ABSTRACT Concrete stands as a fundamental material in the construction industry. However, it encounters challenges such as cracking, crumbling, or disintegration at elevated temperatures, attributed to high thermal stresses and low tensile strength. This study addresses these issues by reinforcing concrete samples with steel and polypropylene fibres, exposing them to temperatures ranging from 25 to 800°C, and conducting mechanical tests. In order to provide a comprehensive examination, a concrete mixture containing lightweight aggregate was also prepared and tested along with other mixtures. The test results showed that adding steel and polypropylene fibres enhanced or maintained compressive strength up to 200°C compared to the control sample. Furthermore, samples containing steel fibres exhibited the highest tensile strength across all temperatures. Notably, at 600°C and above, the lightweight concrete sample demonstrated comparable or superior compressive strength as well as tensile strength compared to the control sample. In addition, it was observed that polypropylene fibres began to melt at 400°C, leading to a decline in compressive and tensile strength in samples containing this fibre type at temperatures exceeding 400°C.

ABSTRACT The masonry veneer wall system relies on metal wall ties to connect the outer masonry leaf to the internal frame, ensuring structural stability. In Australia, a masonry veneer wall typically consists of a timber frame that has galvanised wall ties fixed to the side of the timber studs, with a nail or screw, spanned across an air cavity to the external leaf of masonry. This study explores the impact of corrosion on the integrity of these wall ties, emphasising their susceptibility to failure during extreme events. Existing literature highlights tension failure in a veneer wall is the result of nail pull-out from the timber. In the current research, accelerated corrosion of an R2 (Z600) wall tie reveals that tensile strength reduction is due to decreasing tie cross section from corrosion, leading to wall tie fracture rather than nail pull-out. Understanding these failure mechanisms is crucial for building assessment and monitoring strategies for masonry structures, especially in regions prone to extreme wind or seismic activity in combination with corrosion susceptibility, such as coastal environments.

ABSTRACT This study investigates the shear strength prediction of Fibre-Reinforced Concrete (FRC) beams reinforced with Fibre-Reinforced Polymer (FRP) bars and without stirrups through the application of Machine Learning (ML) techniques. The utilisation of FRP bars, particularly Glass Fibre-Reinforced Polymer (GFRP) and Basalt Fibre-Reinforced Polymer (BFRP) bars, has emerged as a promising alternative to traditional steel reinforcement due to their superior mechanical properties and corrosion resistance. Moreover, the incorporation of macro- and micro-discrete fibres into concrete compositions enhances both shear and flexural behaviour while reducing crack propagation induced by tensile stresses. The primary objective of this research is to develop accurate predictive models for the shear capacity of FRP-reinforced concrete beams, considering various influential parameters. Six different ML techniques, namely Multiple Linear Regression (MLR), Gaussian Process Regression (GPR), k-Nearest Neighbors (KNN), Support Vector Machines (SVMs), Artificial Neural Networks (ANNs) and Random Forest Regression (RFR), are employed to analyse the complex interactions between input variables, such as fibre type, bar diameter, concrete compressive strength, beam dimensions and the resulting shear strength. By leveraging these computational approaches, we aim to overcome the limitations of conventional analytical methods and provide robust predictions for structural design and optimisation.

ABSTRACT Bolted joint behaviour is a key parameter in predicting transmission tower performance. Various types of joints are based on the number of bolts and their configuration. However, a few types of these joints were tested or modelled. In the present study, the load-deformation response of transmission tower joints as a joint behaviour was predicted using a simplified numerical model. Then, available experimental load-deformation responses of joints were used to verify the results of the proposed model. In the last step, the joint behaviours of a 400 kV transmission tower were predicted with the proposed numerical model. Then, the evaluation of the tower’s response was done with a numerical model in ABAQUS under testing loading conditions. Lastly, the deformation of a full-scale tested tower was compared with the numerical results. The numerical model results show a good agreement with the experimental results. The ultimate strength and its corresponding displacement at the full-scale model are predicted with an error of about 4%. Moreover, the failure mode of the transmission tower was not affected by the behaviour of the joints.

ABSTRACT Bridge abutments are often damaged by girder impacts during major earthquakes. Very limited studies have been conducted. None of the past studies have incorporated abutment damage as an integrated system, i.e. the interaction between the deck and the back wall as well as between abutment and backfill. First, the reliability of the numerical model for damage assessment is validated with the result obtained from the shaking table test. Second, numerical simulations of the impact effect were carried out on four abutments with different shapes and dimensions of wing wall. The developed numerical models can simulate the nonlinear backfill soil, the backfill-back wall interface, and damage to reinforced concrete with the strain rate effect of the concrete and steel reinforcement. Parametric studies were conducted on the influence of the nonlinearity of the backfill soil, back wall-to-backfill friction, constitutive law of concrete, hourglass ratio, and impact energy. The results show that the nonlinear behaviour of the backfill soil and wing wall plays a significant role in the impact force on the back wall behaviour. Since poundings can be repetitive, this study confirms that the velocity of the initial impact of a bridge deck can precisely predict the severity of abutment damage.

ABSTRACT Concrete production faces challenges due to the depletion of natural sand and the need for more sustainable practices. This study investigates the use of sugarcane bagasse ash (SCBA) and recycled polyethylene terephthalate (RPET) as partial replacements for cement and sand, respectively. SCBA was tested as a 5%, 10%, and 15% replacement by weight of cement, while RPET was used as a 5%, 10%, 15%, and 20% substitute for sand by volume. Concrete samples were cured in water for 7, 28, and 56 days. The mix with 5% SCBA and 10% RPET showed comparable compressive strength to conventional concrete and improved split tensile strength by 1.2% and 11.61% at 28 and 56 days, respectively. The compressive strength-to-weight ratio of this blend was less than 3% lower than conventional concrete. This combination also maintained similar water absorption and fire resistance characteristics. These results suggest that 5% SCBA and 10% RPET are effective in enhancing the sustainability of concrete while maintaining structural performance, contributing to more environmentally friendly construction practices.

ABSTRACT Due to the advantages of Laplace domain in both time and frequency domains, the dynamic analysis and control tools in engineering software like MATLAB and Python have been designed based on it. Dynamic analysis of structures requires determination of the overall transfer matrix, which is obtained by multiplying the structure's transfer matrix (TM) with the load TM. With the input vector of unit intensity white-noise processes and the overall TM, the structural responses can be obtained. Furthermore, having the load TM is crucial for implementation of active control systems. In this article, the TM of along-wind loads was estimated for a tall building using the proper orthogonal decomposition (POD) method and the genetic algorithm (GA). To evaluate the effectiveness of the proposed approach, an example of a tall building was provided. The wind load cross-power spectral matrix (XPSD) was decomposed using POD technique, followed by the truncation of higher loading modes. Subsequently, the loading TM was derived by estimating the target non-linear functions with linear transfer functions through GA technique. Then, the responses of the structure were computed using the loading TM. The results demonstrated the efficacy of the proposed method in acquiring the loading TM and predicting wind-induced responses.

ABSTRACT The research focuses on optimising the mix design of ultra high-performance geopolymer mortar by employing the Taguchi method’s orthogonal array parameters through a systematic experimental approach. Utilising an L9 orthogonal array, the investigation was structured into two phases, each examining a distinct set of variables across three levels to ascertain their impact on compressive strength. The optimal mix was characterised by a water to binder ratio of 0.28, a fibre volume of 3%, a silicon carbide to binder ratio of 0, and a superplasticizer to binder ratio of 2%. This mix achieved 126 MPa of compressive strength.

ABSTRACT Not counting domestic dwellings, it has been estimated that some tens of thousands of older masonry buildings and structures exist nationally and that many of these are potentially at risk of partial (or worse) collapse from falling or dislodged masonry. This has significant implications for building owners, managers, insurers, the local and national economies, and the urban environment. The problem is caused mainly by the slow deterioration of masonry under atmospheric and other environments and by the corrosion of so-called wall-ties, relatively thin pieces of steel that tie the outer leaf of masonry walls to the inner leaf. The problem is likely to be particularly severe for scenarios such as synoptic windstorms and earthquake events as this causes area-wide damage, and potential wide-spread loss of human life – losses that could be prevented by timely intervention. The present paper deals with the research framework and the methodology being employed in a long-term project to develop tools for cost-effective structural masonry assessment and for risk estimation under structural deterioration conditions. Some early findings with potential immediate practical implications are given. Because the effects of deterioration are long-term, the overall project outcomes will take some years to come to fruition. They will be reported in due course.

ABSTRACT Sustainable concrete construction can be achieved by combining optimised structural designs with low-carbon concrete (LCC). This paper demonstrates the importance of sustainable construction by analysing various design options for a typical suspended slab system in high-rise buildings. Pearson (2020) noted that concrete slabs make up approximately 47% of the embodied carbon (EC) in commercial and residential structures, with slabs alone comprising around 70% of the total concrete volume in residential buildings. This presents an opportunity to reduce EC through structural design choices. The analysis in this paper involved designing a post-tensioned (PT) flat slab system for a residential development in Sydney and then re-designing it as a reinforced concrete (RC) slab by adjusting slab thickness and reinforcement system. A key finding was that transitioning from an RC to a PT slab resulted in a 44% total EC reduction when using a 100% General Purpose Cement (GPC) blend. Further EC reductions can be achieved by implementing LCC. The chosen LCC blend for this study is 23% Fly Ash, 23% Ground Granulated Blast Furnace Slag, and 54% Cement (FA/GGBFS/GPC), demonstrating a 36% reduction in EC compared to a 100% GPC blend while maintaining acceptable workability, constructability, mechanical, and durability properties.