Failure mechanism of FRC slabs on non-local ground

Abstract

The present work deals with the mechanical behavior of a large FRC slab bilaterally supported by a non-local soil. The slab is modelled as a ductile Kirchhoff plate laying on a two-parameter elastic foundation and transversally loaded by a uniform pressure applied on a circular area, thus making the problem axisymmetric. This layout covers a wide array of practical applications of fiber reinforced concrete in structural and civil engineering related to the assessment of the load carrying capacity of industrial floors, roads, airfield pavements and building foundations. The problem is governed by a fourth order linear ODE with variable coefficients, whose solution has been obtained in power series by using the Frobenius method. The analysis allows us to evaluate the influence of the size of the loaded area and the relative stiffness of the slab/subgrade system on the collapse mechanism and the corresponding load carrying capacity, as well as on the distributions of displacement, rotation, bending moments, shear force and contact pressure at the onset of collapse. Keywords Ultimate carrying capacity Á Johansen's failure criterion Á Collapse mechanics Á FRC slab Á Kirchhoff plate Á Two-parameter foundation Á Axisymmetric loading condition Á Frobenius method List of symbols a Amplitude of the loaded region b, c, d Yield loci within the plate at the onset of collapse D Flexural rigidity of the plate E Young Modulus f ctk,fl Characteristic flexural strength of plain concrete f ctk(0.05) Characteristic axial tensile strength (5 % fractile) of plain concrete f ck Characteristic compressive strength (cylinder) of plain concrete h Total slab thickness h 0 Effective depth of the cross section H 1 ð Þ 0 Hankel function of first kind of order zero I 0 Modified Bessel function of first kind of order zero J 0Bessel function of first kind of order zero k r Curvature tensor

Effects of nano-silica treatment on the flexural post cracking behaviour of polypropylene macro-synthetic fibre reinforced concrete

“…A possible limitation in the experimental evaluation of the FRC toughness and post cracking strength is the high scattering of the results of the bending test caused not only by the heterogeneity of the concrete matrix but also by the small specimen geometries and by random factors determining the number of fibres crossing the cracked section [38]. The former data on the enhanced flexural behaviour of a treated MSFRC here provided will contribute in future works for the assessment of accurate modelling of the mechanical response of more complex structures like frames and plates [7,8] made of treated MSFRC.…”

“…Two class of synthetic fibres are usually employed for FRC: micro-synthetic fibres (micron order diameters), which are used for contrasting micro cracking of cement composites resulting from plastic shrinkage [4], and macro-synthetic fibres (mm order diameters), which have comparable dimensions with steel fibres and can equally improve concrete toughness and tensile strength [5]. For their properties, the macro-synthetic fibres have increased their commercial attractiveness over the years, being used in many civil engineering applications such as concrete pavements (used for industrial floors, roads, harbour piers), tunnels shotcrete (fibre reinforced sprayed concrete) and precast industry [6][7][8][9][10][11]. Despite the increased use of macro-synthetic fibres, they also display some peculiar weakness mainly related to the low elastic modulus, if it is compared to that of steel fibres [12], high deformability in time (creep) [13,14] and poor adhesion to the cement matrix due to the chemical inertia of PP and polymeric materials in general [15].…”

Pullout modelling of viscoelastic synthetic fibres for cementitious composites

“…8(d) for treated fibres with L = 30 mm, there is a certain gap between predictions and experimental results near the end of the test. FRC structures near their limit state can be properly assessed, with particular reference to bent beams [28,29] and Kirchhoff plates [30,31,32,33,34]. dσ(τ )ψ(t − τ ) ds L (t z ).…”

Analytical Approach for Modelling the Pull-Out Mechanism of Recycled Synthetic Fibres in Fibre-Reinforced Concrete (FRC)

“…The random distribution of fibres within the matrix provides the composite with a uniform reinforcement with undeniable beneficial effects, also by reducing or even hindering cracks formation, eventually improving the long-term performance and the fracture toughness [8]. For this reason, fibres in concrete may be considered as an important provision against brittle failure modes [9,10] and undesired anti-dry-shrinkage cracking [11]. Focusing on the material constituting the fibres, polymers have turned out to represent a promising solution, for their attractive advantages over steel.…”