Editor’s Note

Three papers on the theme of optimization lead off this issue of the Journal. Camp, Bichon, and Stovall develop a procedure for “Design of Steel Frames Using Ant Colony Optimization.” The design is mapped into a modified traveling salesman problem (TSP) where the configuration of the TSP network reflects the structural topology and the length of the TSP tour corresponds to the weight of the frame. A method for “Cost Optimization of Prestressed Concrete Bridges” is presented by Sirca and Adeli. The problem is formulated as a mixed-integer discrete nonlinear programming problem and solved using a neural dynamics model. The third paper by Gupta, Kripakaran, Mahinthakumar, and Baugh describes computational approaches used in a “GA-Based Decision Support for Optimizing Seismic Response of Piping Systems.” Based on a genetic algorithm that uses finite-element analyses, an efficient crossover scheme is proposed for generating trade-off curves and the approach is validated with respect to optimal solutions obtained by enumeration.

“Approximate Solutions for the Shape of Submerged Funicular Arches with Selfweight” is proposed by Chai and Wang. Cartesian coordinates of the funicular arch are expressed as analytical functions of the tangent angle, which avoids the need to solve a set of differential equations. Museros and Alarcon investigate the “Influence of the Second Bending Mode on the Response of High-Speed Bridges at Resonance” and conclude that the usual assumption that peak vertical displacements are controlled by the fundamental mode is generally true.

A procedure for evaluating statistical measures of deformation is presented by Dinh and Ichinose in “Probabilistic Estimation of Seismic Story Drifts in Reinforced-Concrete Buildings.” The proposed procedure is validated with dynamic response analyses of 9-story wall and frame structures using 36 records from 14 different earthquakes. The results of large-scale experiments to examine the “Seismic Performance of Pile-Wharf Connections” are reported by Roeder, Graff, Soderstrom, and Yoo. Precast concrete piles are found to be stronger than extended pile sections but they degrade more rapidly. Similarly, axial load on the pile improves its resistance but increases the degradation that significantly reduces the inelastic-pushover resistance and increases inelastic-dynamic demands of the system.

Garlock, Ricles, and Sause present findings from “Experimental Studies on Full-Scale Posttensioned Steel Connections.” Results indicate that the posttensioned connection, consisting of high strength strands that run parallel to the beam, possesses good energy dissipation and ductility. Closed-form expressions are derived to predict the connection response and are shown to compare well with experimental results. A physically based yield line model to predict the moment capacity of bolted extended endplate eave connections is proposed by Mofid, Mohammadi, and McCabe in “Analytical Approach on Endplate Connection: Ultimate and Yielding Moment.” The model is validated with experimental results. Ellobody and Young propose an efficient and accurate finite-element model to understand the “Behavior of Cold-Formed Steel Plain Angle Columns.” The effects of initial local and overall geometric imperfections and material nonlinearities of flat and corner portions of the angle sections are incorporated into the model. The study investigates failure loads, buckling modes, and load-shortening curves of plain angle columns.

A two-part paper investigating the buckling and torsion of steel angle beams is presented by Trahair. The first paper examines the behavior of equal angle beams, while the second paper deals with unequal angle sections. The writer develops an approximate method for predicting the second-order deflections and twist rotations of both types of beams under major axis bending and torsion. The elastic flexural buckling of doubly symmetric elements is analyzed by Trahair and Rasmussen in “Finite-Element Analysis of the Flexural Buckling of Columns with Oblique Restraints.” The nature of oblique restraints and their effects on the elastic buckling of columns is discussed.

Xiao, He, and Choi present a study to introduce and experimentally validate “Confined Concrete-Filled Tubular (CCFT) Columns.” The writers propose a new system aimed at controlling the local buckling of the steel tube and confining the concrete in the potential plastic hinge region. Experimental studies demonstrate the effectiveness of the system for seismic loading. “Assessment of a Steel-Free FRP-Composite Modular Bridge System” is described by Cheng, Zhao, Karbharia, Hegemeir, and Seible. The response of individual components and a two-girder deck assemblage are characterized through full-scale tests and analytical predictions based on laminated beam theory are shown to compare well with experimental results.

The final technical paper in this issue provides “Probabilistic Descriptions of Wind Effects and Wind Load Factors for Database-Assisted Design.” Written by Diniz and Simiu, the procedure accounts for inherent randomness in the estimation of peaks and relevant wind-related knowledge uncertainties. The writers contend that consideration of the uncertainties in isolation can be misleading for estimating peak effects. This issue also contains a technical note by Tjhin, Aschheim, and Hernandez-Montes on a pushover-analysis procedure for establishing “Estimates of Peak Roof Displacement Using Equivalent SDOF Systems.”

The issue concludes with two discussions and closures on previously published papers. The first discussion is by Bennett and Flanagan on a paper by Asteris dealing with “Lateral Stiffness of Brick Masonry Infilled Plane Frames.” The discusser argues that the analysis does not allow for sliding of the interface and that there is a significant discrepancy between analytical and experimental results of an infilled frames tested by the discussers. The writer of the original paper points out that while a steel frame was used by the discussers, the model was proposed for infills in concrete frames. The second discussion is by Lee on a paper by Gasparini that appeared in the October 2002 issue of the Journal. The discussion centers on Turner’s unique design with low-steel reinforcement, the significant contributions of Turner in concrete design, the flexural strength of Turner’s flat slabs, and whether any load tests of Turner’s flat slabs were carried out to failure. The writer responds that failure tests were unlikely and that current provisions for two-way slab design do not make for reasonable comparisons with Turner’s slabs.

Barr, P. J., Stanton, J. F., and Eberhard, M. O. (2005). “Effects of temperature variations on precast, prestressed concrete bridge girders.” J. Bridge Eng., 10(1).

Bernal, D. (2005). “Closely spaced roots and defectiveness in second order systems.” J. Eng. Mech., 131(3).

Blekherman, A. N. (2005). “Swaying of pedestrian bridges.” J. Bridge Eng., 10(1).

Furukawa, T., Ito, M., Izawa, K., and Noori, M. N. (2005). “System identification of base-isolated building using seismic response data.” J. Eng. Mech., 131(3).

Hanagan, L.M. (2005). “Walking-induced floor vibration case studies.” J. Archit. Eng., 10(1).

Hanzlik, P., Diniz, S., Grazini, A., Grigoriu, M., and Simiu, E. (2005). “Building orientation and wind effects estimation.” J. Eng. Mech., 131(3).

Kim, H., and Adeli, H. (2005). “Wavelet-hybrid feedback LMS algorithm for robust control of cable-stayed bridges.” J. Bridge Eng., 10(1).

Li, Z., Swanson, J. A., Helmicki, A. J., and Hunt, V. J. (2005). “Modal contribution coefficients in bridge condition evaluation.” J. Bridge Eng., 10(1).

Liu, J. L. (2005). “Exact solution of nonlinear hysteretic responses using complex mode superposition method and its application to base-isolated structures.” J. Eng. Mech., 131(3).

Minor, E. (2005). “Lessons learned from failures of the building envelop in windstorms.” J. Archit. Eng., 10(1).

Nie, J., and Ellingwood, B. (2005). “FE-based structural reliability assessment using efficient directional simulation.” J. Eng. Mech., 131(3).

Yang, J. N., and Lin, S. (2005). “Identification of parametric variations of structures based on least-square estimation and adaptive tracking technique.” J. Eng. Mech., 131(3).

Zhao, J., Shield, C., French, C., and Posbergh, T. (2005). “Nonlinear system modeling and velocity feedback compensation for EFT.” J. Eng. Mech., 131(3).