Scholarly article on topic 'Joint Composed of Various Section'

Joint Composed of Various Section Academic research paper on "Civil engineering"

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Procedia Engineering
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Keywords
{T-joints / "experimental models" / "circular or rectangular hollow sections" / "vertical deformation and horizontal deformation"}

Abstract of research paper on Civil engineering, author of scientific article — V.Kvočák, P. Beke, R. Vargová

Abstract The article presented focuses on the comparison of the measurement results obtained in laboratory experiments on joints composed of rectangular hollow sections, circular hollow sections and rolled open cross sections. Special attention is paid to T-joints that consist of the chord member of a single rectangular section and brace members of different kinds of cross section. The evaluation procedure monitors the resistances and deformations of such joints.

Academic research paper on topic "Joint Composed of Various Section"

ELSEVIER

"Institute of Structural Engineering, Civil Engineering Faculty of Technical University in Kosice Vysokoskolska 4, Kosice 04200, Slovakia

Abstract

The article presented focuses on the comparison of the measurement results obtained in laboratory experiments on joints composed of rectangular hollow sections, circular hollow sections and rolled open cross sections. Special attention is paid to T-joints that consist of the chord member of a single rectangular section and brace members of different kinds of cross section. The evaluation procedure monitors the resistances and deformations of such joints.

© 2012 Published by Elsevier Ltd. Selection and review under responsibility of University of Zilina, FCE, Slovakia.

Keywords: T-joints; experimental models; circular or rectangular hollow sections; vertical deformation and horizontal deformation;

1. Introduction

The gradual increase in the production range of hollow sections has resulted in their more common application in various areas and types of construction. This type of section has a number of applications in the construction industry, especially in structures where aesthetic appeal is important [1]. From the point of view of a structural designer, the application of hollow section joints presents relatively effective utilisation of the material. The distribution of the material and its mass in hollow section joints carries several advantages for various kinds of load. Their application is one of the best design solutions with regard both to buckling in members under compression and to lateral-torsional buckling in members loaded in bending. As far as strain is concerned, joints present the most exposed areas in structures composed of such types of section. Joints composed of rectangular hollow sections have recently received close attention [2],[3],[4]. Our experimental research programme concerns with the hollow-section joints combined with other kinds of section.

The article presents the results of the experimental programme that has been carried out at the Faculty of Civil Engineering of the Technical University in Kosice. Attention is paid to the joints composed of rectangular

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Procedía Engineering 40 (2012) 44 - 49

Engineering

Procedía

www.elsevier.com/locate/procedia

Steel Structures and Bridges 2012

Joint composed of various section

V.Kvocaka, P. Bekea* and R. Vargova3

* Tel.: +421-55-602 4243; fax: +421-55-633 7435

E-mail address: palo.beke@gmail.com

1877-7058 © 2012 Published by Elsevier Ltd. doi:10.1016/j.proeng.2012.07.053

and circular hollow sections, and the HEA open sections. These are all T-joints where the continuous chord member is made of a rectangular hollow section in each type of specimen. The brace members vary in section in terms of type and dimensions; as such, the authors of the article are planning to extend their research and supplement the results gradually by using some other combinations and types of sections in the future [5], [6], [7]. In future authors would like to deal with fire resistance of observed joint. Nowadays a collaboration is prepared with Institute of Architectural Engineering focused on this problematic [8].

2. Preparation of the experiment and performed laboratory measurements

A lot of factors that influence the stiffness of the joint need to be taken into account in the design. These include its geometry, the material used, stress application, welding etc. As regards the geometry of the joint, three different types of joint were compared. In the first type of joint, both the chord and brace members were composed of rectangular hollow sections. In the second type of joint, the chord member was composed of a rectangular hollow section as in the first case; however, the brace member was made of a circular hollow section. In the third type, the brace member was composed of an open HEA-type rolled section while the chord member remained the same as in the other two types.

Another variable that can characterize the joint is a p-parameter. It is the ratio of the mean diameter or width of the brace members to that of the chord. Our aim was to cover as wide a range of p -parameters as possible. To this end, the constant section of RHS 140x140x4mm was selected as the chord. Rectangular hollow sections of RHS 60x60x3, RHS 100x100x3 and RHS 140x140x4mm were used as the brace members in the first type of section, circular tubes of CHS 60x3 mm, CHS 100x3 mm and CHS 140x3 mm in the second type of joint, and, in the third open type of joint, HEA 100, HEA 120 and HEA 140 mm were used. The p-parameter for all types of sections ranged from 0.42 to 1.00. The above parameters made it possible to create a total of nine experimental types of joint (three joints consisting of circular sections, three joints consisting of square sections, and finally, three joints with open brace members). For each test type/set of joints there were subsets of three identical test specimens. Geometry of test specimens is shown in the figure 1.

RHS 140x4

RHS 140x4

RHS 140x4

□ RHS 60x3

RHS 140x4

OCHS 60x4

QCHS 100x4

^HEA 100 ~1~HEA120 | HEA 140

Fig. 1. Geometry of test speciments

All the models were made of steel S235 and a specimen of each model was taken to analyse its material characteristics. The yield strength in all specimens did not exceed the one declared by the steel manufacturer and it varied between 290 and 320MPa.

To simulate the real behaviour of the joint in a lattice structure, the chord member was assumed to act in horizontal compression, while the brace members were compressed in a vertical direction. Horizontal compression was actuated by means of an additional frame and pneumatic press. The numerical value of horizontal load remained constant during the whole loading period. Each specimen type was tested at three horizontal force levels: 68kN, 115kN and 192kN. Vertical load imposed on the specimens by the main hydraulic press was gradually increased until the total failure of the specimen. With respect to the complexity of the task, the length of the brace member was designed so as to prevent buckling of the member [5].

Measurement points on the individual specimens were then selected. Strain gauges were used to measure stress in the specimens and inductive sensors to determine horizontal and vertical deformations. During the strain-gauge measurements attention was focused on the chord member as, based on the calculation model, the joints under investigation collapsed due to the failure of the chord member in particular. Stresses were examined both in the horizontal and vertical walls of the chord and the strain gauges were attached in both longitudinal and transverse directions. Deformation was measured mainly in the chord members, specifically in the upper horizontal and vertical walls of the chord member section.

3. Obtained results

The types of joints selected were observed for both stress and deformation. In the following section of the article, attention will be directed to the deformation of the joints. The following sections provide an exact view of the real behaviour of the individual types of joint. The figures presented compare both vertical and horizontal experimentally measured deformations of the joints.

3.1. Comparison of deformations in the joints consisting of the identical type of the brace member

The joints with the identical type of the brace member are compared, see fig. 2,3,4. First, when there is a linear deformation, the joint is in the elastic range. Later, as the load is increased, the joint deviates from this linear proportionality and the deformation goes through the elasto-plastic and eventually into its plastic range of action. Of all the types of brace members, the most resistant certainly seem to be those with b0=b1 0=1). From the deformation point of view, the joints with a width of 60 mm are the least suitable. These exhibited excessive deformations even under minimal load.

R HS 60x3 RHS 100x3 R HS 140x3

0 50 100 150 200 250 300 vertical force in the brace member [kN]

22,5 20 17,5 15 12,5 10 7,5 5 2,5 0

RHS 60x3 RHS 100x3 R HS 140x3

0 50 100 150 200 250 300 vertical force in the brace member [kN]

Fig. 2. Comparison of the experimentally measured horizontal and vertical deformations in the joints composed of the brace members with rectangular hollow sections

CHS 60x3 CHS 100x3 CHS 140x3

0 50 100 150 200 250 300 vertical force in the brace member [kN]

100 90 80 70 60 50 40 30 20 10 0

C HS 60x3 CHS 100x3 C HS 140x3

WWVAjftA^

0 50 100 150 200 250 300 vertical force in the brace member [kN]

Fig. 3. Comparison of the experimentally measured horizontal and vertical deformations in the joints composed of the brace members with circular hollow sections

5 4,5 4 3,5 3 2,5 2 1,5 1

HEA 100 HEA 120 HEA140

0 50 100 150 200 250 300 vertical force in the brace member [kN]

HEA 100 HEA 120 HEA 140

0 50 100 150 200 250 300 vertical force in the brace member [kN]

Fig.4. Comparison of the experimentally measured horizontal and vertical deformations in the joints composed of the brace members with open HEA-sections

3.2. Comparison of deformations in the joints with the same widths of chord and brace members

The stiffness of the joint does not depend only on its dimensions but also on the type of the brace member used. The comparisons are presented in the form of the following figures 5 to 7.

In the first type of joint (p=1), the stability of the chord web (wall) was crucial for the overall resistance of the joint. Figure 5 presents the distribution of values of vertical and horizontal deformation. Significant deformation of the vertical chord web (wall) occurred even under a relatively light vertical load. The joint collapsed completely with the gradual increase in load due to the buckling of the vertical web (wall) of the horizontal chord member. When the resistance of rectangular, circular and open sections was compared, the rectangular sections proved to be the stiffest.

As can be seen from the figure 6, the buckling effect of the chord web (wall) on the overall resistance of the joint can be observed also in the joints with p=0.714. The overall resistance of the joint was i nfluenced by the loss of stability of the vertical web (wall) although the difference between the vertical and horizontal deformation was less significant than in the first case. When comparing the types of brace member used, the rectangular section appeared to be the most resistant of all. However, the difference between the rectangular and open HEA-section was minimal regarding vertical and horizontal deformation.

In the third type of joint (figure 7) with the most slender brace members, the overall resistance of the joint was to a great extent affected by the stiffness of the horizontal chord web (wall). The difference between the horizontal and vertical deformation in this type of joint is the biggest and the vertical deformation the greatest. The influence of the type of the brace member used on the overall resistance of such joints is virtually negligible. Due to the limited possibilities of the HEA rolling programme, only circular and rectangular hollow sections were compared. For p= 0.714 the behaviour of open sections was identical to that of rectangular sections and, obviously, it does not change for the lower p-parameters.

HEA 140 R HS 140 CHS 140

0 50 100 150 200 250 300 vertical force in the brace member [kN]

HEA 140 R HS 140 CHS 140

0 50 100 150 200 250 300 vertical force in the brace member [kN]

Fig. 5. Horizontal and vertical deformation of the T-joint with p=1.00 depending on the type of brace member used

5 4,5 4 3,5 3 2,5 2

HEA 100 R HS 100 CHS 100

0 25 50 75 100

vertical force in the brace member [kN]

HEA 100 R HS 100 CHS 100

0 25 50 75 100

vertical force in the brace member [kN]

Fig.6. Horizontal and vertical deformation of the T-joint with p=0,714 depending on the type of brace member used

R HS 60 CHS 60

0 20 40 60 80 100

vertical force in the brace member [kN]

0 20 40 60 80 100

vertical force in the brace member [kN]

Fig. 7. Horizontal and vertical deformation of the T-joint with p=0.428 depending on the type of brace member used

4. Conclusion

The scientific research results and evaluations presented characterize the correlations regarding the global resistance of joints in lattice structures in the light of the latest scientific knowledge that should be responsibly taken into consideration in their reliable and cost-effective design. The article presented points to the significance and topicality of the issue of investigating the joints in lattice structures. The priority of the research was to acquire knowledge of the real behaviour of the joints and supplement it with more effective methods for the design of joints composed of rectangular and circular hollow sections, and open HEA-sections.

From the results obtained some patterns of behaviour of T-joints may be identified. With respect to the geometry and type of section, it can be concluded that the resistance of a joint with p=1.00 is greatly influenced by the type of brace member. This influence sharply diminishes with the decreasing value of a p-parameter. With very low p-parameters, the influence of the type of brace member becomes virtually negligible and unimportant.

The conclusions presented in this article represent only a part of a number of results obtained in the experiments. The authors would like to continue in the analysis of such joints, while the main emphasis should be placed on the verification of the obtained results using an appropriate finite model for the joints in question.

Acknowledgements

This paper was funded by project No. 1/0788/12: "Theoretical and Experimental Analysis of Stability and Strength of Composite Members in Compression and Bending" of the grant agency VEGA of the Ministry of Education of the Slovak Republic and the Slovak Academy of Science and by the project ITMS 26220120037 "The Support to the Centre of Excellent Integrated Research into Progressive Building Structures, Materials and Technologies".

References

[1] Kala, Z.; Karmazinova, M.; Melcher, J.; Puklicky, L.; Omishore, A. 2009. "Sensitivity analysis of steel-concrete structural members", In Proceedings of the 9th International Conference on Steel-Concrete Composite and Hybrid Structures „ASCCS 2009" held in Leeds, Research Publishing Services: Singapore, 2009. 305-310. ISBN 978-981-08-3068-7.

[2] Packer, J. A.; Wardenier, J.; Kurobabne, Y.; Dutta, D.; Yeomans. N. "Design Guide for Rectangular Hollow Section Joints under Predominantly Static Loading", Verlag TUV Rheiland, 1992.

[3] Freitas, A. M. S.; Mendes, F.C.; Freitas, M. S. R. 2008. "Finite Elements Analyses of Welded T-Joints", In Proceedings from 5th European Conference on Steel and Composite Structures, Eurosteel, 2008 Graz, 2008. 555 -560

[4] Tomko, M. - Demjan, I. - Al Ali, M.: The Elastic-Plastic and Strain-Stress Analysis of Laminated Lattice-Girder Welded Hinged Connection. In: Transactions of the Universities of Kosice. No. 4 (2010), p. 32-43. ISSN 1335-2334

[5] Beke, P.; 2009. "Analyza zvaranych stycnikov z pravouhlych dutych prierezov [Analysis of welded joint composed of rectangular hollow section] ", Dissertation work. Kosice, 2009. 135 p.

[6] Kvocak, V.; Beke, P. 2008 a. "Experimental analysis of "T"-joints created from various types of sections", In Selected Scientific Papers: Journal of Civil Engineering. 3(2). 51-60. ISSN 1336-9024.

[7] Kvocak, V.; Beke, P. 2008 b. "Experimental verification of welded hollow section joints", In Zeszyty naukowe Politechniki Rzeszowskiej : Budownictwo i inzynieria Srodowiska. vol. 256, no. 50 (2008). 185-192. ISSN 0209-2646.

[8] Lopusniak, M.: Evacuation modeling techniques In: Fire Engineering : the 3rd international scientific conference : proceedings :5th - 6th Oct. 2010,Technical univerzity in Zvolen. - Zvolen : Technicka univerzita, 2010 p.201-207. - ISBN 978-80-89241-38-5