The present paper describes a design approach for textile-reinforced concrete (TRC) 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 crosssections using the component characteristics is not yet possible. The reason or this is the existence of a wide variety 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-sectional strength characteristics of TRC have to be determined experimentally for each material combination considered. For this purpose, several types of test setup have been developed 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 assessment of spatial TRC structures with complex loading scenarios. Compared with the engineering models mentioned, 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 fabrics.The paper starts with a review of the test setups used for deriving the strength characteristics of the TRC crosssection (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 introduced 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 section 4 for a roof structure in double curvature, including the evaluation of the cross-sectional strength characteristics in section 4.1 and the evaluation of the utilization ratio in section 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 language [11].
Further, textile reinforced concrete has been successfully used in many cases as a retrofitting system for existing steel reinforced concrete structures, such as in the renovation of a heritage-listed barrel-shaped roof [9]. A detailed review of applications of textile-reinforced concrete recently carried out in Germany is given in [10].The present paper describes in detail the structural design and construction of a pavilion with an ambitious roof structure made of textile-reinforced concrete recently built on the campus of RWTH Aachen University. Once glazed on all sides, the pavilion will be used as a room for seminars and events (Fig. 1). The design by the Institute of Building Construction of RWTH Aachen University (bauko 2) uses umbrella-like shells as basic elements, each of which consists of an addition of four surfaces in double curvature, known as hyperbolic paraboloids (hypar surfaces).This shape refers to designs by the Spanish architect Félix Candela who, especially in the 1950s and 1960s, created many buildings in Mexico which are based on variations of such hypar shells [11] (Fig. 2).Such shell structures made of reinforced concrete have almost completely vanished from the current construction scene because of the corrosion problems of steel reinforced concrete and because of the labour-intensive fabrication of the complex in situ formwork. Here, TRC with non-corroding textile reinforcement provides new possibilities for the efficient realization of loadbearing systems with a small cross-sectional thickness. Owing to their low weight, such filigree loadbearing structures are particularly suitable for economical prefabricated construction
The present study addresses the influence of variations in material properties along the multi-filament yarn on the overall response in the tensile test. In Part I (Chudoba, Vořechovský and Konrad, 2006), we have described the applied model and studied the influence of scatter of material characteristics varying in the cross-section with no variations along the filaments. In particular, we analyzed the influence of varying cross-sectional area, filament length and delayed activation. Inclusion of these effects has lead to a better interpretation of the experimental data, especially with respect to the gradual stiffness activation, post-peak behavior and some form of size effect. In the present paper, the lengthrelated distributions of local stiffness and strength are included in terms of theoretical considerations and by applying the Monte Carlo type simulation of random fields. Such an approach allows us (1) to demonstrate the strong need for including length scale to random fluctuation of strength along the filaments and (2) to combine several sources of randomness in a single analysis so that their significance can be evaluated from the tensile test response.
Textile reinforced concrete (in short: TRC) is a relatively new building material. It is characterized by the possibility to produce very thin layers with a high tensile strength. Due to the use of flexible reinforcement, TRC is particularly suitable for shell building. In this paper we want to give a short overview about the development of TRC in Germany and the typical material properties. Further we want to describe realized projects in the fields of new shell buildings and of strengthening of reinforced concrete shell structures. The focus is here on manufacturing methods, and we want to demonstrate the potential of textile reinforced concrete for building constructions. We close with a short outlook.
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