This study experimentally investigates the mechanical properties of steel fiber reinforced recycled aggregate concrete (SFRRAC). The smaller strength and ductility of recycled aggregate concrete (RAC), compared to those of natural aggregate concrete (NAC), have restricted its use to mainly non‐structural applications in the construction industry. Such limitations in the mechanical behavior of RAC can be overcome by adding industrial steel fiber (SF). In this study, the split‐tensile strength, the compressive strength, the toughness under compression and the elastic modulus for 25 SFRRAC mixes are experimentally investigated. These 25 mixes were prepared from combinations of five different volume fractions of SF, 0, 0.3, 0.5, 0.7 and 1.0% and five different replacement proportions of natural aggregates (NA) by recycled aggregate (RA), 0, 30, 50, 70 and 100%. From experiments, it was observed that the split‐tensile strength, the compressive strength and the elastic modulus of SFRRAC mixes decreased with RA content; the split‐tensile strength and the toughness under compression increased with SF content. However, there was no clear correlation observed between the SF content and the compressive strength or the elastic modulus. Regression models were established based on the RA and SF contents in the SFRRAC mixes to predict their split‐tensile strength, compressive strength and elastic modulus.

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This study proposes an algorithm to solve inverse reliability problems with a single unknown parameter. The proposed algorithm is based on an existing algorithm, the inverse first-order reliability method (inverse-FORM), which uses the Hasofer Lind Rackwitz Fiessler (HLRF) algorithm. The initial algorithm analyzed in this study was developed by modifying the HLRF algorithm in inverse-FORM using the Broyden-Fletcher-Goldarb-Shanno (BFGS) update formula completely. Based on numerical experiments, this modification was found to be more efficient than inverse-FORM when applied to most of the limit state functions considered in this study, as it requires comparatively a smaller number of iterations to arrive at the solution. However, to achieve this higher computational efficiency, this modified algorithm sometimes compromised the accuracy of the final solution. To overcome this drawback, a hybrid method by using both the algorithms, original HLRF algorithm and the modified algorithm with BFGS update formula, is proposed. This hybrid algorithm achieves better computational efficiency, compared to inverse-FORM, without compromising the accuracy of the final solution. Comparative numerical examples are provided to demonstrate the improved performance of this hybrid algorithm over that of inverse-FORM in terms of accuracy and efficiency.

The global demand for construction aggregate exceeds 26 billion tons per year. With global policy attention directed towards climate change, environmental and economic sustainability, changes are required to the Australian construction industry regarding the extraction of natural resources. In particular, the concrete industry requires seeking innovative, sustainable solutions for reducing the impact of construction and maintenance on the environment. The majority of structures in Australia use reinforced concrete. Therefore, using environmentally and economically sustainable materials such as recycled concrete in construction would preserve natural resources and reduce construction waste and overall costs. There is considerable research available on the use of recycled concrete as a construction material and the use of steel fibers as structural reinforcement has been studied since the 1960’s. However, there is very little research on the combination of the two as a construction material for concrete structures. This study focused on secondary beams made of recycled concrete with the incorporation of steel fibers. This combination offers a structurally sound material that will provide a durable and sustainable solution to Australian Construction Industry. Experimental studies were conducted to validate the performance of the new material in a structural application. Based on the results of the study, recommendations for future research and design applications using these materials are made.