Dynamic response of mortar-free interlocking structures

Economical earthquake-resistant housing is desirable in seismically active rural areas of developing countries. These regions often suffer a significant loss of life during strong ground motion because of lack of seismic-resistant housing. To enable an efficient and cost-effective solution, a new concept of construction was investigated utilising structures consisting of (i) interlocking blocks with relative movability at the block interface and (ii) coconut-fibre rope reinforcement. The interlocking blocks were prepared with coconut fibre reinforced concrete. A mortar-free construction can facilitate more energy dissipation during a seismic event, because of the relative movement at the block interfaces. Four structures were considered: two columns (with and without ropes) and two walls (with and without ropes). This paper reports on the investigation of the in-plane behaviour of the mortar-free structures under different loadings: push over, snap back, impact, harmonic and earthquake loadings. The influence of un-grouted rope reinforcement on the fundamental frequency, damping ratio, induced accelerations, top relative displacement, base shear, overturning moment and block uplift is investigated. The harmonic tests were more accurate in finding the fundamental frequencies of the structures compared to the push over and snap back tests. As expected, the structures with ropes were stiffer than the structures without ropes. The structures with ropes had smaller relative top displacements and block uplifts compared to the structures without ropes. The damping of the structures without ropes was higher than that of the structures with ropes. The damping increased with the amplitude of input motion. The same trend was observed for the maximum overturning moment, uplift and rope tension.