Pullout test for PC column-capital grouted rebar connection with corrugated duct

Abstract

Double-beam precast concrete (PC) structures require large capitals to support a wide PC girder. In this study, a segmented PC column-capital system is developed to overcome the disadvantages of conventional PC columns in terms of manufacturing, transportation, and construction. In the proposed segmented PC column-capital system, large PC capitals are assembled with PC columns using the proposed corrugated rebar connections filled with grouted mortar. To verify the load-transfer capacity of the proposed corrugated rebar connections, pullout load tests are conducted under various test parameters, including the mortar compressive strength, curing time, bond length, and embedment length. To enable rapid construction, a relatively short curing time of 1-2 days is addressed. The test results indicate that the pullout performance of the proposed corrugated rebar connection is primarily affected by the mortar compressive strength f(m)' and embedment length l(d). When f(m)' > 7.9 MPa and l(d) = 800 mm, the proposed corrugated rebar connection transfers tensile loads corresponding to construction loads. When f(m)' > 21.0 MPa and l(d) = 800 mm, the proposed rebar connection can resist the tensile yielding load of the connected vertical rebar even after one-day of curing. However, when l(d) is less than 800 mm, bond-slip failure occurs because of the insufficient bond length. Based on the test results, a parametric analysis is conducted using a finite-element model. Similar to the experimental result, the numerical result shows that the bond strength of the proposed rebar connections is significantly affected by f(m)' and l(d). Hence, a bond-strength model of less-hardened grouted mortar with a bond stress of tau(b) = 0.20 f(m)' is suggested based on the previous and present test results as well as parametric analysis results.