The Effectiveness of Hooks for Plain Steel Reinforcement
Date
2020-09-14
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
0000-0002-3992-4564
Type
Thesis
Degree Level
Masters
Abstract
As buildings age, their structural integrity must be assessed and reassessed at regular intervals to ensure the safety of their continued use and to advise on retrofits and repairs necessary for preventative maintenance and responsive repair. Historic buildings often contain plain reinforcement whereas modern buildings exclusively contain modern deformed reinforcement. Younger engineers in particular have not been trained with or worked with plain bar. Modern American Concrete Institute (ACI) and Canadian Standards Association (CSA) Group codes largely do not contain adequate provisions to assess the structural integrity of many historic buildings.
Twenty-four beam-column joint specimens with four different hook configurations were tested under tension to compare the anchorage capacities of embedded plain and modern deformed 90° and 180° hooked bars. Six replicates of each configuration were tested to determine whether statistically significant differences at the 95% confidence level existed between the anchorage capacities of plain versus modern deformed hooked bars. Visual observations were documented manually to assess differences between crack patterns and observed failure modes.
Typical cracking patterns were observed for groups of both specimens containing 90° and 180° hooks. The degree of cracking observed aligned with results of similar studies. All specimens with 90° hooks failed by side blowout whereas those with 180° hooks failed by front blowout. No evidence of group effects (i.e. decreased anchorage capacity) was observed. Statistically significant differences in maximum normalized tensile load at the 95% confidence level were observed between 90° plain and modern deformed bars, wherein the plain bars had a 3.8 kN/MPa lower maximum; 180° plain and modern deformed bars, wherein the plain bars had a 5.6 kN/MPa lower maximum; and 90° and 180° modern deformed hooked bars, wherein the 90° bars had a 4.0 kN/MPa lower maximum. No statistically significant differences in displacement at maximum normalized load were observed.
An extensive replicate-based study of plain hooked bar incorporating additional parameters (e.g. lead length, bend angle, etc.) is recommended. The value of the recommended work is in determining the sensitivity of hooked bar performance to variations in these parameters.
Description
Keywords
Plain bar, Concrete, Hooks
Citation
Degree
Master of Science (M.Sc.)
Department
Civil and Geological Engineering
Program
Civil Engineering