Web Crippling of Wide Deck Sections

Transcription

1 Missouri University of Science nd Technology Scholrs' Mine Interntionl Specilty Conference on Cold- Formed Steel Structures (1990) - 10th Interntionl Specilty Conference on Cold-Formed Steel Structures Oct 23rd Web Crippling of Wide Deck Sections Jiri Studnick Follow this nd dditionl works t: Prt of the Structurl Engineering Commons Recommended Cittion Studnick, Jiri, "Web Crippling of Wide Deck Sections" (1990). Interntionl Specilty Conference on Cold-Formed Steel Structures This Article - Conference proceedings is brought to you for free nd open ccess by Scholrs' Mine. It hs been ccepted for inclusion in Interntionl Specilty Conference on Cold-Formed Steel Structures by n uthorized dministrtor of Scholrs' Mine. This work is protected by U. S. Copyright Lw. Unuthorized use including reproduction for redistribution requires the permission of the copyright holder. For more informtion, plese contct scholrsmine@mst.edu.

2 Tenth Interntionl Specilty Conference on Cold-formed Steel Structures St. Louis, Missouri, U.S.A., October 23-24, 1990 WEB CRIPPLING OF WIDE DECK SECTIONS By Jiti Studnick, PhD ABSTRACT: This pper presents the results of n extensive experimentl investigtion of web crippling lods for Czechoslovki mde multiple web deck sections. One flnge loding nd two flnge loding conditions were tested for both end nd interior rections. Bsed on the test dt, it cn be concluded tht stisfctory conformity ws obtined with the Cndin Cold-Formed Steel Stndrd for interior support conditions. For end support conditions slightly modified formul from CAN3 - S136 - M84 is recommended. 1. INTRODUCTION Cold-formed steel multiple web deck sections re used frequently in building construction. Where these sections re supported by end or interior bering pltes, or re subjected to concentrted lod t some point in the spn, filure of the deck cn occur by web crippling. Bending stress cn be lso present, but for some combintions of loding nd deck profiles the effect of the bending stress is negligible nd my not contribute significntly to filure. Reserch reported by Behre (1) hs shown tht there is no interction between bending nd web crippling when M ~ Mul t/3 nd Hetrkul nd Yu (2), Wing nd Schuster(3 nd Rtliff( ) lso confirmed this opinion. The ultimte web crippling lod cpcity is function of number of prmeters, nmely, the web slenderness rtio H, the inside bend rdius rtio R, the bering length rtio N, the ngle of web inclintion ~ (Fig. 1) nd the yield strength of steel Fy ' Lod cpcity lso depends on the distnce between the bering edges of djcent opposite concentrted lods or rections. When this distnce m is greter thn 1.5 hw one flnge Professor of Steel Structures, Czech Technicl University Prgue, Czechoslovki 317

3 318 loding is considered to occur. Two flnge loding occurs when the cler distnce between bering edges is equl to or less thn 1.5 h. Finlly, substntil difference is between end nd interior r~ction lodings. Cndin (5) nd AISI(6) codes re identicl in definition of end nd interior rections nd stte tht "end loding or rection occurs when the distnce from the edge of bering to the end of member is equl to or less thn 1.5 hw. When the distnce is greter there is interior rection". Yu(7) specifictes the difference between end nd interior rection more clerly. According to Yu when uniform loding works on bem support res re lwys clssified s one flnge loding zones. The objective of this study ws to determine, by experimentl wy, the lod resistnce of multi-web deck sections subjected to end nd interior rection loding P, s shown in Fig. 2. An experimentl test progrm ws to provide experimentl dt so tht existing methods of computtion could be compred nd evluted. 2. TEST PROGRAM The test progrm ws designed to encompss the most importnt prmeter vritions tht influence the web crippling resistnce of multi-web deck sections subjected to end nd interior rection loding. Test specimens were obtined from Czechoslovk mnufcturer, VSZ Kosice. The two types of specimens re shown in Fig. 3. Spreding of the webs during loding ws, for some tests, prevented by trnsverse tie rods which were bolted to the bottom flnge of profiles, see Fig. 4. The specimens were simply supported t the ends nd the lod ws pplied t the centre, s shown in Fig. 2. Reltively lrge end bering pltes were used for these tests to ensure tht filure would occur t the interior lod position nd vice vers for end lod position. The distnce m from the edge of the interior bering plte to the interior edge of the exterior bering plte ws chnged to obtin the conditions for one flnge nd two flnge lodings. However, the min chngeble dimension ws the bering width n, see Fig. 1. For tests t end support n inclined steel bering plte ws used following the

4 319 ECCS Recommendtions(B). The deck specimens were tested in both positions Nnd R, see Fig. 4. The test lod Pt ws tken either s the lrgest lod the specimen ws ble to sustin (fter which sudden decrese in lod ws experienced), or s the lod which residul deformtion of 1.0 mm developed, whichever ws lesser. 3. TEST RESULTS 3.1 Interior support Test results for 40 specimens re given in Tble 1. The following comments my be mde regrding the results: (i) test lods re not substntilly different for the N nd R positions of deck (ii) test results re lmost linerly influenced by bering width n (iii) test lods for specimens with ties re greter thn without ties. 3.2 End support Test results for 76 specimens re given in Tble 2. The sme three comments s for the interior support results cn be mde nd further two cn be dded: (iv) influence of distnce m on test results is very smll (v) when distnce k is incresed, the test lod lso increses. But the influence is not very strong. 4. COMPARISON OF TEST LOADS AND COMPUTED LOADS The AISI Specifiction(6) nd the Cndin code(5) were used to compute the ultimte web crippling lod Pc,see Tble 3. Since the method of permissible stress is used in AISI Specifiction, multiplying ll equtions from cluse C 3.4 by sfety fctor 1.B5 ws necessry. As the Cndin stndrd is in limit stte terms, there no corrections were necessry except for the missing resistnce fctor fs. Terms in the AISI Specifiction were converted to SI units.

5 320 Dimensions from Fig. 3 nd mesured yield strength Fy 260 MP were used for computtion of Pc' 4.1 Interior support Only one flnge loding ws exmined for interior support tests. Comprison of test results Pt with ultimte computed web crippling lods Pc (using AISI Specifiction nd Cndin Stndrd) is shown in Tble 4 nd in Fig. 5 nd 6. The solid line in the figures represents perfect correltion (P t = Pc) ; the dshed lines re ~ 20% limits which re cceptble sctter limits for tests of this type, bsed on previous reserch. One cn see tht better conformity ws reched in Fig. 6 in which lmost ll results re within ~ 20% limits over full rnge of the bering lengths. However, the men vlue of Pt/Pc of with coefficient of vrition is somewht disturbing. A smll number of tests mkes it impossible to drw more firm conclusions. 4.2 End support 80th one nd two flnge lodings were used in these tests. Comprison of test results Pt with computed lod Pc shown tht the test results re in resonbly hrmony with predicted vlues of web crippling end support lod, ccording to both Americn nd Cndin code. However, incresing of distnce k over boundry vlue 1.5 hw did not increse the test lod in such wy to be comprtive with the computed lod for interior support. Using the test results, new slightly modified expression ws developed, following the Cndin Stndrd. P=lO t 2Fy(sin ~)(l-o.l~ )(1-0.lVR)(1-H/500)(1+K/15H) ( N) (1) Eq. 1 predicts the web crippling cpcity for end rection for both one nd two flnge loding, if K ~ 3H. The other limittions from CAN3 - S136 re still fully vlid. Computed lods ~ccording to Eq. 1 re given in Tble 5.

6 321 Comprison of eq. I with test dt in Tble 6 nd in Fig. 7 shows very good prediction of those expression. This is indicted by the vlues of the men (l.olb) nd coefficient of vrition (0.136) of Pt/Pc. 5. CONCLUSIONS Bsed on the comprisons of the results of 40 interior support nd 76 end support tests with different methods of computtion, the following conclusions were mde: (i) The Cndin Cold-Formed Steel Specifiction(5) predicted the web crippling cpcities resonbly well for interior support conditione (ii) The use of Eq. 1 resulted in better prediction of the web crippling cpcity for end support thn ny of the existing methods. Eq. 1 is eqully vlid for one flnge loding nd two flnge loding. (iii) Tests with end support did not confirm the Cndin nd AISI provision tht the incresing of the distnce from edge of the bering plte to the end of multi-web deck cn bring substntil incresing of web crippling cpcity.

7 322 APPENDIX - REFERENCES 1. Behre, R., Sheet Metl Pnels for Use in Building Construction Current Reserch Project in Sweden, Proc. of the Third Spec. Conference on Cold-Formed Steel Structures, Univ. of Missouri Roll, Nov , Hetrkul, N. nd Yu, Wei-Wen, Cold-Formed Steel I-Bems Subjected to Combined Bending nd Web Crippling, in Thin-Wlled Structures ed. by J. Rhodes nd A.C. Wlker, Constrdo Wing, B. A. nd Schuster, R. M., Web Crippling of Multi-Web Deck Sections Subjected to Interior One Flnge Loding, Proc.Eight Spec. Conference on Cold-Formed Steel Structures, St. Louis, Missouri, Nov , Rtliff, C.D., Interction of Concentrted Lods nd Bending in C-Shped Bems, Proc. of the Third Spec. Conference on Cold-Formed, Steel Structures, Univ. of Missouri-Roll, Nov , Cndin Stndrds Assocition, CAN3 - S136 - M84, Cold Formed Steel Structurl Members, Dec Toronto 6. Americn Iron nd Steel Institute, Specifiction for the Design of Cold-Formed Steel Structurl Members, 1986 ed., Wshington 7. Yu, W. W., Cold-formed steel design, Wiley Europen Recommendtions for Steel Construction: The Testing of Profiled Metl Sheets, Publ. No 20, ECCS Committee TC 7, 197B 9. Studnick, J., Web Crippling of Multi-Web Deck Section, Thin Wlled Structures (in print)

8 323 APPENDIX - NOTATION hw k m Pc Pt R = r/t cler distnce between the flts of flnges mesured in the plne of the web distnce between end of deck nd end of bering plte distnce between edges of djcent opposite concentrted lods n bering leng~h r inside bend rdius t web thickness Fy tensile yield strength H hw/t web slenderness rtio K = k/t end distnce rtio Mult N = n/t ultimte bending moment bering length rtio computed lod test lod inside bend rdius rtio ngle between plne of web nd plne of bering surfce 45 0 ~ -S- ~ 90 0 F /230 resistnce fctor

9 324 Tble 1 Test results for interior support. Web crippling lod Pt in kn type of deck VSZ VSZ 12 position N I R N distnce m [mmj 100 N = I R upper vlue is vlid for deck without ties bottom vlue is vlid for deck with ties

10 325 Tble 2 Test results for end support. Web crippling lod P t in kn. type of deck VSZ VSZ posi tion N R N R distnce m [mm] distnce k (mm} N = distnce m [mm] distnce k [mm] N = where there re two vlues of lod, upper vlue is vlid fot deck without ties, bottom vlue is vlid for deck with ties

11 326 Tble 3 Web crippling lod p c in kn type of deck VSZ VSZ loding one flnge two flnge one flnge two flnge rection end inter e i e i e i N = upper number: AISI vlue bottom number: CAN vlue

12 327 Tble 4 Rtio Pt/P c for interior support type of deck VSZ VSZ loding one flnge pproch AISI CAN AISI CAN posi tion N R N R N R N R N = = = = = AISI men = coefficient of vrition CAN men = coefficient of vrition 0.106

13 328 Tble 5 Web crippling lod Pc in kn ccording to Eq. 1 type of deck VSZ VSZ loding rection both one flnge nd two flnge end rtio K N =

14 329 Tble 6 Rtio Pt/Pc for end support type of deck VSZ VSZ posi tion N R N R loding two flnge K N = loding one flnge K N = men coefficient of vrition 0.136

15 330 tttftf fttttt Fig. 1 Cross section of multiple web deck. H = %' R = t ' N = T, k n tn m n m H I I t I, ~ I I II 1:'2.0 ~, I I 0 0 JJIf/;JJJ 7TTTTTT7T 777TTTTTT" d.) (1.-\.) Fig. 2 Test setup for (i) end rection, (ii) interior rection

16 331 t 1'!{l.lt ('1206."1) f '2..' I (6~,1) Fig. 3 Tested wide deck sections. VSZ type (type )?o~itio\'l N I I ~ tf;, f t t t?ositiol\ R,- -, ~ fp f Fig. 4 End support test. Positions of profile. Tie rods t bolted to the flnge

17 332 "\.' " <t ~ D --" ,., ,,-"-- o II 8 D o 'IS f 1'200'2 o V sf 1210'2 Fig. 5 Test lod Pt vs. computed lod Pc' Interior support (Pc ccording to AISI Specifiction)

18 333 1.' > " D Q D Q " 8 n DD 119 IP ~ ~ ~o o Q D V Q 0 IIsr 1'2.102 c o 20 ItO 60 so 100 Fig. 6 Test lod Pt (Pc ccording to CAN code) vs. computed lod Pc. Interior support

19 334 '{.'2. ' i re.! g D o s - 3 II o.. 8 o 0 'lsi 1'lOO2. 'lsi 1'2102-1<" 120 K =100 K., <, ~O 'l.0 60 ~O Fig. 7 Test lod Pt vs. computed lod Pc. End support