Practice Periodical on Structural Design and Construction

Hot-rolled, heavy-gauge steel sheet piling has advantages over other available products including concrete, vinyl, and fiberglass-reinforced polymers for bulkhead and deep-excavation applications. For FEMA seawall bulkheads, steel sheet piling provides the only practical structural solution available. For deep excavations, steel sheet piling typically provides the most economical solution for the conditions encountered in braced trench and cofferdam construction. A steel sheet pile wall consists of a continuous row of interlocking vertical segments that form essentially a straight wall that is capable of acting integrally. There are two primary types of steel sheet pile wall structures: cantilevered and anchored. Walers are commonly used in conjunction with tiebacks to construct anchored sheet pile walls. Tiebacks are typically installed as either ground anchors or anchor rods secured to deadmen. Cofferdams are a special form of steel sheet pile construction in which the method of resistance to soil forces is provided through the ability of the circular footprint to function either as a compression or tension ring. The design of sheet pile walls involves the evaluation of loads imposed by soil, water, surcharging, and other externally applied forces. The analysis of a sheet pile wall includes a determination of the required depth of embedment, sizing of any anchorage systems, and verification that the actual flexural stresses do not exceed the allowable. Safety factors are typically included in the determination of the minimum embedment depth.

The objective of the study was to determine the heat and moisture behavior of slab-on-ground structures by in situ monitoring of real structures and numerical analysis. The subgrade under the insulated slab of the heated building warms up to the equilibrium temperature, which varies between $+15$ and $+17°C$. Furthermore, the relative humidity of the subgrade pore air is close to $\mathrm{RH}=100\%$. The hygroscopic moisture of the subsoil is more essential in moisture design than capillary movement, which should be prevented. The moisture condition of the slab-on-ground structures alters radically during the life cycle of a structure. At least three divergent characteristic situations can be distinguished, and all three must be considered during the design process: (1) construction phase and excess structural moisture; (2) operational life of the building; and (3) damage control and repair survey.

This paper presents a discussion of the Manufactured Home Construction and Safety Standards (MHCSS) Part 3280 that were revised in the aftermath of Hurricane Andrew. The emphasis is on wind loading and anchorage of housing units. Anchoring systems used to resist lateral and lift wind forces are described and discussed in the light of previous and recent field and laboratory studies. Research to produce anchoring systems that do not rely on auger anchors is recommended.

This paper evaluates the American Association of State Highway and Transportation Officials (AASHTO) line load and live load distribution factors. The standard AASHTO formulas for live load in some cases underestimate the live load moments by as much as 40%. The AASHTO distribution of line loads (dividing the loads equally among all girders) results in even larger underestimates of line load distribution, leading to unsafe designs. This paper shows how more reliable distribution factors can be obtained for line loads, AASHTO truck loads, and non-AASHTO live loads. A user-friendly computer program for calculating distribution factors is discussed. A useful concept for analyzing beams of variable section (equivalent girder) is also discussed.

The village of Cookville, Vermont, has a well-preserved and well-defined historic district and an 80-year-old bridge that served to link the historic district to the village center. In 1997, that old bridge needed to be replaced. The new bridge located in Corinth, Vermont, is a graceful blend of aesthetics and function; the bridge is a substantial departure from typical precast or cast-in-place concrete bridges. The construction of this bridge combined the use of standard construction practices with the use of a special forming method and a unique concrete staining process to create special aesthetic concrete surfaces. The final result was a bridge that appears as if it was built by a stonemason, using stones from the brook that runs underneath it.

The booms of two barge-mounted hydraulic excavators experienced substantial fatigue cracking during normal operation. Fatigue cracking of the smaller excavator, a Liebherr 994 known as the Hercules, occurred at a slower rate than the larger excavator, a Liebherr 996 known as the Antone. However, one crack on the Hercules boom went undetected so long that it grew to a critical length and the boom fractured. Because of the Hercules failure, the prior occurrence of several cracks on the Antone, and the anticipated difficult dredging in the coralline material at the Port of Miami, in Miami, Florida, the owner of the excavators sought assistance in mitigating the risk of damage to the Antone. To control the risk of fatigue cracking, the investigators decided to repair any existing cracks so the structure complied with ANSI/AWS requirements for a cyclically loaded structure; install strain gauges on the structure and perform static and dynamic load tests to determine the strain characteristics of the structure; and develop a structural maintenance program.

The paper describes the geotechnical and structural, reliability-based design of micropile foundations for a factory in Costa Rica, along with its construction issues. The chaotic nature of the very loose soil led the designers to substitute micropiles for the driven piles originally called for in the final design. The same chaotic nature of the soil made any deterministic prediction of the pile lengths impracticable, and the designers developed an original and ad hoc reliability-based procedure to cope with the problem. The area was seismically active, with a maximum considered earthquake spectral response acceleration at short periods $\left(0.2s\right)$ equal to $1.04g$. In order to lower costs and to improve the surrounding ground, the micropiles were specially engineered by the designers, who acted as consultants for the foundation specialist subcontractor. The field test gave excellent results, and negligible elastic deformations were recorded up to 1.5 times the design load. This is a positive example of international collaboration among a Costa Rican client, a Spanish general contractor, and Italian subcontractors and consultants. The mutual understanding, knowledgeability, and open-mindedness of all parties involved (client, general contractor, subcontractors, designers) resulted in a reliable and cost-effective design and construction.

This paper describes the renovation of a circular concrete water tank that had suffered significant deterioration in its dome. After a feasibility study, it was determined that the most desirable solution consisted of the replacement of the existing concrete dome with one made of structural aluminum. The key features of the construction work, including existing dome demolition and installation of the new one, are presented herein with the intent of providing a case study to engineers, contractors, and owners facing similar challenges.