Concrete Filled Steel Tube Piles to Concrete Pile-Cap Connections: Fid-Bau Portal

Concrete Filled Steel Tube Piles to Concrete Pile-Cap Connections

Kappes, L. / Berry, M. / Stephens, J. / McKittrick, L.

This paper describes preliminary findings from a Montana Department of Transportation (MDT) funded project focused on testing the seismic performance of concrete filled steel tube (CFT) pile to concrete pile-cap connections. These connections are common/critical components of the support structure for highway bridges in Montana and across the country, and it is essential for these connections to perform well during seismic events. Despite their widespread use, the design and expected performance of these connections are not necessarily well understood. The preferred failure mechanism for this connection is for the pile cap to possess sufficient capacity to force the connection failure into the more ductile CFT piles. Traditional design methods for this connection often lead to congested and complex reinforcing schemes, and this complexity can obscure the true behavior/effectiveness of the elements within the connection. In this research effort, nine half-scale connections were tested under a monotonic pushover load until failure. The piles were then cycled through several load reversals. As a result of this research effort, a new reinforcing scheme was developed that greatly simplifies the design and construction of the connection while increasing the capacity of the cap. This newly developed reinforcing scheme includes U-shaped reinforcing bars that encircle the embedded CFT piles within the cap that counteract the moment related demands introduced by the embedded pile. In particular, this paper presents the details and results of the nine specimens tested during this research effort. Data collected during these tests includes load, deformations, and strains. The structural efficiency of the newly developed reinforcing scheme is discussed and contrasted with conventional reinforcing schemes. Additionally, future directions of this research effort are presented.