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As an environmentally friendly new method for coating removal, laser cleaning has been widely used in aircraft skin paint removal recently. However, due to the thermal damage sensitivity of composite materials, current laser cleaning is still mainly used in aluminum alloy skins. In this work, we demonstrate a method for cleaning the surface paint of honeycomb sandwich structures by ultraviolet picosecond laser. The method achieves layer-by-layer and non-destructive removal of paint from composite surfaces. The results show that the top coat is selectively removed when the laser power is 8 W and the scanning speed is 1750 mm/s. When the laser power is 8 W and the scanning speed is 750 mm/s, both top coat and primer are completely removed without any morphological damage for the glass fiber. The temperature monitoring results show that the UV picosecond laser exhibits low-temperature paint removal. The paint removal mechanism of UV picoseconds is dominated by photochemical effects.

Glass fibers reinforced polymer (GFRP) were used to longitudinally and transversally 12 columns and while the other 4 columns were reinforced with steel or steel and GFRP as reference specimens. This research dealt with several parameters under different loading conditions, such as the reinforcing material and spacing between ties. This study aims to find out the ability of the reinforced columns with GFRP to bear the loads. In addition, investigate the mode of failure in these columns and their appropriateness in the structures since the columns are compression members. The tested results revealed that the concentric loading columns give higher resistance than their eccentrically loaded counterparts. Also, the hybrid column (steel and GFRP) had the highest peak load compared with the fully reinforced steel and GFRP columns. In addition, the fully GFRP RC- column had an ultimate load slightly less than its steel counterpart under the same loading condition.

The aim of this study is to investigate the behavior of RC concrete beams reinforced with basalt, carbon, glass fiber reinforced polymer bars and conventional steel. A comparison between the results has been performed to investigate and study the effect of fire on reinforced concrete beams considering the following items: (flexural capacity, deflection behavior and crack pattern). It is noticeable that the use of FRP bars significantly increased the ultimate load of the specimens, where the percentage of increase ranged between 34 - 73 % of the ultimate load of the specimen C-S under static load. The greatest ultimate load was reached the beam that was reinforced with carbon bars (CFRP). It was also noticed able that the use of FRP rods significantly increases the deflection of the beams. The percentage of increase was between 45 - 170 % of the final deflection of the C-S specimen under static load. It was noted that the effect of the fire on the beams reinforced with fiber bars (FRP), where the efficiency of bearing capacity of beams after fire decreases by 11 to 18 % of the actual efficiency of bearing capacity of beams control. As for the beam reinforced with conventional steel bars, its efficiency was reduced by 15 % from the actual capacity.

This paper presents a comprehensive study focused on evaluating the strain generated within short concrete columns reinforced with glass-fiber-reinforced polymer (GFRP) bars and spirals under concentric compressive axial loads. This research was motivated by the lack of sufficient data in the literature regarding strain in such columns. Five full-scale RC columns were cast and tested, comprising four strengthened with GFRP reinforcement and one reference column reinforced with steel bars and spirals. This study thoroughly examined the influence of various test parameters, such as the reinforcement type, longitudinal reinforcement ratio, and spacing of spiral reinforcement, on the strain in concrete, GFRP bars, and spirals. The experimental results showed that GFRP–RC columns exhibited similar strain behavior to steel–RC columns up to 85% of their peak loads. The study also highlighted that the bearing capacity of the columns increased by up to 25% with optimized reinforcement ratios and spiral spacing, while the failure mode transitioned from a ductile to a more brittle nature as the reinforcement ratio increased. Additionally, it is preferable to limit the compressive strain in GFRP bars to less than 20% of their ultimate tensile strain and the strain in GFRP spirals to less than 12% of their ultimate strain to ensure the safe and reliable use of these materials in RC columns. This research also considers the prediction of the axial load capacities using established design standards permitting the use of FRP bars in compressive members, namely ACI 440.11-22, CSA-S806-12, and JSCE-97, and underscores their limitations in accurately predicting GFRP–RC columns’ failure capacities. This study proposes an equation to enhance the prediction accuracy for GFRP–RC columns, considering the contributions of concrete, spiral confinement, and the axial stiffness of longitudinal GFRP bars. This equation addresses the shortcomings of existing design standards and provides a more accurate assessment of the axial load capacities for GFRP–RC columns. The proposed equation outperformed numerous other equations suggested by various researchers when employed to estimate the strength of 42 columns gathered from the literature.

In our investigation, we subjected eleven reinforced concrete beams to a four-point bending system to explore the impact of varying fibre and ferrocement contents on their structural behaviour. These beams, measuring 1.7 m in length, featured a rectangular cross-section with dimensions of 150 mm by 300 mm. Our study focused on three key variables: steel fibre content (at levels of 0.5%, 1%, and 1.5%), glass fibre content (also at 0.5%, 1%, and 1.5%), and ferrocement content (evaluated with one or two layers of welded or expanded wire mesh). Our findings revealed that incorporating fibres with minimal shear reinforcement significantly enhanced the beams’ performance. Specifically: The specimen reinforced with 1.5% steel fibres exhibited the highest ultimate failure load, surpassing the control beam by an impressive 41.87%. The 0.5% glass fibre specimen experienced the least deflection at the ultimate load compared to the control beam. The 1.5% glass fibre specimen demonstrated superior energy absorption compared to the control specimen. Notably, using two layers of welded wire mesh proved most effective in enhancing the ultimate failure load when compared to both the control specimen and other ferrocement-strengthened beams.

Hollow structures reduce weight without compromising load-bearing capacity and are widely used. The new Glass-Fiber-Reinforced Polymer high-strength thin-walled inner mold simplifies internal cavity construction and boosts structural performance. This study first investigates the influence of a GFRP high-strength thin-walled circular tube on the cross-sectional load-carrying capacity of hollow slabs. Then, a formula for the bending load-carrying capacity of the section under the action of the tube is derived. The results indicate that when the height of the concrete compression zone meets certain conditions, GFRP high-strength thin-walled circular tubes can improve the ultimate load-carrying capacity of the hollow floor slabs. In order to achieve a more economical design, the bending moment modification of a GFRP high-strength thin-walled circular tube of a continuous slab was studied. Research has found that the bending moment modulation limit for a continuous slab is 35.65% when it is subjected to a load of Pu=24 kN. Experimental analysis has shown that the results are generally consistent with the calculations. In practical engineering, the application of a GFRP high-strength thin-walled circular tube of continuous slabs has limitations. Therefore, this study investigated a GFRP high-strength thin-walled honeycomb core slab and found that its ultimate load-bearing capacity is greater compared to waffle slabs. In addition, the stress performance of the GFRP high-strength thin-walled honeycomb core internal mold is superior, making it more promising for practical applications.

3D printers have been the focus of many researchers in recent years. Many thin-walled structures can be produced using 3D printers. One of the thin wall structures that can be made with 3D printers is the core of sandwich panels. In this research, cores with rectangular cross section have been made using Acrylonitrile Butadiene Styrene (ABS) and Polylactic Acid (PLA) filaments. These cores were reinforced using aluminum and composite face sheets and subjected to a three-point bending test. Glass fibers with a density of 200 g/m2 were used to make composite shells. The results showed that the addition of aluminum and composite face sheets, although increasing the flexural strength, greatly reduces the flexibility of the core.

The concrete in tension zone of traditional reinforced concrete bridge deck is liable to crack under vehicle loading, leading to easy corrosion of the internal steel rebars and earlier appearance of bridgevvv disease. This study proposes a novel waffle-type UHPC-GFRP composite slab that can solve the cracking problem of traditional concrete bridge decks. The GFRP grid was partially embedded in the UHPC to transfer the shear force between the grid and UHPC. The remainder of the GFRP grid was exposed to form a ribbed structure similar to a ''waffle plate''. Five composite slab tests were conducted to investigate the mechanical properties of the proposed composite slab. Accordingly, the influences of the shear span-to-depth ratio, thickness of the UHPC layer, and embedded depth of the GFRP grid on the bending behavior of the composite slab were considered. The experimental results revealed three failure modes of the composite slabs: bending failure (the ultimate bending capacity of 81.1 kN), shear failure (the ultimate shear capacity of 147.8 kN), and GFRP interlaminar shear failure (the ultimate bearing capacity of 167.2 kN). The change in the shear span-to-depth ratio directly affected the failure mode of the composite slab. More specifically, the embedded depth of the GFRP grid increased by 10 mm, the cracking load and ultimate strength of the composite slab increased by 23.8% and 46.6%, respectively. Lastly, a calculation method for the new waffle-type UHPC-GFRP composite slab is proposed, and the calculation error is controlled to be within 12%.

In order to effectively mitigate the risk of bird strikes, it is imperative that radomes situated in areas prone to such incidents possess the capability to endure the impact loads caused by bird collisions. Additionally, these radomes must maintain their electromagnetic transparency. Therefore, glass fibre reinforced polymer (GFRP) with Nomex honeycomb sandwich material is used for radome structural design. The current research is intended to examine the dynamic behavior of sandwich composite panels in order to determine the penetration velocity by testing them at three distinct bird impact velocities, such as 88 m/s, 135 m/s, and 153 m/s. It is necessary to find the velocity at which the bird will penetrate / rupture the radome for the safety of Antenna / Electronic units mounted behind the radome. Finite element explicit code LS-DYNA simulates all three impacts. Extension of the simulation estimated the threshold bird impact velocity to be 146 m/s at which it penetrates the sandwich panel under fixture-controlled boundary condition.

Glass fiber‐reinforced polymer (GFRP) is formed with glass fiber as the reinforcing material and resin as the matrix. It is widely used in wind turbine blades because of its lightweight, high strength, and corrosion resistance properties. Herein, a method to prepare superhydrophobic GFRP surfaces by femtosecond laser direct writing combined with fluoroalkylsilane modification is demonstrated. The prepared GFRP surface has excellent superhydrophobicity with contact angle of 163.9° and sliding angle of 3.8°. In the ice resistance tests, the icing delay time is extended from 33 to 273 s at −5 °C. The ice adhesion strength is reduced from 217.4 to 40.3 kPa. The surface still has superhydrophobicity and ice adhesion strength of less than 100 kPa after ten cycles of the test. The laser exposure conditions are optimized for water/ice repelling and are at high intensity of 4 TW cm−2 pulse−1 and 2.5 m s−1 beam travel speed, which make the presented approach efficient for fabrication over industrially large areas. [ABSTRACT FROM AUTHOR]

This study presents an experimental framework with seventeen beams to investigate the impact of loading type, configuration, and through-bolt anchorage on LC-GFRP (Low-Cost Glass-Fiber-Reinforced Polymer) confinement performance. Beams underwent three-point and four-point bending, with LC-GFRP applied in various ways, including U-shaped, side-bonded, and fully wrapped, with and without anchors. The performance of LC-GFRP was compared to CFRP (Carbon-Fiber-Reinforced Polymer) and sisal wraps. LC-GFRP in side-bonded and U-shaped configurations without anchors under three-point bending showed no shear failure, while those under four-point bending without anchors experienced shear failure. With anchors, U-shaped configurations successfully prevented shear failure. The side-bonded, U-shaped, and U-shaped configurations along the full span with anchors demonstrated peak capacity enhancements of 72.11%, 43.66%, and 68.39% higher improvements than the corresponding configurations without anchors, respectively. Wrapping all sides of the beam with LC-GFRP or CFRP prevented shear failure without additional anchors, with complete wrapping being the most efficient method. When anchors were used, significant capacity enhancements were observed. Existing shear strength prediction models were evaluated, highlighting the need for more tailored expressions for LC-GFRP confinement, especially for non-U-shaped configurations. [ABSTRACT FROM AUTHOR]

The use of fiber reinforced composite materials (FRP) has increased in many areas. These materials need to be processed with some machining methods according to their usage areas, but their machinability is difficult. In this study, surface roughness (SR), delamination factor (Fd) and thrust forces were investigated in the drilling of glass fiber reinforced composite material (GFRP) produced by pultrusion with a coated and uncoated drill. Microstructures of chips formed during drilling were investigated and their effects on surface roughness were determined. Three different cutting speeds (60, 70, 80 m/min) and feed rates (0.06, 0.09, 0.12 mm/min) were selected as machining parameters. At the end of the study, it was found that feed rate had a more significant effect on surface roughness, delamination factor and thrust force. It was observed that as the cutting speed increased, the surface roughness, thrust force and delamination factor decreased. The lowest thrust force and Fd occurred at a cutting speed of 80 m/min and a feed rate of 0.06 mm/min. However, the lowest SR was obtained at a cutting speed of 70 m/min and a feed rate of 0.06 mm/min.Better results were obtained with TiN coated drills compared to uncoated drills. [ABSTRACT FROM AUTHOR]

This study investigates the high-strain-rate impact performance of glass-fiber-reinforced polymer (GFRP) fabric that is impregnated with a shear thickening fluid (STF) and reinforced with multiwalled carbon nanotube (MWCNT) particles. Impact tests were conducted on four GFRP-STF and twelve GFRP-MWCNT/STF composite specimens under four strain rates using a split Hopkinson pressure bar apparatus. The MWCNT/STF specimens were synthesized by dispersing 0.4 wt%, 0.8 wt%, and 1.2 wt% MWCNT nanoparticles in silica-based STF (20.0 wt%). Scanning electron microscopy images confirmed that multiple silica and MWCNT nanoparticles adhered to GFRP fibers and filled the spaces between the fibers. In addition, MWCNT improved the peak viscosity of silica-based STF and degraded the elastic and storage moduli at high strain rates. Split Hopkinson pressure bar testing revealed that GFRP-MWCNT/STF had a significant strain-rate-dependent effect on the peak stress and energy absorption, which was most significant before the failure of the specimen. Compared with GFRP-STF, 0.8% MWCNT/STF improved the peak stress and energy absorption of GFRP by up to 99.4% and 57.1%. Increasing the MWCNT mass fraction improved the peak stress and energy absorption of GFRP-MWCNT/STF and significantly improved the secondary energy absorption capacity, especially when the strain rate was small. In particular, the maximum increase was 41.2%. [ABSTRACT FROM AUTHOR]

In this study, we produced Aluminum oxide (Al2O3) reinforced carbon fiber and glass fiber reinforced polymer (CFRP, GFRP) composites and investigated mechanical and tribological properties. Al2O3 was dispersed in epoxy resin using a mechanical stirrer. The composites are produced via the hand lay-up method and dried at room temperature for 48 hours. The properties of composites were determined via Archimedes' method, flexural, impact, hardness and wear tests. The highest flexural strength and hardness were found at 946.3 MPa and 48.7 HBA for 3 wt.% Al2O3 reinforced CFRP, respectively. The highest impact strength was observed at 187.4 kJ/m2 for an un-reinforced GFRP composite. The lowest Coefficient of Friction (COF) and wear depth was found 3 wt.% Al2O3 reinforced GFRP composites. [ABSTRACT FROM AUTHOR]

Glass fibre reinforced polymer (GFRP) has excellent material properties such as light weight and corrosion resistance, and has been applied to bridge appendages such as wall railings. In this case, bent L‐shaped steel members (bent members) are used at the joints with the floor slab. The GFRP wall railings were designed to consider the wind loads acting on them, and the bolt holes for the anchor bolts were slotted hole for ease of installation. In this study, the effects of loading conditions and bolt arrangement of anchor bolts slotted holes in the performance of the joint structure were analytically investigated for the base joints of GFRP wall railings. The results presented that, in the initial stiffness of the base, the loading condition was smaller for the negative loading than for the positive loading, and the bolt arrangement was smaller on the outside than on the inside. It is shown that the incremental bolt axial force of the anchor bolts is borne by four bolts in the positive loading, however, is biased to only two bolts in the negative loading, focusing on the neutral axis position. [ABSTRACT FROM AUTHOR]

This research aims to address a post-earthquake urgent strengthening measure to enhance the residual seismic capacity of earthquake-damaged reinforced concrete wall structures with coupling beams. The study consists of a series of tests on half-scale prototype coupling beams with various detailing options, including confined with reduced confinement, partially confined, and unconfined bundles, under cyclic loading conditions. The methodology employed involved subjecting the specimens to displacement-controlled reversal tests, and carefully monitoring their response using strain gauges and potentiometers. The main results obtained reveal that GFRP wrapping significantly enhances the seismic performance of earthquake-damaged coupling beams, even in cases where specimens experienced strength loss and main reinforcement rupture. The strengthened beams exhibit commendable ductility, maintaining high levels of deformation capacity, and satisfying the requirements of relevant seismic design codes. The significance of the study lies in providing valuable insights into the behavior and performance of damaged coupling beams and assessing the effectiveness of GFRP wrapping as a rapid and practical post-earthquake strengthening technique. The findings can be particularly useful for developing urgent post-earthquake strengthening strategies for high-rise buildings with structural walls. The method may be particularly useful for mitigating potential further damage in aftershocks and eventual collapse. In conclusion, this study represents a significant advancement in understanding the post-earthquake behaviors of coupling beams and provides valuable guidance for practitioners in making informed decisions regarding post-earthquake strengthening projects. The findings contribute to the overall safety and resilience of structures in earthquake-prone regions. [ABSTRACT FROM AUTHOR]

The present work studies the response to hygrothermal ageing of natural fibre composites (NFCs) against synthetic fibre composites when using three different types of polymers as matrices. For ageing, coupons were fully immersed in distilled water at 23, 40, and 60 °C for a total ageing period of 56 days. Flax fibre-reinforced composites, using two recyclable polymer systems: (i) a bio-based recyclable epoxy and (ii) an acrylic-based liquid thermoplastic resin, were tested against conventional glass fibre-reinforced composites employing a synthetic (petroleum-based) epoxy. Different fibre/polymer matrix material combinations were tested to evaluate the effects of hygrothermal ageing degradation on the reinforcement, matrix, and fibre/matrix interface. The hygrothermal ageing response of unaged and aged composite coupons was assessed in terms of flexural and viscoelastic performance, physicochemical properties, and microscopy (SEM—Scanning Electron Microscopy). [ABSTRACT FROM AUTHOR]

This study focuses on the fatigue behaviour analysis of glass fibre-reinforced polymer (GFRP) composite specimens under high-cycle fatigue loading conditions. Therefore, property validation is recommended in the material development process upon further investigation of the fabricated GRFP. This study aims to evaluate the behaviour of the fabricated GFRP fatigue specimen when subjected to high-cycle fatigue loads and compare it to existing studies. A GFRP fatigue test sample was fabricated using the hand layup process into a flat rectangular panel, which was then cut into a small dimension of 28×2×0.2 cm fatigue specimen. Fatigue tests were performed on five flat specimens at different constant amplitude loads or stress levels between 40% and 80% of ultimate tensile strength to obtain the stress-life curve for the fabricated GFRP. Results showed that the high-stress levels of 80% contributed to the most reduced fatigue life cycle of GFRP. This result is consistent with previous studies and lies within the published life cycle range, validating the fabricated GRFP. A new parameter called the failure modulus, or Mf, may be used to quantify a particular set of fatigue tests. [ABSTRACT FROM AUTHOR]

With the emergence of slimmer footbridges and the introduction of lighter materials, the challenge of vibrational comfort assessment becomes more and more relevant. Previous studies have shown that each pedestrian will act both as an inducer and a damper, referred to as human–structure interaction. However, this interaction is currently not implemented in design guidelines, which leads to a poor comfort estimation for small lightweight footbridges. Derived from smartphone-based vibration measurements, this paper provides an overview of the modal parameters at various pedestrian densities and a comfort assessment of a selection of simply supported GFRP and steel lightweight footbridges in Flanders. The results indicate that the initial structural damping ratios for GFRP bridges exceed the values set in design guidelines and that they increase with an increasing pedestrian density. Further, it is shown that the measured accelerations do not relate proportionally to the pedestrian density. From both results the relevance of human–structure interaction is confirmed. Finally, while the first natural frequency is analytically predicted accurately, the vertical accelerations are substantially overestimated. Here, a better estimation can be made based on the experimentally measured damping ratios. The results contribute to a better understanding of human–structure interaction and the vibration assessment of lightweight footbridges. Practical applications include optimizing footbridge design, focussing on better performance and improving safety and user experience. [ABSTRACT FROM AUTHOR]

The safety of civilian and military infrastructure is a concern due to an increase in explosive risks, which has led to a demand for high-strength civil infrastructure with improved energy absorption capacity. In this study, a Finite Element (FE) numerical model was developed to determine the effect of hybrid Fibre Reinforced Polymer (FRP) as a strengthening material on full-scale Reinforced Concrete (RC) slabs. The reinforcing materials under consideration were Carbon (CFRP) and Glass (GFRP) fibres, which were subjected to blast loads to determine the structural response. A laminated composite fabric material model was utilized to model the failure of composite, which facilitates the consideration of strain rate effects. The damaged area of the laminate is determined in the FE model, and it is in good agreement with the corresponding experimental results in the literature. Models containing different stacking sequences were built to demonstrate their efficiency in resisting blast loads. In general, the damaged area was reduced when a hybrid reinforcement with CFRP as the top layer was used. [ABSTRACT FROM AUTHOR]

The primary goal of this research is to examine the effect of loads, sliding velocity, and sliding distance on CNT added glass fibre reinforced polymer composite sliding in the inert gas condition. The wear performance of the CNT added GFRP composite sliding towards the steel alloy wheel was analysed by important tribological parameters. The results clearly show the subjective influences of the wear parameters and their impact on the rate of wear and the coefficient of friction (COF). The Response Surface Methodology (RSM) confirms the potential spectrum of responses. Also, it defines the optimum value of process factors like applied load, sliding distance, and sliding velocity, which results in a decreased response over the long life of the composite applied. The optimum solution for wear rate and COF, predicted using the design of experiment (DOE) technique in conjunction with the RSM methodology, allows users to choose the appropriate wear rate and COF combination. The asperities on the disc and the pin are well separated under inert gas conditions. Furthermore, because asperity contacts provide the least frictional heat, the development of wear debris is significantly delayed. As a result, the COF and wear rate are both at their lowest. [ABSTRACT FROM AUTHOR]

A high strength-to-weight ratio, stiffness, fatigue resistance, a low coefficient of thermal expansion, and tailorable properties make glass-fibre-reinforced plastic (GFRP) a popular choice for a wide range of applications, including aircraft structures, automobile chassis, and shipbuilding. However, milling GFRP composites is challenging because of their heterogeneous nature and two-phase structure, which lead to high cutting forces and delamination. A statistical experiment was carried out using the Taguchi design of experiments to investigate the effect of machining settings on GFRP composite performance metrics such as surface delamination, surface roughness, and material removal rate. The L27 orthogonal array was used for the experiment, and it served as the foundation for the choice of material, input variables, levels, and output response variables. The experiment's outcomes were analysed using MINITAB software® 18 Version and the Analysis of Variance (ANOVA) method. Based on the signal-to-noise (S/N) ratio, the ideal conditions were selected, and confirmation studies were carried out to ensure their applicability. In order to identify the ideal circumstances for the manufacturing and machining parameters, the data were normalised to a range from zero to one. To overcome the difficulties involved in milling GFRP composites, a thorough investigation and optimisation of the manufacturing process factors and machining settings is essential. [ABSTRACT FROM AUTHOR]

This paper examines the punching shear behavior of a new concrete flat slab design, incorporating a glass fiber-reinforced polymer (GFRP) stay-in-place (SIP) structural form system and orthogonal GFRP top rebar mesh. The SIP form system comprises I-beams supported on the four sides of a column and flat plates with T-up ribs supported by, and adhesively bonded to, the bottom flanges of the I-beams. The web and top flange of the I-beams are embedded in the slab, thereby providing flexural and shear reinforcement, while the SIP ribbed plates provide the bottom reinforcement. Four full-scale interior slab–column specimens, 2000 × 2000 × 200 mm3, were tested under axial compression applied to the column. The slabs have a central 300 × 300-mm square column extending 300 mm on either side of the slab. The study assessed the contributions to punching shear strength of different components of the GFRP system. The new design experienced a 29% higher punching shear strength than the control slab with GFRP rebar only, and was much more ductile. The load dropped gradually over a large range of deflection, increasing the ductility index from 1.6 in the control slab to 3.1 in the slab incorporating the new design. An analytical model is developed for punching shear strength, accounting for concrete contribution and flexural and web contributions of I-beams. Results agreed with experimental strength, within −6% to +13%. A parametric study examined a range of rebar reinforcement ratios, different GFRP I-beam sizes and a comparable steel I-beam. [ABSTRACT FROM AUTHOR]

Compared to the traditional thermal curing method, ultraviolet light-curing can effectively avoid the problems of long curing time and complicated curing equipment. In this paper, a geometric and physical model of the light-curing process of the glass fiber reinforced composite multilayer laminate is established based on the theory of optics and curing kinetics, considering the propagation of ultraviolet light in the laminate is affected by the interlayer during the light-curing process. The meta-analysis method is adopted to calculate and predict the changes in the curing degree, temperature, and stress fields during the light-curing process of glass fiber composites, which also analyzes and summarizes the multi-field distribution and its variation law during the process. By comparing the experimental data with the predicted results, the model's accuracy is verified, and the causes of errors are analyzed, providing an efficient analysis method to investigate the composite light-curing. [ABSTRACT FROM AUTHOR]

Although GFRP poles are widely accepted today due to their low cost and weight and high electrical and corrosion resistance, they suffer large deformations due to the low elastic and rigidity moduli (E & G) values of the GFRP. Accordingly, it is essential to accurately measure these values to estimate the actual deformation of the pole. This study presented a procedure to measure (E & G) values using three different tests on three sample sizes: full, scale pole, conic sample, and ad coupon sample, instead of using the manufacturer values as usual. This study is also concerned with the shear modulus value and when it can be neglected as usual in other traditional materials. The GRG optimization technique was used to analyze the results and determine the optimum values for (E & G) considering the results of the three tests. The results showed that the values of (E & G) are greatly affected by the sample's size and shape, the slenderness ratio of the sample (L/r), and the shear deformation contribution. The critical slenderness ratio (L/r), corresponding to a shear deformation contribution of 10%, was determined for each test. This value is recommended as the upper boundary for any test that measures the (E & G) values. Testing several samples with different (L/r) values is also recommended to enhance accuracy. This study was concerned with determining the optimum values of elastic and rigidity moduli for GRFP poles compared to the manufacturer's conservative values. The results indicated that the shear modulus can be neglected and the importance of the scale effect on the results of flexure and shear modulus. [ABSTRACT FROM AUTHOR]

Abstract Fire-induced structural damage to the seismic performance of reinforced concrete shear walls is critical in the event of a fire-earthquake scenario. However, only few researchers have studied the seismic performance of reinforced concrete shear walls at high temperatures. This study focuses on the seismic performance of fiber reinforced concrete shear walls at high temperatures by using finite element (FE) software, ABAQUS. The experimental test available in a literature on seismic behavior of shear walls exposed to fire and thermal properties of glass fiber reinforced polymer (GFRP) bars were used to validate the FE model and showed good agreement and thus used in the simulation. The FE results showed that exposure of RC shear wall to fire reduced the strength of the wall. The strength of walls at the maximum applied drift of 3.2% with concrete cover thicknesses of 20 mm, 25 mm, and 30 mm was dropped by about 70%, 76%, and 85% of the reference shear wall, respectively. Similarly, the strength of RC walls was reduced by about 80%, 75%, and 68% of the reference shear wall for the duration of fire exposure of 30 min, 60 min, and 120 min, respectively. Additionally, the strength of walls due to one side, two sides, or all sides’ exposure to fire was decreased by about 68%, 56%, and 50% of the reference shear wall, respectively. It can generally be concluded that the fire exposure sides has largely affected the strength of the shear wall compared to the other parameters and GFRP bars were more sensitive to temperature than steel bars.

Dynamic loading on composite components may induce damages such as cracks, delaminations, etc. and development of an early damage detection technique for delamination prediction is one of the most important aspects in ensuring the integrity and safety of such components. The presence of damages such as delaminations on the composites reduces its stiffness and changes the dynamic behaviour of the structures. As the loss in stiffness leads to changes in the natural frequencies, mode shapes, and other aspects of the structure, vibration analysis may be the ideal technique for delamination prediction. In this research work, the supervised feed-forward multilayer back-propagation Artificial Neural Network is used to determine the position and area of delaminations in glass fiber-reinforced polymer (GFRP) plates using changes in natural frequencies as inputs. The natural frequencies were obtained by finite element analysis and results are validated experimentally. The findings show that the suggested technique can satisfactorily estimate the location and extent of delaminations in composite plates.

GFRP bars reinforced in submerged or moist seawater and ocean concrete is subjected to highly alkaline conditions. While investigating the durability of GFRP bars in alkaline environment, the effect of surrounding temperature and conditioning duration on tensile strength retention (TSR) of GFRP bars is well investigated with laboratory aging of GFRP bars. However, the role of variable bar size and volume fraction of fiber have been poorly investigated. Additionally, various structural codes recommend the use of an additional environmental reduction factor to accurately reflect the long-term performance of GFRP bars in harsh environments. This study presents the development of Random Forest (RF) regression model to predict the TSR of laboratory conditioned bars in alkaline environment based on a reliable database comprising 772 tested specimens. RF model was optimized, trained, and validated using variety of statistical checks available in the literature. The developed RF model was used for the sensitivity and parametric analysis. Moreover, the formulated RF model was used for studying the long-term performance of GFRP rebars in the alkaline concrete environment. The sensitivity analysis exhibited that temperature and pH are among the most influential attributes in TSR, followed by volume fraction of fibers, duration of conditioning, and diameter of the bars, respectively. The bars with larger diameter and high-volume fraction of fibers are less susceptible to degradation in contrast to the small diameter bars and relatively low fiber's volume fraction. Also, the long-term performance revealed that the existing recommendations by various codes regarding environmental reduction factors are conservative and therefore needs revision accordingly.

Glass fiber-reinforced polymer (GFRP) composite materials are widely used in many manufacturing industries due to their low density and high strength properties, and consequently, the need for precision machining of such composites has significantly increased. Since composite materials have an anisotropic and heterogeneous structure, the machinability of composite materials is quite different from conventional materials. In the machining of GFRP composite pipes, tool wear, cracks or delamination, a rough surface, etc., many unwanted problems may occur. Therefore, GFRP composite pipes are difficult to process. To prevent such problems, it is very crucial to select suitable process parameters, thereby achieving the maximum performance for the desired dimensional integrity. In this study, through turning of GFRP composites with different orientation angles (30°, 60°, and 90°), the effects of cutting speed (50, 100, and 150 m·min−1), feed rate (0.1, 0.2, and 03 mm·rev−1), and depth of cut (1, 2, and 3 mm) on cutting force and surface roughness were determined. Then, with the use of these machining parameters, a model of the system for determining cutting force and surface roughness was established with artificial neural networks (ANNs). The ANN was trained using Levenberg–Marquardt backpropagation algorithm. It has been observed that the results obtained with the ANN model are very close to the data found in experimental studies. In both experimental and model-based analysis, minimum cutting force (44 N) and surface roughness (2.22 µm) were achieved at low fiber orientation angle (30°), low feed rate (0.1 mm·rev−1), and depth of cut (1 mm) at high cutting speeds (150 m·min−1).

Epoxy R-Glass Fiber-Reinforced Polymer (GFRP) composite plates were hydrothermally aged at 60 °C for 23, 75, and 133 days. The water content reached 0.97 wt%, 1.45 wt% and 1.63 wt%, respectively. The studied GFRP matrix was inert to hydrolysis or chain scission, allowing for investigation of irreversible changes in the fiber-matrix interphase due to hydrothermal aging upon re-drying. During each period, a subset of the specimens was removed from the water bath and dried in a chamber. The weight loss upon drying was explained with epoxy leaching (impurities), sizing-rich interphase hydrolysis, glass fiber surface hydrolysis, accumulated degradation products escaping, and water changing state from bound to free. The influence of hydrothermal aging on the fiber-matrix interfacial properties was investigated. Lower interfacial strength of hydrothermally aged (wet) samples was attributed to plasticization of the epoxy, plasticization and degradation of the sizing-rich interphase (including formation of hydrolytic flaws), and hydrolytic degradation of the glass fiber surface. The kinetics of epoxy-compatible epoxysilane W2020 sizing-rich interphase hydrolysis provided an estimate of ca. 1.49%, 4.80%, and 8.49% of the total composite interphase degraded after 23, 75, and 133 days, respectively. At these conditions, the interface lost 39%, 48%, and 51% of its strength. Upon re-drying the specimens, a significant part of the interfacial strength was regained. Furthermore, an upward trend was observed, being 13%, 10% and 3% strength, respectively; thus, indicating a possibility of partial recovery of properties.

Glass Fiber reinforced polymers (GFRPs) are widely used and play an important role in modern society. The multilayer structure of GFRPs can lead to delamination defects during production and service, which can have a significant impact on the integrity and safety of the equipment. Therefore, it is important to monitor these delamination defects during equipment service in order to evaluate their effects on equipment performance and lifespan. Microwave imaging testing, with its high sensitivity and noncontact nature, shows promise as a potential method for detecting delamination defects in GFRPs. However, there is currently limited research on the quantitative characterization of defect images in this field. In order to achieve visual quantitative nondestructive testing (NDT), we propose a 2D-imaging visualization and quantitative characterization method for delamination defects in GFRP, and realize the combination of visual detection and quantitative detection. We built a microwave testing experimental system to verify the effectiveness of the proposed method. The results of the experiment indicate the effectiveness and innovation of the method, which can effectively detect all delamination defects of 0.5 mm thickness inside GFRP with high accuracy, the signal-to-background ratio (SBR) of 2D imaging can reach 4.41 dB, the quantitative error of position is within 0.5 mm, and the relative error of area is within 11%. [ABSTRACT FROM AUTHOR]

Prevention of mechanical and thermal damage to the composite parts is crucial during the debonding process of adhesive joints. This work highlights the impact of thermally expanded particles (TEPs) on bulk adhesive properties and the lap shear strength of adhesively bonded GFRP joints. FTIR studies revealed insignificant chemical changes occurring among the epoxy and its blend with TEPs. The addition of TEPs has slightly influenced the glass transition temperature (Tg) of adhesive. TMA showed that TEPs lose permanent expansion above maximum expansion temperature due to burst and/or diffuse of gas through the thin shell. DIC analysis of materials revealed that CTE mismatch grows with the addition of TEPs in x and y directions. Increases in TEP content up to 15 wt.% also raised the maximum dimension change in the epoxy adhesive. DMA and TGA studies indicated no major change in storage modulus and weight loss when GFRP was heated up to 170°C. The contact angle of GFRP decreased substantially after plasma surface treatment. Plasma surface treatment provided higher bond strength at room temperature than sandblasting surface treatment and prevented fiber-tearing. Despite the incorporation of TEPs, the enhanced debonding effectiveness at 145°C was marginal (less than 5%) for the epoxy adhesive used in the study. The incorporation of TEPs generated the residual stresses inside the adhesive as confirmed by measuring the residual strength of SLJ samples, especially 10 wt.% TEPs-epoxy joints exhibited more than 20% strength drop. [ABSTRACT FROM AUTHOR]

The work is aimed at studying the impact resistance of epoxy oligomer matrices (EO) modified with polysulfone (PSU) or polyethersulfone (PES) and glass fibers reinforced plastics (GFRP) based on them under low-velocity impact conditions. The concentration dependences of strength and fracture energy of modified matrices and GFRP were determined. It has been determined that the type of concentration curves of the fracture energy of GFRP depends on the concentration and type of the modifying polymer. It is shown that strength σ and fracture energy EM of thermoplastic-modified epoxy matrices change little in the concentration range from 0 to 15 wt.%. However, even with the introduction of 20 wt.% PSU into EO, the strength increases from 164 MPa to 200 MPa, and the fracture energy from 32 kJ/m2 to 39 kJ/m2. The effect of increasing the strength and fracture energy of modified matrices is retained in GFRP. The maximum increase in shear strength (from 72 MPa to 87 MPa) is observed for GFRP based on the EO + 15 wt.% PSU matrix. For GFRP based on EO + 20 wt.% PES, the shear strength is reduced to 69 MPa. The opposite effect is observed for the EO + 20 wt.% PES matrix, where the strength value decreases from 164 MPa to 75 MPa, and the energy decreases from 32 kJ/m2 to 10 kJ/m2. The reference value for the fracture energy of GFRP 615 is 741 kJ/m2. The maximum fracture energy for GFRP is based on EO + 20 wt.% PSU increases to 832 kJ/m2 for GFRP based on EO + 20 wt.% PES—up to 950 kJ/m2. The study of the morphology of the fracture surfaces of matrices and GFRP confirmed the dependence of impact characteristics on the microstructure of the modified matrices and the degree of involvement in the process of crack formation. The greatest effect is achieved for matrices with a phase structure "thermoplastic matrix-epoxy dispersion." Correlations between the fracture energy and strength of EO + PES matrices and GFRP have been established. [ABSTRACT FROM AUTHOR]

This experimental study investigated how defects, in particular fiber misalignment, affect the mechanical behavior of glass fiber composites (GFRP) under compressive loading. GFRP cross-plies with three different types of fiber misalignment, namely a fold, a wave, and an in-plane undulation, were fabricated using the resin transfer molding process. The compressive tests were performed at four different temperatures, in order to investigate the role of a change in the matrix properties on the strength of the composite. The experiments showed that the defects, especially at lower temperatures, had a significant impact on the mechanical properties of the composite, exceeding the proportion of the defects inside the composite. With increasing temperature, the damage mechanism changed from fiber-dominated to matrix-dominated and, in doing so, decreased the significance of fiber misalignment for the mechanical behavior. [ABSTRACT FROM AUTHOR]

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The application of composites in various industries has grown considerably. The relatively high cost of Low-Velocity Impact (LVI) tests and the limitation in data collection due to the short time of this test, on one hand, and previous reports of the conformity of Quasi-Static Indentation (QSI) test results to LVI test results, on the other hand, have convinced researchers to use QSI instead of LVI. The present research investigates the effect of various percentages of nanoclay (because of their cost-effectiveness) on the impact properties of glass-epoxy composite and has used the QSI test to predict the behavior of this nano-composite. For the homogeneous distribution of nanoclay in the resin, a mechanical and an ultrasonic stirrer were used, and the EDAX image of the nano-resin cross-section confirms the success of this process. The QSI test results showed that adding 3% nanoclay to the glass-epoxy composite improves energy absorption by 18%. Moreover, the SEM images indicated that the samples containing 7% nanoclay had deteriorated mechanical properties due to nanoparticle agglomeration. In the end, experimental and numerical LVI tests were performed on the samples containing zero and 3% nanoclay to evaluate the agreement between QSI and LVI test results. The increase in the maximum force and elastic energy and the decrease in the damping ratio and residual deflection all indicate the positive effect of clay nanoparticles on impact-resistance. Numerical results were also very well matched with experimental ones. [ABSTRACT FROM AUTHOR]

Nowadays, the hybridization of natural and glass fiber has promised several advantages as a green composite. Nevertheless, their different characteristics lead to poor mechanical bonding. In this work, agel fiber and glass fiber was used as reinforcements, and activated carbon filler was added to the polymer matrix of a hybrid composite to modify its characteristics and mechanical properties. A tensile and bending test was conducted to evaluate the effect of three different weight percentages of activated carbon filler (1, 2, and 4 wt%). Vacuum-assisted resin infusion was used to manufacture the hybrid composite to obtain the high-quality composite. The results have revealed that adding 1 wt% filler yielded the most optimum result with the highest tensile strength, flexural strength, and elastic modulus, respectively: 112.90 MPa, 85.26 MPa, and 1.80 GPa. A higher weight percentage of activated carbon filler on the composite reduced its mechanical properties. The lowest test value was shown by the composite with 4 wt%. The micrograph observations have proven that the 4 wt% composite formed agglomeration filler that can induce stress concentration and reduce its mechanical performance. Adding 1 wt% filler offered the best dispersion in the matrix, which can enhance better load transfer capability. [ABSTRACT FROM AUTHOR]

Bond Behaviour between GRP Reinforcing Bars and High Performance Aerogel Concrete The bond behavior between reinforcing bars and concrete has a significant influence on the overall load‐bearing behavior as well as the serviceability of reinforced concrete components. Extensive investigations have been carried out in the past for glass fiber reinforced plastics (GRP) in connection with normal concrete (NC). It has been shown that the bond behavior of GRP reinforcement is significantly determined both by the surrounding concrete and by the product‐specific properties (geometry, materials) of the reinforcement bars. For the production of reinforced components made of high‐performance aerogel concrete (HPAC), for which GRP reinforcement elements should preferably be used due to their low thermal conductivity, no studies have been carried out yet. Since it is not possible to simply extrapolate the bond behavior of GRP reinforcement with normal concrete to other types of concrete, 48 pull‐out tests were carried out in the investigations presented below to determine the bond behavior. For comparison with the results from the current state of research, the bond behavior of GRP reinforcement in NC was also determined by means of 24 additional pull‐out tests. Based on the results, analytical bond stress‐slip models were derived for both HPAC and NC. Subsequently, these bond stress‐slip relationships were integrated into a FE model and compared with the results of the experimental investigations. [ABSTRACT FROM AUTHOR]

Pultrusion is a high‐volume manufacturing process for fiber‐reinforced polymer (FRP) composites ensuring high strength and quality products. However, research studies are very limited on the fatigue behavior of these products, especially with unidirectional fiber alignment. This study investigates the fatigue behavior of the unidirectional pultruded glass FRP (GFRP) composites with high fiber volume fraction (Vf=65%). Tension–tension fatigue loading was applied with different levels of applied stress, frequency, and gripping condition until failure. Results showed that the high Vf composites have significantly low fatigue life cycle. Moreover, increasing the frequency showed better fatigue resistance, while the tabs geometry has insignificant effect on the fatigue behavior of the dog‐bone shaped specimens. Comparison with available literature showed that GFRP composites with high Vf have lower fatigue performance than those with low Vf. A fatigue capacity reduction factor is also proposed for unidirectional GFRP composites as a function of the Vf. Highlights: High Vf UD GFRP composites were manufactured and tested under fatigue loading.Influence of applied stress, frequency, and gripping on the fatigue life of composites were studied.Fatigue life of UD GFRP composites with various Vf was compared and analyzed.This study proposes a fatigue reduction factor based on the value of Vf for design purposes. [ABSTRACT FROM AUTHOR]

Gridshell structures have the potential to develop the construction process of free-form structures, offering numerous benefits. These include the minimum use of materials, light-weighting, the creation of a large span structure, structural efficiency, organic shapes, potential for quick and cost-effective construction, column-free spaces, maximum transparency, sustainability, and ease of deconstruction and recycling. Gridshells, regarding their architectural potential and intrinsic geometric rationality, are well-suited for creating complex shapes. Hence, the properties of gridshells depend on the equivalent pre-stress of the two-dimensional grid that was deformed. The mechanical properties of glass fiber reinforced polymer (GFRP), such as high elastic limit strain, strength, and Young's modulus, can further enhance the potential of gridshell structures. Gridshell structures offer numerous opportunities for constructing double curvature shells. However, they also present challenges, particularly in the design and construction process, while minimizing stress and preventing breakages of elements under the influence of forces. This paper presents a review of GFRP elastic gridshell structures, including design and construction methods. Additionally, a case study of an existing gridshell structure, the Solidays gridshell, is presented. Finally, the opportunities and challenges associated with gridshell structures are discussed. [ABSTRACT FROM AUTHOR]

In many industrial applications elastomers are frequently used due to its low cost. In present study the Ethylene propylene diene elastomer (EPDM) was used. Solution intercalation method adopted to synthesize EPDM/OMMT clay nanocomposites using organically modified montmrillonite clay. At different loading levels of clay (2%, 3% and 5% weight) various characterizations such as tensile strength, flexural strength and d-spacing behaviour were performed. X-ray diffraction technique was used to study the d-spacing behaviour of different nanocomposites at 2%, 3% and 5% weight percentage of clay loading level. Clay dispersion in the rubber matrix was observed by scanning electron microscope. Comparative study between pure EPDM specimen and EPDM clay nanocomposite specimen was carried out. Modulus as well as flexural strength value was higher for EPDM clay specimen as compared to pure EPDM specimen. [ABSTRACT FROM AUTHOR]

Embedded optical fibre sensors (OFSs) offer the potential to monitor the internal strains at various stages during the manufacturing and service life of fibre-reinforced polymer (FRP) composite structures. Various aspects associated with the embedment of OFSs, such as integration, material compatibility, and sensing performance of the embedded sensor needs to be investigated to develop reliable OFSs based internal sensing platform for composite structures. In this study, Polyimide (PI) and Polyether ether ketone (PEEK) coated optical fibres (OF) were embedded into glass fibre-reinforced polymer (GFRP) composites to evaluate four important aspects associated with the embedment of OFs, which include; i). Structural integrity of the OFs against chemical reactions from vinyl ester resin and its additives through immersion testing, ii). Methods of integrating the OFs into layered glass fibres for the vacuum resin infusion manufacturing process, iii). Sensing performance of the embedded OFs during manufacturing and structural testing (tensile and compressive), and iv). Internal structural integrity of the embedded OFs and the host composite structure using X-Ray micro-computerised tomography technique (μ-CT). The results from the immersion testing and manufacturing process monitoring showed that both PEEK and PI coated OFs can resist the chemical and mechanical stresses caused by resin polymerisation during curing process. The subsequent mechanical testing showed a similar sensing performance by the PI and PEEK coated OFs. Under tensile loads, the OFs monitored the tensile strain distribution up to 7,000 με and compressive strain distribution up to −1,200 με under flexural loading without compromising their optical performance. Finally, the μ-CT scanning results had shown a minimal structural deterioration of the embedded OFs and host composite structure. The outcomes from this detailed experimental investigation on the embedment of OFS in GFRP structures provided useful information towards the integration and performance of optical sensors in composite structures. [ABSTRACT FROM AUTHOR]

This paper examines the behavior at high strain rates of a shear-thickening fluid (STF) impregnated glass fiber-reinforced polymer (GFRP) fabric using a split Hopkinson pressure bar (SHPB). This study involved impact testing of 4 GFRP specimens and 20 GFRP-STF composite specimens at four different strain rates. The STF employed in this study was synthesized by incorporating 20.0 wt.% of 12 nm silica in polyethylene glycol. Rheological tests indicated that the STF exhibited a noticeable shear-thickening effect, with viscosity surging from 3.0 Pa·s to 79.9 Pa·s. The GFRP-STF specimen demonstrated greater energy absorption capacity, deformation ability, and toughness, bearing higher and faster impact loads than neat GFRP. Specifically, the GFRP-STF specimen showed a 21.8% increase in peak stress and a 92.9% rise in energy absorption capacity under high-strain-rate loading. Notably, the stress–strain curve of the GFRP-STF specimen exhibited a distinct yield stage, while the energy absorption curve displayed no significant descending stage features. [ABSTRACT FROM AUTHOR]

This paper studies the compressive failure behavior of pw-GFRP (plain-woven glass fiber reinforced polymer) sandwich composite L-joints for ships. Six L-joint specimens were subjected to ultimate compressive tests, which show that damage and stiffness degradation started much earlier than any visible signs. A modified fiber kinking criterion is developed for the compressive failure of pw-GFRP layup structure. Moreover, a hybrid stiffness degradation model is applied to simulate the damage progression. The criterion and the degradation model are implemented in simulation through Abaqus user coding. The simulation results are compared with other existing theories, and the proposed criterion is validated by the similar damage initiation time. The combination of the proposed criterion and hybrid degradation model demonstrates a clear advantage over conventional methods in predicting the compressive damage evolution and ultimate failure behavior of the L-joint structure. [ABSTRACT FROM AUTHOR]

The study aims to conduct a direct pull-out test on fifty-four cube specimens considering different variables, including the type of reinforcement (sand-coated glass fiber-reinforced polymer (GFRP) and ribbed steel bars); the type of concrete (normal weight concrete NWC and lightweight foamed concrete LWFC); the diameter of the reinforcing bars (10 mm; 12 mm; and 16 mm) and the bonded length (3∅, 4∅, and 5∅). The hybrid fiber hooked-end steel (0.4% by volume) and polypropylene (0.2% by volume), respectively were used to improve the properties of LWFC by converting the brittle failure to ductile. The results showed that in the case of strengthened foamed concrete (FC), the bond strength with steel bars was greater compared to that with the GFRP bars. The bond strength ratio between the GFRP and steel bars of the FC specimens was found to vary between 37.8–89.3%. Additionally, in all specimens of FC, pull-out failure was witnessed with narrower crack width compared to NWC. Furthermore, mathematical equations have been proposed for predicting the bond strength of FC with steel and GFRP bars and showed good correlation with the experimental results. [ABSTRACT FROM AUTHOR]

This article explores the punching shear behavior of GFRP-RC interior slab–column connections. The parameters tested included the column–aspect ratio (1.0, 2.0, 3.0, 4.0, and 5.0), perimeter-to-depth ratio for square column stubs with side lengths of 0.3, 0.4, 0.5, 0.6, and 0.7 m, and span-to-depth ratios of 4, 6, 8, 10, and 12. A review of the literature revealed that no previous study has investigated the effect of these parameters or their interactions on this type of connection. Numerically, twenty-five slabs were created using finite element (FE) software (V3), each with square dimensions of 2.5 m and a constant thickness of 0.2 m. The central column extended 0.3 m from the top and bottom of the slab. All four sides of the slabs were supported, and the specimens underwent pure static shear load testing. The test results demonstrated that all slabs failed due to punching shear. Increasing any parameter value reduced the punching shear stresses. Additionally, the results indicated that Canadian (CSA-S806-12) and Japanese (JSCE-97) standards for FRP-RC materials generally provided the closest predictions of punching shear capacity compared to the American guideline, ACI 440.1R-22. However, all standards exhibited shortcomings and require enhancement and modifications, particularly to consider the impact of the span-to-depth ratio. Therefore, three equations were developed to predict the shear strength of the connections, yielding better results than those prescribed by the North American and Japanese standards.