The lift tower was also designed to withstand seismic design, where statistical historical data of earthquake occurrences was used to model the magnitude of the movement. The seismic design involves the consideration of critical modes of movement and, in addition to the other loading cases, the resulting stresses and movement were used to calculate the concrete reinforcement and required sizing of the structural elements.
The tower structure consists of two C-shaped concrete cores, which house the lifts and are tied together by a central stairwell. The 55m free standing tower is supported only at the base, where the concrete bridge at the upper level rests on the bastion wall on sliding connections. This concept results from a design intent to have the tower completely independent of the bastion wall. The bridge sliding bearings are located below the two upstanding parapet walls, which are the principle structural elements that support the weight of the bridge, and have been detailed so as to accommodate the predicted movement of the tower.
The lifts are able to travel the total height in 25 seconds and house approximately 21 passengers each. As a precautionary measure, restrictions on the use of the lifts is enforced for a preset critical wind speed. This procedure is maintained in order to protect the exposed cables and cabin of the panoramic lifts from wind action and tower deflections. Instrumentation is located within the tower in order to relay measurements of the wind speed to control mechanisms which enable procedures for the automatic closure of the lifts. In addition, seismic instrumentation has also been installed to stop the lifts in the occurrence of any irregular movements resulting from earthquakes.
Execution of works commenced with construction of foundation base, continuing with concreting of walls and stairs, placement of bridge bearings and construction of bridge and finally with installation of perimeter metallic screen, lifts and building services. The construction works, metallic works and lift / building services were completed by contractors Polidano Brothers Ltd., JSD Ltd. and Mekanika Ltd. respectively. Due to the scale and height of the development, the completion of the project required extensive logistical planning including consideration of the tower and bridge scaffolding, craneage requirements and the temporary attachment of a transportation hoist. In addition, the various contractors faced the challenging task of working in parallel within the confined working space. The design, planning and site works execution were all completed by local consultants and contractors, providing a testimony to the capabilities of Malta’s workforce.