e-mosty March 2019 Long Span and Multiple Span Bridges - Page 36

Specific Details Overall length of all bridges Maximum height of the main pylons Deck width of the Suspension Bridge Deck thickness of the Suspension Bridge Pile diameter of the foundation of the Suspension Bridge Pile number of each pylon of the foundations Pile lengths of the foundations of the Suspension Bridge Anchorage, South: diameter depth of the anchorage Anchorage, North: diameter depth of the anchorage L = 3,003m H = 143.14m B = 25.60m d = 3.00m Φ = 2.20m 24 pieces max. L = 110.00m d = 50.00m h = 36.00m d = 50.00m h = 11.35m THE DECK The proportions of the deck of the Suspension Bridge are shown in the following “Drawings Section” illustrating the symmetrical geometry. Another major challenge was to design the bridge for wind loads which can achieve values up to 250km/h = 69.44m/s. The deck has a slender depth and contrasts well with the stockier towers. In the past many cyclones have hit the coast of Maputo Bay and other areas of Mozambique. Despite the aesthetic slenderness, this deck is designed to resist fluttering phenomenon caused by wind in an area where cyclone occurs. For this reason, data was collected and scrutinized very carefully with all the measured wind speeds since 1973. PYLONS The data were provided by “Instituto Nacional de Metereologia de Mocambique”. The main Pylons are concrete and each consists of two hollow legs 7m x 5m in section, with horizontal bracing beams at 1/3 and 2/3 height and near the top. WIND AND EARTHQUAKE LOADS FOR THE DESIGN OF THE SUSPENSION BRIDGE The Bridge in Maputo is positioned at the end of an axis which is starting in Djibouti and ending in Mozambique, on the east of an active tectonic plate. The axis is follows the path Djibouti-Ethiopia- Uganda-Rwanda-Burundi-Borderline Tanzania / Congo-Malawi-Mozambique. Along this axis the tectonic plates move and the consequence is the risk of severe earthquakes. By statistical analysis of all these collected wind speeds, using the Gumbel Method the derived value of the basic wind speed was: v = 35.77m/s, for 100yr return period, at a height of 10m above sea level (as recommended in the wind tunnel test Report as well). The loading experienced by the deck was estimated in the wind tunnel report. As the height of the Suspension Bridge above the sea level is approximately 64m, the design wind speed was evaluated to: v = 49 m/s. The wind tunnel test for the chosen deck of the Suspension Bridge resulted in a flutter wind speed: 1/2019 v = 73 m/s.