The dynamic properties of concrete structures after being exposed to high temperatures play a crucial role in post-disaster repair and accident prevention measures. This study examined three different mixture ratios of Steel Fiber Reinforced Concrete (SFRC) with matrix strength of C60 and steel fiber contents of 0%, 1%, and 2%. A Split Hopkinson Pressure Bar (SHPB) with a diameter of 75 mm, along with a heating furnace, was employed to comprehensively investigate the dynamic compression behavior of materials. The specimens were exposed to temperatures ranging from 200 °C to 600 °C. In addition to evaluating the extent of mechanical degradation in SFRC after cooling, auxiliary impact experiments were also carried out at ambient temperature. The experimental data revealed that the dynamic peak stress and peak strain initially increased but eventually decreased as the loading rates continued to rise. The degree of strengthening, toughening, and energy absorption capacity of concrete materials progressively decreased as the escalation of strain rate after the cooling process. Moreover, the inclusion of steel fibers proved effective in preventing cracking and damage to the concrete, preserving the integrity of specimens even at higher temperatures. Simultaneously, the residual stress and deformation capacity of SFRC showed considerable enhancement after exposure to elevated temperatures.
The performance of asphalt mixtures greatly influences the long-term performance of bridge deck pavements. It is essential to optimise the asphalt mixtures with the best overall performance according to different regional conditions for use in engineering practice. This study proposes a comprehensive assessment method based on the Analytical Hierarchy Process (AHP) and Fuzzy Comprehensive Evaluation (FCE) to evaluate the serviceability of asphalt mixtures from different perspectives. It is used to optimise the best asphalt mixtures. The results show that the skeleton-dense structure asphalt mixture has better engineering applicability than the suspension-dense structure asphalt mixture, and the comprehensive performance of the asphalt mixture decreases with the increase of the nominal maximum particle size. The FCE determines that the total performance of the seven types of asphalt mixtures in the order of their superiority and inferiority are SMA-13 >asphalt mastic sand (AMS)>SMA-10 >AC-25 >AC-13 >AC-16 >AC-20. The study combines qualitative and quantitative factors, which makes the selection of engineering materials more scientific and rigorous and improves the rationality of material suitability evaluation.
Due to the environmental concerns, the application of natural FRPs to replace synthetic fibre as a strengthening material has increased. Kenaf fibre-reinforced polymer (KFRP) has comparable specific strength with glass fibre-reinforced polymer (GFRP). Moreover, epoxy resin is widely used as a matrix of composites and adhesives; however, it has low shear strength. Improvement of epoxy properties is therefore required, for example, by incorporating biofiller such as eggshells from household waste, which contain calcite, to improve its shear strength. Testing series includes variations of KFRP bond length, KFRP thickness and eggshell filler volume fractions. All the DSJ specimens underwent a two-stage testing process, experimentally and numerically. In Stage 1, experimental work was performed on the specimens through quasi-static tensile tests, following the ASTM D3528–96. In Stage 2, numerical studies were conducted to predict the strength using the extended finite element method (XFEM) within ABAQUS CAE. Subsequently, the strength prediction from developed 2-D FEA models was validated by the experimental datasets. All testing specimens exhibited KFRP rupture mode. For all the studied overlap lengths, the joint strength increased with the increase of the studied composite`s adherend thickness (1 - 4 mm); however, the overlap length reached the optimum at the overlap length of 80 mm, where beyond that overlap length, the joint strength tended to decrease. The maximum joint strength is achieved with a combination of 80 mm bond length and 4 mm KFRP thickness, resulting in a 226.5% enhancement compared to the baseline (composite thickness of 1 mm, with adhesive without filler). Moreover, it was found that volume fraction of 5% eggshell was the optimum. The strength prediction was performed using an extended finite element method (XFEM), In general, there were good agreements in both experimental datasets and XFEM models, with discrepancies of less than 16.1% (averaging less than 8%). The FEA modelling approaches are promising for predicting the joint strength of KFRP/steel DSJ.
