2 August 2012
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The Awa Shirasagi Ohashi Bridge, which includes novel structural systems, was recently constructed in Tokushima, Japan (Figure 1). There were a number of severe design constraints for the project. The bridge is located in a very environmentally sensitive area. The site is also in a seismic region and is frequently struck by typhoons. Furthermore, the bridge was to be founded on soft alluvium, and to be constructed to a tight budget. These exceptionally challenging constraints led engineers to adopt a novel combination of structural forms, including the ‘cable egret’ cable truss system, an improved form of the permanent tubular steel pile cofferdam foundation and a steel- concrete composite sandwich slab deck.
All articles published in the August 2012 issue.
There are still hundreds of high-rise large panel system (LPS) dwelling blocks in the UK. These generally contain ﬂats, but in some cases the accommodation is in the form of maisonettes or another multi-level arrangement. Block owners have a continual responsibility for their safety, which requires periodic inspection and structural assessment. The UK requirements for this particular class of building stem from the 1968 collapse of the southeast corner of Ronan Point, a 22 storey LPS dwelling block. LPS dwelling blocks are basically gravity structures, as are traditional masonry constructed buildings. Typically they comprise precast reinforced concrete ﬂoor and roof components spanning onto storey high structural precast (generally plain) concrete wall panels. Vertical loads are carried to the ground through the structural wall panels, which also provide stability against lateral loads. Historically the guidance used for the structural assessment of LPS dwelling blocks for accidental loads has been the Ministry of Housing and Local Government (MHLG) Circulars 62/68 and 71/68, which were produced shortly after the Ronan Point incident. MHLG Circulars 62/68 and 71/68 together with various other related guidance from that era, were never withdrawn and notionally remain in force today. However, the guidance has been rendered out-dated by subsequent developments. This paper provides an overview of updated technical evaluation criteria and the associated guidance for undertaking a structural assessment of an LPS dwelling block for accidental loads.