Flexural Performance Research Articles

Flexural and impact performance of Kevlar/basalt fabric interlayer hybrid curved composites

FRP composite has become one of the most preferred materials in lightweight applications. Design freedom is a key benefit which is reflected in the choice of fibres, stacking sequence and others. Hybridisation of hard inorganic fibre and organic ductile fibres can lead to synergetic effects. In this paper, an interlayer hybrid curved laminated composite reinforced with woven Kevlar and basalt fabrics and manufactured by a hand lay-up process with epoxy resin was prepared. Experimental investigation on the flexural and impact properties of composite laminates has been performed. The results of the investigation showed that the placement of Kevlar fibres on the impact side can increase the impact and flexural strengths, sample H3 (K3B2K3B2) has the highest impact strength and absorbed energy among seven hybrid laminates, valued at 92.89 KJ/m2 and 2.48 KJ. Compared with H5(B4K6) improved 41.6% and 40.9%, respectively. However, H5 has the highest flexural strength, reaching 231.7 MPa. In addition, the use of basalt fabric on the impact reverse side or multi-layer hybrid structuring further improves the impact properties of the materials. A sandwich-structure composite with basalt layers in the middle and Kevlar layers on both sides shows further improvement in the flexural properties.

Fabrication and structural characterisation of hybrid timber-cardboard sandwich beams

This paper develops a novel class of timber-cardboard sandwich (TCS) panels, consisting of low-cost timber facings and a block-laminated corrugated cardboard core. Experimental and analytical studies are conducted to characterise the flexural performance of TCS beams made from recycled or waste materials. TCS beams made from scrap cardboard cores have the exceptional characteristic of being made mostly from waste, up to 91% by volume or 76% by weight, and are demonstrated to have equivalent performance to beams made with recycled cores. TCS beam flexural behaviour is found to be primarily governed by timber face sheets, with very strong composite action and no observed core shear or debonding failure. The strength, stiffness, and dominant failure mode of TCS beams are thus shown to be accurately predicted using composite sandwich beam theory and cross-sectional analysis. TCS beam bending strength is also found to be significantly higher than conventional foam-core structurally-insulated panels with comparable densities, making them highly viable as a bio-based structural alternative. These research findings enhance the capacity and confidence by which cardboard can be used as a construction feedstock, supporting societal progression toward a greener and more circular economy.

Characterization of Flexural Behavior of Hybrid Concrete-Filled Fiber-Reinforced Plastic Piles.

The reinforcing fibers in filament winding fiber-reinforced polymer (FFRP) are not arranged in the axial direction; thus, the members are vulnerable to bending and shear stresses. To address the limitations, this study evaluated FRP-concrete composite piles with reinforcing fiber arranged in circumferential directions. In particular, modular pultruded FRP (PFRP) members were fabricated with reinforcing fibers arranged in the axial and circumferential directions. The exterior of the fabricated PFRP members was reinforced with FFRP, and the flexural performance of these members was investigated through flexural strength tests. The results obtained from the flexural tests and flexural-stiffness prediction formula differed by approximately 0.72-1.36 times. A comparison between the results of the flexural test and flexural-strength prediction equation showed an error of approximately 1 to 10%.

Experimental investigation of eco-friendly fiber-reinforced concrete using recycled and natural fibers, integrated with recycled aggregates

This study investigates the integration of recycled and natural fibers with recycled concrete aggregates to develop environmentally friendly fiber-reinforced concrete (FRC), with a primary aim of maintaining or enhancing its properties. Four concrete mixtures, namely plain concrete (C-Plain), recycled steel fiber-reinforced concrete (C-RSF), recycled plastic fiber-reinforced concrete (C-RPF), and kenaf fiber-reinforced concrete (C-KF), were formulated and analyzed for their fresh, hardened, and durability characteristics. A 50% replacement of natural coarse aggregates’ weight with recycled concrete aggregates (RCA) was implemented. By standardizing fiber volume fractions at 1.0% for all FRC mixtures, the study evaluated properties such as workability, dry density, ultrasonic pulse velocity (UPV), compressive strength, modulus of elasticity, post-cracking flexural performance, modulus of rupture, flexural toughness, splitting tensile strength, and freeze-thaw resistance after 100 and 300 cycles. Testing involved three specimens for each parameter at 7 and 28 days. The results indicated positive effects on post-cracking flexural performance, modulus of rupture, flexural toughness, splitting tensile strength, and durability with the incorporation of recycled and natural fibers. Notably, C-RSF demonstrated the highest compressive strength (46.63 MPa), flexural toughness (64.35 kN-mm), and modulus of rupture (7.46 MPa) compared to other FRC composites. Additionally, it exhibited minimal weight loss (2.18% and 3.07%) after freeze-thaw cycles, indicating exceptional durability. C-RSF exhibited superior performance, while C-KF showed enhancement slightly below that of C-RSF. Although not reaching the level of C-RSF, C-RPF positively influenced concrete performance. Compressive response either maintained performance or exhibited marginal reduction. The findings carry significant implications for developing environmentally conscious construction materials with enhanced mechanical and durability properties, thereby advancing sustainable construction practices.

Flexural Performance of Steel-Continuous-Fiber Composite Bar and Fiber-Reinforced Polymer Bar Hybrid-Reinforced Sustainable Sea-Sand Concrete Beams: Numerical and Theoretical Study

To investigate the flexural performance of steel-continuous-fiber composite bar (SFCB) and fiber-reinforced polymer (FRP) bar hybrid-reinforced sea-sand concrete (SSC) beams, a total of 21 SSC beams were numerically studied. The concrete damaged plasticity model (CDPM) and FRP brittle damage model were adopted, and the bond-slip behavior between the reinforcement and concrete was considered. Parametric studies were conducted to study the effects of the SSC strength, sectional steel ratio of the SFCB, core steel bar yield strength of the SFCB, out-wrapped FRP elastic modulus of the SFCB, and the ultimate tensile strength of the SFCB on the flexural performance of the beams. The results indicate that increasing the SSC strength and out-wrapped FRP modulus enhanced the bearing capacity and stiffness but reduced the ductility, shifting failure from concrete crushing to FRP bar fracture. A higher SFCB sectional steel ratio markedly improved the flexural stiffness, transforming the load–deflection curve. Elevated core steel bar yield strength maintained the cracking load and deflection while increasing the yield and ultimate loads. For SFCB fracture, higher ultimate tensile strength in the out-wrapped FRP enhanced the ultimate load and deflection, but not in concrete crushing failure. In addition, three failure modes were defined based on the proper assumption, with the proposed bearing capacity formulas aligning well with the FE results.

Assessment on flexural performance of monolithic glass considering spatial and depth characteristics of scratches

Glass products are widely used in building envelopes. Fracture can be triggered accidentally from the glass surface damage such as scratch. This study proposed an approach to assess the flexural performance of the aged monolithic glass panel, which has scratch with spatial and depth information detected via non-contact sensing. The coaxial double ring (CDR) test was conducted for experimentally evaluating the flexural strength on a total number of 160 scratched annealed (AN) and fully tempered (FT) glass specimens. Finite element (FE) analysis was performed to find the exact stress state by considering the geometric non-linear behaviour of glass panel under large deflection. Test and numerical results demonstrate that the scratch depth characterized by a confocal microscope and spatial location can both influence the failure load of FT glass, whereas AN glass is only sensitive to the latter. With combining linear elastic fracture mechanics (LEFM) theory, the relationship between the scratch depth and the residual strength of FT glass can be accurately determined. The spatial and depth characteristics of scratch can then be integrated for the failure load assessment of monolithic FT glass panel. The assessment framework can contribute to the accurate non-destructive assessment on aged architectural glass.

Flexural behavior of RC beams externally reinforced with CFRP composites using various strategies

Abstract The external composite material bonding is an effective and practical method for flexural strengthening of reinforced concrete (RC) beams, providing a large opportunity to develop high-performance and cost-effective structures. Numerous uses exist for carbon fiber-reinforced polymer (CFRP) materials as RC-member strengthening methods. However, issues with bonding and de-bonding continue to be a barrier to this technique's accomplishment. In this research, the CFRP sheets were integrated as an external strengthening material to evaluate their contribution to the flexural performance and so determine how well the CFRP sheets are being used. The experimental work includes one control beam and ten RC beams with CFRP sheets as external strengthening. All beams have the same dimensions: a length of 1.7 m and a sectional area of 20 cm × 25 cm. Experimental tests were carried out with varying CFRP types, lengths, numbers, and arrangements. Each beam’s performance was evaluated in terms of failure mode, ultimate load capacity, ultimate deflection, and a load–deflection curve. The findings demonstrate the effectiveness of CFRP strengthening by demonstrating a considerable improvement in the majority of the study variables. Furthermore, the CFRP strengthening offered an exterior crack-arresting mechanism.

Flexural performance of reinforced concrete beams strengthened using near-surface-mounted carbon-fiber-reinforced polymer bars: Effects of bonding patterns

The near-surface-mounted (NSM) fiber-reinforced polymer (FRP) technique is effective for enhancing the load carrying capacity of strengthened reinforced concrete (RC) beams. However, this technique significantly reduces the deformability of strengthened RC beams. To overcome this, the present study combines the NSM strengthening method with the partial bonding technique: the strengthening FRP reinforcement is partially bonded onto the concrete substrate). Six full-scale 4.3 m long RC beams strengthened with NSM FRPs using various bonding patterns were tested. The results indicated that mechanical interlocking grooves slightly improve the load carrying capacity, but have a negligible effect on the deformability of the strengthened beams. A decrease in the bond length increased deformability by 27.2 %, with only a 7.6 % drop in load capacity compared to that of the beam with full bonding. An advanced finite element model was developed and validated to confirm an optimal bond length of 930 mm for maximum flexural performance.

Experimental study on flexural performance of composite slabs with bent bars and postcast ultrahigh‐performance concrete joints

AbstractThis paper describes the use of joints with bent bars and postcast ultrahigh‐performance concrete (UHPC) joints to enable formwork‐free and support‐free construction of composite slabs. To investigate their flexural performance, static loading tests on three full‐scale simply‐supported slabs and one monolithic slab were carried out. Flexural capacity, stiffness, and crack development were recorded, resulting on flexural failure experienced by all specimens. Main cracks of composite specimens developed along the UHPC–normal concrete interface, and cracks on both sides of the UHPC joint developed evenly, similar with that of the monolithic specimen. Besides, composite slabs and a monolithic slab showed similar flexural capacity. UHPC joint was not cracked when failure occurred, and bottom bars were anchored and connected in the UHPC joint, proving that the flexural anchorage method is feasible. The average strain of the composite specimen across the UHPC joint was still consistent with the assumption of plain section, and there was an approximate linear relationship between the expansion width of the joint at the bottom of the slab and the maximum crack width at bottom bars. Moreover, middle bars contributed to the flexural capacity and stiffness of composite specimens, while horse stool reinforcement may effectively prevent the interface shear failure on the composite interface. Based on test results, the formula to control cracking of UHPC is given in this paper. The design methods on flexural capacity, stiffness, and expansion width of composite slabs are also presented and discussed.

Blast retrofit of shear-deficient high-strength concrete beams with ultra-high performance concrete

This research has investigated the ability of ultra-high performance concrete (UHPC) to improve the blast performance of high-strength concrete (HSC) beams. As part of the study 4 shear-deficient HSC beams built without stirrups and with dimensions of 125 mm × 250 mm × 2440 mm were retrofitted with a UHPC jacket and tested under simulated blast loads using a shock-tube. The retrofit involved replacing the existing cover with a cast in-situ UHPC jacket (with thickness of 20–40 mm). A companion set of beams was also tested under quasi-static four-point bending. The results from the blast and static tests are compared to a control set of HSC beams built without and with stirrups to examine the ability of UHPC to increase shear and flexural resistance, respectively. The effect of steel ratio (ρ = 1.6% or 2.4%), an important parameter which affects the behavior of HSC and UHPC beams, was also investigated in beams with 15M and 20M bars. Under static loading, the results show that the UHPC jacket was able to prevent shear failure, and improve flexural performance by increasing strength by 40–125%, stiffness by 80–100% and overall toughness by 56–144%, when compared to the companion HSC beams. Under blast loading, the UHPC increased shear capacity, prevented shear failure and improved blast performance by reducing displacements, increasing overall blast capacity and improving damage tolerance. For example, in the 20M set, the UHPC-retrofitted beam showed reductions of 26–63% in maximum displacements, and 88–100% in residual displacements under varying blast intensities. The steel ratio was found to play an important role on the failure mode of the retrofitted beams under static loading, with bar fracture observed in the beam with lower steel ratio of 1.6%. As part of the numerical study, the blast response of the UHPC retrofitted beams was predicted using 3D finite element (FE) modeling. The FE models were able to predict the failure modes and maximum displacements of the control and UHPC retrofitted beams, with an average numerical-to-experimental displacement ratio of 1.03 and an average error of 8%.

Flexural performance enhancement of modified gypsum-based composite boards using basalt fiber braids

In conventional fiber-reinforced gypsum boards, while the integration of fibers curtails crack propagation and moderately increases the flexural strength, the phenomenon of strain-softening is inevitably induced, which restricts the wider application of gypsum boards. The present study primarily focuses on evaluating the influence of basalt fiber (BF) braids on the flexural performance of fiber-reinforced modified gypsum matrix composite boards. The investigation considers factors such as the types of modified gypsum-based matrix, the number of BF braid layers, and the placement of fibers. During the experiments, the failure modes of various structural gypsum boards were observed, and comparisons were made regarding the changes in flexural stress-strain behavior, flexural strength, and displacement. Moreover, a reasonable explanation of the entire flexural stress process was provided based on the internal forces of the gypsum boards. Furthermore, a comparative analysis is conducted to examine the variations in ductility indices among different structural configurations of gypsum boards. The research results indicate that the combined action of fibers and BF braids effectively restricts the development of cracks, preventing a sudden decrease in stress during the growth stage. Additionally, BF braids fulfill their role, ensuring stress strengthening occurs within the gypsum board. Furthermore, the configuration of modified gypsum with fibers and two layers of BF braids (MG-BF-B-L2) exhibits the most significant improvement in flexural performance. Compared to modified gypsum group (MG), the flexural strength, entire ductility, and post-peak ductility have increased to 3.39 times, 7.66 times, and 1.58 times, respectively.

Suitability of Foamed Concrete for the Composite Floor System in Mid-to-High-Rise Modular Buildings: Design, Structural, and Sustainability Perspectives

This study investigates the application of lightweight foamed concrete (FC) in modular building floor systems to address challenges in lifting and transportation within modular construction. Initially, a literature review identifies FC’s characteristics and optimum mix design, considering its sustainability and strength. The comprehensive review highlights that FC can be a lightweight alternative to replace traditional concrete in floor structures. Further, this study conducted the life cycle assessment and indicates that FC with coarse fly ash substitution is the optimum mix, which releases less greenhouse gas emission (i.e., 740.89 kg CO2-eq/1 m3) than other mixes. Subsequently, the study conducted design verification and parametric study of composite floor systems (i.e., cold-formed steel-FC, timber-FC, and steel deck-FC). The results show similar flexural and shear performance compared to normal-weight concrete despite its lower density (1600 kg/m3) compared to normal-weight concrete (2400 kg/m3). Further, the reduction of modulus of elasticity (43% of normal-weight concrete’s value) in FC increases deflection by 22–46% and 11–15% for steel-FC and timber-FC floor systems, respectively. Overall, the outcome shows that FC can be an efficient alternative for mid-to-high-rise modular building floor construction. Its lightweight nature can reduce the module’s weight, making modular construction more cost-effective.

Proposing new adhesive-free timber edge connections for cross-laminated timber panels: A step toward sustainable construction

The use of timber as a building material is becoming increasingly popular thanks to its superior environmental performance compared with concrete and steel. However, timber structures rely on solid connections to improve their weak expansibility. Steel connections can be prone to corrosion over time, leading to the decreased structural integrity. Additionally, steel connections require more material and energy to manufacture and install compared with timber connections. This article focuses on the flexural performance of cross-laminated timber (CLT) panels with adhesive-free edge connections under four-point bending tests. First, numerical models of experimentally tested CLT panels were constructed using the finite element (FE) software ABAQUS. Then, these FE models were validated with the comparisons of their results with those of the experimental tests. Afterward, four new adhesive-free edge connections using timber for the CLT panels were developed in this study, helping sustainable construction. Utilizing the designed edge connections of the current study, forty-one parametric studies were numerically conducted on the connected CLT panels to investigate their ultimate loads, strains, displacements, moment capacities, failure modes, and effective stiffness. The factors affecting the edge connections’ load-bearing capacity were also examined and discussed. The study provides helpful insights into the development of CLT as a sustainable construction material with improved adhesive-free edge connections.

Flexural performance of round-ended concrete-filled steel tubular specimens

Round-ended concrete-filled steel tubular (CFST) columns have numerous benefits, including easy construction, aesthetic appearance, and variable section arrangement. This study experimentally and numerically investigated the flexural behavior of round-ended CFST columns. The six testing results showed that as the aspect ratio increased from 1.38 to 1.86, the flexural resistance and stiffness increased by 82.0% and 159.9%, respectively. Every round-ended CFST specimen had excellent ductility. Concrete can be adequately confined by the round-ended steel tube. Mechanistic and parametric analyses were carried out using a finite element model. Mechanistic analysis demonstrated that the round segment of the steel tube can effectively confine the concrete, resulting in a considerable strength gain near the edge of the compression zone. The parametric analyses showed that as the concrete strength increased from 24 to 110 MPa, the flexural resistance increased by average 20.4%; as the steel strength improved from 235 to 700 MPa, the flexural resistance increased by average 155.4%; as the steel ratio enhanced from 0.05 to 0.2, the flexural resistance increased by average 179.7%; and as the aspect ratio increased from 1 to 3, the flexural resistance of the major (minor) axis increased (decreased) by about 59.9% (36.5%). The analysis showed that the flexural stiffness of this composite specimen can be accurately predicted by AISC 360–2016. Finally, a simplified model was proposed for estimating the flexural resistance of the round-ended CFST specimens.

Flexural performance and damage evolution of multiple fiberglass-reinforced UV-CIPP composite materials-- A view from mechanics and energy release

Fiberglass-reinforced ultraviolet cured-in-place pipe (UV–CIPP) composite material is one of the most trenchless materials for underground pipelines’ rehabilitation. In this paper, the bending resistance and damage evolution mechanism of glass fiber-reinforced UV-CIPP composites were investigated under the influence of glass fiber structure, the number of layers of glass fibers, the angle of fiber layups, and the thickness of the material by high-definition video, SEM and infrared thermal imaging. The results indicate that the damage evolution modes of UV-CIPP materials mainly include: (1) fiber pull-out and overall fiber bundle tensile failure caused by strong interfacial bonding, (2) fiber/matrix debonding and delamination, fiber fracture, and matrix cracking caused by weak interfacial bonding. Furthermore, among the seven different fiberglass structures of UV-CIPP materials, the [0°/90°] warp-knit axial/short-cut felt fiberglass fabric exhibit the best flexural performance, with a bending strength of 412 MPa and a bending modulus of 16.1 GPa for the 4 layers glass fiber fabric. Moreover, in the bending process of UV-CIPP materials, the surface temperature rises primarily due to fiber break, the temperature transition aligning with the stress transition. Finally, the energy release is mainly caused by the failure of the glass fibers, but the resin contributed comparatively little. This study provides a scientific reference for the structural design and optimization of UV-CIPP materials.

Flexural performance investigation of steel-concrete composite beams strengthened with prestressed CFRP tendons in the negative bending moment region

To enhance the flexural performance of steel-concrete composite beams in the negative moment region, an external prestressing technique utilizing Carbon Fiber-Reinforced Polymer (CFRP) tendons was implemented for reinforcement. This article designed and manufactured 6 test beams for static load testing, and compared the changes in mechanical properties of the test beams before and after reinforcement, such as failure mode, deflection, CFRP tendons stress increment, strain, and cracks. A specific focus was given to exploring the impact of varying prestressing levels and the quantity of CFRP tendons on the flexural performance of composite beams in the negative moment region. Based on the plastic hinge theory, a new calculation model for the flexural bearing capacity of externally prestressed CFRP tendon-reinforced composite beams was established. The use of externally prestressed CFRP tendons reinforcement has a significant reinforcement effect, which can improve the elastic working range and ultimate bending bearing capacity of the composite beam in the negative bending moment zone, and effectively limit the development of concrete slab cracks in the negative bending moment zone. Theoretical values obtained from the proposed model in this study showed good agreement with experimental values, enabling accurate calculation of the incremental stress in externally prestressed CFRP tendons and the ultimate bearing capacity of composite beams. The study also provides a reasonable range for controlling the prestress level of CFRP tendons, which can serve as a reference for practical engineering design.

Flexural performance of sustainable hybrid fibre-reinforced SCC beams made of treated recycled aggregates

Flexural performance of sustainable hybrid fibre-reinforced SCC beams made of treated recycled aggregates

Effect of interface treatment on the flexural performance of existing RC bridge beams strengthened with UHPC

As one of the most innovative cement-based materials, ultra-high performance concrete (UHPC), with excellent durability and mechanical properties, has been widely used in strengthening existing bridges. In this study, in-situ four-point bending tests were carried out to investigate the flexural behavior of precast reinforced concrete (RC) hollow slab beams in service for 15 years strengthened with UHPC. Among them, three hollow slab beams were strengthened with UHPC, and the interface treatment was chiseling, planting rebars, and a combination of chiseling and planting rebars, respectively. The remaining one without any strengthening treatment was used as the control specimen. To evaluate the enhancement effect of different interface treatments on UHPC-strengthened beams, the cracking load, ultimate load, crack development and failure modes of UHPC-strengthened beams were analyzed. Results indicated that the stiffness, deflection capacity and flexural capacity of UHPC-strengthened beams was significantly improved. Meanwhile, the stiffness of UHPC-strengthened beams in the pre-damage stage was increased by 49%–94%, when compared with the unstrengthened beam. Correspondingly, the ultimate flexural capacity was increased by 29%–38%. The interface chiseling treatment was more favorable to enhance the deformation capacity of UHPC-strengthened beams. The interface planting rebar treatment was more favorable to enhancing the ductility of UHPC-strengthened beams. The crack development was effectively suppressed by the interface chiseling and planting rebars together. This contributes to a higher load capacity reserve for UHPC-strengthened beams. The bearing capacity under serviceability limit state of the UHPC-strengthened beams was increased by 1.25, 2, and 2.5 times through the interface treatments of chiseling, planting rebars, and a combination of both, respectively.

Reliable design rules for cold-formed ferritic stainless steel closed built-up beams

In the companion paper, test results were presented to explore the flexural performance of cold-formed ferritic stainless steel (FSS) closed built-up beams. Each specimen was fabricated by joining two lipped channels in a face-to-face configuration and securing them with spot welds at intermediate points along the beam span. Sectional aspect ratio, compression flange’s sectional slenderness and moment gradient were the key parameters varied to explore their influence on the flexural response of such members through tests. The current paper establishes a simplified finite element (FE) model of cold-formed FSS closed built-up beams and verifies it against the test results. Further, an extensive parametric study is carried out using the validated FE model to generate a large pool of data points. A wider database comprising of test results, numerical results obtained from this study and numerical results available in the companion paper were used to critically examine the adequacy of the current Australian Specifications (AS/NZ), American Standard (SEI/ASCE-8), European Code (EN 1993-1-4), Modified Eurocode approach suggested by Gardner and Theofanous, and Direct Strength Method (DSM) in North American Specification (AISI-S100: 2016), Modified DSM approach proposed by the authors in the literature and Continuous Strength Method (CSM) for cold-formed steel (CFS) flexural members. This makes the current study the first to extensively assess the accuracy of the various design guidelines available in the codes and other relevant literature, which explicitly highlighted their grave limitations. Accordingly, through suitable modifications and recommendations, new design rules are proposed to reliably and safely predict the flexural capacity of cold-formed FSS closed built-up beams.

Epoxy-based CFRP composites with induced single and multiple delaminations: flexural performance under four-point loading using digital image correlation

ABSTRACT The present work explores the effect of induced single and multiple circular delamination(s) on both the strength and stiffness of carbon/epoxy composite laminate subjected to pure bending. The laminates consisted of stacking sequence [0/0/45/-45/90/45/-45/90]S. They were manufactured using the hand layup method and vacuum bagging technique. The composites contained delamination(s) at the centre. The multiple delaminations have different sizes. They were inserted in a triangular pattern. Flexural tests were conducted in displacement control mode. The intact composite failed without delamination. The existence of multiple delaminations highly deteriorated the structural integrity and as a result the flexural properties decreased as compared to composites containing single delamination. Plies of the delaminated composite beams buckled locally on the compression side. Hence, the local out-of-plane displacement at the centre of the defect was measured using 3D DIC. The local out-of-plane displacement was higher in composites of induced multiple delaminations. Additionally, surface displacements and strains were measured at the region of interest. The causes of degradation in flexural performance and damages are also explained in detail.