ABSTRACT This study numerically investigates the seismic behavior of beam-to-column connections with Reduced Beam Section (RBS) and variable stiffener configurations in box columns. Six models with varying stiffener thicknesses (10-25 mm) and heights (400-600 mm) were analyzed using the AISC 341-16 protocol. The reference model was validated against experimental data, showing a 6.4% difference in maximum moment. Parametric analysis revealed that increasing stiffener thickness enhanced maximum moment by 8.3%, initial stiffness by 8.5%, and energy dissipation by 18%, but reduced ductility. Conversely, increasing stiffener height improved ductility by 6.6% and energy dissipation by 5.9%. Panel zone stresses exceeded the yield strength (355 MPa) in models with intermediate stiffener thicknesses, while thicker stiffeners maintained stresses below this limit. These findings underscore the need to optimize stiffener design to balance moment capacity, energy dissipation, and ductility in RBS connections for seismic applications.

ABSTRACT Marine environments subject the longevity of concrete structures to extreme conditions, and hence, sophisticated reinforcement techniques have to be adopted to combat corrosion and extend service life. The current study investigates the adhesion properties between Carbon Fiber Reinforced Polymer (CFRP) rebars and aluminium oxide (Al₂O₃) nanoparticle-reinforced concrete and contrasts them with steel rebars. Mechanical performances of the concrete reinforced by nanoparticles were tested by experiments and predicted by nonlinear finite element analysis with ABAQUS software to simulate the adhesion mechanism using a separation-slip model. Experimental pullout tests validated the finite element model, and results indicated that addition of 0.25% and 0.5% Al₂O₃ nanoparticles improved the tensile strength of GFRP rebars by 118.5% and 134.7%, respectively, compared with standard concrete. The study of various parameters, including nanoparticle content and rebar diameter, revealed distinct CFRP and steel rebar adhesion behaviours. Steel rebars exhibited greater pullout forces with more excellent mechanical adhesion, while greater CFRP rebar diameters increased chemical bonding and significantly improved pullout forces. The results highlight the ability of Al₂O₃ nanoparticles to enhance bond strengthening and optimise the performance of concrete structures under corrosive conditions. The study provides valuable guidelines for the construction of durable and sustainable reinforced concrete structures, particularly for marine environments.

ABSTRACT The time-domain method plays a significant role in structural wind-induced vibration analysis. The conventional approach typically involves three key steps: wind field simulation, dynamic vibration response calculation, and statistical analysis of the response. However, dynamic response analysis often relies on approximate methods and demands substantial computational effort. To address this limitation, this paper proposes a simplified closed-form approach, which significantly enhances the computational efficiency while maintaining accuracy. The core idea leverages the principle that the response of a harmonic input through a linear system remains harmonic. By exploiting this property, the solution for a linear system subjected to trigonometric excitation can be derived analytically, bypassing the need for the numerical integration of the vibration equations, which ensures both precision and efficiency. Furthermore, the Fast Fourier Transform (FFT) technique is employed to efficiently compute the structural response for a sum of trigonometric functions, drastically reducing the computational time. To demonstrate the method’s effectiveness, the along-wind vibration response of a 45 m transmission tower is analysed in the time domain. The proposed approach is validated against frequency-domain analysis and traditional time-domain methods. Results confirm that the method is computationally efficient and accurate, particularly for structures with a high number of degrees of freedom.

ABSTRACT Textile-reinforced concrete (TRC) is a composite material consisting of high-strength mortar and continuous textiles that can form a slender member. In normal concrete, a discrete short fibre can be incorporated to increase its performance under tensile force while improving its ductility under bending. This research investigated the effect of incorporating natural kenaf fibre into TRC to improve its tensile strength and ductility. The tensile and flexural strengths of TRC with and without kenaf fibre were investigated, having either single or two layers of carbon textile mesh. It was found that mortar with 2% kenaf fibres treated with NaOH solution yields the highest compressive strength of 52.0 MPa, well beyond the target strength of 40 MPa. The addition of short fibre increases the tensile strength of a single-layer TRC without fibre, while minimal strength improvement was observed in two-layer TRC. The addition of kenaf fibre did not improve the overall behaviour of TRC under flexure. However, the ultimate flexural capacity and ductility increased when the kenaf fibre was added to TRC. Generally, short kenaf fibre can be incorporated into TRC where tensile strength is required; however, the number of textile layers will control the improvement in strength.

ABSTRACT This paper presents the results of the seismic analysis of the towers of the Faith Sultan Mehmet (FSM) Suspension Bridge in Istanbul, Turkey. A three-dimensional (3D) model of the entire bridge and a 3D finite element model of the towers were initially created. The results of the free vibration analysis showed good agreement with the available measured data of the ambient vibration. The seismic performance of the bridge and its towers was assessed using 3D non-linear finite element time-history analysis and non-linear static analysis in Abaqus. The 3D finite element model of the tower was modelled using shell and beam elements. The shear force at the base of the towers in response to seismic forces was calculated and compared with results of previous studies. The base shear force obtained using shell elements was less than that obtained using beam elements, revealing the advantage of the use of shell elements over beam elements. The results of this investigation show that, when modelling the FSM Bridge towers with shell elements, although the maximum resistance of the structure decreased compared to modelling with beam elements, the bridge towers showed satisfactory and acceptable performance against earthquake loads in pushover analysis.

ABSTRACT Currently, cup-headed bolts are not referenced in the Australian Timber Design Standard (AS 1720.1), despite their widespread use in timber construction. This study aims to compare cup-headed bolts (CHBs) and hex-headed bolts (HHBs) in terms of their practical applications and structural capacity in timber post-to-beam connections through a combination of industry surveys and experimental testing. A questionnaire was conducted to assess builders’ perceptions regarding the differences and similarities between the two bolt types. The respondents, with an average industry experience of 30 years, overwhelmingly preferred cup-headed bolts for timber post-to-beam connections, with the majority viewing them as interchangeable with hex-headed bolts. These survey findings informed the experimental phase, where selected joint configurations were tested under tension, compression, and pullout loads. The results revealed that in tensile and compressive tests, cup-headed bolts exhibited higher joint capacity than hex-headed bolts, with no significant difference in failure modes between the two. In pullout tests, no substantial performance difference was observed. Given these findings, cup-headed bolts should be incorporated into the Australian Timber Design Standard, aligning regulatory guidelines with current industry practice while introducing no apparent structural drawbacks.

ABSTRACT Older bridges were designed and constructed with pre-1970 design guidelines with design shortcomings (e.g. shorter lap splices located in the potential plastic hinge zone at the bottom of the column, and inadequate lateral confinement). For older bridge columns, the potential of having a catastrophic collapse can only be assessed by conducting realistic simulations of deficient lap-spliced RC columns against seismic loading. This study proposes a numerical model to realistically simulate the nonlinear behaviour of bar-slip in circular lap-spliced RC columns through model calibration and regression and applies the model to existing older non-ductile bridges to assess their seismic vulnerability. An experimental database consisting of 17 circular specimens exhibiting lap-splice failure before yielding of longitudinal reinforcement is constructed and used to calibrate the proposed numerical model to optimise the model parameters. The proposed model correlates strongly with the existing experimental data. Fragility curves are developed to determine the seismic damage potential of non-ductile bridges. Single-frame concrete box-girder bridge models having two-span, three-span, and four-span with and without lap splices in the plastic hinge zone were selected. Fragility results indicate that the older bridges having deficient lap splices in RC columns in the plastic hinge zone have a higher probability of failure.

ABSTRACT To produce RA of good quality, this research proposed a new three-step processing method. First, soak the raw material in a moderate acetic acid solution. The second step is to grind the aggregate physically using an LA abrasion machine. Finally, the third step is to coat the aggregate with a cement silica fume slurry to seal any pores. There are seven distinct types of triple processed recycled aggregates (TPRAs): TPRA(0RVNs), TPRA(100RVNs), TPRA(200RVNs), TPRA(300RVNs), TPRA(400RVNs), TPRA(500RVNs), and TPRA(600RVNs). This study examined the effects of TPRAs by varying the amounts of TPRAs added to an M40 grade control mix in place of NA (0%, 20%, 40%, 60%, 80%, and 100%). Experiments were conducted to investigate the properties of TPRA-created concrete, including its workability, strength, and durability. Under conditions where TPRA (500 RVNs) replaces 60% of the NA in the mix, the compressive strength drops by 12.84%, but the RCPT value rises by 34%. This means that structural concrete should have TPRA (500 RVNs) replaced with 60% NA. Additionally, for the best results while making TPRA, it is recommended to soak it for 24 h in a moderate acetic acid solution, then run it through 500 revolutions per minute (RPM) on the LA abrasion machine. Finally, cover it with a layer of cement silica fume slurry.

ABSTRACT The study evaluates the mechanical performance of cementitious matrix-based strengthening composites through tensile and bond tests for masonry reinforcement. Two composite systems were tested: the first, a glass fabric embedded in a 1:3 cement mortar matrix (GF-RCM), and the second, short hybrid fibres in an engineered cementitious composite matrix (SF-ECC). Both systems were chosen for their potential to improve masonry’s tensile strength and bond properties. Experimental results indicated that both composites showed promising tensile and bond strengths, confirming their suitability for masonry strengthening. The GF-RCM composite outperformed the SF-ECC system, exhibiting significantly higher tensile and bond strengths. This enhanced performance is attributed to the strong interaction between the glass fabric reinforcement and the cement mortar matrix. Additionally, the GF-RCM composite proved to be more practical for field applications due to its simpler preparation and application process. The study highlights the effectiveness of the GF-RCM composite as an efficient and user-friendly solution for strengthening masonry structures, providing superior mechanical properties and ease of use. However, both composites demonstrate potential for various strengthening applications, depending on project-specific needs.

ABSTRACT This study utilises Exploratory 10.6, a coding-free machine learning (ML) platform, to predict the interface shear strength of concrete interfaces, offering a coding-free AutoML solution to a data-driven approach in structural engineering. A dataset of 200 push-off samples was analysed, incorporating six input parameters: volume fraction of steel fibres, concrete compressive strength, yield strength of interface reinforcement, strength ratio, interface shear reinforcement area, and interface shear plane area. The single output parameter is the interface shear strength. The study employed machine learning models, including XGBoost, decision tree (DT), random forest (RF), and linear regression (LR), to develop predictive models. XGBoost emerged as the most effective model, achieving an R2 of 0.924 and RMSE of 1.032, significantly outperforming traditional empirical models, such as those in AASHTO LRFD and ACI codes, which demonstrated poor generalisation across varying experimental conditions. The random forest and decision tree models achieved R2 values of 0.812 and 0.728, respectively, with RMSEs of 1.895 and 1.962, while the linear regression model showed the lowest performance with an R2 of 0.768 and an RMSE of 1.458. Data preprocessing techniques, including correlation plots and principal component analysis, highlighted strength ratio as the dominant factor influencing interface shear strength. This study also revealed that ML-based models performed better during training than testing, highlighting their reliance on training data. The findings underscore the superiority of advanced ML approaches, particularly XGBoost, over traditional empirical methods, and demonstrate the potential of coding-free platforms for enhancing predictive modelling in structural engineering.