Vehicle impact tests have been made on three types of steel bridge parapet as part of the laboratory's research into the performance of various designs of parapet to ministry of transport technical memorandum no be5. The programme was carried out in collaboration with the British Steel Corporation. The minimum design requirements of the memorandum are intended to provide parapets capable of containing cars weighing 1.5 mg impacting at an angle of 20 degrees. For p1 parapets, specified for motorways, the design speed is 113km/h, while p2 parapets, specified for all-purpose roads, have a design speed of 80 km/h. The three types of parapet tested were a p1 parapet and two arrangements of p2 parapets. The p1 parapet which consisted of three rails mounted on posts spaced at 3.6 m centres satisfactorily contained and redirected a car colliding at 111 km/h. A similar three rail p2 parapet with wire mesh satisfactorily contained and redirected a car colliding at 83 km/h, the car steering back to the line of the parapet after impact. The vertical infill p2 parapet with two rails contained a car striking it at 73 km/h but the car overturned after impact. (the memorandum has lately been amended to restrict the use of this type of parapet to roads where the speed does not exceed 65 km/h.) In a test outside the requirements of memorandum be5 the p1 parapet contained a coach weighing 4.9 mg striking at 93 km/h and 17 degrees, but the posts yielded sufficiently for the vehicle to overturn on being redirected. (Author/publisher)
Samenvatting