Experimental study of predamaged columns strengthened by HPFL and BSP under combined load cases

Abstract

After the ground motion, a large number of columns remain intact and can be retrofitted and reused. In this paper, to explore the effects of the loading scenario, predamage level and strengthening measures on the seismic performance of reinforced concrete (RC) columns, seven predamaged specimens strengthened with high-performance ferrocement laminate (HPFL) and bond steel plate (BSP) were tested. The results show that the bearing capacity, ductility, single-cycle energy dissipation and stiffness of all the predamaged specimens can be effectively restored and improved by this strengthening method for different loading cases. This strengthening method also significantly improves the shear capacity and changes the failure modes of the predamaged strengthened specimens from those of the corresponding predamaged unstrengthened specimens. The vertical eccentricity only slightly affects the seismic behavior of the specimens, while the horizontal eccentricity significantly increases the length of the failure region and reduces the seismic behavior of the specimens, considering the bearing capacity, energy dissipation capacity, and stiffness. The effects of different predamage levels are unique.

Keywords:

• Bond steel plates
• combined loading
• cyclic loading
• high-performance ferrocement laminate
• predamaged column
• reinforced concrete
• strengthening

Notations

$P$	=	mean maximum load
${\Delta }_y$	=	yield displacement
${\Delta }_u$	=	ultimate displacement
${\mu }_{\Delta }$	=	displacement ductility coefficient
$E$	=	energy dissipation coefficient
$h_e$	=	equivalent damping ratio
${\Delta }_m$	=	maximum deformation that can be attained within a selected loading cycle
${\Delta }_{um}$	=	ultimate deformation capacity of the specimen subjected to monotonic loading
$\beta$	=	a nonnegative calibration parameter related to cycle damage
$dE$	=	incremental dissipated energy
$V_y$	=	yield load
$D_l$	=	displacement damage index
$m_{eq}$	=	equivalent cumulative cycle number
${\rho }_{sv}$	=	stirrup ratio
$\lambda$	=	shear span ratio
$K_{pj}$	=	average stiffness at the jth stage loading
$V_{ji}$	=	peak loading corresponding to the ith cycle at jth stage loading
${\Delta }_{ji}$	=	displacement corresponding to $V_{ji},$ where n is the number of cycles

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

All data, models, and code generated or used during the study appear in the submitted article.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China (Grant No. 51778060), the Natural Science Foundation of Jiangsu Province (No. BK20191441), the Czech Scientific Foundation project (No. GA17-26353J) and the Fundamental Research Funds for the Central Universities, CHD (Grant No. 300102289401, 300102280711 and 300102280713).