Gulf Construction Online - Strictly Business

Al Wasl Office Complex

Strictly Business

GCM presents a special report on the new Al Wasl complex in Dubai that is all set to open.

01 MARCH 2001

The Al Wasl office complex has been completed recently on Al Qataiyat Road in Oud Metha in Dubai, UAE.

The prestigious project consists of a six-storey office block and a 16-storey office tower, both of which have one basement level. The complex has external landscaping and an open car-park.

The complex, which has a total built-up area of 56,000 sq m, occupies a 15,863 sq m site near the headquarters of Dubai Electricity and Water Authority (Dewa) and the Grand Hyatt Hotel development which is currently under construction. It provides a total of 418 car parking spaces, of which 319 spaces are inside the building and underground.

The specifications for the Al Wasl office complex has called for the highest standards of finishes and services, says Dr Sadek Owainati, projects director for Arkiteknik International, the consultant on the project.

The main contractor for the project was Al Moosa Contracting (Pioneer).

The tower facades are of curtain-walls and aluminium cladding while the elevations of the block include precast concrete panelling and aluminium cladding. The office block, which has a curved layout with sloping facades, includes nine shops and food outlets with spacious sitting areas.

The office tower, which houses Citibank's office, has one basement level, two levels for the banking hall (ground and mezzanine floor), 14 levels for the office area and two levels of roof deck for various building services. It is served by six passenger lifts and one service lift.

The office block comprises two levels for car-parking (basement and ground floor), five levels for office areas and a roof deck which serves as a roof garden and also accommodates the mechanical plant. It is served by six passenger lifts and two service lifts.

Both buildings have a reinforced concrete framing and are founded on approximately 760 piles of different diameters (1,000, 900 and 600 mm).

During foundation works, due to a high underground water table, a dewatering system had to be designed to lower the water level, in certain areas, up to 6 m below the natural level, says Stan Trojanovic, senior project manager, Al Moosa Contracting.

Detailing the construction techniques utilised on the project, he continues: ''The chosen waterproofing tanking system comprised two layers of 4-mm-thick reinforced membrane with many sophisticated details. Penetration of the underground drainage system through the waterproofing system of the basement slab and pile caps was avoided by encasing all the drainage pipes within the reinforced concrete, as proposed by Al Moosa Contracting.

''For floor structures - designed as ribbed slabs - the main contractor opted for GRP (glass reinforced plastic) moulds, of a flexible length, to cope with varying rib spans. For easier stripping, the maximum length of moulds ordered was 80 cm. As they were made of a flexible material, no air pressure was required for stripping.

''Concreting on the 80-m-high office tower, up to the seventh level, was performed by concrete pumps. Above that, concrete was poured by two hydraulic placing booms - of the self-climbing type, one in each core - which were fed by a stationary concrete pump. Their radii were chosen to cover the whole building including both cores and all columns.

''Flying tables were used for decking on the office tower. As soon as they were placed, work would start on fixing of trough moulds, which was followed by reinforcement placement and simultaneous MEP works.

''For columns and walls, pre-assembled reinforcement cages were lifted, whenever practical. To speed up the construction of core walls, which had a difficult configuration, the formwork and the sequence of casting were adjusted several times. For 200 mm walls, a special concrete mix with 10 mm aggregate had to be used to allow flow of concrete through trimmer bars, fixed around numerous openings.

''One side of the office tower's mezzanine concrete slab has been designed as hung from the slab above, by means of high-strength steel hanger bars of 60 mm diameter, which had to be imported. At a certain stage of construction, these bars were stressed, and only after ensuring that they were properly engaged, was the slab's supporting system removed.

''Due to its geometry, the six-storey office block presented more of a challenge than the office tower, during the structural works phase as well as during the finishing stage.

''The building - which is curved in plan and has inclined external walls with very small tolerances - was a demanding task, particularly for surveyors, carpenters and later for marble and ceramic tile masons. Controlling the deflections of the curved RC spandrel beams, spanning 20 m, and aligning the precast concrete panels, particularly in the curved areas, required special attention.

''A lot of preparation work was carried out in all office areas prior to casting the first areas of internal concrete screeds (75 mm) with embedded flush floor trunking. In order to achieve a good bond, concrete surfaces were hacked prior to placing the screed''

According to Trojanovic, among the major challenges on the project was the safety, welfare and housekeeping, for up to 1,200 workers at the peak of construction. However, during the course of construction no major accidents nor even injuries took place, he stresses.

Turning to other challenges on the project, Trojanovic says: ''The project had a short construction time of just 21 months, compounded by the fact that site design coordination was complex and construction planning called for works on two buildings at the same time,'' he says.

''Other challenges were the office block's configuration and sequencing of building envelope works (aluminium and precast concrete panels); finding system solutions for window-cleaning equipment and garbage chutes, to minimise modifications to be done on the building structure; solving the problem of unsuitable soil conditions in one area under the office block; maintaining efficient communication with the consultant in resolving coordination requirements and fulfilling the consultant's decisions regarding site inspections, approvals of shopdrawings, materials and method statements.

''On the office block, one of the most difficult tasks was to site-coordinate erection works with RC precast panels on one side and aluminium and glazing works, on the other. It required special solutions for access, working platforms, and lifting and protection of already installed panels. For example, the type of scaffolding chosen as being the most appropriate for the installation of aluminium panels to the sloping facades, was one which was not in contact with any of the sloping surfaces. It was designed to be supported through window openings, having standards resting on the internal floor structure, so it allowed unhindered access to all external areas.

''During the complex process of special equipment selection, the most difficult part was finding suitable window-cleaning equipment for the office block, due to various obstructions on the roof, recessed areas in the facade on the first and second floors and due to an inclined facade walls.

''Cranage made a major contribution to the success of the project. In addition to five tower cranes, a lot of mobile cranage was required. Upon completion of the roof structures of both buildings, chillers had to be lifted and positioned. For lifting chiller modules to the office tower's 80-m-high roof, a 400-tonne mobile crane was used.

''For the construction of floating floor slabs for the mechanical equipment, extensive efforts were made with a specialist company, to secure acceptable noise and vibration levels. An acoustic consultant was also engaged to make sure that other sensitive areas have an acceptable noise level.

''With regard to aluminium and glazing works, the unitised curtain-wall system used on the office tower was complex and Alico, the aluminium and glazing contractor, engaged a specialist design consultant to work on the system.

''Precast subcontractor Emirates Precast has shown exceptional skill in producing perfectly curved precast panels as well as elegant louvres structures.''

''This landmark project was finished after great efforts by all participants, which had to come up with a lot of innovative ideas in order to reach the goal,'' he comments.

Both the buildings have central air-conditioning using a chilled water system, refuse chutes which service all floors and window-cleaning equipment.

MEP services in the office tower include: kitchen and toilet exhaust system, basement air-conditioning and smoke extract, staircases and lobbies pressurisation system, main power supply including main LV panel, sub-main distribution board, distribution boards and cabling, standby power supply using a generator and UPS (uninterruptible power supply), low-voltage supply for lighting and power outlet, including emergency lighting, fire detection and alarm system, earthing and lightning protection, telephone system including structural communication cabling, CCTV (closed circuit television) system, audio/public address system, building management system (BMS) and lighting control system, hot and cold water supply, soil and waste drainage system, rainwater system, and fire detection and fighting.

Internal finishes for typical office floors is sand cement screed and washable emulsion on walls of the office tower. Two floors, in addition to all the telecommunication rooms are provided with raised flooring. The basement floor has screed with epoxy paint on walls. Entrances and lift lobbies have a 30 mm patterned marble while staircases have fairfaced concrete with sealer coat.

In the office block, the basement car-park has forced ventilation to clear all exhaust fumes and the staircases have a pressurization system.

Other MEP systems in the office block include: kitchen and toilet extract systems, main power supply distribution including main LV panels, submain distribution boards, distribution boards and cabling, low-voltage supply for lighting and power outlets including emergency lighting, fire detection and alarm system, earthing and lightning protection, telephone system including structured communication cabling, audio/PA system, BMS and lighting control systems, hot and cold water supply, drainage system, storm water system, and fire detection and fighting.

External finishes are precast panels, epoxy paint and structural glazing while internal finishes for the office space floors is screed with dust-proofer and washable emulsion paint on walls. The entrances have marble on floor and wall areas. The basement car-parking have power-floated floors and epoxy paint on plastered walls. Stairs have ceramic tiling.