Assessment of the realistic stiffness and capacity of the connections in quincha frames to develop numerical models

Peru is one of the most seismically active countries in the world, this fact highlighted by several destructive earthquakes in recent years. The centre of Lima has a large number of historic structures with a ground floor in adobe, and their upper storeys in quincha, a traditional technique consisting of a timber frame with an infill of canes and mud. Despite the existence of a large number of buildings containing this technique, very little is known about its seismic performance. In order to investigate this, a series of experimental tests on quincha frames, with and without the infill, have been carried out previously, with the aim of quantifying the lateral behaviour and identifying vulnerable areas. The present paper details work carried out to develop a finite element model of the test frames without infill. This model of the timber frame will enable an accurate representation of the frame behaviour to be developed before adding the infill of canes and mud to the model. As the behaviour of the infill material and its connection to the frame is difficult to determine, characterising the timber frame with a high degree of accuracy ensures that the contribution of the infill can be globally quantified from the overall experimental results. The beams and posts are connected by cylindrical mortice and tenon joints, with a diagonal bracing member providing some lateral restraint. The connections have been modelled semi-rigid springs, with the stiffness calculated using variations of the component method. This was found to give very similar results to those obtained experimentally.