Seizmic Analysis of Masonry Structures with Finite-Discrete Element Method : Doctoral Thesis

U ovom radu je u okviru kombinirane metode konačno-diskretnih elemenata razvijen novi numerički model za simulaciju ponašanja zidanih konstrukcija izloženih statičkom, dinamičkom i seizmičkom opterećenju. U postojeći računalni program Y-2D koji se temelji na kombiniranoj metodi konačno-diskretnih elemenata implementiran je novi numerički model za simulaciju čeličnih klamfi i trnova u suho zidanim kamenim konstrukcijama. Model uključuje dva tipa klamfi i jedan tip trnova koji se najčešće koriste u kamenim konstrukcijama uzimajući u obzir mogućnost izvlačenja klamfe i trna iz kamenog bloka, mogućnost pucanja klamfi i trnova te cikličko ponašanje materijala. U sklopu ovog rada provedena je verifikacija ugrađenog modela te je prikazana njegova primjena u inkrementalnoj seizmičkoj analizi realnih kamenih konstrukcija. Također, razvijen je novi numerički model materijala za analizu nearmiranih zidanih konstrukcija. Model se sastoji od novog numeričkog modela kontaktnog elementa za simuliranje veze bloka i morta te novog modela ponašanja materijala u konačnom elementu. Model materijala u konačnom elementu uzima u obzir ortotropno ponašanje, mogućnost sloma u tlaku, pojavu tlačnog omekšanja te cikličko ponašanje materijala. Model ponašanja kontaktnog elementa za simulaciju veze morta i bloka uzima u obzir pojavu sloma u vlaku i posmiku, povećanje energije loma u posmiku uslijed povećanja predlačnog naprezanja, smanjenje koeficijenta trenja uslijed povećanja posmične deformacije te cikličko ponašanje veze morta i bloka. Valjanost modela je provjerena usporedbom dobivenih rezultata s numeričkim i eksperimentalnim rezultatima preuzetima iz literature. Prezentiran je također i novi numerički model za seizmičku analizu zidanih konstrukcija omeđenih armiranobetonskim serklažima koji se sastoji od sinteze novo razvijenog numeričkog modela materijala za analizu nearmiranih zidanih konstrukcija te prethodno razvijenog numeričkog modela za analizu armiranobetonskih konstrukcija.This thesis presents a new numerical model based on a combined finite-discrete element method, capable of predicting the behaviour of masonry structures under static, dynamic and seismic loads. A new numerical model of steel clamps and bolts in dry stone masonry structures is implemented in the available numerical cod Y-2D based on combined finite-discrete element method. Model includes several types of clamps and bolts which are frequently used in strengthening of dry stone masonry structures taking into account influence of the pulling out of the clamps and bolts from the stone block, cyclic behaviour, yielding and failure of the steel. The verification of the model and possibility of using this model in incremental dynamic analysis of real dry stone masonry structures is also shown. New material model for numerical analysis of unreinforced masonry structures was also developed. Model consists of new numerical model in contact element which simulates connection between block and mort, and new material model in finite element. Material model in finite element takes into account orthotropic behaviour, cyclic behaviour, possibility of failure and softening in pressure. Numerical model of contact element which simulate connection between block and mort take into account possibility of failure and softening behaviour in tension and shear, increasing of fracture energy in shear due to increasing precompression stress, decreasing friction coefficient due to increasing shear displacement as well as cyclic behaviour connection between mort and block. The verification of the model was performed on examples by comparing it with the results obtained with the known numerical and experimental results from literature. New numerical model for seismic analysis of reinforced masonry structures was also presented. Model consists of synthesis of new developed material model for unreinforced masonry structures and previously developed numerical model for analysing reinforced concrete structures

Three-Dimensional Finite-Discrete Element Framework for the Fracturing of Reinforced Concrete Structures

This paper presents a three-dimensional numerical model based on finite-discrete element method for simulating cracking and predicting failure in reinforced concrete (RC) structures. Discrete representation of concrete cracks is coupled with a non-linear reinforcement model where reinforcing bars interact with concrete and slip due to crack opening and steel plastic deformation. Hence, it enables a simulation of complex material behaviour of concrete and steel in cracked zones and its influence on global structural behaviour. Several numerical examples are used to study the sensitivity of the model to different numerical and physical parameters and its capabilities in the analysis of RC structures

A New Algorithm for Dynamic Analysis of Thin Plates in the Combined Finite-Discrete Element Method

This paper presents a new numerical algorithm for a dynamic analysis of thin plate structures based on the combined finite-discrete element method (FDEM). A nonlinear analysis of thin plates subjected to static or dynamic load has been provided. The model uses 3-noded triangular finite elements and is implemented in the open source FDEM package - Yfdem. The performance of the new model on simple benchmark tests is presented

Sensitivity analysis of numerical parameters in FEM/DEM model for RC structures

The application of the finite-discrete element method (FEM/DEM) in the analysis of reinforced concrete (RC) structures is still in its early stages. Therefore, in this paper, sensitivity of the numerical model for analysis of RC structures based on the FEM/DEM method to the numerical parameters is presented. The accuracy of the solution, depending on the mesh refinement, crack spacing and penalty term, was analysed. The performed numerical analyses are useful in predicting the penalty parameter and mesh density in order to minimize numerical errors in analysis of RC structures with the FEM/DEM method. Validation of the numerical model for adopted numerical parameters was also shown by comparing numerical and experimental results

Sažetak

This paper presents a new numerical model for the analysis of beam type structures. The model uses two-noded rotation free finite elements and takes into account material non-linearity, finite displacements, finite rotations and finite strains. The presented numerical model has been implemented into the open source ‘Yfdem’, which is based on the Combined Finite Discrete Element Method. The performance of the new numerical model was demonstrated on simple benchmark tests, by a comparison with known experimental and analytical results.U ovom radu prezentiran je novi numerički model za analizu grednih konstrukcija. Model koristi dvočvorne konačne elemente sa translacijskim stupnjevima slobode u svakom čvoru i pri tome uzima u obzir materijalnu nelinearnost, velike pomake, velike rotacije i velike deformacije. Prezentirani numerički model je implementiran u numerički paket ‘Yfdem’ koji se bazira na kombiniranoj metodi konačnih i diskretnih elemenata. Prednosti novog numeričkog modela demonstrirane su na jednostavnim primjerima usporedbom rezultata s poznatim analitičkim i eksperimentalnim rješenjima iz literature

Numerical model for confined masonry structures based on finite discrete element method

This paper presents a numerical model for confined masonry structures under seismic load. The model is based on a combination of the finite discrete element models for reinforced concrete confining elements and a masonry infill. Material non-linearity, including fracture and fragmentation of discrete elements, is considered through contact elements, which are implemented within a finite element mesh. The model includes the following phenomena: nonlinear cyclic behaviour of concrete, reinforcement and masonry during the seismic event, interaction between the reinforcement and concrete, cracking of the reinforced concrete confining elements and masonry units, as well as failure and softening in tension and shear for mortar joints. The application of the developed numerical model is exemplified on a confined masonry wall exposed to seismic excitation

Nonlinear analysis of engineering structures by combined finite-discrete element method

U radu je prikazan numerički model za dinamičku analizu suho zidanih kamenih i armirano-betonskih konstrukcija zasnovan na kombiniranoj metodi konačno-diskretnih elemenata (FEM/DEM). Model opisuje ponašanje takvih konstrukcija izloženih dinamičkom opterećenju, pojavu i razvoj pukotina, trošenje energije uslijed nelinearnih efekata, inercijalne efekte uslijed gibanja, kontaktno međudjelovanje i postizanje stanja mirovanja kao posljedicu trošenja energije u sustavu.A numerical model for dynamic analysis of dry-stone masonry and reinforced-concrete structures, based on the combined finite-discrete element method (FEM/DEM), is presented in the paper. This model describes behaviour of such structures when exposed to dynamic load, crack initiation and propagation, energy dissipation mechanisms due to non linear effects, inertial effects due to motion, contact impact and achievement of the state of rest as a consequence of energy dissipation mechanisms in the system

Overview of the methods for the modelling of historical masonry structures

Prikazan je pregled metoda namijenjenih za modeliranje povijesnih zidanih konstrukcija, počevši od jednostavnih klasičnih pa sve do suvremenih prikladnih za primjenu u računalnim programima. Predočena su glavna obilježja zidanih konstrukcija te glavne značajke metoda za njihovu analizu kao što su dinamičke analitičke metode, metode graničnih stanja, konačnih elemenata te diskretnih elemenata. Dan je osvrt na primjenu pojedine metode obzirom na zahtijevanu razinu točnosti, količinu ulaznih podataka te vrijeme trajanja proračuna.An overview of methods for the modelling of historic masonry structures, starting from simple traditional to modern methods suitable for use in computer programs, is presented. Main characteristics of masonry structures, as well as principal features of methods for their analysis, such as dynamic analytical methods, limit state methods, finite element methods, and discrete element methods, are presented. A review of application of individual methods with regard to the required level of accuracy, quantity of input data, and calculation time, is presented

Stability analysis of dry stone lintels using combined finite-discrete element method

U ovom radu prikazana je primjena kombinirane metode konačno-diskretnih elemenata (FEM/DEM) u analizi potresne otpornosti suho zidanih kamenih nadvoja. Sedam kamenih suhozida s različitim tipovima kamenih nadvoja izloženo je djelovanju linearno rastućeg horizontalnog ubrzanja podloge, te potresnom opterećenju. Na temelju dobivenih rezultata analizirana je potresna otpornost te mehanizmi sloma pojedinog tipa nadvoja. Također su komentirane i predložene preporuke za oblikovanje kamenih nadvoja s ciljem postizanja što veće potresne otpornosti.The use of the combined finite-discrete element method (FEM/DEM) in the analysis of seismic resistance of dry stone lintels is presented in this paper. Seven dry stone masonry walls with different types of stone lintels were exposed to linearly increasing horizontal base acceleration and to seismic excitation. Based on the analysis results, the seismic resistance and failure mechanisms were analysed for each type of lintel. Recommendations for the design of stone lintels, aimed at achieving the greatest possible seismic resistance, were also discussed and presented

Application of finite discrete element method in dynamic analysis of masonry structures

This paper presents the application of the numerical models for dynamic analysis of dry stone masonry structures strengthened with clamps and bolts and confined masonry structures based on finite discrete element method (FDEM). The proposed models considers the effects of the behavior of masonry structures due to dynamic action, crack initiation and propagation, energy dissipation mechanisms due to nonlinear effects, inertial effects due to motion, contact impact and attaining state of the rest that is a consequence of energy dissipation mechanisms in the structure. The models also include all relevant effects related to behavior of reinforcement in concrete and clams and bolts in stone blocks. The application of the model was performed on examples related to behavior of dry stone masonry structures strengthened with clamps and bolts as well as confined masonry wall