Erection of the TRC shells

Prior to the erection of the TRC shells, the four reinforced concrete columns were levelled, aligned and brought to the desired height. The columns were then joined to the concrete foundation with threaded bars anchored in the concrete foundation. In particular, the steel base plate welded to the column reinforcement at the bottom of the columns was bolted to the pad foundation (Fig. 3).

In order to transfer the large-format TRC shell from the production tent to the reinforced concrete columns, the movable roof of the production tent was opened and the shell was lifted off its formwork with a mobile crane (Fig. 14).

Fig. 13. Production of the TRC shell using shotcrete Fig. 14. Transferring a TRC shell from the production tent to the top of the RC column using a mobile crane

Fig. 12. Timber formwork for TRC shell in fabrication tent with movable working platform

A. Scholzen/R. Chudoba/J. Hegger · Thin-walled shell structures made of textile-reinforced concrete

The TRC shells were lifted with the crane at a single point only: the centre. From a structural point of view, the load during stripping corresponded to the final stress state with predominant membrane stresses. In this way no additional transportation anchors were needed for lifting. Instead, the connection of the TRC shell to the crane was realized using a thick-walled hollow steel pro-file, which was inserted into the embedded steel compo-nent and fixed by three steel bolts. The hollow steel profile about 1.20 m high automatically stabilized the shell dur-ing the strippdur-ing and erection process.

The embedded steel component was also used for the final positional adjustment of the shells and the struc-tural connection between shell and column. For this pur-pose, the four threaded bars protruding from the column were fed through the four guide tubes of the steel compo-nent during erection (Fig. 11). In the final state it was then possible to align the shells accurately using nuts which were placed under the steel component, so that a planned gap of 2 cm between the shells was attained (Fig. 15).

After final adjustment of the umbrellas, the joints were sealed at each column head and base, and the TRC umbrellas were bolted together with steel joints as ex-plained in section 2.1. Temporary scaffolding was neces-sary for erecting and coupling the TRC shells, which was dismantled after completion of the work.

4 Conclusions

This paper describes the structural design as well as the construction of a demonstration structure with a roof con-sisting of textile-reinforced concrete (TRC) shells. Based on the analysis of the loadbearing behaviour of the hypar shells, a reinforcement concept was developed reflecting the flow of the principal stresses within the shell structure.

Furthermore, a fabrication technique for the TRC shells as precast elements was developed together with the contrac-tor which met the high requirements regarding the posi-tional accuracy of the textile reinforcement layers over the filigree shell thickness. Besides the issues concerning the structural design and production of the shells as precast elements, it was also necessary to address the appropriate design of the connections. A solution for erecting and

aligning the shells has been proposed and realized as well.

Issues concerning the material behaviour and ultimate limit state assessment are presented in the companion pa-per [13].

These large shells demonstrate the application po-tential of this innovative, high-performance composite ma-terial. The present example of the TRC pavilion is intend-ed to inspire designers and architects to implement further new applications of textile-reinforced concrete in practice.

Acknowledgements

The authors wish to thank the German Research Founda-tion (DFG) for financial support within the collaborative research centre SFB 532 “Textile-reinforced concrete – de-velopment of a new technology” and DFG project CH 276/2-2.

References

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of 8th RILEM Int. Symposium, Barros, J. A. O. (ed.), Portu-gal, 19–21 Sept 2012.

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3. Soranakom, C., Mobasher, B.: Correlation of tensile and flex-ural responses of strain softening and strain hardening ce-ment composites. Cece-ment & Concrete Composites, 2008, 30, pp. 465–477.

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Non-linear analytical model of composites based on basalt textile reinforced mortar under uniaxial tension. Compos-ites: Part B, 2013, No. 55, pp. 518–527.

5. Hegger, J., Goralski, C., Kulas, C.: Schlanke Fußgänger-brücke aus Textilbeton – Sechsfeldrige FußgängerFußgänger-brücke mit einer Gesamtlänge von 97 m (A Pedestrian Bridge Made of Textile Reinforced Concrete). Beton- und Stahlbetonbau, 2011, 106, No. 2, pp. 64–71 (in German).

6. Hegger, J.; Kulas, C.; Raupach, M., Büttner, T.: Tragverhalten und Dauerhaftigkeit einer schlanken Textilbetonbrücke (Load-Bearing Behavior and Durability of a Slender Textile Reinforced Concrete Bridge). Beton- und Stahlbetonbau, 2011, 106, No. 2, pp. 72–80 (in German).

7. Kulas, C., Schneider, M., Will, N., Grebe, R.: Hinterlüftete Vorhangfassaden aus Textilbeton – Tragverhalten und Aus-führung (Ventilated façade structures made of textile rein-forced concrete – structural behavior and construction).

Bautechnik, 2011, 88, No. 5, pp. 271–280 (in German).

8. Horstmann, M., Hegger, J.: Sandwichfassaden aus Textilbe-ton – experimentelle Untersuchungen (Sandwich façades made of Textile Reinforced Concrete – Experimental investi-gations). Bautechnik, 2011, 88, No. 5, pp. 281–291 (in Ger-man).

9. Schladitz, F., Lorenz, E., Jesse, F., Curbach, M.: Verstärkung einer denkmalgeschützten Tonnenschale mit Textilbeton.

Beton- und Stahlbetonbau, 2009, 104, No. 7, pp. 432–437.

10. Ehlig, D., Schladitz, F., Frenzel, M., Curbach, M.: Textilbeton – Praxisprojekte im Überblick (Textile concrete – an overview of executed projects). Beton- und Stahlbetonbau, 2012, 107, No. 11, pp. 777–785 (in German).

Fig. 15. Loadbearing structure after final adjustment and coupling of the TRC shells (photo: bauko 2, RWTH Aachen University)

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Structural Concrete (2015), No. 1

11. Cassinello, P., Schlaich, M., Torroja, J. A.: Félix Candela. In memoriam (1910–1997). From thin concrete shells to the 21st century lightweight structures. Informes de la Construc-ctión, 2010, 62, No. 519, pp. 5–26.

12. Scholzen, A., Chudoba, R., Hegger, J.: Dünnwandiges Scha-lentragwerk aus Textilbeton: Entwurf, Bemessung und baupraktische Umsetzung. Beton- und Stahlbetonbau, 2012, 107, No. 11, pp. 767–776.

13. Scholzen, A., Chudoba, R., Hegger, J. (2015): Thin-walled shell structures made of textile-reinforced concrete – Part II:

Experimental characterization, ultimate limit state assess-ment and numerical simulation. Structural Concrete, 16:

115–124. doi: 10.1002/suco.201400046.

14. Schätzke, C., Schneider, H. N., Joachim, T., Feldmann, M., Pak, D., Geßler, A.; Hegger, J., Scholzen, A.: Doppelt gekrümmte Schalen und Gitterschalen aus Textilbeton. In:

Proc. of 6th Colloquium on Textile Reinforced Structures, Curbach, M., Ortlepp, R. (eds.), Berlin, 2011, pp. 315–328.

15. Schnabel, A., Grieß, T.: Production of non-crimp fabrics for composites. In: Non-crimp fabric composites: manufactur-ing, properties and applications, Lomov, S. V. (ed.), Wood-head Publishing Series in Composites Science and Engineer-ing, No. 35, Woodhead, Oxford, 2011.

Prof. Dr.-Ing. Josef Hegger RWTH Aachen University

Institute of Structural Concrete (IMB) Mies-van-der-Rohe-Str. 1

52074 Aachen Germany

[email protected] Dr.-Ing. Rostislav Chudoba RWTH Aachen University

Institute of Structural Concrete (IMB) Mies-van-der-Rohe-Str. 1

52074 Aachen Germany

[email protected] Dipl.-Ing. Alexander Scholzen RWTH Aachen University

Institute of Structural Concrete (IMB) Mies-van-der-Rohe-Str. 1

52074 Aachen Germany

[email protected]

The present paper describes a design approach for textile-rein-forced concrete (TRC) shells which reflects the interaction be-tween normal forces and bending moments based on the cross-sectional strength characteristics of the material determined experimentally. The influence of oblique loading on the composite strength of TRC elements with flexible reinforcement is included in a normalized interaction diagram for combined loading. As an example, the design approach is applied to the ultimate limit state assessment of a TRC shell in double curvature. Furthermore, the general applicability of the design approach is discussed in the light of the non-linear loadbearing behaviour of TRC. Due to its strain-hardening tensile response, stress redistributions within the shell result in loadbearing reserves. Details of the structural design and production solutions developed and applied during the realization of the TRC shell structure are described in the companion paper (Part I).

Keywords: cementitious composites, strain-hardening composites, textile-reinforced concrete, hypar shells, design of concrete shells, numerically based assessment, anisotropic damage model

1 Introduction

Assessment rules are needed for the design of textile-rein-forced concrete (TRC) shell structures in order to intro-duce this innovative composite material successfully into engineering practice. Engineering models that reflect the tensile, bending and shear strength of TRC elements have already been developed in recent years in analogy to those for conventional steel reinforced concrete structures.

Cross-sectional idealizations for design have been provid-ed for loadbearing TRC beam elements [1, 2, 3], steel rein-forced concrete structures retrofitted with TRC [4] and TRC sandwich panels [5].

Whereas steel-reinforced concrete cross-sections can be designed and dimensioned solely based on the material laws for steel and concrete, the direct design of TRC cross-sections using the component characteristics is not yet possible. The reason or this is the existence of a wide

vari-ety of textile fabrics [6] differing in material, type of weave and coating, which affect the stress-strain response of the composite quite significantly. Therefore, the cross-section-al strength characteristics of TRC have to be determined experimentally for each material combination considered.

For this purpose, several types of test setup have been de-veloped recently [3, 7, 8, 9].

The existing engineering models for TRC [1, 2, 3]

have been derived mostly for relevant uniaxial stress states, e.g. for TRC beam or truss elements. However, as documented in [10], by using simple linear finite element analyses, it is possible to exploit the high potential of this composite material, especially in thin shell structures.

However, engineering models and design tools for TRC shell structures are still lacking. In this paper, we propose a systematic approach to the ultimate limit state assess-ment of spatial TRC structures with complex loading sce-narios. Compared with the engineering models men-tioned, two additional important effects are included in the design approach: i) simultaneous action of normal forces and bending moments on a TRC shell cross-section and ii) a strength reduction due to the direction of loading not being aligned with the orientation of the textile fab-rics.

The paper starts with a review of the test setups used for deriving the strength characteristics of the TRC cross-section (cross-section 2.1). This is followed by a brief discussion of the test data interpretation (section 2.2). A simplified n-m interaction diagram for combined loading is intro-duced in section 3.1 and extended with the effect of oblique loading and butt joints between the fabrics in sections 3.2 and 3.3 respectively. The general assessment criterion is then given in section 3.4. The proposed automated assessment procedure accounting for the anisotropy of the TRC shell exposed to general loading conditions is described in section 3.5. An example of the application of the assessment procedure is given in sec-tion 4 for a roof structure in double curvature, including the evaluation of the cross-sectional strength characteris-tics in section 4.1 and the evaluation of the utilization ra-tio in secra-tion 4.2. The non-linear loadbearing behaviour of TRC and the structural reserves available due to stress redistributions within the shell are studied numerically in section 4.3. The present paper extends and generalizes the concepts originally published in the German lan-guage [11].

Technical Paper

Thin-walled shell structures made of textile-reinforced concrete

Part II: Experimental characterization, ultimate limit