GUIDE FOR THE DESIGN OF CRANE-SUPPORTING STEEL STRUCTURES

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1 GUIDE FOR THE DESIGN OF CRANE-SUPPORTING STEEL STRUCTURES THIRD EDITION R.A. MACCRIMMON NIAGARA FALLS, ONTARIO

2 2.4. Fatigue The calculated fatigue stess ange at the detail unde consideation, to meet the equiements of Clause 26 of S6-4 and as descibed in Chapte 3 of this document, will be taken as that due to C. Note: Dead load is a steady state and does not contibute to the stess ange. Howeve, the dead load stess may cause the stess ange to be entiely in compession and theefoe favouable o wholly o patly in tension and theefoe unfavouable Ultimate Limit States of Stength and Stability In each of the following inequalities, fo load combinations with cane loads, the factoed esistance, R, and the effect of factoed loads such as 0.9D, ae expessed in consistent units of axial foce, shea foce o moment acting on the membe o element of concen. The most unfavouable combination govens. Case Pincipal Loads Companion Loads. R.4D 2. R (.25D o 0.9D) + (.5C +.0L).0S o 0.4W 3. R (.25D o 0.9D) + (.5L +.0C).0S o 0.4W 4. R (.25D o 0.9D) +.5S (.0C + 0.5L) 5. R (.25D o 0.9D) +.4W (.0C + 0.5L) See Note R (.25D o 0.9D) +.0C 7. R.0D +.0E.0C d + 0.5L S 8. R.0D + C whee C is any one of the cane load combinations C 2 to C 6 fom Table 2.2. Loads D, L, S, W and E ae loads defined in the National Building Code of Canada (NBCC) issued by the Canadian Commission on Building and Fie Codes with the exception that the load L is all the live loads excluding loads due to canes. Notes () though (9) of table B of the NBCC 205 shall apply to the factoed load combinations. Notes: ) The combinations above cove the whole steel stuctue. Fo design of the cane unway beams in an enclosed stuctue fo instance, S and W would not nomally apply. 2) Cane unway columns and occasionally cane unway beams suppot othe aeas with live loads. 3) The effects of factoed imposed defomation,.25t, lateal eath pessue,.5h, factoed pe-stess,.0p, shall be consideed whee they affect stuctual safety. 4) The eathquake load, E, includes eathquake-induced hoizontal eath pessues. 5) Cane wheel loads ae positioned fo the maximum effect on the element of the stuctue being consideed. 6) The basic NBCC load factos shown above ae in accodance with infomation available at the time of publication of this document. The designe should check fo updates. 7) Note that the NBCC equies that fo stoage aeas the companion load facto must be inceased to.0. 8) Side thust due to canes need not be combined with full wind load. 7

3 stess evesals, ae excluded fom these povisions and should be investigated fo fatigue in any case. Second, the equiements of Clause 26. that the membe and connection be designed, detailed, and fabicated to minimize stess concentations and abupt changes in coss section ae to be met. Only then, if the numbe of cycles is less 3 than the geate of two citeia, oc f s is no fatigue check equied. The detail categoy may detemine the limit. Fo example, fo detail categoy E, fom Table 0, the fatigue life constant, = MPa and, say, calculations give a fatigue stess ange, ƒ s = 20 MPa. Hence the second citeion yields a limit of cycles. Theefoe, the limit of cycles contols and if the detail is subject to fewe than cycles, no fatigue check is necessay. 3.3 Detailed Load-Induced Fatigue Assessment 3.3. Geneal Clause of S6-4 gives the design citeion fo load-induced fatigue as follows: whee F s ƒ s F s = fatigue esistance 3 nn F st nn F st and ʹ = fatigue life constants (see Clause ) n numbe of stess ange cycles at given detail fo each application of load N = numbe of applications of load F st = constant amplitude theshold stess ange (Clauses and ) f s = calculated stess ange at the detail due to passage of the fatigue load including stesses due to eccenticities Above the constant amplitude fatigue theshold stess ange, the fatigue esistance (in tems of stess ange) is consideed to vay invesely as the numbe of stess ange cycles to the /3 powe. Reaanging the expession fo the fatigue esistance, the numbe of cycles to failue is: 3 nn F s Accodingly the numbe of cycles to failue vaies invesely as the stess ange to the thid powe. Below the constant amplitude fatigue theshold stess ange, the numbe of cycles to failue vaies invesely as the stess ange to the fifth powe. The effect of low stess ange cycles will usually be small on cane-suppoting stuctues but should be investigated nonetheless. It equies the addition of a second tem to the equivalent stess ange (see Section 3.3.3) whee the value of m is 5 fo the elevant low stess ange cycles. As stated in Section 2.4, a dead load is a steady state and does not contibute to stess ange. Howeve, the dead load stess may cause the stess ange to be entiely in compession and theefoe favouable o wholly o patly in tension and theefoe unfavouable. In this egad, web membes of tusses subjected to live load compessive stesses may cycle in tension when the dead load stess is tensile. This condition may also apply to cantileve and continuous beams. On the othe hand, the compessive stesses due to dead load in columns may oveide the tensile stesses due to bending moments. Fo additional infomation on analysis of stess histoies whee complex stess vaiations ae involved, see Fishe, Kulak and Smith (997), and Kulak and Gondin (200). 9

4 3.3.2 Palmgen -Mine Rule The total o cumulative damage that esults fom fatigue loading, not applied at constant amplitude, by S6-4 must satisfy the Palmgen-Mine Rule: whee: nn N fi nn i i 0. = numbe of expected stess ange cycles at stess ange level i. N fi = numbe of cycles that would cause failue at stess ange i. In a typical example, the numbe of cycles at load level is and the numbe of cycles to cause failue at load level is The numbe of cycles at load level 2 is and the numbe of cycles to cause failue at load level 2 is The total effect o damage of the two diffeent stess anges is = 063. < 0. OK Equivalent Stess Range The Palmgen-Mine ule may also be expessed as an equivalent stess ange.! Dv 8 a Dv B m m e = i i whee: D v e = the equivalent stess ange a i = faction of any paticula potion of the stess ange to the total numbe of cycles ni = ni D v i = the stess ange level i. m = 3 fo stess anges at o above the constant amplitude theshold stess ange. Fo stess anges below the theshold, m = 5. Fo example, if the stess ange at level in the above example is 88 MPa and the stess ange at level 2 is 29 MPa, then the equivalent stess ange is < c m ^ h + c m ^ hf 200 MPa A calculation of the numbe of cycles to failue (see Section 3.3.) and whee gives cycles. Since the actual numbe of cycles is , the pecentage of life expended (damage) is /49 000) 00% = 64%. This is essentially the same esult as in (equivalent stess ange was ounded off). 0

5 Table 4. continued Stuctual Class of Sevice One Cane Only SA SB SC SD SE SF Desciption Thousands of Full Loading Cycles Lowe Limit N Not Defined 2. Side thust fom canes should be distibuted in popotion to the elative lateal stiffness of the stuctues suppoting the ails. 3. Stuctual analysis should account fo theedimensional effects such as distibution of caneinduced lateal loads between building bents. 4. Vetical deflection of unway beams unde specified cane loads, one cane only, not including impact, should not exceed the indicated atios of the span Hoizontal deflection of unway beams unde specified cane loads should not exceed the indicated atios of the span. See also Comment 4/5. 6. Building fame lateal deflection at unway beam level fom unfactoed cane loads o fom the unfactoed -in-0-y wind load should not exceed the specified factions of the height fom column base plate o 50 mm, whicheve is less Exceptions fo pendant-opeated canes ae noted: The lesse of /00 o 50 mm 7. Relative lateal deflection (change in gauge) of unway ails due to gavity loads should not exceed 25 mm. 8. Effect of tempeatues above +50 C and below -30 C should be investigated. 9. Ends of simply-suppoted ends of unway beams should be fee of estaint to otation in the plane of the web and fee fom pying action on hold down bolts. (f) 22

6 Table 4.2 continued Item Comment See Figue 3 Some degee of thee-dimensional analysis is equied to adequately assess loads in hoizontal bacing. Refe to Fishe (2004) and Giggs (976) fo additional infomation /5 Recommended deflection limits fo Items 4 and 5 ae consistent with the ecommendations of the CMAA. Deflections ae elastic beam deflections. Diffeential settlement of foundations can cause seious poblems and should be limited to 2 mm unless special measues ae incopoated. The industy pactice is to calculate deflections fo one cane, not including impact. - 7 Excessively flexible columns and oof faming membes can esult in undesiable changes in ail-to-ail distance, even unde cane-induced gavity loads that cause sway of the stuctue. These movements can ceate cane opeational poblems and unaccounted-fo lateal and tosional loads on the cane unway beams and thei suppots. Final unway alignment should be left until afte the full dead load of the oof is in place. 8 Fo applications whee the ambient tempeatue ange lies between +50 C and -30 C, stuctual steel meeting the equiements of CSA G40.2 gade 350W can be expected to pefom adequately. Fo sevice at elevated tempeatues, changes in popeties of the steel may waant adjustment of design paametes. While notch toughness at low tempeatues is often equied by bidge codes, this is not usually a equiement fo cane unway beams, one eason being the elatively small cost of eplacement compaed to a bidge beam. - 9 Limiting estaint to otation and pying action on bolts can often be accommodated by limiting deflections and by moving the hold-down bolts fom between the column flanges to outside as shown in Figues 4 and 8. The cap plate thickness should be limited o use of finge tight bolts is ecommended to minimize pying action on the bolts. Note that the eccenticity of vetical loads shown in Figue 8 may cause a state of tension in the column flanges. Fo design fo fatigue, lage anges of stess may have to be consideed. Knee bace stuts should not be used, in paticula fo class of sevice C, D, E and F Whee lateal estaint is not povided, the unway beams should be designed fo bending about both the stong and weak axes. See AISC (993), Rowswell and Packe (989), and Rowswell (987).The use of details that ae igid in out-of-plane diections should be avoided. S6-4 equies consideation of the effects of distotion-induced fatigue The web-to-flange weld can be subjected to tosional foces due to lateal loads applied at the top of the ail and ail-to-flange contact suface not cented ove the web beneath, fo instance. Thee is no diectly applicable fatigue categoy. Refe to AIST (2003) fo additional infomation Use of intemittent fillet welds on tension aeas of built-up unway beams is pohibited by CSA W59. Intemittent fillet welds have shown poo esistance to fatigue and ae not allowed on dynamically loaded stuctues by some authoities such as AIST (2003) and AWS (205). The use of these welds should be esticted to applications whee fatigue is not a consideation. - 29

7 Eection toleances of cane unway ails should be compatible with minimization of eccenticities on the suppoting stuctue and within toleances set by the cane manufactues. Allowable sweep of cane unway beams should be consistent with design assumptions fo ail eccenticity, ail clip adjustment toleances and ail alignment toleances. Unless the stuctue is suitably esistant to change in gauge of cane ails unde oof dead load, final alignment of the cane unway beams should be defeed until the full dead load of the oof is in place. Figue 24 shows the equiements of the CMAA. The ate of change should not be applied to a distance less than 6 metes. It is based on equiements fo satisfactoy cane pefomance. Othe toleances such as those shown in table 4. ae elated to fabication and eection toleances. Both citeia should apply. The fabication specification should account fo equied toleances which may be moe sevee than the individual standads pemit. In case of conflict with Clause of S6-4 and ecommendations contained elsewhee in this design guide, the moe stingent equiements should goven. Checking of eection toleances should be by independent suvey. Whee the specified toleances ae exceeded, the designe should be notified. Afte assessment, the designe should specify emedial measues as may be equied Standads fo Inspection Refe also to Sections 5.27 and Figue 25 shows commonly used standads fo welding and inspection of cane unway beams. See W59 fo moe infomation. Refeing to CSA Standad W59, Welding inspection oganizations and individual inspectos must be cetified to CSA Standads W78 and W78.2 espectively. Fo inspection of othe aspects of fabication and eection, no standad fo cetification exists. Inspectos should be completely familia with the equiements of the design dawings and poject specifications including all specified standads and codes, including equiements fo dynamically loaded stuctues as may be applicable. CSA Standad B67-96 specifies the minimum equiements fo inspection, testing, and maintenance of canes and includes suppoting stuctues. Section specifies that a Pofessional Enginee must cetify the suppoting stuctue. The use is advised to consult with the juisdiction having authoity egading adoption of this Standad, and whethe thee may be exemptions o additions Maintenance and Repai Cane-caying stuctues subjected to fatigue, in combination with: age, unintended use (often called abuse), inadequate design, impefections in mateials, substandad fabication, substandad eection methods, and building component movements, such as foundations, equie maintenance and epai. Repai pocedues should incopoate the ecommendations of an expeienced stuctue designe, o the epai can ceate effects that ae moe seious that the oiginal impefection. Refeing also to item 5.29, it is ecommended that peiodic inspection and maintenance be done and a checklist should be pepaed fo the maintenance pesonnel. Fishe (2004), Millman (99, 996) and Reemsnyde and Demo (978) povide additional infomation. 42

8 Calculate Dead Load Suppoted by the Plate Gide Section Aea, mm 2 # = kg/m # = kn/m Plate Gide # % of Apon Plate # Rail Misc. (allowance) kn/m Calculate the Unfactoed Bending Moment M x Due to Dead Load = # knm $ 8 = Calculate the Unfactoed Maximum Bending Moment M x Due to Live Loads with Impact = = 3 54 knm $ Calculate the Unfactoed Maximum Bending Moment M x Due to Live Loads without Impact = = 2853 KN.m Calculate the Unfactoed Maximum Bending Moment M y due to Live Loads (side thust) = * # = knm $ * Amplified due to eccenticity of loads due to side thust Calculate M fx with Impact M fx = ^25. # 634. h + ^5. # 354h = 556kNm $ (see pevious calculations) Calculate M fx without Impact M fx = (.25 X 63.4) + (.5 X 2853) = 4484 kn.m If the unloaded cane has been weighed (C DL ) knowing the lifted load (C LL ), the factoed vetical cane load would be.25c DL +.5C LL. Calculate M fy at Top M = = knm $ fy # Check bacing to compession flange by Clause Maximum factoed foce in top flange Factoed UDL due to 5% of this foce kN/m kn

9 Factoed bending moment due to this foce knm < knm 8 Does not goven, no need to combine with side thust. Calculate M fy at Bottom M fy = 5. # # 225. = 34. knm $ Check Tial Section fo Biaxial Bending, Top cone, Rail Side. Check fo live Loads, No Impact This is the Yielding Limit State (Stength) Check. M fx M fy. M + # 0 x My = = #. 0 OK Check fo Lateal-Tosional Buckling Limit State (Stability) is not equied because the section is lateally suppoted by the hoizontal beam. Check fo Bending Stength Top Cone, Back Side M M fy y # = 042. < 0. OK Check fo M fx and M fy in Bottom Flange, Live loads, no side thust = <.0 OK Check fo M fx and M fy in Bottom Flange, Live loads, no impact = = <.0 OK 59 Calculate Factoed Shea in the Vetical Diection, Impact included = b # # l ^ + + h = = 665 kn Check Shea Stength in the Vetical Diection = < 0. OK A check fo combined bending moment and shea is not equied because the section is not tansvesely stiffened. See S6-4, Clause

10 Check column action 2 A = ^2 # 232 # 25h + ^6 # 92h = mm 3 3 I ^ = #. mm h # = # = # = mm L = of the length of the stiffenes 4 3 = # 440 = 080 mm KL # = = 6 4 Using Table 4-4 of the CISC Handbook, the factoed esistance fo 350 MPa stiffenes is # = 4607kN > 665kN OK 000 Check Beaing (Clause 3.0) 25 Fit to Bea, Minimum welds to be povided Check one side Factoed load 665 =. kn 2 = mm Figue A24 Beaing of Beaing Stiffene Clause 28.5 states that at least 75% of the aea must be in contact. To guad against fillet welds suppoting the load, check fo = 55 mm in contact. The factoed beaing esistance, to clause kn > OK Design welds to web Factoed load pe weld kn/mm 2350 ( say) Fom Table 3-24, CISC Handbook, need 5 mm fo stength; use minimum = 8 mm. 3