National Precast Concrete Association of Australia "Reid Up" on Engineering
On 26th May 2010, members of the National Precast Concrete Association of Australia (NPCAA) met for a technical discussion centred around the interpretation of and testing to AS3850-2003. The meeting, held at Reid's head office in Croydon in Melbourne’s outer east, also included physical "in-concrete" destructive testing in Reid's testing facilities.
The main theme of the meeting was to discuss AS3850-2003, and in particular, the ambiguities surrounding it's interpretation. A number of specific points were examined in the context of AS3850-2003, and it was demonstrated that a variety of interpretations are possible, leading to different Working Load Limits (WLL) being determined and claimed to be in accordance with the standard. This ambiguity, and the consequent different interpretations, has resulted in the publication of performance numbers which are not based on the same assumptions. This has proven to be a sure path to confusion and uncertainty in the precast industry, where the performance of similar items cannot be compared accurately in an impartial "like for like" manner.
Examples demonstrated included the determination of Working Load Limits and Limit State Factors relating to lifting and bracing inserts, the importance of applied loads, the use of dynamic and suction factors during lifting of precast panels, and the often ignored science of sling angles in lift design.
To demonstrate the inherent ambiguities within the standard, destructive physical tests of bracing and lifting anchors were conducted in the testing laboratory, the results measured, and the data analysed. After witnessing the physical testing, NPCAA members returned to the meeting room to dissect their findings. The analysis highlighted the discrepancy, where the same set of data can be used to derive differing hypotheses from different interpretations of AS3850-2003. this further confirmed the widespread view that AS3850-2003 needs to be reviewed, and that the NPCAA should take an active and leading role in the revision.
Members of the NPCAA who attended the meeting left with a greater appreciation of AS3850-2003, the issues the industry faces in the revision of the standard, and the importance of a consistent, controlled, and well defined methodology in the testing and analysis of engineering test data to confirm theory.