Editor’s Note

In this issue I continue my introduction of editorial board members beginning with Asghar Bhatti, Kim Rasmussen, and Colby Swan, all outgoing members who have done outstanding jobs during their respective three-year terms.

Asghar Bhatti (Fig. 1) is a professor in the Department of Civil and Environmental Engineering at the University of Iowa, Iowa City, where he started his academic career back in 1980 after obtaining his Ph.D. from the University of California, Berkeley, CA. He is a registered professional engineer in the State of Iowa. He has been a member of the American Society of Civil Engineers since 1981 and was elected a Fellow of ASCE in 1999. He is active in the analysis and computations area within the Structural Engineering Institute. He is also a long-term member of the American Concrete Institute and the American Society of Engineering Education. He has recently been appointed to the ACI 318 subcommittee charged with incorporating advanced analysis techniques into the ACI code. In ASEE he is currently serving a three-year term as the director of the Civil Engineering Division. His teaching and research interests are in the general areas of analysis, design, and optimization. In addition to various journal and conference publications he has authored two books on finite elements published by Wiley in 2005 and 2006 and one book on optimization published by Springer in 2000.

Dr. Kim Rasmussen (Fig. 2) is full professor in the School of Civil Engineering at the University of Sydney. His research areas are theoretical and experimental structural mechanics with particular expertise in steel structures, cold-formed steel structures, stainless steel structures, aluminum structures, and structural stability and analysis. He teaches advanced structural steel design to undergraduate and postgraduate students. He is chairman of the Standards Australia committees for Aluminum Structures and Steel Storage Racks and member of the Standards Australia committees for Steel Structures and Stainless Steel Structures. He is also chairman of the ASCE Standards Committee for Stainless Steel Structures. Dr. Rasmussen is member of the editorial boards of five international journals, including the ASCE Journal of Structural Engineering, the Journal of Constructional Steel Research and Thin-Walled Structures. His current research activities involve the testing, analysis, and design of scaffolding and steel storage rack structures, including the development of design methods based of system reliability analysis and advanced structural analysis. Dr. Rasmussen is currently head of the School of Civil Engineering and chairman of the Centre for Advanced Structural Engineering at the University of Sydney.

Colby Swan (Fig. 3) is professor of civil and environmental engineering at The University of Iowa where he has been teaching since earning a Ph.D. in civil engineering and operations research at Princeton University in 1993. His long-term research interests include many facets of computational solid mechanics and structural optimization. Much of his present research emphasis is directed at realistic modeling of clothing interactions with the human body using nonlinear shell theory and contact mechanics with the objective of designing improved protective clothing systems. He is a former chair of the ASCE/SEI Committee on Emerging Computing Technology and the incoming chair of the ASCE/SEI Committee on Optimal Structural Design for the period of 2009–2012. He was honored with the Robert and Virginia Wheeler Faculty Fellow of Engineering at the University of Iowa during 2004–2007 and is the corecipient of ASCE State-of-the-Art in Civil Engineering award in 2004.

Arzhang Alimoradi (Fig. 4) is a lecturer at the University of Southern California and a senior research engineer with John A. Martin and Associates in Los Angeles. He earned his Ph.D. from the University of Memphis in 2004 and is an alumnus of the International Institute of Earthquake Engineering and Seismology. Dr. Alimoradi is a registered professional engineer in the State of California, and recipient of the 2006 Outstanding Journal Paper Award from the Los Angeles Tall Buildings Structural Design Council. He has published many papers, reports, book chapters, and computer software in peer-reviewed venues. In 2006, he proposed, planned, and executed the EERI Annual Graphics Competition and has chaired the competition ever since. He has served the U.S. National Science Foundation as a panelist and reviewer of research proposals. Dr. Alimoradi has been on many national/international technical committees and boards including ASCE, EERI, Seismological Society of America, International Association for Computational Mechanics, and Structural Engineers Association of Southern California. His research focus is on structural dynamics and earthquake engineering, strong ground motion characterization, nonlinear dynamics and simulation of complex response, optimization and computational intelligence in structural mechanics, and system identification. His teaching and practice encompass a multidisciplinary combination of the research in solving critical engineering problems.

Rajesh P. Dhakal (Fig. 5) received his Bachelor’s degree in civil engineering from Tribhuvan University, Nepal, in 1993, with a gold medal; an M.E. degree from the Asian Institute of Technology (AIT) in Thailand in 1997, with another gold medal; and a Ph.D. in civil engineering from the University of Tokyo, Japan (2000). Currently, he is an associate professor (reader) in the Department of Civil and Natural Resources Engineering at the University of Canterbury, New Zealand. Prior to joining Canterbury in 2003, he worked as a civil engineer in Nepal (1993–1995) and as a research fellow in Nanyang Technological University, Singapore (2000–2003). His research interests lie in the areas of reinforced concrete, earthquake engineering, and structural fire engineering. To date, he has published two books and authored more than 130 technical papers in peer-reviewed publications. He has received several medals for his academic performance, three best paper prizes, and two outstanding researcher awards. His awards list includes the Aoyagi Award presented by AIT, Thailand; the Young Engineering Researcher Award bestowed by the University of Canterbury; and two prestigious awards presented by New Zealand Earthquake Commission and the New Zealand Society for Earthquake Engineering—the 2007 Ivan Skinner Award for advancement of earthquake engineering research in New Zealand, and the 2008 Otto Glogau Award for the best journal paper in earthquake engineering discipline. Currently, he is also an editorial board member of the civil engineering transactions of Scientia Iranica.

Akshay Gupta (Fig. 6) is a principal engineer and the director of AIR Worldwide’s Catastrophe Risk Engineering practice. He specializes in the areas of structural analysis and design and risk engineering with focus on assessment, mitigation, and repair of damage to structures arising from natural and manmade hazards. Dr. Gupta has more than $10\text{years}$ ’ experience in analysis and design of building structures and specialized structures (equipment, tanks, silos, flares, transmission lines, among others). He has investigated hundreds of structures damaged by the Northridge, Turkey, India, San Simeon, and Hawaii earthquakes, as well as Hurricanes Frances, Katrina, and Rita. His natural hazard risk analysis and mitigation work extends from individual buildings to portfolios of building structures to large industrial facilities at risk from earthquakes, high winds, or ocean storm surge. His work often includes finite-element modeling, linear and nonlinear static and dynamic analysis, physical testing of structures and components, and network modeling. Dr. Gupta holds a Bachelor’s degree in civil engineering from the Indian Institute of Technology, Delhi, India, and M.S. and Ph.D. degrees in structural engineering from Stanford University. Dr. Gupta is a member of various professional organizations and author of numerous technical papers and reports. He is a licensed professional engineer and is certified in the practice of structural engineering.

Twelve technical papers and a technical note have been selected from the following themes: reinforced concrete structures, metal structures, special design issues, structural identification, analysis and computation, and seismic effects. Also included is a discussion on a previously published paper and the authors’ closure.

“Experimental and Numerical Investigations on the Seismic Behavior of Lightly Reinforced Concrete Beam-Column Joints” are carried out by Li et al. Tests were conducted on five $3∕4$ -scale reinforced-concrete beam-column joints with and without slabs and with different column orientations. Additional numerical simulations with three-dimensional nonlinear finite-element models were also carried out to understand the effects of several critical factors, including column axial load, ratio of column depth to beam reinforcement bar diameter, and effective slab width. The “Effects of Bottom Reinforcement on Hysteretic Behavior of Posttensioned Flat Plate Connections” is experimentally investigated by Han et al. Test results from six 3/4-scaled specimens for interior posttensioned (PT) flat plate connections subjected to constant gravity loads and quasistatic reversed cyclic lateral loads indicate that the slab bottom reinforcement conforming to ACI-ASCE 352R.1 is not required to prevent collapse, but does significantly improve the hysteretic energy absorption capacity.

Bendito et al. propose a new equation for determining the “Inelastic Effective Length Factor of Nonsway Reinforced Concrete Columns.” The equation is obtained from a sensitivity analysis performed on a two-dimensional nonlinear finite-element numerical model that takes into account the inelastic behavior of the concrete columns (cracking, yielding, and second-order effects) and calibrated with 44 experimental tests. In “Macroscopic Elastic Constitutive Relationship of Cast-in-place Hollow-core Slabs” Jing-Zhong Xie proposes an effective sectional area method based on the characteristics of stress distribution for computing both the bending and axial compressive elastic modulus of cylindrical hollowed-core slabs. The so-called transverse-rib-effect phenomenon in which the transverse rib of hollow-core slab may lead to macroscopic stiffness increase is demonstrated.

In “Performance of Steel-Concrete Composite Beams under Combined Bending and Torsion” Nie et al. present findings from tests on eleven steel-concrete composite beams, four under pure torsion and seven under combined bending and torsion. Test results show that the reinforced concrete slab contributes mainly to the torsional resistance of composite beams and the contribution of steel joists to torsion is negligible. However, the steel joist restrains the concrete slab from deforming longitudinally, which enhances the torsional strength of the concrete slab. A three-dimensional behavioral truss model capable of analyzing composite beam sections subjected to the combined bending and torsion is presented. The “Lateral Buckling Strength of Simply Supported LiteSteel Beams Subject to Moment Gradient Effects” is evaluated by Kurniawan and Mahendran through detailed finite-element simulations. The suitability of the current design methods is discussed and design recommendations for simply supported LSBs subject to moment gradient effects are proposed.

Omer et al. investigate the “Failure of Lightly Reinforced Concrete Floor Slabs with Planar Edge Restraints under Fire.” The proposed model accounts for membrane action that occurs at large slab deformations and presents a failure criterion based on rupture of the steel reinforcement and accounts for the influence of bond between steel and concrete on reinforcement rupture. The “Structural Fire Safety of Circular Concrete Railroad Tunnel Linings” is investigated analytically by Caner and Böncü in terms of reduction in service load safety due to time and temperature-dependent material degradation and increase in load demand in a tunnel fire. Results of the study suggest that tunnel bored machine (TBM) tunnels in soft soil can have a better fire performance compared to the ones located at stiff conditions with similar initial loading.

A new static-based method for “Structural Damage Detection of Cable-Stayed Bridges Using Changes in Cable Forces and Model Updating” is presented by Hua et al. Damage identification is formulated as an optimization problem in which the cable force error between measurement results and analytical model predictions is minimized. The validity of the method is illustrated by numerical studies of damage detection of the cable-stayed Sutong Bridge. A simplified system identification procedure is developed by Huang et al. for “Physical-Parameter Identification of Base-isolated Buildings Using Backbone Curves.” The hysteretic model is characterized by a backbone curve by which the multivalued restoring force is transformed into a single-valued function. The proposed algorithm extracts individually the physical parameters of each floor as well as the bearing system that are essential in structural health monitoring.

“Frame Element for Metallic Shear-Yielding Members under Cyclic Loading” is developed by Saritas and Filippou based on a three-field variational formulation with independent displacement, stress, and strain fields. In contrast to existing concentrated plasticity models that require parameter calibration for different loading and support conditions, the proposed model is general, and does not suffer from shear locking and does not require mesh refinement for the accurate representation of inelastic member deformations.

In “Experimental Studies on Real-Time Testing of Structures with Elastomeric Dampers” Mercan and Ricles utilize a Bode diagram of the complete real-time testing system to design a velocity feed forward component that improves the tracking performance of the command displacements by the hydraulic actuator. The stability limits associated with a time delay for the tests are discussed and compared with delays that occurred in the tests.

In “Rational Fraction Polynomial Method and Random Decrement Technique for Force-Excited Acceleration Responses” Ku and Tamura address a parameter identification problem of a linear dynamic system resulting from forced acceleration responses when input forces are unknown. The procedure applies the mode indicator function, the complex mode indication function, and the rational fraction polynomial method to identify the modal parameters of the dynamic system from the frequency response functions of the random decrement signatures.

The issue concludes with a discussion by Aristizabal-Ochoa on a paper by Dym and Williams on “Estimating Fundamental Frequencies of Tall Buildings” which appeared in October 2007. The discusser argues that the two-dimensional beam model used in the formulation is inadequate to account for factors such as foundation compliance, the rotational inertia along the height of the building, and second-order effects. It is suggested that the cantilever Timoshenko shear beam-column overcomes these deficiencies and is more suitable for the proposed application. In their closure, the authors clarify that the objective of the study was to rapidly estimate the natural frequency of high-rise buildings and not necessarily to provide a comprehensive and all-inclusive model. It is also pointed out that the discusser did not compare results obtained from his model to available empirical data; hence the advantage of the proposed formulation is not validated.