Mijo Nikolic

University of Split - Faculty of Civil Engineering Architecture and Geodesy

This article presents a novel two-dimensional quadrilateral solid finite element model, enhanced by incompatible modes and embedded strong discontinuity for simulation of localized failure in quasi-brittle heterogeneous multi-phase materials. The focus of interest lies in the development of discontinuities and cracks induced by both tensile and com...

This research presents a novel approach to modeling fracture propagation using a discrete lattice element model with embedded strong discontinuities. The focus is on enhancing the linear elastic response within the model followed by propagation of fractures until total failure. To achieve this, a generalized beam lattice element with an embedded st...

In this work, we propose Bayesian parameter estimation of a nonlinear mechanics based model describing the behaviour of mortar subjected to double shear test with externally bonded carbon fibre reinforced polymer (CFRP) plates. With the Bayesian approach, it is possible to identify mechanical material parameters of different phases of the mortar me...

A novel, fully coupled hydro-mechanical model for the failure analysis of partially saturated porous media is presented. Failure mechanisms pertain to propagating discontinuities, i.e. tensile cracks and shear bands influenced by matric suction or capillary pressure, that arises in the partially water saturated conditions. In order to simulate prop...

In this paper, we present a novel discrete lattice numerical model for modelling reinforcement in concrete structures. Concrete behaviour is represented here by Voronoi cells and Timoshenko beams as cohesive links between them. Reinforcement bars are explicitly implemented as separate beam elements, while the connection between the concrete and rei...

Consolidation tests were performed on reconstituted marl samples under saturated and unsaturated conditions in the geomechanical laboratory at the Faculty of Civil Engineering, Architecture and Geodesy (FCEAG). Reconstituted marl samples were used to simulate the behaviour of marl residual soil as a final product of weathering. The experimental res...

A damage softening model is implemented into a discrete lattice framework with embedded strong discontinuities for the discontinuous representation of fracture. Such a model fits heterogeneous framework and allows capturing the complex fracture mechanisms in quasi-brittle materials under various quasi-static and dynamic loading conditions. Finite e...

The weathering of marls from Dalmatia (Croatia) is approached from the aspect of unsaturated conditions and suction through the first findings of a new scientific project dealing with experimental and numerical investigations of mechanisms in unsaturated geomaterials. This is done by connecting the reliable previous own research results obtained on...

Microbiologically induced calcite precipitation (MICP) following the ureases is a bio-geo-chemical soil improvement technique in which the microorganism facilitates to create an environment for the precipitation of carbonates among the grains. This results in binding the loose granular media and prevention against mechanical failure. However, the b...

Prediction of failure mechanisms in concrete is a fairly complex task due to heterogeneous concrete micro structure, localization process triggered by cracks, multiple crack interactions during their growth and coalescence, different dissipative mechanisms in fracture process zone prior to localized failure and in a localization zone during the fai...

Nasip izrađen od zrna dobivenih drobljenjem meke stijene može biti podložan dodanom slijeganju uzrokovanim raspucavanjem zrna unutar strukture nasipa. Ovo dodatno slijeganje nije uzrokovano promjenom stanja naprezanja unutar nasipa i ne može biti procijenjeno standardnim metodama proračuna na osnovi modula stišljivosti izmjerenog nakon zbijanja nas...

When the principal stress (stress 1) reaches the chosen damage threshold value (the ultimate stress) cracks start to appear and propagate. The crack opening is measured by stress 5

In this work we address the challenge pertinent to validating safety of large engineering structures, both in terms of integrity to failure under extreme conditions and durability within their environment. Of particular interest are industrial domains of excellence in France, such as energy-production (nuclear power plants, large offshore turbines)...

Video: Kalthoff's experiment and dynamic crack propagation

This paper presents the lattice element models, as a class of discrete models, in which the structural solid is represented as an assembly of one-dimensional elements. This idea allows one to provide robust models for propagation of discontinuities, multiple cracks interaction or cracks coalescence. Many procedures for computation of lattice elemen...

In this work we propose and compare the two models for crack propagation in dynamics. Both models are based on embedded strong discontinuities for localized cohesive type crack description and both provide the advantage to not to require tracking algorithms. The first one is based on discrete lattice approach, where the domain is discretized with V...

In this work we present the total energy balance in dynamically driven localized failure propagation. The full energy balance is investigated on the well known benchmark problem where pre-notched plate is subjected to edge impulsive load or projectile causing the dynamic crack propagation until failure, which is experimentally shown in [1]. The lo...

The presence of the pore fluid strongly influences the reponse of the soil subjected to external loading and in many cases increases the risk of final failure. In this paper, we propose the use of a discrete beam lattice model with the aim to investigate the coupling effects of the solid and fluid phase on the response and failure mechanisms in the...

This chapter explores the role of material heterogeneity in the study of the mechanical behavior of concrete. It presents the meso-scale model, which is capable of providing different failure mechanisms leading to macro-scale representation in terms of multi-surface models for concrete, combining Drucker-Prager for compression stress and Rankine fo...

This paper presents the ‘discrete lattice model’, or, simply, the ‘lattice model’, developed for rock failure modeling. The main difficulties in numerical modeling, namely, those related to complex crack initiations and multiple crack propagations, their coalescence under the influence of natural disorder, and heterogeneities, are overcome using th...

The numerical methods have their origin in the early 1960s and even at that time it was noted that numerical methods can be successfully applied in various engineering and scientific fields, including the rock mechanics. Moreover, the rapid development of computers was a necessary background for solving computationally more demanding problems and t...

This chapter presents a discrete approach for modelling failure of heterogeneous rock material with discrete crack propagation and internal fluid flow through the saturated porous medium, where the coupling conditions between the solid and fluid phase obey the Biot’s porous media theory. Discrete cracks and localized failure mechanisms are provided...

also available at: http://www.sciencedirect.com/science/article/pii/S004578251500328X

In this work, we present a discrete beam lattice model capable of simulating localized failure in a heterogeneous fluid-saturated poro-plastic solid. Coupling conditions between the solid and fluid phase are governed by the Biot’s porous media theory, enhanced with the fluid flow through cracks. The basis for development of discrete 2D plane strain...

The results of experimental research program on ninety intact rock cylindrical test specimens are presented. The main goal is to examine the effect of typical specimens shape deviations (i.e. 'micro' deviations from flatness, parallelism of ends and specimen axis perpendicularity) on uniaxial compressive strength (UCS) for the limestone and similar...

Cette thèse aborde le problème de la rupture localisée dans les roches, qui caractérise un grand nombre d'applications dans le domaine du génie civil, tels que la rupture du barrage, effondrement des fondations, la stabilité des excavations ou les tunnels, les glissements de terrain et les éboulements. Le risque de rupture localisée devrait être mi...

In this work we present a full 3D model capable of representing cracks propagating through rock mass until complete localized failure. The model is based upon the discrete lattice of Timoshenko beams that can capture failure modes by using the embedded strong discontinuities. The model can also capture the pre-existing cracks and induced rock mass...

In this work, we present a discrete beam lattice model with embedded discontinuities capable of simulating rock failure as a result of propagating cracks through rock mass. The developed model is a two-dimensional (plane strain) microscale representation of rocks as a two-phase heterogeneous material. Phase I is chosen for intact rock part, while p...