02 Technical Journal Papers 016 - 033 Plan Design Enable I am delighted to introduce you to the second issue of the Technical Journal. This journal continues to bring together technical papers that have been produced across the Atkins Group by our own exceptionally talented members of staff. It showcases the technical excellence that thrives within Atkins, featuring papers from disciplines such as aerospace, bridges, buildings, environment, highways, intelligent transport systems and water. Atkins is a multinational engineering and design consultancy, providing expertise to help resolve complex challenges presented by the built and natural environment. As a large organisation, with around 18,000 people, Atkins has many very strong technical abilities. To assist in meeting our customers increasing demand for a complex mix of services drawn from a number of our businesses around the world, our Technical Networks were launched at the 2008 Atkins Group Conference. These networks will ensure we consistently identify, share, celebrate and promote our technical expertise to deliver excellence. The networks are chaired by our most respected specialists, providing leadership in their appointed network, and it is through these Network Chairs that many of the papers have been collected. The papers contained in this journal demonstrate how we rise to the challenges presented to us and provide our clients with innovative, cost effective and sustainable solutions. I hope you enjoy the papers presented as much as we enjoyed producing them. Chris Hendy Chair of Technology Board Transport Solutions Highways & Transportation FORWARD FORWARD Technical Journal 2 Papers 016 - 033 016 - Structures Bahrain World Trade Centre 5 017 - Structures Transverse web stiffeners and shear moment interaction for steel plate girder bridges 13 018 - Structures Wind-induced dynamic failure of a slender sculpture 27 019 - Structures The role of aggregate in reinforced concrete exposed to chloride environment 33 020 - Structures Design of continuity slabs and the Metro viaduct designs 41 021 - Structures Replacement of the stay cables on Penang Bridge 47 022 - Structures Lateral buckling of steel plate girders for bridges with flexible lateral restraints or torsional restraints 63 023 - Intelligent Transport Systems Civil Certification – The new approach to ensuring fitness for purpose for enforcement equipment in England and Wales 75 024 - Intelligent Transport Systems Using ITS to deliver the network management duty of the traffic management act and improve journey time reliability for road users 79 025 - Intelligent Transport Systems What happens when the control centre is not there? Technology resilience for the Highways Agency regional control centres 87 026 - Intelligent Transport Systems Technology resilience for Highways Agency network operations 91 027 - Highways Developments in highway design standards: Key issues for highway authorities 95 028 - Highways Atkins’ Best Practice Guide for Integrated Data Management on Highways Projects: The first steps 99 029 - Water & Environment A new approach to legally protected species: Ecology mitigation for transport schemes that need not cost the earth 107 030 - Water & Environment Puny Drain diversion, King’s Lynn, UK 109 CONTENTS 031 - Water & Environment Technical report by Traffic Wales into cause and subsequent analysis of the reasons for the failure of the tunnel fire main at the east portal of Conwy Tunnel 113 032 - Aerospace Composites methods development under the next generation composite wing (NGCW) research programme 121 033 - Virtual Reality Applications of Virtual Reality in transportation projects 127 Bahrain World Trade Centre 016 Arshad Khan Martin Halford Associate Director - Structures Consultant Middle East & India V-Consult Atkins Surrey, UK Manama, Bahrain Abstract The Bahrain World Trade Centre (BWTC) development comprises twin 240m high office towers rising above a 3-storey podium development adjacent to the Sheraton Hotel in the Commercial Business District of Manama, Bahrain. The design features three horizontal axis wind turbines mounted between the towers, taking advantage of the prevailing onshore wind to generate electricity, which posed unique challenges that had to be overcome. This paper covers the basis of design, the wind tunnel testing undertaken for the project and the ground conditions encountered on the site. The foundation design is described, including consideration of soil-structure interaction effects at the interface between the piled and ground bearing foundation elements. The paper also describes the framing systems adopted for the primary reinforced concrete structure and the floors, with discussion of the benefits of early contractor appointment on the selection of floor systems and formwork. The structural steelwork elements, including the spire and the panoramic lift enclosure, are also described. 1. Introduction Bahrain World Trade Centre is located within the centre of the Kingdom’s Commercial Business District, Manama, with direct access off the King Faisal Highway. It forms the focal point of a masterplan to rejuvenate an existing hotel and shopping mall. Rising to 240 metres in height, the twin office towers create a dramatic focal point visible throughout the Kingdom. The concept design was inspired by the traditional Arabian “Wind Towers” in that the shape of the buildings harness the prevailing onshore breeze from the Gulf. Three 29- metre diameter horizontal axis wind turbines are mounted on bridge structures between the sail shaped towers, providing a renewable source of energy for the project. In addition to the office towers, the development includes an extension to the existing retail mall, STRUCTURES new restaurants and cafes, refurbishment of the adjacent 5-star hotel and 1,700 parking spaces. The twin towers are framed predominantly in reinforced concrete, with structural steelwork used for the clad steel spire, panoramic lift enclosure and mezzanine floors. There are 45 floors (excluding mezzanines) from the ground floor of the podium, as well as a 4.5 metre deep single storey basement. FIGURE 1. BAHRAIN WORLD TRADE CENTRE DURING CONSTRUCTION WITH THE TOWER CRANE STILL IN PLACE, JUNE 2007 5 016 Bahrain World Trade Centre The design was carried out on a fast-track basis following 3. Ground conditions an early appointment of the contractor, Nass Murray & Roberts Joint Venture, The contractor provided value engineering input at the design stage, particularly A ground investigation was undertaken by Al Hoty on the selection of floor and formwork systems. Analytical Services during March and April 2004. The site is formed on reclaimed land comprising loose to medium dense silty fine sand. The depth of fill 2. Wind environment and above the old seabed ranges from approximately 2.5m to 3.5m and the old seabed comprises a zone wind tunnel testing of nominally 1.0m thick very soft silty clay. The old seabed is underlain by weak carbonate sandstone (Calcarenite) and carbonate siltstone Following consultation with the authorities in Bahrain, (Calisiltite) to approximately 31m, with instances of a BS 6399-2 mean hourly basic wind speed of 26 bands of very weak completely weathered siltstone. m/s was adopted for the design. Wind tunnel testing The carbonate siltstone is underlain by moderately was undertaken by BMT, modeling both the towers strong Limestone at a depth of approximately 31m. The and the surrounding low and medium rise buildings. limestone was generally proven to a depth of 36m. A force balance test was undertaken to determine structural loads and to predict accelerations at the Ground water was observed at approximately 1.8m depth highest occupied floors. A separate pressure-tapping within the made ground and the results of chemical tests model was used to determine cladding pressures. The indicated high sulphate concentrations in the soils. two models were used together in determining the downstream effects of one tower on the other. Tests were also undertaken to evaluate pedestrian comfort at the 4. Foundation solution ground floor and in public spaces on the podium levels. A cautious approach was adopted in interpreting the structural loads derived from the wind tunnel testing. Each tower has a separate continuous piled raft This was because of uncertainty regarding directional foundation at basement level. The raft slabs vary in factors appropriate for extreme storm events, particularly thickness according to loading and incorporate lift pits. given the limited available wind data. As a result, it was Beneath the main cores the raft thickness is 3.0 metres decided that a minimum directional factor of 0.9 would and the piles are 1200mm diameter, closely spaced be used. This still gave reductions of up to 20 percent for and rated at 18MN safe working load. Away from the critical wind directions where peaks in wind load indicated main core the raft thickness reduces progressively to aerodynamic lift occurring due to the plan shape of the 2.0 metres and the piles to 1050mm diameter, more towers. The peak wind load on each tower derived from widely spaced and rated at 8MN safe working load. the wind tunnel test results was approximately 16MN. The loads acting on the pile group are predominantly Building accelerations were calculated in order to allow dead loads, imposed loads and wind loads. These act occupancy comfort to be assessed at the upper floors. in combination to generate maximum and minimum The results of this assessment, based on