Seismic Evaluation and Design of Petrochemical and Other Industrial Facilities

This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book provides practical guidance to engineers involved in the seismic design and evaluation of petrochemical and other industrial facilities. It addresses specific seismic related aspects of petrochemical facility design, evaluation, or operations. A number of available industry codes, standards, and specifications are normally used for the design of structures and components at petrochemical facilities. Emphasis is placed on providing information that will help the engineer understand the derivation and significance of different definitions of ground motion, which may be encountered on a project. The book also covers the evaluation of flat-bottomed steel storage tanks and addresses earthquake contingency planning for a facility. The book provides guidance where multiple codes must be evaluated on a project, in particular to international projects and vendors.

The design philosophy is derived from current knowledge of seismic hazards, observed and recorded behavior of structures and components during earthquakes, and consideration of consequences of failure of these structures and components. Available documents on recommended seismic design practices for conventional, as well as special facilities (ASCE 7-16 and FEMA 1050, 2015), have been used in the overall development of design and evaluation philosophies. The criteria in this chapter are based on performance objectives, defined for selected risk categories. The main elements of these performance objectives are structural integrity; containment; and functionality. Prior to construction of a project, whether a new facility or modification to an existing one, submittal to a local jurisdiction for the purpose of obtaining a construction building permit may be required. A complete permit application package, prepared by a registered design professional, will likely contain design drawings, calculations, and written inspection, observation, and quality assurance plans.

This chapter provides the necessary background information on techniques used to define and quantify seismic hazards. Hazards covered include ground shaking, excessive ground deformations or ground failure caused by fault rupture, liquefaction, and landslides and inundation of coastal areas and resulting damage caused by large waves produced in nearby bodies of water (tsunamis and seiches). Development of a site-specific design response spectrum includes consideration of regional tectonics, attenuation of ground motion with distance, and the influence of subsurface conditions at the site for which the response spectrum is being computed. In general, site-specific design response spectra can be computed through either a probabilistic seismic hazard analysis (PSHA) or a deterministic seismic hazard analysis (DSHA). Local site effects in PSHA or DSHA are either considered explicitly through a site response analysis or implicitly by using the appropriate GMPEs. This chapter provides brief descriptions of PSHA and DSHA procedures.

This chapter describes the overall methodology for performing seismic analysis of petrochemical facilities to obtain seismically induced loads. This is applicable to structural systems or subsystems to be used either in new design or in evaluation of existing facilities. The chapter is organized such that the main contents are written primarily for design of new facilities. It gives guidance for appropriate application of typical building code provisions to the types of structures and equipment commonly found in petrochemical facilities. Seismic building codes used in the past emphasized building structures and were developed with a primary focus on methods and earthquake experience from building performance. ASCE 7 incorporates seismic provisions developed through the NEHRP process specifically for use with nonbuilding structures. The chapter emphasizes application to nonbuilding structures not similar to buildings and provides guidance for using the seismic provisions of ASCE 7.

This chapter provides guidance for the seismic structural design of petrochemical facilities. The methods described are applicable to structures and components, including supports and anchorages of electrical and mechanical systems. The chapter addresses the earthquake load combinations to be used in design and the acceptance criteria to be met. The earthquake load combinations are derived mainly from IBC, ASCE 7, and PIP and are delineated to provide specific guidance for common structures and components at petrochemical facilities. The earthquake load combinations currently used by the petrochemical industry have also been considered. The acceptance criteria are defined by reference to accepted industry codes and standards. This chapter describes typical structures and components found in petrochemical facilities and provides special design recommendations for them. It also deals with physical interaction between structures and components, and the precautions that should be taken to minimize the negative effects.

A walkthrough or walkdown evaluation is the term generally applied to an on-site, mostly visual, screening review where as-installed components are methodically “walked down” and evaluated for potential seismic vulnerabilities. Using this method, it is possible to rapidly and cost-effectively identify the highest risk areas and prioritize further, more detailed evaluations that would be appropriate. This chapter provides practical guidance to engineers who will perform such evaluations. Petrochemical and other industrial facilities are increasingly being forced to demonstrate safety against toxic releases and pollution by mandates such as the California Accidental Release Prevention (CalARP) program requirements, OSHA regulations, and EPA regulations. A walkdown evaluation should be incorporated into a pre-startup safety review for new facilities. Walkdown techniques along with limited analytical evaluations have been used extensively in California petrochemical facilities rather than a nuclear-type methodology to satisfy CalARP and similar mandates since the early 1990s.

This chapter provides the reader with guidelines for designing new tanks and evaluating existing tanks for seismic loads. Emphasis is given, however, to evaluation of existing tanks. The information is mostly applicable to unanchored, flat-bottomed storage tanks at grade in areas of higher seismicity, with requirements to be de-rated for lower seismic areas. Although tank uplift is very common, sliding of tanks is rare and in general need not be considered a credible failure mode for storage tanks at grade. A walkthrough is an on-site visual screening, whereby “as-installed” components can be evaluated for seismic vulnerabilities. The chapter gives walkthrough evaluation guidance specifically for tanks. Anchorage details should be assessed during walkthrough inspection to ensure an adequate load path for the hold-down forces developed in the anchor bolts to be transferred from the tank shell to the foundation.

The primary purpose for assembling an earthquake emergency contingency plan is to have a rapid, rational, and structured response to a seismic event. This chapter covers the organization of personnel and resources for performing structural damage assessment and damage control. The key to effective response to any disaster situation is organization and planning before the event occurs. As likely scenarios could entail loss of water, loss of communications, loss of firefighting ability, inability to reach the site, release of hazardous materials, and others, it is imperative to take a proactive role in planning for any emergency. Some of the most critical areas to address are pre-event assessment of seismic risk, formal response plan, pre-earthquake training, and inspection materials. After performing the field inspections, posting buildings, and making structural evaluations, data and results must be assembled to report them to the incident commander.

This chapter addresses post-earthquake damage assessment of those facilities considered to be in need of structural investigation after the occurrence of an earthquake. After every significant seismic event, an immediate and complete walkdown of the petrochemical or other industrial facility in question would be the optimal response. However, although such action is strongly advised, this is impractical owing to cost and personnel constraints. For these reasons, two factors need to be considered with regard to the scope of post-earthquake damage assessments: prioritization of items to be assessed after an earthquake and determination as to what “size” of an event warrants an assessment. The performance of a post-earthquake damage assessment should be preceded by the safety-related actions. During pre-investigation activities, the inspection team should discuss and determine what areas of the plant, equipment, or components will be inspected and in what order.

This chapter presents guidelines to assist the design professional who is performing pre-earthquake seismic upgrading and modification of existing structures. These guidelines are intended only as recommendations to the engineer faced with a task of retrofitting seismically deficient structures. The guidelines cover both plant structures (i.e., nonbuilding), as well as buildings located within the plant facility. For both plant and building structures, it is suggested that the design professional obtain an up-to-date geotechnical report, review local seismicity, review original structural drawings and calculations, verify the vertical and lateral seismic force resisting systems, and identify potential weak links and structural deficiencies in the structural systems. Once a retrofit scheme is developed, it is recommended that the design professional review the scheme with the facility/plant owner and building official to determine any restrictions or issues associated with the retrofit and obtain their approval prior to any detailed engineering design work performed.

This chapter describes the seismic design and analysis of marine oil terminal wharves and piers. These structures are used to moor tank vessels and barges and to transfer liquid bulk petroleum products. The chapter also addresses pile-supported structures. The approach described is taken primarily from the California Code of Regulations, Title 24, Part 2, Chapter 31F, otherwise known as the Marine Oil Terminal Engineering and Maintenance Standards (MOTEMS), which specifically addresses marine oil terminals. As part of the California Building Code, MOTEMS is updated regularly and has adopted many of the provisions of ASCE 61. ASCE 7 provides minimum load criteria for design strength and allowable stress limits. Because wharf “failures” typically are the result of excessive deformations, not catastrophic collapse, the state-of-the-practice analysis and design methodologies are used with displacement-based methods rather than the conventional force-based design methods as described in ASCE 7.

Designers and owners are frequently confronted with situations where multiple codes might be used for the same application. This is prevalent on international projects, where local codes can differ significantly from a company’s own standards. This also occurs when international vendors request exceptions to project specific criteria to use design codes that are more familiar to the particular vendor or design codes that are embedded into design software. This chapter provides guidance for situations such as these, where the design engineer may be required to understand and evaluate multiple seismic design criteria or codes. Seismic design in general will require conformance to the governing local building code. Importance factors are treated in very different ways by different codes. For example, ASCE 7 uses a seismic importance factor directly that is often considered to be 1.25 for petrochemical and other industrial facilities, or for selected items within petrochemical and other industrial facilities.