Analysis of aircraft structures are mainly performed by assuming that the structure behaves linearly. In linear finite element analysis, it is assumed that deformations are small, thus geometric nonlinearity can be neglected. In addition, linear analysis assumes that linear constitutive laws applicable, implying that material nonlinearity can also be neglected. One very common type of nonlinearity is associated with the boundary conditions. Contact between two deformable bodies or between a deformable and rigid body are typical examples of nonlinearity associated with boundary conditions. Linear structural analysis, in general, does not include contact analysis. Simplicity of linear analysis in terms modeling, interpreting the results and solution time makes the linear analysis approach very convenient in preliminary design and analysis stage of aircraft structures. However, simplicity of linear analysis may result in unconservative results which may occur due to neglecting the true nonlinear behavior of the structure. In this thesis, one such nonlinear eect called prying load eect on the tensile connections is studied. The eect of prying load on structures are initially described by referencing the analytical approaches presented in the literature. Finite element models of typical bolted connections such as L and T type are generated for various combinations of the chosen design parameters such as bolt diameter, flange thickness, washer diameter and edge distances. Parametric modeling approach is used to perform the high number of finite element analysis which involve contact for the purpose of calculating the prying load. Comparative study of the eect of prying load is then conducted by also including the results presented in the literature. Comparisons of the prying load are done with the experimental results presented in the literature. Series of finite element analyses are preformed for various cases such that eect of geometrical variables and bolt preload on prying ratio can be understood. According to the results obtained, it is concluded that main factors eecting the prying ratio are the distance of bolt center to the clip web, flange thickness of the clip and preload on the bolt where the eect of edge distance of the bolt is insignificant.

The purpose of the work resulting in this report is to develop a mechanically enhanced breaking bar, or prying bar, for bringing down trees. There was already a prototype to study, which was assembled by welded steel components. A specification of demands took form after continuous technical discussions with the inventor, assignee and mentors. When an analysis of this device and its function was made, the work continued with calculations to establish the foundation to design a mechanical model. Geometrical relationships were established to design the sub-components of the breaking bar and its functions. Simulations regarding material strength and mechanical function were made by the use of different modules in the CAD-software Solid Works and led to a simplified version of the breaking bar. The new simplified version was accepted by the inventor and the drawings for the new tool could now be made. During the time of this work the inventor has prepared his patent request and therefore this work has been classified and considered under secrecy for the inner circle persons containing the Kogertek-employees. The breaking bar which was produced with its powerful gear ratio is amplifying the force from the handle by a factor 25 and lifts 50 mm in the felling cut of the tree. In theory the tool would weigh approximately 1800 grams and can be used to bring down a tree with a diameter of at most 40 cm. Drawings for the constituent components were sent to a workshop to be manufactured and a mechanical breaking bar was assembled and tested.

No description available.

This master thesis deals with analytical calculation of the various flange connections using theory of thin-walled bodies and axisymmetric assumptions. The calculation is demonstrated by one specific geometry configuration. Numerical finite element method was performed to verify analytical calculation model and also this method enabled more in-depth analysis of the prying effect which has negative influence on the bolt connection tensile load. Output from this analysis is prying point location function in plate thickness dependence and application this function into analytical calculation.

The difficulty in developing bolted connection designs lies in the limitations in existing methods to characterize their strength and typically nonlinear response due to the complex interaction of the bolts and structural components. Yet it is necessary for the engineer to be able to determine the three main connection response characteristics: stiffness, strength, and ductility to account for their influence on the overall structural response behavior. The need for better connection response characterization becomes even more crucial in a performance based design approach or when designing partially-restrained moment frames. Several welded moment resisting frame connections were found to have serious failures following the 1994 Northridge earthquake leading to more interest and research on bolted connections as an alternative. In this study a refined three dimensional nonlinear finite element modeling approach to accurately simulate the response of bolted connections is presented. Sensitivity studies of modeling parameters are also performed. A nonlinear response dataset of over 400 connection cases is generated using this approach with a parametric bolted angle connection model. The use of a parametric Richard-Abbott type function and a neural network, calibrated using the response dataset, as practical tool to model the nonlinear stiffness response of bolted connections under monotonic loading is demonstrated and assessed. Failure criteria that can be practically used in conjunction with the refined three dimensional finite element models without any additional modeling requirements are developed. The stress modified critical strain (SMCS) criterion based on the void growth and coalescence mechanism initiating ductile fracture in steel is used for determining failure in the connection member. The bolt failure criterion developed is a mechanics based model using the elliptical interaction of the tensile and shear capacity envelope. The failure criteria and bolted angle response dataset is combined to assess in detail the impact of geometry and topography of the bolted angle connections on the following response characteristics: strength, initial stiffness, plastic stiffness, and absolute ductility or the displacement capacity. Finally, using the dataset of bolted angle connection response, along with their capacities and failure modes determined using the developed failure criteria, the prying strength models in the AISC LRFD Specifications, Eurocode, and a hybrid model are assessed and found to be very conservative for some cases. Based on these results a modified Eurocode and hybrid prying strength model is proposed which greatly improves the prying strength prediction. These prying models are assessed and verified using experimental data found in literature.

In order to predict the behaviour of bolted steel connections, different methods can be applied to calculate the design tension resistance. In this thesis, the tension resistance is evaluated in the context of the so called Component Method according to Eurocode 3 part 1-8. The design approach establishes a unified procedure of modelling steel joints. Each joint configuration is decomposed into its basic components depending on loading type. In order to design the resistance of components subjected to tensile forces, a simple substitute model, the so-called Tstub flange is adopted. The Component Method is rather complicated to apply for all joint configurations. Therefore, the aim of this thesis is to create a brief and facilitated handbook covering the most common types of connections Kadesjös’ engineers deal with. The topic to be studied is rather comprehensive. Thus, this work is only focusing on the resistance calculation of components located in tension zone of HEA-sections in order to go deeper into the equivalent T-stub approach. To get a complete view about the designing procedure, general information about the Component Method are gathered by a literature study. Thereafter, the technical rules for calculation introduced in codes and standards were used to generate a general solution algorithm for two different connection configurations. The calculations have been performed using Mathcad, and the obtained results from a parametric analysis for particular profiles in each example are then summarised in tables and diagrams using Microsoft Excel. / Att förutse skruvförbands beteende kan kräva tillämpning av diverse metoder. Metoderna används för att kalkylera den dimensionerande lastkapaciteten. I denna avhandling värderas lastkapaciteten i enlighet med den så kallade Komponentmetoden från del 1-8 i Eurokod 3. Denna dimensioneringsmetod fastslår en enhetlig procedur när det gäller modelleringen av stålförband. Varje förbandstyp bryts ner till sina baskomponenter med avseende på belastningstypen. För att beräkna den dimensionerande lastkapaciteten för dragbelastade komponenter används en förenklad substitutionsmodell en så kallad T-knut. Komponentmetoden är något komplicerad att tillämpa för alla former av skruvförband. Därmed är den huvudsakliga ambitionen med arbetet att skapa en kortfattad handbok vars syfte är att täcka de vanligaste typerna av skruvförband som Kadesjös konstruktörer använder sig av. Ämnet som kommer att studeras är relativt omfattande, således bestämdes det att i huvudsak sätta fokus på bärförmågan hos komponenter i dragzonen för HEA-profiler och därav dyka djupare i den ekvivalenta T-knutmetodiken. För att få en helhetsbild av dimensioneringsprocessen samlades allmän information om komponentmetoden genom litteraturstudier. Därefter användes dimensioneringsreglerna, presenterade i koder och standarder, för beräkning av lastkapacitet. Dessa utnyttjades för att generera en lösningsalgoritm för två skilda förband. Beräkningen genomfördes med hjälp av beräkningsprogrammet Mathcad. De erhållna resultaten, från en parametrisk analys för särskilda profiler i varje exempel, sammanfattades i form av tabeller och diagram med hjälp av Microsoft Excel.