W L IND OADS FOR P O ETROCHEMICAL AND THER I F NDUSTRIAL ACILITIES PREPARED BY Task Committee on Wind-Induced Forces of the Petrochemical Committee of the Energy Division of the American Society of Civil Engineers 1801 ALEXANDER BELL DRIVE RESTON, VIRGINIA 20191–4400 Cataloging-in-Publication Data on file with Library of Congress American Society of Civil Engineers 1801 Alexander Bell Drive Reston, Virginia, 20191-4400 www.asce.org/pubs Any statements expressed in these materials are those of the individual authors and do not necessarily represent the views of ASCE, which takes no responsibility for any statement made herein. No reference made in this publication to any specific method, product, process, or service constitutes or implies an endorsement, recommendation, or warranty thereof by ASCE. The materials are for general information only and do not represent a standard of ASCE, nor are they intended as a reference in purchase specifications, contracts, regulations, statutes, or any other legal document. ASCE makes no representation or warranty of any kind, whether express or implied, concerning the accuracy, completeness, suitability, or utility of any information, apparatus, product, or process discussed in this publication, and assumes no liability therefore. This information should not be used without first securing competent advice with respect to its suitability for any general or specific application. Anyone utilizing this information assumes all liability arising from such use, including but not limited to infringement of any patent or patents. ASCE and American Society of Civil Engineers—Registered in U.S. Patent and Trademark Office. Photocopies and permissions. Permission to photocopy or reproduce material from ASCE publications can be obtained by sending an e-mail to [email protected] or by locating a title in ASCE’s online database (http://cedb.asce.org) and using the “Permission to Reuse” link. Bulk reprints. Information regarding reprints of 100 or more copies is available at http://www.asce.org/reprints. Copyright © 2011 by the American Society of Civil Engineers. All Rights Reserved. ISBN 13: 978-0-7844-1180-3 Manufactured in the United States of America. 16 15 14 13 12 11 1 2 3 4 5 6 7 ASCE Petrochemical Energy Committee This publication is one of five state-of-the-practice engineering reports produced, to date, by the ASCE Petrochemical Energy Committee. These engineering reports are intended to be a summary of current engineering knowledge and design practice, and present guidelines for the design of petrochemical facilities. They represent a consensus opinion of task committee members active in their development. These five ASCE engineering reports are: 1) Design of Anchor Bolts in Petrochemical Facilities 2) Design of Blast Resistant Buildings in Petrochemical Facilities 3) Design of Secondary Containment in Petrochemical Facilities 4) Guidelines for Seismic Evaluation and Design of Petrochemical Facilities 5) Wind Loads for Petrochemical and Other Industrial Facilities The ASCE Petrochemical Energy Committee was organized by A. K. Gupta in 1991 and initially chaired by Curley Turner. Under their leadership the five task committees were formed. More recently, the Committee has been chaired by Joseph A. Bohinsky and Frank J. Hsiu. The five reports were initially published in 1997. Buildings codes and standards have changed significantly since the publication of these five reports, specifically in the calculation of wind and seismic loads and analysis procedures for anchorage design. Additionally, new research in these areas and in blast resistant design has provided opportunities for improvement of the recommended guidelines. The ASCE has determined the need to update four of the original reports and publish new editions, based on the latest research and for consistency with current building codes and standards. The ASCE Petrochemical Energy Committee was reorganized by Magdy H. Hanna in 2005 and the following four task committees were formed to update their respective reports: • Task Committee on Anchor Bolt Design for Petrochemical Facilities • Task Committee on Blast Design for Petrochemical Facilities • Task Committee on Seismic Evaluation and Design for Petrochemical Facilities • Task Committee for Wind Load Design for Petrochemical Facilities Current ASCE Petrochemical Energy Committee Magdy H. Hanna Jacobs Engineering - Chairman William Bounds Fluor Corporation John Falcon Jacobs Engineering James R. (Bob) Bailey Exponent, Inc. J. G. (Greg) Soules CB&I iii The ASCE Task Committee on Wind-Induced Forces This report is intended to be a state-of-the-practice set of guidelines. It is based on reviews of current practice, internal company standards, published documents, and the work of related organizations. The report includes a list of references that provides additional information. The reference list emphasizes readily available commercial publications and government reports. This report was prepared to provide guidance for determination of wind induced forces on structures found in petrochemical and other industrial facilities. It should be of interest to engineers familiar with design of industrial type structures and the application of ASCE 7, “Minimum Design Loads for Buildings and other Structures,” to these types of structures. In helping create a consensus set of guidelines, a number of individuals provided valuable assistance and review. Reviewers included John Geigel (ExxonMobil), Drew Troyer (ConocoPhillips), and Eric Wey (Fluor Corporation). The committee is appreciative of the efforts of these reviewers. The task committee would also like to acknowledge the numerous contributions made to this task committee and other technical committees over the years by both Michael Bergeron (SNC Lavalin – GDS Engineers) and Mike Chen (Fluor Corporation). Both Michael and Mike passed away during the preparation of this report update and will be sorely missed by the committee and the broader engineering community. Finally, the committee would also like to thank Judy Falcon (Exponent, Inc.) who patiently and diligently edited the manuscript and put up with all of our changes. iv The ASCE Task Committee on Wind-Induced Forces James R. (Bob) Bailey Richard T. Gilbert Paul B. Summers Ph.D., P.E., F. ASCE P.E. P.E., S.E. Exponent, Inc. ExxonMobil Research & MMI Engineering Engineering Company Chairman Co-Chairman Secretary Samuel D. Amoroso, Ph.D., P.E. Engensus Engineering & Consulting K.C. Fong, P.E. URS Corporation Javier Garza, P.E. Shell Madgy H. Hanna (Past Co-Chairman) Jacobs Engineering Don Harnly, P.E. Jacobs Engineering Kirby Hebert Louisiana State University Marc L. Levitan (Past Chairman) Louisiana State University Guzhao Li, Ph.D., P.E., S.E. MMI Engineering Gerald W. Mayes, P.E. The Shaw Group Rajendra Prasad, P.E., PMP Mustang Engineering, L.P. Norman Rennalls, P.E. Shell Amy Styslinger, P.E. ExxonMobil Upstream Research Company Walter A. Waller, P.E. Bechtel Corp James H. Wissehr, P.E., S.E. Jacobs Engineering Silky S.K. Wong, P.E., S.E. Fluor Corporation Randall L. Wright, P.E., S.E. Mustang Engineering, L.P. Gregory B. Young, P.E. ConocoPhillips v This page intentionally left blank Table of Contents Chapter 1: Introduction .................................................................................................... 1 1.1 Background ....................................................................................................... 1 1.2 State of the Practice .......................................................................................... 2 1.3 Purpose of Report ............................................................................................. 2 Chapter 2: Background .................................................................................................... 3 2.1 Introduction ....................................................................................................... 3 2.2 Key Wind Engineering Concepts .................................................................... 3 2.3 Aerodynamics of Open Frame Structures ....................................................... 9 2.4 Aerodynamics of Partially Clad Structures ................................................... 10 2.5 Aerodynamics of Vertical Vessels ................................................................. 11 2.6 Other Wind Loading Codes, Standards, and Guides .................................... 14 2.7 Research Progress and Future Needs ............................................................. 15 Chapter 3: Review of Existing Design Practices ......................................................... 18 3.1 Introduction ..................................................................................................... 18 3.2 Survey of Existing Practices and Impacts of First Edition Guidelines ........ 18 3.3 Existing Design Practices for Structures New to Second Edition ................ 21 Chapter 4: Recommended Guidelines Part I: Design Considerations and Methods ..................................................................................................................... 31 4.0 Introduction ..................................................................................................... 31 4.1 Historical Performance ................................................................................... 31 4.2 Wind Tunnel Testing ...................................................................................... 43 4.3 CFD Commentary .......................................................................................... 45 4.4 Load Combinations ........................................................................................ 46 4.5 Special Considerations for LNG Facilities .................................................... 55 4.6 Evaluation of Wind Loads on Existing Structures ........................................ 58 4.7 Wind Load Analysis Uncertainty .................................................................. 64 Chapter 5: Recommended Guidelines Part II: Analytical Determination of Wind Loads ...................................................................................................................... 66 5.0 General ............................................................................................................ 66 5.1 Pipe Racks ....................................................................................................... 67 5.2 Open Frame Structures ................................................................................... 69 5.3 Partially Clad Structures ................................................................................. 83 vii 5.4 Pressure Vessels ............................................................................................. 85 5.5 Cooling Towers .............................................................................................. 94 5.6 Air Cooled Heat Exchanger (Air Coolers or Fin Fans) ................................ 95 Appendix 5A Alternate Method for Determining C and Load Combinations for f Open Frame Structures ........................................................................ 97 Appendix 5B High-Solidity Open Frame Structures .............................................. 106 Chapter 6: Examples ..................................................................................................... 110 6.0 Introduction ................................................................................................... 110 6.1 Pipe Rack and Pipe Bridge Example ........................................................... 111 6.2 Open Frame Examples ................................................................................. 123 6.3 Partially Clad Structure Example ................................................................ 137 6.4 Pressure Vessels Example ............................................................................ 140 6.5 Cooling Tower Example .............................................................................. 154 References ........................................................................................................................ 160 Index ................................................................................................................................. 167 viii CHAPTER 1 INTRODUCTION The focus of this report is on the procedures for determining the design wind loads for non-building structures in petrochemical and other industrial facilities. The report is structured around the following generic types of structures usually found in these facilities. Examples are also provided for some of these structures: a. Pipe support structures (pipe racks, pipe bridges) b. Open and partially clad frame structures c. Vessels (vertical, horizontal and spherical) d. Cooling towers e. Air coolers (air cooled heat exchangers, also known as fin fans) f. Tanks g. Steel stacks 1.1 Background The basis and procedures for determining design wind loads for enclosed structures and other conventional structures are well documented in the engineering literature. These design basis and procedures have been adopted by ASCE and prescribed in ASCE/SEI 7-051 (herein referred to as ASCE 7) and its predecessor documents. Other organizations have incorporated the major provisions of ASCE 7 into building codes. The International Building Code (IBC) states that wind loads should be calculated in accordance with ASCE 7, and the IBC has been adopted throughout the United States. ASCE 7 provides three methods for calculating design wind loads on the main wind force resisting system (MWFRS) and on components and cladding: 1. Simplified procedure 2. Analytical procedure 3. Wind tunnel procedure The simplified procedure (Method 1 in ASCE 7) was introduced to simplify the analysis of typical regular-shaped building structures. Its use is restricted to relatively rigid, low-rise, enclosed structures. The analytical procedure (Method 2 in ASCE 7) is permitted for structures of any height that do not have unusual geometric irregularities or unusual response characteristics. The wind tunnel procedure is required for complex structures that cannot be evaluated using Method 1 or 2. The Scope statement for ASCE 7 indicates that the standard provides minimum load requirements for the design of buildings and other structures that are subject to building codes. ASCE 7 also addresses enclosed structures, trussed towers, and simple cylinders commonly found in petrochemical facilities. However, to address important non-building structures in petrochemical and other industrial facilities, this report enhances ASCE 7 provisions for open frame structures, structures with 1 At the time of publication of this report, ASCE/SEI 7-10 had been released. 1