时间: 2016年12月26日 上午10点
地点: 土木楼617
报告人: Ir Dr P.L. NG
Abstract: Shrinkage of concrete refers to the volumetric reduction due to loss of pore water. If the shortening movement is restrained, tensile stresses and shrinkage cracks may develop in the structure. Creep of concrete refers to the gradual increase in deformation under sustained load. It could compensate part of the effects of restrained shrinkage by gradually reducing the shrinkage-induced stresses. Construction control aims at minimising the adverse effects or maximising the beneficial effects of the time-dependent movements and deformations. Conventionally, the incorporation of creep and shrinkage effects in finite element analyses is rather complicated and this has made the analysis of construction control measures difficult. To tackle this problem, a new approach of analyzing the creep and shrinkage effects by finite element method has been devised. Time-step analysis is adopted and the stage-by-stage construction is simulated by assigning appropriate element stiffnesses for the partially completed structure. The locked-in strains due to increase in elastic modulus as the concrete hardens are incorporated in the element formulation. Furthermore, a remnant creep based visco-elastic model is developed, whereby the remnant creep strains are employed to determine the incremental creep strains. This circumvents the need for memorising the element stress histories and significantly enhances the computational efficiency. Numerical examples of reinforced concrete floor system constructed in stages are presented, where different construction control measures are simulated and their effectiveness is assessed.
Biography: P.L. Ng (BEng(CivE), PhD, MBA, BEAM Pro, FAIIB, FHKCI, FHKIUS, MHKIE, MICE, APEC Engineer, CEng, Eur Ing, IntPE, RPE) is a visiting adjunct professor in the Faculty of Civil Engineering, Vilnius Gediminas Technical University in Lithuania. He obtained his Bachelor of Civil Engineering and Doctor of Philosophy degrees at the University of Hong Kong. After graduation, he has been involved in the design and construction of a number of major infrastructure projects in Hong Kong and he is chartered civil engineer in Hong Kong, United Kingdom, and Europe. He is an Executive Board member and an honorary secretary of the Hong Kong Concrete Institute. He has more than 15 years of experience in fundamental and applied research, and his research interests are in the areas of sustainable concrete materials and concrete structures. He is serving in the editorial board of 4 international journals, and he has published more than 80 technical papers. He was the recipient of Certificate of Merit of The HKIE Innovation Awards for Young Members in 2013 and The HKIE Outstanding Paper Award for Young Engineers/Researchers in 2012.
发布人：杜进生