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Publication Type: search.filters.UBSTyp.KonferenzbeitragAuthor: search.filters.author.Eligehausen, RolfStart date: 1990End date: 1994

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Now showing 1 - 10 of 30
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    Simulation of cracking and failure of concrete structures
    (1990) Cervenka, Vladimir; Eligehausen, Rolf
    The computer simulation of the cracking process in concrete structures is performed by means of the program system SBETA. The program is based on nonlinear hypo-elastic constitutive model, which covers all important, experimentally derived material properties, namely, cracking, nonlinear stress-strain law in compression, softenning in compression and tension, biaxial failure function, etc. The nonlinear fracture mechanics is included by means of the fictitious crack model and smeared crack approach. Two examples of computer simulation of concrete fracture are shown. In the first example, the failure mode of a pull-out test is presented. In the second example, the process of the crack development and shear failure of a reinforced concrete beam is simulated.
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    Computer simulation of anchoring technique in reinforced concrete beams
    (1990) Cervenka, Vladimir; Pukl, Radomir; Eligehausen, Rolf
    The load transfer in reinforced concrete structures by means of anchoring elements is very common in modern concrete technology. Anchoring elements are often inserted in the bottom surface of a structure and the load is transfered by tensile action of the concrete. In case of shear failure, the anchores are located in the most exposed tensile zone of beams. The shear failure can be thus influenced by anchoring elements. This effect was analysed by means of the finite element program SBETA, which is based on the nonlinear-elastic constitutive model. The comparison with experiments for several loading configurations was made. In the second part a computer simulation of similar experiments was conducted.
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    Computer simulation: splitting tests of concrete thick-walled rings
    (1992) Pukl, Radomir; Schlottke, Bernd; Ozbolt, Josko; Eligehausen, Rolf
    Two non-linear program systems are used for a computer simulation of splitting failure of thick-walled concrete rings under internal radial pressure. Results of the numerical analyses for plane stress models, axisymmetrical model and 3D model are compared with available experimental data and empirical formulas. It is shown, that the behavior observed in experiments can be simulated, using advanced material models, namely the non local microplane model and SBETA material model based on the crack hand theory. With increasing outer radius of the ring, a size effect can be observed.
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    Size effect of the concrete cone failure load of anchor bolts
    (1992) Eligehausen, Rolf; Bouska, Petr; Cervenka, Vladimir; Pukl, Radomir
    The concrete cone capacity of headed anchor bolts subjected to axial tension load was experimentally investigated using 35 concrete specimens of three different sizes. The dimensions of the test specimens were varied in proportion to the embedment depth h (h = 50, 150 and 450 mm). Material properties were measured on accompanying specimens. The measured failure loads are compared with other experimental and numerical investigations. According to the present results the failure loads increase in proportion to h 16, that means close to the prediction by linear fracture mechanics.
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    Post-processing tools for nonlinear fe analysis of concrete structures
    (1990) Cervenka, Vladimir; Pukl, Radomir; Eligehausen, Rolf
    Finite clement analysis of the cracking process in concrete structures brings new requirements for the post-processing environment. Crack direction and location are important for identification of the failure mode. The problem have been solved in the finite element program SBETA which was developed by the authors for simulation of the failure processes in reinforced concrete structures. The post-processing system creates the graphical images of crack patterns. Graphical sequences for simulation can be generated.
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    Numerical analysis of headed studs embedded in large plain concrete blocks
    (1990) Ozbolt, Josko; Eligehausen, Rolf
    Anchoring elements such as headed studs, expansion, grouted or undercut anchors are used for local transfer of loads into concrete members. Parameter study of the behavior of headed stud anchors with embedment depth h v= 130 mm and failing by pulling out a concrete cone, is performed through numerical analysis. Compression and tension strength, fracture energy and the head diameter are varied. Numerical analysis is performed using nonlocal microplane model and axisymmetric finite elements. Results of the analysis are compared with experimental results.
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    Rotation capacity of prestressed concrete members
    (1992) Eligehausen, Rolf; Li, Longfei
    A numerical investigation on the behaviour of plastic hinges in prestressed concrete structures is presented. The object of the study is to determine the rotation capacity of prestressed concrete members which is needed to predict the amount of moment redistribution in hyperstatic prestressed concrete structures. A numerical model has been developed for the analysis of plastic hinges in prestressed concrete structures. It is based on a simply supported beam which simulates the region between two points of zero moment in a continuous beam. A discrete crack model has been applied in the numerical analysis. Realistic constitutive laws of steel, concrete and bond of reinforcing and prestressing steel have been assumed, respectively. The developed model enables an accurate analysis of the load deformation response of a statically determinate prestressed concrete beam with bonded or unbonded tendons under monotonic loading throughout all behaviour states up to failure . The parameters influencing the rotation capacity of prestressed concrete beams were studied by means of the numerical model.
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    Fastening elements in concrete structures - numerical simulations
    (1993) Ozbolt, Josko; Eligehausen, Rolf
    Anchoring elements such as headed and expansion studs and grouted or undercut anchors, are often used for local transfer of loads into concrete members. In order to better understand the failure mechanism, a large number of experiments have been carried out in the past. However, due to the complicated three-dimensional load transfer a very few or no numerical studies have been performed for a number of different fastening situations i.e. influence of the embedment depth, crack-width inftuence (fastening in cracked concrete), influence of the edge distance etc. Therefore, in the present study some results of the axisymmetric and three-dimensional numerical analysis of the headed studs embedded in plane concrete block are presented. Influence of different geometrical and material parameters have been studied employing finite element method and nonlocal microplane model. Comparison between experimental and numerical results indicate reasonable good agreement. Generally it has been observed that the failure mechanism is governed by fracture energy rather than by tensile strength of concrete. As a consequence, the size effect is strong and close to linear elastic fracture mechanics.
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    Creep and fatigue analysis of reinforced concrete structures
    (1992) Eligehausen, Rolf; Kazic, Mihajlo; Sippel, Thomas M.
    A computional procedure for the creep and fatigue analysis of reinforced concrete structures exposed to flexure is presented. The fatigue loading effects are modified into an equivalent creep analysis. The analysis is based on the finite element method employing beam elements. The material behavior of steel, concrete and bond between reinforcement and concrete are described as realisticly as possible. For the reinforcing steel the stress-strain behavior as measured in tests or given in codes is assumed. For the stress-strain behavior of concrete in compression under static loading, the proposal by Park/Pauley is taken. The influence of sustained or fatigue loading is taken into account by using the isochrone σ-ε-relationship valid for t > t o or N > 1 respectively; whereby the creep coefficients for both type of loadings are taken from MC90. For sustained and fatigue loading the isochrone bond stressslip relationship is used. The creep coefficients are taken from MC90. The accuracy of the proposed model is checked by comparing the behavior of some test beams under sustained and fatigue loading with the predictions.
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    Simulation of cycling bond-slip behavior
    (1992) Ozbolt, Josko; Eligehausen, Rolf
    In the present paper results of a numerical analysis for a deformed steel bar embedded in a concrete cylinder and pulled out by monotonic and cyclic loading are shown and discussed. The analysis is performed by the use of axisymmetric finite elements and an improved 3D general microplane model for concrete, instead of the classical interface element approach, a more general approach with spatial discretization modeling the ribs of a deformed steel bar is employed. The pull-out failure mechanism is analyzed. Comparison between numerical results and test results indicate good agreement. The present approach is able to correctly predict the monotonic as well as cyclic behavior including friction and degradation of pull-out resistance due to the previous damage.