Editor’s Note

A two-part paper by Sri Sritharan examining the behavior and design of bridge joints opens this issue of the Journal. In “Strut-and-tie analysis of bridge tee joints subjected to seismic actions,” Sritharan identifies certain shortcomings in the widely used force transfer model for bridge tee joints. It is demonstrated that modeling joint shear as a component of the total force transfer across the joint enables utilization of beam reinforcement for the force transfer, thus reducing the required shear reinforcement and improving constructability of the joint. In the second paper, “An improved seismic design procedure for concrete bridge joints” is proposed. Utilizing a new modified form of the force transfer model, Sritharan develops a methodology for the seismic design of tee and knee joints in bridge structures. “Factors contributing to bridge-embankment interaction” by Price and Eberhard investigates important phenomena that contribute to interaction effects between bridges and approach embankments during earthquakes. The study finds that three-dimensional embankment effects and modeling of soil behavior are significant contributors while the response is generally insensitive to embankment scattering and changes in embankment geometry.

An integrated analysis and design method to estimate inelastic strength and deformation demands is described by Park and Eom in “Direct inelastic earthquake design using secant stiffness.” The methodology facilitates design of members to achieve specified strength and ductility-demand levels. Tremblay and Poncet investigate the “Seismic performance of concentrically braced steel frames in multistory buildings with mass irregularity.” It is concluded that mass irregularity has limited negative impact on the seismic performance of structures designed with the static analysis method. The reduction in performance can be improved by utilizing a dynamic analysis method in design. An approach that allows for consideration of nonlinear connection response using commonly available elastic analysis software is developed by Surovek, White, and Leon in “Direct analysis for design evaluation of partially-restrained steel framing systems.” The proposed procedure allows for stability to be checked using AISC-LRFD interaction equations, thereby eliminating the need for determining effective length factors.

An “Experimental investigation of cold-formed steel lipped angle concentrically loaded compression members” is presented by Young. The test strengths are compared to North American and Australian∕New Zealand specifications and found to be generally conservative for the majority of configurations. Martinez et al. study the “Behavior of harp bracings in rigid frame metallic bays.” With these special on-roof bracings, the loads received by the columns are partially transmitted to the endwall frame; hence, the columns require smaller section size and foundations. Static push-out and full-scale bending tests are carried out by Clouston, Bathon, and Schreyer to assess the “Shear and bending performance of a novel wood concrete composite system.” This new system is shown to be superior to alternative wood–concrete composite systems in terms of its structural efficiency and constructability.

A new generalized model that includes the effect of prestressing tendons and considers variable depth stress fields applied to the cross section is proposed by Recupero, D’Aveni, and Ghersi to develop “M-V interaction domains for prestressed concrete beams.” The model is validated with experimental data and used in the design of a pretensioned bridge beam to evaluate the additional reinforcement necessary in the flanges as a function of the web reinforcement. In “Explaining the riddle of tension stiffening models for shear panel experiments,” Bentz compares the performance of three tension-stiffening relationships and concludes that the variation in the computed behavior using the different equations can be explained by different bond conditions of the specimens tested to calibrate the original relationships. A new expression is derived to quantify this effect and sample results demonstrate the effectiveness of the proposed relationship. Cho, Kwon and Spacone propose an “Analytical model of concrete-filled FRP tubes based on multiaxial constitutive laws.” An orthotropic hypoelasticity-based constitutive law defined in triaxial stress space is used for concrete and the confinement-induced concrete strength enhancement is computed from a four-parameter failure surface. The model is verified against available experimental results on concrete-filled FRP cylinders.

Findings from a study examining the time-effect factors for steel-doweled wood connections are described by Marlor and Bulleit in “Load-duration behavior of wood connections.” Two cumulative-damage models are calibrated to long-term tests conducted on small-scale wood connection specimens, and design recommendations are made for time-effect factors for doweled connectors. “Reliability of light-frame wall systems subject to combined axial and transverse loads” is investigated by Rosowsky, Yu, and Bulleit. An experimentally validated analytical model is utilized in a Monte Carlo simulation to derive reliability indices of light-frame wall systems in high snow- and hurricane-prone regions in the United States.

The final two technical papers in this issue deal with the subject of system identification and damage detection. A finite-element model updating technique is applied by Unger, Teughels, and Roeck for “Damage detection of a prestressed concrete beam using modal strains.” An iterative sensitivity-based algorithm is used to solve an optimization problem that attempts to minimize the error between experimental modal data and corresponding analytical predictions. Another identification technique is presented by Lee and Wooh in “Waveform-based identification of structural damage using the combined FEM and microgenetic algorithms.” It is demonstrated that the proposed procedure can detect a multiple existence of damaged elements and also characterize their location and severity.

This issue also includes a set of discussions on a paper by Zarghamee et al. that appeared in January 2004 issue of the Journal. The first discussion is by Andrew Romer, who agrees with the authors that the current AWWA procedure is inadequate but doubts the validity of relying on the adjacent soil to provide stability to the pipe. The next discussion is by William Dana who raises several questions about the details of the formulation and modeling and seeks clarification on the design procedure proposed by the authors. The third and final discussion is by John Scarino who also raises numerous issues on the authors’ approach and contends that any design procedure involving soil–structure interactions cannot be justified by mathematical modeling alone. The original writers provide closure to the subject by addressing all of the concerns raised by the discussers and indicate that while their attempt has provided a simple yet rational approach to the problem, additional experimental and analytical work is needed to advance the design procedure.

Bhattacharya, B. et al. (2005). “Reliability-based load and resistance factor rating using in-service data.” J. Bridge Eng., 10(5).

Cheng, C.-T., Mo, Y. L., and Yeh, Y.-K. (2005). “Evaluation of as-built, retrofitted and repaired shear-critical hollow bridge columns under earthquake-type loading.” J. Bridge Eng., 10(5).

Lehman, D. E., Roeder, C. W., and Larsen, R. A. (2005). “Design of cotton duck bridge bearing pads.” J. Bridge Eng., 10(5).