A. Enfedaque

Structural Cast-in-Place Application of Polyolefin Fiber–Reinforced Concrete in a Water Pipeline Supporting Elements

AbstractResearch has shown that polyolefin-based macrofibers can meet the requirements of the standards to consider their postcracking contribution in the structural design of fiber-reinforced conc...

Assessment of the Shear Strength of Steel Fibre-Reinforced Concrete

Steel fibres when added to concrete, form what has been termed steel fiber-reinforced concrete (SFRC). The merger of these two materials boasts an improved post-cracking strength maintaining a high durability. Such features enable the use of SFRC in structural applications thanks to the appearance in recent times of standards and recommendations that assess its structural capacity based on flexural tests. However, the shear behaviour of a structural material is of key importance and up to now there are few studies dealing with this issue. In order to widen the knowledge in this area this contribution presents the experimental results of push-off shear tests performed in SFRC. The samples employed were double-notched ones and they were subjected to compressive forces in the tip of both notches creating pure shear stresses in the ligament. The influence of the fibre dosage was analysed by manufacturing two self-compacting concretes with 26 and 70 kg/m3 of fibre. Moreover, the influence of the fibre length was studied by using 35 and 50 mm-long fibres. Furthermore, the shear behaviour was also connected with the fracture behaviour of the same specimens shown in previous studies of the same authors.

Application of trilinear softening functions based on a cohesive crack approach to the simulation of the fracture behaviour of fibre reinforced cementitious materials.

The relevance of fibre reinforced cementitious materials (FRC) has increased due to the appearance of regulations that establish the requirements needed to take into account the contribution of the fibres in the structural design. However, in order to exploit the properties of such materials it is a key aspect being able to simulate their behaviour under fracture conditions. Considering a cohesive crack approach, several authors have studied the suitability of using several softening functions. However, none of these functions can be directly applied to FRC. The present contribution analyses the suitability of multilinear softening functions in order to obtain simulation results of fracture tests of a wide variety of FRC. The implementation of multilinear softening functions has been successfully performed by means of a material user subroutine in a commercial finite element code obtaining accurate results in a wide variety of FRC. Such softening functions were capable of simulating a ductile unloading behaviour as well as a rapid unloading followed by a reloading and afterwards a slow unloading. Moreover, the implementation performed has been proven as versatile, robust and efficient from a numerical point of view.

How to predict the orientation factor of non-rigid macro-synthetic fibre reinforced concrete

Polyolefin fibre reinforced concrete can met the requirements set in the standards that enable to consider the residual strengths in structural design. Such residual load-bearing capacity of fibre reinforced concrete is assessed by flexural tensile tests in which the presence of fibres can bridge the crack formed and provide strengths that are directly related with the number of fibres and their positioning in the fracture surface. Therefore, the orientation and distribution of the fibres is decisive in the mechanical behaviour of fibre-reinforced concrete and this can be estimated by means of the orientation factor. Several classical models have been extensively used for the case of rigid steel fibres. The increasing interest in structural synthetic fibres that can bend demands new considerations in this matter. A probabilistic model that considers the previous research with stereographical assumptions has been performed allowing the use of fibres that can bend. This study has developed significant tools for design with the aim of predicting such number of fibres crossing a vertical surface using fibre reinforced concrete with steel and polyolefin fibres. The model has been verified with experimental data and represents with accuracy the existence of boundaries, the type of concrete and compaction methods used to cast the moulds.