Renovation, reinforcement and expansion of the A9 Schiphol Bridge
Work on the Schiphol Bridge on the A9 motorway is in full swing. The project is being carried out on behalf of the Directorate-General for Public Works and Water Management (Rijkswaterstaat) and is aptly referred to as a technical masterpiece. It represents a huge infrastructure project. When completed, it will be the widest bascule bridge in the Netherlands. But what changes will be made to the bridge?
The Schiphol Bridge is an essential structure on the A9 motorway, facilitating the intersection between the A9, the Nieuwemeerdijk N231, the Ringvaart (Ring Canal) and the Schipholdijk. It consists of two bridges (northbound and southbound) with two movable steel decks with electromechanical operating mechanisms. The renovation and expansion work includes widening the concrete decks and substructure, renovating the bascule chamber, and constructing a new control building. This bridge structure requires careful design, planning, construction methods, and phasing to achieve a safe, efficient, and sustainable bridge that meets growing traffic demands with a remaining service life of 30 years.
The Schiphol Bridge consists of two sections, one for each direction of traffic. Each bridge is divided into a western approach ramp of approximately 85 metres, an eastern approach ramp of roughly 165 metres, and a movable section spanning approximately 20 metres.
For the new situation, the two existing steel decks and the drive mechanism will be replaced entirely and widened on both sides. The movable part of the bridge consists of an orthotropic deck slab supported by cross girders and main girders. The steel decks of both bridges (northbound deck and southbound deck) are virtually identical in design and detailing, except for the width due to the number of lanes they have to accommodate. The northbound deck is considerably wider than the southbound movable deck.
The counterweight of the northbound bridge is filled with approximately 442 tonnes of solid ballast. The design of the counterweight for the southbound bridge differs slightly from that of the northbound bridge. The counterweight of the southbound bridge, which has a narrower width, is filled with approximately 362 tonnes of solid ballast.
The mechanical equipment of the Schiphol Bridge is vital for its reliability and functional availability. It comprises several components and systems that function together to ensure the bridge’s operational movement, safety and maintainability.
One of the most important aspects of the mechanical equipment is the operating mechanism of the bridge. This electromechanical mechanism allows the bridges to open and close independently for the passage of vessels. It consists of a robust hydraulic system with electric motors and gear mechanisms (Panama wheel-pinion drive with crank mechanism) that ensure powerful and precise operation of the movable bridge sections.
In addition, the mechanical equipment includes a crank mechanism that provides a locking force (the ‘locking and securing of the bridge’) to ensure a guaranteed closed position. This contributes to the bridge’s safety and minimises the risk of malfunction.
Sensors and measuring systems are also integrated into the mechanical equipment. These sensors monitor, among other things, the position, speed and forces exerted on the bridge. They provide valuable information to the control and monitoring system, enabling it to position the bridge accurately and check for deviations during the opening and closing cycles. Based on this data, timely maintenance can be conducted to ensure optimum bridge functioning.
In addition to the above systems, there are other mechanical components such as bearings, seals and emergency drive mechanisms, and both decks are equipped with a manual drive mechanism. These components all play a crucial role in the smooth operation of the bridge and must be regularly inspected and maintained to ensure optimum performance. To allow maintenance to be conducted with the bridge in the open position, a locking mechanism is provided in the bascule chamber to enable maintenance or replacement of drive components.
An essential aspect of the renovation and expansion of the Schiphol Bridge is the widening of the existing, in-situ post-tensioned, concrete deck. To accommodate the increased capacity requirements (road widening), the existing concrete decks will be widened, and a coupling will be provided between the existing and new decks.
The concrete decks will be widened by adding new in-situ cast post-tensioned decks on either side of the existing decks. The widening of the decks will be carried out on auxiliary bridges on either side, on which the formwork structures will be built over the Haarlemmer Ringvaart (Ring Canal). These new decks, with an advanced coupling to the existing structure, form a seamless transition between the old and new parts of the bridge.
The coupling between the existing and new decks is an important aspect of the concrete deck widening. It will be achieved by creating an integrated system of reinforcement drilled into the existing concrete decks and and hydrojetting the exposed existing reinforcement to incorporate additional reinforcement. This form of coupling ensures that the forces exerted on the bridge are evenly distributed over the entire bridge deck, thus providing strength, stability, and increased safety. It also creates a functional, wider deck surface to facilitate expansion.
The bascule chamber is an essential part of the Schiphol Bridge. It plays a crucial role in the opening and closing of the bridge’s movable components. The chamber houses the mechanical equipment and provides the necessary strength, stability, and force distribution during the movement process of the drive mechanism, which exerts significant force on the concrete structures and foundations.
The existing bascule chamber will be renovated and adapted to meet the requirements of the new bridge configuration. Various adaptations will be undertaken, such as replacing the expansion joints, renewing the roof of the bascule chamber and strengthening the walls and floor. The front wall, up to a height of approximately 0.5 m NAP (Normaal Amsterdams Peil), will also be completely demolished and rebuilt. This renovation work will ensure that the bascule chamber can withstand the increased loads and forces and continues to meet the structural safety standards, with the intended remaining service life of 30 years.
In addition, the bascule chamber will be extended on the north and south sides to accommodate the new configuration of the bridge (road widening). The dimensions of the new part of the bascule chamber are significantly larger than those of the existing part.
The existing control tower will be completely demolished, and a new control building will be built on the north side of the Schiphol Bridge. The new control building will be constructed as a ‘box-in-box’ structure. The control building has been designed to provide a safe and comfortable working environment for the personnel responsible for operating the bridge. Although hidden from the direct view of road traffic, the control building has been architecturally designed and integrated with functionality and aesthetics in mind.
The control building has rounded corners and various design features to visually differentiate it from the bridge deck. As a result, the building will be a recognisable element of the location and contribute to the overall appearance of the bridge.
Wouter, managing director Infra and also COO of Iv, would be delighted to discuss this with you! Get in touch via +31 88 943 3200 or send a message.
