WP4. Performance-based Engineering framework for industrial structures

The scope of this WP is to formulate a Performance-Based Earthquake Engineering (PBEE) framework for industrial equipment structures. This is a key WP that will exploit all the results obtained in previous WPs (WP2 and WP3), and will provide the necessary data for the reliability and risk assessment procedures that will be developed in the WPs that follow. 

As a first step, appropriate performance levels, also referred as “limit-states” (i.e operational, heavy damage, collapse prevention) will be established, taking into consideration a series of parameters such as the type of industrial facility, its significance relative to the whole industry and its content (toxic, flammable). These performance levels will provide the relationship between the seismic response and capacity of an industrial facility structure with respect to its operational requirements and will be based on research experience, existing literature, current design codes/guidelines, and a series of numerical analyses.

Table 1 Major modes of failure for liquid storage tanks, pressure vessels and industrial piping.

Liquid storage tanks

• Elephant’s foot buckling and sloshing buckling (Figure 7a),  
• Failure of floating roof (Figure 7b), 
• Excessive deformation or rupture on the tank base plate, 
• Failure of tank anchor bolts, 
• Excessive distortion or rupture at the tank nozzle area.

Pressure vessels

• Local deformation of vessel wall at the support area, 
• Failure and loss of support, 
• Excessive distortion or rupture at the vessel nozzle due to attached equipment.

Industrial piping

• Local buckling and/or fracture at the pipe elbows, 
• Failure of pipe racks and loss of piping support structure (Figure 8a), 
• Loss of connection between the pipes and the supporting structure (Figure 8b), 
• Failure of flanges – bolted connections, 
• Weld fracture.

In addition, it is necessary to determine the possible failure modes for every industrial equipment structure considered and link them with the performance levels. These failure (or damage) modes must be mapped with appropriate Engineering Demand Parameters (EDPs), which are response parameters (e.g. displacements, stresses, strains, or stress resultants) calculated at critical locations of the structure. A list of possible failure modes for different industrial structures is shown in Table 1. The selection of EDPs will be based on engineering judgment, collecting information from previous earthquake events, current state of practice and through a series of numerical analyses using the numerical models of WP3.

The research team of the UTh will lead this WP. Apart from UTh, the NTUA and the Institute of Engineering Seismology and Earthquake Engineering (ITSAK) teams will participate. The UTh has pioneered the research on the analysis and response assessment of industrial structures (Karamanos et al. 2006a, 2006b, 2009, Varelis et al. 2011, Pappa et al. 2011, Diamanti 2011), while the NTUA and ITSAK teams have extensive experience on PBEE (Vamvatsikos & Cornell 2002, Mochonas et al. 2009, Fragiadakis & Vamvatsikos 2011). 

Key intermediate goals: For every type of industrial facility structure: identify damage modes, establish performance levels; propose appropriate EDPs and their limit-state threshold values.