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This research is mainly concerned with studying experimentally the behavior of ultra high performance fiber reinforced concrete short columns loaded eccentrically. The investigation was undertaken on seven columns until failure. The achieved compressive strength of the tested concrete cubes was 130 MPa.
The evaluation of columns’ performance was based on main parameters, which were the ratios of eccentricity to thickness of the columns, longitudinal reinforcement and transversal reinforcement. Failure modes and crack patterns, deformations and strains’ behavior in longitudinal reinforcement and concrete were observed and covered.
Theoretical calculations for the tested specimens according to different international standards included ACI, CSA and BS were presented with a comparison of the theoretical and experimental results.
Based on the presented study, the main conclusions are:
1- The failure mode of the columns was spalling of the concrete cover. Columns loaded with eccentric load failed by crushing and spalling the concrete at compression zone, with some horizontal cracks at tension zone, which increased with the increase of eccentricity.
2- Increasing the eccentricity to thickness ratio (e/t) reduced the ultimate load capacity of the column. Increasing the eccentricity to thickness ratio from zero to 0.45 leads to decrease in column ultimate load capacity by 65%.
3- Longitudinal steel reinforcement ratio influences effectively on the ultimate load capacity of the column in presence of eccentric loading. Increasing the longitudinal steel reinforcement ratio from 1.40% to 2.79% accompanies with increasing in column ultimate load capacity by 32% to 47%.
4- Increasing the confining reinforcement ratio leads to increase in column ultimate load capacity in presence of eccentric loading. Increasing the stirrups steel ratio from 1.60% to 2.00% results in increasing in ultimate load capacity of columns by 16%.
5- The prediction of columns’ ultimate loads using interaction diagram based on the CSA standard gave good agreement with most of the experimental results of the ultra high performance concrete columns under eccentric loading with experimental to standard ratio (Nexp/NCSA) ranges between 0.64 and 1.06.
6- The equations based on the ACI and BS standards gave overestimation theoretical values for the ultimate capacity of the eccentrically loaded columns.
6.3 RECOMMENDATIONS FOR FUTURE STUDIES
The followings are recommended for future research:
1- Further research is recommended to study the performance UHPFRC long columns loaded axially and eccentrically.
2- Research on the behavior of UHPFRC columns under different loading conditions as biaxial loading, cyclic loading, etc.
3- Research on the behavior of UHPFRC columns confined with spiral reinforcement under eccentric loading.
4- Further experimental research to study the effect of eccentricity on UHPFRC columns with high strength transversal reinforcement.
5- Further experimental research is suggested to study the axial strength behavior of strengthened UHPFRC columns.