Specially processed steel cord (SC) macrofibres, each consisting of five twisted steel fibres, are used to improve the post-cracking behaviour of cementitious composites. The long steel cords have a large diameter, and are characterised by high tensile strength, frictional bond strength and flexural rigidity. In addition to these steel cord macrofibres, microfibres are used to enhance the snubbing strength and total tensile behaviour of the composite. The two specific hybrid fibre blends studied in the present paper are SC and polyethylene (PE), as well as SC and polyvinyl alcohol (PVA) fibres. The objectives of the current study are to explore the mechanisms by which fibres interact with the composite matrix, and to provide a rigorous characterisation of the performance achievable with hybrid-fibre-reinforced cementitious composites (HFRCCs). Cement-based composites containing large volume fractions (1·0∼2·3%) of various hybrid fibres were compared in terms of flow and fibre dispersion, as well as compressive, splitting tensile, flexural and uniaxial tensile properties. The workability of HFRCCs is governed by the high surface area of the microfibres. The results confirm that the flexural strength, tensile strength and ductility (pseudo-strain-hardening) of HFRCCs are tremendously improved in comparison with mortar or monofibre systems. Furthermore, there is a synergy effect in the microfibre and macrofibre hybrid systems.

The current study examines the effects of the deformation behaviour of cementitious material ductility on the seismic performance of shear-dominant coupling beams. Matrix ductility and reinforcement layouts comprise the main testing variables. Three short coupling beams with two different reinforcement arrangements and matrices are constructed and tested. They are subjected to cyclic loading under a suitable experimental set-up. All specimens are characterised by a shear span–depth ratio of 1·0. The reinforcement layouts consist of a classical scheme and diagonal scheme without confining ties. The effects of cement-based matrix ductility on crack patterns, failure modes, hysteretic characteristics and the ultimate shear load of the coupling beams are examined. The combination of a ductile cement-based matrix and steel reinforcement is found to result in improved energy dissipation capacity, simplification of reinforcement details, and damage-tolerant inelastic deformation behaviour. Test results show that high-performance hybrid fibre-reinforced cement-based composite (HPHFRCC) coupling beams behave better than normal reinforced concrete (RC) control beams. These results are evidenced by the tensile deformation capacity, damage tolerance and tensile strength of HPHFRCC material.

Infilled frames have been investigated by many researchers during the last few decades. It is noted that frame structures incorporating infill walls have shown definite economic and performance advantages over conventional rigid-frame structures when the structures are required to resist large lateral loads due to earthquake ground motion. The objectives of this study are to evaluate the effect of notches in the infill walls and to investigate the effect of the ductility of cementitious composites, particularly strain hardening and multiple cracking, on the seismic performance of infill walls subjected to displacement reversals. The experimental investigation consisted of cyclic loading tests on four 1/3-scale models of infill walls. Material ductility and notches in the infill walls were the main variables in the test. In the test results, as expected, strain-hardening cementitious composite infill wall specimens showed multiple crack patterns due to the bridging of fibres and stress redistribution in the cement matrix. Although the strain-hardening cementitious composite infill wall had a less effective section near the notched mid-section, it showed a higher strength and energy dissipation capacity than those of the reinforced concrete infill wall specimen without a notched mid-section.