Editor’s Note

The first set of papers to lead off this issue of the Journal deals with modeling issues in reinforced concrete and masonry structures. They are followed by two papers that examine the response of steel-concrete composite structures. Papers on structural identification include a study of fiber optic sensors and a finite-element model updating methodology. Three papers on seismic effects, one on wind effects, and one on analysis and computation wrap up this issue of the Journal.

On the basis of results from uniaxial, monotonic, compression loading tests of 108 large-scale specimens, Konstantinidis et al. develop an “Analytical Stress-Strain Model for High-Strength Concrete Members under Cyclic Loading.” The model accounts for the effects of concrete compressive strength, volumetric ratio of transverse reinforcement, yield strength of ties, tie spacing, and tie pattern. The model is implemented in a finite-element program to analyze high-strength concrete members subjected to cyclic loading. Comparisons with test data indicate that the proposed model provides a good fit for a range of observed hysteretic behavior. A model that estimates “Short- and Long-Term Deflections in Reinforced, Prestressed, and Composite Concrete Beams” subjected to bending about any transverse axis without torsion is developed by Rodriguez–Gutierrez and Aristizabal–Ochoa. The effects of creep, shrinkage, and tension stiffening in the concrete are incorporated. The proposed model is capable of predicting with reasonable accuracy the nonlinear load-deflection response of concrete beams reinforced with reinforcing steel, prestressed or posttensioned strands, or composites. A simulation model that incorporates the effects of geometric and material nonlinearity resulting from cracking and crushing of masonry and yielding of prestressing steel is developed by Baqi and Bhandari to predict “Postcracking Behavior of Prestressed Masonry in Flexure.” The proposed model is suitable estimating in-plane response of both bonded and unbonded prestressed masonry structures. The model is validated by comparing theoretically computed values in both the pre- and postcracked range with available experimental data.

Results of testing on a new composite beam composed of a structural tee, a horizontal top stud, precast concrete, stirrups, and cast-in-place concrete slab are reported by Ju et al. in “Experimental Evaluation of New Concrete Encased Steel Composite Beam to Steel Column Joint.” Three types of the proposed system are tested under cyclic loading. The primary test parameters are the spacing of the transverse bars in the slab and the ratio of the width of the bar spacing to bracket length. On the basis of recorded load-displacement responses and observed failure patterns, it is concluded that the proposed system is a viable alternative for seismic moment-resisting frames. An “Experimental and Analytical Study of Prestressed Steel–Concrete Composite Beams Considering Slip Effect” is presented by Nie et al. An analytical model is developed that accounts for the slip effect between steel and concrete interface and the increase of the prestressing tendon force with increase in loading. A simplified reduced stiffness method is then proposed for estimating the deflection of prestressed composite beams. The authors find that including the slip effect in calculating the deflection and yield capacity of these composite sections can significantly improve the accuracy of analytical predictions.

Jacobs et al. present findings from “Testing of a Prestressed Concrete Girder to Study the Enhanced Performance of Monitoring by Integrating Optical Fiber Sensors.” Results from large-scale testing demonstrate the feasibility of fiber Bragg grating strain sensors for both static and dynamic monitoring. Although a perceptible decrease in eigenfrequencies is observed with increasing load, significant shifts are measured only in the postyield range. A distinct zone of high curvature corresponding to the formation of a plastic hinge is also detected. Results of a combined experimental and analytical approach to examine “Modal Testing and Finite-Element Model Updating of a Lively Open-Plan Composite Building Floor” are presented by Pavic et al. The methodology incorporates state-of-the-art finite-element (FE) modeling, experimental measurements, model tuning, and sensitivity-based automatic model updating. The authors demonstrate that a fairly complex FE model developed on the basis of best engineering judgment can yield natural frequencies within 10 to 15% of instrumented measurements. Errors were attributed to both overestimation and underestimation of the stiffness of the main composite beams, depending on location, which in turn was a result of uncertainties related to cracking in the lightweight concrete, effects of nonstructural elements, and the uneven distribution of mass and stiffness in a real-world fully furnished floor during daytime operation.

Giuriani and Gubana investigate an alternative solution to avoid oversized foundations in “Underground Box Structure as a Foundation for Shear Walls in Seismic Resistant Buildings.” Elements constituting the box structure, such as the peripheral walls, are already part of the actual building; hence, the foundation design becomes an integral part of the overall system design. The panels are appropriately underreinforced to allow plastic yielding, whereas the ribs are stiffened and strengthened to improve shear flow along the rib-to-panel interface. Although the analytical solution presented in the paper refers to a rectangular box, the proposed concept can be extended to complex plan shapes.

“Probabilistic Constant-Strength Ductility Demand Spectra,” by Yi et al., offers an approach to estimate both the mean and standard deviation of the ductility demand, given the normalized strength and fundamental building period. The proposed spectra permit the treatment of frequency content and ground motion intensity measure separately and describe the variation of a structure from elastic to inelastic state as a function of peak ground acceleration. This enables its application in stochastic seismic displacement analysis and probabilistic seismic demand analysis. A detailed seismic performance assessment procedure is developed by Erduran and Yakut in “Vulnerability Assessment of Reinforced Concrete Moment Resisting Frame Buildings” with masonry infills. The procedure is based on component damage functions that are developed in terms of interstory drift ratios. These component functions are then synthesized to determine story level and overall building performance states. The procedure is calibrated to the observed performance of three buildings subjected to the recent earthquakes in Turkey. The authors conclude that the methodology can reasonably predict damage states in both the primary building components and in the overall building following a seismic event.

Duthinh and Fritz investigate the compliance of buildings to meet the requirements implicit in recent versions of ASCE standards in “Safety Evaluation of Low-Rise Steel Structures under Wind Loads by Nonlinear Database-Assisted Technique.” An improved nonlinear database-assisted method for estimating ultimate capacity under wind loads is proposed. This method can be used to increase safety under wind loads with little or no increase in material consumption or to save material and energy while maintaining wind-resisting capacity. The authors conclude that frames designed to ASCE 7–93 and allowable strength design generally satisfy ASCE 7–02 requirements with respect to wind loading but that the safety level is relatively low and could be further enhanced at very low cost.

A new corotational subparametric formulation consisting of a four-noded element with quadratic hierarchic shape function and capable of modeling both material and geometric nonlinearity is proposed by Siyam et al. in “Large-Displacement Analysis of Planar RC Structures.” Employing a new definition of the local reference system and degrees of freedom, the approach results in a computationally efficient formulation. Cracking in concrete is accounted for, but reinforcing steel is smeared across the element, assuming perfect bond. Validation studies include comparing analytically simulated response with experimental data and the ability of the formulation to achieve quadratic convergence in the geometrically nonlinear range of response.

The December 2006 issue erroneously attributed the review of the paper “New Measure for Severity of Near-Source Seismic Ground Motion” by Sasani to Associate Editor Vinay Gupta. The final review and acceptance of this paper were handled by the Chief Editor, Sashi Kunnath.

Andreu, A., Gil, L., and Roca, P. (2007). “Computational analysis of masonry structures with a funicular model.” J. Eng. Mech., 133(4).

Anoop, M. B., and Rao, K. B. (2007). “Application of fuzzy sets for remaining life assessment of corrosion affected reinforced concrete bridge girders.” J. Perform. Constr. Facil., 21(2).

Ching, J., and Hsieh, Y.-H. (2007). “Approximate reliability-based optimization using a three-step approach based on subset simulation.” J. Eng. Mech., 133(4).

Feng, P., Ye, L., and Teng, J.-G. (2007). “Large-span woven web structure made of fiber reinforced polymer.” J. Compos. Constr., 11(2).

MacNamara, S. C., Garlock, M. M., and Billington, D. P. (2007). “Structural response of nuclear containment shield buildings with construction openings.” J. Perform. Constr. Facil., 21(2).

Main, J. A., and Jones, N. P. (2007). “Vibration of tensioned beams with intermediate damper. I: Formulation, influence of damper location.” J. Eng. Mech., 133(4).

Main, J. A., and Jones, N. P. (2007). “Vibration of tensioned beams with intermediate damper. II: Damper near a support.” J. Eng. Mech., 133(4).

Mosallam, A. (2007). “Structural evaluation and construction of FRP composites strengthening systems for the Sauvie Island Bridge.” J. Compos. Constr., 11(2).

Ni, Y. Q., Hua, X. G., Wong, K. Y., and Ko, J. M. (2007). “Assessment of bridge expansion joints using long-term displacement and temperature measurement.” J. Perform. Constr. Facil., 21(2).

Rutz, F. R., and Rens, K. L. (2007). “Wind loads for 19th century bridges: Design evolution, historic failures, and modern preservation.” J. Perform. Constr. Facil., 21(2).

Tabsh, S. W. (2007). “Stress-strain model for high strength concrete confined by welded wire fabric.” J. Mater. Civ. Eng., 19(4).

Takewaki, I. (2007). “Closed-form sensitivity of earthquake input energy to soil-structure interaction system.” J. Eng. Mech., 133(4).

Täljsten, B., Hejll, A., and James, G. (2007). “CFRP strengthening and monitoring of the Gröndals Bridge in Sweden.” J. Compos. Constr., 11(2).

Teng, J.-G., Huang, Y. L., Lam, L., and Ye, L. (2007). “Theoretical model for fiber-reinforced polymer-confined concrete.” J. Compos. Constr., 11(2).

Wang, Z., and Wong, K. K. F. (2007). “Stochastic dynamic analysis of inelastic structures using the force analogy method.” J. Eng. Mech., 133(4).

Yu, C., and Schafer, B. W. (2007). “Effect of longitudinal stress gradients on elastic buckling of thin plates.” J. Eng. Mech., 133(4).

Several names of reviewers did not appear on the Reviewer List that was published in the December 2006 issue of the Journal. Once again, the editors wish to acknowledge the efforts of reviewers and reiterate our appreciation for their contributions. The Technical Activities Division of SEI and the Associate Editors of the Journal of Structural Engineering wish to thank the following additional individuals who served as reviewers during the period August 2005–July 2006.