Title: Shear Transfer across Interface between New and Existing Concretes Using Large Powder-Driven Nails

Author(s): Dong-Uk Choi, James O. Jirsa, and David W. Fowler

Publication: Structural Journal

Volume: 96

Issue: 2

Appears on pages(s): 183-192

Keywords: concretes; pullout tests; shear connector; shear transfer

DOI: 10.14359/609

Date: 3/1/1999

Abstract:
Use of special powder-driven mechanical fasteners (nails) for shear transfer in bonded concrete overlays for bridge deck or pavement rehabilitation was experimentally investigated. The investigation consisted of nail pullout tests and interface shear transfer tests: 1) nail pullout strength was investigated with concrete compressive strength and existing crack or edge effects as test variables (366 tests); and 2) interface shear strength and mechanism of shear transfer with and without nails were investigated by pushoff tests using overlay specimens cast on slabs (76 tests). Test variables for the shear portion of the investigation were concrete strength, interface roughness, bonded versus unbonded interface, interface shear reinforcement, and crack effect. In the pullout tests, nail pullout strengths of 36.4 and 44.1 kN were determined in a normal strength concrete (fc= 28 MPa) and a high-strength concrete (fc= 51 MPa), respectively. The pushoff test results indicated that nails were effective in improving the shear strength of bonded-rough interfaces. Overlay specimens with two nails and a contact area of 465 cm2 (interface shear reinforcement ratio = 0.38 percent) had 10 to 16 percent higher strength than comparable overlay specimens without nails. An unbonded-rough interface with nails effectively resisted the shear force. No premature nail failure in pullout was observed in any pushoff tests, which indicated that the development of the pullout resistance by the large powder-driven nails used as shear connectors was adequate.