Georgios A. Drosopoulos

University of Central Lancashire | UCLAN · Civil Engineering

Present study investigates the effect of the fibre volume ratios and the ply thicknesses on the fundamental frequencies and the frequency gaps of simply supported and symmetric angle-ply laminates. The elastic constants of the fibre reinforced composite are determined by using micromechanical relations. The laminate is defined as having three layer...

Usage of artificial intelligence methods and especially feedforward artificial neural networks which can be trained by the backpropagation method has a long history in mechanics. By using input-output examples experimentally generated or numerically calculated, direct and inverse problems in mechanics can be studied [1-4]. Complicated metamodels ca...

Nonlinear Mechanics for Composite Heterogeneous Structures applies both classical and multi-scale finite element analysis to the non-linear, failure response of composite structures. These traditional and modern computational approaches are holistically presented, providing insight into a range of non-linear structural analysis problems. The classi...

The structural behavior of Neoria masonry monument is studied here. The determination of structural and material properties of a partially collapsed monument and the evaluation of existing damages and their importance for further restoration studies are not trivial tasks. The investigation has been based on detailed geometric data, collected from s...

Materials with negative Poisson?s ratio are called auxetics and they present enhanced properties (e.g. damping, indentation resistance, fracture toughness and impact resistance) under external loadings. The auxetic properties are derived from peculiar-shaped microstructures, such as starshaped frames. In the present investigation, several applicati...

Fusion of data mining and computational mechanics is a modern approach for the exploitation of available data within rigorous modelling. First steps in this direction have been focused on the usage of neural networks and other soft computing tools as metamodeling tools. This framework seems suitable for numerical homogenization techniques realized...

Optimal design and analysis of three-phase graphene/fibre reinforced laminated nanocomposite plates with respect to maximizing the fundamental frequency is the subject of the present study. Optimal design solutions are given for four different sets of design parameters. First design problem determines the optimal graphene contents of individual lay...

Masonry structures without mortar or with mortar of low quality are used in several infrastructures, like bridges and retaining walls Unilateral contact plays a crucial role in their stability. Limit analysis and nonexistence of solution are related to the creation of collapse mechanisms. Open source and freely available software can be used for th...

Base isolation is a widely-used method used to minimise the harmful effects of earthquakes on buildings. Unlike a fixed base building, a building with a base isolation system essentially decouples the superstructure from the substructure resting on the ground. Then, during earthquakes, the superstructure’s relative displacement is significantly red...

A band gap region, or simply a band gap, is a range of frequencies where vibrations of certain frequency ranges are isolated. In the present paper, such ranges are sought through the study of different cases for the shape of the unit cells of a lattice, i.e., of an assembly of classical structural elements, such as beams and plates. A lattice with...

Present work investigates the biaxial buckling of three-phase, angle-ply laminates reinforced with graphene platelets and carbon or glass fibres. The analysis is based on Classical Plate Theory with the shear effect neglected. The laminate is defined as a three-ply symmetric laminate with simply supported boundary conditions and with different grap...

In this article an overall procedure is proposed, for the numerical investigation of the structural response of ancient monuments made of megalithic stones. The procedure is implemented on the middle temple of the Mnajdra Megalithic structure, listed as UNESCO World Heritage and regarded as one of the oldest structures from early civilization datin...

Methods used for the structural evaluation of masonry structures and monuments are presented in this article. Limit analysis is initially presented as a tool for the study of the collapse mechanism and limit load of masonry structures. Unilateral contact-friction laws are introduced between the stones, to describe damage due to opening-sliding. Rel...

A computational homogenization method is presented in this article, for the investigation of localization phenomena arising in periodic masonry structures. The damage of the macroscopic, structural scale is represented by cohesive cracks, simulated by the extended finite element method. The cohesive traction–separation law along these cracks is bui...

In the present article the failure behaviour of a steel, beam type element supported against fire by protection boards, is studied. Three – dimensional, coupled temperature-displacement, non-linear finite element analysis models have been developed to simulate the unprotected and protected structure. A simple modelling approach is proposed for the...

In the present investigation, a band-gap region, i.e. the isolation of certain frequencies, through the optimization of the shape of the unit cells of a lattice is considered. In general, a lattice is considered as an assembly of classical structural elements, such as beams, plates, etc. Each cell of the lattice is discretized using the finite elem...

In this article a numerical approach is proposed for the investigation of composite materials, like masonry. A number of simulations of a nonlinear, heterogeneous microstructure with gradually increasing loading, are considered. Average stress and stiffness are also derived. Then, this information is incorporated in databases, and a metamodel is cr...

The structural behaviour of Frangokastello, a mediaeval masonry castle located in Crete, Greece is studied. The structure presents several damaged areas, consisting of cracks and local failure of masonry. The finite element method (FEM) is used to investigate how the existing failure of the structure affects its mechanical response. First, an eigen...

Stone arch bridges are part of the cultural heritage for many countries. Their construction was based on materials easily available locally, e.g. stones and mortar. The weak-in-tension material dictated the shape of the structures. Many stone arches still survive and some are even used as pedestrian bridges or bridges for light traffic, therefore a...

Delamination between the layers of smart composite beams is a possible failure type. The effectiveness of active vibration control, when delamination appears, is investigated in this article. In particular, optimized fuzzy controllers are developed and tested on partially delaminated piezocomposites. A finite element model based on layerwise theory...

In this paper a novel approach for the investigation of pathological problems in masonry arch bridges using inverse analysis procedures is proposed. A real case study located in Kakodiki village on the island of Crete (Greece) is considered for the application of the proposed computational scheme. The method uses the damaged condition of the bridge...

Various models of smart composite beams and plates with piezoelectric layers, with glue have been created. The finite element method has been used for the numerical solution of related static and dynamic problems. Furthermore, delamination between the various layers has been modelled, in order to estimate one of the most commonly appearing damage i...

The design of novel mechanical microstructures having auxetic behaviour is proposed in this paper using techniques of topology optimization for compliant mechanisms. The resulting microstructure can be modified in order to cover additional needs, not included in the topology optimization formulation. Classical structural optimization, contact mecha...

Several numerical models are presented in this article, for the study of the ultimate behaviour of a real stone arch bridge. For the exact representation of the geometry an integral and comprehensive survey involving Terrestrial Photogrammetry and Ground Penetrating Radar is in order to provide a realistic 3D geometric model for the subsequent mech...

Ideas related to the numerical analysis of masonry structures are presented in this article. Terrestrial photogrammetry methods are used for the exact representation of the geometry of the structures. Numerical models are then developed for the study of the mechanical behaviour of masonry. Non-linear finite element analysis models with principles t...

The design of mechanical microstructures having auxetic behaviour is proposed in this paper using techniques of topology optimization for compliant mechanisms. A robust hybrid algorithm based on evolutionary algorithms and local search steps is used. The result may need verification in order to accommodate needs not taken into account in the topolo...

The article presents a three-dimensional nonlinear finite-element model that was developed for the study of a top and seat angle bolted steel connection with double web angles. Unilateral contact and friction laws were used to simulate the interaction among the connected parts. Large displacements as well as the von Mises failure criterion were als...

Numerical homogenization is based on the usage of finite elements for the description of average properties of materials with heterogeneous microstructure. The practical steps of the method and representative examples related to masonry structures are presented in this paper. The non-linear Representative Volume Element (RVE) of the masonry is crea...

In this article the behaviour of an extended end-plate steel connection under elevated temperatures is studied using three-dimensional non-linear finite elements with unilateral contact and friction interfaces. The behaviour of the connection up to collapse has been studied. Within this study, the influence of the sequence between thermal–mechanica...

This paper presents a numerical investigation of the mechanical behaviour of extended end - plate steel connections including comparison with full size experiments. Contact and friction laws have been taken into account with nonlinear, three dimensional finite element analysis. Material and geometric nonlinearities have been implemented to the mode...

Unilateral contact effects arise in masonry structures due to the absence of mortar or its low quality. Techniques from nonsmooth mechanics and mathematical programming, especially complementarity problems, can be used for the structural analysis and the calculation of the limit load and collapse mode. Modified damage mechanics theories can be used...

The ultimate failure load of stone arch bridges is calculated in this paper. The finite element model consists of contact interfaces which simulate potential cracks. A parametric investigation demonstrates the influence of the geometry on the mechanical behavior. A reduction of the rise of the arch (below the initial, real geometry) generally cause...

In this article a comparison between two non-linear finite element approaches for the numerical estimation of the ultimate failure load of masonry arches is presented. According to the first model, the geometry of the arch is divided into a number of unilateral contact interfaces which simulate potential cracks. Opening or sliding for some of the i...

A masonry arch consists of masonry blocks and mortar joints. Blocks have high strength in compression and low strength in tension while mortar has generally low strength. The men- tioned variation in the mechanical properties of the bridge's materials makes the study of them quite demanding and leads to the development of a number of theories in or...

A method for the estimation of the limit load and the failure mode of fiber-reinforced polymer (FRP) reinforced stone arch bridges is hereby presented. Unilateral contact interfaces with friction simulating potential cracks are considered in the finite element model of the bridge. FRP strips are then applied to the intrados and/or the extrados of t...

In this paper is studied the ultimate failure (limit) load of stone arch bridges. The proposed model is based on finite element analysis with interfaces, simulating potential cracks, which allow for unilateral contact with friction. Opening or sliding of some interface indicates crack initiation. The ultimate load has been calculated by using a pat...

The ultimate failure load of stone arch bridges is calculated in this paper by using finite element analysis. Contact interfaces simulating potential cracks are considered. Opening or sliding of a number of the potential interfaces indicates crack initiation [1]. Fiber Reinforced Plastic (FRP) strips are then applied to the stone bridge and the ul...

We consider stone bridges with unilateral mortar joints and elastic or rigid stones [1], [2]. Opening or sliding indicates crack initiation and propagation. The ultimate load has been calculated by using a path - following technique. Lack of a solution at a certain level of loading indicates onset of failure, which can be checked by the solvability...

In the present work the ultimate failure load and the collapse mechanism of a stone arch bridge are estimated by the usage of (a) a multi - part elastic model with unilateral contact frictional interfaces and (b) a continuous damage model. According to the contact model, contact interfaces simulating potential cracks are considered and their openin...

The limit load of a stone arch bridge can be identified by the lack of solvability of a finite element analysis including contact interfaces that simulate potential cracks. Opening or sliding at some of them indicates crack initiation. The ultimate load has been calculated by using a path -following (load incrementation) technique. The method is ap...