Durable new wooden cable-stayed bridges over the Hambeek River in Roermond

The existing 'Hambeek bridges', namely the Roode bridge and Bridge 't Ham over the Hambeek in Roermond, were found to be in need of replacement after inspection. The municipality of Roermond invited Flora Nova Houtconstructies, among others, to tender for the project 'Replacement of two wooden bridges over the Hambeek'. Flora Nova accepted the project and Boogaerdt Hout, one of the oldest timber merchants in the Netherlands, supplied all the wood.

To prepare and set out the tender by means of an EMVI contract with accompanying demand specification, the municipality of Roermond engaged engineering firm Westenberg. "The request turned out to fit very well within our business activities," begins Lennert Joore, Manager of Construction Works at Flora Nova. "After all, we are very strong in realizing civil engineering structures." 

From design to realization

Flora Nova houtconstructies b.v., a nationally operating company, specializes in the design and construction of bridges, marinas, jetties and decking, among other things. "Thanks to our broad knowledge and experience in wood, combined with steel, concrete and plastic, we are in an excellent position to completely relieve our clients of their worries. The reason that many municipalities, water boards, provinces and contractors know how to find Flora Nova for a variety of assignments."

Bridges over the Hambeek River

So too for the bridges over the Hambeek River. "As the contractor for this project, we were responsible for the total work: preparing and executing from A to Z in a construction team context all the necessary work. That included removing the two old bridges and designing, drawing, calculating, realizing and delivering the two new bridges. The tasks also included applying for the necessary permits and additional work such as taking traffic measures and communicating with stakeholders."

Plan of action

"As with every project, we drew up a thorough plan of action, in which we described how we would do the preparation and execution and how we could relieve the client as much as possible in this. We achieved the maximum score and the project was subsequently awarded to us. After a pleasant kick-off, we started the design phase. During this phase, we looked closely at the shortcomings of the old bridges and came up with solutions for them in the new design. A number of starting points were fixed. The most important one? The new bridges had to have the same appearance and consist of the same material as the old bridges."

Improvement through change

"We always respect the required project specifications, unless it turns out during the design phase that calculations show that it is not technically possible, as in this project." Joore explains that the old bridges were built in 1985 and the structural calculations at that time had to meet lower standards and safety factors. "For the new bridges, that would mean that-if we were to build them in wood as requested-the girder structures would become so large that the clearance height would no longer be adequate and the deadweight would be too great. So then you have to make a change anyway, to ensure that the design meets current standards as well as being structurally feasible." The engineers at Flora Nova engineered new bridges with steel girders, but modified the design so that the new bridges appear to be made entirely of wood. "This way the new bridges have the same wooden appearance, but meet current standards and requirements," says Joore. 

Wood supplier

To realize both bridges in wood, it was important to work with a wood supplier who knew what he was talking about as well as ensuring that the necessary wood could be obtained in a timely manner. "In Boogaerdt Hout we found the perfect partner," says Joore. Founded in 1741, Boogaerdt Hout is one of the oldest timber traders in the Netherlands. With their own import channels, round timber sawmill, mechanical woodworking and years of accumulated knowledge, they can supply any sector with the right sustainable type of wood.      

Wood in wet construction

Lars Bastiaansen, sales manager at Boogaerdt Hout and specialized in the application and processing of wood in wet construction, talks about their contribution to this project. "Because of the strength and durability of the material, wood is very applicable in civil engineering and especially in hydraulic engineering. Just look at lock gates, fenders, bridges, jetties and railings." Bastiaansen notes an increase in the use of hardwood. "This undoubtedly has to do with increasing sustainability requirements in terms of materials. Because wood is CO₂ retained throughout its lifetime, it plays an important role in making the Dutch infrastructure more sustainable. We exclusively import our wood through sustainable productions mainly from West Africa."

Sustainable bridges

"We were involved early in the process and worked closely with Flora Nova. Especially the quantity and size of the pylons created a challenge. Using such long heavy piles is quite unique. For this you need logs that are nice and straight and long. We immediately consulted with the FSC sawmill in West Africa and they selected logs in the forest especially for this project that met the aforementioned qualities. It was then a matter of getting these to the Netherlands in time and processing them further so that the schedule could be met." Joore: "There was a perfect interaction between Boogaerdt Hout and Flora Nova: they sawed and planed everything properly and we then cut and assembled it." Bastiaansen adds: "By keeping the dimensions as optimal as possible in the preliminary stages and including the sustainability idea in the engineering, the minimum amount of waste was generated. With a total volume of 57 m³ to FSC Azobé in these bridges is a whopping 93,154 Kg of CO₂ recorded."

Prefabrication

Both bridges were fabricated in segments at Flora Nova's machine shop in Ophemert. "One of the reasons that the municipality chose us is because we provide maximum effort in the preparation," says Joore. Among other things, Joore refers to carefully measuring the existing situation, drawing the new bridges into the measured situation and performing various necessary checks during fabrication. "Every detail and screw of the bridge, was carefully worked out in the drawing work. The municipality was also very appreciative of our execution method. For example, we recreated the supports on our own site from the actual situation and already built both bridges completely once, including the prefabricated railing." According to Joore, these are all factors that contributed to the fact that on-site execution could be realized in a very short time. But not before the bridge arrived at its location....

Transportation by water

Due to the dimensions of the bridges (47 and 53 meters long), the segments were loaded onto a work vessel overnight and transported by water to Roermond. There, further assembly and finishing of the prefabricated construction kit took place. "This method of transport not only ensured few transport movements by road, but also less inconvenience to local residents," said Dr. K. K., who is a member of the project team. The bridge sections were mounted on the old foundations and further finished.

Joore and Bastiaansen are proud of the final result: "With the new bridges over the Hambeek, we have realized in a sustainable way in a Natura2000 area two beautiful eye-catchers that will be frequently used by pedestrians and cyclists."