A popular water pipe system used in many countries is one formed by prestressed cylindrical concrete pipes (PCCPs) formed by identical precast moduli joined together in situ. This technology was and still is quite popular in many water supply systems internationally. This technology was mainly selected at the time due to its cost-based comparative advantage. However, over the years, numerous incidents of structural failures have been reported for this type of pipeline, causing, in some cases, serious disruption of the water supply. This study summarizes the results of an experimental investigation on ten (10) PCCP specimens taken from an existing water pipeline with the objective of investigating their bearing capacity under either three-edge bending or internal hydraulic pressure loads. Moreover, there is a need to check the capability of specific retrofitting/strengthening schemes to upgrade this bearing capacity and thus enhance the operational period. Provided that the prestressing wires are fully active according to design specifications, the original specimen performed satisfactorily for the set internal hydraulic pressure limit of 8.5 bar. Specimens retrofitted with either internal or external CFRP or RC jacketing performed satisfactorily for internal hydraulic pressure levels well above this 8.5 bar limit. A critical factor is, as expected, the loss of prestress.

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Fiber-reinforced polymers (FRP) are rapidly gaining acceptance from the construction sector due to their large effectiveness. They are mainly used as confining reinforcement for concrete columns and as tensile reinforcement for concrete beams, columns and slabs. FRPs are already used to a large extent for applications such as bridges and parking lots, where elevated temperatures are not the main risk. Their increasing use as structural reinforcement is hampered by the concern related to their behavior at elevated temperatures as the relevant research is deficient. Thanks to the significant advantage of FRPs’ mechanical properties, further investigation into the influence of heating on their mechanical behavior may solve many doubts. The present study examines the influence of temperatures, ranging among 50, 100 and 250 °C, on the tensile strength of FRP laminates with carbon fibers (CFRP). In addition, the resistance of CFRP specimens to low-cycle thermal loading at the temperatures of 50, 100 and 250 °C under constant tensile load was investigated. The experiments were carried out in the laboratory of Experimental Strength of Materials and Structures of Aristotle University of Thessaloniki.

A number of unreinforced masonry walls of prototype dimensions were built at the laboratory of Strength of Materials and Structures of Aristotle University using prototype masonry units together with mortars having such a composition that can be characterized as low strength mortars. The in-plane and out-of-plane behaviour of such structural elements is of considerable interest as existing structures include this type of structural components. During the construction of these piers samples of the mortars used in the construction were taken. After a curing period these samples were subjected to two distinct tests, namely axial compression and four-point bending. Similarly, from the basic material of the masonry units, either clay or natural stone, prismatic specimens were formed which were also subjected to either axial compression or four point flexure. Next, a number of numerical simulations were performed utilizing all the information of the geometry and material characteristics of the mortar or masonry material specimens in order to replicate numerically the axial compression and four point flexure tests which were performed in the laboratory. The numerically simulated behavior resembles the measured brittle load-deformation response and the observed actual damage at the end of the tests. Using back analysis procedures a reasonable correlation can also be achieved between the measured value of the ultimate load and the corresponding value predicted by this type of numerical simulation. 345 COMPDYN 2019 7 th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering M. Papadrakakis, M. Fragiadakis (eds.

COMPDYN 2019 7 th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering M. Papadrakakis, M. Fragiadakis (eds.

These numerical simulations employed all the geometric and mechanical characteristics of the tested specimen. In all these specimens the reinforcing details prohibited the appearance of shear failure modes. Therefore, this study focuses on the flexural response and the numerical simulation of the bending mode of failure at either the columns or the beams forming each sub-assembly. Towards this objective the features of commercial software were utilized. The observed behaviour is portrayed in terms of horizontal load versus horizontal displacement cyclic response as well as bending moment cyclic response that develops et the beams and columns forming this RC joint. These bending moment values are compared with the corresponding ultimate bending moment values derived from the relevant cross-sectional detailing as well as from the measured concrete and steel material properties. From this comparison the observed cracking of the beams near the RC joint can be explained. The used 2-D and 3-D numerical simulations of the tested RC joint were successful up to a point to represent the observed flexural non-linear response of this RC structural sub-assembly. The used 3-D numerical simulation, although more complex than the corresponding 2-D numerical simulation, produces numerical predictions that are in better agreement with the observed maximum horizontal load and therefore ultimate bending moment capacity. By comparing the numerical results with the corresponding experimental measurements the validity of the employed numerical simulation is validated. 225 COMPDYN 2019 7 th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering M. Papadrakakis, M. Fragiadakis (eds.

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