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    Fundamentals of Soil Structure Interaction Analysis for Integral Bridges

    BLOG BRIDGE INSIGHT

     

    Soil-Structure interaction (often referred to as SSI) is required when structural and ground displacements are depended of each other.  It is usually required when the relation between soil and structure stiffness are comparable. On those cases a coupled structure-soil model is required. 

     

    This 1-hour case study covers the theoretical background of soil interaction analysis with application methods according to PD 6694-1:2011. Attendees can get many useful knowledge on integral bridge design.

     


    Key Points

      

    1. Background of Soil-Structure Interaction

    From this session, 3 analysis method, Limit Equilibrium Analysis, Spring Analogy, and Continuum Media will be presented with its characteristics. Practical design method and important notes for flexible foundation, laterally loaded piles, and retaining structures under laterally loaded pressure.

    2. Design of Integral Bridges

    Methods of analysis according to PD 6694-1 and example for integral bridge on piled abutments will be explained and demonstrated.

     


     

    Approaches of Soil-Structure interaction

     

    In order to consider soil-structure interaction, 3 approaches can be applied: Linear equilibrium method, spring analogy, and continuum media.

     

    Limit equilibrium analysisSpring Analogy

    Continuum media


     

    Flexible Foundations and Laterally Loaded Piles

     

    For flexible foundations and laterally loaded piles, spring analogy can be applied with Winkler spring or p-y curve. Both can be simulated in midas Civil by “Surface Spring Support” and “Point Spring Support” feature.

     

    Spring analogy: Uncoupled springs - Winkler model

    P-y curves

    P-y curves 2


    Retaining Structures

     

    For retaining structures, lateral load pressure can be calculated and applied. For this, different formulations can be applied such as Rankine theory, Eurocode7, etc. In midas Civil, this approach can be applied by applying external loads, and adding nonlinear springs.

     

    Retaining structures 1

    Retaining structures 2

    Retaining structures 3

    Retaining structures 5

    Retaining structures 6


    Integral Bridges

     

    Finally, for integral bridges, both linear equilibrium and soil-structure interaction analysis can be used depending on the structure type. When applying linear equilibrium in midas Civil, external pressure load can be applied to the abutment. 

     

    Methods of analysis

    Soil-structure interaction

    Integral Bridges


    Watch the Case Study Here

     

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    About the Author
    Pere Alfaras | Principal Bridge Engineer | Arcadis UK

    Alfaras is a Principal Bridge Engineer at Arcadis UK with 10+ years of experience in bridge and structural design. He has been a lecturer for Finite Element Method of Civil Structures at the UPC/Barcelona Tech for 5 years. Some of the projects Alfaras has been involved in include the Lower Thames Crossing in UK and the "Eix Diagonal" Motorway in Spain. 

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