Cisc Crane Guide
This is to discuss whether it is necessary to apply a dynamic impact factor to lifting load in crane tower structural analysis and design. During the weekend, I have conducted some studies on the Crane and Supporting Structural design and like to share the study findings with you. It should be advised that we are talking about Crane and Supporting Structures not only the Crane itself.
Design Approach There are two types of design approaches,. Static Design approach - Load Factor Method. General Design Approach - Allowable Stress Method 1.1 Static Approach, A safety factor should be applied for Crane and Bearing Structural Design when considering static loading. According to ASME specifications ASME30.20 and ASME BTH-1. Use a Safety Factor 2.0 for Category A lifters (Cranes), and – Category A, Lifting loading is defined;. Apply a Safety Factor 3.0 for Category B lifters (Cranes), -Category B, Lifting loading is undefined or lifting loading is severe.
No dynamic or impact factor is to be applied when applying static approach, 1.2 General Design Approach We are using this method in our crane tower structural analysis and design using structural analysis program SACS. If using general design approach, AISC allowable stress (generally 0.6Fy) should be applied for Crane and Bearing Structural Design. In addition, an impact or dynamic factor has to be applied for the lifting load. Different specifications specified different dynamic impact factor as shown in the following. Impact factor 1.2 to 1.5 (not more than 1.5) per specifications ASME30.20 and ASME BTH-1. Impact Factor 1.25 per ANSI MH27.1 & MH27.2,. Dynamic Factor 1.33 per API 2C for fixed pedestal/tower cranes, to be discussed in section 3.
Practically, onshore crane design shall apply impactor factor of 1.25 based on ANSI MH27.1 & MH27.2 specifications, see references attached 1, 2. Actually, the combination safety factor is almost the same as in load factor design method. Considering that the allowable stress of 0.6Fy, it implies that a safety factor is 1.67, when apply dynamic impact factor of 1.25 for lifting load, the overall safety factor for lifting load is, Foverall =1.25x1.67=2.08, It is relatively higher than 2.0 specified in Load Factor Design Method for structures of Category A lifters. That means both load factor method and allowable stress method are based on almost the same strength evaluation criteria for design of crane and bearing structures. 2 Theoretical Impact Theoretically, as a moving loading imposed on a structural system, additional dynamic loading impact shall be deployed to the structure due to the following reasons: Regardless of effects from wind, shocking (due to stopping or starting), moving with loading would induce dynamic impact which has to be considered in structural analysis and design. 2.1 Theoretical Impact If considering the vertical lifting speed only, the dynamic impact is to be counted following the equation, (2-1) Where, K with unit of lb/ft as Vertical Spring Rate or Structural System Stiffness; SWL with unit of lb as static working load or crane rated load; g gravity, 32.2ft/sec2; relative velocity of lifting, ft/sec.
2.2 Calculation per our Structure Based on the crane tower structural analysis, the calculated structural displacement is 3.333” or 0.2777’ at the 40’ tip under static load of 40 kips. Actually the term of is equivalent to the term of Thus we can calculate the dynamic impact factor in accordance with the lifting speed as shown in the shown in Table-1. Table-1, Example of Dynamic Impact Calculation per Current Tower Structure It is seen from the table that the dynamic factor is about 1.25, 1.33, 1.5 and 2.00 as lifting speed reaches 0.75 ft/sec, 1.0 ft/sec, 1.5 ft/sec and 3.0 ft/sec respectively for our tower structure. Above example is based on structural deflection of our crane tower with the boom at 135 degree in plane. In fact, the structural deflection is varying due to loading intensity, boom rotation and loading application distance from tower center in plane. Therefore, the theoretical dynamic impact is changing in one structural system in accordance with the actual loading intensity, lifting speed and boom position. Practically, to simplify analysis, a constant impact factor is always used for structural analysis and design as specified by related design specifications.
In general, the higher the lifting speed, the severe the dynamic impact and the stiffer the structure the higher the dynamic impact. When designing a crane supporting structure, a structural layout is developed and the structural stiffness is defined, therefore, the lifting speed is a critical factor concerning dynamic impact for lifting load.
As lifting speed is one of the main factors in dynamic impact evaluation, the specification requires that experienced operator should be employed to control the lifting speed. However, control of speed could not be guaranteed, specification further requires that a “Qualified Professional” should determine the dynamic factor to simplify the calculations. 3 Onshore VS. Offshore From Section 1 and 2, we can conclude that there is no significant difference from different specifications. The impact factor is in a range of 1.2 to 1.5 depending on the structural stiffness and lifting speed. Regardless if the specification is for offshore or onshore structure, the dynamic impact factor follows the same theory of structural dynamics. The difference between offshore and onshore structures is the movement of the crane supporting structural base.
- The attached is a very useful design guide. Yea, you have CISC and DG7 but I've found a lot of this crane column design is based on a lot of.
- Charter in 1942, the CISC functions as a nonprofit organization promoting the. The scope of this design guide includes crane-supporting steel structures.
Actually, the dynamic impact calculation for offshore structure is based on the same equation as that used for onshore structure. The only difference is the speed calculation counting crane base movement as shown in Equation 3-1.
CISC Centre for Steel. Crane-Supporting Steel Structures: Design Guide (Third. The scope of this design guide includes crane-supporting steel structures.
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(3-1) For onshore structures, the speed Vh in Equation 2-1 represents the lifting speed for cranes supported by a fixed structure. For offshore structures, on the other hand, the speed is summation of three directional speeds due to movement of supporting structural base as shown below. Assuming Vd and Vc to be zero, equation 3-1 returns to equation 2-1, the same as dynamic factor calculation for onshore structures. Therefore, applying API-2C factor 1.333 for fixed structure to onshore structures is reasonable. However, the factor of 1.333 is relatively conservative with 6% higher than the factor 1.25 specified in ANSI specification. I believe either applying dynamic impact factor 1.25 per ANSI or using factor 1.333 per API is reasonable. However, impact factor 1.25 specified in ANSI specification for onshore structures is strongly recommended for our crane tower structural analysis and design.
I am expecting technical discussions to determine the impact factor for moving load. Thanksa RE: Crane and supporting structural design (Structural).
From such use. All suggestions for improvement of this publication will receive full consideration for future printings.
CISC is located at 3760 14th Avenue, Suite 200 Markham, Ontario, L3R 3T7 and may also be contacted via one or more of the following: Telephone: 905-946-0864 Fax: 905-946-8574 Email: info@cisc-icca.ca Website: www.cisc-icca.ca Revisions This Edition of the Design Guide supersedes all previous versions posted on the CISC website: www.cisc-icca. Future revisions to this Design Guide will be posted on this website. Users are encouraged to visit this website periodically for updates. Vii PREFACE TO THE SECOND EDITION Since the fi rst printing of this design guide in January 2005, the author has received many useful and constructive comments along with questions, answers to which could generate more information for the designer of these structures. Additionally, changes to the National Building Code of Canada (NBCC) and refi nements to the companion load concept upon which load combinations are based have occurred. CSA Standard S16, Limit States Design of Steel Structures is being updated and new provisions that affect the design of these structures are being introduced. The second edition refl ects the signifi cant changes that are warranted due to the above information and now includes an index.
The fi rst two chapters contain an introduction that explains the intent of the publication (unchanged) and information on loads and load combinations. Important changes in this area are included, most notably in the refi nement of the load combinations, section 2.4.2. Chapter 3, Design for Repeated Loads, remains essentially unchanged, with a few clarifi cations added. Chapters 4, 5 and 6, Design and Construction Measures Checklist, Other Topics, and Rehabilitation and Upgrades have been updated to refl ect comments and additional information. References have been added and updated. Several comments and questions related to the fi gures and design examples have prompted revisions to some of the fi gures and the two design examples.
The intent of this publication remains to provide a reference for the practicing designer that refl ects Canadian and North American practice. The author wishes to thank all those who took the time to comment and provide suggestions.
Special thanks to the late David Ricker (reference 27) who took the time to constructively comment in depth, providing a number of suggestions which have been incorporated into this edition. Viii 1 CHAPTER 1 - INTRODUCTION This guide fi lls a long-standing need for technical information for the design and construction of crane-supporting steel structures that is compatible with Canadian codes and standards written in Limit States format. It is intended to be used in conjunction with the National Building Code of Canada, 2005 (NBCC 2005), and Canadian Standards Association (CSA) Standard S16-01, Limit States Design of Steel Structures (S16-01). Previous editions of these documents have not covered many loading and design issues of crane-supporting steel structures in suffi cient detail. While many references are available as given herein, they do not cover loads and load combinations for limit states design nor are they well correlated to the class of cranes being supported. Classes of cranes are defi ned in CSA Standard B167 or in specifi cations of the Crane Manufacturers Association of America (CMAA).
This guide provides information on how to apply the current Canadian Codes and Standards to aspects of design of crane-supporting structures such as loads, load combinations, repeated loads, notional loads, mono-symmetrical sections, analysis for torsion, stepped columns, and distortion-induced fatigue. The purpose of this design guide is twofold: To provide the owner and the designer with a practical set of guidelines, design aids, and references that can 1. Be applied when designing or assessing the condition of crane-supporting steel structures. To provide examples of design of key components of crane-supporting structures in accordance with: 2. (a) loads and load combinations that have proven to be reliable and are generally accepted by the industry, (b) the recommendations contained herein, including NBCC 2005 limit states load combinations, (c) the provisions of the latest edition of S16-01, and, (d) duty cycle analysis. The scope of this design guide includes crane-supporting steel structures regardless of the type of crane. The interaction of the crane and its supporting structure is addressed.
The design of the crane itself, including jib cranes, gantry cranes, ore bridges, and the like, is beyond the scope of this Guide and is covered by specifi cations such as those published by the CMAA. Design and construction of foundations is beyond the scope of this document but loads, load combinations, tolerances and defl ections should be in accordance with the recommendations contained herein. Frankenstein study guide answers. For additional information see Fisher (2004). In the use of this guide, light-duty overhead cranes are defi ned as CMAA Classes A and B and in some cases, C.
See Table 3.1. Design for fatigue is often not required for Classes A and B but is not excluded from consideration.
The symbols and notations of S16-01 are followed unless otherwise noted. Welding symbols are generally in accordance with CSA W59-03. The recommendations of this guide may not cover all design measures. It is the responsibility of the designer of the crane-supporting structure to consider such measures.
Comments for future editions are welcome. The author wishes to acknowledge the help and advice of Hatch, for corporate support and individual assistance of colleagues too numerous to mention individually, all those who have offered suggestions, and special thanks to Gary Hodgson, Mike Gilmor and Laurie Kennedy for their encouragement and contributions. 2 CHAPTER 2 - LOADS 2.1 General Because crane loads dominate the design of many structural elements in crane-supporting structures, this guide specifi es and expands the loads and combinations that must be considered over those given in the NBCC 2005. The crane loads are considered as separate loads from the other live loads due to use and occupancy and environmental effects such as rain, snow, wind, earthquakes, lateral loads due to pressure of soil and water, and temperature effects because they are independent from them. Of all building structures, fatigue considerations are most important for those supporting cranes. Be that as it may, designers generally design fi rst for the ultimate limit states of strength and stability that are likely to control and then check for the fatigue and serviceability limit states.
For the ultimate limit states, the factored resistance may allow yielding over portions of the cross section depending on the class of the cross-section as given in Clause 13 of S16-01. As given in Clause 26 of S16-01, the fatigue limit state is considered at the specifi ed load level – the load that is likely to be applied repeatedly. The fatigue resistance depends very much on the particular detail as Clause 26 shows.
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However, the detail can be modifi ed, relocated or even avoided such that fatigue does not control. Serviceability criteria such as defl ections are also satisfi ed at the specifi ed load level. Crane loads have many unique characteristics that lead to the following considerations: (a) An impact factor, applied to vertical wheel loads to account for the dynamic effects as the crane moves and for other effects such as snatching of the load from the fl oor and from braking of the hoist mechanism. (b) For single cranes, the improbability of some loads, some of short duration, of acting simultaneously is considered.
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(c) For multiple cranes in. 3.