Editor’s Note

This issue of the Journal consists of six technical papers on metal structures, two each on concrete and wood structures, three papers dealing with developments in analysis and computation, three papers on seismic effects, one paper on the topic of system identification, and a technical note examining a new approach to achieving ductility in RC beams.

The leadoff paper in this issue by Okazaki et al. investigates “Stability Requirements for Beams in Seismic Steel Moment Frames” through an analytical study in which lateral-torsional buckling and local buckling are explicitly modeled. Based on analyses, flange and web width-thickness limits are established to achieve various target rotation capacities. The results indicate strong flange-web interaction, which is contrary to current code provisions that treat flange and web local buckling as independent phenomena. Results from tests of six cantilever specimens are reported by Parra-Montesinos, Goel and Kim in “Behavior of Steel Double-Channel Built-Up Chords of Special Truss Moment Frames under Reversed Cyclic Bending.” The main parameters investigated were stitch spacing and internal bracing requirements, and the study finds that the current lateral bracing requirements specified in AISC-LRFD are inadequate to prevent lateral-torsional buckling of both individual elements and the built-up member.

Results from cyclic tests on six specimens with high strength bolts are described by Guo, Gu, and Liu in “Experimental Behavior of Stiffened and Unstiffened End-Plate Connections under Cyclic Loading.” Although the plastic rotation of all connections exceeded 0.03 radians, stiffened specimens exhibited higher load carrying and energy dissipation capacities. For thinner end plates, the stiffeners delayed the premature fracture of welds. Column web stiffeners were shown to reduce the possibility of strength failure of the column flange. Dezi, Gara, and Leoni investigate shear lag effects in slabs resulting from different prestressing techniques in their paper “Effective Slab Width in Prestressed Twin-Girder Composite Decks.” The analysis accounts for loss of planarity in the slab cross section, the flexibility of the shear connection, and the time-dependent behavior of concrete. The authors conclude that the effective width suggested by the code overestimates the stress level induced by prestressing and leads to nonconservative solutions.

A two-part paper summarizing an experimental and analytical study on Fatigue of Corrugated-Web Plate Girders is presented by Ibrahim, El-Dakhakhni, and Elgaaly. The first paper describes findings from the testing of trapezoidally corrugated-web plate girders subjected to fatigue loading under different stress ranges. A relationship between the stress range and number of cycles to failure is developed. The second paper presents finite-element and fracture-mechanics studies to investigate the effects of different geometrical parameters on the induced stress concentration at different locations and explains the findings of the experimental study described in the earlier paper. An analytical procedure to estimate the fatigue life of the girders is developed.

A “Strain Rate Model for Dynamic Analysis of Reinforced Concrete Structures” is proposed by Pandey et al. The model accounts for pressure sensitivity in 3D loading and strain rate sensitivity in dynamic loading. A smeared crack approach is used to model tension cracking, and tension stiffening is considered by defining the tensile stress-strain curve in nondimensional form. The proposed formulation is shown to simulate effects such as tensioning stiffening and aggregate interlock and also to predict postcracking stresses in concrete and postyield stresses in steel with a fair degree of accuracy. A plain strain analytical model to determine the confining pressure of transverse reinforcement is developed by Braga, Gigliotti, and Laterza in “Analytical Stress–Strain Relationship for Concrete Confined by Steel Stirrups and/or FRP Jackets.” The model considers the effect of cross-sectional tangential stresses, and the complete confining stress state is described by a single parameter as a function of the axial strain level. The model is validated with available experimental data.

A new concept in shear wall design is introduced by Varoglu et al. in “Midply Wood Shear Wall System: Concept and Performance in Static and Cyclic Testing.” One ply of sheathing material is placed at the center of the wall between a series of stud pairs and plates oriented in a $90°$ rotated position relative to those used in standard wood walls. Results of experimental testing indicate that the load carrying and energy dissipation capacity of midply walls is over three times that of comparable standard wood shear walls. Twenty-one 2.4 by $2.4\mathrm{m}$ specimens were tested by Johnston, Dean, and Shenton to study the “Effects of Vertical Load and Hold-Down Anchors on the Cyclic Response of Wood Framed Shear Walls.” Seven different configurations of walls with and without hold down anchors and varying uniform vertical loads were tested using the CUREE test protocol. Results indicate that the vertical loads increase both the lateral stiffness and energy dissipation capacity of the walls.

A numerical approach for “Form-Finding of Nonregular Tensegrity Systems” is proposed by Zhang, Maurin and Motro. Based on the dynamic relaxation method with kinetic damping, the proposed method leads to more intricate and creative forms. Either the force or length of selected elements can be fixed by an appropriate choice of related stiffness during the form-finding process. Several numerical examples are presented to illustrate the application of the process. “Sequential Hybrid Inverse Mapping for State-Specified Design of Frames” by Ito and Nakamura presents a generalized method wherein a combined set of unknown member stiffnesses and member end-displacements can be determined for a set of prescribed member end-displacements and stiffnesses. The method enables a designer to find solution sets of member stiffnesses and member end-displacements (or strains) for a variety of design problems for which overall $P\text{-}\delta$ and $P\text{-}\Delta$ must be taken into account. A procedure that combines the benefits of the pattern identification ability of the Apriori DM algorithm with the capabilities of GA operators is proposed by Wang and Ghosn in “Hybrid Data Mining/Genetic Shredding Algorithm for Reliability Assessment of Structural Systems.” It is shown that the proposed algorithm significantly reduces the computational effort associated with determining the probabilistically dominant failure modes of structures.

Lee and Foutch utilize a reliability-based procedure in the “Seismic Evaluation of Steel Moment Frame Buildings Designed Using Different R-Values.” The evaluation comprises 3-, 9-, and 20-story steel moment frames designed with R-factors ranging from 8 to 12 and subjected to a suite of ground motions representing a hazard level corresponding to a 2% probability of being exceeded in 50 years. The study concludes that current R-factors result in conservative designs for the 3-and 9-story buildings, while the 20-story buildings show a low level of confidence for achieving a collapse prevention performance objective. The viability of a real-time dynamic testing procedure called Effective Force Testing (EFT) is the subject of the paper “Comparison of Tests of a Nonlinear Structure Using a Shake Table and the EFT Method” by Zhao et al. Critical issues to be addressed in conducting an EFT test are discussed. Test results indicate that the EFT method can be used to apply real-time seismic simulation to structures undergoing nonlinear deformation if proper velocity feedback compensation is provided. “New Three-Dimensional Damage Index for RC Buildings with Planar Irregularities” is proposed by Jeong and Elnashai. The procedure accounts for bidirectional and torsional response effects and is based on decomposing a 3D structure into planar frames. The local damage index is sensitive to out-of-plane response, and a method to combine local damage indices is also proposed.

“Structural Damage Detection via Modal Data with Genetic Algorithms” by Perera and Torres describes a nondestructive global damage detection and assessment methodology based on changes in frequencies and mode shapes of vibration. A nonclassical optimization approach involving the use of genetic algorithms is used to localize damaged areas of the structure. The method is verified for numerous damage scenarios utilizing both simulated beams and experimental data.

A “New Avenue of Achieving Ductility for Reinforced Concrete Members” is proposed by Wu, where compressive yielding instead of tensile yielding is developed in the member. The author contends that there is no limit on the achievable ductility of a flexural member as long as the ductile compression zone can sustain the yielding. Additionally, the proposed approach can avoid rupture of nonductile reinforcement or the crushing of concrete regardless of whether the beam is under or over reinforced. The effectiveness of the idea is demonstrated through experimental testing of reinforced concrete beams.

Behr, R. A. (2006). “Design of architectural glazing to resist earthquakes.” J. Archit. Eng., 12(3).

Bozorgzadeh, A., Megally, S., Restrepo, J. I., and Ashford, S. A. (2006). “Capacity evaluation of exterior sacrificial shear keys of bridge abutments.” J. Bridge Eng., 11(5).

Clift, C. D. (2006). “Curtain wall designs for wind and blast: Three case studies.” J. Archit. Eng., 12(3).

Connor, R. J., and Fisher, J. W. (2006). “Consistent approach to calculating stresses for fatigue design of welded rib-to-web connections in steel orthotropic bridge decks.” J. Bridge Eng., 11(5).

Lauzon, R. G., and DeWolf, J. T. (2006). “Ambient vibration monitoring of highway bridge undergoing a destructive test.” J. Bridge Eng., 11(5).

Li, H., Yang, H., and Hu, S. L. J. (2006). “Modal strain energy decomposition method for damage localization in 3D frame structures.” J. Eng. Mech., 132(9).

Minor, J. E., and Norville, H. S. (2006). “Design of window glass for lateral pressures.” J. Archit. Eng., 12(3).

Norville, H. S., and Conrath, E. J. (2006). “Blast-resistant glazing design.” J. Archit. Eng., 12(3).

Scruggs, J. T., and Iwan, W. D. (2006). “Optimal nonlocal and asymmetric structural damping using regenerative force actuation networks.” J. Eng. Mech., 132(9).

Segal, F., and Val, D. V. (2006). “Energy evaluation for Ramberg-Osgood hysteretic model.” J. Eng. Mech., 132(9).

Takewaki, I. (2006). “Probabilistic critical excitation method for earthquake energy input rate.” J. Eng. Mech., 132(9).