Developed as part of a small team while working at Dissing+Weitling Architecture in Copenhagen, Denmark.
Although now separated by the Gulf of Aden, the southern part of the Arabic Peninsula and the Horn of Africa were closely connected in ancient times. Even now, the highlands of the Yemeni and Ethiopian regions have much in common both physically and environmentally. Throughout history there has always been a considerable cross-continental trade across the Red Sea and the Gulf of Aden and this has remained true to the present day. The movement of merchants dating back to ancient times has led to a significant blending of populations and traditions.
The new link will foster and strengthen the existing cultural and economic connections between the regions, and serve a population of in excess of 100 million people. The bridge will be located in the Strait of Bab el-Mandab, a narrow point between the Horn of Africa and Yemen, the water passage between the Red Sea and the Gulf of Aden. Every year tonnes of material from the Persian Gulf is shipped to and from the west through the Strait of Bab el-Mandab, the Red Sea and the Suez Canal. The route is the main waterway between Europe and Asia.
The bridge will link the coast of Djibouti to the Governorate of Ta´izz in Yemen, passing the nearby island of Perim and spanning over 29 km of water. New cities will be built at either end of the bridge, with Medinet an Noor, the “City of Light” on the Djibouti side. The cities will provide activities and buildings for thousands of inhabitants.
The constructive principle of the Djibouti-Yemen bridge is straightforward: to cross over considerable depths of water (around 300 m) it is necessary to opt for very long spans in order to avoid numerous, costly, and complicated foundations. Consequently the proposed engineering solution is to design a suspension bridge with 4 main spans of approximately 2.7 km each.
The structural principle then becomes easy to comprehend as the forces and tensions are clearly perceived in the design. With its gigantic dimensions the bridge will be one of the most visible and impressive structures ever made by man.
The relation between the width of the deck and the length of crossing is extremely close to what is technically feasible. This provides special opportunities for the design of the bridge pylons: there will be five colossal concrete pylons with a soaring height of about 400 m.
The four legs and the four layers of horizontal cross beams will form an austere wedge-shaped volume which is both dramatic and visually elegant and light: a ladder to the sky capable of holding two cables 1.2 meters in diameter which will support the whole bridge. Each pylon leg has a simple rhombus cross-section, slightly tapered from the bottom up. The tops of the pylons have glass caps to protect the cable saddles and provide opportunities for illumination. Each side of the pylon volume has a kink in the middle, visible on the horizontal cross beams in order to give the whole pylon a lighter appearance.
The anchor blocks at the end of the suspension spans strike a delicate balance between a thick concrete element, strong enough to support the heavy load and a design proportioned to be as slender as possible. The blocks work as a transition element between the approach spans and the suspension spans.
The approach spans will be very long, up to 1 km, due to the water depths. They will be a very light structure of steel tubes connected in triangular shapes in order to form a fine double triangular truss.
The truss will be sustained by simple and numerous concrete piers every 150 meters.
The main deck is divided into three parallel elements, the two outermost for the road traffic and a single one in the middle for the railway. The deck is supported by cross beams every 30 meters, constituting the backbone of the bridge.