Editor’s Note

The November 2006 issue of the Practice Periodical on Structural Design and Construction contains five relevant and practical papers in addition to the Construction forum plus discussions and closures of previously published papers.

The first paper in this issue is titled “Fundamental Principles for Avoiding Congested Work Areas—A Case Study,” and was prepared by H. Randolph Thomas, David R. Riley, and Sunil K. Sinha. The authors hail from Pennsylvania State University where Dr. Thomas serves as Professor of Civil Engineering, Dr. Riley as Associate Professor of Architectural Engineering, and Dr. Sinha as Assistant Professor of Civil Engineering. The paper presents results of a case study that documents, both qualitatively and quantitatively, the impact of congested work areas on labor productivity. Field observations are compared to historical baseline productivity rates and findings of lower productivity are reported. For construction-minded professionals, this paper presents a useful review of site management techniques which can be beneficial to improving profitability and client satisfaction.

The 2005 hurricane season was one of the worst on record with respect to both devastation and the number of named storms that impacted the continental United States. The second paper in this month’s Practice Periodical highlights the significant damage that occurs from windborne debris during hurricanes. The paper titled, “Large Wind Missile Impact Capacity of Residential and Light Commercial Buildings,” was authored by Nur Yazdani, Professor and Chairman, Department of Civil Engineering, University of Texas at Arlington; Perry S. Green, Technical Director, Steel Joist Institute; and Saif A. Haroon, Saiful Bouquet Inc. The paper presents a useful summary of residential and light commercial roof and wall assemblies that meet the missile impact provisions of the 2001 Florida Building Code. Assembly systems to be avoided are also reviewed. The summaries provided in this paper will be useful to engineers and contractors who design and build structures in hurricane&-prone areas.

The third paper, “Strengthening of Reinforced Concrete Bridge Columns with FRP Wrap,” was contributed by our colleagues at the Illinois Institute of Technology. Sidney A. Guralnick, Perlstein Distinquished Professor of Engineering–Emeritus and Lukito Gunawan, Adjunct Assistant Professor present a compressive strength model for confined concrete wrapped with fiber-reinforced polymer (FRP). The model, which is based on an extension of Mohr’s strength theory, was verified using existing test data on reinforced concrete bridge columns. Bridge strengthening using FRP wraps are becoming more mainstream, and models such as the one presented here will be useful to bridge engineers.

Advances in concrete technology have yielded significant advances in concrete strength, which have been accompanied by beneficial gains in durability and economics. The fourth paper in this issue should be useful to bridge designers as these high-performance materials become more widely used. Following the bridge theme, this paper presents a case study for the use of high-performance concrete (HPC). The paper entitled “Case Study of a High-Performance Concrete Bridge in Tennessee” studies a bridge constructed partially with normal strength concrete and partially with HPC. The precast beams and cast-in-place deck and diaphragms were instrumented during construction and monitored through service. Comparisons of time-dependent performance characteristics for strength, creep, shrinkage, and camber are made. The case study was carried out by X. Sharon Huo, Pingsheng Zhu, Francis Ung of the Tennessee Technology University, and Edward P. Wasserman of the Tennessee Department of Transportation.

The fifth and last paper in the Practice Periodical discusses the results of a postconstruction environmental monitoring study of a fly ash-based road bed. The paper entitled “Postconstruction Environmental Monitoring of a Fly Ash-Based Road Subbase” was prepared by Samrat Mohanty, Research Assistant, and Yoginder Chugh, Professor, both with the Mining and Mineral Resources Engineering School at Southern Illinois University, Carbondale. Pre- and postconstruction water quality tests were compared and found to comply with Illinois standards. The resulting conclusion is that fly ash subbase materials can be used without adverse environmental effects. Sustainability is the future, and this paper presents a unique opportunity to use power plant waste products in a safe and beneficial way.

The Discussion and Closures section of the Periodical includes a discussion prepared by Peter Kocsis with author closure is presented for a paper published in August 2005 and entitled “Discussion on AASHTO LRFD Load Distribution Factors for Slab-on-Girder Bridges.” The author of this paper was C. S. Cai. A second discussion includes a Discussion of an earlier (May 2005) paper entitled “Effect of Spread Footing Flexibility on Structural Response” by Sami W. Tabsh and Abdul Raouf Al-Shawa. The discussion was prepared by John Springfield, the Structural Design Forum Editor.

The editorial board thanks the authors of this issue’s papers, and encourages readers to submit discussions- and comments- on the subject matter presented. Discussions and comments should be submitted as stipulated in the General Information section, which can be found at the front of this Periodical.