Practice Periodical on Structural Design and Construction

Although flaggers are often an integral component of temporary traffic control measures during roadway construction and maintenance, they may be exposed to significant safety hazards associated with the inadequate illumination of flagging operations. To eliminate these hazards, guidelines are needed that provide specific direction and recommendations for optimal illumination of flaggers. This paper presents the findings of a research study that included the evaluation of selected light equipment under actual working conditions and the development of recommendations for flagger illumination. Three types of light equipment were selected for the study: a 12-V spotlight, a 12-V high-intensity discharge (HID) floodlight, and a light tower with a 2,000 W output. Light equipment testing was performed on two projects in the state of Oregon. The findings reveal that flaggers do not feel comfortable when using 12-V spotlight and 12-V HID floodlight systems because of the small amount of light these systems emit compared with a light tower. Project sites containing a greater number and intensity of surrounding artificial lights require light systems with a greater output to illuminate the flagger. One safety problem incurred was that glare from the light tower created a hazard for motorists. However, there was no similar glare hazard for the 12-V spotlight and floodlight. The study revealed site features and flagging operations that can negatively impact the quality of flagger illumination. Two practical tools were developed as a result of the study to assist setting up and performing nighttime flagging operations in a safe manner: a flagger-illumination checklist and a flagger-illumination assessment flowchart. The flowchart is used before flagging operations begin to help plan the operation. The checklist provides guidance for assessing the flagger-illumination requirements on a work site, selecting the appropriate light equipment to use, and determining the appropriate location and setup of the equipment.

This paper describes the results of a study to develop fundamental principles of subcontract management. Fundamental principles are actions a general contractor can take it improve job performance. In developing the principles, there was significant interaction with industry professionals. The principles are organized into two broad groupings: managing people and managing the subcontractor’s work. There are a total of 21 principles listed. These are easy to comprehend and implement. If implemented, they will likely yield immediate and positive results.

Rectangular openings in structural members are used to allow the passage of services. Special design considerations are required to compensate for the reduction in stiffness and to minimize fatigue cracks in the web. The paper investigates the behavior of deep plate girders with rectangular openings with applications to oil and gas facilities. An efficient numerical procedure is first presented for analysis of webs with rectangular penetrations. The limitations of the current AISC guidelines and Canadian design procedures are also highlighted. Recommendations are proposed for structural engineers to minimize web stresses in the girder. The influence of these penetrations on the performance of the plate girder is also illustrated for several loading conditions. It is shown that for openings with aspect ratios $(\alpha /\beta )>1$, the stress decreases as the opening radius of curvature ($r$) increases. Also, the location of the maximum stress is largely influenced by the opening aspect ratio ($\alpha /\beta$). It is also shown that a slow increase in the web maximum stress results when the opening curvature $(r)<40\mathrm{mm}$. For plate girders under shear loading, the web stress decreases by increasing the opening curvature ($r$).

Roof coverings, particularly barrel tiles, have experienced significant damage over the last few years from storms, even weaker storms such as Category 1 Hurricane Wilma in 2005. Efforts have been made to ban mortar-set attachments in southern Florida in favor of adhesive sets. Moreover, some homeowners have generalized the poor performance of clay or concrete tiles in favor of one or the other. This study aims to address 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 detailed experimental study revealed the strongest system to be concrete tiles with mortar, both for uplift capacity and impact resistance. Although concrete tiles bond to mortar much better than clay tiles, clay tiles adhere better to the foam adhesive. Concrete tiles were also shown to perform better than clay tiles when impacted by a traveling projectile. Test results do not support the ban on the use of mortar for hip and ridge tiles. It is suggested that any such ban on mortar should be limited to clay tiles only. The study also showed cyclic testing to more accurately represent the uplift capacity of tiles for real hurricane conditions. In contrast, the monotonic testing used by tile manufacturers across the industry was found to overestimate the uplift capacity of tiles by as much as 40%.

A sudden and catastrophic failure occurred at a newly constructed dike facility, designated Dikes 19 and 20, along the east side of the Dead Sea shoreline in the Middle East. The failure occurred at approximately 4:30 p.m. on March 22, 2000, resulting in the release of approximately 55 million cubic meters (approximately 72 million cubic yards) of brine and the washing out into the Dead Sea of a 2.6 km (1.6 mi) section of Dike 19. After the engineering assessment of the failure was completed, the owner decided to move forward with a reconstruction plan, reinstating the failed section and rehabilitating the section that did not fail. Accordingly, three viable conceptual reconstruction alternatives were developed for further evaluation. A judgmental risk-based analysis was performed to evaluate the proposed alternatives. Subsequently, a decision tree analysis was performed to assist the owner in making the final decision for the alternative with the lowest risk and reasonable cost. The purpose of the risk analysis was only to determine which reconstruction method would have the lowest comparative risk level. The risk analysis was not intended to simulate the actual cause of failure. This article discusses the decision-making approach based on a fault tree analysis and the comparative risk of failure estimated for the three reconstruction alternatives designated as Alternatives I, II-A, and II-B. The overall risk of failure for each alternative was quantified and compared. Alternative II-B was found to have the lowest risk indicator. In addition, on the basis of risk indicators and construction cost, a decision tree was developed, and Alternative II-B was found to offer the most favorable option for the reconstruction of the failed portion of the dike.