IMPROVING THE IMPACT RESISTANCE OF GRC PLANKS USING GRP BARS

摘要

Glass-fibre reinforced concrete (GRC) planks are commonly used as an integral part of the walkways in floating marina systems and are so chosen because of their lightness relative to their strength and flexibility, their durability and their non-slip surface. Planks can be single or multi-span and are thin (circa 3cm) to minimise their weight. However, use in practice has very occasionally given rise to flexural failures of the planks due to impact loading, usually by dropping of gas cylinders or a heavy person jumping off a moored boat, or by accidental impact of a berthing boat into a service bollard. Failures tend to be catastrophic and leave the pontoon in an unserviceable condition, such that immediate replacement is necessary to ensure continuation of a safe walkway for sailors. To mitigate against such failures, the incorporation of glass-fibre reinforced plastic (GRP) re-bar was investigated, GRP being non-corrosive and of relatively high tensile strength capacity. Two 6mm parallel bars were introduced close to the soffit of the planks over their entire length. This research project characterised the flexural response and failure modes of the GRP re-bar planks under static and impact loads. Considerably enhanced load carrying capacity and ductility were observed under static loading. More importantly,the response of the strengthened planks to simulated human impact over a series of jump heights provided evidence that considerable additional toughness was introduced by the GRP bars, enabling much better energy absorption. Although some cracking still occurred on impact, the planks remained serviceable and safe,ensuring that they could be replaced in due course without undue disruption to normal pedestrian traffic.