Shear strengthening of concrete members with TRM jackets: Effect of shear span-to-depth ratio, material and amount of external reinforcement

An experimental work on reinforced concrete (RC) rectangular beams strengthened in shear with textile reinforced mortar (TRM) jackets is presented in this paper, with focus on the following investigated parameters: (a) the amount of external TRM reinforcement ratio, ρf, by means of using different number of textile layers and different types of textile fibre materials (carbon, glass, basalt); (b) the textile geometry, and (c) the shear span-to-depth ratio, a/d. In total, 22 tests were conducted on simply supported rectangular RC beams under (three-point bending) monotonic loading. The experimental results revealed that: (1) TRM is very effective when the failure is attributed to debonding of the TRM jacket from the concrete substrate; (2) the trend of effective strains for carbon, glass and basalt TRM jackets is descending for increasing values of the TRM reinforcement ratio, ρf, when failure is associated to debonding of the jacket; (3) the effect of textile geometry is significant only for low values of ρf, resulting in variances in the capacity enhancement and the failure modes, and (4) the shear span-to-depth ratio has practically no effect to the failure mode nor to the TRM jacket contribution to the total shear resistance of the RC beams

On the additivity of block designs

We show that symmetric block designs D=(P, B) can be embedded in a suitable commutative group G_D in such a way that the sum of the elements in each block is zero, whereas the only Steiner triple systems with this property are the point-line designs of PG(d,2) and AG(d,3). In both cases, the blocks can be characterized as the only k-subsets of P whose elements sum to zero. It follows that the group of automorphisms of any such design D is the group of automorphisms of G_ D that leave P invariant. In some special cases, the group G_D can be determined uniquely by the parameters of D. For instance, if D is a 2- (v,k,lambda ) symmetric design of prime order p not dividing k, then G_D is (essentially) isomorphic to (Z/pZ)^{{v-1}/2}, and the embedding of the design in the group can be described explicitly. Moreover, in this case, the blocks of B can be characterized also as the v intersections of P with v suitable hyperplanes of (Z/pZ)^{{v-1}/2}

Shear capacity of masonry walls externally strengthened using Flax-TRM composite systems: experimental tests and comparative assessment

A growing environmental awareness is gradually changing the entire economic system and consequently, the building materials sector is increasingly interested in innovative sustainable solutions. The use of plant fibres as reinforcement in inorganic composite systems, generally referred to as Textile Reinforced Mortar (TRM), represents an innovative alternative to the use of more traditional high-strength inorganic fibres, which reduces the environmental impact of the composite. However, there are several unsolved issues regarding the correct mechanical behaviour of such innovative systems. Various studies have been conducted to assess the fibre-to-mortar bond properties and to investigate the tensile behaviour of TRMs based on plant textiles, such as flax, hemp, coir, sisal, and jute. Moreover, there is still a lack of experimental evidence concerning the efficiency of the composite material once applied to structural elements. Therefore, this paper reports on an experimental study on the shear capacity of walls strengthened by two TRMs characterised by a different amount of textile reinforcement. The experimental results are discussed and compared with the results of theoretical models derived from formulations proposed by the standards in this field. This study shows that Flax-TRM reinforcement enhances the strength and ductility of a masonry assemblage, confirming the potential utility of such materials. Furthermore, it points out some limitations of this reinforcement technique and paves the way for future studies aimed at improving the efficiency of the entire system

Experimental study on the adhesion of basalt Textile Reinforced Mortars (TRM) to Clay Brick Masonry: The influence of textile density

Textile Reinforced Mortar (TRM) composite systems are gaining consensus within the scientific and technical communities as a viable and advantageous alternative to the most conventional Fibre-Reinforced Polymer (FRP) composites. Due to the good compatibility both in terms of stiffness and vapor permeability between the inorganic matrix and the substrate, the TRMs appear to be particularly well suited for strengthening masonry members and enhancing their capacity to withstand tensile and shear stresses, such as those induced by seismic shakings. This paper aims to investigate the mechanical response of a TRM system featuring an internal reinforcement made of basalt fiber textile. Therefore, the paper reports the results of an experimental campaign carried out by single-lap shear bond tests on masonry substrate reinforced by TRM strips. Three different kinds of TRM have been taken into account, each one characterized by a variable number of fabric plies. The results show that, in all cases, TRMs fail prematurely due to debonding between fabric and matrix. However, the aforementioned premature failure is the main concern emerging from these test results, and further work is requested in reformulating the matrix composition towards enhancing their tensile strength and, hence, restraining the occurrence of fabric-to-matrix debonding