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- The influence of self-compacting steel fibre reinforced concrete infill on the flexure strength and ductility of masonry wallsPublication . Oliveira, Luiz Pereira de; Bernardo, LuísThis paper presents an experimental study on the influence of longitudinal reinforcement ratio and steel fibre volume in self-compacting concrete infill on the strength and ductility of reinforced masonry walls subjected to flexure. Flexure tests were performed as four-point bending tests on twelve walls. The analysis of the concrete infill contribution to the walls capacity is made considering recent recommendations for steel fibre reinforced concrete design. A ductility index was defined and applied to study the ductility behaviour of the masonry walls. The analysed variables are the longitudinal reinforcement ratio and the steel fibre volume in the concrete infill.
- Neutral Axis Depth versus Ductility and Plastic Rotation Capacity on Bending in Lightweight-Aggregate Concrete BeamsPublication . Bernardo, Luís; Nepomuceno, Miguel; Pinto, HugoThis article presents an experimental study on the evolution of the neutral axis depth at failure in the critical section with the flexural ductility and plastic rotation capacity of reinforced concrete (RC) lightweight-aggregate concrete (LWAC) beams. For this, the results of a previous experimental program involving RC LWAC beams tested in flexure until failure are used. The variable studies were the concrete compressive strength (between 22.0 and 60.4 MPa and dry density between 1651 and 1953 kg/m3) and the longitudinal tensile reinforcement ratio (between 0.13% and 2.69%). The flexural ductility and the plastic rotation capacity of the RC LWAC beams are characterized by a ductility index and a plastic trend parameter, respectively. The influence of the variable studies, as well as the relation of the flexural ductility and plastic rotation capacity with the values for the neutral axis depth at failure are analyzed and discussed. Some conclusions are drawn which can be useful for the design of RC LWAC beams for flexure. In particular, it is shown that the practical rule of limiting the neutral axis depth at failure to ensure ductile behavior, as used in normal-weight aggregate concrete beams, is also valid for RC LWAC beams.
- Flexural ductility of lightweight-aggregate concrete beamsPublication . Bernardo, Luís; Nepomuceno, Miguel; Pinto, HugoThis paper describes an experimental study on the flexural ductility of lightweight-aggregate concrete beams including concretes with compressive strengths between 22.0 and 60.4 MPa and dry densities between 1651 and 1953 kg/m3. Nineteen simply supported beams were tested until failure. Two symmetrical concentrated loads were applied at approximately one third of the span. Ductility was studied by defining ductility indexes. The main variables are the concrete compressive strength and the longitudinal tensile reinforcement ratio. It is shown that the parameter with higher influence on ductility is the longitudinal tensile reinforcement ratio. The test results are also compared with the requirements from some codes of practice. It is shown that ACI Code requirements give more guaranties as far as ductility is concerned, when compared with European codes.