Practice Periodical on Structural Design and Construction

Estimating shear wall and diaphragm deflection is important for several reasons, including (1) classifying diaphragms as rigid or flexible; (2) estimating intrastory drifts to compare to code specified limits; and (3) estimating the potential for excessive deflection, which may cause costly damage. Historically, shear wall and diaphragm deflection has not been a critical design consideration. Much more attention has been paid to this issue after the 1994 Northridge, Calif. earthquake. The Northridge earthquake caused designers and code officials to place more emphasis on deflection, specifically for classifying diaphragms as either rigid or flexible. Building code changes that limited the use of narrow shear walls were also a result of the Northridge earthquake. Although building codes have provided methods for estimating diaphragm and shear wall deflection, this information is scattered and incomplete. The intention of this paper is to provide a comprehensive summary of the currently recognized methodologies for calculating shear wall and diaphragm deflection.

Circular base plates are commonly used for pipe columns, such as pylons in cable-stayed bridges, lighting poles, and electric power line posts. Although the explicit solutions for rectangular base plates can be found in many textbooks and AISC design procedures for base plates, a design procedure for circular base plates has not been documented. In this paper, two equilibrium equations are presented for circular base plates with large eccentric loads. Since these two equations cannot be solved explicitly, an iteration approach is used to solve them.

This paper describes important engineering features relating to the seismic evaluation of a school building system in southern Indiana. This evaluation is the first step in identifying deficiencies in the school’s seismic force resisting system and may ultimately be a reference for retrofitting the structure to be in compliance with current design standards. This paper is intended to provide an introduction to the engineering challenges of seismic retrofitting of school structures in the Midwest, with particular reference to the Glenwood Middle School located in Evansville, Indiana. To this end, the paper presents the numerical modeling and analyses to establish a retrofitting scheme that would provide a structurally stable system under seismic loading conditions.

This paper presents a parametric study of the effect of potholes on load distribution in reinforced concrete slab bridges using finite-element analysis (FEA). Parameters such as the span length, slab width, pothole location, and wheel load conditions on simply supported one-span reinforced concrete slab bridges were investigated. Four typical span lengths were considered in combination with one, two, three, and four lanes. A total of 65 highway bridge study cases were analyzed. It was assumed that the bridges were stand-alone structures carrying one-way traffic. Design trucks were placed close to one edge of the slab, with the absolute minimum spacing between the trucks in order to predict the worst loading conditions. Previous studies validated the use of the AASHTO standard specifications design procedures when designing slab bridges. A typical bridge was selected to determine analytically the optimum thickness and critical location of the pothole(s) in any lane at midspan. The presence of one or two potholes $[0.6m\times 0.6m(2\mathrm{ft}\times 2\mathrm{ft}\left)\right]$ in the first two lanes created at the midspan of a bridge increased the maximum longitudinal bending moment by about 25% when compared with FEA results of slabs with no potholes, and by as much as 70% when compared with the AASHTO standard specifications. However, the new AASHTO LRFD design procedure overestimates the design moment in the concrete slabs with one or two potholes by about 20%. Therefore, the AASHTO LRFD design approach appears to account for the potential deterioration in the design of new concrete slab bridges. This paper will assist bridge engineers in comparing the two AASHTO design procedures as well as performing a realistic evaluation of the load carrying capacity of existing highway bridges.

For the past 36 years there has been an enormous explosion of means to prevent litigation in the construction and engineering industries. ASCE has been in the forefront of shaping this process through its participation in the National Construction Industry Dispute Resolution Committee (formerly the National Construction Industry Arbitration Committee). ASCE, by supporting the American Arbitration Association’s efforts and participating in its deliberations, has derived the benefits of having at the disposal of its members many time- and cost-saving methods of resolving their disputes. The history of dispute resolution and ASCE’s participation in the process updated to the present, 2003, is set forth in this paper.

The presence of gravel and cobble during horizontal directional drilling (HDD) operations is one of the most challenging situations encountered by contractors. An unexpected encounter with this soil condition often results in difficulty or even failure in completing the bore. This paper presents the results of field research in which three 61 m (200 ft) installations (bores) of 100 mm (4 in.) high-density polyethylene pipe were performed in gravel/cobble conditions. Each of the installations was completed using various combinations of drilling fluids to demonstrate the effectiveness of using fibers to increase the chances of success. The first installation was completed using a traditional bentonite/polymer drilling fluid mixture, while the second and third installations were performed with fiber additives mixed into the drilling fluid to provide mechanical suspension of the cobble/gravel formation. The results demonstrated that increased productivity and flow of returns could be achieved with proper drilling fluid considerations. Overall, the third installation experienced a 25% increase in productivity from the second installation and a 67% increase from the first installation through the use of two fiber additives in combination. The results of this research should assist HDD contractors in improving the success rate of installations in gravel/cobble conditions, resulting in significant cost savings in fluid usage, mixing time, and problems associated with inadvertent returns.

The flexural performance of box beams under eccentric edge loading is discussed in this paper. Physical tests show that the combined effects of edge loading and the connection of the two primary box beam components (toe-to-toe joists), by top and bottom track members, may reduce the overall strength of the box beam. In the test results reported here, the mode of failure was predominantly beam instability due to twisting. In some cases, this instability was accompanied by elastic local buckling. Ignoring any composite action between the connected components of the box beam, the combined flexural strength of the primary beam components (joist members) was computed and compared with the measured capacity. This comparison showed that, based on the measured yield strengths, edge loading has a tendency to reduce beam capacity. These limited test results suggest that additional work should be undertaken to evaluate similar edge loading conditions that are commonly found in cold-formed steel framed structures.