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SOIL-STRUCTURE INTERACTION OF FRP PILES IN INTEGRAL ABUTMENT BRIDGES
Amde, Amde M
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The rapid degradation of conventional material piling is one of the major problems in the bridge and civil infrastructure industry. Conventional construction materials have major disadvantages that increase their maintenance cost and reduce their service life especially in aggressive environments. The use of advanced composite materials such as Fiber Reinforced Polymers (FRPs) offers a better alternative to conventional building materials in terms of strength, weight, durability, and life cycle cost. Integral abutment bridges are a special type of bridges that are built without bearings or expansion joints. These bridges are usually subjected to cycles of expansion and contraction that causes horizontal movements of the pile foundations. Accommodating such movements requires some flexibility in the piling system. Fiber reinforced composites (FRPs) have the strength and flexibility and can be custom designed as needed. An extensive literature and market survey indicated that composite materials are increasingly being considered for use in civil infrastructure applications ranging from the retrofit and rehabilitation of buildings and bridges to the construction of new structural systems. Very little research has been conducted on FRPs as piling materials. The current research investigates the use of fiber reinforced composites as piling materials for jointless bridges. Three-dimensional finite element models were developed and analyzed using the multi purpose FEM package ANSYS. The models were built to take into consideration multiple design parameters including the non-linear behavior of soil and concrete and the orthotropic behavior of unidirectional composites. Investigation results showed that FRP composites are good candidates for use in piling systems. Because of their flexibility in both geometrical shaping and layer lay-up, FRPs provide more options to designers to come up with suitable systems based on their needs. A new pile section is introduced to be used with or without concrete filling. The section consists of two flanges and a double web to allow flexibility in controlling the size of concrete filling between the webs. Analysis results showed that flexibility of the geometry of the new pile section and the flexibility of tailoring multi-layered unidirectional FRP composites make the pile customizable for best performance. FRP composites lend themselves to be optimized to achieve desired properties. The study showed that favorable stiffness and stress results can be obtained for composite piles in integral abutment bridges by optimizing the section's geometry while keeping a fixed cross-sectional area.