City planning using the SEAMAN simulation tool

Designing a new bridge over a river passed by inland vessel traffic will always be a challenge, both for the visual look as well as for the safety of vessels passing under and traffic on the bridge. SSPA is contributing to the design process of the new bridge, Hisingsbron, being built in the city of Gothenburg. It is doing this using the SEAMAN simulator. Clients such as the Gothenburg city architect, the design team from COWI and stakeholders from the shipping industry have been able to evaluate the bridge to be built.

A situation

The pilot leans back in his chair. He has safely navigated the ship from Lilla Edet, has just passed the Marieholmsbron bridge and there are only two bridges left to pass until this journey will end for him. He can see the newly built bridge “Hisingsbron” slowly opening its leaves in front of him as he is approaching it. Suddenly the bridge leaves stop dead with the bridge only half open. After a short moment the bridge-watch announces over the radio that there is a malfunction in the bridge’s machinery, and it will stay in its current state until further notice. The pilot realises immediately that he will not be able to pass under the bridge in its present state, and as the ship is travelling with the current it will be too much of an effort to simply stand-by in front of the bridge. He will have to rest the ship against the fenders on the bridge guard designed for precisely this type of event. But is such a manoeuvre possible, and is it safe? Can the pilot trust that the design of the bridge guards is sound?

Fortunately the situation above is taking place on a SEAMAN simulator at SSPA. Hisingsbron is not yet built, and before COWI decides on the design of the bridge guards they will take every measure to ensure that the guards can pass scenarios like the one described above. One measure that has been taken is to set up a SEAMAN simulation to test the design’s safety.

The bridge

The new river connection will form a connecting link between the north and south bank of the river and contribute to the transformation of the Freeport and Gullbergsvass areas. The connection is not only a transportation link, but also a major urban development project and an attractive symbol for the City’s future. Hisingsbron is to replace the existing Götaälvbro and to go into operation around 2020. The project’s total construction period is planned to be approximately five years. A program outline was drafted and consultations were held in autumn 2009. The height of the new bridge will be 13 meters and it will be located just upstream of the existing Götaälvbron. To start with, at least 80,000 public transport users, 5,000 cyclists and pedestrians, and 30,000 drivers will be using the bridge on a daily basis.

The challenge

SSPA continually works as a partner with large design and construction companies, as well as municipalities in city planning. SSPA’s contribution in the close cooperation with clients is usually to provide logistic best practice, design collision avoidance measurements, ice management, evaluate maritime risks and simulate vital hazardous situations during construction and operation. In this specific project SSPA worked closely with COWI and the Municipality of Gothenburg to evaluate maritime risks and the nautical effects of the new bridge’s design.

The main parts of the mission were:

  • To verify safe ship passage of the new bridge
  • During construction work:
    • To verify safe passage of the construction site and old bridge.
    • To eliminate or reduce risks introduced to shipping during all stages of construction, which was done by simulating identified critical steps in construction.
  • To form a documentation to enhance existing risk analysis focusing on injuries onboard passing vessels.

All has been done to maintain safe and effective vessel traffic during the construction and during operation.

The simulations

SEAMAN is a simulation framework designed in-house at SSPA. It draws upon SSPA’s 70 years of experience of hydrodynamics and ship manoeuvring. Through SEAMAN and SSPA’s manoeuvring experts that knowledge is brought to clients in a way that answers the questions that each specific client may have. Since each client is unique, and each question is unique, SEAMAN is designed from the start to be flexible. In this particular case the visual cues gained from the bridge opening and closing was important for the client. SSPA modelled the bridge so that the opening times were close to those in reality, which enabled the previously described simulation to be carried out realistically.

The results

What happened with the pilot and the malfunctioning bridge in the situation? The pilot successfully manoeuvered the ship to the bridge guard, from which he could proceed once the bridge was functioning again. The bridge design proved sound, at least for this scenario. During the two days when the simulations were conducted, 64 other scenarios were simulated, discussed by the pilots and SSPA’s maneuvering experts, and then graded for safety. This will help ensure that there will be fewer surprises once the bridge is actually built. Considering that the bridge is expected to last for 120 years, those days in the SEAMAN simulator can be considered time well spent.

Photos and illustrations

Is the manoeuvre possible and is it safe? Different situation alternatives were created on the SEAMAN simulator at SSPA.

Screenshot from the simulation. Before the final design of the Hisingsbron will be decided, every measure will be taken to ensure that the guards can pass scenarios like the one described.

Götaälvbron in the City of Gothenburg as it is today. Hisingsbron will replace the existing bridge around 2020. Photo: Jim Sandkvist

65 scenarios were simulated, discussed by the pilots and SSPA’s manoeuvering experts, and then graded for safety. This will help ensure that there will be fewer surprises once the bridge is actually built.