Textile Reinforced Concrete (TRC) materials have been addressed several times at the ACI conventions in the past 14 years. This area has been led by several RILEM Committees, fib, and ACI Committee 549. The first TRC committee was formed in July 2002, the RILEM TC 201-TRC (Textile Reinforced Concrete). The work of this committee was followed by Technical Committee 232-TDT addressing Test methods and design of textile reinforced concrete, developing recommendations of test methods and design of the composites. ACI has had a very strong presence in the international development of these materials. Various research groups have developed a wealth of recent information pertaining the methodologies, properties, and areas of applications for fabric reinforced cement-based materials. The theoretical framework will address aspects of multi-scale modeling, analytical tools to predict and design components for tensile, flexural, and shear loading of TRC composite systems. these sessions would be of interest to researchers, structural engineers and concrete repair professionals.
(1) New test methods for characterization and specification of early age and mechanical properties of textile reinforced concrete and FRCM;
(2) Procedures for measurement of material properties and residual strength parameters. Development of tools for structural analysis and design;
(3) Development, analysis, design, manufacturing, and applications of masonry repair materials with FRCM;
(4) Case studies of now and innovative structural systems from TRC and FRCM.
Shear Strengthening of Reinforced Concrete T-beams Using Carbon Reinforced Concrete
Presented By: Sarah Bergmann
Affiliation: RWTH Aachen University
Description: According to current regulations, a large number of existing structures show deficits in their shear capacity, which is often limited by the existing shear reinforcement. As the replacement of these structures is not always possible or favorable, effective strengthening methods and an accurate evaluation of their effectiveness are becoming more important.
The application of known strengthening methods such as additional steel reinforcement in slots, external prestressing, glued steel as well as CFRP strips, can be useful under certain boundary conditions. In addition to these methods, a strengthening with carbon reinforced concrete (CRC) can be a suitable alternative.
Tests on rectangular beams and T-beams, strengthened with AR-glass or carbon reinforced concrete layers show significant increases in their shear capacity despite low layer thicknesses and thus prove the potential of this innovative strengthening method.
Current approaches for the calculation of the shear capacity of strengthened components show deficits regarding suitability, accuracy and validity in practice-relevant applications.
Further research is necessary to identify major factors influencing the load-bearing behavior and shear capacity of reinforced concrete structures strengthened with CRC. This basic understanding is needed to develop a reliable and economical calculation model that can be used in an appropriate and practicable way to assess the effectiveness of a strengthening measure with CRC.
For this reason, extensive tests were carried out on reinforced T-beams in static four-point bending tests. A compact and a slender cross-section with low ratio of shear reinforcement were considered. For both cross-sections there were two reference tests as well as two tests each for five different CRC layer configurations. For the slender cross-section, two more tests were carried out with a shotcrete layer without carbon reinforcement.
Reinforced Concrete Columns Confined with FRCM: Experimental Performances, Analytical and Numerical Modeling
Presented By: Luciano Ombres
Affiliation: University of Calabria
Description: Fabric Reinforced Cementitious Matrix (FRCM) composites have the potential to improve the structural performances of concrete columns. As demonstrated by experimental investigations available in the technical literature, in fact, the FRCM confinement gives evidence of a remarkable increase of both strength and ductility of the existing concrete columns.
Many parameters, both geometrical and mechanical, affect the performances of FRCM confined reinforced concrete columns: among those the fabric and matrix type, the confinement ratio (i.e. the number of FRCM layers), the FRCM configuration, the concrete strength, the shape of the section and the load eccentricity. The variability of these parameters and the wide variety of FRCM systems available on the market, make difficult the development of general design models. Some available design models, such as those proposed in Code provisions (ACI 549, fib, Italian Code, etc.,) in some cases are not able to well predict the structural response of FRCM confined reinforced concrete columns. At the same time, numerical models are, often, not reliable and complex from a design point of view. Accurate and detailed analyses are, then, needed to overcome these difficulties, improve the knowledge of the structural behavior of FRCM confined concrete columns and allow to define reliable design models.
In the paper, the behavior of FRCM confined concrete columns is analyzed both experimentally and theoretically. An experimental investigation was conducted on FRCM confined reinforced concrete columns with square cross section (10 columns, 800 mm height with 150x150 mm cross section). Parameters investigated were the number of confining FRCM layers, the type of fabric (PBO and steel), the type of mortar (cement-based and lime-based), the eccentricity values of the compression load, the internal steel reinforcement.
Design Formula for FRCM Strengthened Masonry Elements Under Compression and Shear Load
Presented By: Maria Aiello
Affiliation: University of Salento
Description: The increasing interest in the field of conservation of existing masonry structures resulted in the development of new retrofitting technologies in the recent past. One of the most promising is the use of Fabric Reinforced Cementitious Mortar (FRCM), which consists of an open-grid within an inorganic matrix. The effectiveness of the FRCM-application is well-demonstrated in literature by means of experimental investigation regarding different structural members, among the others, columns and shear wall. In addition, FRCMs are commonly recognized as a durable strengthening solution since the grid is generally non-metallic (high-resistance corrosion) and, at the same time, the matrix is chemically compatible with masonry substrates.
Estimation of the Shear Strength of RC Members with Externally Bonded, Fully Wrapped FRCM Composites
Presented By: Tommaso D’Antino
Affiliation: Department of Architecture, Built Environment, and
Description: The application of externally bonded (EB) fabric reinforced cementitious matrix (FRCM) composites represents a viable solution to increase the shear strength of existing reinforced concrete (RC) members. Depending on the geometry and type of RC member, FRCM can be U-wrapped or fully wrapped around the member cross-section. Although the fully wrapped configuration is often not applicable for RC beams, it is particularly useful and easy to apply in the case of RC columns. However, models to estimate the shear strength of RC members with fully wrapped FRCM composites are currently quite limited. This study proposes an analytical model to estimate the shear strength provided by FRCM composites fully wrapped around RC cross-sections. The model is based on the truss analogy adopted by numerous design guidelines for the case of EB fiber reinforced polymer (FRP) strengthening. The proposed model accounts for the peculiar bond behavior observed in FRCM composites, which may differ significantly from that observed with FRP composites. The model accuracy is assessed by comparing analytical and experimental results of RC beams fully wrapped with PBO FRCM composite.
Structural Behavior of Thin-walled Shells Made of Textile Reinforced Concrete: Review of Existing Modeling Approaches and Needs for Further Development
Presented By: Michael El Kadi
Description: The development of cementitious composites reinforced with non-metallic textile fabrics resulted in several applications realized during the last decade, showing the potential of the material. Besides planar, regular structural elements, applied in cladding, pavement systems also geometrically non-uniform elements have been realized e.g. at ETH Zürich, TU Dresden, VUB Brussels, RWTH Aachen. Moreover, an economic utilization of high-performance reinforcement fabrics in large structural elements raised the need to vary the reinforcement layout through the geometry. The non-trivial geometry in combination with a non-uniform reinforcement layout poses several challenging questions on the design rules that are not covered by current codes. Realistic analysis of structural behavior using specialized modeling approaches is required that is able to account for specific aspects of material- and structural behavior. The paper will describe the salient aspects of the structural behavior of TRC shells and will review the methods applied to address these aspects in the modeling strategies and in experimental characterization.
An Overview of The Tensile and Bond Behavior of Fabric Reinforced Cementitious Matrix (FRCM) Composites
Presented By: Gianmarco De Felice
Affiliation: Roma Tre University
Description: Fabric Reinforced Cementitious Matrix (FRCM) composites are an effective, compatible and cost-efficient solution for repairing and strengthening existing structures. Recent research studies provided fundamental information on their tensile and bond properties and important industrial developments made many systems available for applications in the field. At the same time, a guideline for the design of structural retrofitting is in the process of being published by the ACI 549 Committee. A Round Robin Test was organized by RILEM TC 250-CSM on 28 FRCM composites with basalt, carbon, glass, PBO, aramid and steel fabrics, with different matrixes comprising cement or lime mortars, to collect a wide experimental dataset, contribute to existing knowledge and define test protocols. This paper provides an overview of the fundamental properties of a wide range of FRCM systems, based on the laboratory outcomes, and investigate the repeatability of test results. The intrinsic brittleness of the matrix in traction and the occurrence of several failure modes in both, tensile and shear bond tests, caused a large scatter of results, even when the tests were carried out in the same laboratory. Additionally, due to the sensitivity to manufacturing process, curing conditions, and experimental procedures (gripping method, measuring techniques) non-negligible differences were also found from laboratory to laboratory. Observance of standardized procedures is therefore necessary to improve the repeatability of test results and the confidence level associated to FRCM mechanical parameters, whose variability should be carefully taken into account in the design.