Editor’s Note

Fifteen technical papers make up this issue of the Journal. The theme of the first group of seven papers is metal and composite structures. This is followed by two papers on Concrete Structures, one paper examining the behavior of fiber reinforced cement composite members, one dealing with nonstructural elements in wood frame structures, one on dynamic computational methods, and one on structural damage detection. The issue concludes with a two-part paper investigating the seismic response of steel frame structures.

“Finite-Element Modeling of Partially Encased Composite Columns Using the Dynamic Explicit Method” by Begum, Driver and Elwi leads off this issue of the Journal. The explicit formulation, in conjunction with a concrete damage plasticity model, is shown to provide good predictions of the capacity of both uniaxially and eccentrically loaded PEC column tests reported in the literature. The study suggests that the ultimate capacity of the column is not significantly affected by the presence of local imperfections. An analytical procedure for the “Design of Wide-Flange Section Column-to-Split-Tee Tensile Connection with High-Strength Bolts” is derived by Harada and Morita. The yield line analysis method considers the case of both punching shear deformation of plate elements and tensile deformation of connection bolts. The validity of the equations to predict yield and maximum strengths of the connection is demonstrated by comparison with available experimental results. Theoretical, experimental and finite element simulations are presented by Abbas, Sause, and Driver in “Analysis of Flange Transverse Bending of Corrugated Web I-Girders under In-Plane Loads.” The proposed analytical method for quantifying flange transverse bending is validated through comparison with four-point bending experiments of large-scale corrugated web girders. Based on results of finite element analyses, the writers conclude that the differences between experimental and theoretical flange stresses can be attributed to the contribution of the web to flexural resistance.

Kozy and Earls report on a combined experimental-analytical study in their paper “Bearing Capacity in Long-Span Tubular Truss Chords.” The study indicates that the limit state of bearing failure is influenced by the geometry of the connection, the nature of loading and material properties. A finite element parametric study is then carried out along with yield line analyses to develop capacity equations for bearing capacity. “Cold-Formed High-Strength Stainless Steel Tubular Sections Subjected to Web Crippling” is presented by Zhou and Young. Tests were carried out on specimens under four loading conditions: end-one-flange, interior-one-flange, end-two-flange, and interior-two-flange. Test results were compared to design strengths obtained using the American, Australian/New Zealand and European specifications. Existing specifications are shown to be unconservative or overly conservative and consequently, a new unified web crippling equation is proposed for cold-formed high-strength stainless steel square and rectangular hollow sections.

Park et al. present results from an experimental program in their paper “Framed Steel Plate Wall Behavior under Cyclic Lateral Loading.” Five single-bay three-story specimens were tested with varying plate thickness and strength and compactness of the column. It is shown that well-designed steel plate walls can sustain large ductility and possess adequate energy dissipation capacity. Walls with relatively thin plates exhibit shear-dominated response while walls with thicker plates exhibit a predominantly flexural response. Walls with thinner plates achieved better ductility, though adequately designed boundary columns are essential for overall satisfactory performance of the system. A performance-based approach is outlined by Garlock, Sause and Ricles in “Behavior and Design of Posttensioned Steel Frame Systems.” Seismic performance levels, seismic input levels, structural limit states and capacities, and structural demands for post-tensioned frame systems are defined. A step-by-step procedure is proposed and the methodology is evaluated by comparing the demands obtained through time-history analyses. While design criteria for the limit states of connection strength, angle fracture and strand yield were generally satisfied, other design criteria were not always satisfied in some elements in the frame indicating the need for additional research.

A smeared cracking approach is developed by Chen and Mahadevan to carry out “Cracking Analysis of Plain Concrete under Coupled Heat Transfer and Moisture Transport Processes.” An integrated finite-element based framework is used to simulate crack propagation in concrete exposed to coupled heat transfer and moisture transport. The cracking state in each element is characterized using a local relative crack density (LRCD) concept and a numerical relationship between LRCD and the moisture transport property is developed. A measure of overall deterioration at the structural level is then estimated using the concept of global relative crack density. A method for “Advanced Crack Width Analysis of Reinforced Concrete Beams under Repeated Loads” is presented by Oh and Kim. Bond stress-slip relations and the variation of transfer length under repeated loading are incorporated in the model. The model is validated with previously published experimental data. Findings from the analytical study indicate that the transfer length decreases as a function of load cycles due to increase in residual slip.

Parra-Montesinos and Chompreda report on findings from an experimental study investigating “Deformation Capacity and Shear Strength of Fiber-Reinforced Cement Composite Flexural Members Subjected to Displacement Reversals.” It is found that all specimens constructed with strain-hardening FRCC exhibited drift capacities in excess of 4% and buckling of longitudinal reinforcement in members without web reinforcement did not occur at plastic hinge rotations of 4%.

The effect of finishes and partitions are numerically examined by van de Lindt and Liu in “Nonstructural Elements in Performance-Based Seismic Design of Wood Frame Structures.” An incremental mass analysis (IMA) approach, derived from the concept of an incremental dynamic analysis was utilized to determine what seismic mass numerically produces a prescribed performance level for a wood frame structure or sub-assembly. Findings from the analytical study indicate that the allowable seismic mass can be significantly increased when nonstructural elements are included in the design.

Efficient local approximations and accurate global approximations are combined to achieve “Efficient Dynamic Reanalysis of Structures” by Kirsch, Bogomolni and Sheinman. A combined approximations approach, developed originally for static analysis, is developed using concepts contained in methods such as series expansion, reduced basis, matrix factorization and Gram-Schmidt orthogonalizations. A reduced eigenproblem is introduced and numerical examples to demonstrate the value of the approach are presented.

A methodology for “Improving the Performance of Structural Damage Detection Methods Using Advanced Genetic Algorithms” is proposed by Raich and Liszkai. The method identifies both the location and severity of the damage in structural systems using a limited amount of measured data. Damage is identified by minimizing the error between measured and analytically computed frequency response functions obtained through finite element updating. Two genetic algorithm representations were evaluated on simulated damage case studies. The writers conclude that the proposed methodology in conjunction with near-optimal sensor layouts provides reduced sensitivity to noise thereby enabling the prediction of damage in relatively large structures with greater accuracy.

The seismic response of steel moment frames is investigated in a two-part paper by Liao, Wen and Foutch. Modeling considerations for the “Evaluation of 3D Steel Moment Frames under Earthquake Excitations” are examined in the first part. The 3D finite element model employed in the study considers the effect of gravity frames, panel zones and inelastic column deformation. Results indicate that torsional effects due to non-symmetric member failure are important and that conventional lumped-plasticity models are inappropriate for use in Incremental Dynamic Analysis because it limits the development of plasticity in the columns. Reliability and redundancy factors proposed in the new NEHRP provisions are investigated in the second paper. Results of the fragility and limit state probability analyses indicate that buildings with fewer moment frames are more vulnerable and may not meet FEMA/SAC target performance criteria. Further, it is found that the new NEHRP 2003 provisions are a significant improvement over the 1997 recommendations; however, it is suggested that the proposed uniform $\rho$ factor of 1.3 could be further improved to account for the effect of different number and layout of moment frames and the interaction between motions in the principal direction and torsional motions.

Bazant, Z. P., and Verdure, M. (2007). “Mechanics of progressive collapse: Learning from World Trade Center and building demolitions.” J. Eng. Mech., 133(3).

Christenson, R. E., Spencer, B. F., and Johnson, E. A. (2007). “Semiactive connected control method for adjacent multidegree-of-freedom buildings.” J. Eng. Mech., 133(3).

Connor, R. J., Kaufmann, E. J., Fisher, J. W., and Wright, W. J. (2007). “Prevention and mitigation strategies to address recent brittle fractures in steel bridges.” J. Bridge Eng., 12(2).

Koechlin, P., and Potapov, S. (2007). “A global constitutive model for reinforced concrete plates.” J. Eng. Mech., 133(3).

Lu, X., and Hsu, C.-T. T. (2007). “Stress-strain relations of high-strength concrete under triaxial compression.” J. Mater. Civ. Eng., 19(3).

McMullin, K. M., and Merrick, D. S. (2007). “Seismic damage thresholds for gypsum wallboard partition walls.” J. Archit. Eng., 13(1).

Melchor-Lucero, O., Carrasco, C. J., Espino, L., Fernandez, A., and Oseguedo, R. A. (2007). “Computer modeling for a generalized approach to measure impact damage.” J. Eng. Mech., 133(3).

Samaan, M., Kennedy, J. B., and Sennah, K. M. (2007). “Dynamic analysis of curved continuous multiple-box girder bridges.” J. Bridge Eng., 12(2).

Szuladzinski, G. (2007). “Response of beams to shock loading: Inelastic range.” J. Eng. Mech., 133(3).

Taher, R. (2007). “Design of low-rise buildings for extreme wind events.” J. Archit. Eng., 13(1).

Wallner, M., and Pircher, M. (2007). “Kinematics of movable bridges.” J. Bridge Eng., 12(2).

Yehia, S., Abudayyeh, O., Nabulsi, S., and Abdelqader, I. (2007). “Detection of common defects in concrete bridge decks using nondestructive evaluation techniques.” J. Bridge Eng., 12(2).