Production of steel-concrete composite columns for blast tests

Concrete columns with hollow-core sections find widespread application owing to their excellent structural efficiency and efficient material utilization. However, corrosion poses a challenge in concrete buildings with steel reinforcement. This paper explores the possibility of using glass fiber-reinforced polymer (GFRP) reinforcement as a non-corrosive and economically viable substitute for steel reinforcement in short square hollow concrete columns. Twelve hollow short columns were meticulously prepared in the laboratory experiments and subjected to pure axial compressive loads until failure. All columns featured a hollow square section with exterior dimensions of (180 × 180) mm and 900 mm height. The columns were categorized into four separate groups with different variables: steel and GFRP longitudinal reinforcement ratio, hollow ratio, spacing between ties, and reinforcement type. The experimental findings point to the compressive participation of longitudinal GFRP bars, estimated to be approximately 35% of the tensile strength of GFRP bars. Notably, increasing GFRP longitudinal reinforcement significantly improved the ultimate load capability of hollow square GFRP column specimens. Specifically, elevating the ratio of GFRP reinforcement from 1.46% to 2.9%, 3.29%, 4.9%, and 5.85% resulted in axial load capacity improvements of 32.3%, 43.9%, 60.5%, and 71.7%, respectively. Specifically, the GFRP specimens showed a decrease in capacity of 13.1%, 9.2%, and 9.4%, respectively. Notably, the load contribution of steel reinforcement to GFRP reinforcement (with similar sectional areas) was from approximately three to four times the axial peak load, highlighting the greater load participation of steel reinforcement due to its higher elastic modulus. In addition, the numerical modeling and analysis conducted using ABAQUS/CAE 2019 software exhibited strong concordance with experimental findings concerning failure modes and capacity to carry axial loads.

Polyurethane mixtures are regarded as novel polymer pavement materials that can overcome the shortcomings of poor mechanical properties and loose particles of open-graded friction course (OGFC). Owing to its high strength after curing, polyurethane binder improves the mechanical connection at the aggregate-aggregate contact point, which effectively enhances the service performance of permeable pavement. However, the relationship between the binder content and the mechanical and functional properties of polyurethane mixture has not clearly understood yet. The objective of this study is to investigate the influence of the binder-aggregate ratio on the mechanical and functional properties using laboratory tests. Firstly, the effect of binder content on the mechanical properties of the mixture is examined by Marshall stability test, uniaxial compression test, and bending beam test. Secondly, the functional properties of the mixtures are characterised by Cantabro test, permeability test, computed tomography, and particle clogging test. Finally, the durability of the mixtures is characterised by hydrolysis resistance test and ultraviolet radiation degradation test. The results reveal that the content of binder has a significant impact on the mechanical and functional properties of the mixture. It is necessary to maintain a balance between the mechanical and functional properties.

3D-printed steel reinforcement for digital concrete construction – Manufacture, mechanical properties and bond behaviour

ABSTRACTPavement skid resistance plays a key role in traffic safety. Meanwhile, tire-pavement noise is a major source of traffic noise in urban areas. Current asphalt mixture design methods, however, mostly focus on volumetric and mechanical properties and pay little attention to the skid resistance and noise reduction performance of asphalt mixtures, which are significantly affected by the surface textures of asphalt mixtures. Incorporating the evaluation of surface texture into the mixture design would aid in a more rational selection of materials considering both mechanical and functional properties of asphalt mixtures. In this paper, the surface texture properties of several types of asphalt mixtures are measured using a recently developed 2-Dimensional Image Texture Analysis Method. A prediction model correlating the mixture surface texture levels at different central texture wavelength in octave band with the important mix design parameters is established using a multivariate non-linear regression analysis. The model is validated through laboratory test and imaging measurement indicating its capability of predicting the level and distributions of mixture surface texture. The prediction model is anticipated to provide a basis of optimised mixture design considering the skid resistance and noise reduction performances of asphalt pavement.

This study investigates the blast resistance of reinforced concrete (RC) shear walls reinforced with hybrid configurations of traditional steel rebars and advanced fiber-reinforced polymers (FRPs), including carbon fiber reinforced polymer (CFRP), glass fiber reinforced polymer (GFRP), and basalt fiber reinforced polymer (BFRP). A validated finite element analysis (FEA) model was used to evaluate ten reinforcement configurations subjected to central contact explosive loads. RC shear walls measuring 2100 mm × 2800 mm × 300 mm were analyzed based on displacement, surface damage, and energy absorption. Configurations fully reinforced with CFRP demonstrated the highest blast resistance, effectively minimizing displacement and surface damage due to CFRP's superior stiffness and tensile strength. BFRP configurations exhibited higher energy dissipation but resulted in increased deformation and damage, while GFRP configurations provided intermediate performance, balancing stiffness and flexibility. Hybrid configurations combining steel and FRPs offered an effective compromise by optimizing energy absorption, structural integrity, and cost-effectiveness. These findings highlight CFRP as the optimal material for high-impact applications, while hybrid and material-specific reinforcements provide adapted solutions for moderate resistance requirements or environmental constraints. This study emphasizes the importance of material selection and reinforcement strategies in the design of durable, blast-resistant RC structures.

Nondestructive detection and monitoring of stress in concrete structural members is highly coveted. Yet, there are still no efficient techniques capable of achieving that goal. The leading approach towards this goal has been based on acoustoelasticity, the relationship between mechanical properties, such as mechanical wave speed, and the stress state of the solid medium. In concrete materials, acoustoelasticity has been increasingly studied, mainly using wave propagation phenomena, and usually in small samples of plain concrete — without steel reinforcement — axially loaded. A less studied approach involves the use of resonance phenomena, which offers other benefits. In this study, we tested a real-size reinforced concrete column of cross section 20 cm × 20 cm and 2 m long, by applying three cycles of controlled compressive axial load, varying from 0 to 4 MPa, and measuring axial strains and torsional frequencies of vibration. Repeatable results show that the frequencies of vibration and applied compression are positively correlated. indicating a dominant elastic behavior. This study is an important step forward on the path to understanding and implementing a nondestructive technique for stress monitoring of real concrete structures.

Reinforcement mechanism of orientally distributed steel fibers on ultra-high-performance concrete

Design and analyses of porous concrete for safety applications

Purpose. Study of the effect of sodium phosphate additives on the properties of a reversible sand-clay mixture in the green and dry state to improve the quality of castings from iron-carbon and aluminum alloys. Research methods. A reversible molding mixture based on quartz sand and kaolin clay was used. The effect of three additives (sodium tripolyphosphate, sodium hexametaphosphate, sodium pyrophosphate) in amounts from 0.5 to 2.0% was studied. Properties of mixture were determined using standard methods: clay component content, strength, gas permeability, crumbleness, flowability, formability, packing. Results. Effective additives have been studied to ensure the possibility of multiple use of reversible molding sand-clay mixtures. Special attention is paid to the regulation of the properties of the mixture in the dry state, since this issue has been much less researched today. For this purpose, sodium phosphates, which are produced by the chemical industry in sufficient quantities, were used for the first time. As materials that affect the properties of the mixture as a whole, they have not been considered before. Scientific novelty. For the first time, the positive effect of sodium phosphate additives on the physical and mechanical properties such as strength and crumbleness of reversible sand-clay mixtures was established. This effect is manifested in the fact that additives contribute to a slight improvement of properties of the green mixture and a very significant improvement of these properties of the dry mixture. There is practically no effect on important technological properties (flowability, formability, packing). Practical value. Based on the results of the experiments, it is recommended to use sodium tripolyphosphate or hexametaphosphate additives in the amount of 0.5 to 1.0 % to significantly improve the properties of dry sand-clay foundry molds. The use of these additives eliminates the appearance of surface defects in cast parts from aluminum and iron-carbon alloys.

This study investigates the structural performance of reinforced concrete (RC) columns reinforced with hybrid Steel-FRP Composite Bars (SFCBs), offering a sustainable alternative to conventional steel and fiber-reinforced polymer (FRP) reinforcement. Eight large-scale RC columns, measuring 400 × 400 mm in cross-section and 1850 mm in height, were tested under combined cyclic and axial loading to simulate seismic conditions. The experimental variables included SFCB diameters (14 mm, 18 mm, 22 mm), axial load ratios (20%, 30%, 40%), and stirrup spacing (80 mm, 100 mm, 150 mm). The results indicate that SFCBs can effectively replace traditional steel reinforcement, providing comparable load-bearing capacity while significantly improving durability. Columns reinforced with SFCBs demonstrated superior initial stiffness and achieved higher drift ratios than steel-reinforced columns, exceeding the limits set by international design codes (ACI 440.2R, CSA S806-12, Eurocode 8) with maximum drift ratios of up to 6.5%. Increasing the SFCB diameter from 14 mm to 22 mm enhanced peak load capacity by 14%–20% and improved drift ratios by up to 113%. However, higher axial load ratios and wider stirrup spacing were found to reduce ductility. Specifically, increasing the axial load ratio from 20% to 40% decreased ductility by 13.46%, while increasing stirrup spacing from 80 mm to 150 mm reduced ductility by 8.90%. These findings underscore the potential of SFCBs to enhance the performance of RC columns in seismic and corrosive environments, offering a durable and sustainable solution for modern infrastructure. To the authors' knowledge, this study represents the first comprehensive investigation into the behavior of SFCB-reinforced RC columns under combined cyclic and axial loading, providing valuable insights for the design of resilient concrete structures.

Potassium sodium niobate (KNN)‐based piezoelectric ceramics have emerged as a promising alternative to lead‐based systems due to their exceptional properties. While extensive research has focused on improving the electrical properties of KNN‐based ceramics through doping and processing optimization, the concurrent investigation of their mechanical properties has been lacking. This study presents a comprehensive analysis of the mechanical and electrical properties of KNN‐based lead‐free piezoceramics doped with various transition metal oxides and rare earth oxides, based on substantial experimental data. Our findings reveal that the as‐sintered KNN‐based ceramics exhibit not only outstanding electrical properties but also remarkable mechanical robustness compared to conventional toughened lead zirconate titanate (PZT)‐based ceramics. These exceptional electrical and mechanical properties are attributed to the micro‐scale and atomic‐scale structure of the modified KNN‐based ceramics, characterized by a highly condensed structure, an inhomogeneous distribution of nano‐domain structure, and the presence of amorphous intergranular films at grain boundaries.

Dynamic behavior of axially loaded masonry walls strengthened with different innovative techniques under explosion loading

Hollow concrete columns are often employed in bridge constructions because of their lighter weight and effective section characteristics. In addition, to reduce the issue of steel reinforcement corrosion and create a strong and light construction, hollow section columns are also reinforced with bars made of fiber-reinforced polymer. This research aimed to analyze the effect of GFRP (glass fiber reinforced polymer) on the compression strength of hollow square concrete columns under an axial concentric load. The finite element application ABAQUS 2019 version was used to simulate a finite element model, calibrated utilizing experimental data from previous studies for various geometric models of concrete and material specifications of the reinforcement. The findings of the experimental studies and the finite element model exhibit excellent agreement. Finally, according to the parametric study's results, A parametric analysis is done to assess the impact of changing reinforcement ratio, spacing between the ties, inner-to-outer section width ratio, and a comparison with steel reinforcement. The computational results clearly show how an Increased longitudinal GFRP reinforcement ratio improves the columns' bearing capability, but when compared to steel reinforcement, it provides less bearing capability. For the optimum outcome with hollow square concrete columns, it is advised to adopt the limit of the i/o between 0.27 and 0.38. In addition, changing the spacing between stirrups was shown not to significantly impact the capacity for axial load in hollow square concrete columns.

The purpose of this study is to investigate the effect of different reinforcement strategies on the mechanical properties of pulverized glass waste (PGW) reinforced AA6061-T6 friction stir welded joint. Friction stir welding of PGW reinforced AA6061-T6 was carried out at an optimized processing parameters by using different reinforcement strategies including centre groove, parallel holes, centre holes, zig-zag holes and side holes arrangements. Thereafter, the microstructure and mechanical properties of weldments produced using each strategy were investigated. The results showed that all the reinforcement strategies utilized in this work produced harder joints than the unreinforced joint. The parallel holes (PH) strategy followed by the centre holes (CH) exhibited the highest hardness of 72 HRCB and 66 HRCB respectively. Only the joints produced using PH, CH and SH strategies exhibited higher or improved impact energy than the unreinforced. Though the joints produced using PH and CH reinforcement strategies have tensile properties that are close to that of the unreinforced joints, the unreinforced joints show higher tensile properties than the entire reinforced joints. Compared with other reinforcement strategies, better particle distribution was achieved through the use of PH and CH reinforcement strategies. Parallel holes and centre holes arrangements have been established as the most appropriate reinforcement strategies for producing high quality aluminium alloy composite welded joints.

Conventional glass-ionomer materials: A review of the developments in glass powder, polyacid liquid and the strategies of reinforcement