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corr control steel_bearing_piles 8pgs

corr control steel_bearing_piles 8pgs - Corus Construction...

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A corrosion protection guide For steel bearing piles in temperate climates Corus Construction & Industrial
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2 A corrosion protection guide For steel bearing piles in temperate climates This document is intended to provide guidance on the corrosion and protection of H-section universal bearing piles used for the foundations to all types of structures. In the majority of circumstances steel bearing piles can be used in an unprotected condition, however, in more aggressive environments, additional protection may be required to achieve the desired design life of the structure. This publication outlines the corrosion performance of steel piling in various environments, and reviews the protective measures that can be taken to increase the life of steel piles where necessary. Corrosion of piling in various environments In determining the effective life of unprotected piles, the selection of piling section and the need for protection, it is necessary to consider the corrosion performance of bare steels in the different environments normally encountered in service. The corrosion rates given in this section are per exposed face. To determine the reduction in section thickness, the cumulative losses from all relevant faces need to be considered. The corrosion rates quoted are based on those given in BS 8002 (1) , BS 8004 (2) , BS 6349 (3) or are derived from the corrosion allowances given in EN 1993 – 5 (Eurocode 3: Part 5) (4) . Mean or guidance values are given by the references and are considered to be most relevant to the design and performance of most steel foundations. However, in some circumstances the designer may wish to take account of higher values and in these circumstances upper limits are given for marine environments in BS 6349. Underground corrosion of steel piles Natural soils The underground corrosion of steel piles has been studied extensively. A review (5) of published data, outlining mainly overseas experiences, concluded that, unless the soils are strongly acidic (pH<4), the underground corrosion of steel piles driven into undisturbed soils is negligible, irrespective of the soil type and characteristics. The insignificant corrosion attack was attributed to the very low oxygen levels present in undisturbed soils. Research on instrumented driven steel piles (6) shows that the greatest proportion of load resistance is derived from the lowest 25% of pile length in the zone immediately above the pile tip, where the risk of corrosion is normally lowest. This also has relevance to piles driven into fill soils. Pitting corrosion in the water table zone is frequently reported in the literature, but nowhere is this regarded as affecting the structural integrity of piling, except for excessive pitting found in some Norwegian marine sediments (7) . Evaluations by British Steel (8-12) of piles extracted from UK sites, ranging from canal and river embankments to harbours and beaches, also confirm negligible underground corrosion losses. A further evaluation in Japan (13) of test piles
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