Year: 1998

Location: Lisbon, Portugal

Country: Portugal

Owner Builder: Diverse Ownership

Contractor: Construtora do Tamega / H. Hagen / Obrecol / OPCA / H. Hagen

Designer: Álvaro Joaquim De Melo Siza Vieira

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Problem / Solution

The 1998 Lisbon World Exposition was an official specialised World’s Fair held in Lisbon focusing on the oceans and their future importance, as well as, a commemoration of 500 years of Portuguese discoveries. Several exceptional structures were made for the event, one of the most spectacular being the Portuguese National Pavilion. This structure included a sagged parabolic membrane slab roof cast by means of Light Weight Aggregate Concrete. The dimensions of the canopy are 65m x 50m, and the slab thickness is 20cm.

Experience

The sagged roof induced some large horizontal forces at top of the shear wall with stiffeners. Due to the use of LWAC, these forces are minimised. The shear walls insure the force transfer for the horizontal loads from dead-weight, wind and earthquake between the roof and the underground pile foundations. The roof itself is a 20cm thick parabolic membrane LWAC slab. The membrane tension due to sag is compensated by using long posttension cables anchored in support slabs on top of the shear walls.

Why expanded clay?

The Portuguese National Pavilion consists of the main 3 storey multipurpose building and the slab canopy. The pavilion provided conditions for the reception of delegations present at Expo’98. The canopy structure is a 20-centimetre-thick parabolic membrane concrete slab hanging from prestressed tendons anchored along the two short sides into slabs placed on top of a reinforced concrete structure of shear walls and stiffeners. LWAC was chosen as material due to low dead weight, so that the horizontal forces in roof and supports could be reduced to a minimum at the same time as appropriate strength and stiffness was maintained. The total weight of the roof was reduced by approximately 430 tons using LWAC. It is the first time that a structure of this type is casted with LWAC in Portugal.