Showing papers in "Civil engineering for practicing and design engineers in 1983"

Dynamic uplift capacity of helical anchors in sand

Abstract: Earth anchors are becoming a very useful technique for securing temporary and permanent foundation systems subjected to uplift loads. In recent years, helical anchors have become more widely used because of their ease of installation and low cost. Past research has concentrated on static loading. Recent investigations into the cyclic capacity of anchors have increased rapidly due to increased construction in the ocean and the importance of anchors in advancing offshore technology. Laboratory tests were performed with one-quarter scale single-helix model anchors in dry sand at a constant relative density and embedment depth. The two parameters investigated were the displacement amplitude and prestress load. Appropriate equipment and instrumentation were used to monitor anchor deflection, dynamic load, and horizontal soil stresses during the cycle tests. Static tests were performed to determine the ultimate pullout capacity of dead anchors and the postcyclic failure capapcity of anchors. It was concluded that screw-in anchor installation technique and the application of a prestress load both produced an increase in horizontal soil stresses and soil densification in the vicinity of the single-helix anchor. Cyclic loading caused a reduction in horizontal stress and an upward cyclic creep of the anchor. Reduction of horizontal stress occurred until the active failure stress was approached. At this point, the sand had loosened and the anchor began to pullout rapidly. The post-cyclic static capacity was found to be lower than the ultimate static capacity of a dead anchor. In the prestress range investigated, a critical ratio of dynamic load to effective static capacity exists. Above this critical ratio, a failure of a prestressed anchor will occur earlier than a dead anchor failed by cyclic loading. Prestressed anchors below this critical ratio will experience an increase in anchor life.

Guidelines for applying criteria to designate routes for transportating hazardous materials

Abstract: Le transport de matieres dangereuses est essentiel pour les activites jour apres jour de presque toutes les classes de la societe. En meme temps le public est de plus en plus concerne par la securite de l'embarquement de ces matieres dangereuses. Utilisation d'une methode d'approche de l'analyse de risques. Des personnes avec peu ou aucune connaissance de l'embarquement des matieres dangereuses ou de la planification des transports peuvent facilement utiliser les lignes directives discutees dans cet article

Wave equation analysis and dynamic monitoring of pile driving

Abstract: The wave equation analysis of driven piles is presented with a comparison of the Smith and Case damping approach and a discussion of cmventional soil input parameters. The cushion model is explained, and the difference in definition between the commercially available computer protrams is pointed out. Some views are given m the variability of the wave equatim analysis when used h practice, and it is recommended that results shouH always be presented in a range of values as corresponding to the relevant ranges of the input data. A brief background is given to the Case-Goble system of field measurements and analysis of pile driving. Limitations are given to the fieb evaluation of the mobilized capacity. The CAPWAP laboratory computer analysis of dynamic measurements is explahed, and the advantages of this method over conventional wave equation analysis are discussed. The influence of resiCual loads m the CAPWAPdetermined bearing capacity is indicated. This paper gives a background to the use in North America of the Wave Eguation Analysis and Dynamic Monitoring in modern engineering desigt and installatim of driven piles. The purpose of the paper is not to provlle a comprehensive state-of-the- art, but to present a review and discussion of aspects, which practisint civil engineers need to know in order to understand the possibilities, as well as the limitations, of the dynamic methods in pile foundation design and quality control and insPection. The Wave Equation Analvsis Longitudinal wave transmissions and solutions to wave equations have been lnown by mat6ematicians for almost a century. Fifty years ago, Isaacs (1931) pointed out that wave action occurred in a pile after impact and that wave mechanics could be used to analyse pile driving. A solution to the medimensional wave equatim, as applied to pile driving, was first published by Glanville et al. (1938). However, before the existence of computers, the solutions were not practical. About thirty years ago, E. A. L. Smith

Sensitivity analysis of ecological design parameters in streams. A

Abstract: Presentation des parametres de qualite des eaux de rivieres, parametres d'equations de sensibilite