Practice Periodical on Structural Design and Construction

The American Society of Mechanical Engineers has published a new standard for the design of below-the-hook lifting devices. This standard defines design requirements for lifting devices used in construction and general industry in conjunction with cranes, derricks, and other types of hoisting equipment. The standard establishes two design categories and five service classes that define certain requirements for the design of lifting devices. The design category relates to the expected usage of the lifter and the service class guides the design with respect to fatigue life assessment. Successful use of this design standard requires that designers, manufacturers, purchasers, and users of lifting devices all understand the meanings of these design categories and service classes and apply that understanding to the proper specification of lifter design requirements. This paper provides an extended discussion of the design category and service class definitions and provides guidance to purchasers and users of below-the-hook lifting devices in specifying the correct design category and service class.

The American Society of Mechanical Engineers has published a new standard for the design of below-the-hook lifting devices. This standard defines design requirements for lifting devices used in conjunction with cranes, derricks, and other types of hoisting equipment. Chapter 2 of the standard defines two design categories that establish the design factor used to calculate allowable stresses for the design of the structural elements of the lifting device. This paper provides an extended discussion of the method by which variations in expected structural strength and applied loads relate to reliability and design factors.

The American Society of Mechanical Engineers has published a new standard for the design of below-the-hook lifting devices. This standard defines design requirements for lifting devices used in conjunction with cranes, derricks, and other types of hoisting equipment. Chapter 3 of the standard addresses the structural design requirements for lifting devices. Although most of the design provisions are based on familiar principles and practices, the provisions for the design of pinned connections are significantly different from more common specification requirements. The discussion and analyses presented in this paper demonstrate that these provisions for the design of pin-connected plates provide reliability equal to or greater than that upon which the design factors in the standard are based, thus demonstrating that these provisions are acceptable for the intended purpose of the design of below-the-hook lifting devices. Also discussed is how to address a pinned connection with a large pin-to-hole clearance.

The American Society of Mechanical Engineers has published a new standard for the design of below-the-hook lifting devices. This standard defines allowable stress structural design requirements for lifting devices used in construction and general industry in conjunction with cranes, derricks, and other hoisting equipment. One type of lifting device that is common in construction and that is not specifically addressed in the standard is the stiffened plate lifting beam. Design issues that are applicable to this type of lifting beam are lateral-torsional buckling, combined tensile, and shear stresses in the regions around pin-loaded holes, connections among the built-up elements of the beam, and strength of the lower pin holes. This paper derives a method for the design of stiffened plate lifting beams that is compatible with the requirements of the standard.

The Omega Bridge is a riveted, steel arch bridge built in the early 1950s to cross the Los Alamos Canyon and connect the town of Los Alamos, New Mexico to technical areas of the Los Alamos National Laboratory. The alternate route from the bridge runs through the canyon on a steep grade, which is not a suitable option, particularly for emergency vehicles such as fire trucks. In the early 1990s, the bridge was rehabilitated due to the poor condition of the deck and increased traffic demands, which resulted in several changes to the original structure. This paper discusses the load rating of the bridge as affected by the rehabilitation according to the AASHTO load factor rating method. Attention is given to the evaluation of the floor system components including the stringers, floor beams, and spandrel beams. It is shown that the Omega Bridge is in satisfactory structural condition, no load posting is necessary, and the bridge is safe for the passing of emergency response vehicles.

When a tunnel in rock is dewatered, the steel liner is submitted to an external hydrostatic water pressure, and buckling is often the critical failure mode. In the present case, the steel tunnel liner is considered encased by a competent concrete backfill. This paper presents a simplified graphical method for liner failure due to global buckling phenomena. A local buckling phenomenon is also possible in the shell when stiffeners are required. In this case, a criterion is proposed to evaluate the maximum free spacing between stiffeners and the relationship between steel liner thickness and free spacing of stiffeners is developed.

Municipal infrastructure such as transportation, waste disposal, and utilities are rapidly expanding due to an increase in urbanization. Subsequently, municipalities are faced with having to designate the most effective method of installing new buried infrastructure while being mindful of cost considerations. In order to determine the most feasible underground construction method, various risks and cost factors must be assessed and analyzed. The intent of the study was to compare horizontal directional drilling (HDD) applications with traditional open cut applications. This study is relevant to practitioners and researchers because it identifies and describes risks and factors used in creating a planning tool for small diameter pipelines in an urban environment. The data indicate that utilizing HDD can minimize risks and reduce the overall costs of construction in an urban environment.

This paper follows a companion paper “Progressive Collapse and Earthquake Resistance” (Gurley 2008) dealing with structural design against progressive collapse caused by accidental explosion, terrorist attack, or earthquake. The present paper focuses on those findings/recommendations/implications of the NIST 2005 Final Report on the Collapse of the World Trade Center Towers that relate particularly to proposed changes in structural design practice for fire in tall buildings such as: (1) A new role for, perhaps, a new breed of “fire engineer” as members of building project design teams alongside the established disciplines: architects/structural engineers/HVAC engineers/hydraulic engineers/electrical engineers; (2) a wider role for structural engineers working with fire engineers to carry out structural analysis including fire as a load condition so as to ensure burnout without progressive collapse even if a column is lost and sprinklers fail; (3) more research on sprayed fire resistant materials and better quality control during and after construction “over the life of the building”; and (4) the merits of nonstructural gypsum core walls as opposed to load-bearing concrete cores.

Sustainability is important to the well-being of our planet, continued growth of a society, and human development. Concrete is one of the most widely used construction materials in the world. However, the production of portland cement, an essential constituent of concrete, leads to the release of significant amounts of ${\mathrm{CO}}_2$ , a greenhouse gas (GHG); production of one ton of portland cement produces about one ton of ${\mathrm{CO}}_2$ and other GHGs. The environmental issues associated with GHGs, in addition to natural resources issues, will play a leading role in the sustainable development of the cement and concrete industry during this century. For example, as the supply of good-quality limestone to produce cement decreases, producing adequate amounts of portland cement for construction will become more difficult. There is a possibility that when there is no more good-quality limestone in, say, a geographical region, and thus no portland cement, all the employment associated with the concrete industry, as well as new construction projects, will be terminated. Because of limited natural resources, concern over GHGs, or, both, cement production is being curtailed, or at least cannot be increased to keep up with the population increase, in some regions of the world. It is therefore necessary to look for sustainable solutions for future concrete construction. A sustainable concrete structure is constructed to ensure that the total environmental impact during its life cycle, including its use, will be minimal. Sustainable concrete should have a very low inherent energy requirement, be produced with little waste, be made from some of the most plentiful resources on earth, produce durable structures, have a very high thermal mass, and be made with recycled materials. Sustainable constructions have a small impact on the environment. They use “green” materials, which have low energy costs, high durability, low maintenance requirements, and contain a large proportion of recycled or recyclable materials. Green materials also use less energy and resources and can lead to high-performance cements and concrete. Concrete must keep evolving to satisfy the increasing demands of all its users. Designing for sustainability means accounting for the short-term and long-term environmental consequences in the design.