Experimental Testing of Pile-to-Cap Connections for Embedded Pipe Piles

Abstract

For bridges supported by piles, acceptable system performance under seismic loading depends on effective pile-to-cap connections. A fixed pile-to-cap connection is often desirable to help control deflections during lateral loading when soft soils are present. While reinforcement bar cages that extend from the pile into the cap are effective in providing a fixed pile-to-cap connection, it is more economical to rely on pile embedment to provide fixity and moment resistance. This study investigated embedded pile-to-cap connections for concrete-filled pipe piles. Four full-scale specimens, each consisting of a cap with two piles, were investigated in the field under cyclic loading. The specimens had minimal reinforcement and varying amounts of pile embedment. Results show that the moment resistance of pile-to-cap connections can be significantly greater than what is typically calculated based on the flexural reinforcement and embedment bearing. Excess moment capacity may be explained by friction between the pile and the cap at the connection. This friction mechanism is described and discussed in the context of experimental results from other studies.