Editor's Note

The August 2005 issue of the Practice Periodical on Structural Design and Construction includes the Structural Design Forum, where the subject is “Certification? Inspection? What’s the Difference and Why Should You Care?” The author is Bobbi Marstellar, Vice President of Certification, American Institute of Steel Construction (AISC). This is followed by the Construction Forum, whose subjects are “Comments on Steel Construction…Our History…Conferences… The author is Cliff J. Schexnayder, Editor of the Construction Forum.

In addition to the above, this issue brings together a series of articles∕papers in the areas of structural engineering and construction practice. Also included is a Technical Note and Discussions on two papers published previously. All of these are briefly summarized in the following paragraphs.

Ryan Chancey, Thomas Sputo, Edward Minchin, and Jennifer Turner, all of the University of Florida, Gainesville, Fla., have prepared an interesting and timely paper entitled “Justifiable Precision and Accuracy in Structural Engineering Calculations: In Search of a Little Less Precision and Supposed Accuracy.” Our computational tools are capable of calculating to a high level of precision. One result is that engineers are currently producing calculations to unrealistically high levels of precision. Many practitioners advocate reporting structural calculations to four, five, and even six significant figures, disregarding the implicit precision on which modern design codes and specifications are based. In response to this practice and in order to remind the structural design engineers of the inherent limitations of the precision of structural engineering calculations, the authors have reviewed historical documents pertaining to structural design, taking into account methods of structural analysis and practical design situations. Conclusions were drawn from these considerations, and a recommendation as to an appropriate level of precision in structural design is presented.

The second paper in this issue deals with highway bridges and is entitled “Time-Dependent Behavior of Continuous Composite Integral Abutment Bridges.” The authors are M. Arockiasamy, of Florida Atlantic University, Boca Raton, Fla., and M. Sivakumar, of PTE Strand Co., Inc., Hialeah, Fla. The authors believe that integral abutment bridges provide bridge engineers a potentially economical design alternative to traditional bridges with thermal expansion joints. At the present time very limited design and construction guidelines are available, and no unified design procedures exist. The main parameters governing design include time-dependent effects of creep, shrinkage, and temperature on composite superstructure; soil pressure from abutment backfill; and soil-substructure-superstructure interaction. The authors developed analytical models and numerical procedures for predicting instantaneous linear and nonlinear time-dependent long-term behavior. The redistribution of moments due to temperature gradient, creep, shrinkage, and restraints produced by abutment foundation and backfill are also considered in the analysis. The readers are invited to comment on the models and procedures developed by these authors.

Continuing with the general topic of bridges, the next paper is entitled “Discussion on AASHTO LRFD Load Distribution Factors for Slab-on-Girder Bridges.” The author is C. S. Cai, of Louisiana State University, Baton Rouge, La. The author performed a study to develop a set of formulas for load distribution factors that are more rational than the current AASHTO LRFD formulas. A formula to quantify the intermediate diaphragm effect on live load distribution is also proposed. Practicing bridge engineers are asked to review this paper and comment on the efficacy of the proposed formulas.

The fourth paper is construction oriented and is titled “Decision Support System for Commencement Delay Claims.” The authors are Mohamed Hegab and Khaled Nassar, both of North Dakota State University. As all of us know, delay claims are common on construction projects. Commencement delay claims are different, as the owner of the project is responsible for the delay. This paper presents a methodology to solve the conflict of commencement delay in an efficient way through a well-described case study in which a decision tree was used to determine the minimum cost associated with the commencement delay claims. Our readers in construction are asked to comment to the editorial board on the efficacy and general application of the suggested procedure.

The next paper in this issue also deals with construction, and is entitled “The Challenges of Stadium Construction—A Case Study.” It is authored by Sarel Lavy and Aviad Shapira, both of Technion-Israel Institute of Technology, Haifa, Yuval Botansky, of Odar Engineering and Construction, Petah-Tikva, Israel, and Cliff J. Shexnayder of Arizona State University. The paper describes the distinctive design and construction requirements of an outdoor athletic stadium located in Haifa, Israel. This is an open-air stadium which accommodates about 2,400 seats in the upper deck. The lower deck contains office and visitor facilities. This stadium has a distinctive arrangement of 30-meter-high bowed reinforced concrete columns from which 24-meter-long curved reinforced concrete beams are cantilevered. Because of restricted access to the project site, it was necessary to cast both columns and beams at the site and to lift them into place.

The following paper deals with “Practices That Influence Safety Performance on Power Plant Outages.” The author is Jimmie Hinze, of University of Florida. The author states that power plants cannot function indefinitely without having to shut down one or more of its units to perform major maintenance or implement a necessary upgrade. Such power plant shutdowns are referred to as outages and are associated with serious safety concerns that stem primarily from the fact that the workforce buildup is very fast and work-schedule intense. The schedule intensity is mandated by utilities that want the power plant to be fully operational as soon as possible. It is common for outage work to be scheduled with a seven-day workweek, twelve-hour days, and two shifts per day to perform the work. A study was conducted to identify those practices employed on power plant outages that resulted in low injury rates. Results showed that safer performances were associated with cost-plus projects, projects where the utility financially supported safety promotion, projects where bonuses were linked with safety performance, projects that were shut down for shorter time periods, and projects where more innovative safety practices were implemented. Readers are asked to comment on similar experiences in their respective operations.

The next paper is a technical note entitled “Shear Lag in Rectangular HSS Members: A Comparison of Design Equations to Test Data.” The authors are Bo Dowswell and Stacey Barber, both of the firm Structural Design Solutions, Birmingham, Alabama. The AISC Load and Resistance Factor Design Specification for Steel Hollow Structural Sections includes equations to account for shear lag in slotted HSS connections. The equations are based on tests on open-section structural shapes. The authors performed a study that compares the AISC equations to available data from previous tests and finite-element models to determine whether the equations are valid for rectangular-section HSS members. Results from four research projects were compared with the AISC equations. In this the AISC equations were found to be reasonably accurate and generally conservative.

As mentioned, this issue of the journal also includes several discussions and closures. The first set of discussions is with respect to the paper titled “Rebuilding the World Trade Center,” by Robert F. Borg, John Gambatese, Kenneth Haines Jr., Chris Hendrickson, Jimmie Hinze, Arpad Horvath, Enno Koehn, Scott L. Moritz, Marvin Mass, and Robert A. Haughney (August 2003, Vol. 8, No. 3, pp. 137–145). The paper is discussed by K. Sivakumar, of the University of Dundee, U.K., and by Enno Koehn, of Lamar University, Beaumont, Tex. The closure for this paper is by Robert F. Borg.

The next discussion is about the paper “Minimizing Construction Vibration Effects,” by Mark R. Svinkin (May 2004, Vol. 9, No. 2, pp. 108–115). The discusser is Greg McLellan, of the Pepper Engineering Group, Inc., North Miami Beach, Fla. The closure is by Mark R. Svinkin.

The editorial board asks the readers to comment on the subject matter and quality of the papers presented in this issue.