Editor’s Note

The section begins with the very important topic of whether seismic design provisions can improve the resistance of buildings to blast loads and progressive collapse. Hayes et al. quantifies the relationship between seismic detailing and blast and progressive collapse resistance using the Alfred P. Murrah Federal Building as a test-case, using three different strengthening schemes, in the paper “Can Strengthening for Earthquake Improve Blast and Progressive Collapse Resistance?” The study concludes that strengthening the perimeter elements using current seismic detailing can improve the survivability of the building, but internal seismic strengthening is not as effective.

Starr and Krauthammer investigate the characteristics of force transfer through cladding panels to the structural support frame using precision impact testing in “Cladding-Structure Interaction Under Impact Loads.” Based on observed impact force dissipation results, the role of cladding systems in reducing short-duration load effects is better understood. In “Blast Response of Lightly Attached CMU Walls,” Baylot et al. present a series of physical experiments to develop methods for predicting the hazard levels associated with CMU walls subjected to blast loads. Test results are given for several retrofitting techniques that have been developed to mitigate blast load debris hazards. In a similar paper, entitled “Failure Mechanisms of Polymer-Reinforced Concrete Masonry Walls Subjected to Blast,” by Davidson et al., thin-membrane elastomeric polymers are applied to the CMU wall interior to prevent breaching and collapse from blast loads. The failure mechanisms found from the explosive tests are presented along with finite-element simulations to study the parameters that affect the blast response of polymer-reinforced CMU walls. Blast retrofit wall technologies and dynamic modeling techniques are further studied and developed in “Analysis and Experimental Evaluation of In-Fill Steel-Stud Wall Systems under Blast Loading,” by Salim et al. Based on full-scale wall and component testing, a dynamic model is developed that will enable designers to predict the level of performance of a wall system for a given explosion threat level.

In the paper “Experimental Investigation of the Dynamic Properties of Aluminum Foams,” by Sadot et al., the mechanical properties of aluminum foams under static and impact load conditions are experimentally investigated to develop reliable analytical models for predicting the behavior of the foam-protected structures to blast loads. In their follow-up paper, “Foam Protected RC Structures under Impact: Experimental and Numerical Studies,” Schenker et al. present results of experimental and numerical blast load investigations of reinforced concrete beams and plates that are protected with aluminum foams. In yet another paper involving concrete, Salim et al. experimentally investigate the “Shock Load Capacity of Concrete Expansion Anchoring Systems in Uncracked Concrete.” Their findings reveal for the first time the ultimate capacity of various concrete expansion anchors under blast-event-type loading conditions. Important conclusions and recommendations are given for several commonly used concrete expansion anchors.

Two papers are presented in this section that incorporate blast and impact loads in bridge analysis and design. Winget et al. consider blast loading in their paper titled “Analysis and Design of Critical Bridges Subjected to Blast.” A summary is given of the results of ongoing research to develop performance-based blast design standards for bridges. Discussion is also presented on the inclusion of physical security and site layout principles in the design, and on the design and retrofit options available to mitigate blast effects. The bridge response and vulnerability of piers to impact loads are studied in the paper “Numerically Efficient Dynamic Analysis of Barge Collisions with Bridge Piers,” by Consolazio and Cowan. The authors present a new approach which couples the nonlinear dynamic barge and pier responses into a shared collision impact force. Numerical procedures are employed for accelerating the convergence of the coupled system to allow for more efficient and rapid analyses.

In the paper by Keierleber and Rosson, entitled “Higher-Order Implicit Dynamic Time Integration Method,” a new time integration scheme is developed and presented that makes use of higher-order polynomial approximations to more accurately model a system’s dynamic response. The relative merits and stability aspects are presented along with accuracy comparisons of the new higher-order method and several traditional implicit methods.

This issue includes three additional technical papers, two technical notes, and a discussion. The first paper deals with “Nonlinear Characteristics of Damaged Concrete Structures under Vehicular Load.” Law and Zhu propose a damage index based on the flexural rigidity of the beam to assess the damage resulting from vehicular loads. Next, Attard and Fafitis define a nonlinear constitutive relationship in the postelastic range in their paper “On the Plastic Hinge Development of Frame Members Using a Nonlinear Hardening Rule.” Plastic hinge lengths and element displacements are derived, and the formulation is validated through comparison with experimental results from published literature. The final technical paper, “Experimental Study on Embedded Steel Plate Composite Coupling Beams,” by Lam et al., investigates a new system to improve the performance of coupling beams under earthquake and severe wind loading. Experimental evidence is presented to demonstrate the enhanced performance of the proposed embedded plate. Procedures to assist in the design of the plate are also provided.

The first technical note, “Performance Tests and Hysteresis Model of MRF-04K Damper,” by Li and Xu, present a double-ended shear mode combined with valve mode MRF damper. The writers show that a modified version of the Bouc-Wen model is able to reproduce observed experimental response and that the damper is effective for structural control applications. The final paper in this issue, by van de Lindt et al., examines “Strength-based seismic reliability of wood shear walls designed according to AF&PA/ASCE 16.” Reliability indices were calculated by evaluating the seismic performance of 12 different wood shear walls. The findings are expected to provide guidance in updating codes and standards. The issue concludes with a discussion by Cho on a paper by Park et al. that appeared in June 2003. The discussers offer clarification on their original truss analogy and its application in composite beams with web openings. Park et al. point out the necessity of distinguishing diagonal tension strength from pull-out strength, whereas the model by the discussers incorporates diagonal tension failure indirectly in the development of the pull-out capacity of the studs.

The current issue of The Journal of Performance of Constructed Facilities (Vol. 19, No. 3) contains several papers examining the damage, performance, and inherent integrity of the Pentagon structure to the airliner crash of September 11, 2001.

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Dowswell, B., and Barber, S. (2005). “Shear lag in rectangular HSS tension members: Comparison of design equations to test data.” Pract. Period. Struct. Des. Constr., Vol. 10(3).

Gavin, H. and Aldemir, U. (2005). “Optimal control of earthquake response using semiactive isolation.” J. Eng. Mech., Vol. 131(8).

Lee, K. H., and Rosowsky, D. V. (2005). “Site-specific snow load models and hazard curves for probabilistic design.” Nat. Hazards Rev., Vol. 6(3).

Prasad, B. K. R. et al. (2005). “Fracture mechanics model for analysis of plain and reinforced high-performance concrete beams.” J. Eng. Mech., Vol. 131(8).

Surry, D., Kopp, G. A., and Bartlett, F. M. (2005). “Wind load testing of low buildings to failure at model and full scale.” Nat. Hazards Rev.,Vol. 6(3).

Uddin, N., and Vaidya, U. (2005). “Ballistic testing of polymer composites to manufacture emergency safe house shelters.” J. Compos. Constr., Vol. 9(3).

Wang, D., and El-Sheikh, A. I. (2005). “Large-deflection mathematical analysis of rectangular plates.” J. Eng. Mech., Vol. 131(8).

Yu, H.-W., and Hwang, S.-J. (2005). “Evaluation of softened truss model for strength prediction of RC squat walls.” J. Eng. Mech., Vol. 131(8).