Editor’s Note

This issue of the Practice Periodical includes five articles and one case study. Their summaries are given in the following paragraphs.

The first article deals with mitigation of hazards at construction sites. In particular, it deals with hazards faced by flaggers during roadway construction and maintenance due to inadequate illumination of flagging operations. There have been a number of accidents resulting in injuries and construction work stoppage. This resulted in a research study evaluating various types of standard construction site illuminating equipment under actual working conditions. This included a 12-V spotlight, a 112-V high-intensity discharge spotlight, and a light tower with 2,000-W output. Testing was performed on two projects in the state of Oregon. The study resulted in illumination requirements to properly illuminate the flagger without introducing glare to motorists, as well as construction site features that need to be considered in setting up flagger illumination. Practical tools, in the form of a flagger illumination checklist and flagger illumination flowchart were developed and are described in this article.

Effective subcontractor management is the focus of the second article. This is paramount in producing efficiency and economy in a construction project. Fundamental principles discussed in this paper are actions a general contractor can take to enhance job performance. The set of 21 principles presented were formulated by the authors after an intensive interaction with industry professionals. They are organized into two broad groups, i.e., those dealing with managing people, and those managing subcontractor’s work. The authors believe that, if implemented, these principles will yield immediate and positive results.

Rectangular openings in structural members are used to allow for the passage of services. Special design considerations are required to compensate for the reduction in stiffness and minimize fatigue cracks in the web. The third paper investigates the behavior of deep plate girders with rectangular openings with application to oil and gas facilities. An efficient numerical procedure is first presented for analysis of webs with rectangular web penetrations. The limitations of the current AISC guidelines and Canadian design procedures are highlighted. The influence of such penetrations on the performance of the plate girder is illustrated for several loading conditions.

Roof coverings such as roof tiles and particularly barrel tiles have experienced significant damage over the last few years even from weaker storms, such as Category 1 Hurricane Wilma in 2005. Efforts have been made to ban the mortar-set attachments in South Florida in favor of adhesive sets. The study described in the fourth paper aimed at addressing whether there is a significant difference in the uplift capacity and impact resistance of field and ridge tiles of clay and concrete with either mortar-set or adhesive-set attachments. The experimental study revealed the strongest system to be concrete tiles with mortar, both in terms of uplift and impact resistance. Although concrete tiles bond to mortar much better than clay tiles, clay tiles adhere better to the foam adhesive. Test results do not support the ban on the use of mortar for hip and ridge tiles.

A sudden and catastrophic failure took place on March 22, 2000, at 4:30 p.m. to a newly constructed dike facility along the east side of the Dead Sea shoreline in the Middle East. In addition to significant structural damage, the failure also resulted in the release of approximately 55 million cubic meters of brine and the washing out into the Dead Sea of a 2.6-km long section of one of the dikes. After assessing the extent of damage, the owner decided to move forward with reconstruction of the failed section of the dike facility, and rehabilitation of the portion that did not fail. Three reconstruction alternatives were developed for further evaluation. A judgmental risk-based analysis was performed on each of the alternatives followed by a decision-tree analysis of each. The purpose was to determine which reconstruction alternative would have the lowest comparative risk level. The fifth paper discusses the decision-making approach for the three reconstruction alternatives and results obtained.

Thirty years ago, on July 17, 1981, two walkways in the Hyatt Regency Hotel in Kansas City, Missouri, collapsed, killing 114 people and injuring 216 others, many of which were permanently disabled. Two steel walkways were stacked one on top of the other and suspended from the ceiling above. The top walkway fell on the bottom walkway, and the two fell to the floor of the crowded atrium below. In terms of the number of casualties, this collapse was the worst structural failure in the history of the United States. This case study discusses the cause of collapse, design and construction issues, as well as ethical and legal issues associated with this collapse.