Wald-Švarc 1

EXPERIMENTS WITH END PLATE JOINTS SUBJECT TO MOMENT AND NORMAL FORCE

FRANTIŠEK WALD, MAREK ŠVARC

Key words: Stress structures, Connection design, Moment – normal force interaction, Experimental observations, Portal frames The presented work describes the test designed to develop and to evaluate a European analytical prediction model of behaviour of end plate joints under combination of a bending moment and a normal force. In the laboratory of Czech Technical University ware carried out two sets of tests simulating the beam–to-column and beam-to-beam joints. The results are ready to be incorporated into the European databank of joint behaviour.

1. Introduction

The European practice improved the design of structural frames by introducing the knowledge of the frame imperfections and of the join behaviour [Eurocode 3, 1992]. The experimental knowledge supported by set of databanks [Kishi & Chen 1986] allows modelling of the working diagram by the engineering mechanical methods [Zoetemeijer, Summary 1983]. The prediction of joints made of the open section was improved significantly and reached the application level [Jaspart, 1991]. The mechanical model of joints using the component procedure [Zoetemeijer, Summary 1983] enable to predict the behaviour with asked accuracy [Wald & Steenhuis 1993]. The design of the multi-storey building frames including joints reached the practical application [Annex J, 1998].. The portal frames prediction is limited by the interaction of the normal force and the bending moment. The application of the component method [Zoetemeijer, 1974] to this problem is under the process [Jaspart et al., 1999]. The experimental work is the only way to enable the adequate FE simulation.

Experiments described in this paper ware carried out in laboratory of the Czech Technical University in Prague, Faculty of Civil Engineering, January – May 2000 [Švarc & Wald, 2000]. The contribution continues in experimental and theoretical work [Wald & Steenhuis 1993] prepared to improve and evaluate the European model of joint design started in 1990 [Šimek & Wald, 1991].

The experiments of the set up ware prepared to assure the quality of the prediction model, which is under preparation. The accuracy of the prediction is limited by number of tests [Bijlaard, 1982]. The new set of test related to the interaction of bending moment and normal force is under preparation in the Structural Laboratory of University of Coimbra, Portugal in spring 2001. These tests ware design under project COST C12 to be compulsory to ones finished at Czech Technical University in Prague.

Table 1 : The heights of the specimens

Beam - column type (SN) Beam-beam type (NN) SN 1000 SN 1500 NN 750 NN 1000 NN 1500

v [mm] 1032 1532 732 1032 1532

Wald-Švarc 2

2. Test Set-Up 2.1 Main Tasks

The main solved tasks were to evaluate a shape of the contact area and a position of the neutral axes. The behaviour of contact area was studied based on influence of M/N and the deformability of components in contact. The goal was to obtain the main design parameters: the joint working diagram based on the internal forces.

vtp

tp*

?

tp

tp*

?

v

p tp*

tp*

t

Figure 1 : The geometry of the specimen of the beam-beam type (NN)

and of the beam - column type (SN)

Figure 2 : The NN test set-up Figure 3 : The SN test set-up

Wald-Švarc 3

Figure 4 : The arrangement of the hinge by the loading cell

Figure 5 : The arrangement of hinge by the support

The test was streamed to observe the stiffness and the resistance under M/N, the influence of the support condition of the contact area, the change of the position of the normal force during the loading. The M-N interaction is reached by V shape of test specimen of two joints types, see Figure 1. Total five specimens ware tested (NN – three test, SN – two tests). The set up of type „beam-beam“ (marked below as NN) simulates a rigid support of compressed flange, see Figure 2. The test set up SN is type „beam-column“ (marked further as SN) and allows studying a free support of compressed flange of a connected beam, see Figure 3. The M-N ratio is changed by the specimen height, see Table 1. The test specimens ware loaded by hinged supports in the test frame, see Figures 4 and 5.

2.2 Measurements To reach the asked quality was measured the shape of the contact area, the total vertical

deformation, the local deformation of end plates, the bolt internal tensile forces. The carbon paper was used to obtain the print of the shape of the contact area after the

test. The induct transducers measured the vertical deformation. Deformation of the end plates was measured by inducting transducers at both sites of the flange in tension and at the middle between the flanges of the end plate. By the experiments NN ware the bolts equipped by the strain gages in the central hole drilled into the bolt. A strain gage was located on neutral axes of the bolt in the plane of the potential bending under the position under the bolt head, see Figure 6. The bolts ware preloaded by the hand smooth tightening to reach a torsion moment of 30 Nm.

Wald-Švarc 4

Figure 6 : Instrumentation of the plate of HH tests 2.3 Geometry

- The designed values are equipped by the real measured values to enable the FE simulation of the problem. The geometry of the beam-to-beam tests (NN tests) are summarized in Table 2 and 3 based on the Figure 8 and 9. The beam was designed as IPE 200 with bolts M 20 of material 10.9. No washer was placed under the bolt head as well as under the nut. - The values of the beam-to-column tests (SN tests) are introduced into the Table 4 and 5 based on the Figure 10 and 11. The beam was designed as IPE 180, the bolts M 12 of material. No washer was placed under the bolt head as well as the nut. The designed values are equipped by the real measured values to enable the FE simulation of the problem.

1e1

e2

w1

bp

hp

a tf

tw

e3

1

e1

e2

w1

bp

hp

a

tf

tw e3

tests NN tests SN

Figure 7 : The geometry of the end plate

Wald-Švarc 5

Table 2 : Geometry of the beam – beam tests, NN Symbols Measured [mm] Nominal [mm]

e eccentricity -------- 60 tp end plate thickness 10,05 10 tp* column head plate 16,06 16

V750 total length of set-up NN 750 731,9 732 V1000 total length of set-up NN 1000 1032,3 1032 V1500 total length of set-up NN 1500 1532,2 1532

Table 3 : Geometry of the end plates (NN 750, NN 1000, NN 1500) Symbols Measured [mm] Nominal [mm]

bp end plate width 140,05 140 hp end plate height 250,02 250 a1 beam vertical position 10,01 10 w1 bolts horizontal position 35,02 35 e1 the first bolt row vertical position 70,04 70 e2 the second bolt row vertical position 99,85 100 e3 the third bolt row vertical position 80,02 80 tf column flange mid thickness 8,52 8,5 tw column web mid thickness 5,64 5,6

aw.w the web weld effective height 4,03 4 aw.f the flange weld effective height 5,01 5

Table 4 : Geometry of beam - column tests, SN Symbols Measured [mm] Nominal [mm]

e eccentricity -------- 90 tp end plate thickness 8,02 8 tp* column head plate 16,00 16

V1000 total length of set-up SN 1000 1032,05 1032 V1500 total length of set-up SN 1500 1531,80 1532

Table 5 : Geometry of the end plates (SN 1000, SN 1500) Symbols Measured [mm] Nominal [mm]

bp end plate width 90,04 90 hp end plate height 250,10 250 a1 beam vertical position 60,01 60 w1 bolts horizontal position 19,98 20 e1 the first bolt row vertical position 25,04 25 e2 the second bolt row vertical position 79,85 80 e3 the third bolt row vertical position 90,03 90 tf column flange mid thickness 8,01 8 tw column web mid thickness 5,34 5,3

aw.w the web weld effective height 4,06 4 aw.f the flange weld effective height 5,02 5

Wald-Švarc 6

2.4 Material tests The standard coupon test [EN 10002] ware provided for the end plates and column

flanges, see Appendix. Three cylinder specimen, cut in the horizontal direction of the plate, was used for end plates of the N-N tests, marked as Ni, see Table 6 in Annex. At Table 7 are described the values of tree material tests of the end plates NS, cut in horizontal direction of the plate. The cylinder specimen ware marked as Si. For the material tests of the beam flange ware used tree flat specimens cut in direction of beam marked as Pi. see Table 8.

3. Results 3.1 Failure modes

The compressed part of the joint was designed to govern the resistance by all tests. For the NN test the failure occurred as failure of the flange of the beam in the compression. By the SN tests the failure occurred at the un-stiffened flange of the column in the compression part.

3.2 Shape of contact area

The shape of the contact area is one of the most important experimental observation by this types of joints, see Figures 12 and 13. By increasing of the normal force ratio is the area increasing. The engineering simplification placing the contact zone into the compressed flange area, see [Eurocode 3] is loosing its accuracy significantly.

test SN 1000 SN 1500

Figure 12 : Contact area of tests observed by a carbon paper of the SN tests

Wald-Švarc 7

a) b) c)

Figure 13 : Contact area of the tests; a) NN 750, b) NN 1000, c) NN 1500

3.3 Tests symmetry The measurement of the horizontal deformation shows good tests symmetry, see Figures 14 and 15. Close to the reached resistance ware the transducers removed to protect them against damage.

0

50

100

150

200

250

300

0 5 10 15 20 25 30 35 40 45Deformation [mm]

Forc

e [k

N]

NN 750 - P1NN 750 - P2NN 1000 - P1NN 1000 - P2NN 1500 - P1NN 1500 - P2

Figure 14 : Vertical deformation – force diagram of the NN tests

Wald-Švarc 8

0

10

20

30

40

50

60

70

0 10 20 30 40 50 60 70 80 90

Deformation [mm]

Forc

e [k

N]

SN 1000 - P1SN 1000 - P2SN 1500 - P1SN 1500 - P2

Figure 15 : Vertical deformation – force diagram of the SN tests 3.4 End plate deformation

The test SN shows a small deformation affected by less symmetry, see Figure 6. The tests

NN shows a very good symmetry and reasonable values, the transducers ware removed before reaching the collapse, see Figure 17.

0

50

100

150

200

250

300

-1 1 3 5 7 9 11Deformation [mm]

Forc

e [k

N]

NN750-I2NN750-I3NN1000-I2NN1000-I3NN1500-I2NN1500-I3

Figure 16 : End plate deformation of the NN tests

Wald-Švarc 9

0

10

20

30

40

50

60

70

-1 0 1 2 3 4 5

Deformation [mm]

Forc

e [k

N]

SN1000-I2SN1000-I3SN1500-I2SN1500-I3

Figure 17 : End plate deformation of the SN tests

3.5 Bolt Forces The results of bolt forces of N-N test are summarized in graph, see Figure 18.

0

50

100

150

200

250

300

-200 0 200 400 600 800 1000 1200 1400

Bolt force [kN]

Foer

ce [k

N]

NN750-è.5NN750-è.6NN1000-è.3NN1000-è.4NN1500-è.1NN1500-è.2

Figure 18 : Bolts forces of the NN tests

Wald-Švarc 10

0

10

20

30

40

50

60

70

0 1 2 3 4 5 6

Joint Rotation [o]

Mom

ent [

kNm

]

NN 750NN 1000NN 1500

0

10

20

30

40

50

60

70

0 50 100 150 200 250Normal Force [kN]

Mom

ent [

kNm

]

NN 750NN 1000NN 1500

Figure 19 : M-N-? curve of the NN test

Wald-Švarc 11

0

5

10

15

20

25

0 1 2 3 4 5 6Joint Rotation [o]

Mom

ent [

kNm

]

SN 1000SN 1500

0

5

10

15

20

25

0 10 20 30 40 50 60Normal Force [kN]

Mom

ent [

kNm

]

SN 1000SN 1500

Figure 20 : M-N-? curve of the SN test

Conclusions o The pure measured M-N-? curves calculated based on overall deformation against loading

forces are shown in Figures 19 for the NN tests and at Figure 20 for the SN test. No improvements due to the deformation of the beam-column bending are introduced at this level.

o The tests shows expected moving of the neutral axes during the loading, see Figures 12 and 13.

Wald-Švarc 12

o The results are ready to be incorporated into the European databank [Weynand at al., 1999].

o The reached collapse is adequate to the prediction model based on component method. o The comparison to the predicted methods is under preparation. Acknowledgements

This research has been supported by grant GAÈR 103/01/0708 of the Czech Grant Agency and by grant J01-98:210000001 of the Czech Ministry of Education. References

[Eurocode 3, 1992] ENV - 1993-1-1 (1992) Design of Steel Structures - General rules and

roles for buildings, European Prenorm, CEN, Brussels. [Annex J, 1998] ENV - 1993-1-1/A2 (1998) Design of Steel Structures - General rules and

roles for buildings, Annex J, Joints in Building frames, European Prenorm, CEN, Brussels.

[EN 10002] EN 10002-1 (1990) Metallic materials, Tensile testing. Part 1: Method of testing (at ambient temperature), CEN, Brussels.

[Bijlaard, 1982] Bijlaard F. S. K. (1982) Rekenregels voor het ontwerpen van kolomvloetplaten, rapport nummer BI-81-51, TNO Building and Conctruction research, Delft.

[Jaspart, at al., 1999] Jaspart J.P., Mac B., Cerfontaine F. (1999) Strength of joints subject to combined action of bending moments and axial forces, in Proceedings of the Conference Eurosteel ´99, Studnièka J., Wald F., Macháèek J. ed., Vol. 2, Prague, 26 - 29 May 1999, ÈVUT Praha, pp. 465 - 468, ISBN 80-01-01963-2.

[Jaspart, 1991] Jaspart J. P. (1991) Etude de la semi-rigidite des noeudes poutre-colone et son influence sur la resistance et la stabilite des ossatures en acier, MSMT, Liege.

[Kishi & Chen 1986] Kishi N., Chen W.F. (1986) Data Base of Steel Beam to Column Connections, Vol. I, Vol. II, CE-STR-86-26, Purdue University.

[Šimek & Wald, 1991] Šimek I., Wald F. (1991) Experimental evaluation of joints stiffness and resistance, research report, Project G1121, , p. 92, Prague.

[Švarc & Wald, 2000] Švarc M., Wald F. (2000) Experiments with end plate joints, research report, COST C12, CTU in Prague, p. 20.

[Wald & Steenhuis, 1993] Wald F., Steenhuis M. (1993) The Beam-to-Column Bolted Joint Stiffness according Eurocode 3, v Workshop 1992 - COST C1, in Proceedings of the State of the Art Strasbourg, pp. 503 - 516.

[Weynand at al., 1999] Weynand K., Huter M., Kirby P.A., Simoes da Silva, Cruiz P.J.S. (1999) A databank for tests on semi-rigid joints, in proseeding Control of the semi-rigid behaviour of civil engineering structural connections, Liege September 1998, pp. 217 - 229.

[Zoetemeijer, Proposal 1983] Zoetemeijer P., (1983) Proposal for Standardisation of Extended End Plate Connection based on Test results and Analysis, Rep. No. 6-83-23, Steven Laboratory, Delft.

[Zoetemeijer, Summary 1983] Zoetemeijer P. (1983) Summary of the Research on Bolted Beam-to-Column Connections (period 1978 - 1983), Rep. No. 6-85-M, Steven Laboratory, Delft.

[Zoetemeijer, 1974] Zoetemeijer P. (1974) A Design Method for the Tension Side of Statically Loaded Bolted Beam-to-Column Connections, Heron, No. 20 (1), Delft.

Wald-Švarc 13

APPENDIX MATRIAL TESTS RESULTS The standard coupon test results are summarized in Tables 6, 7 and 8 below.

Table 6 : Coupon test of the end plates, set of tests NN d0 d01 L0 S0 du du1 Lu Su FeH Fm ReH Rm A Z

mm mm mm mm2 mm mm mm mm2 kN kN Mpa MPa % % N1 5,90 6,00 31,00 27,81 3,20 3,20 39,90 8,04 9,80 12,10 352 435 28,71 71

N2 6,00 6,00 30,50 28,27 3,65 3,65 39,60 10,46 8,85 11,80 313 417 29,84 63 N3 6,00 6,00 30,50 28,27 3,40 3,40 41,40 9,08 9,50 12,00 336 424 35,74 68

x 334 426 31,4 67

R 39 18 - -

fk 321 420 - -

Table 7 : Coupon test of the end plates, set of tests SN d0 d01 L0 S0 du du1 Lu Su FeH Fm ReH Rm A Z

mm mm mm mm2 mm mm mm mm2 kN kN MPa MPa % % S1 6,00 6,00 30,10 28,27 3,55 3,55 40,50 9,90 8,45 12,05 299 426 34,55 65

S2 6,00 6,00 30,00 28,27 3,60 3,60 41,90 10,18 8,80 12,50 311 442 39,67 64 S3 6,00 6,00 30,10 28,27 3,30 3,30 42,70 8,55 9,10 12,80 322 453 41,86 70

x 311 440 38,7 66 R 23 27 - -

fk 303 432 - -

Table 8 : Coupon test of the beam flange, set of tests SN b0 h0 L0 S0 bu1 bu2 hu Lu Su FeH Fm ReH Rm A Z

mm mm mm mm2 mm mm mm mm mm2 kN kN MPa MPa % % S1 5,70 21,90 80,60 124,83 3,90 4,20 15,20 122,80 61,56 43,50 54,20 348 434 52,36 51 S2 5,60 21,80 80,20 122,08 4,10 4,10 15,10 124,00 61,91 42,00 52,00 344 426 54,61 49

S3 5,70 22,00 80,50 125,40 3,60 3,70 14,70 129,80 53,66 38,50 50,00 307 399 61,24 57

x 333 420 56,1 52 R 41 35 - -

fk 320 408 - - The relative elongation and contraction was calculated as A = [(Lu - L0) / L0]*100% , (1) where Lu is the coupon final length and L0 is the coupon initial length. The contraction was evaluated based on expression Z = [(Su - S0) / S0]*100% , (2) where Su is the coupon final width and S0 is the coupon initial width. Evaluation of the characteristic values of the working diagram was based on T distribution for small number of data as x = ? i (fui) / n , (3) R = max [fui] - min[fui] , (4) fk = x - ?t R(3) , (5) where n is number of tests, fui is the measured value of resistance, ?t is the probability factor for the T distribution.