Many engineers, including LTA and various consultants, have asked the question of whether used strutting material diminishes in strength with age in the past. Yongnam, being a major player in the local strutting industry, have proactively carried out a full-scale test to address this fundamental safety concern.
Yongnam carried out a full-scale load test on its proprietary modular strutting system at its fabrication plant in Tuas on the 8th November 2006. A full-size test of this scale and magnitude is believed to be the first ever to be done in Singapore. A full-sized 20m long double-laced strut system was tested in collaboration with the National University of Singapore to its ultimate failure load, with full monitoring of stresses and deflections with strain gauges and transducers.
Prominent guests from the construction industry were invited to witness this event. More than 300 invited guests from major contracting firms; LTA, MRT, BCA, academic institutions, universities and engineering consultants attended the event.
The main test objectives are to determine the safe capacity of a used Yongnam’s Strut System and compare with actual design loads. The significance of this test is of paramount importance to the local construction industry, as the Yongnam Strut System is widely used on LTA, MRT, building, basements and general civil engineering applications.
Amongst the various technical and scientific documentations recorded from the test, the following summarizes the overall test results. At a failure load 1438 tons which is about 2.0 times the safe working capacity of the strut system, the test confirms the following main points:
(1) The predicted failure load of the strut based on BS5950:Part1:2000 is 995 tons. Based on the design safety factor of 1.4, the working load is 710 tons. The actual collapse load of the test specimen is 1438 tons. The actual factor of safety against the design working load is about 2.0. The load capacity predicted by the codes is found to be on the conservative side.
(2) Forces induced in lacings are less than 1% of the axial load, as compared with current codes of practices recommendations of 2.5%.
(3) The current size of lacings is not critical and it does not govern the strut ultimate capacity; hence there is no need to increase lacing size for all future projects. This relates directly to an economical and cost-effective strut system.
(4) An old and reused strut does not diminish in strength over the years. This relates to the significant point that struts can be repeatedly reused over the years, hence leading to economical operational advantages.
(5) The strut connection joints are not the critical failure point; since the failure is the mid span buckling of the top flange. This relates to economical design of strut joints.
This report ultimately proved to be of tremendous benefit to our overall strutting business objectives in many aspects. Developers, main-contractors, engineering consultants and authorities will find that the test result gives a level of safety and product confidence that is unparalleled in both Singapore and globally, as Yongnam continues to spread the use of its strutting system globally to other countries such as Hong Kong, Thailand, India and the Middle-East.
Full-Scale Load Testing of Steel Strutting System for Yongnam Holdings Limited