AN IMPROVED MEANS OF REINFORCING ADOBE WALLS - EXTERNAL VERTICAL REINFORCEMENT

ABSTRACT Traditional adobe (mudbrick) houses are highly susceptible to damage and destruction during seismic events. This vulnerability is particularly acute in developing countries where traditional construction practices and resource limitations result in large stocks of at-risk houses. The current favoured method to improve the earthquake resistance of new adobe houses includes the use of pilasters / buttresses, a crown/ring beam, internal vertical reinforcement (e.g. bamboo, cane, plastic tubing) and internal horizontal reinforcement (e.g. bamboo, cane, wire mesh). Although this method has been observed to significantly delay structural collapse, this paper raises some questions about the capacity of this form of reinforcement to delay the onset of cracking at low intensity ground motions. Furthermore, the complexity of the system is a major obstacle to its widespread use. An alternative system is being developed and tested at the University of Technology, Sydney (UTS), Australia. This system retains the use of a crown/ring beam and internal horizontal reinforcement (wire mesh), however the vertical reinforcement (bamboo) is placed externally and attached to the wall after construction. The bamboo is securely tied to the horizontal and vertical reinforcement and the ring beam, creating a stable matrix. This system can also be slightly modified for the seismic retrofitting / strengthening of existing dwellings. Shake table testing at UTS has shown the system to be an effective means of impeding initial cracking, as well as delaying major structural damage and ultimate collapse. Scale model (1:2) u-shaped wall panels are being subjected to transient dynamic loading using a shake table to evaluate the response to out-of-plane seismic forces. Time-scaled input spectra are being used to induce damaging resonance conditions and the force-displacement characteristics and failure mechanisms of different reinforcement systems are being studied to determine their resistance capacity. This paper presents the results of shake table tests at UTS, as well as providing some discussion on the opportunities and challenges for implementation.