WANG Q, LIANG X H, LIU X,et al.Seismic performance of RC square columns strengthened by UHPC with node reinforcement[J].Journal of Henan Polytechnic University(Natural Science) ,2024,43(6):164-172.

doi:10.16186/j.cnki.1673-9787.2023070033

Received:2023/07/20

Revised:2023/10/07

Published:2024-09-24

Seismic performance of RC square columns strengthened by UHPC with node reinforcement

WANG Qiang1,2, LIANG Xuhua2, LIU Xin2, ZHU Wanxu1,2, LU Chunling1,2

1.Guangxi Key Laboratory of Green Building Materials and Construction Industrialization，Guilin University of Technology，Guilin  541004，Guangxi，China；2.Guangxi Key Laboratory of Geomechanics and Geotechnical Engineering，Guilin University of Technology，Guilin  541004，Guangxi，China

Abstract:  Objectives  To address the problem of debonding between ultra-high performance concrete （UHPC） and reinforced concrete （RC） square columns in strengthened structures， Methods   a method of strengthening the RC square columns with UHPC under node reinforcement was proposed. To verify the effectiveness of this reinforcement method， four specimens were designed and fabricated. The seismic performance indicators， such as ductility， cumulative energy dissipation， and peak load-carrying capacity were analyzed based on whether the columns were reinforced and different axial compression ratios （0.2，0.4）.  Results The test results showed that the ductility coefficient and cumulative energy dissipation of UHPC node reinforcment columns increased by up to 15.7% and 76.4%， respectively， and the peak load-carrying capacity increased by up to 34.5%. The pinching effect of the hysteresis curve of the reinforced columns was improved. This improvement was due to the node reinforcement increasing the bonding stress between the UHPC reinforcement layer and the foundation base， enabling excellent synergy between the UHPC reinforcement layer and the core concrete. Additionally， the UHPC reinforcement layer could restrict the cracking of concrete and the buckling of longitudinal reinforcement in the plastic hinge zone， thereby improving the rotational capacity of the plastic hinge zone. With the increase of axial compression ratio， the load-carrying capacity of the specimens showed an upward trend，but both ductility and cumulative energy dissipation decreased. This was because the steel fibers in UHPC acted as bridges， inhibiting the development of cracks in the cement matrix and reducing the severity of delamination in the UHPC reinforcement layer， resulting in more apparent improvement in the failure mode of high axial compression ratio specimens. Finally， a calculation method for the flexural bearing capacity of UHPC reinforced columns based on the assumption of plane section is proposed. The ratio of the calculated results to the test results was greater than 0.85， indicating high accuracy and validating the rationality of this calculation method.  Conclusions   The research findings can provide an experimental basis and theoretical reference for the practical engineering application and design of UHPC reinforced RC columns under node reinforcement.

Key words:node  reinforcement;UHPC strengthening;RC square columns;seismic performance;flexural bearing capacity