Editor’s Note

The February 2009 issue of the Practice Periodical on Structural Design and Construction contains five relevant and practical papers in addition to the structural design and construction forums.

The first paper in this issue is entitled “Construction Learning Curves,” and was prepared by H. Randolph Thomas, M.ASCE. The author hails from the Pennsylvania State University, where he serves as professor of civil engineering. The paper presents foundational information about construction learning curves to better explain their use in defending contractor claims for monetary damages. Learning curves originated in the aircraft manufacturing industry and have been applied to the construction industry without understanding of their proper application. Unfortunately, the concept and data inputs are often used to mask poor project management in attempts to mitigate financial loss. This paper will be useful for individuals assisting contractors in support of justifiable construction claims or owners reviewing unsubstantiated claims.

An interesting community improvement project consisting of a pedestrian footbridge for the City of Pamplona is described in the second paper. Francisco Ramírez Chasco, Andrés Seco Meneses, and Eduardo Prieto Cobo present “Alemanes Footbridge.” The project design seeks to minimize its effect on the river landscape and ecology while constituting a reference point in the newly developed area, which lacks a central community landmark.

Construction industry profitability is often subject to the influences of Mother Nature. When unfavorable weather is expected, labor inefficiencies, which increase cost and schedule estimates, occur. The third paper in this month’s Practice Periodical provides a literature review and data from multiple projects to highlight the efficiency losses that result from very hot or very cold temperatures and from rain and snow. The paper, entitled “Fundamental Principles of Weather Mitigation,” was authored by H. Randolph Thomas, M.ASCE, and Ralph D. Ellis Jr., M.ASCE, associate professor at the University of Florida. The paper presents a principle to account for labor increases associated with adverse weather that will be useful to contractors and owners.

The fourth paper, “New NESC Extreme Ice Loading,” was contributed by Mehran Keshavarzian, M.ASCE, and Charles H. Priebe, M.ASCE. Dr. Keshavarzian is a consulting transmission engineer, and Mr. Priebe is a senior transmission engineer with Commonwealth Edison Company. The paper details the effects of the new NESC-2007 extreme ice load with concurrent wind loading condition on the design of electric utility structures, hardware, and conductors. The new extreme ice load condition is compared with the existing NESC weather-related loading conditions to determine which governs in various regions of the United States. The paper will be useful to utility structure designers.

The fifth and final paper in this month’s Practice Periodical was contributed by our colleagues Sidney A. Guralnick and Lukito Gunawan from the Illinois Institute of Technology. In their paper, “Design of Concrete Members Subjected to Triaxial Compression,” the authors present a new strength theory for the design of concrete members subject to triaxial compression stress using an extension of the Mohr’s strength theory. The new theory is verified against results from 236 tests of normal strength concrete specimen and 50 high strength specimen previously reported in the literature. The paper will be useful for engineers seeking a principle based approach to strength prediction for concrete members subject to triaxial compression.

The editorial board thanks the authors of this issue’s papers, and encourages readers to submit discussion and comment 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 the Periodical.