THE ARUP JOURNAL I C i i >- SUMMER 1985 I i Vol.20 No.2 Summer 1985 Contents Practical matters decking plus a layer of edge trim occurred, Published by With traditional concrete construction the studs detached. The site test seems Ove Arup Partnership 13 Fitzroy Street. London W1P 6BQ there are practical aspects which, because crude but appears to be quite effective. THEARUP they are so familiar, are often taken for Large holes for lifts and such like are granted by the design team or left in the formed by the decking laid to suit with edge Editor Peter Hoggett capable hands of site staff and the trim all round. Smaller holes for services Art Editor Desmond Wyeth FSIAD can more conveniently be formed by JOURNAL Assistant Editor David Brown contractor. Similarly with composite construction there are many practical running the decking through, boxing out Leslie & Godwin, Farnborough, aspects but in contrast these should be prior to concreting, then cutting the deck by Mike Bonner and Terry Raggett considered by the design team. afterwards. Steelwork erectors are permitted to work Because of the timescale of erection and Ronald Stewart Jenkins: without all the safety rails required for the comparatively small quantities engineer and mathematician, general labour gangs. This is one involved, the contractor will generally be by Ronald Hobbs advantage in having the profiled decking looking to pour quite large areas of included with the steelwork sub-contract, concrete at a time. On Farnborough where The Merlin Hotel, 14 so that the erectors also lay the decking. the concrete was pumped and power- Perth, Western Australia, However safety rails will then be required floated, the contractor was aiming to by Keith Pollock before reinforcement fixing and concreting. concrete one floor per day in each wing. The spacing of shear studs should be a Although this was a little optimistic for the City site: Lovat Lane, 18 multiple of, or the same as, the decking rib first wing where a learning curve situation by Deborah Lazarus centres where the decking crosses the applied, he did achieve it for each of the last beam. Conversely where the decking is two wings. Farnborough Road office development, 20 parallel to a beam, it should be arranged so Conclusion by Svend Jensen and Peter Lunoe that the ribs are spaced equidistant about The Farnborough Office Development has the centreline of the beam clearly demonstrated some of the Site testing of the shear studs is very advantages which can be gained by using simple. A small proportion are bent over to composite construction in the right 15° from the vertical, usually with an odd circumstances: given the high standards length of scaffold tube. If a stud detaches, required, the building has been completed or a visual inspection shows any fractures quickly and at a relatively low cost. in the weld, then it is condemned. On this project we found that generally studs Credits welded through a single layer of decking Client: were all sound, whereas in the few places County and District Properties Ltd. where two layers of decking or a layer of Front cover: Leslie & Godwin building: main office entrance (Photo: Peter Cook: Designed by: Arup Associates) Architects: Back cover: Ronald Jenkins Scott. Brownrigg and Turner Fig. 8 Quantity surveyor: Roadway under west wing Banks. Wood and Partners (Photo: Ernie Hills) Services consultant: Leslie & Godwin, Fig. 9 Michael Aukett Associates Escape stair in wings Landscape consultant: Farnborough (Photo: Svend Jensen) Eachus Huckson Partnership Main contractor: Fig. 10 Costain Construction Ltd. Arup Associates View along south wing Steelwork sub-contractor: Group 5 (Photo: Ernie Hills) Octavius Atkinson & Sons Ltd. Mike Bonner V Terry Raggett The brief The Leslie & Godwin Group commissioned Arup Associates in September 1978 for the design of an owner-occupied office building totalling about 9,500m2 at Farnborough, Hampshire. The brief required a mixture of deep and shallow office accommodation with lettable commercial space at ground floor level. Outline proposals were approved by Leslie & Godwin in December 1978 but because of reorganization within their company, the scheme was temporarily halted. In March 1980 ownership of the proposed building was acquired by the Imperial Group Pension Trust Ltd. who, through their agents Richard Ellis, amended the brief to one considered more suitable for a 4 speculative building. The office space was > to be of a constant width of not more than 18m which could incorporate enclosed offices at the outer perimeter and also capable of being subdivided into separate lettable areas of between 600m2 to 850m2. The dining area was required to cater for a total of 450 people in three separate sittings and was to be provided with separate coffee lounge and bar. The ground floor had to include the pedestrian right-of-way developed into an enclosed shopping mall with as much commercial lettable space as possible on each side. In addition, covered space for 20 cars was required as part of the site right angles to the web, this method is of Each step of the flight is formed from a audible range, the low frequencies can be great benefit wl-.ere beams are connected steel plate bent to give a 75mm deep tray, felt and there is a danger that they may to the stanchion from two or more which is then filled with normal concrete induce high or audible frequencies in some directions. after steelwork erection. This gives the final part of the building, even far away from the Stanchion splices were initially stipulated stair ready for carpeting. source. To combat this the roof plantroom as being to full strength of the section, For the semi-circular landings the primary has a floating floor made with an bearing in mind that most stanchions were steelwork is two 150mm square hollow independent, mesh reinforced concrete designed to 90-95% of their capacity and section members, welded to give a T shape slab cast on a metal decking, which is some a little more. The fabricator chose to in plan. The outer edge is a curved supported from the structural floor by splice stanchions 500mm above second 100 x 100mm angle, acting both as edge resilient rubber pads. Apart from acting as floor level, and proposed end bearing for former and structural member. Holorib a structural isolator the floating slab adds axial load with normal bolting/plates for profiled decking and concrete then to the general mass of the floor structure moment capacity. After inspecting his complete the landing on site, again ready and provides high frequency attenuation works and the quality of machining, we for carpeting. Corrosion and fire protection agreed to the end-bearing proposal. To The stairs and landings are simple in The question of corrosion protection of the assist him we also gave more specific concept and construction. What is not so steelwork was discussed with the client at design values for stanchion moments at his obvious is the care required in design and a very early stage and it was agreed that chosen splice locations, enabling him to detailing to achieve this. Stairs often throw although it was basically in a dry, internal minimize the bolting/plates requirements. up problems disproportionate to the environment some form of protection Stability amount of work in them, and the ones in should be provided. All the internal this building were no exception. For steelwork, apart from the top flange of For structural stability the cruciform beams to which shear studs are welded, building shape is very suitable. Diagonal example the secondary core landings lie outside the perimeter line of stanchions, has been painted with a two-pack epoxy bracing is provided for both directions in primer. In addition the members along the the central core and for the transverse giving a most distinctive feature to the final building. However, the resultant force perimeter, which are more likely to become direction in the escape stair cores, at the damp, were given an MIO barrier coat. end of each wing. The locations of diagonal eccentricities, at mid-height level on the stanchions, proved quite a problem. Some The superstructure was required to have a members had to be co-ordinated with fire resistance of one hour and for internal services ducts and doorways into the cores, specially-shaped brackets, fitting com• pletely within the stanchion flanges so as beams and columns this was achieved by a so each elevation of bracing is designed as vermiculite spray, Mandolite P20, and by an N-truss arrangement. To allow for any not to protrude either into the cladding zone or the stairwell, were the answer. fire blankets at the expansion joints. direction of wind loading, diagonal The external stanchions at ground and first members were designed both for tension Structure-borne noise and vibration The steel-framed structure, being lighter floor were encased in concrete, with a and compression, using square hollow 50mm mesh reinforced cover, after section steelwork. and generally more flexible with a lower damping capacity than that of an erection. Expansion joints are provided towards the equivalent concrete structure, is more inner end of three of the wings, at locations susceptible to vibration. However, As far as the deck is concerned a Restricted chosen to give simple detailing. To permit calculations indicated that the structural Fire Engineering Approach was adopted to longitudinal movement but provide response of the building is perfectly calculate the extra fire reinforcement transverse stability the joints were made as which, in addition to the A98 mesh in the satisfactory for normal office use. The office entrance was to be separate into two and, although the site was left over sliding joints with dowels in the concrete top of the slab, amounted to an 8mm bar in from the entrance to the shopping mall and from the Kingsmead development, it is the deck.