Practice Periodical on Structural Design and Construction

Like other industries, engineers, contractors, and construction/project managers in the construction industry are continuously searching for means, methods, and materials that will give them an edge to be more efficient in terms of cost and/or time. Some of these tools come in the form of a new piece of equipment or breakthrough product with multiple uses. It is people, though, that are the key resource of the construction industry. Thus, construction workers can also be looked to for gaining an advantage. This can be done by setting up projects so that the workers can make better use of their time while on the job. One such example is implementing the four day, $40\mathrm{h}$ workweek in lieu of the traditional five $8\mathrm{h}$ days. This paper will explore the merits of utilizing such a system in the construction industry, outline some of its impacts on a project and the workers, present a multiattribute utility function for determining its effectiveness, and conclude with a recommendation on its use.

Composite girders consisting of concrete deck on built-up girders are frequently used in bridge construction for their economic advantages. The use of composite girders results in a very economical design. Additional savings can be obtained in design and material costs for some members by automating design approaches based on optimization techniques. This paper describes the use of EXCEL Solver to find the minimum weight for a composite trapezoidal box cross section for a two lane bridge. Design aid tables were generated for structural steel Grades 250, 345, 485, and $690\mathrm{MPa}$ , and different spans varying from $3.0–100\mathrm{m}$ . The search for the minimum cross section used in this research satisfies the 17th Edition of the American Association of State Highway and Transportation Officials Specifications—Load Factor Design method.

Including diaphragm action in sizing building posts (columns) and postembedment depths (foundation) is more consistent with the actual building performance. A large portion of in-plane loading, such as wind, is transferred to the end walls through in-plane shear via metal roofing—a phenomenon called “diaphragm action.” Because of load sharing and redundancies that are not accounted for, postframe buildings are stronger and stiffer than what is normally assumed. Various construction and design practices that increase diaphragm strength and stiffness of postframe buildings are discussed. The objective of this paper is to discuss design and construction practices that contribute to the diaphragm strength and stiffness of metal-clad postframe rectangular buildings. The paper is based on data and information obtained from the full-scale metal-clad timber-framed postframe building tested over a period of 9 years, and the literature. Understanding the functions, contributions, interactions, and load sharing characteristics of the different framing, cladding, and redundant elements is critical in understanding the diaphragm action and optimizing designs of postframe buildings. The study benefits the engineers, architects, builders, and code officials of postframe buildings.

Construction of intermediate diaphragms is an extra cost financially and in scheduling. Practice of intermediate diaphragms in prestressed concrete bridges is still controversial, and the practice in each state is different. This paper presents a review of the state-of-the-art practice regarding intermediate diaphragms of prestressed concrete bridges. Through a critical review, issues regarding the intermediate diaphragm effects on bridge performance are discussed. It is found that the ways to model the intermediate diaphragms make a significant difference on the results, and it is crucial to quantify the actual stiffness contribution of the intermediate diaphragms. Through field inspections, more specific information has been acquired for the current practice in Louisiana. This information is of invaluable help for developing finite element analysis and for the research team to make sound recommendations regarding the practice of intermediate diaphragms. The presented information will also help other states in examining the functions of intermediate diaphragms and in developing their policies of practice.

The design, manufacture, testing, inspection, and use of below-the-hook lifting devices are standardized in the United States by ASME B30.20 Below-the-Hook Lifting Devices. Prior to the issuance of B30.20, there were no broadly applicable standards for the design and use of lifting devices used with cranes and derricks. This standard contained only a very basic structural requirement that lifters be designed based on a design factor of three with respect to yield strength. This requirement produced a number of requests to the B30.20 Subcommittee for clarification and a certain amount of confusion in industry as lifting equipment designers developed interpretations with respect to aspects of design for which yielding is not a practical limit state. ASME responded to these queries by developing the new design standard BTH-1-2005 Design of Below-the-Hook Lifting Devices. This paper documents the history of the development of B30.20 and BTH-1 from the inception of the B30.20 Subcommittee through the first issue of BTH-1 and documents certain key decisions made during the development of BTH-1. Particular emphasis is made on the structural design requirements for lifting devices.