Practice Periodical on Structural Design and Construction

Tilt-up concrete wall construction is an alternative to cast-in-place, precast, or masonry methods of constructing building walls. The process involves more than just a cast and lift operation. Detailed planning, preparation, scheduling, and safety issues are constantly redefining the process. This paper describes the tilt-up process in step-by-step detail from the panel layout, to the setting of forms, to the concrete placement, and finally to the panel erection. A warehouse/office/shop tilt-up in Tempe, Ariz. is used as a case history of this construction method.

After testing of a full-scale model semimonocoque airframe aluminum bridge at Lehigh University in 1960, New York State built two similar four-span aluminum structures on Long Island, which were opened to traffic in 1965. During an inspection in 1996, galvanic corrosion of the aluminum superstructure at contact surfaces with the steel bearings in presence of moisture, limited distortion or buckling of members at some of these locations, and damage to the bridge underside when struck by a vehicle taller than available clearance were noticed. Otherwise, the rest of the structure appeared to be in good condition. Due to the unique structural configuration, an investigation of viable procedures for repair and maintenance of these structures was conducted. This investigation resulted in the cost-effective rehabilitation procedure described in this paper.

The relationship among the moment, deflection, and buckling load of a structural member is used to develop an elegantly simple and unique expression referred to as the universal column formula (UCF). The UCF relates critical compressive stress to the entire range of member slenderness values for axially loaded columns with or without minor load eccentricity. The UCF is straightforward in appearance and application, yet it is sufficient to perform any axially loaded timber and steel column analysis and design. The UCF unifies the various formulations of column curves common to the field of structural engineering. Comparisons with the secant formula, the Euler curve, and The National Design Specification for Wood Construction and the AISC Design Specifications for Structural Steel Buildings are presented, and a practical application of the UCF is demonstrated.

Many older buildings and farm buildings have been designed with snow load provisions that are lower than the present design code provisions. As a result, some of these buildings have experienced complete or partial roof failure. This paper examines the snow load requirements of two governing building codes and presents a case study where a low-cost, fast-track solution strategy was devised to repair and to retrofit a partially damaged roof in Fargo, N. Dak.

High-performance drill and blast methods for tunnel construction require that each of the individual working elements that constitute the construction process are optimized and considered as a system of sequential and parallel activities. The advantage of integrating the logistic backup systems facilitates an increase in performance. To achieve increased production, it is necessary to improve the drilling, explosive loading, temporary ground support installation—rock bolts, steel mesh, shotcrete, steel sets, lagging, mucking, and logistics. Better blast techniques, partial robotilization, and integration of all systems and processes is also necessary.

Background for the civil engineering design is given, and failure possibilities are provided. Various structural components, including the foundation slurry walls, the design of the column support system, and the performance of the floors are briefly described. The 110-story Twin Towers were constructed 30 years ago and utilized the latest engineering principles; they were stable, and workers as well as visitors often commented that the upper floors were comfortable and any sway was not noticeable during storms.