Saudi Crown Prince Abdullah bin Abdul-Aziz inaugurated the new headquarters of Saudi Basic Industries Corporation (Sabic) in Riyadh last month.

The opening ceremony was part of the Saudi industrial giant's 25th anniversary celebrations.

Based in the Kortoba district of Riyadh and occupying a massive 284,500 sq site, the building is a major landmark on the highway leading from the King Khalid International Airport to Riyadh city. All Sabic executives and administrative staff will be located in this building.

The 16-storey twin towers represents the new face of Sabic - a combination of the modern and the traditional. The two towers merge into a single block at the 13th level and include a total built-up area of 53,251 sq m. The building can accommodate 2,000 corporate staff including senior management, business groups and support services.

The towers, which are clad with precast panels, have an arched facade symbolising a gateway suitably located at the entrance to the city.

The project also includes a 'low-rise' three-level building for marketing at the north of the main building and two wings on the south - one for the mosque and cafeteria and the other for the 1,000-seater auditorium and a training centre.

Facilities include multi-storey parking for 1,500 cars, basement parking for senior executives and a recreational compound including a gymnasium, swimming pool and squash and volleyball courts for employees.

A utility compound on the north-east corner contains the electromechanical plant, a warehouse, a sewage plant and pump houses.

The project forms part of a three-phase development envisaged by Sabic over the long term, a decision on which is yet to be made. Phasese two and three are expected to each include three-levels of office space and three levels of car-parking structure accommodating an additional staff of 500 each.

The high functional efficiency, environmental considerations and energy conservation is reflected in the building's overall design. The main entrance for VIPs and visitors is on the south side with three other entrances providing access for the staff.

The total gross building area (GBA) for the complete project is 172,901 sq m.

Elaborating on the construction of the project, a spokesman for Sabic says: ''An initial site investigation indicated that extensive grouting of solution cavities was necessary, and approximately 380 cu m of cementitious grout was used in ground improvement works. Foundation works on the tower and underground car-park involved a total of 53,00 cu m of earthworks. Much of the excavated material was screened and used for backfill.

''The two-legged tower is founded on a reinforced concrete raft 2.5 m thick. The volume of concrete in the raft is 11,000 cu m. The superstructure is a reinforced concrete frame incorporating elevator and service cores within each leg of the tower. The floors are of waffle slab and solid slab construction. The two legs of the tower are joined above level 13 with the construction of a temporary steel bridge, between 12th and 13th floor levels, which provided a surface on which the 2.5 m deep transfer girders could be cast. Precast concrete form slabs were used in the repetitive areas of solid slab construction. A permanent steel bridge, spanning 22 m, at 9th floor level serves as an additional connection between the two legs of the tower.

''The tower is connected, at basement level, to an underground VIP car-park which has a diameter of 50 m and has spaces for 47 cars.

''The highest occupied floor is 64.3 m above ground floor, and the highest concrete element terminates at 78.3 m above ground floor. The building footprint is 88 by 50 m. The concrete used throughout had a specified characteristic strength of 35 N/m sq m at 28 days, with microsilica added to all concrete below ground level. The volume of concrete in the structure is 37,100 cu m.

The auditiorium and exhibition centre is a two-storey reinforced concrete structure in the shape of a semi-circular arc. It is founded on pad footings and incorporates a partly vaulted roof in the exhibition area. The 25-m-span flat roof over the auditorium is constructed of steel beams with a profiled steel deck. The volume of concrete used in this structure was 8,650 cu m with a specified characteristic strength of 30 N/m sq m.

''The two-storey reinforced concrete structure which houses the mosque and cafeteria has a partial basement which houses the kitchen. The basement is founded on a raft while the remainder of the structure is founded on pad footings. The building incorporates two vaulted roofs, each spanning 11 m. The mosque has a reinforced concrete dome 18.8 m in diameter, with a 28.5-m-high minaret.

The volume of concrete used in this structure was 8,100 cu m, with a specified characteristic strength of 30 N/m sq m.

The five-level car-park is a reinforced concrete structure, shaped in the form of a semi-circular arc. The outermost facade is 336 m long and the innermost facade is 212 m long. The foundations are strip footings, and the structural frame and ramps are of reinforced concrete. The parking decks are constructed of 840 precast, prestressed concrete double-tee units, spanning 16.5 m, with in-situ structural topping. Five elevators service this structure.

''Extensive ground investigation was carried out under each of the ancillary buildings. All are founded on pad foundations and are singlestorey buildings. The roof of the swimming pool is an elongated dome. The roof of the gymnasium consists 23 m span steel trusses covered with insulated and waterproofed corrugated steel sheets. The specified concrete strength in the ancillary buildings was 30 N/m sq m at 28 days. The warehouse and chiller plant are housed in two steel-framed buildings which were fire-proofed using proprietary, sprayapplied, cementitious material.''