Experimental Investigation of Tensile and Bond Strength for a GFRP–SSWM Hybrid Wraps

This study experimentally investigates the tensile and bond performance of novel GFRP–SSWM hybrid wraps developed using two epoxy adhesives - Sikadur 30 LP and Sikadur 330. A total of 42 coupon specimens for tensile testing and 48 dumbbell specimens for bond testing are prepared using various two-layer and three-layer configurations of GFRP, SSWM, and their hybrids. Tensile tests are conducted as per ASTM D3039, and specimen performance are evaluated in terms of ultimate load capacity, displacement at peak load, stiffness, rupture strain, and failure modes. Fractographic assessment is also performed at the failure plane of coupon specimens. Study results of tensile and bond test, indicate that GFRP-only specimens exhibit high tensile strength and stiffness but fail in a brittle manner, while SSWM-only specimens show greater ductility with reduced strength. Hybrid configurations offer a balanced response between strength and ductility. Among hybrids, GS specimens bonded with Sikadur 30 LP show superior performance in two-layer systems. Fractographic observations confirm effective hybrid action between GFRP and SSWM without delamination or layer separation at the interface. The capacity utilization ratio further supports that Sikadur 30 LP performs better than Sikadur 330, especially in hybrid configurations involving SSWM. The study highlights the mechanical viability of GFRP-SSWM hybrid wraps for use in strengthening applications

An experimental study on the rehabilitation performance of CFRP-strengthened bubble deck slabs: effects of void size and preloading levels

This study examines the rehabilitation performance of reinforced concrete bubble deck slabs (with 50 mm and 60 mm voids) strengthened with externally bonded CFRP sheets. Nine specimens were tested: eight bubble slabs (grouped by void size and preloading level) and one solid control slab. Three specimens of each void size were pre-damaged to 50%, 60%, and 75% of their ultimate load before being strengthened with CFRP and retested. One specimen per group remained unstrengthened for comparison. Results show that increasing void size reduces load capacity: the unstrengthened 50 mm and 60 mm void slabs achieved 96.2% and 86.5% of the solid slab’s strength, respectively. CFRP rehabilitation effectively restored structural performance, with 50 mm void slabs recovering up to 98.5% of the control slab’s capacity and exhibiting 25% lower deflection. In contrast, 60 mm void slabs showed lower recovery efficiency, particularly at higher preloading levels SB-6-75 recovered only 82.5% of the control strength. All strengthened specimens failed by CFRP debonding combined with flexural cracking, with no shear failures observed. The study demonstrates that CFRP retrofitting significantly enhances the strength and stiffness of damaged bubble deck slabs, especially those with smaller voids. Void size and pre-damage level are critical factors influencing rehabilitation success

Correlation Between Process Parameters and Mechanical Properties of Ti6Al4V Alloys Processed by Electron Beam Melting

The present study of Ti6Al4V alloy production via Electron Beam Melting (EBM) represents a cutting-edge research topic impacting different strategic engineering applications. This can be attributed to the widespread use of this alloy and by the unique characteristics of the EBM process. Operating under vacuum and with powder pre-heating, EBM enables the fabrication of components with higher density and reduced residual stress compared to other additive manufacturing techniques. The research reported in this paper analyses the effect of process parameters used in the manufacturing process on defect formation and then on mechanical properties. The results highlighted that the presence of lack of fusion defects leads to a markedly anisotropic behavior of the alloy. This is due to the different morphology of the defects in the different considered directions and to their effect in concentrating stresses

Numerical modeling of fracture processes of bodies with stress concentrators under conditions of proportional loading, taking into consideration the statistical distribution of ultimate strength and partial loss of load bearing capacity

This work is dedicated to the development of a fracture model for an elastic-brittle solid with statistically distributed strength characteristics of subregions and the application of this model to describe fracture processes of bodies with stress concentrators under biaxial loading. The methodology of numerical modeling of deformation and fracture processes is improved to take into account the partial loss of load bearing capacity and the appearance of local anisotropy. Based on the improved methodology, modified algorithm is developed. The influence of the biaxial loading mode and the dispersion of the ultimate strength distribution on the loading diagrams and the orientation of the macrodefect is considered. The realization of the gradual macrodefect development (localized type of damage accumulation) or its growth through the most weakened damaged areas (mixed type) is revealed. The applicability of the approach to assessing the type of damage accumulation based on the analysis of numerical solutions of boundary value problems within the elasticity theory is demonstrated. The efficiency of the usage of the modified approach to ensure the reliability and safety of critical structures under multiaxial loading is concluded

Improved flexural behaviour of reinforced concrete beam strengthened using stainless steel wire mesh

The paper presents an experimental investigation of the flexural behaviour of reinforced concrete (RC) beam elements strengthened externally with stainless steel wire mesh (SSWM). SSWM has the potential to be an alternative composite material in place of Carbon Fiber Reinforced Polymer (CFRP) and Glass Fiber Reinforced Polymer (GFRP) because of advantages such as being cost-effective, having more fire-resistance and corrosion resistance, good bond behaviour with concrete, improve the strength of members, leaving minimal effects on structural aesthetics as it has less thickness and ease in availability. In the present study, SSWM has been wrapped externally over the beams having three different wrapping patterns, including fully wrapped vertical SSWM strips over the beam, partial wrapping of vertical SSWM strips in between the stirrups of the beam and partial wrapping of vertical SSWM strips above the stirrups of the beam, and control beam with no wrapping, each configuration having two test specimens. Results of experimental investigation in terms of cracking load, ultimate load, corresponding deflection, ductility, initial stiffness and energy absorption capacity of different wrapping patterns have been obtained and compared with those of control beam specimens. From the results obtained, it has been demonstrated that the fully wrapped SSWM strip wrapping pattern enhanced the flexural strength of the beam and showed the highest strength gain compared to the other wrapping patterns

Structural behavior of GFRP-concrete composite beams

Glass Fiber Reinforced Polymer (GFRP) I-sections offer a promising alternative to traditional steel reinforcement due to their reduced weight and maintenance requirements. This study aims to optimize the design of GFRP-reinforced composite concrete beams for cost-effective solutions. Twelve tested beams were tested under four-point bending loading, divided into four groups with varying depths: three conventional reinforced concrete (RC) beams as control specimens; nine beams with GFRP I-sections positioned internally; externally; and internally with exposure to 500°C for 90 minutes. The test results indicate that GFRP-reinforced beams exhibit superior strength and bending resistance compared to conventional RC beams where an increase in maximum load ranging from 62% to 113% and reduced deflection at the same load level. Optimal performance was observed when GFRP I-sections were placed near the tensioned fiber. Exposure to elevated temperatures resulted in minimal performance reductions, not exceeding 5% at yield load and 16% at maximum load comparing with composite tested specimens without exposure to elevated temperature. Theoretical analyses closely aligned with experimental results, providing a foundation for practical guidelines on the economical design of GFRP-reinforced composite

Optimizing different damaged reinforced concrete corbel characteristics utilizing CFRP sheets

Concrete corbels are short cantilever constructions that may lose their strength over time because of loads that happen over and over again. As an external bonding method for reinforcement, carbon fiber-reinforced polymer (CFRP) strips are utilized to improve performance. This study examines the influence of CFRP strips on the reinforcement and repair of conventional concrete corbels by concentrating on ultimate strength, performance under monotonic loads, and the effects of varying damage ratios during restoration. As part of a study project, nine double-concrete corbels with the same size and reinforcement had to be manufactured and tested. The samples were split into two groups: those with strip wrapping and those with side wrapping. Each group had three corbels that had already been damaged, one corbel that had been reinforced, and control specimens that had not been repaired. The results showed that side-wrapped corbels with CFRP reinforcement exhibited a 19.72% (SCS-0-1) improvement in strength and a 13.73% (RCS-50-1), 18.35% (RCS-60-1), and 4.15% (RCS-70-1) increase in ultimate load. Strip-wrapped corbels showed improvements of 9.86% (RCST-50-2), 5.44% (RCST-60-2), and 0.51% (RCST-70-2), whereas strengthening (SCST-0-2) showed an improvement of 19.72%. Also, specimens wrapped in CFRP showed less ultimate deflection than their un-strengthened counterparts at the same damage levels, which shows that they perform better and last longer

Behavior of steel columns with double curvature: a numerical simulation and design-oriented parametric study

This research present a novel investigation, which focuses on the numerical exploration of steel columns having a double curvature, built with both hollow square and circular cross-sections. A finite element model was initially created using ABAQUS software and was validated through a series of compression experiments conducted on square hollow specimens exhibiting double curvature. close agreement was observed in term of ultimate loads, load–displacement curves and deformed shapes corresponding to the failure modes. Based on validated numerical simulations, parametric analyses are carried out to investigate the effects of major geometric parameters on the axial bearing capacity of double curved steel columns. The study consists in a systematic variation of curvature angle (20°, 25°, 30°, and 35°), curvature radius (500 mm, 700 mm, 900 mm, and 1100 mm), square cross-section size (250 mm, 300 mm, 350 mm, and 400 mm), circular diameter (318 mm, 381 mm, 445 mm, and 509 mm) and end offset distance (400 mm, 600 mm, 800 mm, and 1000 mm). The findings highlighted the sensitivity of axial performance to angle curvature, section width and offset distance at column ends. The outcomes of this study provide valuable insights for the design and optimization of curved steel columns in structural engineering applications, particularly where stability and axial strength are critical

Effect of fracture energy estimation on the predictions of mode II behavior of bonded joints using cohesive zone models

Fracture behavior of adhesive joints is an important topic in structural design of new structural elements or in retrofitting of existing ones. The mechanical models available in literature capable of predicting the failure mode of these junctions are mainly formulated within the cohesive zone model (CZM). Direct approaches for identification of CZM parameters in pure mode II of bonded joints, based on different modelling of strain energy release rate (SERR), are presented. The mode II SERR was determined from experimental results on end notched flexure (ENF) tests. Digital image correlation (DIC) analysis was used to evaluate the shear slip displacements of adhesive layer. The mode II cohesive traction-separation law was identified by numerical differentiation of SERR and best fit equation systems were adopted for an analytical description of cohesive interface behavior. Moreover, the obtained CZM laws were used for predicting the decohesion process by finite element analyses. Global and local responses of ENF test were compared with experimental data in terms of load-displacement and adhesive tangential displacement-time curves, respectively. A more accurate modelling of fracture energy resulted in a sounder agreement of prediction with experimental data

An innovative analytical approach for predicting the fundamental time period of moment-resisting frames

Most seismic design codes provide formulas for estimating base shear and lateral loads. To determine lateral loads, the building's fundamental vibration period must be calculated, either theoretically or experimentally. However, there is no simplified equation that accurately calculates this parameter. This paper proposes a new simplified formula for computing the fundamental period of reinforced concrete moment-resisting frames (MRFs). The proposed formula is validated through eigenvalue analysis of the mathematical models of various building frames using finite element methods (FEM), with varying structural properties along their height. The proposed model achieved an average prediction error of around 4% and an R² (coefficient of determination) value of 0.999 when compared to FEM results, outperforming existing empirical formulas. A sensitivity analysis was conducted to identify the effect of each of the design parameters, accompanied by a comparative evaluation against some formulas from the literature. The novelty of the suggested method is that it can calculate the fundamental period more accurately and easily by considering the stiffness and seismic mass of the building