Underpasses in Hooipolder interchange are true masterpieces

On behalf of the ALSÉÉN construction consortium, Nepocon provided the engineering for the final and execution design of two new underpasses at the Hooipolder interchange: the Oosterhoutseweg and the Hooipolder underpass. The latter in particular is a first by Dutch standards. An interview with Jelle Mensink of Nepocon, project leader and chief structural engineer of this work.

Based on the VO and feasibility study conducted by construction consortium ALSÉÉN, Nepocon has further developed the two underpasses, Mensink says. "They pass under the Oosterhoutseweg and the A27, forming a new flyover connecting road at the Hooipolder interchange. Both underpasses were built on a pre-construction site next to the road and will be retracted during two road closures. We calculated the structures both geotechnically and structurally and developed the DO in 3D. Our DO models were then exported to the construction consortium's online BIM environment for extensive clash checking in the ACC. We then also created the UO, which included a 3D reinforcement model in addition to the traditional concrete drawings. Based on these models, the reinforcement supplier was able to generate the bending states. This 3D reinforcement model saved considerable time in the realization of both artworks and prevented detailing errors, so that the underpasses were ready to be inserted well within schedule."

100 hours of Hooipolder

The Hooipolder underpass was successfully pushed in by construction combination ALSÉÉN during the "100 Hours of Hooipolder" between Aug. 13 and 18. "A mega operation," according to Mensink. "Sliding in an underpass in an arch of this length (116 meters) was also a first for the Netherlands. The deck has several cantings to keep the design as slim as possible and to keep the weight to a minimum, so that the whole thing could still be retracted. The entire hulk weighed as much as 6,300 tons. The 50-meter-long Oosterhoutseweg underpass has yet to be retracted. The engineering of such daring feats is what we have become big at. We work very closely with the execution and have a wealth of practical knowledge. That makes it very pleasant to work with contractors. We know exactly what they mean."

Nepocon stands for smart, creative and practical designs. "We are a multidisciplinary agency with expertise in various fields of work. Our engineers create manufacturable and executable designs in civil engineering, hydraulic engineering, steel and mechanical engineering and geotechnical engineering, among others. With five offices, we are also nicely spread across the country." Nepocon is part of Engius, a collective of independent engineering firms. In addition to Nepocon, the labels Bureau Schmidt, Solid Services and Van Monsjou & Partners are part of Engius. "Regarding the current issue of Replacement and Renovation (V&R), as a collective we have complementary expertise in the areas of inspection, analysis, recalculations and engineering. By combining these strengths, we can provide clients with integrated, substantiated and practical advice that matches the complexity and urgency of the V&R task."