COMPARATIVE STUDY OF EARTHQUAKE RESISTANT PORTAL BRIDGE STRUCTURE USING FIXED BASE AND ROCKING SHALLOW FOUNDATION

• Main Author: Nanang Lutfian Putra, Moh.
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/62429
• Institution: Institut Teknologi Bandung

An earthquake resistant structure is a structure designed to have the ability to withstand earthquake forces by dissipating the energy of an incoming earthquake. In designing the bridge structure there are several energy dissipation mechanisms that can be applied. The system that commonly used is energy dissipation by allowing the formation of plastic hinges on the bridge pier elements, this system is known as the ductility concept. Another energy dissipation system is using an earthquake resistant structural system technology in the form of Lead Rubber Bearing (LRB) and/or others. The bridge is designed to rely on the concept of ductility, detailed column reinforcement to ensure the formation of plastic hinges at the bottom and/or top of the piers. Bridge designed with this concept may be safe against collapse, but susceptible to considerable damage and permanent lateral displacement. Furthermore, if using an earthquake resistant structural system device in designing a bridge, it has certain considerations before making it an alternative design. The price of device that relatively expensive is one of them. Based on these, in this research the use of a rocking shallow foundation will be studied which aims to provide an alternative design that can produce a more economical design. The design concept that will studied in this research is a bridge that used a fixed base support (ductility concept) and a bridge with rocking shallow foundation. The two design concepts will be compared with their seismic response through two methods, namely pushover analysis and non-linear time history analysis with 11 pairs of ground motion. Pushover analysis was carried out to determine the maximum performance of bridge structure and the performance of rocking shallow foundation used, while non-linear time history analysis was carried out to determine accurately how the performance and seismic response of the two bridge design concepts were compared. In this study, the bridge model with rocking shallow foundation through the foundation dimension design previously based on linear analysis response spectrum, determining the value non-linear spring constant using p-y curve method and determining the value of rocking performance limit based on the dimensions of the design result referring to ASCE 41-17 before being used in the pushover and non-linear time history analysis. The result of the research on two design concepts applied to a multi-span portal bridge structure consisting of simple span and continuous structural system that have varying height of piers are: a bridge structure with rocking shallow foundation produces a longer natural period compared to a fixed base bridge structure; natural period more longer causing the deformation that occurs increase compared to fixed base bridge; application rocking shallow foundation produces similar performance average to fixed based but can reduce axial force, shear forces and momments that occur in the pier of bridge; reduction of shear forces and momments can be utilized to optimize shear reinforcement and/or longitudinal reinforcement of bridge pier. Based on the overall result obtained, it can be concluded that the use of a design concept using rocking shallow foundation can reduce the stiffness of the bridge structure, however can produce better performance compared to a bridge fixed base (ductility concept).