Comparative study of different methods for superstructure-foundation interactions




Sharma, Prakriti

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Bridge failures in the past decade due to structural deficiencies demonstrated the clear need for a review of the current bridge analysis approaches. This study focuses on pile-supported bridges under predominantly static loading. A critical review of the current analysis approaches was performed. It was concluded that in the absence of an onerous iteration process, the current approaches often produce inaccurate and, in many cases, unsafe results since the interactions between superstructure and foundation are not fully considered. To address the inherent limitations of the current approaches, a computer program [Soil Spring Module (SSM) 2.0] was developed as a part of the study. SSM 2.0 can be used in conjunction with a frame analysis program to capture nonlinear load transfer from foundation elements to soil in different directions simultaneously. STAAD.Pro was selected for demonstration in this study. Using SSM 2.0 and STAAD.Pro, this study proposes a new analysis approach using the Integrated Analysis Process (IAP). The same methodology can be applied in other frame analysis programs. Kansas Bridge 45 was selected as a case study. Using the IAP approach, a series of integrated analyses including all superstructure elements (e.g., deck, girders and piers) and all foundation elements (e.g., pile caps and piles) were performed on Kansas Bridge 45 for different soil types and properties. Different from the conventional approaches, the full interactions between superstructure and foundation were considered simultaneously in a single analysis using the IAP approach. The analysis results from the IAP approach and the conventional approaches were examined. The advantages of the IAP approach were identified. Comparing to the conventional approaches in current practice, the proposed IAP approach does not involve crude assumptions or intensive iterations. Using the IAP approach, design engineers can complete structural and foundation analysis of pile-supported bridges with good accuracy in a timely manner. The same methodology can potentially be applied to other structure types.



Pile foundation, superstructure-foundation interaction, bridge, soil-structure interaction, STAAD.Pro, Integrated bridge analysis, soft clay, stiff clay, soil- pile-structure interaction, soil springs, superstructure stiffness, Davisson and Robinson, superstructure response, foundation response, p-y, t-z, q-z