Editor’s Note

The first issue of 2007 opens with two forums, Structural and Construction. One meaning of “forum” is “a periodical giving an opportunity for discussion.” Doubtless, this was the intention of the originators of this periodical, but as a group, engineers seem reluctant to commit themselves to print. If something fails to perform, the questions of who will pay to fix it and will there be litigation inhibit discussion.

Sometime ago, I was called upon to investigate extensive cracking in a concrete floor topping. A fluid “self-leveling” concrete material had been used. Of course, the floor finishers were delighted to try this material, reducing as it did their physical effort dramatically. Not surprisingly, once winter heat created a dry interior environment, the topping revealed cracks. One wonders why the likelihood of cracking had not been investigated adequately before the material was selected. I hasten to add that no engineer had been consulted, so engineers were not sued in this case.

The cracking floor topping is not something one would normally publicize. However, this example illustrates how useful it would be to other engineers to learn of construction and design problems that might be avoided with careful consideration of the experience of others. A sister ASCE periodical on the performance of constructed facilities specializes in revealing such problems on a grander scale. Possibly we could cover small but nonetheless troublesome problems.

With good reason, it has been suggested that book reviews might be added to this journal, not in a formal manner following receipt of new books from a publisher but based on a reader’s experience with a particular book. The formal procedure can lead to the observation, “Not another academic writing on this topic again.” Nevertheless, I must admit to finding during the past five years an outstanding book on reinforced concrete theory and design and one of equal merit on masonry design, both written by very competent (and it just so happens, Canadian) academic researchers. Our literature seems not to cover construction details that malperform or even fail. To prepare a text on this topic would be a monumental task, but again, it is a subject on which our readers could contribute item by item.

The subject of the Structural Forum is fire-resistant design of concrete, masonry, and wood, contributed by my coeditor of Forums, Nestor Iwankiw. Essentially, it is part of an ongoing discussion on fire-resistant design, but to the reader who jumps in at the middle, this may not be totally clear. The series was initiated by Alfawakhiri and Carter’s article in February 2005 on the fire-resistant design of structural steel. This article is not reprinted here but discussion by Longinow, Mniszewski, and Miller is presented, together with the response of the original authors. Iwankiw has completed the presentation here (but one senses not the discussion), by addressing the topic of fire-resistant design of other structural materials, namely concrete, masonry, and wood.

Cliff Schexnayder has prepared for the Construction Forum an account of part of the career of an early American civil engineer, Herman Haubt. Schexnayder covers Haubty’s career up to the time he left the Pennsylvania Railroad to work on the Hoosac Tunnel in Massachusetts. One is more likely to read and enjoy these short articles than full biographies. Quite interesting aspects of these articles are both the manner in which the designer overcame the not always correct flow of forces and how the structure was to be built. By a back-road detour near the English–Welsh border, I once saw the last of many iron bridges conceived by Thomas Telford in about 1800. My wife, who was there with me, said, “Is this all there is?” I explained to her that the bridge could be fabricated in several parts, transported on wagons, and erected without need of the falsework in the river required for stone bridges.

Five articles have been contributed to this issue of the Periodical. The first discusses an unusual procedure to the tendering and procurement of correctly fabricated structural steel for the rebuilding of the steel plate I-girder and steel box girder bridges forming part of the Marquette Interchange at Milwaukee. Preliminary shop drawings, prepared during the design stage in close cooperation with the designers, were provided to bidders. The objectives were to ensure that complexity of the design intent would be understood, minimizing errors that might delay fieldwork, ensuring that bidders clearly understood what was required of them and reducing time on final shop drawing preparation. The second named author’s firm prepared the preliminary shop drawings.

Foundations for integral bridge abutments are discussed in the second paper by engineers from the Iowa Department of Transportation and a bridge design consultant. Consideration is given to the effect of an array of types of pile foundations in addition to spread footings. Various site situations, such as skew and fixed and free abutments, are considered. It is claimed that the reduction in number of expansion joints required, or their complete elimination, coupled with simplification of design, detailing, and construction justify this approach. Certainly, the reduction in number or complete elimination of expansion joints, with their associated maintenance, poor ride quality, and potential hazard, is a worthwhile objective. This is highlighted by the recent (October 2006) tragic failure of an overpass in Montreal, which resulted in five deaths of occupants in cars underneath. A probable cause is thought to have been deterioration at the abutment arising from salt water leaking through the expansion joint.

The third paper, which discusses computation of the peak dynamic response of turbo generator pedestals using modal synthesis, was prepared by the staff at a structural engineering research center in India. Since design of turbine pedestals is not a frequently required task of many engineers, the value of this paper lies in its application of the technique to other equipment support structures.

Timing is of prime importance in the repair of bridges if traffic use is to be restricted during construction. In technical periodical reporting, railway bridges are frequently featured because of the complete occupancy requirement, but prolonged highway bridge repair can cause much complaint when traffic is disrupted. The paper by Umphrey et al. addresses replacement designs for the Georgia DOT, employing propriety precast concrete deck panels used in staged construction with concurrent traffic. Of the four authors, two are practicing engineers in Huntsville, Ala, and two are academic engineers from Auburn University, Ala.

This issue contains a mix of fairly generally understood topics and highly specialized ones. The last paper addresses a special aspect of a fairly widely appreciated problem, that of stress concentrations in weldments that may lead to fatigue problems. I recall complaining that the section on fatigue in welded joints in the Canadian steel design standard addressed only bridge details. There was nothing appropriate for a simple light standard pole welded to a base plate. The last paper deals with tubular welded joints of a totally different magnitude, namely offshore tubular structures, but presumably the principles are widely applicable. The four authors are all affiliated with the University of Queensland in Brisbane, Australia.