Editor’s Note

Many of you, particularly if you submitted a paper for consideration to the Journal, would have interacted with Johanna Reinhart and/or Jackie Perry. Together they were part of a great team at ASCE, contributing significantly to its success and stature. Earlier this year, Jackie moved on to assume a new position in ASCE while Johanna announced her retirement after having been with ASCE, for over $10\text{years}$ . Associate Editors, past and present, will remember the enthusiasm, energy, and professionalism with which they ran journal operations. On behalf of all of us, I would like to take this opportunity to express my sincerest thanks to Johanna and Jackie for their contributions to ASCE in general and the Journal of Structural Engineering in particular. They both will be missed.

Let me now welcome Melissa Junior who replaces Johanna Reinhart as Journals Director and Elizabeth Horowitz who took over from Jackie Perry as Managing Editor of the Journals division. I look forward to working with them as we continue to address some of the challenges we face to reduce median turnaround times, which in my opinion, are still far from satisfactory.

During 2007, six Associate Editors retired after completing their terms: Rob Chai, Scott Civjan, Reginald DesRoches, Sanj Malushte, Michael Symans, and Donald White. Thank you all for your untiring efforts to maintain the quality of the Journal. A belated welcome to Sankaran Mahadevan from Vanderbilt University and Kim Rasmussen from the University of Sydney. Joining the editorial board for 2008 are Amjad Aref from the University of Buffalo, Rajesh Dhakal from the University of Canterbury, Judy Liu from Purdue, and Amit Kanvinde from the University of California at Davis.

I also wish to take this opportunity to thank my editorial board who continue to work hard identifying the most qualified reviewers and ensuring that papers that make a contribution to the state of the art are singled out for publication as expeditiously as possible. Thanks also to our excellent pool of reviewers—all of whom are acknowledged in this issue.

This concluding issue of the Journal for 2007 begins with a Forum on an interesting issue raised by Morris Ojalvo related to pure torsion and the Wagner hypothesis. I have selected to publish this opinion with the objective of initiating a discussion should readers care to share their views on the subject.

The leadoff theme for this issue is Structural Safety and Reliability. This is followed by a paper on fire response of tall buildings. The next group of papers comprises Dynamic and Seismic Effects followed by Structural Identification and Control, Analysis and Computation, and Structural Optimization. Papers on Metal, Concrete, and Wood Structures complete the issue.

An innovative methodology to consider the spatial correlation of a wire’s strength over the wire’s length is proposed by Shi et al. in “Random Field-Based Approach for Strength Evaluation of Suspension Bridge Cables.” The wire strength is modeled as a non-Gaussian random field along its length. The capabilities of the proposed methodology are demonstrated through an application involving an experimental data set of wire segments extracted from the Williamsburg Bridge. A procedure for estimating the tensile strength of a cable composed of parallel wires at different corrosion stages is also presented.

A new approach based on interval arithmetic for the treatment of parameter uncertainty for linear static structural mechanics problems is proposed by Muhanna et al. in “Combined Axial and Bending Stiffness in Interval Finite-Element Methods.” An element-by-element technique is used to reduce overestimation, thereby enabling a sharp enclosure of the system response. Numerical examples are presented to illustrate the process. In the next paper, Padgett and DesRoches examine the “Sensitivity of Seismic Response and Fragility to Parameter Uncertainty” for a class of retrofitted bridges. The study finds that savings in simulation and computational effort in fragility estimation may be achieved through a preliminary screening of modeling parameters. However, the propagation of uncertainty in modeling parameters tends to be overshadowed by the uncertainty in the ground motion and the base geometry of the structural class.

The effects of fire spread on long-span truss floor systems comparable to the type of construction in the World Trade Center towers is the focus of the paper “Structural Response of Tall Buildings to Multiple Floor Fires” by Flint et al. The local and global response of the model is described over the course of a concurrent fire on 3 floors reaching a peak compartment temperature of $800°\mathrm{C}$ . Findings from the analysis suggest that the resulting large displacements in the floor system will not lead to failure; however, the interaction of the deflected floors with exterior or perimeter columns may lead to structural collapse. It is concluded that additional structural members such as hat trusses that allow redistribution of loads away from exterior columns have a significant beneficial effect on the robustness of the structure.

Şimşek and Kocatürk conduct “Dynamic Analysis of Eccentrically Prestressed Damped Beam under Moving Harmonic Force Using Higher Order Shear Deformation Theory.” The tendon is assumed to be straight and unbonded to the concrete. Lagrange equations are used to reduce the problem to a system of differential equations that are solved by direct integration. The effects of eccentric and axial prestess forces, velocity of the moving harmonic force, and viscous damping of the material are investigated.

In an effort to explore how ambient vibrations based on routine traffic excitation can be used as part of a long-term bridge monitoring approach, Liu and DeWolf study the “Effect of Temperature on Modal Variability of a Curved Concrete Bridge under Ambient Loads.” A database developed over a $5\text{-}\text{year}$ period is used to evaluate how temperature variations influence the modal properties. Results show that the variability of measured model parameters due to temperature should be considered and quantified prior to the establishment of a baseline for use in damage assessment algorithms. The study of “Self-Diagnosis and Self- Repair of an Active Tensegrity Structure” in situations of partially defined loading and damage events is described by Adam and Smith. The response of the structure to a load and damage is measured and compared to candidate self-diagnosis solutions. These solutions are employed to compute control commands of shape control and self-repair for the structure. Self-repairing control commands are computed using a multiobjective approach that increases stiffness and decrease stresses with respect to the damaged state.

Yang et al. propose a “Rigid Element Approach for Deriving the Geometric Stiffness of Curved Beams for Use in Buckling Analysis.” Typically, a geometric stiffness matrix is used in conjunction with an elastic stiffness matrix for buckling analysis. In the proposed approach, no assumptions are made for the kinematic behavior of curved beams. Mesh refinement is shown to lead to improved convergence. The robustness of the method is demonstrated through the solution of several benchmark problems.

Frangapol and Liu present a procedure for “Bridge Network Maintenance Optimization Using Stochastic Dynamic Programming.” The multiobjective optimization problem is solved in two phases. In the first phase, optimal maintenance plans are identified for individual bridges while in Phase II, limited annual maintenance budgets are allocated in such a way that the identified optimal maintenance plans for individual bridges can be satisfied for as many bridges as possible. A single-objective formulation derived from multiple attribute utility theory and weight assignments derived from reliability importance factors is developed and solved using a binary integer programming algorithm.

Tong et al. investigate the “Fatigue Strength of End-Coped Crane Runway Girders” through a combined analytical and experimental study. Finite-element analyses were carried out to investigate stress concentration at the coped ends of typical crane girders. Analytical results indicate that stress concentration decreased with increasing cope radius and decreasing section depth, which is consistent with measured field data. Based on the analytical study and fatigue testing of $1∕5$ -scaled end-coped girder specimens, the authors recommend a fatigue limit of 2 million cycles at a maximum principal stress of $103\mathrm{MPa}$ . Findings from an analytical study in conjunction with experimental tests are reported in “Behavior and Design of Seam-Welded Stainless Steel Circular Hollow Section Flexural Members” by Kiymaz, Coskun, and Cosgun. The strength results obtained from testing and finite-element simulations are compared with American, Australian, and European specification for cold-formed stainless-steel structures. It is shown that significant improvements are possible for cross-sectional slenderness limits provided by current specifications.

Results from “Large-Scale Testing of a Replaceable ‘Fuse’ Steel Coupling Beam” are presented by Fortney et al. The coupling beam is designed and detailed based on the authors’ previous recommendations. The innovative “fuse” steel beam provides an added feature in that postdamage repair and/or replacement difficulties and expenses are minimized. Kim and Leon investigate whether moment-resisting frames designed by the wind moment frame (WMF) method are adequate to resist the increased demand on lateral resistance required by modern seismic codes in their paper “Seismic Performance of PR Frames in Mid-America Earthquake Region.” Utilizing FEMA $273∕356$ criteria, the study finds that PR frames satisfy selected performance objectives with 99% confidence for global performance limits.

The full elastoplastic behavior of confined columns is analytically derived by Eid et al. in “Elastoplastic Confinement Model for Circular Concrete Columns.” The solution to the partially confined RC column in the elastoplastic range is derived by replacing the discrete lateral reinforcement with an equivalent tube, and the Drucker-Prager (DP) yield criterion is applied to the concrete behavior in the plastic range. It is shown that the proposed model simulates the behavior of concrete columns partially confined by steel ties and of columns fully confined by fiber-reinforced polymer sheets.

The “Performance of Shear Walls with Diagonal or Transverse Lumber Sheathing” is reported by Ni and Karacabeyli through 16 full-scale tests. The effects of hold-downs, vertical load, and lumber sheathing width on in-plane shear capacity are investigated. The testing also examined whether shear resistance is cumulative when diagonal or transverse sheathing is used on one side and gypsum wallboard panels on the other. Results show that with proper hold-down connections, the design values in the U.S. and Canadian codes are appropriate for shear walls with lumber sheathing.

The “Benefits of Using Puddled HSC with Fibers in Slabs to Transmit HSC Column Loads” are demonstrated by Lee et al. Results of compression tests performed on two slab-column specimens and four isolated columns without slabs are reported. Predictions using current North American code approaches are compared to experimental results.

A closed-form solution is developed by Ghosh and Basu as “Alternative Approach to Optimal Tuning Parameter of Liquid Column Damper for Seismic Applications.” The closed-form expression is based on the extension of the theory of “fixed-point” frequencies for a classical undamped system to a damped nonlinear LCD system. The values of optimum tuning ration have been compared to those obtained from standard theory for the specific case of white noise input.

This issue concludes with a discussion by Tena-Colunga on a paper by Neuenhofer on “Lateral Stiffness of Shear Walls with Openings.” The discusser agrees that the simplified hand calculation method is unreliable, sharing his own calculations and results and pointing to existing literature that also concur with these findings.