DESIGN OF PRESTRESSED BOX GIRDER BRIDGE WITH FULL SHORING CAST-IN-SITU COSTRUCTION METHOD

• Main Author: Rahmadiani, Syavira
• Format: Final Project
• Language: Indonesia
• Subjects: Teknik (Rekayasa, enjinering dan kegiatan berkaitan)
• Online Access: https://digilib.itb.ac.id/gdl/view/44970
• Institution: Institut Teknologi Bandung

This thesis is based on the need of bridge constructions as supporting infrastructure of transportation system, specifically fly overs as one of vastly constructed bridges in big cities and developing areas. Fly overs usually have quite long main span which varies from 50 to 100 metres in length. Therefore, prestressed concrete box girder bridges have been the most popular choice because of their advantages for medium-long spanned bridges and also the esthetical aspect and spatial efficiency of box girders. In bridge designing, construction method gives a huge impact on the designing process itself since internal forces that occur are greatly affected by it on construction stage while external loads work after construction. This must affect the requirement and layout of tendons to resist working loads both in construction stage or service condition. Moreover, additional effect such as creep and shrinkage must be calculated when designing a concrete bridge with cast-in-situ method. In this thesis, we design a prestressed concrete box girder bridge with full shoring cast-in-situ method which consists of 3 spans, each consecutively has length of 45, 70, and 45 metres and height of 5 metres. The objective of this thesis is to determine the number and layout of tendons and reinforcement required for superstructure and also the dimensions and reinforcement required for substructure and foundation of the bridge to resist working load based on new standards from SNI. The results obtained from this design will be compared to the results from bridge design using cast-in-situ balanced cantilever construction method. vi The process of design is divided into several steps, the first is preliminary design including the dimension of box girder and piers which refers to AASHTO LRFD 2012 Bridge Design Specification. Secondly, calculate the loading based on RSNI 1725:201X to determine internal moments that work in the structure in order to determine the number and layout of tendons required. The next step is to do the bridge modelling using Midas Civil 2011 program that calculates more accurately by considering the effect of time-dependent material, loss of prestress in tendons, and response spectrum analysis caused by earthquake load listed in RSNI 2388:201X. The program analysis which resulted in girder stress is compared to stresses allowed by RSNI T-12-2004 to decide whether the tendons obtained from preliminary design can be used. After superstructure design is completed, the substructure and foundation are designed using internal forces calculated by Midas Civil. From the steps mentioned, we determine that the outer spans of the bridge require 18 tendons and the middle span requires 34 tendons. The box girder also requires transversal and longitudinal bending reinforcement-which provides shape for the girder, and shear reinforcement. Torsional reinforcement is not necessary because the box girder torsional resistance is high. The bridge itself is a statically undetermined structure where the supporting system on both piers are different. Pier 1 is hinged supported using guided and fixed bearing while pier 2 is roller supported using multi-directional and guided bearing. Both piers are typical which are 2,2 x 3 m in dimension however, because of the difference in supports, reinforcement required by both piers are different and so are the foundation below. The results of bridge design using full shoring construction method have several differences compared to balanced cantilever method. Loss of prestress in full shoring method is greater than in balanced cantilever method. However, total strands of tendons used in full shoring method is less than in balanced cantilever method. The same applies for shear reinforcement since the shear force that occurs vii in full shoring method is smaller. These things show that full shoring method is more economic in material aspect.