Flexural Loading Research Articles

One Billion Years of Stability in the North American Midcontinent Following Two‐Stage Grenvillian Structural Inversion

AbstractThe North American craton interior preserves a >1 Ga history of near surface processes that inform ongoing debates regarding timing and drivers of continental‐scale deformation and erosion associated with far‐field orogenesis. We tested various models of structural inversion on a major segment of the Midcontinent Rift along the Douglas Fault (DF) in northern Wisconsin, which accommodated ≳10 km of total vertical displacement. U‐Pb detrital zircon and vein calcite Δ47/U‐Pb thermochronometry from the hanging wall constrain the majority of uplift (≳8.5 km) and deformation to 1052–1036 Ma during the Ottawan phase of the Grenvillian orogeny. Combined U‐Pb zircon dates, Δ47/U‐Pb calcite thermochronometry, and field data that document syn‐ to early post‐depositional deformation in the footwall constrain a second stage of uplift (1–1.5 km) ca. 995–980 Ma during the Rigolet phase of the Grenvillian orogeny. A minor phase of Appalachian far‐field orogenesis is associated with minimal thrust reactivation. Our combined analyses identified the 995–980 Ma Bayfield Group as a Grenvillian foreland basin with an original thickness 0.5–2 km greater than currently preserved. By quantifying flexural loading and other subsidence mechanisms along the Douglas Fault, we identify dynamic subsidence as a mechanism that could be consistent with the development of late‐Grenvillian transcontinental fluvial systems. Minimal post‐Grenvillian erosion (0.5–2 km) in this part of the craton interior has preserved the Bayfield Group and equivalent successions, limiting the magnitude of regional erosion that can be attributed to Neoproterozoic glaciation.

Effect of using normal concrete or recycled concrete layer on behavior of repaired projectile bullet damaged reinforced concrete beams

AbstractThis study utilized experimental research to investigate the efficiency of using normal aggregate concrete (NAC) or recycled aggregate concrete (RAC) as a new concrete layer for repairing projectile bullet damage to strengthening reinforced concrete (RC) beams. This study comprised the construction and testing of eight RC beams made of RAC and NAC. They are initially subjected to projectile bullets and after that tested with flexure load to evaluate the effect of using RAC and NAC that was investigated. The findings of test results demonstrate that the repaired specimens with RAC or NAC experienced a higher load capacity than the damaged control specimens. As such, this approach could potentially use to restore RAC or NAC beams were previously damaged by projectile bullets. In addition, the findings of this research indicate that the load capacity of the damaged RC beams that were previously repaired using the NAC layer was higher than the load capacity of the damaged RC beams that were repaired using the RAC layer. The load capacity enhanced significantly of (106%–118%) and (104%–113%), respectively, when NAC and RAC are utilized in repairs. Therefore, using either NAC or RAC concrete is more economical, environmentally friendly, and efficient than demolishing.

Production of rubberized concrete utilizing reclaimed asphalt pavement aggregates and recycled tire steel fibers

The integration of waste tire elements into concrete, specifically granular rubber and discrete steel fibers, signifies a substantial advance in the pursuit of sustainable alternatives for rigid concrete pavements. This incorporation not only improves the ductility of rigid concrete pavements, but also augments their energy absorption capabilities. Similarly, replacing natural aggregates in concrete with reclaimed asphalt pavement (RAP) aggregates makes a large contribution to the reduction of negative environmental impacts, while conserving natural resources from depletion. This investigation explores the potential application of recycled rubber particles from waste tires (WTRR) and RAP aggregates as partial substitutes for natural fine aggregates, and evaluates their impact on the performance of rigid concrete pavements. Eight mixes were cast, each with two variables: (i) fine aggregate type (fine rubber (FRu) aggregates, fine asphalt (FAs) aggregates, and combinations of both types of aggregate) replacing 50 % of the natural fine aggregate; and (ii) waste tire recycled steel fibers (WTRSF) content (0 and 40 kg/m3). The axial compressive stress–strain, flexural load–deflection, and direct shear strength behaviors, together with the dry unit weight and volume of permeable voids for all concrete mixes were investigated and compared. The results show that, although the flexural and shear strengths decrease with the inclusion of FRu and/or FAs, the use of WTRSF noticeably mitigates the losses in strength that arise from the use of WTRR and/or RAP aggregates alone. The inclusion of WTRSF enhances the strain capacity of the concrete and allows the development of adequate post-peak energy absorption capacity in flexural and shear loading. Additionally, the dry unit weight of the proposed composites decreased by as much as 8 %, and their volume of permeable voids lies within the limits of high-durability concrete mixes (9–12 %). Hence, the proposed sustainable concrete composites are promising composites for rigid concrete pavement construction.

Efficacy of PZT Sensors Network Different Configurations in Damage Detection of Fiber-Reinforced Concrete Prisms under Repeated Loading.

Real-time structural health monitoring (SHM) and accurate diagnosis of imminent damage are critical to ensure the structural safety of conventional reinforced concrete (RC) and fiber-reinforced concrete (FRC) structures. Implementations of a piezoelectric lead zirconate titanate (PZT) sensor network in the critical areas of structural members can identify the damage level. This study uses a recently developed PZT-enabled Electro-Mechanical Impedance (EMI)-based, real-time, wireless, and portable SHM and damage detection system in prismatic specimens subjected to flexural repeated loading plain concrete (PC) and FRC. Furthermore, this research examined the efficacy of the proposed SHM methodology for FRC cracking identification of the specimens at various loading levels with different sensor layouts. Additionally, damage quantification using values of statistical damage indices is included. For this reason, the well-known conventional static metric of the Root Mean Square Deviation (RMSD) and the Mean Absolute Percentage Deviation (MAPD) were used and compared. This paper addresses a reliable monitoring experimental methodology in FRC to diagnose damage and predict the forthcoming flexural failure at early damage stages, such as at the onset of cracking. Test results indicated that damage assessment is successfully achieved using RMSD and MAPD indices of a strategically placed network of PZT sensors. Furthermore, the Upper Control Limit (UCL) index was adopted as a threshold for further sifting the scalar damage indices. Additionally, the proposed PZT-enable SHM method for prompt damage level is first established, providing the relationship between the voltage frequency response of the 32 PZT sensors and the crack propagation of the FRC prisms due to the step-by-step increased imposed load. In conclusion, damage diagnosis through continuous monitoring of PZTs responses of FRC due to flexural loading is a quantitative, reliable, and promising application.

The Influence and Mechanism of Curing Methods and Curing Age on the Mechanical Properties of Yellow River Sand Engineered Cementitious Composites.

This study investigates the potential use of Yellow River sand (YRS) sourced from the lower reaches of the Yellow River in China as a sustainable and cost-effective substitute for quartz sand in Engineered Cementitious Composites (ECC). With an annual accumulation of approximately 400 million tons in this region, YRS presents a substantial resource. ECC specimens with 100% YRS replacement with quartz sand were subjected to various curing methods: natural, steam, standard, and sprinkler. Extensive mechanical testing including flexural, compressive, uniaxial tensile, and four-point flexural tests was conducted. Additionally, Scanning Electron Microscope (SEM) and Mercury Intrusion Porosimetry (MIP) analyses investigated microscopic mechanisms influencing macroscopic mechanical properties. Finally, the mechanical properties of the YRS-ECC test block after 14 days of standard curing and the traditional sand ECC test block were compared and analyzed. The results indicate that ECC specimens with 100% YRS substitution under natural curing show an optimal ultimate tensile strain of more than 4%, providing the best resistance to the reduction in ultimate flexural load and deflection due to aging. Steam curing enhances flexural and compressive strength, achieving an ultimate flexural load of 5 kN and a maximum deflection of 4.42 mm at 90 days. SEM analysis revealed lower C-S-H gel density under natural curing and higher under steam curing, enhancing fiber pull-out in steam-cured specimens. The MIP tests demonstrated that natural curing had the highest porosity (32.86%) and average pore size (51.69 nm), whereas steam curing resulted in the smallest average pore size, with 44% of pores under 50 nm. Compared with traditional sand, it is found that the ultimate bending load and deflection of YRS-ECC are 5.7% and 9.4% higher than those of traditional sand ECC, respectively, and its ultimate tensile strength and strain are also improved. These findings highlight YRS as a sustainable alternative to natural sand in ECC, with natural curing proving the most effective for superior mechanical performance, including tensile strain, crack resistance, and durability.

Flexural behavior of coral aggregate concrete beams reinforced with BFRP bars under seawater corrosion environments

The combined utilization of fiber-reinforced polymer (FRP) composites with coral aggregate concrete (CAC) in remote island areas contributes to the reduced construction cost and construction period, offering a promising application. However, the evolution pattern and deterioration mechanism of flexural behavior for FRP bars reinforced CAC beams in marine service environments remains unclear. Thus, this paper investigates the flexural behavior of basalt-FRP (BFRP) bars reinforced CAC beams under seawater immersion and dry-wet cycle conditions using laboratory-accelerated aging methods. The research considers the effects of exposure temperature and corrosion age on their failure modes, flexural stiffness, ultimate loading capacity, and deformation deflection. The experimental results revealed that with the increase in corrosion age and exposure temperature, the amount of vertical cracks of CAC beams decreased and their crack depth also exhibited a slight reduction, but their crack width and spacing at failure significantly increased. After being attacked by seawater environments, the load-deflection curves of CAC beams experienced an enhanced slope of the ascending section (i.e., flexural stiffness), but this strengthened flexural stiffness did not result in an enhancement in the ultimate load capacity. Instead, with prolonged corrosion and higher temperatures, the ultimate load of CAC beams displayed significant degradation, accompanied by reduced mid-span deflection. After 12 months of seawater exposure to wet-dry cycle conditions at 60 °C, the ultimate load and mid-span deflection of CAC beams degraded by approximately 25.0 % and 56.6 %, respectively. The study also predicted the flexural bearing capacity of CAC beams utilizing existing specifications for FRP-reinforced normal aggregate concrete (NAC). It was concluded that the formulae for flexural loading capacity for FRP-reinforced NAC beams were still suitable for CAC beams.

Enhancing energy absorption of the sandwich beams with a synergetic strategy of flexible/rigid materials in re-entrant auxetic cores under flexural loading

Enhancing energy absorption of the sandwich beams with a synergetic strategy of flexible/rigid materials in re-entrant auxetic cores under flexural loading

Enhanced impact resistance of RC beams using various types of high-performance fiber-reinforced cementitious composites

This study investigates the impact resistance of reinforced concrete (RC) beams using various types of high-performance fiber-reinforced cementitious composites (HPFRCCs). A total of ten large-sized RC beams were fabricated and tested under static and impact loading conditions. Four different types of HPFRCCs with 2% by volume of steel, polyvinyl alcohol (PVA), and polyethylene (PE) fibers were considered. Ultra-high-performance fiber-reinforced concrete (UHPFRC) based on steel fibers demonstrated superior compressive and tensile strengths, while high-performance strain-hardening cementitious composite (HP-SHCC) based on PE fibers exhibited the highest strain and energy absorption capacities. The steel-bar reinforced (R-) UHPFRC and HP-SHCC beams showed superior flexural load capacity compared to reinforced normal strength concrete (R-NSC) beams. The highest ductility of 8.02 was found in the R-HP-SHCC beam, almost 5 times higher than that of the R-NSC beam. By drop hammer impact with a kinetic energy of 30 kJ, the R-UHPFRC beam completely failed due to its higher reaction load and lower structural ductility, while other RC beams made of NSC and HPFRCCs withstood the identical impact load. The R-HP-SHCC beam exhibited the best impact resistance, with a 29.1% lower maximum deflection compared to the R-NSC beam, and the largest residual load capacity after the impact damages. The R-HP-SHCC beam, despite being damaged, showed no reduction in flexural stiffness, yet it demonstrated an impressive 5.4% increase in load capacity compared to the undamaged beam.

Time-dependent behaviour of 3D printed fibre-reinforced limestone calcined clay cement concrete under sustained loadings

The evolution of 3D-printed concrete (3DPC) structures has made remarkable impacts in the construction industry and academia for prospective engineering practice globally. This is due to promising outcomes of various investigations on its construction coupled with several advantages it offers over conventional cast concrete. However, the time-dependent deformation of 3DPC under sustained loading is still unknown and requires extensive research. Quasi-static studies have also shown that creep could be of great concern due to its production technique involving layer stacking, which eventually leads to weak interlayer bond strength. This paper experimentally investigates the time-dependent behaviour of fibre-reinforced printed concrete (FRPC) containing limestone calcined clay cement (LC3) under sustained tensile and flexural loadings. The experimental tests conducted on LC3-FRPC specimens in two orthogonal directions were individual creep and shrinkage to determine other parameters associated with creep responses, including creep fracture. The specimens for tensile and flexural creep were subjected to sustained stresses of 40, 60 and 80 % of the tensile and 40 % flexural strength results obtained from quasi-static tests. The quantified creep is compared in terms of the difference in stress levels, as the results revealed that none of the specimens fractured under sustained loadings. Instead, higher direct tensile strengths were recorded for the creep specimens after 225 days loaded at different stress levels. Then, it is postulated that direct tensile tests on similar LC3-FRPC specimens without creep loading may confirm that the monotonic stress-strain response at the age at which the tests are terminated forms an envelope for creep fracture.

Influence zones of continuous beam systems

Unlike influence lines, the concept of influence zones is remarkably absent within the field of structural engineering, despite its existence in the closely related domain of geotechnics. This paper proposes the novel concept of a structural influence zone in relation to continuous beam systems and explores its size numerically with various design constraints applicable to steel framed buildings. The key challenge involves explicitly defining the critical load arrangements, and is tackled by using the novel concepts of polarity sequences and polarity zones. These lead to the identification of flexural and shear load arrangements, with an equation demarcating when the latter arises. After developing algorithms that help identify both types of critical load arrangements, design datasets are generated and the influence zone values are extracted. The results indicate that the influence zone under ultimate state considerations is typically less than 3 adjacent members for any given beam within a continuous system, rising to a maximum size of 5 adjacent members. Additional insights from the influence zone concept, specifically in comparison to influence lines, are highlighted, and the avenues for future research, such as in relation to the newly identified shear load arrangements, are discussed.

Flexural properties of bamboo scrimber under different temperature conditions: Experimental study and mathematical model

Changes in ambient temperature significantly affect the flexural properties of bamboo scrimber. From the perspective of structural safety, temperature is one of the most important conditions to be considered when using structural components made of bamboo scrimber. This experimental study investigated the flexural performance of bamboo scrimber across a broad temperature range of −30 °C to 250 °C, providing essential data for its use as a structural member under different temperature conditions. Through a series of tests conducted at different temperature conditions with utilization of scanning electron microscopy, the damage modes and failure mechanism of bamboo scrimber were analyzed at both macroscopic and microscopic levels. It was found that the failure modes of bamboo scrimber under different temperature conditions were mainly categorized as simple tensile fracture damage, split tensile damage and brittle tensile fracture damage, in which the brittle tensile fracture damage only occurred in the specimens at a temperature of 250 °C. In general, the flexural strength and modulus of elasticity decrease with increasing temperature; when the temperature was increased from 20 °C to 250 °C, the specimens' flexural strength and modulus of elasticity decreased by 87.95 % and 90.25 %, respectively. Microscopic analysis revealed that these variations were correlated with alterations in the shape, structure and composition of the internal cells. Moreover, based on the Hognestad model, a mathematical relationship model between the load-displacement curves of bamboo scrimber and the temperature was derived, which can accurately predict the flexural load capacity of bamboo scrimber under varying temperature conditions.

Tensile properties of steel fiber reinforced recycled concrete under bending and uniaxial tensile tests

It is important to study the tensile behavior of steel fiber reinforced recycled concrete (SFRRC) for the reliability of structural design. This paper investigates the effects of different mixture systems, including full-NA, full-RCA, full-RFA, full-RA, and full-RA+10%RP, on the tensile behavior of recycled concrete through uniaxial tensile and three-point bending tests. In addition, the effects of the volume content of steel fiber on tensile behavior are investigated. The uniaxial tensile strength and stress-strain curves of SFRRC were tested and the load-deflection, P-CMOD, double K fracture parameter and fracture energy under flexural tensile load were measured. The results show that the incorporation of recycled materials may negatively affect the tensile strength of recycled concrete. Compared with natural concrete, the uniaxial tensile strength decreased by 28.4%–50.2 % and the flexural tensile strength decreased by 17%–42.52 %. In addition, tensile properties, such as initial crack stress, peak strain, double K fracture toughness, and fracture energy, will also decline. The effect of the volume content of steel fibers on the tensile properties of recycled concrete with different mixed systems is analyzed. The steel fiber changes the tensile cracking mode of recycled concrete. When the content of steel fiber exceeds 1 %, the SFRRC of different mixed systems has the phenomenon of deflection hardening. When the fiber content is 2 %, the uniaxial tensile strength is increased by 13.83%–69.07 %. Contrasting with the control group, the recycled concrete group containing 2 % steel fiber showed enhanced fracture energy, which was increased by 15–23 times with different mixture systems. Uniaxial tensile constitutive models of SFRRC have been established under different mixture systems. The tensile stress-strain response of SFRRC was obtained indirectly by inverse analysis. It has been found that flexural tensile tests overestimate the post-crack properties of materials, and this phenomenon is more obvious in recycled concrete. This research is of great significance for the structural design of SFRRC.

Improving sustainability of precast concrete sandwich wall panels through stone waste aggregates and supplementary

Precast concrete sandwich wall panels offer advantages such as design flexibility, ease of installation, cost-effectiveness, and energy efficiency due to the incorporated insulation layer, but regular concrete production has sustainability issues. This study aims to improve the sustainability of these panels by utilizing stone waste aggregates as a replacement for natural aggregates and supplementary cementitious materials as a partial replacement for cement. The panels were made with two concrete wythes reinforced with steel fibers and joined using basalt fiber-reinforced polymer (BFRP) connectors, with high-density expanded polystyrene (EPS) insulation (30 kg/m3) in between. Self-compacting concrete mixes with varying proportions of stone waste aggregates and supplementary cementitious materials were used. Full-scale wall panels were cast and subjected to flexural tests per ASTM standards, analyzing load-displacement curves, ultimate bearing capacity, and failure modes. The incorporation of steel fibers and stone waste aggregates resulted in substantial increases in failure load and flexural strength compared to controlled concrete panels, with the stone waste steel fiber panels exhibiting significantly higher maximum cracking loads and improved energy absorption and ductility. The inclusion of these sustainable materials, along with basalt fiber connectors and grooves in the EPS layer for mechanical interlock, prevented brittle failure modes and enhanced the composite action, leading to more ductile behavior under flexural loading. Utilizing sustainable materials like stone waste aggregates (100% replacement) and supplementary cementitious materials (30% replacement) in these panels can contribute to eco-friendly and efficient construction practices while maintaining adequate structural performance, paving the way for more sustainable building systems

Reinforcement of Concrete Structures with High-Performance Fiber-Reinforced Concrete (HPFRC)

The incorporation of high quality fibers into very high strength concrete matrices leads to materials that are especially suitable to withstand extreme loads. For this reason, these materials are adequate for reinforcement and durability improvement of buildings and infrastructure constructions. The general objective of this work is to numerically study the flexural behavior of concrete structural elements reinforced with HPFRC. This general goal includes the analysis of the effect of the different variables, including the content and type of fibers, as well as the thickness of the reinforcement. The results of this analysis can contribute to improving the efficiency of the intervention techniques. For this purpose, numerical models are calibrated to reproduce the behavior observed in experimental tests carried out on HPFRC elements. Then the models are used to reproduce reinforced concrete beams reinforced with HPFRC under flexural loading. Finally, the effect of the aforementioned design variables on the behavior of reinforced beams is studied using the calibrated models. The results show the efficiency of the intervention increases with the fiber content and thickness of the reinforcement layer. However, the definition of the optimal design should also consider other criteria, such as constructional limitations and cost analysis.

Recycling of wasted wool fibers from sheep shearing for green building components: A review

It is nowadays recognized that the building sector causes the greatest environmental impact in terms of both waste production and carbon emissions. Within the context of ecologically sustainable development (ESD), the construction sector is looking for more eco-friendly materials, such as natural fibres. Natural fibers are worldwide recognized as ideal replacement for traditional construction materials, providing excellent thermal and acoustic insulation for building but also for adoption as reinforcement fibers in cement mortars, composite materials, solid boards/panels, raw biomasses, multi-layers, filled loosen/foaming types, particles, slurry types, coils, bricks, etc. The aim of this work is to provide a clear overview on the natural fibers currently employed in the green production of building components, with the main focus on wool fibers deriving from the livestock sector, where wool waste disposal is a crucial problem. This article is a review conducted using the Systematic Literature Review (SLR) approach, a globally recognized method that is not inherently innovative. The innovation of this article lies in the addressed topic, which is relatively new and has only recently gained significant attention, resulting in a limited number of highly relevant articles in the literature.A systematic literature review of the use of wool fibers for green building components is conducted herein to highlight the characteristics that make such material a usable resource in the construction sector and the limits of its use. Given the findings from the reviewed papers, the authors could document that most of the reviewed articles aimed at analyzing the mechanical, thermal, and acoustic properties of building components containing wool fibres. The review highlights that the strength of the wool fiber relies on its thermal properties which can be exploited for building thermal insulation. The wool fiber is also featured to provide good resistance to flexural loads; conversely, all the studies highlighted a negative effect of wool fibers on the compressive behavior of the investigated building components. The analysis of the acoustic properties showed that given the strong capacity of the wool fiber to absorb sound, wool is a great alternative to the conventional materials derived from non-renewable resources.Nevertheless, despite the eligibility of such fiber to be employed soon in the building sector, the analysis about the economic viability of the manufacturing process suggests that the high costs for the raw material, labor, electricity, and above all the high volume of water have to be drastically reduced by prompting the development of sheep wool fiber waterless processing. The achieved results could represent a first step in planning the sustainable re-use of wool waste as natural, renewable, and biodegradable fiber in the construction sector, providing the possibility of creating a new supply chain and solving the problem of its disposal.

Chemical treatment, fibre length, and fibre loading affecting the mechanical and morphological characteristics of flax fibre/polylactic acid (PLA) green composites developed by injection moulding

AbstractThis paper presents the parametric investigation and optimization of various chemical treatment parameters that affect the mechanical performance of the green composite. The injection moulding method was used to produce the green composites using flax fibre (FF) and polylactic acid (PLA). The chemical parameters chosen to investigate their effects are chemical type (sodium hydroxide, sodium carbonate, and potassium hydroxide), chemical concentrations (1 %, 2 %, and 3 % (w/v)), and duration for fibre treatment (2 h, 4 h, and 6 h). The mechanical performance of the green composites was assessed by evaluating the various properties namely strength, modulus, and elongation under tensile, share, flexural, and compression loading conditions. The morphological study was also performed to examine the failure behavior of the composite after mechanical testing. The effect of fibre length (2 mm, 3 mm, 4 mm, 5 mm, and 6 mm) and fibre loading (10 wt.%, 20 wt.%, and 30 wt.%) on the performance of the flax fibre (FF)/polylactic acid (PLA) composite was also investigated. The fibre dispersion, fibre orientation, and fibre length retention were investigated to assess the characteristics of fibre during injection moulding of the developed flax fibre (FF)/polylactic acid (PLA) composite.

Mechanical, durability and microstructural properties of waste-based concrete reinforced with sugarcane fiber

Extensive research has focused on producing sustainable concrete by exploring waste and recycled materials as alternatives to virgin substances. However, waste-based concretes often exhibit inferior durability and mechanical performance compared to traditional concrete. Incorporating reinforcement agents can enhance their performance. This study investigates the use of sugarcane fiber as a reinforcement in waste-based concretes containing fly ash (FA), ground granulated blast furnace slag (GGBS), and recycled concrete fine and coarse aggregates (RFA and RCA). Five dosages of sugarcane fibers (0 %, 1 %, 2 %, 3 %, and 4 % by fine aggregates mass) were examined. Mechanical and durability tests, including compressive strength, flexural strength, water absorption, and chloride ion penetration, were conducted. Scanning electron microscopy and micro-porosity analysis were employed for further assessment. Results show that adding sugarcane fiber enhances the waste-based concrete properties, with 3 % being the optimal dosage. This dosage improves compressive strength by 16 %, flexural strength by 35 %, flexural load bearing capacity by 34 %, energy absorption by 107 %, and toughness index by 6 %, while reducing water absorption by 4 % and chloride ion penetration by 23 %. Further increases in fiber dosage decrease concrete properties. The enhanced behavior is attributed to reduced porosity, refined pore structure, and reduced microcrack propagation. This study underscores the potential of incorporating sugarcane fiber along with waste materials to develop eco-friendly composites, aiming to mitigate carbon dioxide emissions and address environmental concerns.

Study on flexural and self-repairing properties of shape memory alloy concrete beams

The generation and expansion of cracks in concrete materials have always been a problem that needs to be solved, and an increasing number of scholars are beginning to hope that structures will have bionic functions of self-diagnosis and self-repairing of damage. In this study, shape memory alloy (SMA) concrete beams are prepared. The flexural and self-repairing properties of SMA concrete beams were investigated by a four-point bending test. The effects of various factors on the bearing capacity, ductility, and crack width before and after repair were analyzed. The experimental results indicate that the increase of SMA fiber content and the complexity of the SMA bar end shape can significantly enhance the flexural bearing capacity and repair performance of the beam. The increase in the bond length of SMA bars can enhance the bending resistance of the beam, but it will reduce its self-repairing performance. The repair rate of SMA on concrete cracks is 45.7 %-76.5 %, and the load recovery rate is between 49.4 % and 80.6 %. The flexural load capacity calculation formula is proposed, and the calculation results closely match the test values, providing a reference for the application of SMA.

The Seismic Behavior of Rectangular Concrete-Encased Steel Bridge Piers: A Review

This paper proposes a review of the previous research work and the representative publications regarding the seismic behavior of the concrete-encased steel (CES) columns. Concrete-encased steel sections are composed of steel sections encased in reinforced concrete members. The research work recently showed increased attention to this type of column due to its advantages compared to conventional reinforced concrete columns. Firstly, the analytical studies of the behavior of the CES columns under axial loads, including comparative studies between different research works, are presented. Then, the behavior of the CES columns under combined axial and flexural loads is also highlighted. An overview of the analytical confinement material models is addressed. In addition, the discussion and summary of the seismic behavior of the CES columns and the important parameters affecting the seismic behavior of these types of columns are included. Although important progress has been made by the previous studies in the CES columns under the axial load and the combination of axial and seismic loads, they fundamentally focused on the building columns, and little attention was paid to the impact of lateral reinforcement and their configuration in bridge piers. Due to the lack of studies on the parameters affecting the seismic behavior of the bridges, more studies should still be made to better understand the behavior of the CES bridge piers. This paper provides a reference for the research and engineering practice of concrete-encased steel bridge piers. It also concludes with suggestions for future studies to integrate the seismic requirement of the CES bridge piers in Canada.

Design and evaluation of mechanical strength of multi-material polymeric implants for mandibular reconstruction.

Reconstruction of mandible implants to address segmental abnormalities is still a challenging task, both in vitro and in vivo. The mechanical strength of the materials used is a critical factor that determines how well bone is regenerated. The reconstruction technique of mandibular abnormalities widely uses polymeric implants. It is critical to evaluate the mechanical resilience under different load cases, including axial, combined, and flexural loading conditions. This study developed implants for mandibular defects using a combination of four materials: polylactic acid (PLA), polyethylene terephthalate glycol (PETG), thermoplastic polyurethane (TPU), and polycaprolactone (PCL), with the aim of mimicking the inherent characteristics of cortical and cancellous bone structures and evaluating their mechanical properties to support bone Osseo integration. The eleven of these combinations of structures result below the micro strain threshold level of <3000 µε, and the five combinations of the structures result in micro strain above the threshold value. The intact bone study results show that the stress under axial, combined, and flexural loading conditions is 27.6, 38.9, and 64.9 MPa, respectively. This study's stress results are lower than those from the intact bone study. The study found that the combinations of PLA and TPU material were most preferred for the cortical and cancellous bone regions of polymeric implants. These materials are also compatible with 3D printing. The results of this study can be used to find multi-material combinations that are strong and flexible.