Issue 16

As a result of identified concrete strength deficiencies, in a number of reinforced concrete multistorey public housing blocks constructed in the 1960s and early 1970s, the Hong Kong Housing Authority initiated a programme of structural appraisals, to assess the buildings’ overall structural adequacy and to determine strengthening requirements where appropriate. This paper describes the methodology which has been developed and the criteria which have been adopted in undertaking these appraisals, with particular reference to the assessment of applied loads, available material strengths and appropriate partial safety factors to be used in evaluating load effects and structural resistance. B.J. Stubbings, P.R. Ainsworth, R. Crane and R.A.M. Watkins

Since the mid-l950s, the Hong Kong Government has housed some 2.8M people in approximately 1500 high-rise, reinforced concrete buildings. By the early 1980s, the Government’s Housing Department was facing growing maintenance problems in the older blocks. These difficulties arose in part from the common problems of reinforcement corrosion and spalling which are now being faced worldwide, and also because of generally low and extremely variable concrete strengths. This paper describes, firstly, how these defects were identified and how priorities for further action were established through the development of ranking systems. It goes on to discuss the techniques utilised in assessing the nature and extent of the defects, including visual survey and testing programmes, and the development of a structural appraisal methodology. Finally, the ways in which the defects are now being redressed, and the repair and strengthening methods being used, are outlined. D.P. McNicholl, P.R. Ainsworth, M.V. Harley, B.J. Stubbings and R.A. Watkins

Since the mid 1950s, the Hong Kong Government has housed some 2.8 m people in approximately 1500 high-rise reinforced concrete buildings. Since the early 1980s the Government’s Housing Department has faced growing maintenance problems related in part to the low concrete strength encountered in some older blocks. R.A.M. Watkins and D.P. McNicholl

Environmental enhancement and the ‘aims of structural design’ We have received a plea from Mr R. P. Strauss of Stratford-upon-Avon to the effect that, as structural engineers, we should more specifically include ‘environmental enhancement’ as one of our declared ‘aims’: ’The IStructE document Aims of structural design proposes function, economy and safety as the desired objectives. In the first ‘cost v. maintenance-cost’ equations of economy, an additional ‘environmental enhancement factor’ should be considered. Environmental enhancement refers to the impact of the chosen structure on its users and beholders rather than, for example, the flood protection aspects of the Thames Barrier or the pollution reduction aspects of water treatment. Verulam