Wind-resistant performances comparison between a long-span CFRP and a steel cable-stayed

Influence of temperature on concrete beams strengthened in flexure with CFRP

In steel members strengthened by carbon-fiber reinforced polymer (CFRP) plates, the thermal stresses are introduced in the steel members, the CFRP plates and the adhesive layers when temperature changes because the linear thermal expansion coefficients of steel and CFRP are mismatched. As so far, the authors proposed a technique to reduce the thermal stress in steel members strengthened by CFRP plates, which involves bonding aluminum alloy plates with CFRP plates. In the proposed method, the thermal stress in steel member can be reduced so that there are negligible levels of stress in steel member when the cross sectional areas of CFRP and aluminum plates are designed to correspond to the coefficient of thermal expansion of steel, even though the thermal stresses are introduced in the CFRP and aluminum plates. In this study, to confirm the maintaining the thermal stress reduction in steel member by proposed method, thermal stress measurement in steel plate strengthened by CFRP and aluminum plates was carried out about 21 months. In this research, the thermal stress introduced in the steel plate strengthened by CFRP plates was also measured. Furthermore, to assume the thermal shear and normal (peel) stresses in adhesive layers, FE analysis with plane stress element was employed. As the result, it was shown the thermal stresses in steel plate with CFRP plate were able to calculate by using composite theory and measured temperature. Furthermore, in steel plate strengthened by CFRP and aluminum plates, the thermal stress introduced in steel plate was negligible-small through the all-season. It was found the thermal stresses in steel plate with CFRP plates as well as CFRP and aluminum plates were also estimated by using composite theory and measured temperature. In the steel plate strengthened by CFRP and aluminum plates, the thermal shear and normal stresses in adhesive layer glued to steel plate become smaller than that in the conventional CFRP bonded specimen. However, the shear stress in adhesive layers between CFRP and aluminum plates in proposed method was higher than the thermal stress in adhesive layers between CFRP plates in conventional method.

CFRP lamella stay-cable and its force measurement based on microwave radar

The guided wave technique is commonly used in structural health monitoring as the guided waves can propagate far in the structures without much energy loss. The guided waves are conventionally generated by the surface-mounted piezoelectric wafer active sensor (PWAS). However, there is still lack of understanding of the wave propagation in layered structures, especially in structures made of anisotropic materials such as carbon fiber reinforced polymer (CFRP) composites. In this paper, the Rayleigh-Lamb wave strain tuning curves in a PWAS-mounted unidirectional CFRP plate are analytically derived using the normal mode expansion (NME) method. The excitation frequency spectrum is then multiplied by the tuning curves to calculate the frequency response spectrum. The corresponding time domain responses are obtained through the inverse Fourier transform. The theoretical calculations are validated through finite element analysis and an experimental study. The PWAS responses under the free, debonded and bonded CFRP conditions are investigated and compared. The results demonstrate that the amplitude and travelling time of wave packet can be used to evaluate the CFRP bonding conditions. The method can work on a baseline-free manner.

Numerical investigation of the parameters influencing the behavior of dapped end prefabricated concrete purlins with and without CFRP strengthening

The improvement in the flexural response and cracking resistance of steel-concrete composite beams stiffened with Carbon Fiber Reinforced Polymers (CFRP) sheets at the hogging moment regions is investigated experimentally and numerically in this study. The experimental program consists of two composite beams tested in an inverted position to simulate a portion of a continuous composite beam at the hogging moment region. The concrete flanges of the beams are reinforced externally with corrugated steel deck which used also as a permanent formwork. The experimental findings are used to develop and validate a reliable finite element (FE) model which able to simulate the non-linear performance of the stiffened beams as well as plain beams. In addition, a FE analysis on full-scale continuous composite beams with reinforced concrete flange is carried out to confirm the influence of using CFRP strips as a strengthening technique at the hogging moment regions. The beam deformation, steel flange strain, concrete strain, and CFRP strain confirm good agreement between the FE analysis and the test data. The beam capacity is enhanced only by 11% due to a premature failure in the composite flange. Although the composite connection between the concrete flange and the steel beam is improved by enhancing the cracking resistance of the concrete, the ductility of the strengthened beams is reduced by 20% in comparison to the un-strengthened beam.

Carbon fiber-reinforced polymer (CFRP) sheets have recently become popular for use as repair or rehabilitation material for deteriorated carbon fiber reinforced concrete structures. Carbon fiber reinforced concrete beams were analyzed by finite element software ANASYS. Through the finite element analysis, the results showed that using bonded CFRP to strengthen R. C. beams can significantly increase their load carrying capacity. However, the beams with prestressed CFRP can withstand larger ultimate loads than beams with bonded CFRP. Using bonded CFRP to strengthen R. C. beams can obviously reduce the ultimate deflection.

Purpose This study aims to present the load-carrying capacity and its most influential parameters for concrete-filled steel built-up columns (CFSBC) under axial compression. A novel analytical model has been proposed and validated to estimate the ultimate inelastic buckling strength of the CFSBC. The research also explores the effects of column length, plate thickness and carbon fibre-reinforced polymer (CFRP) confinement through finite element analysis (FEA). Design/methodology/approach The model has been proposed based on the column’s inelastic buckling. The proposed model has also been verified with the experimental database of 96 CFSBC. The parametric study is carried out using the finite element (FE)-based ABAQUS software for various parameters, such as the length of CFSBC, the plate thickness and the number of confining CFRP layers. Findings It is observed that while increasing the length of the column, the load-carrying capacity is reduced to about 12% for per metre of length increment and the reduction in the width-to-thickness ratio (b/t) reduces the load-carrying capacity to the extent of 10% to 15% for each 2 mm of thickness reduction. Owing to the change of CFRP layers from 0 to 3, there is no significant change in the results, which concludes that CFRP has a less effective role in the case of CFSBC. Research limitations/implications This study primarily focuses on the axial compression behaviour of CFSBC without considering lateral or seismic loading effects. The analytical model is validated against 96 experimental results, but further verification with larger data sets is needed for broader applicability. The FEA is conducted using ABAQUS, which may have limitations in capturing many complex real-world conditions. Additionally, CFRP confinement is analysed for up to three layers only, and its effectiveness beyond this limit remains uncertain. Practical implications This study provides a robust framework for designing CFSBC with optimised load-carrying capacity. Engineers can use the validated analytical model to estimate inelastic buckling strength, reducing reliance on costly experimental testing. The findings emphasise controlling column length and plate thickness to maximise strength, ensuring safer and more efficient structural designs. As CFRP confinement has minimal impact, its usage can be minimised, leading to cost savings. These insights are crucial for high-rise buildings and bridge applications, promoting sustainable construction by improving material efficiency, reducing waste and enhancing the overall performance of composite structural elements. Social implications The study contributes to safer and more efficient infrastructure by improving the design of CFSBC, leading to durable and cost-effective construction. Enhanced structural performance reduces the risk of failures, ensuring public safety in high-rise buildings and bridges. The optimised use of materials, especially reduced reliance on CFRP, lowers construction costs, making housing and infrastructure development more affordable. Additionally, promoting sustainable construction through efficient material use aligns with environmental conservation efforts. The findings support infrastructure resilience, benefiting communities by ensuring long-term structural reliability, reducing maintenance needs and fostering economic growth through optimised engineering solutions. Originality/value This study proposes a novel analytical model for predicting the inelastic buckling strength of CFSBC, validated with experiments and simulations, offering insights into key design factors while optimising material use and structural efficiency.

LES study on variation of flow pattern around a 4:1 rectangular cylinder and corresponding wind load during VIV

This paper offers the findings of numerical study carried out to evaluate the behavior of low strength concrete columns in square section strengthen by Carbon Fiber Reinforced Polymer (CFRP) composites and subjected to axial compression load. In this study, a three dimensional non-linear finite element formulation model has been presented using ANSYS-16.1 (software computer program) to analyse low strength concrete columns in square section strengthen by CFRP composites in different configurations, to evaluate the improvement in the ultimate load capacities of columns as a result of CFRP confinement, and to study the impact of the most important parameters such as: compressive strength of concrete, thickness of the CFRP layers jacket/strips and the presence of steel reinforcement on the performance of th modelled columns subjected to compression load. A comparison has been made between the results obtained from the Finite Element Analysis (FEA) and experimental data. The results of the numerical FEA study showed that, external strengthening with CFRP composites are very effective in upgrading the ultimate load of square concrete columns. In addition, the findings revealed good agreement between the ANSYS and the experimental test results. The results obtained from the parametric study revealed that when the CFRP layers increased from 2 to 3 layers and from 2 to 4 layers the ultimate loads of the columns increased about (2%-10%) and (7%-15%) respectively. While the compressive strength showed significant effect on the upgrade of the ultimate load, when increase the compressive strength to 42MPa and to 60 MPa, the ultimate load increased to about 220% and to about 300% respectively. The presence of steel reinforcing did not show reasonable effect on the ultimate load.

Analytical study of CFRP strengthening steel plates with a semi-elliptical surface crack

Fatigue behavior and digital image correlation monitoring of steel plates with mixed-mode edge cracks repaired with CFRP materials

A reliability analysis of the axial compressive load bearing capacity of postfire reinforced concrete (RC) columns strengthened with carbon fiber reinforced polymer (CFRP) sheets was presented. A 3D finite element (FE) model was built for heat transfer analysis using software ABAQUS. Based on the temperature distribution obtained from the FE analysis, the residual axial compressive load bearing capacity of RC columns was worked out using the section method. Formulas for calculating the residual axial compressive load bearing capacity of the columns after fire exposure and the axial compressive load bearing capacity of postfire columns retrofitted with CFRP sheets were developed. Then the Monte Carlo method was used to analyze the reliability of the axial compressive load bearing capacity of the RC columns retrofitted with CFRP sheets using a code developed in MATLAB. The effects of fire exposure time, load ratio, number of CFRP layers, concrete cover thickness, and longitudinal reinforcement ratio on the reliability of the axial compressive load bearing capacity of the columns after fire were investigated. The results show that within 60 minutes of fire exposure time, the reliability index of the RC columns after retrofitting with two layers of CFRPs can meet the requirements of Chinese code GB 50068 (GB 2001) for safety level II. This method is effective and accurate for the reliability analysis of the axial load bearing capacity of postfire reinforced concrete columns retrofitted with CFRP.

Load-deflection curve is the most important part of the structural analysis of RC beam and slab. The load-deflection analysis of the RC one-way slab strengthened by CFRP using experimental work, finite element analysis (FEA), artificial neural network (ANN), and a comparison of them together are the important objective of this study. The dimension of the one-way slab was 1800A�400A�120 mm which was strengthened by different length and width of carbon fiber reinforced polymer (CFRP). The experimental results sufficiently adapted with FEA and ANNs output. The feed forward back-propagation (FFB) was the best ANN for prediction of load-deflection curve with minimum error below 1, and maximum correlation coefficient close to 1.

Notch stress intensity factor for center cracked plates with crack stop hole strengthened using CFRP: A numerical study