The Influence of Construction Joints on the Shear Behavior of Reinforced Self-Compacting Concrete Beams

الملخص

Construction joints are essential in massive concrete structures since these structures cannot be cast in a single pour. Nowadays, Self-compacting concrete is preferred due to its ability to compact without vibration and segregation concerns. The present research investigates the shear behavior of reinforced self-compacting concrete beams at the horizontal construction joint regions experimentally and analytically. The experimental works included testing twelve beams to investigate the effect of five test variables: construction joint position, compressive strength, main reinforcement, secondary reinforcement ratios, and the presence of dowels (shear connectors). Strain gauges were used in three locations to investigate the stress in the reinforcing bars. Tests showed that self-compacting concrete beams behave similarly to conventional concrete beams and self-compacting concrete beams without construction. That, the bottom of the compression zone was the optimum level for the construction joints. Increasing compressive strength reduced deflection. In addition, increasing the main reinforcement changed the failure mode from flexural to shear, separating the construction joint. While changing the secondary reinforcement results in totally different behavior since increasing secondary reinforcement changed the failure mode to flexural failure. While decreasing secondary reinforcement resulted in separation at the construction joint level. The results also showed that employing dense dowels impacted ductility because the deflection was reduced. While utilizing fewer dowels insignificantly affected the beam behavior. Further analytical investigations using finite element analysis (ANSYS program) were conducted to study the influence of utilizing high-strength concrete and the secondary reinforcement ratio on the behavior of reinforced self-compacting concrete beams. The analytical results indicated that the shear strength of self-compacting concrete beams was increased with the concrete strength and the secondary reinforcement ratio. Utilizing a 70 MPa high-strength concrete resulted in a 47.4 % ultimate load over the experimental value for regular-strength concrete (28 MPa). Increasing the ratio of secondary reinforcement (0.01229 to 0.049) resulted in a 10.3% increase in ultimate load magnitude. While decreasing the ratio of secondary reinforcement (0.01229 to 0.0025) with spanning the spacing between stirrups reduced the ultimate load magnitude by 55.8%.