Omid Taheri - M.S., Imam Khomeini International University, Civil Eng. Dept., Qazvin, Iran
Reza Ziaie Moayed - Associate Professor, Imam Khomeini International University, Civil Eng. Dept., Qazvin, Iran
Mohammadamin Nozari - Ph.D. Student, Imam Khomeini International University, Civil Eng. Dept., Qazvin, Iran

Soil-structure interaction is one of the most important factors in theanalysis; especially for complicated problems such piles aresubjected to different loads. Owing to the sensitivity of pile designand analysis to geometry, loading type and soil behavior, it isunavoidable to consider the soil-structure interaction. Usingsubgrade reaction approach is one of the most practical method inpredicting the deflection and bearing capacity of piles subjected tolateral loads. Therefore, it is necessary to predict the exact value ofmodulus of subgrade reaction. Many full-scale pile test have beenperformed in order to investigate the behavior of lateral resistanceon cast-in-place concrete piles. Finite element (FE) methods alsocan be applied to predict the variation of horizontal subgradereaction (

Modulus of horizontal subgrade reaction, Back-analysis method, Lateral pile behavior, Soil-pile interaction