Pushover analysis in slab-on-piles bridge using reinforced concrete-filled spun piles

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Slab-on-piles is a bridge structure consisting of a continuous pile as a pier, pile head, and slab. Generally, the spun pile is chosen as the pile pier because of the quick construction and low maintenance. However, due to the hollow section with prestressed concrete, without filler, it has weakness in the form of brittle failure under bending moment and shear. Some studies mention that the initial failure occurs due to an explosion in the inner surface of the hollow spun pile or on the surface of the hole. The implementation spun pile for the slab-on-piles bridges should consider that behavior. Therefore, some practical engineers usually use concrete-infill treatment, however, the performance improvement in the nonlinear behavior needs to be known. This study investigates the use of hollow spun piles filled with concrete and normal reinforcement for a slab-on-piles bridge structure. This type of spun pile will be referred to as a reinforced concrete-filled spun pile (RCFSP). The location of slab-on-piles bridge is assumed to be built in Aceh, Indonesia. The height of the RCFSP on the slab-on-piles bridge is 6 m relative to the ground surface. A preliminary design using the linear elastic method is conducted using the response modification factor of 3.5. The slab-on-piles bridge requires 25 RCFSP for each bridge segment. Based on the pushover analysis method, this structure could not reach a performance point. A redesign is conducted using a response modification factor of 1.5. The redesign result shows that the structure requires 60 RCFSP and a performance point is found at a displacement of 85 mm in the longitudinal direction and 81 mm in the transversal direction. This research concludes that a slab-on-piles bridge is not efficient to be designed with a high value of response modification factor even though using the concrete-infill treatment.