(ANALYSIS FOR PERFORMANCE-BASED DESIGN OF STEEL STRUCTURES EXPOSED TO FIRES : CASE OF STUDY OFFSHORE PLATFORM)

• Main Author: HAMIDAH (NIM : 25003086), MARIE
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/20268
• Institution: Institut Teknologi Bandung

Offshore platforms for oil and gas production are prone to fires, therefore it is important to design a fire resistant offshore structure. Fires affect both material and the overall structural system performances. Thus a study of material capacity and overall structural system due to fire hazard needs to be conducted. Recently, a Performance-based design method analysis has been developed as a new design method to verify the fire resistance of a structure element. This thesis investigates performance-based analysis for fire resistance offshore structure and evaluates a real case study of offshore platform exposed to fire. <br /> The investigation and application of the fire resistance performance based design method includes definition of performance criteria, reconstruction of fire scenario and verification by nonlinear analysis. In the verification, nonlinear analysis is performed to simulate the actual condition. First, the steel offshore platform exposed to static load and fire load is modeled, then the performance-based analysis is used to examine the response of the structure due to fire load. The reliability of the performance based analysis to determine the fire resistance of the structure is also verified. The analysis result of the case study is then compared to the prescriptive method. <br /> The analysis shows that the offshore steel structure without any fire protection can survive an extreme fire incident and satisfy the performance criteria. The analysis also shows that after exposed to fire, the investigated structure can resist the extreme environmental load (storm) and ductility level earthquake without. <br /> Based on the results, it can be concluded that the performance criteria could be achieved within the following conditions: The platform structure is placed in open space (external fire) therefore the maximum temperature that occurs is lower than the fire temperature in compartment/closed area; Since platform is an offshore structure, therefore the heat can be absorbed by the sea; At the riser area, there is a fire wall and security system in form of riser valves which will be immediately closed whenever a fire occurs and the gas between the valves will then fade away. Thus, a fire protection is not necessarily whenever there is an extreme temperature loading, as long as there is a sufficient reserved capacity at members that are close potential fire source. This reserved capacity can be in the form of low stress ratio at operational condition or/and redundancies of the structure. The structural redundancies are important to the ability of the structure to redistribute the stress without any serious consequences. Protection to fire hazard which is required by prescriptive method is not an absolute requirement that has to be done, because without protection, offshore steel structure which has been exposed to fire still can perform even in environmental storm condition. Fire protection need to be applied only at potential members which are exposed to fire such as riser, conductor, and structural members closed to fire sources for economical reason.