News Details
High-strength glass fibre reinforcement survives the impact of a 36-tonne truck
Schöck ComBAR: Ideal for use in PL-3 barrier walls
Crash test in North America: The test wall for the crash test was reinforced exclusively using Schöck ComBAR. No bending cracks or any other signs of bending failure could be found after a 36-ton truck had crashed into the barrier. (Photo: Schöck Bauteile GmbH)
A 36-tonne tractor van-trailer drives into a bridge barrier at 80 km/h – and causes only minor damage to the barrier wall. This is the result of a crash test recently carried out in North America. The glass fibre reinforcement “Schöck ComBAR” was installed and submitted to extensive testing. Working together with the Ministry of Transportation in the Canadian province of Ontario (MTO), a team of engineers led by Professor Kahled Sennah of Ryerson University (Toronto) developed and tested the test wall reinforced with ComBAR. A video of the impressive crash test can be viewed at www.schoeck-canada.com.
In North America, barrier walls are being reinforced more and more often with glass fibre reinforcement. Reason: corrosion problems that often occur when traditional steel-reinforced concrete is used are avoided when glass fibre reinforcement is installed, yet the overall strength of the wall remains the same. The building component manufacturer Schöck developed the glass fibre reinforcement “Schöck ComBAR” several years ago and has continuously developed it since. The bars are made up of numerous highly corrosion-resistant linearly aligned glass fibres impregnated by a vinyl ester resin matrix. The special manufacturing method used by Schöck ensures that all bar diameters have a high tensile strength of more than 1000 N/mm² in the direction of force. The modulus of elasticity is 60,000 N/mm². Glass fibre reinforcement has similar mechanical characteristics as steel-reinforced concrete, but is much lighter, more resistant to aggressive environments, non-magnetic and does not conduct thermal or electric currents. It is indeed a special reinforcement for special cases.
Further proof of the outstanding material properties of ComBAR was recently provided by a spectacular crash test in North America: a ComBAR-reinforced barrier wall withstood the impact of a 36-tonne truck. The truck crashed into the wall at an angle of 15 degrees and a speed of 80 km/h, and came to a standstill after about 50 metres. Following the crash, neither bending cracks nor any other signs of bending failure could be found on the wall. According to Canadian guidelines, the test wall conformed to category PL-3. This performance level describes the level of material strength required for road barriers on bridges. Level 3 is the highest risk category with regard to overall vehicle load and angle of impact.
Test set-up: Barrier wall
The barrier wall was developed by a team of experts working closely with the Ministry of Transportation in the Canadian province of Ontario (MTO). The test was performed at the Texas Transportation Institute (TTI), one of the most experienced institutions for crash tests on barriers, walls and highway accessories in North America. The TTI is part of the Texas A&M University System. In his capacity as independent consultant, Professor Khaled Sennah of Ryerson University (Toronto) was in charge of the comprehensive project. Sennah has carried out further static tests on the wall following the crash test, so that ultimately a calculation method will be available for barrier walls using the Schöck ComBAR glass fibre reinforcement. The aim is to develop a “finite element method” (FEM) of the wall and the crash, enabling further optimisation of the reinforcement design and the determination of static load equivalents.
Reinforcement layout and dimensioning
For the crash test with Schöck ComBAR, the reinforcement pattern was developed on the basis of a standard MTO reinforcement drawing for PL-3 walls with glass fibre reinforcement. In agreement with MTO, the Schöck experts made minor changes to the final reinforcement layout to optimise it. Dimensioning was checked again by the renowned engineering office McCormik Rankin (Ontario). In the design, the so-called “yield-line theory” used for the design of steel-reinforced concrete elements was transferred to ComBAR. This yield line theory was adopted for the dimensioning of highly ductile materials such as ComBAR. The crash test was carried out in line with the recently published American “Manual for Assessing Safety Hardware” (MASH). The barrier wall was almost 40 metres long and its design approximately corresponded to that of a real bridge deck.
Following the crash, neither bending cracks nor any other signs of bending failure could be found on the wall. The horizontal construction joint between the deck slab and the wall showed no signs of damage either. High-speed cameras recorded the crash test. The extensive film material was analysed by experts at the TTI, who then submitted a final report to Schöck and the MTO. The standard drawing of a PL-3 wall with glass fibre reinforcement is to be revised on the basis of the test results.
Specialists can obtain further information about “ComBAR” glass fibre reinforcement from Schöck Bauteile GmbH, Germany, and Schöck Canada Inc. – information can either be ordered by fax (+1 519 896 2190) or e-mail (christian.witt@schoeck.com).
