Search

There is no unified method for deriving the tensile properties of fiber-reinforced ultra-high-performance cementitious composites (UHPCC). This study compares the most common material tests based on a large series of laboratory tests performed on a self-developed UHPCC mixture. The cementitious matrix, with a compressive strength of over 150 MPa and a matrix tensile strength of 8–10 MPa, was reinforced with 2% by volume of 15 mm long and 0.2 mm diameter straight high-strength steel microfibers. Over 100 uniaxial tensile tests were performed on three test configurations using cylindrical cores drilled out from larger prismatic specimens in three perpendicular directions. In addition to uniaxial tests, flexural tests on prismatic elements and flexural tests on thin plates were conducted, and the tensile properties were derived through digital image correlation (DIC) measurements and inverse analysis. Furthermore, splitting tensile tests on cylindrical specimens were employed to ascertain the tensile properties of the matrix. The outcomes of the diverse laboratory tests are presented and discussed in detail. The relationships between crack width and deflection in the context of flexural tests were developed and presented. In conjunction with compression tests and modulus of elasticity tests, the constitutive law is presented for the investigated materials. [ABSTRACT FROM AUTHOR]

The probabilistic evaluation of the capacity and response of structural systems is often done by probabilistic simulation. This approach relies on a considerable number of deterministic analyses to obtain an accurate estimation of the desired statistical characteristics. However, the need of performing a large number of analyses hinders the application of probabilistic simulation in practice, especially when the deterministic calculation of the structural response is computationally expensive in itself (e.g. nonlinear finite element analysis). To increase the appeal of probabilistic simulation, the number of analyses should be very small (i.e. ten or less). This study shows how different sampling techniques can be adopted to select a very small sample subset of analyses to be run, and how they can yield accurate results in estimating the shear capacity of prestressed reinforced concrete beams. Based on the results of the study, the Fractile Based Sampling (FBS) method emerges as a more promising sampling strategy than other sampling techniques, like Latin Hypercube Sampling (LHS). For the same small number of samples, the results show that FBS is preferable over LHS and other sampling techniques for capturing both the general distribution of the response and the tails of the distribution, which shows its usefulness in assessing probability of failure and reliability. [ABSTRACT FROM AUTHOR]

The use of textile reinforced concrete (TRC) as a shear strengthening solution for reinforced concrete (RC) structures is a viable and effective strategy. The low tensile strength of the cementitious matrix used to produce TRC, however, can strongly limit the performance achievable by such material. Using fiber/textile reinforced concrete (F/TRC), that is, TRC where short‐dispersed fibers were admixed to the cementitious matrix, has proven to overcome such limitations. An experimental campaign, aimed at assessing the influence of the fiber‐reinforced cementitious matrix, the number of layers, and their anchoring, was performed at the structural laboratory of Carinthia University of Applied Sciences. F/TRC strengthening configurations were tested on real‐scale T‐beams without internal transversal reinforcement. The results highlight the contribution of the cementitious matrix and hint at the possibility of simply summing its contribution to the one of the textile fabrics, while appropriate end‐anchorage seems to improve the performance of both elements. [ABSTRACT FROM AUTHOR]

The demand of effective and low-invasive methods for strengthening existing concrete structures is continuously increasing due to the ageing infrastructure. High performance materials can beneficially be applied to provide sustainable and robust strengthening solutions. The present article presents some exemplarily selected methods and innovative approaches for subsequent strengthening of existing RC structures. Main results of experimental investigations are summarized and future research topics identified.

The use of textile-reinforced concrete (TRC) in retrofit applications has proven to be an effective and viable solution. Many parameters, however, can affect the outcome, strongly inhibiting its potential. An experimental campaign was performed to assess the efficiency of TRC in strengthening reinforced concrete (RC) beams against bending with different varying parameters such as cementitious materials, number of textile layers, mechanical anchorages, and addition of short dispersed steel fibers. Results show how each parameter affects both the capacity increase and the failure mode, pointing out the beneficial effect of introducing both anchorage systems and short dispersed steel fibers. [ABSTRACT FROM AUTHOR]

Strengthening methods for shear‐deficient bridges were developed and tested in cooperation with the HILTI Corporation and SIKA Austria. In order to identify the strengthening effect in shear, a number of 12 T‐shaped RC‐beams with a length of 5.38 m were designed. In the experimental campaign two different types of strengthening systems were applied and subjected to shear loading until failure. The successful use of a modern digital image correlation system provided the basis for an in‐depth analysis of failure mode and crack pattern as well as shear degradation at each load stage. Finally, the applicability of existing shear design models with consideration of the strengthening elements analogously to cast‐in shear reinforcement was evaluated. [ABSTRACT FROM AUTHOR]