This issue of Structures and Buildings contains six papers covering different interesting topics including bond properties of steel rebars, flexural strengthening of reinforced concrete (RC) beams, repairing of fire-damaged circular RC columns, seismic performance of a connection between concrete-filled steel columns and RC frames, optimal location of sensors for detecting rail damage, mechanical behaviour of fasteners in laminated bamboo lumber.
The bond characteristics of steel rebar embedded in cracked concrete have been experimentally and theoretically investigated by many researchers. However, there is still a lack of theories able to predict the effect of concrete workability on the bond capacity of steel rebar embedded in pre-cracked concrete. Following this need, in the first paper by Mousavi et al. (2024), an experimental champaign considering both normal and self-consolidating concretes is presented. The obtained experimental results show that initial crack widths larger than 0.10 mm have a significant influence on bond properties and concrete mixtures with higher workability are less sensitive to the pre-cracking phenomenon than normal concrete mixtures.
The second and the third papers regard the rehabilitation of RC beams and fire-damaged RC columns using fibre-reinforced polymers. Chhorn et al. (2024) conduct experimental tests on four RC beams strengthened using different basalt-fibre-reinforced polymers (BFRP) reinforcement techniques. Three-dimensional finite-element (FE) models are implemented in Abaqus to simulate the response of RC beams strengthened with BFRP plates. The obtained experimental and numerical results show the effectiveness of the proposed technology to improve the flexural resistance of RC beams. In the next paper, Hussain et al. (2024) investigate the response of fire-damaged circular RC columns repaired using different confinement techniques. The use of carbon-fibre-reinforced polymers (CFRP) is compared to steel wire mesh, filled with cement–sand mortar and wrapped with CFRP. Undamaged, fire damaged and repaired fire-damaged circular RC columns are experimentally tested at room temperature under uniaxial compression until failure. Non-linear FE models are implemented in Abaqus and validated based on the experimental results. Data obtained from 168 models are used to develop regression equations for the prediction of the performance of repaired RC columns. The proposed numerical and analytical models show a good capacity to predict the post-fire performance of damaged and repaired RC columns.
Concrete filled steel tube (CFST) technology has been widely used in civil engineering structures providing numerous structural benefits including the confinement of the concrete core and the easy and quick construction method. In the fourth paper, Dai et al. (2024) investigate the seismic response of a connection system between CFST columns and RC frames. The monotonic and cyclic experimental tests on two specimens and a comprehensive parametric analysis performed using a FE model calibrated based on the experimental results are introduced. The analyses show that the use of a higher concrete strength would be most effective at elevating the ultimate strength and initial stiffness of the connection system, while changes in the axial compressive force ratio have larger impacts on stiffness degradation than on ultimate strength.
Health monitoring plays an important role for reducing the risk in rail track maintenance. Acoustic emission (AE) techniques are considered a reliable way to detect the rail defects. The optimum location of AE sensors is important for improving the defects detection and reducing the related costs. Kundu et al. (2024) introduce the results of an experimental test to investigate the optimum placement of a single sensor on a rail section. The crack is simulated through a pencil lead break and the obtained signal analysed using wavelet transformation to establish a relationship with the group velocity and to localise the simulated crack.
Bamboo is becoming a popular alternative to traditional building materials, due to its sustainability, durability, and good mechanical performance. In the concluding paper of this issue, Chen et al. (2024) present experimental research on the effect of shank diameter, shank type, penetration depth and insertion direction on the nail-holding behaviour of laminated bamboo lumber (LBL). It is found that the withdrawal resistance of nails/screws in the LBL members increases with an increase in fastener diameter and penetration depth. The theoretical models available in literature are compared to the experimental load-slips curves to identify the most suitable one.
We thank all the Authors, Reviewers and Readers and we welcome discussion on any of these papers.
