Heavy Crane Research Articles

Noise Exposure Profile Among Heavy Equipment Operators, Associated Laborers, and Crane Operators

This study, conducted in 1987 and 1988, has made it possible to quantify exposure to noise among heavy equipment operators, associated laborers, and crane operators. The average daily noise exposure was 84 to 99 dBA for heavy equipment, 90 dBA for the laborer, and 74 to 97 dBA for the crane operator. The main sources of noise to which heavy equipment operators are exposed are vehicle engines and the muffler exhaust system, usually located near the operator. The presence of insulated cabs such as those found on power shovels, backhoes, wheel loaders, and graders help reduce noise exposure. The type of tasks carried out by the laborers, the sources of noise from heavy equipment around which they work, and the manual equipment they use determine the noise levels to which such workers are exposed. In the case of crane operators, an insulated cab significantly reduces the operator's exposure to engine noise.

ALTERNATIVE PROCEDURE FOR THE ASSEMBLY ANDINSTALLATION OF TLP TENDONS

The assembly and installation of the Shell Auger and Mars TLP tendons was performed in segments, using a heavy crane vessel to build the tendon columns in the vertical position, thus avoiding having to upend them. The corresponding segments were added on to the top, one at a time, using a purpose built connector, after which the column was lowered into position for the next segment. The cost of this operation had a great impact on the price of the tendons, not only because of the connectors, but also due to the vessel costs over the period required to perform this assembly. In order to try to reduce the tendon costs for the next Shell TLP coming on schedule, Ursa, an alternative assembly and installation procedure was investigated, based on the sizes of the Auger tendons. The main object of this study was to prove the technical feasibility of a solution, in which the tendons would be assembled in a yard, floated out in a bundle and, finally upended at or near the installation site. This paper contains a description of this study regarding the bundle assembly and the technical solutions required in order to upend a long and slender bundle of tubes within code stress limitations. INTRODUCTION The study described in this paper will be evaluated, by comparison with the results of other installation alternatives, in order to choose that, which is technically and economically most efficient for the installation of the tendons of the upcoming Shell Ursa TLP. Considering, however, that information regarding costs of the Auger Platform tendon installation was already available, it was decided that the alternative feasibility study should be Transactions on the Built Environment vol 29, © 1997 WIT Press, www.witpress.com, ISSN 1743-3509 168 Offshore Engineering performed for the Auger tendon sizes and extended, at a later date, for Ursa only if and when the alternative is chosen. The object of this study is, therefore, to provide a solution for bundling together twelve 28-inch diameter, 870m long tendon pipes, which will be pulled into the water, towed out to the installation site, upended in a single piece and, only then removed, one at a time, from the assembly frame without destabilizing the remaining bundle. The work performed in order to reach a frame meeting the requirements of each of the phases mentioned above, obviously, went through several design cycles, but only the final configuration will be presented. Nevertheless the most important design restraints will be emphasized. The design was performed for the actually installed Auger tendon sizes and weights, but a much lighter assembly frame could have been achieved if the tendons had been designed close to neutrally buoyant. Obviously in this case the corresponding increase of the tendon weight would also have to be evaluated and considered. DESCRIPTION OF THE ASSEMBLY Construction and assembly was assumed to take place in a yard long enough to build the twelve tendons side by side, spaced so that cranes can move freely between them, in order to perform the assembling operations. The yard should be equipped with a railway, that extends into the water, on which the tendon bundle will be assembled. The tendon assembly will be supported by conveniently spaced trolleys, which will run the structure into the water until the bundle is lifted off the trolleys, as it becomes buoyant. Figure 1 presents a general view of the bundled tendon structure, where the following components can be identified: The 12 tendons equally spaced around a 6m diameter circumference; A 1.5m diameter tank extending along the entire centerline of the bundle, except for the two ends. This diameter was chosen so that it's buoyancy plus that of the 12 tendons was approximately neutrally buoyant. These tanks were assumed pressurized near the bottom; Two 5m diameter tanks at the two ends of the assembly. The bottom one will be flooded in the beginning of the upending sequence to keep the longitudinal tank under tension, in order to prevent it from buckling, while the top one, never flooded, is required to provide the necessary system stability; Transactions on the Built Environment vol 29, © 1997 WIT Press, www.witpress.com, ISSN 1743-3509 Offshore Engineering 169

Dome-Shaped Space Trusses Formed by Means of Posttensioning

Dome-shaped space trusses can be derived from a flat configuration by means of posttensioning. The structure considered here is devised to be a near mechanism initially and during the posttensioning operation. It is a near mechanism as only the flexural stiffness of the continuous top chords provides any resistance to deformation. Therefore, no appreciable force is induced in the members of the structure during the shape formation process. The results of experimental and theoretical work on the shape formation of a dome-shaped space truss by means of posttensioning are presented herein. An analytical procedure that includes both geometric and material nonlinearities is developed to determine the final shape of the dome-shaped space truss, using commercially available finite-element software. The ultimate aim is to lead to significant economies in the construction of large-span lightweight structures by eliminating or minimizing the need for scaffolding and heavy cranes in the shaping and erection of such structures.

Frost-Thaw Effects on Ballasted Track

The multiple failures of a ballasted track 877 m long built to guide the wheels of a heavy gantry crane used in a logging yard in northern Alberta, Canada, are described. At the time of construction the crane was claimed to be the heaviest, and its wheels were supported by a ballasted track with wood lateral members (ties). The track was built in 1985 but exhibited excessive differential vertical and lateral deformations in subsequent years. The focus is on failure of a track related to freeze-thaw conditions and the solution to track instability problems, which was achieved geotextiles.

Frost-Thaw Effects on Ballasted Track

The multiple failures of a ballasted track 877 m long built to guide the wheels of a heavy gantry crane used in a logging yard in northern Alberta, Canada, are described. At the time of construction the crane was claimed to be the heaviest, and its wheels were supported by a ballasted track with wood lateral members (ties). The track was built in 1985 but exhibited excessive differential vertical and lateral deformations in subsequent years. The focus is on failure of a track related to freeze-thaw conditions and the solution to track instability problems, which was achieved geotextiles.

Practical Approaches in Mill Building Columns Subjected to Heavy Crane Loads

Since the turn of this century, the amount of analytical and experimental research in the area of column design has been extensive. While the information and results of such research is scattered and narrowly focused in very specialized areas, identification of this vast amount of relevant information available is often difficult. There is no legal code governing the design of heavy mill building columns and the designs are based on experience and judgment. Additionally, there are varying types of mill building columns due to assumptions and geometry. This has led to a design practice that varies from one designer to another, based on their experience and knowledge of the mill buildings. For a practicing engineer it is essential to analyze, integrate, and establish a logical and comprehensive design methodology and procedures. It is not possible to establish one generic approach applicable to all types of mill building columns. It is rather easier to deal independently with each type of these complex structural elements in achieving this goal. This paper presents a design methodology and procedures for "heavy mill building columns" subjected to heavy crane loads. For the purpose of this paper heavy crane loads are defined as loads imparted by cranes with lifting capacity ranges from 100 tons to 500 tons such as hot metal cranes. These columns consist of two or more shafts and are laced together to achieve composite behavior. The column bases are fully fixed and the roof trusses are simply supported at the top of the building shaft. The bottom chords of the trusses are braced the full length of the building. Other types of mill building columns are not included in the scope of this paper. Therefore, the procedures and methodology presented herein may not be directly applicable to any other type of mill building column.

New method for testing linear and angular dimensions in the construction of heavy cranes

New method for testing linear and angular dimensions in the construction of heavy cranes

Cranes: their Construction, Mechanical Equipment, and Working

MODERN developments of means of transit, especially in the direction of the transhipment of heavy goods, have made it necessary that rapid and powerful lifting gear should be devised, and pari passu with the developments of heavy engines and wagons, heavy ordnance and large ocean liners, there has been an equally interesting and important advance in the construction of rapid and heavy cranes. Cranes: their Construction, Mechanical Equipment, and Working. Anton Böttcher. Translated and supplemented with English, American, and Continental Practice by A. Tolhausen. Pp. xvii + 510 (London: A. Constable and Co., Ltd., 1908.) Price 42s. net.