Civil Insight: A Technical Magazine Volume 3 | Page 57

Civil Insight (2019) 57-63 Civil Insight: A Technical Magazine Comparison of Axial Load Distribution on Bridge Pile Foundation under Different Analysis Procedures 1,* Asim Gautam, 2 Shakil Manandhar, 3 Kameshwar Sahani 1 Student, 2 Deputy ME in Structural Engineering, Kathmandu University, Nepal, [email protected] Team Leader, Local Roads Bridge Program, Lalitpur, Nepal, [email protected] 3 Lecturer, Kathmandu University, Nepal, [email protected] Abstract This paper considers the structural aspects of pile foundation by comparing the axial load distribution on bridge pile foundation when analyzed by the Classical Method and the Finite Element Method (FEM). 3D numerical model of the pile group was made using SAP2000. The axial loads at piles at the base of the pile cap were compared and the results were established. While comparing the distribution of axial loads at the pile, the Classical Method was found to underestimate the design load when compared with the FEM model. This leads to a finding that the Classsical Method of load distribution may not be sufficient to predict the design loads of the pile foundation group. Keywords: Axial load distribution, Bridge pile foundation, Pile group, Finite Element Method (FEM), Classical Method 1) Introduction Bridges are critical infrastructure in transportation network as they provide connections over the obstacles like rivers. Among the components of the bridge, bridge foundation is the most vulnerable as the foundation comes in direct contact of the soil. As the soil properties are less predictable in nature, a number of bridge foundation failures have been observed in the past few decades. It has been estimated that 60% of all bridge failures result from scour and other hydraulic-related causes (Kattell & Eriksson, 1998). To counter the scouring problems in bridges, deep foundations are a must. The deep foundations include well foundation and pile foundation. Due to the ease of construction and the availability of equipment, bored cast in-situ concrete piles are primarily used in Nepal. Local Roads Bridge Program (LRBP) is the program coordinated by the Department of Local Infrastructure (DoLI), supported by Swiss Agency for Development and Cooperation (SDC) to provide technical assistance to the states and local levels in motor-able bridge construction. According to LRBP, the structural design of bridge pile foundations (bored cast in-situ) are designed using the classical approach of load distribution and codal provisions of IS 2911 (Part 1/Sec 2). The failure of bridge foundation in the past, like the one in Jhulaghat across Babai River, has prompted the need for assessing the alternative methods of structural analysis and design. In design of bridges, the axial load that needs to be resisted by a pile is one of the most important parameters required for pile design. For the study, the axial load that needs to be resisted by a pile in a group of piles was calculated using the Classical Method of distribution of loads coming to the pile foundation. This study aims to examine whether the classical approach of load distribution in piles predicts the design axial load adequately. Thus, 3D numerical modeling using the FEM-based software SAP2000 (SAP2000, 2015) was *Corresponding Author Email address: [email protected] (Asim Gautam) Submitted on October 5, 2019; Accepted on December 15, 2019 57