Stress analysis of composite beam components

Composite structures are formed by using a combination of different types of material. These different types of materials can be materials such as steel, wood and concrete. In this thesis, general information about composite structures is given, composite beam components are introduced and the calculation methods of composite beam components are taken into consideration and push-out tests of nine test specimens prepared in ITU Civil Engineering Building Materials Laboratories are carried out and stress analysis and size effect tests of composite beam components are performed. Analytical results obtained from the experimental work were analyzed in the Abaqus finite element method program and their tensile behaviors of the composite components were investigated. In the first part of the thesis, general information about steel concrete composite structures is given. Composite beam forming composite components that are concrete, steel profiles, trapezoidal sheet steel, concrete reinforcement and shear connectors are mentioned. Information on the basis of calculations in the presence or absence of a connecting element at the interface of composite beams after expressing what kind of shear connectors are considered as the most important component of the composite beam. The shear connector is used to tie the concrete slab and steel beam in order to transfer the horizontal shear between the slab and the steel beam without slip and at the same time to prevent vertical separation of the slab from the steel profile at the inner face. Also at this part includes types of shear connectors which called rigid type, flexible type and bond or anchorage type. Rigid type, resist shear forces through the front side by shearing and sustain a small deformation. Type of failure is generally concrete failure. Bar connector, tee connector, horseshoes connector and channel connectors are common examples of rigid type connector. Flexible connectors derive the stress resistance by bending, tension or shearing in the root and exposed to large deformation. When they reached the ultimate strength, they sustain plastic deformation. The most commonly used type is headed (stud) connector. These connectors are welded to flange of the steel beam by welded machine. During welding operation using a ceramic ferrule to ensure good welding. After describing the general properties, standard measurements and calculation method of the stud shear connector, which is the most preferred today and in this thesis used in the experimental work, the formulations for the national and international standards used in the calculation of ultimate strength capacity of the stud shear connectors are explained. In addition, in the first part, there are also literature studies and results of experimental studies which investigated the behavior of shear connectors under different conditions. Experimental studies have been carried out with push-out test method in these literature studies and numerical verification of these experimental works using Abaqus program has been explained. In the second part, finite element selection, modeling of contact surfaces, modeling of materials, boundary conditions and load assignment and calibration analysis were performed in the Abaqus program which is used for numerical verification of experimental works performed in thesis. In order to confirm the validity of the selected methods, the results of selected samples from previous experimental literature studies and the parameters related to selected method principles were used to model these samples in the Abaqus program using the finite element method. In the Abaqus program, because of the symmetry of the specimens, only one quarter of the push out test arrangement is modelled. For the concrete slabs, steel beam and stud connector a 3D eight node element C3D8R (Continuum, 3D, 8-node, reduced integration) solid element type is chosen. And for the rebar component 3D beam element B31 (Beam, 3D, 1-st order interpolation) is adopted. For material selection for concrete slab is chosen "Damage Plasticity Model" when analyse method is "static/implicit" and "Microplane Model (M7)" parameters are used when analyse method is "explicit/dynamic". Steel beam, stud connector and rebars meterial selection, bilinear stress-strain curve is used to define material model. "Explicit/Dynamic" analysis method is about time control. And this method generally used to solve progressing damage, failure of metal, the problem of impact and metal forming. This method also shows to be a powerful solution scheme for discontinuous medium, contact interaction and large deformation. Even though being a dynamic method, explicit method is also used for a quasi-static analyses. In the Abaqus program as explained, the results of analysis made by this method were more realistic. Before analyse the model the most important option is mesh the model. During analyse the model, mesh option should be more frequent intervals around the stud connector and interaction zone where stud connector embedded the concrete slab. The results of the analysis of the models that have been made are compared with the results of the literature studies which are taken as an example by creating a force-slip chart. In the third section, the properties of the test specimens to be used in the experimental work are mentioned. This part is also mentioned that the specimens are prepared in the lab and applied the test. In the push-out test, the steel profiles were welded in studs. And then concrete is poured into each head of the steel profile. So steel profiles are prepared in such a way that they remain between two concrete slabs. For each head of the steel profile, one stud connector is welded stud welding with a special welding machine. During welding stud connector used ceramic ferrule for controlling welding area. And also for understanding size effect the stud connectors size scaled by using lathe machine. Furthermore, in order to have concrete compressive strength 45-55 MPa, natural sand, crushed sand, crushed stone1, water and cement ratios are calculated in the laboratory and concrete is prepared by forming materials. The aggregates were subjected to sieve analysis in order to be able to hold the concrete class. The granulometry of the aggregates was established as a result of sieve analysis. We have a granulometry curve after all this has been achieved. After pour concrete to coupon, the specimens are kept in the concrete pool so that it can receive the curing time. After concrete casting, cylindrical concrete pressure test was done to find ultimate compressive strength of concrete. For understanding stud connector and rebars behaviour, they were subjected to tensile strength test by using tensile testing machine in ITU Civil Engineering Building Materials laboratory. After calculated ultimate tensile strength of stud connector and rebars, the values found were entered as material properties in the model made in the Abaqus program. The reinforcement mesh without ribs arranged to be the bottom and top of each concrete slab. In order to investigate the size effect in the experiment, nine samples were prepared in total, three from each sample. Specimens classified as PL1-PL2-PL3 are the largest size, the specimens are classified as PM1-PM2-PM3 prepared so that the dimensions of all composite components are half of the dimensions of the largest size and last specimens which will be the smallest specimens, the dimensions of all components are half of the dimensions of the previous one are classified as PS1-PS2-PS3. After the specimens were prepared, push-out tests were carried out in the load applicator located in ITU Civil Engineering Building Materials Laboratory to be applied to the web of steel beam. In the fourth section, the results of the force-slip values obtained by the experiment are examined. As a result of the experiment, specimens were modeled in the Abaqus program in the direction of the values obtained by using finite element model (FEM). These models were analyzed and compared with the experimental study, numerical verification of the experiment was made. The result of the force-slip graph obtained from the analysis results using the Abaqus program and the graphs of the test results are in agreement with each other. Thus, it can be concluded that size effect is the effect of composite beams. Consenquently, findings obtained from numerical and experimental studies show that the study is compatible with the hypothesis part. The shear connections of composite beam components exhibit a brittle fracture mechanism during fracture. This brittle fracture mechanism is accompanied by size effect. As a result of experimental and numerical analyzes, this brittle fracture type can be caused by crushing of the concrete part. And size effect is observed when it occurs in the form of the progress of micro and macro cracks formed in fracture of concrete. The size effect of the concrete was not clearly seen in the push-out test, which is a composite beam component, because there was no previous size effect analysis. However, in the present study, this situation has been uncovered and it has been revealed that improvements have to be made to the required standards.