Strain Limits for Concrete Filled Steel Tubes in AASHTO Seismic Provisions.

摘要

Reinforced concrete filled steel tubes (RCFSTs) are commonly used as bridge pipe piles in high seismic regions. The pipe piles in high seismic regions. The pipe-piles consist of reinforced concrete encased in a steel tube. The steel tube is used as a permanent casing which eases construction. The concrete is confined by the steel tube, increasing the compressive strength, and the concrete core prevents the steel tube from buckling inward. This research program presents experimental test performed on twelve large scare RCFSTs. The pipepiles were subjected to reversed cyclic four-point bending with a constant moment region centered in the pile. The tests focused on two variables: (1) diameter to thickness ration and (2) internal reinforcement ratio. The large scale specimens consisted of outer diameters of 20-24 inches and diameter-to-thickness rations between 33 and 192. The thin walled piles were tested with varying internal reinforcement ratios ranging from 0.78% to 2.43%. The effect of D/t ratio and internal reinforcement ratio on the initiation of buckling and rupture, ductility, damping, and strain compatibility were determined. Analyses were performed to compare the curvature distribution and plastic hinge length of RCFSTs and convention reinforced concrete columns. A finite element model was created to capture the monotonic response of the specimens.