniques, probabilistic concepts and experimental results into a coherent framework for the performance evaluation of structures. His work in Incremental Dynamic Analysis has received wide attention, while he has also co-authored seismic assessment guidelines for buildings and has been a primary contributor to the seismic loss assessment methodology and the open-source risk-modeler’s toolkit adopted by the Global Earthquake Model Foundation. |
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André R. Barbosa - Oregon State University
Use of OpenSees for the Development of Physics-based Tsunami Fragility Functions ABSTRACT
An efficient probabilistic framework is presented for the development of physics and simulation-based parametrized tsunami fragility functions for building and bridge structures. The proposed framework is general and makes use of nonlinear finite element structural models that capture structural member failures in shear and the first-order second-moment (FOSM) reliability method. The application of the framework is illustrated with the development of parametrized fragility functions for an example reinforced concrete moment frame building designed to ASCE 7-05 and ACI 318-08 codes. In this application example, uncertainty in materials and building geometry are considered explicitly. Results indicate that explicit consideration of structural member failures is of paramount importance as the fragility functions based on global failure criteria that do not account for member failures tend to overpredict damage state capacities. Among the several sources of uncertainty considered, breakaway openings in the building are the dominant contributor to the uncertainty in the structural capacity. The estimation efficiency of several scalar and vector-valued intensity measures is evaluated using the logistic regression method. The intensity measures considered consist of inundation depth, flow velocity, specific momentum flux, kinematic moment of specific momentum flux and their interactions. The predictive power of vector-valued intensity measures is found to be higher than that of scalar intensity measures. Among the scalar intensity measures analyzed, those that combine information of inundation depth and flow velocity are identified to be the most efficient predictors of structural damage, and therefore are considered to be the preferred measures to characterize the intensity of tsunami hazards for practical applications. SHORT BIOGRAPHY
Dr. Barbosa is an Assistant Professor and Endowed Kearney Faculty Scholar at Oregon State University (OSU) where he joined after completion of his Ph.D. in 2011. Before pursuing his Ph.D. at UC San Diego, he worked for seven years as a structural designer in Lisbon, Portugal. At OSU, Dr. Barbosa's research focuses on the development of experimental testing programs and numerical tools and techniques geared towards improving structural performance and resilience of the built environment to multiple hazards. Studied within the research group are earthquakes, fire, and tsunami hazards. Structural materials addressed are reinforced concrete, timber, and steel. Dr. Barbosa is a researcher of the NIST-funded Center of Excellence for Community Resilience. He is also actively participating in several ASCE, ACI, and EERI technical committees related to reinforced concrete and timber structures. He was selected to be the ASCE SEI Wood Research Committee chair for the coming three years. He was also recently announced as the 2017 Daily Journal of Commerce Newsmaker, in Oregon, for his research on Cross-Laminated Timber. |
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Pedro Arduino - University of Washington
Recent advances in modeling soil-structure interaction problems using OpenSees ABSTRACT
In soil-pile interaction problems the pile response is best characterized using beam column type models to capture nonlinear deformation and force distributions. However, soil response is more effectively described using solid continuum based elements. The beam and solid combination poses a challenge for advanced modelling when frictional contact mechanisms and potential separation are to be considered. This research explores different ways to enhance soil-pile interaction modeling capabilities through the direct integration of beam-column and solid type models. The approaches are based on 3D frictional node-to-surface contact. Contrary to traditional contact implementations, the contact surface is defined using a semi-analytical representation of the three-dimensional surface of a discrete 3D-beam finite element. This allows for geotechnical models to simulate nonlinear pile behavior through the characterization of complex cross sectional properties such as reinforcement or defects by means of an advanced beam element with fiber cross section. Moreover, it enables the incorporation of size effects due to frictional resistance against rotation, or the effect of closely packed arrays of piles. As an application example a 3D finite element analysis of a bridge abutment and foundation system subjected to the kinematic demands of lateral spreading is considered. The selected bridge system corresponds to the Mataquito river bridge in Chile. The 2010 Maule earthquake caused extensive lateral spreading on both river banks at this site. Observations suggest that 3D effects may have contributed to reducing the structural demands placed on the abutment and foundations during lateral spreading. 3D models representing the existing site geometry and a plane strain approximation of the approach embankment are developed and used to estimate bending demands in the shaft foundations supporting the bridge abutment. SHORT BIOGRAPHY
Pedro Arduino is a professor at the University of Washington Department of Civil & Environmental Engineering. His primary research interests are in computational geomechanics with emphasis in constitutive modeling of soils, finite element analysis, and hazard analysis. Much of his current research is in the area of soil-structure interaction, performance-based earthquake engineering, and landslide and debris flow simulation. He has conducted research for the National Science Foundation, the Pacific Earthquake Engineering Research (PEER) Center, and the Washington State Department of Transportation (WSDOT). He is a member of the ASCE EM Inelasticity and ER Earth and Retaining Structures committees and served on the editorial board of the ASCE Journal of Geotechnical and Geo-environmental Engineering. Prof. Arduino is a member of GEER and was part of the reconnaissance team that visited Chile after the 2010 Maule, Chile, and 2011 Great Japan earthquakes. Arduino has also served as a consultant to private firms and government agencies in the U.S. and abroad. |
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Frank McKenna - University of California, Berkeley
OpenSees: Future Directions ABSTRACT
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