Editor’s Note

A two-part paper by Kurama et al. investigates the behavior of a special type of hybrid steel-concrete system consisting of concrete shear walls and steel coupling beams. The first paper focuses on “Experimental Evaluation of Posttensioned Hybrid Coupled Wall Subassemblages.” The paper discusses results from tests on 11 subassemblies in which coupling is achieved by posttensioning the steel beams to the walls by using unbonded tendons. Top and seat angles are used at the beam-to-wall connections to yield and provide energy dissipation. The system performs well under cyclic loading with negligible residual deformations. In the second paper, the writers describe “Seismic Design and Analytical Modeling of Posttensioned Hybrid Coupled Wall Subassemblages.” Experimental data presented in the companion paper are used to validate and refine analytical models for the subassemblages. Guidelines for selecting the coupling beam and the posttensioning steel area, as well as the design of the top and seat angles and their connections, are proposed. Results from an experimental study on the seismic response of two steel-concrete hybrid subassemblies are presented by Fargier-Gabaldón and Parra-Montesinos in “Behavior of Reinforced Concrete Column—Steel Beam Roof Level T-Connections under Displacement Reversals.” The primary variables investigated include anchorage requirements for the column longitudinal bars and confinement requirements in the T-connection. It is concluded that properly designed hybrid connections have potential for use in seismic applications.

Canbay et al. investigate the monotonic behavior of “High-Strength Concrete Columns under Eccentric Load.” On the basis of the observed response of 11 tested specimens, the authors found that the response of columns with cross ties consisting of a $135\text{-}\text{degree}$ hook at one end and $90\text{-}\text{degree}$ bend at the other end is comparable with that of columns with ties supporting intermediate longitudinal bars. Also, current ACI 318-02 specifications provide an upper bound estimate of the ultimate strength of the sections. Hoehler and Stanton propose a “Simple Phenomenological Model for Reinforcing Steel under Arbitrary Load.” The model provides steel stress as an explicit function of the total steel strain and accounts for monotonic envelope curves with a yield plateau and nonlinear strain hardening. Model para-meters for typical reinforcing steel used in the United States are recommended.

The “Fatigue Life of Girders with Trapezoidal Corrugated Webs,” based on 4-point bending tests of eight large-scale girders fabricated from HPS 485W steel, is evaluated by Sause et al. Test results demonstrate that corrugated web I-girders exhibit a longer fatigue life than conventional steel I-girders with transverse stiffeners. I-shaped members loaded in compression and bending about the minor principal centroidal axis are the focus of the paper, “Minor Axis Moment-Thrust Response Behavior in Steel I-Shaped Members,” by Aktas and Earls. Modifications to the current AISC interaction equations are proposed to predict the strength of these types of members. Lee and Gazzola propose “Design Equation for Offshore Overlap Tubular K-Joints under In-Plane Bending,” which is based on a numerical parametric study. A capacity equation is derived from nonlinear regression of the database of finite element results. “Test and Design of Aluminum Alloy Compression Members” by Zhu and Young reports the results from a test program that included columns with and without transverse welding of the end plates. Comparisons of the test strengths and design strengths obtained by using the American, Australian/New Zealand, and European specifications are presented.

“Response of Nonstructural Components in Structures with Damping Systems” is investigated by Pavlou and Constantinou. The buildings were represented by steel frames designed by the procedures described in the NEHRP 2000 recommended provisions. The study concludes that significant benefits may be achieved with viscous damping systems in reduced floor spectral accelerations and absolute velocities. An earlier procedure by the writers that estimates peak deformation in base-isolated buildings is extended by Ryan and Chopra for “Estimating Seismic Demands for Isolation Bearings with Building Overturning Effects.” Rocking and bearing axial-load effects are found to have minimal influence on peak lateral bearing deformation. A control algorithm taking into account external excitations is developed by Ma and Yang in “Sampled Data Feedback-Feedforward Control of Structures with Time Delays.” A linear feedforward gain is proposed in combination with an adaptive scheme to adjust this gain in real time depending on the measurement history. The method is validated with examples that use multistory shear beam lumped mass models.

A step-by-step procedure is developed by Kim et al. in “Application of Internally Damped Shearbeam Model to Analysis of Buildings under Earthquakes: Robust Procedure for Quick Evaluation of Seismic Performance.” The method consists of a series of explicit formulas that do not require iteration and provides envelopes of maximum story drifts. The procedure is validated by comparing the predictions with time-history estimates of three sample building structures.

A new procedure to derive the distribution of peak pressure and load coefficients is proposed by Tieleman et al. in “Peak Wind Load Comparison: Theoretical Estimates and ASCE 7.” For all cases investigated, the suburban peak and load coefficients were found to exceed those obtained from open-terrain exposure experiments. Based on analysis of data from testing at the University of Western Ontorio and Clemson, it is concluded that using dynamic pressures to convert wind load data from one exposure to another may be unreliable.

Balling et al. develop a unique algorithm to determine multiple optimum and near-optimum topologies in a single run in their paper, “Multiple Optimum Size/Shape/Topology Designs for Skeletal Structures Using a Genetic Algorithm.” The proposed procedure is validated by using several standard test problems as well as a bridge and a plane frame example.

“Frequency Analysis of Ground Snow Data and Production of Snow Load Map Using Geographic Information System for the Eastern Black Sea Region of Turkey” is presented by Durmaz and Daloğlu. This is accomplished by examining the probability plot correlation coefficients with three different cumulative distribution functions and determining the best fit of the theoretical probability distribution by using snow data from 32 Turkish weather stations located in the eastern Black Sea region and adjacent cities.

Ian Feltham seeks clarification on the applicability of the expressions proposed by Kim and Mander in their paper “Theoretical Shear Strength of Concrete Columns due to Transverse Steel,” which appeared in the January 2005 issue of the Journal. The writers provide closure to the topic by clarifying the issues raised in the discussion and indicating that the proposed model is applicable to both beams and to columns. In the second discussion, M. P. Saka questions the validity of the comparison presented by Camp et al. in one of the design examples in the paper “Design of Steel Frames using Ant Colony Optimization” (Vol. 131, No. 3). The original writers provide further explanation to justify the validity of the comparisons.

Alhan, C., Gavin, H. P., and Aldemir, U. (2006). “Optimal control: A basis for performance comparison of passive and semiactive isolation systems.” J. Eng. Mech., 132(7).

Cheng, L., and Karbhari, V. M. (2006). “Fatigue behavior of a steel-free FRP-concrete modular bridge deck system.” J. Bridge Eng., 11(4).

Cole, T. A., Lopez, M., and Ziehl, P. H. (2006). “Fatigue behavior and nondestructive evaluation of full-scale FRP honeycomb bridge specimen.” J. Bridge Eng., 11(4).

Davister, M. D. (2006). “The most degrading postbuckling mode of pin-jointed structures.” J. Eng. Mech., 132(7).

Landis, E. N. (2006). “Towards a physical damage variable for concrete.” J. Eng. Mech., 132(7).

Saiidi, M. S., Johnson, R., and Maragakis, E. M. (2006). “Development, shake-table testing, and design of FRP seismic restrainers.” J. Bridge Eng., 11(4).

Stiller, W. B., Gergely, J., and Rochelle, R. (2006). “Testing, analysis, and evaluation of a GRFP deck on steel girders.” J. Bridge Eng., 11(4).

Yao, W., and Ye, Z. (2006). “Internal forces for statically indeterminate structures having different moduli in tension and compression.” J. Eng. Mech., 132(7).