Behavior Of Beams Research Articles

Validating synergistic effects of hybrid nanomaterials and progressive collapse behaviour of UHPC beams: Do particle packing theory, experiments and finite element analysis strongly interconnected?

Ultra-High-Performance Concrete (UHPC), a unique cementitious composite that exhibits an ideal solution for structural reclamation. The significant objective is to develop UHPC with binary nanomaterials (nanosilica and nano clay) using Modified Andreasen and Andersen particle packing theory and examine effect of nano hybridization in flexural and shear behaviour of reinforced UHPC beams. In addition, findings such as load-deflection behaviour and crack pattern are validated with Finite Element Analysis (ANSYS). The synergistic effect of hybrid nanomaterials enhances formation of hydration products that accounts for 27%, 30.7%, and 49% improvement in compressive, splitting tensile, and flexural strength in 2% nanosilica and nano clay (D2 mix Id). Moreover, flexural UHPC beam (D2 F) and shear UHPC beam (D2 S) withstand 9.5% and 10% higher ultimate load than control (A0 F and A0 S mix). The Finite Element Analysis predicts ultimate load in very minimum discrepancy percentage that ranges from 1 to 3%.

Investigating the modal behaviors of a deep beam with a transverse open crack

This paper investigates the modal behaviors of a deep beam with a transverse open crack. Unlike cracked shallow beams with aspect ratio (L/h) > 10, cracked deep beams with aspect ratio < 5 simultaneously exhibit near the crack both axial-bending coupling mode caused by mode I crack and shear (or sliding) mode caused by mode II crack, referred to as axial-bending-shear modal coupling. Therefore, for accurate modal behaviors prediction, appropriate compatibility equations accounting for both modes I and II crack should be employed for deriving a frequency equation. Because the derived frequency equation is nonlinear with respect to modal frequency, the modal frequencies are calculated through the Newton–Raphson method. The corresponding mode shapes are determined by substituting the calculated modal frequencies into the spectral solutions for either side of the crack. The validity of the proposed method was demonstrated through comparison to the finite element analysis and experimental results.

Study of the flexural behavior of UHPC-HPC composite beams strengthened with BFRP sheet after chloride secondary erosion

To solve the issue of insufficient durability of reinforced concrete (RC) structures, a new structure of ultra-high performance concrete (UHPC)-high performance concrete (HPC) composite beam was designed, and the flexural performance of the composite beam strengthened with basalt fiber reinforced polymer (BFRP) after pre-damage was investigated. Results indicate that main cracks are formed and developed after the secondary erosion of chloride salt, leading to three forms of failure modes of the beams: BFRP sheet fracture and concrete crushing, BFRP sheet debonding and concrete crushing and BFRP sheet debonding. The test beam failure process can be classified into three stages: linear elasticity, crack development and yield. The maximum cracking and ultimate loads increased by 27.9 % and 35.8 %, respectively. The crack load growth rate of the beam decreased after 7 days (d) of secondary chloride salt erosion. The formula for calculating the peel strength of the UHPC-HPC composite beam was modified. The calculated bending capacity of the beam agrees well with the measured value. This study provides a reference for enhancing the lifespan and calculating the flexural bearing capacity of structures in corrosive environments.

Fatigue performance simulation of reinforced concrete beams externally strengthened with side bonded CFRP sheets

Damaged Reinforced Concrete (RC) beams are commonly strengthened by bonding Carbon Fiber Reinforced Polymer (CFRP) strips to their soffits. However, inaccessible or narrow soffits limit the use of bottom-bonded CFRP strips. The Side Bonded (SB) CFRP technique overcomes this, yet studies on SB-CFRP-reinforced beams' fatigue behavior are limited. This paper presents a Finite Element (FE) model for simulating the fatigue behavior of RC beams externally strengthened with SB-CFRP sheets. The model incorporates cyclic-dependent CFRP-concrete interface degradation. Existing experimental results are utilized to validate its accuracy. Computational analyses are undertaken to explore the effects of CFRP dimensions, load and prestress levels, and end-U-shaped wrapping on fatigue performance. A simple model is proposed to predict fatigue life considering load and prestress levels. The FE model effectively predicts fatigue performance. Parametric studies indicate that narrow CFRP strips are unable to prevent concrete failure under high loads. Fatigue failure modes include rebar ruptures and CFRP delamination. Besides, the end-U-shaped wrapping reduces interface damage, extending fatigue life. The study emphasizes the sensitivity of vibration excitation method to CFRP debonding. The proposed equation efficiently predicts the fatigue life of RC beams with externally bonded CFRP strips on their sides.

Buckling Analysis of FG Timoshenko Beam Based on Physical Neutral Surface Position

The paper investigates the buckling analysis of functionally graded Timoshenko beams with different boundary conditions. The study focuses on the static and dynamic behavior of FG beams and plates. The critical buckling loads are investigated concerning the slenderness ratio, power law index, and boundary conditions. The method involves defining the effective properties of the FG beam using the rule of mixture, assuming the reference surface is the physical neutral surface. Numerical results are presented, showing the variation of the non-dimensional neutral surface position with the power law index for different material property ratios. The study concludes by discussing the influence of the slenderness ratio, power law index, and boundary conditions on the critical buckling load of FG Timoshenko beams.

Numerical Analysis of Combined Effect Hybrid Fibres and Fire Insulation on the Fire Resistance Performance of SCC Beams

The use of self-compacting concrete in structural members has become increasingly prevalent in various construction applications. However, these structures are susceptible to one of the most hazardous disasters, which is the fire. This paper presents a numerical investigation of the fire resistance performance of self-compacting reinforced concrete (SCC) beams, as well as a parametric study to assess the impact of hybrid fibres and fire insulation on enhancing their performance under fire conditions. The study is conducted by developing a 3D finite element (FE) model using ANSYS software, where temperatures are applied according to the ISO834 standard fire. Geometric and material nonlinearities are considered in the evaluation of the behaviour of beams under fire conditions. The developed FE model is validated by comparing the predicted results with those of the experimental tests in literature. The fire resistance performance of SCC beams was compared with that of normal strength concrete (NSC) beams. The parametric study is conducted using three types of fire insulation, namely Tyfo WR-AFP, CAFCO 300, and Carboline Type-5MD. The results showed that SCC beam has lower fire resistance performance than the NSC beam. However, the incorporation of hybrid fibres allows a 17% improvement in the fire resistance of SCC beams. The use of fire insulations has increased the fire resistance time of SCC beams, and more particularly Carboline Type-5MD insulation with an increase of 28%. The combined use of hybrid fibres and fire insulation improved the fire resistance of SCC beams by 43%.

Behavior of ultra-high-performance concrete deep beams reinforced by basalt fibers

Abstract Deep beams are crucial for construction projects due to their load-carrying capacity, shear resistance, and architectural adaptability. Ultra-high strength concrete and ultra-high-performance concrete (UHPC) are used in their production. Basalt fiber is used as an alternative due to its corrosion resistance, tensile strength, and thermal stability. This study investigates the behavior of UHPC deep beams reinforced with basalt fibers. Three sets of 11 specimens were constructed without transverse reinforcement and reinforced with either fibers or steel fibers. The study also analyzes the impact of parameters like shear strength capacity, crack development, and load-deflection behavior on UHPC deep beams. The study discovered that the inclusion of basalt fibers in UHPC deep beam can effectively postpone the onset of diagonal cracks. Incorporating basalt fiber at concentrations of 0.5, 0.75, and 1.0% led to respective increases of 48.17, 70.07, and 86.66% in the diagonal fracture force, as compared to the inclusion of steel fibers which resulted in increases of 18.24, 56.93, and 98.54% in diagonal fracture loads. The ideal ratio for enhancing the maximum shear capacity was found to be 0.75% of basalt. This specific percent resulted in the highest measured force out of the three percentages that were examined. The addition of basalt fibers at concentrations of 0.5, 0.75, and 1.0% resulted in respective improvements of 11.62, 30.08, and 28.69% in the ultimate shear capacities. During that period, steel fibers significantly enhanced the ultimate shear capacity, resulting in an increase of 19.83, 34.49, and 55.24% compared to specimens without fiber reinforcement. Regarding the second parameter of this investigation, a drop in the shear span ratio is linked to an augmentation in shear capacity and a reduction in mid-span deflection to varying extents for both the utilization of basalt and steel fibers.

Modelling of energy harvesting with bendable concrete and surface-mounted PVDF

Polyvinyl alcohol fiber reinforced engineered cementitious composite (ECC) using piezoelectric polymer film has attracted significant interest due to its energy harvesting potential. This work provides a theoretical model for evaluating the energy harvesting of bendable ECC using surface-mounted polyvinylidene fluoride (PVDF). In the mechanical part, concrete damage plasticity model based on the explicit dynamic analysis was utilized to simulate the dynamic flexural behavior of ECC beam under different dynamic loading rates. The mechanism of force transfer through the bond layer between the PVDF film and ECC specimen was simulated by a surface-surface sliding friction model wherein the PVDF film was simplified as shell element to reduce computational cost. Then, the electromechanical behavior of the piezoelectric film was simulated by a piezoelectric finite element model. A simplified model was also given for a quick calculation. The theoretical model was verified with the experimentally measured mechanical and electrical results from the literature. Finally, a parametric analysis of the effects of electromechanical parameters on the efficiency of energy harvesting was performed. The verified theoretical model can provide a useful tool for design and optimization of cementitious composite systems for energy harvesting application.

Effect of Polypropylene Fibre on Self- Compacting High-performance Concrete

This study conducted tests on the design mixture of Polypropylene Fibre Reinforced Self-Compacting High-performance Concrete (PFRSCHPC) and Self-Compacting high-performance concrete (SCHPC) to determine the mechanical properties of the concrete, and the beams behaviour under bending loads. The composition of the mixtures of PFRSCHPC and SCHPC refer to Oesman, et al. (2022), which conducted research on UHPC (ultra-high-performance concrete) using natural sand and crushed stone through a 4.75mm sieve. PFRSCHPC and SCHPC compositions using Portland Slag Cement (PSC); 1% superplasticizer and 30% silica fume of the total binder; 1% Polypropylene fibre (PP); the ratio of� sand to crushed stone 45%: 55%; and the w/b was 0.23. However, SCHPC as the control concrete mixture does not contain PP. The testing results of the PFRSCHPC showed compressive strength, tensile strength, flexural strength, and modulus of elasticity were 42.73 MPa; 4.33 MPa; 8.98 MPa; 45.51 GPa, respectively. When compared to SCHPC, PP has an influence in increasing tensile strength by 2.38 MPa (122.05%), flexural strength by 2.67 MPa (42.77%), and concrete elasticity modulus by 6.67 GPa (17.32%). However, 1% PP decreased compressive strength of PFRSCHPC, lower by 4.93 MPa (10.34%) compared to SCHPC. PFRSCHPC beam reached a peak load of 27.5 kN; initial stiffness of 5.32 kN/mm; ductility of 5.6; and toughness of 1606.08 kNm. PFRSCHPC beam with PP fibre content of 1% are able to increase 17.02% of peak load; 14.75% of ductility, and 113.91% of toughness.

Effects of CFRP sheets on the flexural behavior of high-strength concrete beam

Abstract The aim of this study is to evaluate numerically the effects of carbon fiber-reinforced polymer (CFRP) sheets strengthening on the flexural performance of high-strength concrete (HSC) beam using ABAQUS 3D finite element (FE) modeling software. The developed FE models were verified against the experimental results found in literature. The FE models can accurately estimate the performance of CFRP-strengthened high-strength reinforced concrete (RC) beams. Subsequent parametric analysis was performed to assess the performance of CFRP-strengthened concrete beams considering various parameters including compressive strength of concrete, CFRP width, thickness, length, number of CFRP layers, and CFRP strengthening schemes. Based on the results of FE analysis. It was demonstrated that using HSC significantly enhances the performance of CFRP-strengthened RC beams. It was also confirmed that width, thickness, and layer number of CFRP sheets improve the flexural behavior of CFRP-strengthened HSC beams by increasing the ultimate loads and strain-hardening behavior of the specimens. The strengthening schemes contribute to delaying or inhabiting the debonding especially when the CFRP sheets are added along the bottom of the beams. It was demonstrated that using CFRP sheets U-wrapping contributes to the prevention or delay of debonding and increases the capability of resisting the stress imposed on the concrete. Therefore, installing the CFRP sheets at the bottom face of beam below the tensile reinforcement enhances the performance of CFRP-strengthened HSC beams.

The Behavior of Ferrocement RC Beams Exposed to Flexural Load and Elevated Temperature

The Behavior of Ferrocement RC Beams Exposed to Flexural Load and Elevated Temperature

The effect of concrete compressive strength to the strengthening efficiency of RC beams using CFRP in slits

The near-surface mounted technique (NSM) is one of the most effective techniques to strengthen concrete structures, mainly in bending and shear. ABAQUS software has been used to establish a numerical model for the mechanical behavior of a RC beams strengthened by CFRP NSM. In this paper, three rectangular CFRP strengthened RC beams were simulated using ABAQUS and tested in four-point bending scheme in order to investigate the impact of concrete compressive strength to the strengthening efficiency. The results showed that increasing the Concrete compressive strength induced a positive impact to the peak load. further changing the compressive strength influence the failure criteria of the tested specimens.

Flexural behavior of glulam beams reinforced by bonded prestressing tendons

The rapid progression of mass timber structures towards greater spans presents a challenge for the flexural behavior of glulam beams. In this study, this challenge was addressed by reinforcing the glulam beams with prestressing tendons which were bonded to the glulam beams by epoxy resin. The objective of this study is to investigate the influence of prestressing force levels and bonded types on the flexural behavior of prestressed glulam beams. Four-point bending tests were conducted on twelve glulam beams prepared by unreinforced, unbonded prestressed or bonded prestressed techniques. Experimental results revealed that the glulam beams exhibited increased ductility under prestressing force. Compared with unreinforced beams, the prestressed beams demonstrated a remarkable increase of up to 78.8 % in flexural capacity and 13.5 % in flexural stiffness. For the prestressed beams, the flexural capacity increased as prestressing force increases. Compared with the unbonded prestressed beams at the same prestressing force level, the bonded ones exhibited higher flexural capacity and flexural stiffness. Additionally, the bonded prestressed beams exhibited a slight increase in tendon stress at the end of the prestressing tendon during loading, indicating favorable bonding behavior of epoxy resin. Numerical models were developed to predict the non-linear flexural behavior of prestressed beams, and the numerical results showed good agreements with the experimental results. Parametric analysis based on the numerical models was conducted on the prestressed beams at various prestressing force levels. The positive effect of the bonded prestressed method on the flexual behavior of glulam beams was further substantiated.

Bending performance of laminated veneer lumber timber beams strengthened in the compression side with near-surface mounted CFRP plates

This study investigated the bending behavior of timber beams that were strengthened using carbon fiber-reinforced polymer (CFRP) plates. Fourteen laminated veneer lumber (LVL) timber beams, each measuring 60 mm×200 mm x 2400 mm, were subjected to four-point bending tests. The objective was to investigate the effect of using CFRP plates as near-surface mounted (NSM) strengthening in the compression zone on the bending behavior of the LVL timber beams. In this experiment, two beams were left unstrengthened while the remaining beams were strengthened with varying lengths, depths and numbers of CFRP plates. The beams load-midspan deflection relationship, ultimate load capacity, stiffness, failure mode, and strain profile distribution were analysed based on experimental results. The use of CFRP plates in the compression zone of LVL beams has been found to improve their strength and stiffness. The test result showed timber beams strengthened with CFRP plates with a reinforcement ratio ranging from 1.67 % to 5.00 % experienced a significant increase in bending strength of 4.24–28.85 % and an increase in bending stiffness of 16.48–62.51 %. These results indicate that NSM CFRP plates can effectively strengthen timber materials, offering improved bending performance and durability.

Alterations to the bending mechanical properties of Pinus sylvestris timber according to flatwise and edgewise directions and knot position in the cross-section

Given the heterogeneity of the material, the behaviour of a timber beam may differ depending on which of its sides is subjected to tension and which one is subjected to compression. An analysis is undertaken in the present work of the behaviour in non-destructive bending tests on the four sides of 57 samples of Pinus sylvestris (scots pine) of structural size (2000 × 100 × 70 mm3). A study is additionally performed of the influence of the size and position of knots in the cross-section. The modulus of elasticity in flatwise direction was found to be 3 % higher than in edgewise direction. This difference could be attributable to the shear effect. While the introduction of knottiness variables did not improve modulus of elasticity prediction, it did decrease the error in the prediction of the modulus of rupture. The margin knot area ratio corresponding to the outer eighth of the cross-section’s width occupied by knots was the knottiness variable with the lowest error in modulus of rupture prediction.

Flexural behaviour of precast reinforced concrete beams bonded to steel-reinforced engineered cementitious composites

Prefabricated concrete structures have attracted much attention due to their simple construction and reliable quality control. Due to the load requirements of transportation vehicles, the prefabricated concrete components must be divided into sections and then transported to be assembled in place. Therefore, the connection between prefabricated concrete beams significantly affects the mechanical behaviour of the structures. This paper proposes a new connection for prefabricated concrete beams bonded to reinforced engineered cementitious composites (ECC). Static experiments were carried out on a cast-in-place (CIP) beam and five precast concrete beams with different lengths or reinforcement ratios of steel-reinforced ECC. The cracking propagation, flexural capacity, beam stiffness, and strain distribution of the precast concrete beams were comparatively analysed. It is concluded that the flexural behaviour of the precast beams proposed in this study was similar to that of the CIP reference. Moreover, the flexural capacity of the prefabricated beams increased as the reinforcement ratio of steel-reinforced ECC. As the reinforcement ratio of steel-reinforced ECC increases from 1.67 % to 6.7 %, the corresponding flexural capacity of the prefabricated beams increase from 59.56 kN to 168.78 kN. Finally, a formula was established to predict the flexural capacity of prefabricated beams bonded to steel-reinforced ECC, and the theoretical results show good agreement with experimental results.

Experimental study on the flexural behaviors of ECC-reinforced masonry beams with GFRP mesh

This study aims to investigate the flexural behaviors of ECC-reinforced masonry beams with GFRP mesh under various interface treatment methods. Eleven sets of ECC-reinforced masonry beams with GFRP mesh were fabricated and subjected to a four-point bending test. The effects of the fibre volume fraction and thickness of ECC, interface treatment methods, GFRP mesh strength and layers on the flexural behavior of masonry beams were investigated and analyzed, including the failure mode, crack distribution, flexural strength, and load-deflection curves. The test results revealed that a transition in the failure mode of masonry beams from brittle failure to interfacial stripping failure or ductile failure after reinforcement. Increasing the number of GFRP mesh layers, the fibre volume fraction and thickness of ECC improved the flexural performance of the masonry beams, while increasing the GFRP mesh strength had the opposite effect. Among the variables, the interface treatment method exerted the greatest influence on the flexural performance of the masonry beams. The masonry beams treated with a bolt interface exhibited the best flexural performance, with flexural toughness and ultimate deflection increasing by 1.69 times and 0.32 times, respectively. Furthermore, the flexural performance of the masonry beams reinforced with a 15 mm thick ECC and single-layer GFRP mesh demonstrated similar reinforcement effects to the masonry beams reinforced with a 20 mm thick ECC, while reducing costs by 23 %. Based on the existing codes governing the calculation method of flexural strength and considering the influence of various factors, a calculation model for the flexural strength of ECC-reinforced masonry beams with GFRP mesh was established.

Macro-meso cracking inversion modelling of three-point bending concrete beam with random aggregates using cohesive zone model

An accurate description of concrete crack propagation is essential to practical engineering. In this paper, the cohesive zone model (CZM) is used to investigate the macroscopic mechanical properties and the microscopic crack damage behavior of concrete beams in the three-point bending test. Five key factors controlling the cracking of cohesive elements, namely mode I fracture energy, mode II fracture energy, shear strength, tensile strength, and elastic modulus (stiffness), are subjected to parametric examinations. Based on macro-mechanical properties and micro-cracking, the test results and parametric models of specimens are inversely analyzed. The applicable parameter range of control factors in the three-point bending simulation is obtained. Considering the quantitative aggregate information of specimens with different mix proportions, three computation models with different aggregate areas are established. The quantitative results of crack propagation are derived by applying the parameter range. Finally, the accuracy of the parameter range is validated based on the simulated and experimental mechanical properties and quantitative results of cracks.

Effect of GFRP bar length on the flexural behavior of hybrid concrete beams strengthened with NSM bars

Abstract This project aims to investigate the effect of near-surface-mounted glass fiber reinforced polymer (GFRP) bars strengthening on the flexural behavior of hybrid reinforced concrete beams. Seven beams were made; one of these specimens had no strengthening and is considered as a reference beam. The other models were strengthened using near-surface-mounted GFRP bars at the bottom of beams with different lengths (0.5, 0.75, and 1) of effective span beams and diameters (8 and 12 mm) of GFRP bars. The beam length was 2,200 mm with 150 mm width and 240 mm depth. The flexural reinforcement consists of 2 φ12 steel bars at the tension zone and 2 φ12 at the compression zone for all beams. Furthermore, to resist shear forces, φ12 steel bars were used, distributed along the length of the beams spaced at 125 mm c/c; two-point loads on the beams with 500 mm between them were applied at the mid-span. The investigated characteristics were cracking and failure load, crack width, deflection, and failure patterns. By examining the models, it was found that there is an improvement in failure load range from 11.54 to 53.84% relative to the control.

Experimental and analytical investigations into flexural behavior of composite beams with UHPC T-section and HRS H-section

This study investigated the flexural behavior of composite beams with ultra-high performance concrete (UHPC) T-section and hot rolled steel (HRS) H-section. First, a four-point bending test on six specimens was conducted. The effects of stud spacing and tensile reinforcement ratio on flexural performance were investigated in terms of crack patterns, failure modes, ultimate load, load-strain response, relative interfacial slip, and ductility. The experimental results indicated that the stud spacing and the presence of tensile reinforcement had a visible effect on the crack patterns of UHPC web. The distribution of group cracks was observed at UHPC web of specimens with unreinforced UHPC bulb. During the failure stage, the whole HRS H-section in the constant moment region yielded. In particular, the partial cross section of HRS entered the strain hardening stage. In addition, an analytical approach verified by six tested specimens was developed to study the moment-curvature response of HRS-UHPC composite beams (HUCBs). The comparison results indicated the good accuracy of the analytical approach. Then, the proposed sectional analysis model was utilized to investigate the effects of the strength of HRS and UHPC, the total depth of cross section, and the depth of HRS H-section on yielding moment, including ultimate moment and ductility. The analytical results revealed that the strength of HRS and the total depth of cross section had a significant impact on the moment-curvature response of HUCBs. The sectional analysis also illustrated that the yielding point was mainly determined by the yielding of HRS H-beam. Compared with UC120, the ultimate moment and ductility coefficient of the composite beam using UC200 increased by 20.6 % and 87.7 %, respectively. However, the tensile strength of UHPC had a slight influence on the yielding and ultimate moment as well as ductility.