Flexural Deflection Research Articles

Experimental research on the flexural properties and pore structure characteristics of engineered geopolymer composites prepared by calcined natural clay

The synthesis of high ductility geopolymer composites using excavated natural clay is an economical and environmentally friendly method to realize the utilization of excavated natural clay. This paper presents an experimental research on the flexural properties and pore structure characteristics of engineered geopolymer composites (EGC) prepared by calcined natural clay. The EGC with different slag and fiber contents were prepared and the four-point bending tests were conducted on the EGC. The effect of slag and fiber content on the flexural strength, flexural deflection and flexural toughness were discussed. The microscopic pore structure characteristics of EGC were further analyzed. The optimal mixture ratio of calcined clay-based EGC with the highest flexural toughness was proposed. The results show that fiber can significantly enhance the flexural properties and cracking control ability of EGC. The ultimate flexural strength, flexural deflection, flexural strengthening index and flexural toughness of EGC all increase with increasing fiber content. The results also show the addition of 10.0% slag can increase the flexural strength and flexural toughness, while excessive slag content reduces the flexural properties. The EGC with 10.0% slag content and 2.5% fiber content exhibits excellent flexural properties and cracking control ability. The ultimate flexural strength and flexural toughness index reach 9.75 MPa and 486.11, showing the highest flexural toughness.

Extrusion Parameters Optimization and Mechanical Properties of Bio-Polyamide 11-Based Biocomposites Reinforced with Short Basalt Fibers.

The increasing demand for sustainable materials in high-value applications, particularly in the automotive industry, has prompted the development of biocomposites based on renewable or recyclable matrices and natural fibers as reinforcements. In this context, this paper aimed to produce composites with improved mechanical and thermal properties (tensile, flexural, and heat deflection temperature) through an optimized process pathway using a biobased polyamide reinforced with short basalt fibers. This study emphasizes the critical impact of fiber length, matrix adhesion, and the variation in matrix properties with increasing fiber content. These factors influence the properties of short-fiber composites produced via primary processing using extrusion and shaped through injection molding. The aim of this work was to optimize extrusion conditions using a 1D simulation software to minimize excessive fiber fragmentation during the extrusion process. The predictive model's capacity to forecast fiber degradation and the extent of additional fiber breakage during extrusion was evaluated. Furthermore, the impact of injection molding on these conditions was investigated. Moreover, a comprehensive thermomechanical characterization of the composites, comprising 10%, 20%, and 30% fiber content, was carried out, focusing on the correlation with morphology and processing using SEM and micro-CT analyses. In particular, how the extrusion process parameters adopted can influence fiber breakage and how injection molding can influence the fiber orientation were investigated, highlighting their influence in determining the final mechanical properties of short fiber composites. By optimizing the process parameters, an increment with respect to bio-PA11 in the tensile strength of 38%, stiffness of 140%, and HDT of 77% compared to the matrix were obtained.

Flexural behavior of bonded post-tensioned concrete beams with steel or GFRP bars

Post-tensioned concrete beams with GFRP reinforcement have gained attention in recent years due to their unique flexural behavior and potential cost benefits. Because of the absence of comprehensive guidelines in international codes and limited application in constructions, this hybrid system is adopted in the current paper as a pioneering solution for sustainable and eco-friendly construction practices. Particularly noteworthy is the corrosion resistance of GFRP bars, which significantly enhances the durability of structures. The influence of using GFRP with bonded post-tension concrete beam is experimentally investigated compared to concrete beams with prestressing and non-prestressing reinforcement. Eight concrete beams with different reinforcement types and ratios were cast and tested under three-point load. Flexural resistance, crack pattern, deflections, and strains of the beams were compared with a reference beam with prestressing and non-prestressing reinforcement. Experimental load capacities of the tested beams were compared to those obtained from various international codes. The experimental results revealed that the beams with GFRP bars had smaller failure load and larger deflection compared to those with non-prestressing steel by up to 25 % and 37 %, respectively. A 3D finite element model (FEM) was developed and validated by comparing the numerical results with those obtained from the experiments. A sensitivity analysis was performed, using the validated FEM, by changing the concrete strength, steel yield stress, and GFRP ultimate strength by ± 20 %. The sensitivity analysis included seventy-two beams which had the same dimensions, loading, and boundary conditions of the tested beams. Changing the concrete strength only led to varying the beam capacities by −7 % ∼ + 4 %. Changing the steel yield stress only led to changing of the beam capacities by −13 % ∼ + 11 %. No change was observed when the GFRP ultimate stress was varied by 20 %.

Effect of recycled aggregates with different parent strength and fly ash on flexural strength of recycled aggregate concrete prisms

Fast consumption of conventional ingredients of concrete and waste generated due to demolishing old buildings is a multi-fold problem in the concrete industry. Hence the sustainable alternative of it is the need of the day. In this research work effect of binary blending of demolished waste and fly ash on the flexural strength of plain concrete prism is presented. The properties of aggregates and cement are evaluated. The physical and chemical properties of fly ash were determined. Recycled aggregates from demolished waste with different mix ratios (1:2:4 and 1:1.5:3) were used. Optimization of recycled aggregates; by evaluating concrete cylinders in 12 batches; showed 35% as optimum. At the optimum dosage of recycled aggregates fly ash was used from 2.5% to 15% with an increment of 2.5% to optimize its dosage. Compressive strength test of the standard-size cylinders and their comparison with control concrete showed a 10% dosage of a fly as the optimum percentage to replace the cement in the concrete matrix. Using both optimized dosages of recycled aggregates and fly ash prism specimens of900mmx150mmx300mm were cast in four batches. The beam specimens were cured for 28 days followed by an evaluation of flexural strength and deflection under centric load in the universal testing machine. Test results of flexural strength (only 15% loss) showed good potential for both waste materials in the concrete matrix. Recycled aggregate with higher parent strength showed better performance than its other counterparts. With higher-strength recycled aggregates residual flexural strength was recorded as equal to 93%. For all specimens recorded deflection was within the allowable limits of ACI-318.

Comparative analysis of spinning techniques on the performance of full-strength-grade engineered cementitious composites: Mechanical characteristics, pore structure, fiber distribution, micromorphology

The spinning techniques used for ultra-high molecular weight polyethylene (UHMWPE) fibers are crucial for enhancing the performance of ECC. However, the specific effects of different spinning techniques for UHMWPE fibers on ECC's performance are not well understood. To address this gap, this study investigates the influence of dry-spun and wet-spun spinning techniques on both the macroscopic mechanical properties and microscopic characteristics of full-strength-grade ECC. Comprehensive tests were conducted, including assessments of tensile, compressive, and flexural strength. Additionally, detailed CT-based 3D reconstruction and SEM analysis were performed to examine the pore structure, fiber orientation, and micromorphology. The findings reveal that the surface irregularities and roughness of dry-spun fibers lead to stress concentration, whereas the more uniform surface of wet-spun fibers enhances their bridging performance. Compared to dry-spun fibers, wet-spun fibers significantly improve ECC's tensile and flexural properties, enhancing ultimate tensile strength by up to 22.7 % and ultimate flexural deflection by up to 50.2 %. Additionally, wet-spun fibers result in a more uniform pore structure and better fiber alignment, creating a denser and more compact matrix. These microstructural improvements contribute to superior load transfer and energy absorption characteristics, enhancing ECC's overall performance and durability. These results underscore the critical role of fiber spinning techniques in optimizing ECC performance, contributing to more durable and sustainable structures in high-performance construction applications.

Mechanical analysis of al/foam composite sandwich panels under elastic and elastoplastic states

This study performs mechanical analysis for Al/Foam composite sandwich panels under 3-point bending using numerically and experimentally. The flexural rigidity, elastic deflections, and normal, shear stresses are obtained by analytical calculations of the Timoshenko beam equation and compared finite element (FE) models for 3-point bending loading conditions. The FE models are constructed using 2D single-layer shell and 3D solid discrete-layer models. The validity of FE models at the analysis is evaluated for Al/PVC Foam sandwich composites for the elastic state. The experimental bending results of Al/XPS Foam sandwich composites are compared with numerical models at elastic and elastoplastic states. The elastic results indicate that the out-of-plane deflection results agree well across numerical and analytical models. Normal stresses at the core are higher in 3D discrete-layer solid models compared to laminated shell theory-based models for thick plates, due to the more accurate characteristics of the discrete-layer solid models. The Timoshenko beam theory-based analytical bending results show a good correlation with the results from laminated shell theory-based finite element method (FEM) analyses. Elastoplastic FEM analysis indicates that discrete-layer-based 3D solid FEM models effectively predict local effects dependent on indentation failure.

Research on the flexural performance of recycled coarse aggregate concrete beams after carbonation

This paper discusses the flexural behavior of carbonated recycled aggregate concrete (RAC) beams through experimental data. We produced fifteen beams, each varying in recycled aggregate replacement ratios: 0 %, 30 %, 50 %, 70 %, and 100 %. Each replacement ratio included three beams, amounting to different levels of carbonation: non-carbonated, partially carbonated, and completely carbonated. Post accelerated carbonation processes; flexural testing was conducted. The findings reveal that beams incorporating varying amounts of recycled coarse aggregates (RCA) but maintaining identical carbonation levels exhibited a minor reduction in the cracking moment, with negligible variations in ultimate flexural strength and deflection. Moreover, beams sharing the same RCA replacement ratio demonstrated increased cracking moment, ultimate flexural strength, and stiffness with advancing carbonation levels, while deflection tended to decrease. Based on these findings, predictive models for cracking moment and ultimate flexural strength of carbonated RAC beams were developed. Comparisons between experimental outcomes and numerical simulations, particularly within the RAC50 group, indicated nearly identical results.

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.

Microstructure and mechanical properties of multi-phase TiAl alloy matrix composites consolidated via field-assisted sintering technique

AbstractIn this study, fully densified Si3N4/TiAl composites were fabricated using the field-assisted sintering technique (FAST). Microstructural analysis showed the evolution of a continuous network structure consisting of minor fractions of in-situ formed Ti2AlN, unreacted Si3N4 ceramic particles and dominant Ti5Si3 intermetallic phases within the TiAl matrix at Si3N4 content above 1.5 wt%. The hardness of the developed composites increases with increasing Si3N4 content, with 7Si3N4/TiAl composite exhibiting the highest hardness of approximately 487 HV1.0, which was about 57% higher than that of the sintered pure TiAl alloy. Among the sintered samples, 1.5Si3N4/TiAl composite displayed the highest flexural strength of 832.65 ± 12.88 MPa (34.3% higher than pure TiAl matrix) with a deflection of 0.14 mm. In contrast, the lowest flexural strength and deflection of 535.44 ± 21.14 MPa and 0.09 mm were obtained in composite reinforced with 7 wt% Si3N4 ceramic content. The fractured surface of the sintered samples displayed predominantly cleavage fracture mode.

Hybrid fiber reinforced ultra-high performance coal gangue geopolymer concrete (UHPGC): Mechanical properties, enhancement mechanism, carbon emission and economic analysis

The low carbonization of ultra-high performance concrete (UHPC) has become a hot topic for sustainable development in the construction industry. Calcined coal gangue was used as aggregate and binder to prepare ultra-high performance coal gangue geopolymer concrete (UHPGC) in this paper. The hybrid reinforcement effect of steel fibers, calcium carbonate whiskers (CW), and carbon nanotubes (CNTs) on UHPGC was studied in the experiment. The results indicated that when the mixing ratio of straight steel fibers and hooked-end steel fibers was 2:1, the 28 d-compressive strength of UHPGC reached 145.94 MPa. However, excessive hooked-end steel fibers deteriorated the reinforcement effect of adjacent fibers and reduced the mechanical properties of UHPGC. CW and CNTs had a more significant improvement in the flexural properties of UHPGC. The bridging effect of CNTs and CW dispersed the stress on the matrix and delayed the formation and development of micro-nano cracks. Meanwhile, CNTs and CW improved the fiber bridging energy dissipation, thereby improving the flexural properties of UHPGC. The UHPGC had the highest flexural strength and flexural deflection of 13.59 MPa and 4.12 mm, respectively. The UHPGC prepared in this paper had lower carbon emissions and economic costs compared to traditional UHPC. Overall, this study provided valuable references for the resource utilization of coal gangue and the multi-scale strengthening and toughening of UHPGC.

Tensile and flexural performances of prefabricated slabs with wet UHPC connection

A wet connection for prefabricated slabs using Ultra-High-Performance Concrete (UHPC) was proposed and experimentally investigated. Influence of parameters such as the lap length of dowel rebar, the groove key size and the arrangement of post-placed rebar in grooves were comparatively explored. Four tensile specimens and eight flexural specimens were designed and tested. The crack development, failure mode, load-deformation characteristics, strains and bearing capacity were observed and analyzed. The results indicated that the lap length of dowel rebar significantly influenced the failure mode. Dowel rebar with insufficient lap length in post-cast UHPC connection exhibited rebar pulling-out failure, and lap length of 12 times diameter of the dowel rebar could achieve mechanical performance equivalent to cast-in-situ construction. Based on analysis of the test results, the prediction for tensile capacity of UHPC connection was recommended based on existing prediction formula for bonding stress of rebar in concrete, and the theoretical predicting formulas for flexural bearing capacity and deflection of prefabricated slabs having different dowel rebar lap lengths in UHPC connection were proposed, which showed good agreement with test results.

Experimental study on flexural behavior and bending capacity prediction of Q550E steel beams within corroded shear span

An experimental study is carried out to investigate the degradation behavior of Q550E HPS steel beams with corroded shear span. At first, tensile tests of 15 pieces of steel are undertaken to obtain the degradation law of mechanical property parameters. Four steel beams with different corrosion damage levels in shear span are designed by electrochemical accelerated corrosion. The flexural loading tests of corroded steel beams are conducted, and the mechanical response of local corrosion to steel beams behavior is discussed. The necessity of lateral bracing is discussed theoretically. Considering the constitutive model affected by corrosion and the role of stiffeners, a predictive model of bending bearing capacity is proposed. The results show that the increasing corrosion damage will cause the failure position to move from mid-span to shear span, and the failure mode will shift from mid-span compressive flange buckling to bending-shear buckling, and finally appear web buckling. Corrosion damage level higher than 10% will lead to insufficient strain development. The proposed model can predict the flexural capacity and deflection well. Compared with the test results, the bearing capacity and deflection of corroded HPS beams are predicted by the nonlinear iterative method with high accuracy.

Effects of textile type on the flexural properties of prefabricated hollow-core slabs strengthened with PVA fibers-improved TRM

In this study, the utilization of textile-reinforced mortar (TRM) in the strengthening and rehabilitation field is investigated. To regulate crack width, polyvinyl alcohol (PVA) fibers were incorporated into the TRM matrix. Nine prefabricated hollow-core slabs strengthened with TRM, along with one reference slab, were subjected to static loading using a 4-point bending apparatus. The experimental variables consisted of the type of textile (glass, basalt, and carbon) and the number of textile layers (one, two, and three layers). The experimental findings demonstrated that the inclusion of PVA fibers improved the TRM by effectively controlling crack width and increasing energy absorption capacity. Among the textile types, carbon TRM-strengthened slabs exhibited the highest flexural capacity. This capacity increased by 74%, 119%, and 132% for slabs strengthened with one, two, and three layers of textile, respectively. Glass TRM-strengthened slabs demonstrated superior deformability, with an increase rate ranging from 202% to 331%. Finally, to predict the flexural capacity and deflection of the tested slabs, a theoretical analysis was conducted and validated by comparing the theoretical predictions to the actual test results for accuracy and reliability.

An inquisition on alkaline treated Banana/Sisal/Pineapple fiber epoxy composites for light to moderate load applications

To address the sustainable development goals, an attempt was made to investigate the alkaline treated and untreated Banana, Sisal, and Pineapple fiber epoxy hybrid composite for their mechanical and thermal properties. Tensile, Flexural, Impact, modulus, and Heat Deflection temperature (HDT) were evaluated and analyzed for low-load structural applications. The performance of Alkaline Treated Fiber composites was better than the untreated fiber composites. The treated Banana, Sisal, and Pineapple hybrid fiber epoxy composite has a high HDT value of about 78 °C, a maximum tensile strength of 104 MPa, a tensile modulus of 25 MPa, a flexural strength of 78 MPa, a flexural modulus of 5286 MPa,and an impact strength of 286 J m−1 when compared to other composites. Interfacial failure analysis was also carried out with the help of a Scanning Electron Microscope (SEM) to study the microstructural behavior of the tested specimens. It was observed that the alkaline treatment increases fiber-matrix interaction.

Optimizing the Mechanical Properties of Cement Composite Boards Reinforced with Cellulose Pulp and Bamboo Fibers for Building Applications in Low-Cost Housing Estates.

Africa is the third-richest continent in the world in terms of bamboo species. Despite these laudable natural resources, most African countries still use asbestos cement board as one of their major building materials. This is chiefly due to the high cost of equipment and technologies associated with non-asbestos-fiber cement board production. The current research seeks to underscore the possibility of utilizing these massive continent resources for non-asbestos-fiber cement board production by employing the existing production process in the asbestos cement industries via an innovatively developed laboratory-simulated Hatschek process. Non-asbestos-fiber cement boards incorporating kraft and bamboo fibers were successfully produced in the laboratory using this innovative method based on Hatschek technology, with natural fibre addition in the range of 2-6 wt.%. Experimental results revealed that the Flexural strength and deflection of the board improved significantly, producing optimum values of 10.41 MPa and 2.0 mm, respectively for composite board reinforced with 10 wt.% and 6 wt.% of kraft pulp and bamboo fibers, respectively. The SEM morphology of the fractured surfaces revealed the mode of composite fracture as well as good interaction at the fiber-matrix interface. Overall, the mechanical properties of the developed composite boards satisfy the minimum requirements of relevant standards based on fiber cement flat sheets and can be employed for internal building applications in low-cost housing estates in developing countries. The outcome of this research indicates that the current industrial production process based on Hatschek technology can be employed for non-asbestos-fiber cement board production using the studied natural fiber.

Flexural and cracking performance of ultra-high performance concrete beams with high-strength steel reinforcements

In this study, the flexural and cracking performance of ultra-high performance concrete (UHPC) beams reinforced with high-strength steel reinforcement (HSSR) is investigated. Four beam specimens, including two UHPC beams and two normal-strength concrete (NSC) beams with different HSSR ratios were tested under flexure. The effect of concrete type and HSSR ratio on the flexural behaviour was evaluated. The failure mode, load-deflection response, stiffness, ductility and strain of the concrete and HSSR were discussed. Test results show that UHPC coupled with HSSR achieved better flexural performance and the ability to limit the development of the crack. The flexural capacity, deflection and stiffness for the UHPC beams were increased but the ductility was decreased as the HSSR ratio increased. The flexural behaviors of UHPC beams were predicted by section analysis. The flexural performance of HSSR-UHPC beams should consider the contribution of steel fibre to the tensile strength. Considering the influence of steel fibre, an equation was proposed to predict the average crack spacing. UHPC beams showed excellent agreement with the experimental results. The maximum crack width of 630 MPa reinforced UHPC beams was calculated by NF P 18-710 in accordance with the test results.

Achromatic ribbed elastic meta-structure for ultra-broadband flexural wave manipulation

Elastic metasurfaces have shown remarkable ability in exotic wavefront manipulations based on the generalized Snell’s law (GSL), stimulating great promise for many potential applications, such as elastic wave signal processing, vibration control, and energy harvesting. However, elastic metasurfaces suffer from strong narrow-band confinement and dispersion modulation due to the inherent velocity-dispersive properties and the dispersion of the accumulated phase during propagation. To address this issue, we propose a novel conceptual design paradigm of achromatic ribbed elastic meta-structures (AREMs) beyond the narrow-band limit for the ultra-broadband manipulation of flexural waves in thin plates. We establish an analytical model for ribbed subunits to accurately solve the phase shift and amplitude of the transmitted waves. In addition, we reveal the relationship between broadband achromatic functionality and subunit phase shift dispersion. We theoretically design and numerically demonstrate three flexural wave manipulation functionalities in an ultra-broadband frequency range of 1–10 kHz, including flexural wave deflection, focusing, and splitting, with a relative bandwidth of 163.6 %. Finally, we experimentally verify the ultra-broadband flexural wave manipulation capabilities of AREMs. Our study may open new horizons for ultra-broadband high-efficiency achromatic and structurally simplified flexural wave-based devices, with promising extensions to other elastic wave modes.

Fiber fraction-dependent flexural behavior of high-performance fiber-reinforced concrete under static and repeated loading

The effect of the fiber volume fraction on the flexural behavior of high-performance fiber-reinforced concrete (HPFRC) under both static and repeated loading is highlighted through a series of experiments. All rectangular prism-shaped flexural specimens were 40 × 40 × 160 mm3 and subjected to a three-point bending (3 PB) fixture with a span length of 120 mm. Macro-hooked and micro-smooth steel fibers with volume contents of 0.0%, 0.5%, 1.0%, and 1.5% were investigated. The flexural strength and deflection capacity of the HPFRCs under static loading generally increased with increasing fiber volume content. The micro-smooth fiber mostly produced a higher flexural strength and a lower deflection capacity compared to the macro-hooked fiber. Under repeated loading, a larger fiber volume fraction generally resulted in higher HPFRC endurance limits, which exceeded 40,000 cycles with a fatigue stress ratio of <0.5, at a fiber volume fraction of 1.5 vol%. The flexural fatigue equations of the HPFRCs of various fiber contents were calculated with the fatigue stress amplitude as well as the fatigue stress ratio, based on the experimental data. The HPFRCs’ sensitivity to endurance limits generally decreased with increasing fiber content; this finding was greater when using the micro-smooth fiber than when using the macro-hooked fiber.

Behavior of steel box bridge girders subjected to hydrocarbon fire and bending-torsion coupled loading

This paper presents an experimental together with numerical investigation on behavior of steel box bridge girders under hydrocarbon (HC) fire and bending-torsion coupled loading conditions. Four test bridge girders fabricated utilizing single-box configured with twin-chamber supporting thin concrete slabs, taking into consideration sectional features and loading methods, were simultaneously subjected to HC fire exposure and bending-torsion coupled loading to analyze thermal and structural response. A numerical model established through program ANSYS, validated dependent on measured data generated from fire tests, was used to conduct a parametric analysis. Results show that significant discrepancies of temperature occur in mid-web and side-web of test bridge girders exposed to HC fire. Steel top flange has a significant influence on heat accumulation and transfer inside steel box, escape of water vapour in concrete slab and also fire resistance of steel box bridge girders. Deflection difference in transverse section of test bridge girders subjected to bending-torsion coupled loading gradually become predominant with fire exposure time. Test bridge girders without steel top flange experience a wide longitudinal crack in concrete slabs instead of excessive flexural deflection through entire fire exposure duration. Increasing longitudinal stiffeners in mid-web and bottom flange can effectively enhance fire resistance of steel box bridge girders. Timely evacuation of applied loads enforced on bridge girders during fire exposure can greatly delay deflection progression. The post-fire residual bearing capacity in test bridge girders can recover more than 80 % of initial bearing capacity after HC fire exposure. The experienced maximum temperature and fire exposure time has a predominant influence on post-fire recovery ability of steel box bridge girders under ventilation cooling conditions.

Study on Stiffened-Plate Structure Response in Marine Nuclear Reactor Operation Environment

As the regulations on greenhouse gas emissions at sea become strict, efforts are being made to minimize environmental pollutants emitted from fossil fuels used by ships. Considering the large sizes of ships in conjunction with securing stable supplies of environment-friendly energy, interest in nuclear energy to power ships has been increasing. In this study, the neutron irradiation that occurs during the nuclear reactor operation and its effect on the structural responses of the stiffened-plate structures are investigated. This is done by changing the material properties of DH36 steel according to the research findings on the neutron-irradiated steels and then performing the structural response analyses of the structures using analytical and finite-element numerical solutions. &amp;#x00052;esults reveal the influence of neutron irradiation on the structural responses of the structures. It is shown that both the strength and stiffness of the structures are affected by the neutron-irradiation phenomenon as their maximum flexural stress and deflection are increased with the increase in the amount of neutron irradiation. This implies that strength and stiffness need to be considered in the design of ships equipped with marine nuclear reactors.