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2024-05-10

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Accelerated bridge construction (ABC) has recently gained popularity among state departments of transportation to minimize construction costs, time and waste, and optimize the use of materials. This research focused on the connection details between hollow-core fiber-reinforced polymer concrete-steel columns (HC-FCS) and their foundations. The column consists of a concrete core sandwiched between an outer fiber-reinforced polymer (FRP) tube and an inner steel tube. Two foundation anchorage details were tested with multiple embedment lengths into the footing to evaluate the connection's capability to transfer axial load and bending moment and achieve the ultimate column flexural and shear capacities. Seven column-footing specimens were cast and tested to failure to study the effect of embedment length, diameter-to-thickness ratio, compressive strength of the concrete footing, and end-of-column anchorage on monolithically cast connection capacity. Two specimens utilizing a socketed connection filled with ultra-high performance concrete (UHPC) designed to represent connection of precast elements were cast and tested to failure. The specimens were designed to be tested as a simply supported beam using a typical load frame by constructing each 2 ft by 2 ft by 4 ft-1 in. footing with a column portion embedded at the desired embedment length at each end of the footing. The column portion of the specimen was in the form of only a steel tube. An 8.625 in. diameter steel pipe with a thickness of 0.219 in. was used for eight specimens, while a 6.625 in. diameter steel pipe with a thickness of 0.25 in. was used for one specimen. Embedment length had a significant effect on the performance of the column-footing connection. The short embedment lengths tested (1.6Di and 1.68Di) were not sufficient to develop the steel pipe flexural strength for the monolithic connection specimens with a normal-strength concrete footing. However, the use of socketed connection with UHPC, high-strength concrete footing, and welding a series of lugs to the embedded pipe prevented the steel pipe from pulling out to some extent, and local buckling occurred in the steel pipe at a moment greater than the calculated capacity of the steel pipe with an embedment length of 1.6Di. The 1.8Di embedment length prevented the steel pipe from pulling out whether using the socketed connection with UHPC, high-strength concrete, or normal-strength concrete. The specimens with this longer embedment length failed after exceeding the flexural strength of the steel pipe, and local buckling occurred in the steel pipe. This suggests that the column-footing connection with a 1.8Di embedment length is potentially sufficient to achieve the flexural strength capacity of the steel pipe.

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Accelerated Bridge Construction, Connection, Engineering, Civil., Substructure

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