Regine Ortlepp

Textile Reinforced Concrete for Flexural Strengthening of RC-Structures-Part 2: Application on a Concrete Shell

The first practical application of the innovative strengthening method using textile reinforced concrete was carried out in October/November 2006 in the retrofit of a reinforced-concrete roof shell structure at the University of Applied Sciences in Schweinfurt, Germany. Since textile-reinforced concrete had not yet been standardized as a construction material, a single “special-case” technical approval was sought from and granted by the appropriate authorities for this particular application of textile reinforced concrete. This strengthening method entailed the layer-by-layer application of three layers of fine-grained concrete and textile fabric comprising 800 tex carbon rovings onto a rough, sandblasted concrete surface. The resulting strengthening layer has a thickness of only 15 mm (0.6 in.) and extended the roof structure’s service life.

Application of stitch-bonded multi‐plies made by using the extended warp knitting process: reinforcements with symmetrical layer arrangement for concrete

With the development of the extended stitch‐bonding process, an important modification of the production process for stitch‐bonded fabrics was realized. Through the introduction of a lateral shift of the needle bar, the stitch‐bonding process is essentially being changed compared with the working method used before. This has made possible the manufacturing of optimally adjusted textile semi‐finished products for numerous applications in the field of composite material. One such application – the usage of stitch‐bonded fabrics as a textile reinforcement for concrete – is analyzed in this article. It was observed that promising possibilities for the use of the extended stitch‐bonding process result from overcoming the known restrictions during the production with conventional stitch‐bonding machines. A markedly improved quality of textile reinforcement is achieved through the new binding patterns and the free arrangement of the layers. The reinforcement shows a verifiable better bonding behavior than the conventional method. Therefore, it is guaranteed that there is no spalling on the concrete surface at service load, which is an important prerequisite for the practical use of textile‐reinforced concrete.

Column Strengthening with TRC: Influences of the Column Geometry onto the Confinement Effect

The increase of the load-carrying capacity of columns being reinforced with Textile Reinforced Concrete (TRC) is partly achieved by the additional concrete cover. But then it is also decisively caused by the confinement effect of the textile reinforcement. The confinement is thereby producing a three-axial state of stress within the concrete core of the column. The effectiveness of such a confinement is especially dependent on the geometry of the concrete column to be strengthened. At rectangular ones with sharp edges without ogees the TRC strengthening can only augment the load-carrying concrete share not create a confinement effect which can be achieved at the round counterparts. Within the study we tested columns with all possible cross-sections from square to circle with different transition radiuses. Thus the influence of the transition radius onto the local-bearing capacity of the reinforcing textile was recorded. Furthermore the impact of different fibre materials and reinforcement degrees of the TRC-strengthening layer has been examined. The first results show a considerable disproportionate increase of the confinement effect with rising transition radius, as well as a growth of the confinement effect with augmenting level of reinforcement in the TRC-strengthening layer.

Textile-Reinforced Concrete for Flexural Strengthening of RC-Structures—Part 1: Structural Behavior and Design Model

The use of technical textiles to reinforce concrete (i.e., textile reinforced concrete [TRC]) extends into entirely new areas of application. The thick concrete covers, as required for steel reinforced concrete, are no longer needed due to the corrosion resistance of textile materials. Slender structural members with thicknesses as small as 10 mm (appr. 4 in.) are possible. Additional characteristic features of textile reinforcement include two-dimensional planar characteristics, as well as ease of deformability and adaptability to complex and curved geometries. This can be exemplified by a pedestrian bridge built of TRC. Various geometric forms, such as slabs, beams, T-beams, shells, and columns can easily be strengthened using TRC. Dimensioning of elements and structures using TRC requires detailed knowledge of the load-bearing behavior of this composite material. Indeed, such behavior resembles that of steel reinforced concrete; however, this behavior is more heavily influenced by the bond between the textile reinforcement and the fine concrete, as well as the bond between filaments within the textile reinforcement. Minimal thicknesses also make it possible to strengthen existing concrete structures using TRC. Such strengthening increases both the ultimate load bearing capacity, as well as the serviceability, of the structure. Experimental results of strengthened slabs and beams, as well as a design model for flexural strengthening, is presented in this paper.

Strengthening of RC Structures with Textile Reinforced Concrete (TRC)

Strengthening by textile reinforced concrete noticeably increases both the ultimate load bearing capacity as well as the serviceability such as deflections, crack widths and crack spacing are reduced. This paper will give an overview of the ongoing research work with this new composite material Textile Reinforced Concrete (TRC).

Anchorage Length for Textile Reinforced Concrete

1 Abstract- The anchorage length needed for textile fabrics as reinforcement within a fine-grained concrete matrix was determined based upon specific filament yarn pull-out tests. The purpose of this research was to eliminate the possibility of failure due to fabric pull-out from the matrix in practical applications. Therefore, a new test set-up was developed, which offers the possibility for a quick and direct determination of the anchorage length. Several textile fabrics made of alkali resistant glass (AR-glass) fibres, as well as carbon fibres were therewith tested. Findings indicated that conventional AR-glass fabrics required large anchoring lengths, and, its another fact to consider, that carbon fibres have a substantially higher strength than AR-glass fibres and different bond behaviour. The research further showed that an additional application of a polymer suspension coating to textile fabrics greatly increased the reinforcements resistance to pull-out.