A rig for static-load testing highway parapet posts to failure was designed and built at Abington for an Industrial Member.
The object of the testing was to establish a post's load capacity. The test was not designed to act as a crash load simulator, but as a quality control test for production posts required by BS 6779, the standard for highway vehicle containment parapets.
The Member wanted to be satisfied about the quality of its components, in particular the welding which goes into them before they are put into service. Because of their enclosed nature the posts are difficult to inspect by NDT, so random testing to destruction was adopted.
The test in BS 6779 is based on the results of a quality survey carried out by TWI in 1984 for the Transport and Roads Research Laboratory. The rig can accommodate a range of parapet post designs with any base fixing and can test to loads over 200kN at a lever arm of up to one metre. The aluminium posts are rectangular and hollow in horizontal section, and tapered vertically from 215x75mm at the base to 93x75mm at the top. They are designed to carry at least 50kNat a 600mm lever arm.
In service the posts support three aluminium parapet rails and are spaced at approximately three-metre centres. The rails themselves are intended to act as an energy absorbing containment barrier. To satisfy the British Standard dynamic test performance criteria the parapet must be able to withstand the impact of a 1.5t vehicle travelling at 70mph at an angle of 20 degrees to the fence.
The testing rig is an L shaped strongback on to which the posts under test can be bolted and loaded using a hydraulic ram. At one end of the ram, a spherical joint transmits load to the post. At the other, a load cell monitors the load the post is sustaining. Deflections of the post while under load are measured by a displacement transducer.