Red Line adds tension to the Post Tensioning industry in Qatar

STARTSInnovation is possibly one of the key elements that lead to progress and the construction industry is one sector that seems to abound with a variety of new technologies and innovation methods to make building better, simpler and faster. According to Mr. Sameel Hamza, the Operations Manager of the Red Line Post Tensioning Contracting company, post tensioning is one of the applications that has consistently been growing in the past few years. The technology is based on the principle of post-tensioning where the prestress is permanently introduced into the structure after the concrete has hardened. Hamza explained that this is achieved by the stressing of suitably arranged, high-strength prestressing tendons, usually arranged in parabola-like formation. Post-tensioning generates favourable stress conditions in the structure, enabling efficient use of building materials while controlling deformations under severe conditions.

The use of the post tensioned slab system has been consistently growing in recent years. Typical applications are: private residential housing, offices, car parks, shopping centres, hospitals, hotels, bridges and apartments and industrial buildings. The main advantages of the post tensioned slab over the conventional reinforced concrete slab, is that allowance can be made for increased clear spans, thinner slabs, lighter structures, reduced cracking and deflections, reduced storey height, repaid construction and better water tightness. These advantages can result in significant cost savings.  There are also some situations where the height of the building is restricted, so a technique that allows for the planned amount of storey’s at a reduced height has allowed additional storey’s to be constructed within the planned construction. The most impressive and clearly visible application of post tensioning is the greater spans and larger column free areas that one sees on the facades of highrise towers and hotels. Hamza said that they had constructed the front of the Grand Hyatt Hotel Doha which has a 28m span.

The Redline Post Tensioning company describes itself as one of the newest, multi-disciplined engineering and post tensioning contracting companies in the State of Qatar. It started its work in 2007 and currently has 28 projects in various stages of completion. From 2007 it has completed more than QR 40 million worth of projects. Hamza describes post tensioning as a specialized construction application and is particularly effective for building slabs and bridges. It is only used in the horizontal element of construction and started being used in Germany in the early 1920’s. The application was brought to the United Arab Emirates in the late 1990’s and now almost 80 – 85% of buildings use the post tension building method as opposed to the precast concrete slabs.

Red Line Post Tensioning Company provides an extensive service for the construction of Post Tensioned Slab Systems covering the following:

Project feasibility study for post tension application. Preliminary design and cost estimation. Final design and shop/working drawings. Complete supply and installation of post tensioning systems.

Complete services for formwork set up, reinforcement fixing, concreting and post tensioning installation of slab structures.

The RED Line Post Tension slab system in association with SEVER Technical System Pvt. Ltd. Australia consist of a fully integrated hardware and stressing equipment system of engineer designed components which meets the exact requirements of appropriate BS 8110 & AS3600 codes. The RED Line Post Tension slab system is manufactured to meet strict quality control standards and tolerances thus enabling designers engineers and Post Tension professionals to specify and use the system with confidence. The system has been designed, manufactured, and installed in a wide array of projects in the industrial, Commercial and civil engineering industry. The RED Line stressing components and equipment enjoy an enviable reputation for integrity.

Some of the projects that have been completed by the Red Line Post Tensioning company:

Al Baraka Twin Towers, 52 storey’s, City Centre, Doha. Dukhan Towers, Doha, Qatar. Al Asmakh Hotel Apartments, 7 storey’s, Doha. Al Handasa Office Building, (2) Basements, Ground, and 12 storey’s, Doha. Viva Bahria, basement, ground, 20 storey’s high, The Pearl, Doha, Qatar.

Hamza added that Red Line was also involved in the construction of the Islamic Bank Tower in West Bay which was a joint venture with VSL, a leading post tensioning company who was involved in completing an LNG Plant for QatarGas, the Salwa Road/Immigration Interchange and also the tallest Hotel in the world – the Burj Al Arab, Dubai, UAE.

The following projects are in progress and as such do not have end dates attached to them yet as they are dependent on other construction processes:

Al Baker Executive Towers, Al Dafna-Doha, 2 highrise towers Al Mohanna Trade Centre, 60 storey’s high plus three Basement and Ground

floor, Doha City Centre. Al Wefak residential building, large residential project comprising 2 buildings,

includes a Basement and Ground floor, Al Wakra.

According to Hamza, the Red Line Post Tensioning company has been invited by Ashghal to tender for the new F-Ring Road. The demand for infrastructure in Qatar is keeping pace with the growth of Qatar and also the growth of Doha as a transport hub and key commercial centre in the Gulf. They have also just been awarded a contract by Ashghal for the Hamad Medical City worth QR 250 million and expected completion date mid-2011.

CONCLUSIONIn conclusion, one can note that there is a definite move towards large spans in buildings due to the fact that there is more than ever an increased emphasis on providing large

uninterrupted floor space for higher rental returns. Post-tensioning is an economical way of achieving spans larger than 7.5 metres and as spans increase apparently, so do thesavings. According to Ed Cross, the Technical Director of Austress Freyssinet Pty Ltd the most significant factor affecting the cost of slab system post-tensioning is the tendonlength. There are of course a few other factors which will affect the contract price and this is best discussed with a post tensioning professional. The main structural schemes available are the flat plate, flat slab and banded slab. The banded slab is the most cost efficient but the costing will be affected by factors such as floor to floor heights, services, amongst other things. Cross also says that for high rise construction and highly repetitive floor plates, the use of more specialized structural schemes is appropriate with emphasis on systems formwork. It is not uncommon for post-tensioning to be rejected in certain types of building project due to a perceived lack of flexibility. However, tendons are usually spaced sufficiently far apart to allow penetrations of reasonable size to be made later, without cutting through the tendons. Should it be necessary to cut tendons this can easily be achieved using well established methods.ENDS.

Words: 1,116