Concrete-filled steel tube (CFST) piles with concrete pile caps have been successfully used by the Montana Department of Transportation (MDT) as cost-effective bridge foundations for short and medium-span bridges. While their performance under gravity loads is well understood, predicting their behavior under extreme lateral loads (e.g. seismic events) remains challenging with conventional design methods. Recent research at Montana State University developed a moment-rotation based methodology to predict CFST-to-cap connection capacity, but refinements are needed to improve its accuracy, particularly regarding the effects of U-bar reinforcement. Additionally, lack of standardized design details for CFST pile cap connections has led to inconsistencies in bridge designs and construction practices. Without standard details, engineers must custom-design each connection, which can result in variable performance and uncertain safety margins. There is a clear need to build upon the existing research findings to enhance the design methodology and provide uniform design guidance for these connections.
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