1,200 tons moved with precision
Heavy duty castors from Blickle castors help Strabag lower a bridge reliably.
Vienna-based Strabag SE is one of the largest construction companies in Europe. Its core markets are Germany, Austria and countries in Eastern and Southeast Europe. It has more than 75,000 employees and generates an annual turnover of approximately 16 billion euros. The company’s core business areas are commercial, industrial and bridge construction, infrastructure projects, building sports facilities and sewage systems.
Strabag needed to lower a 53-metre long bridge section weighing more than 1,200 tons in successive stages over the course of several days as part of an eight-lane expansion of the A7 motorway near Hamburg. This had to be done while keeping the position of the concrete structure stable, with zero margin for error. Strabag had previously used high performance PTFE slide plates for similar projects. However, the gap between the panels and the steel beams introduced the risk of the bridge swinging around. The procedure also had to be halted when the plates kept getting stuck due to the sides being lowered at slightly different speeds.
Strabag’s experts came up with an alternative - using castors to guide the bridge downwards along steel beams. The company contacted Wache, the dealer who has represented Blickle in the Hamburg and Schleswig-Holstein region for 35 years. Strabag’s requirements were clearly defined: a low mounting height and a tread width of less than 200 mm. Each castor needed to have a load capacity of six tons. Spring travel of between 10 and 20 mm was specified in order to balance out tolerances. Blickle’s development department came up with a tailored solution which met all of Strabag’s requirements. The nearly indestructible80 Shore D castor is made from high-quality compressed cast nylon. It also offers a particularly low level of rolling resistance and is abrasion-resistant. Blickle used four polyurethane springs to compensate for the tolerances. Hydraulic jacks were used to gradually lower the motorway section between four vertical steel beams. Steel brackets were placed on the underside of the bridge to transfer some of the weight of the bridge onto the vertical steel beams. Blickle incorporated 16 specialised castors into these brackets - eight in the direction of travel and eight in the transverse direction. The castors kept the bridge section perfectly aligned with the steel beams.
Blickle helped Strabag to significantly improve the complex lowering process, which previously involved PTFE plates. Bridge sections getting stuck is no longer an issue thanks to Blickle’s specialised castors. “The castors and suspension system make the lowering process much more reliable. We were able to overcome any imperfections in the surface structure of the beams without any issues,” said the project lead at Strabag. Blickle’s solution also provides an impressive level of flexibility. Strabag can use specialised adjustment nuts on the PU springs to make minute adjustments quickly and easily.