Enhancing ductility of reinforced concrete columns : Hong Kong case study
by Wong Ho Fai
M.Phil. Civil Engineering
xviii, 144 leaves : ill. ; 30 cm
Hong Kong is located in a low to moderate seismicity region. The earthquake risk is not nil. Traditionally, the engineers do not consider the seismic effect when they are designing the structures of the buildings. Instead, they put significant emphasis on the wind effect. This may cause a potential danger in buildings if there is any earthquake in the region....[ Read more ]
Hong Kong is located in a low to moderate seismicity region. The earthquake risk is not nil. Traditionally, the engineers do not consider the seismic effect when they are designing the structures of the buildings. Instead, they put significant emphasis on the wind effect. This may cause a potential danger in buildings if there is any earthquake in the region.
The seismic design for the severe earthquake region requires special steel detailing for reinforced concrete structures in order for the structures to behave in ductile manner and dissipate the earthquake energy by inelastic action. For R.C. columns, they require high steel ratio and close spacing of stirrups to provide adequate confinement for the concrete. However, in the case of Hong Kong, it is not wise to adopt directly the same design for strong earthquake. The construction cost will increase significantly. The most appropriate way is to propose an improved reinforcement detailing, which can reasonably enhance the ductility of elastically designed R.C. columns.
The objective of the research is to investigate the ductility of R.C. columns with Hong Kong reinforcement details and make suggestion for the current practice for columns in order to enhance ductility of the columns for the case of Hong Kong without increasing the cost and construction difficulties significantly.
In the experimental study, large-scale specimens with different lateral reinforcement arrangements have been tested. The performance of each specimen is evaluated based on ductility capacity and energy dissipation ability. The tested sample is under constant axial load and increasing lateral reversals.
It has been shown that the addition of crossties into the cross section, but maintaining the similar stirrup ratio, can effectively improve the performance and enhance the ductility capacity of the columns with Hong Kong reinforcement details.
Design recommendations based on the experimental study have been presented for the non-seismically designed R.C. columns according to:
(1) Demand and Capacity (2) Construction difficulties (3) Cost of construction
The suggestions may be served as a reference to practical designers or contractors for moderately seismic design of reinforced concrete columns.