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Effect of Tie Bars on Axial Compressive Behavior of Round-Ended Rectangular CFST Stub Columns
Zhigang Ren1, Qi Li1, Chuang Liu1,2
1School of Civil Engineering and Architecture, Wuhan University of Technology, Wuhan 430070, China.
Materials (Basel, Switzerland)
|February 15, 2022
Summary
Tie bars effectively reduce local buckling in round-ended rectangular concrete-filled steel tube (RRCFST) columns, enhancing ductility and bearing capacity, especially for large aspect ratios. Their effectiveness is limited in small aspect ratio columns due to inherent steel tube confinement.
Area of Science:
- Structural Engineering
- Materials Science
- Civil Engineering
Background:
- Round-ended rectangular concrete-filled steel tube (RRCFST) columns are susceptible to local buckling, compromising their long-term performance as bridge piers.
- This buckling issue affects the structural integrity and service life of bridge infrastructure.
Purpose of the Study:
- To investigate the effectiveness of tie bars in mitigating local buckling and enhancing the performance of RRCFST stub columns.
- To analyze the influence of various tie bar parameters (aspect ratio, spacing, limb number, diameter) on failure modes, confinement, capacity, and ductility.
Main Methods:
- Experimental testing of 11 RRCFST specimens with tie bars and 3 without.
- Development and validation of finite element models (FEM) using different concrete constitutive models for rectangular and circular sections.
- Proposal and validation of an analytical model to predict ultimate bearing load.
Main Results:
- Tie bars reduced the scope of local buckling, shifting it towards the middle height with decreased longitudinal spacing.
- Increased tie bar diameter significantly improved displacement (58.4%) and energy ductility (85.1%) in large aspect ratio columns.
- Tie bars offered limited benefits for small aspect ratio columns due to sufficient inherent confinement from steel tubes.
Conclusions:
- Tie bars are an effective strengthening method for RRCFST columns with large aspect ratios, improving ductility and load-bearing capacity.
- The configuration of tie bars, particularly diameter and spacing, is crucial for optimal performance.
- An validated analytical model can predict the load-bearing capacity of RRCFST stub columns with tie bars.
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