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The mechanical behavior of timber beams with a slotted-in steel plate connection is studied by creating a numerical model that is able to simulate the global bending behavior, the global load carrying capacity and the nonlinear plastic fastener force distribution in the connection. Experimental results from Material Testing Institute (MPA), University of Stuttgart were used to verify the simulation results from this study. The modeling of both the timber beams and the mechanical connections is performed with shell, beam and nonlinear connector elements. Three models were created, where the first model was a single-dowel double shear joint model to study the ability to use structural elements in the modeling of the test beams. It was used to simulate some of the basic failure modes in Eurocode 5 (EC5). The second model was a beam model used to simulate the bending of a jointed timber beam with a slotted-in steel plate connection, where only two connector elements were used to model the joint behavior of each dowel group. It can be used to study the global deflection and the load carrying capacity of the jointed timber beams. The third model was a combined beam-shell model where the beam elements are used for the timber parts outside the connection area and the fasteners, while the shell elements are used for the slotted-in steel plate and the timber parts within the connection area. It uses two nonlinear connectors to connect each dowel to the wood and a pure coupling constraint to connect the dowels to the slotted-in steel plate. This model can simulate the same phenomena as model two and also the development of the elasto-plastic shear force distribution in all the dowels. All the models were created using parameterized Python scripts, which makes it possible to easily change different input parameters. Most of the modeling results show good agreement with both experimental results and with calculated load carrying capacity results for individual dowels according to EC5. The use of the structural elements (beam, shell, and connector elements) was found to result in much less computational time compared to the use of solid elements.

The thesis aimed to identify fracture strain for multiaxial loading for laminate material of Al and LDPE that is mostly used in the food packing technology specially in liquid packaging industry. These materials are thin and flexible which make it difficult to handle and test it. The investigation was through applying new Nakajima test setup on such a material by designing a custom setup and 3D printing the Nakajima setup prototype to be able to use it in this study. DIC technique was used to get the results from the Nakajima test and the software used to apply the DIC technique is GOM correlate. As a validation for measurement from such a technique, a tensile test has been done and measured strains were compared with those from the specimen from the Nakajima that has smallest width as it was close to a uniaxial loading. One more validation technique was by creating a FE-model using (Abaqus software) for the biaxial loading and comparing it to the biaxial loading results that obtained from the DIC analysis.

Different rock formations may appear within the same mass, or even within the same formation there may exist layers of different materials, creating interfaces between layers (an interface may be defined, in more general terms, as a frictional contact that separates two similar or dissimilar materials). Currently, there is no well-established experimental work that investigates the influence of frictional interfaces, interface orientation and flaw geometries on crack behavior (i.e. initiation, propagation and coalescence) in brittle specimens under compressive loading. A series of experiments on homogeneous gypsum specimens, used as a rock-model material, containing two pre-existing open flaws and a frictional interface has been performed under uniaxial compression. The experiments investigate how cracks interact with interfaces and how different variables (i.e. flaw geometry, interface inclination angle and interface roughness) affect crack behavior in homogeneous materials separated by an interface. The specimens are 203.2mm high, 101.6mm wide, and 25.4mm thick. The two flaws, with 0.1mm aperture and 12.7mm length (2a), are created through the thickness of the specimen. The spacing (S) between flaws, continuity (C), and inclination angle, measured from the horizontal, (β) define the geometry of the flaws. Three flaw geometries are tested: S=0, C= -2a= -12.7mm, β= 30° (i.e. a left-stepping geometry); S= 2a= 12.7 mm, C=a=6.35 mm, β= 30° (i.e. an overlapping geometry) and S= 3a= 19.05mm, C=0, β= 30° (i.e. a right-stepping geometry). Smooth and rough unbonded interfaces are created by casting the specimen in two parts. The first half of the specimen is cast against a PVC block with an inclined face (i.e. 90°, 80° or 70°) with respect to the vertical axis of the specimen. The second half is then cast against the first one. Sandpaper may be attached to the PVC block to provide different roughness to the interface; a debonding agent applied to the interface ensures a cohesionless contact. In the experiments, digital image correlation (DIC) is used to monitor crack propagation on the specimen surface. The experiments indicate that the interface itself is an important contributor to new cracks and its presence in the specimens reduce crack initiation stress. Furthermore, the increase in roughness and inclination of the interface (i.e. from horizontal to 70° from the vertical) causes crack initiation stress to decrease. It was also observed that the angle between the incident crack plane and the interface affects whether an incident crack will penetrate an interface or be arrested: Tensile cracks that meet the interface at 30° to 60° angle get arrested, while those at or above 70° cross the interface with an offset of 0 – 1.2 mm. While shear cracks that meet the interface at 20° to 63° angles get arrested at the interface, while those at or above 70° cross the interface with an offset in the range of 0 – 1.76 mm. Another relevant finding is the fact that changes in interface roughness or inclination angle did not affect the angles at which cracks initiate or reinitiate at the interface.<div>A numerical study was conducted using the Extended Finite Element Method (XFEM) capability in ABAQUS, to further investigate the fracture behavior observed in the experiments and, more specifically, the influence of the different types of interfaces. An extensive investigation of the stress fields around the tips of the flaws and of the new cracks, as well as along the interface in the specimens, was conducted to determine the relationship between stresses and crack initiation and propagation (i.e. type and direction of cracks). The stress-based approach yields predictions of tensile and shear cracks location and initiation direction that are in good agreement with experimental results. The numerical investigation indicated that rougher horizontal interfaces induced slightly higher tensile stresses around the interior and exterior flaw tips than smoother interfaces, which may explain why tensile cracks at these locations initiated earlier in specimens with a rough interface. Moreover, inclined interfaces induced higher tensile stresses around the interior and exterior flaw tips than horizontal interfaces, which may justify that, in the experiments, inclined interfaces promoted crack initiation earlier than horizontal interfaces.</div>

The use of composite materials brought a tremendous breakthrough in the scientific world of aerospace engineering. The lack of understanding of the failure of composite materials can be disastrous. Composite laminated structures need to be thoroughly studied and investigated in the design stage. In this thesis, formed-hat skin stringer made of composite laminates is investigated. Delamination is the most common failure of laminated composites, which has two stages delamination onset and delamination propagation. In the preliminary design phase, firstly the structures need to be investigated for low-velocity impact to check the formation of damage onset due to the impact that may arise during manufacturing. In the detailed design phase, the structure is investigated to study the evolution of delamination growth under loading conditions. The structure is modeled using 3 D elements because of the presence of Interlaminar stresses in the width and thickness direction and anisotropic nature. In this thesis, more emphasis is given on the interface between the skin and the stringer. The debonding effect of the interface is studied using cohesive zone model(CZM).

In recent time, some of the construction processes of multi-storey timber buildings are achieved by using prefabricated volume modules since this method is very beneficial due to its high prefabrication level and the fast on-site assembly of the modules. The main structural component of these modules is a light-frame shear wall that stabilizes these modules from the effect of horizontal forces. A shear wall typically consists of timber frame with studs and rails and sheathing panels connected by dowel type fasteners to one or both sides of the frame. The structural behavior of shear wall and its racking performance is controlled by adequate design of its mechanical joints where sheathing-to-framing joints is the key issue in evaluating the overall behavior of shear wall. This study mainly deals with modelling of light-frame shear walls based on linear elastic characteristic for sheathing-to-framing joints. The objective of this study is to create two effective computer-based models (beam-spring-shell and beam-spring-shell-solid) to predict linear behavior of light-frame shear walls. In addition, the study deals with an experimental investigation of various types of short light-frame shear walls. Finally, the study compares modelling and experimental results to verify that they are in good agreement and that an efficient FE model is able to predict the structural behavior of shear walls for a short computational time. The study optimizes use of beam-spring-shell model which is as reliable as the beam-spring-shell-solid model, emphasizing its advantages over the resource-consuming solid model. The beam-spring-shell model is efficient and can be implemented and used for design and analysis of modular-based timber buildings.

High magnitude earthquakes have devastating effects that leads to severe human and material losses; when affecting concrete gravity dams, seisms devastate the surrounding habitat through sudden release of reservoir. Dam safety is therefore a significant issue to be accounted in order to prevent the failure of dams located in seismic regions. The Baozhusi dam, the case study of this thesis, was exposed to 8.0 Ms (at the Mercalli scale) Wenchuan earthquake 2008 with intensity of (0.148 g) at the dam site. The earthquake intensity exceeded the design level of the dam (0.1 g); yet, the Baozhusi dam was not severely damaged as showed by tests. The present study case is a modeling and analyzing of the dynamical behavior of the Baozhusi dam during the earthquake duration. The results show that the horizontal component of the ground motion predominate the dynamic response of the dam. It is confirmed that the horizontal component of the ground motion crossed the dam at its axis and therefore minimizing the damages on the concrete gravity dam.

In this thesis six different models of IPE240 have been created in order to study their behavior undershear, bending and torsion. These models simulate IPE240 but differ in the boundary conditions, inthe loading and the length of the beam and in some connections which connect certain elements. Inthis study the modeling and simulation of the steel member is executed in ABAQUS Finite ElementAnalysis software with the creation of input files. When developing a model for the finite elementanalysis a typical analysis process is followed. All the parameters that are required to perform theanalysis are defined initially to geometry which is half the beam due to symmetry, and the materialproperties of each model are defined too. Then a mesh is generated for each model, the loads of eachmodel are applied which are expressed as initial displacement. Subsequently, the boundary conditionsfor each model are defined and finally the model is submitted to the solver when the kind of analysishas been defined. Namely, the analysis which is performed in this thesis is static stress analysis.When the ABAQUS has run the models, the contour plots for the von Mises stresses for each modelare studied. In these contour plots, a large concentration of stresses and problems which arise in eachone of the models are notified. As it has been observed in all models, the beam yields at the flangesof the mid-span and collapses at the mid-span. Therefore, the failure at the mid-span is more criticalthan the failure at the support. Moreover, the beams are weak in bending due to the fact that theytwist almost 60-90 degrees under a large initial displacement at the control node. Additionally, much localized failure and buckling occurred at the mid-span, and local concentrated stresses also occurredat the bottom flange at the support due to the boundary conditions details.Thereafter, a verification of the results of the ABAQUS through the simple analytical handcalculations is performed. It is concluded that the error appearing in most selected points is small.However, in some points in the web of the mid-span the error is greater. Additionally, whilecomparing the load-displacement curves of the two different plastic behaviors, it is observed that themodel with an elastic-plastic with a yielding plateau slope behavior has smaller maximum loadresistance than the model with a true stress-strain curve with strain hardening behavior.Finally, some errors and warning messages have occurred during the creation of the input files of themodels and a way of solving them is suggested.

The eXtended Finite Element Method is a partition of unity based method, particularly suitable for modelling crack propagation phenomena, without knowing a priori the crack path. Its numerical implementation is mostly achieved with stand-alone codes. The implementation of the eXtended Finite Element Method in commercial FEA softwares is still limited, and the most famous one including such capabilities is Abaqus TM. However, due to its relatively recent intro-duction, XFEM technique in Abaqus has been proved to provide trustable results only in few simple benchmark problems involving linear elastic material models.In this work, we present an assessment of the applicability of the eXtendend Finite Element Method in Abaqus, to deal with fracture mechanics problems of rubber-like materials. Results are provided for both Neo-Hookean and Arruda-Boyce material models, under plane strain conditions. In the rst part of this work, a static analysis for the pure Mode-I and for a 45o mixed-Mode load condition, whose objective has been to evaluate the ability of the XFEM technique in Abaqus, to correctly model the stress and displacement elds around a crack tip, has been performed. Outcomes from XFEM analysis with coarse meshes have been compared with the analogous ones obtained with highly re ned standard FEM discretizations. Noteworthy, despite the remarkable level of accuracy in analyzing the displacement eld at the crack tip, concerning the stress eld, the adoption of the XFEM provides no bene ts, if compared to the standard FEM formulation. The only remarkable advantage is the possibility to discretize the model without the mesh con-forming the crack geometry. Furthermore, the dynamic process of crack propagation has been analyzed by means of the XFEM. A 45o mixed-Mode and a 30o mixed-Mode load condition are analyzed. In particular, three fundamental aspects of the crack propagation phenomenon have been investigated, i.e. the instant at which a pre-existing crack starts to propagate within the body under the applied boundary conditions, the crack propagation direction and the predicted crack propagation speeds. According to the obtained results, the most inuent parameters are thought to be the elements size at the crack tip hand the applied displacement ratev. Severe diculties have been faced to attain convergence. Some reasonable motivations of the unsatisfactory convergence behaviour are proposed.

Understanding the true behaviour of impacted structures is the only way to assess their robustness under exceptional events such as vehicle collision. The primary objective of this master’s thesis was to perform a finite element parametric investigation on the influence that some parameters have in steel buildings subjected to vehicle impacts. The parameters chosen for the study, involved uncertainties in the material definition and in the load configuration of the bolts used in the impacted column end-connections. By using the Abaqus software, a finite element model of the structure has been created. The five storey steel building considered has been modelled in a simplified manner with the exception of the impacted area which, instead, has been defined in a more detailed fashion. During the simulations, different preload conditions have been used, comparing cases with and without the preload force. Regardless its variation, it has not been observed any increase in the structural resistance. On the other hand, the simulation provided interesting results for what concerns the material variations in the bolts. Although the changes have been small in magnitude, the effect on the structural response during the impact was remarkable. For all the cases considered, an increase of the material ductility, achieved by increasing the ultimate strain at failure, entailed higher resistance of the connections. Various failure modes have been observed when the material properties have been changed. Having clarified the influence of the assumptions made, the results provided helpful information in sight of future studies. Although the model still needs to be validated, the research clarified which of the parameters investigated are to be collected with more attention. Keywords: Vehicle collision, steel building, FE model, Abaqus/Explicit, parametric investigation, bolt preload, bolt material.