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In a recent field test, 100kg of bare high explosives (TNT equivalent) was detonated in free air to investigate the performance and behaviour of five sandwich blast doors. The bare charge pack, placed 1.5m above ground level, consists of 365 sticks of PE4 explosive (NEQ factor = 1.19). A single stick of COMP4 booster explosive with a length of detonator chord was placed at the centre of the pack; its purpose was to ensure complete initiation of the PE4 explosive. Blast doors were fabricated as sandwich panels with attendant locking mechanism and shear pins to resist the blast overpressure. Idealised pressure-time histories were used to design the blast doors. Each blast door, located equidistant from one another and arranged in a circle with the explosive charge at the centre, was subjected to different load intensities by positioning them at prescribed range from the explosive source. Details of the blast doors, experimental set-up, blast overpressure data and limited acceleration record are presented. Calculated peak overpressure values, though underestimated, were in agreement with measured data. All the blast doors survived the test, except for one door positioned closest to the explosive source; the excessive blast overpressure at this close range resulted in localised damage to the panel/locking mechanism area. However, the structural system of this door remained undamaged. T. S. Lok, BSc(Hons), PhD, CEng, MIStructE, Eur-Ing, PEng, MASCE, MIES Associate Professor, Nanyang Technological University, School of Civil and Environmental Engineering, Nanyang Avenue, Singapore 639798
The Jurong Island formed by the amalgamation of seven existing islands off Jurong was an attempt by the Singapore Government to create a world class petroleum and chemical industry on the island. The design and construction of a road link to connect the Jurong Island to the mainland was completed with a series of precast gravity caissons. The foundation of the caissons consisted of a layer of stone sill on prepared seabed using dredging. In view of the short overall contract period (24 months), it was most important to ensure that the 96 reinforced concrete caissons be fabricated and installed on time without causing any delay to the subsequent activities such as sand filling which was forming the core of the causeway. Based on the detailed scheduling, it required 12 months to fabricate the 96 caissons. Therefore special fabrication and launching methods were used to overcome the extremely short construction period. This paper describes the construction methods adopted in this project for the fabrication, moving and launching of reinforced concrete caissons by using stationary slipform, Aerogo heavy lift and transfer system, and the floating dock. Seow Kiat-Chuan, PEng, MSc, BEng CPG Consultants Pte. Ltd Choi Sung-Pil, BSc, MKSCE CPG Consultants Pte. Ltd Pang Poh Yong, PEng, BEng, PGD CPG Consultants Pte. Ltd Jimmy Tsen Chee Nam, BEng, MSc (Civ Eng), MSc (Highw Eng) CPG Consultants Pte. Ltd Lim Peng-Hong. MConsE, MSc, DIC, PEng, MIES, BEng CPG Consultants Pte. Ltd
Methods of adding more storeys to an existing building are briefly described. Strengthening of foundations by addition of micropiles and pre-loading is illustrated. Strengthening of existing reinforced concrete columns by plate bonding, reinforced concrete jacketing and polymer impregnation are discussed. The concept and method used for the addition of 14 storeys to an existing hotel and shopping centre has been described. C. K. Murthy, BE (Mys), PhD, FIE(I), FIES, MConsES, MASCE, MSIBL, PEng CKM Consultants Pte Ltd, Singapore A. Murthy, BEng, MIES, PEng CKM Consultants Pte Ltd, Singapore