CFRP repaired welded thin-walled cross-beam connections subject to in-plane fatigue loading
- Authors: Xiao, Zhigang , Zhao, Xiao
- Date: 2012
- Type: Text , Journal article
- Relation: International Journal of Structural Stability and Dynamics Vol. 12, no. 1 (2012 2012), p. 195-211
- Full Text: false
- Reviewed:
- Description: Cracked cross-beam connections made of thin-walled rectangular hollow sections (RHS) are repaired with carbon fiber-reinforced polymer (CFRP) sheets. Constant amplitude fatigue experiments are conducted on the repaired specimens. A pilot test is conducted on a T-connection of square hollow sections (SHS) to explore the effective method of applying CFRP. Due to the peeling effect at the corner region of the SHS-to-SHS connection, early debonding happens in the pilot test that only results in a slight extension in fatigue life. In the following experiments of repairing RHS-to-RHS cross-beam connections, circumferential or transverse restraining CFRP patches are applied in the corner region that prevents early debonding successfully and leads to significant increase in fatigue life. Finally, an improvement is made with the addition of steel strengthening plates that increase both the flexural stiffness and fatigue life of the cracked specimens significantly. The proposed retrofitting method may be useful for repairing other similar fatigue-cracked welded tubular connections.
Crack propagation prediction of CFRP retrofitted steel plates with different degrees of damage using BEM
- Authors: Yu, Qian Qian , Zhao, Xiao , Chen, Tao , Gu, Xianglin , Xiao, Zhigang
- Date: 2014
- Type: Text , Journal article
- Relation: Thin-Walled Structures Vol. 82, no. (2014), p. 145-158
- Full Text: false
- Reviewed:
- Description: Although carbon fibre reinforced polymer (CFRP) materials have proven effective in strengthening steel structures especially when used to improve fatigue behaviour, further study is required to investigate their effectiveness when applied at different stages of crack propagation in steel elements. This paper presents a numerical study on CFRP retrofitted steel plates with different degrees of damage using the boundary element method (BEM). The numerical results compared well with the experimental data, which demonstrated that the BEM is reliable for crack propagation analysis of CFRP laminate retrofitted steel plates. Finally, a parametric analysis was conducted to investigate the influence of bond length, bond width, CFRP stiffness and adhesive shear modulus on stress intensity factor (SIF) values. © 2014 Elsevier Ltd.
Fatigue behaviour of CFRP strengthened steel plates with different degrees of damage
- Authors: Yu, Qian Qian , Chen, Tao , Gu, Xianglin , Zhao, Xiao , Xiao, Zhigang
- Date: 2013
- Type: Text , Journal article
- Relation: Thin-Walled Structures Vol. 69, no. (2013), p. 10-17
- Full Text: false
- Reviewed:
- Description: An experimental and analytical study was conducted to further investigate the effectiveness of the carbon fibre reinforced polymer (CFRP) plates in extending fatigue life of steel structures. Different lengths of artificial cracks were introduced to represent different degrees of fatigue damage. The experimental results demonstrated that the CFRP patches could effectively slow down the crack growth and prolong the fatigue life. A theoretical model was developed to predict the fatigue life of tested specimens. Thereafter, a parametric study was carried out to investigate the fatigue behaviour of steel plates with a wider range of damage degrees. This study extends the understanding of CFRP repair at different stages of crack propagation and provides some useful suggestions for the strengthening method.
Fatigue strength evaluation of transverse fillet welded joints subjected to bending loads
- Authors: Xiao, Zhigang , Chen, Tao , Zhao, Xiao
- Date: 2012
- Type: Text , Journal article
- Relation: International Journal of Fatigue Vol. 38, no. (2012), p. 57-64
- Full Text: false
- Reviewed:
- Description: Three methods of fatigue strength evaluation, i.e., the hot spot stress (HSS) method, 1 mm stress method and linear elastic fracture mechanics (LEFM) method, are used to evaluate the fatigue strength of transverse fillet welded joints in bending and the results are compared with those of fatigue experiments. It is found that the HSS is overly conservative in predicting the fatigue strength of fillet welded joints in bending. The 1 mm stress catches the geometric influence of attachments very well. A reference strength range is suggested for applying the 1 mm stress method to the fatigue strength evaluation of fillet welded joints in bending on the base of analysing available test data. LEFM is an established method for fatigue strength evaluation of welded joints and its applicability is much dependent on the ease and accuracy of quantifying the stress intensity factor (SIF) along the crack front. In this study, the SIF of fillet welded joints in bending is estimated in different ways and the resulting fatigue strengths are compared with fatigue test data.