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Nowadays, the focus of reliability-based validation of the post-fire bearing capacity of structures is on multi-storey buildings used for dwellings or offices due to the high human impact related to the use of the building. Research has been done using first order reliability-based methods to assess the behaviour of simple single isostatic concrete slabs, which is commonly used in this type of buildings. But, the knowledge of the post-fire behaviour of structures is also of high economic importance for industry and companies. Today, a lack of knowledge on the behaviour of single storey framed hyper static steel structures exist. The main goal of this research is to simulate the consequences of natural fire on industrial steel or composite structures, to compare the simulations against results available in the literature and to provide a method to evaluate the remaining structural load-bearing capacity. With only a limited amount of data, using numerical techniques, the temperature distribution in enclosures can be known and, from that, the structural response be predicted. Furthermore, it is known that the failure mode, in case of fire, of this kind of framed structures is always determined by the moment resisting beam-column nodes. A force-based method directly delivers the needed information for a framework and can be easily arranged in a statistical format. With the results of the theoretical analysis, the residual bearing capacity of the considered structure can be assessed after exposure to the fire.

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Reinforced concrete deep beams are one of the most important elements used in civil engineering structures, not only because they are able to resist high compressive forces, but also because they can be used to increase the resistance of a structure under a dynamic loading. However, given that they are not exempt from degradation provoked by aging or unexpected loading, they tend to decrease in quality and resistance. To avoid this, Fiber Reinforced Polymers (FRP) appeared as one of the methods used for the strengthening of the deep beams.
The main goal of this thesis is to introduce and define the fundamental theory of the Five-Spring model, developed by Mihaylov et al. (2015), and extend it to deep beams strengthened with FRP wraps. The extended Five-spring model will account the effect of the FRP wraps depending on the following parameters: (1) the bond-slip relationship of the FRP strip to the concrete interface; (2) the process of debonding of the FRP strip; (3) the angle of the critical shear crack ; (4) the ratio between the depth of the FRP strip and the depth of the beam; (5) the wrapping scheme ; (6) the position of the strip with respect to the critical shear crack and (7) the shape of the critical shear crack. To account for the bond-slip model and the process of debonding, models developed by Lu et al. (2005) and Chen et al. (2012) were selected, yet in a simple manner. The shape of the critical shear crack on the other side was accounted by analyzing what is the shape that produce the most accurate response of the process of debonding. Once the influence of the seven parameters was considered, they were implemented one by one in the Matlab code to validate this extended Five-spring model with experimental data.
The extended Five-spring model was validated against test results from the literature and concluded that FRP has a positive effect in the pre-and-post peak behavior of deep beams. However, it was also observed that the accuracy of the predicted results would increase when more parameters, such as the concrete crushing around the loading plate, supports settlement or debonding of the FRP , were considered.

Deep beams --- Kinematics based modelling --- Reinforced concrete --- Wrapping --- Fiber reinforced polymers --- FRP --- Shear behaviour --- Ultimate load --- Displacement --- polymers --- Ingénierie, informatique & technologie > Ingénierie civile

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This thesis aims to investigate the bond strength between 3D printed concrete and diverse types of reinforcement. The application of 3D printed concrete within the construction industry is still in its initial stages as there are still many challenges yet to be solved. One of these challenges is the successful implementation of reinforcement in 3D printed concrete. Due to its anisotropy caused by the layered structure, it exhibits a completely different behaviour than conventionally casted concrete. This research is extremely interesting to gain new crucial insights on the implementation of 3D printed concrete as a construction method. This new technique has the potential to drastically change the future of the construction industry. It enables complex geometries and precise customisation; this can lead to more durable and efficient structures. To carry out this research, specimens were made from 3D printed concrete and conventional casted concrete that were subjected to a double beam end test. Three diverse types of reinforcement were used. First, an open cord wire was used, then also a barbed wire and, for reference, a conventional ribbed reinforcement bar. The specimens were dimensioned so that when subjected to this test setup, they would fail due to the debound between the concrete and the reinforcement. The advantage of this test setup is that it uses bending instead of direct pull on the reinforcement. In addition, the location of the tension reinforcement, at the bottom of the specimen, is also much closer to the actual situations on which concrete structures are designed. The objective of these tests was to provide more insight on how the reinforcement bars behave in 3D printed concrete. With the open cord wire, this was quickly apparent; this wire was far too fragile to be implemented in concrete structures. In contrast, the barbed wire brought promising results. Because the spines of the barbed wire created a mechanical lock, a greater bond strength was achieved. It also ensured that the different layers of the 3D printed concrete were better bonded. The forces achieved did not differ much from specimens made from conventionally casted concrete. These promising results regarding the barbed wire as a reinforcement bar offer interesting perspectives for future further research. Future research could focus on further optimising this technique or exploring new possibilities in using barbed wire as reinforcement.

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