PSI - Issue 10

C.B. Demakos et al. / Procedia Structural Integrity 10 (2018) 148–154 C.B. Ddemakos et al. / Structural Integrity Procedia 00 (2018) 000 – 000

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volume minimization. The specimen tested is shown in Figs.1(a,b). The cement frame section was 8 mm thick and 10 cm wide. The cement mortar was tested and found to have an axial compression strength of about 50 MPa. The specimen was located inside a box, which was filled with sand over the arch to load it uniformly in bending. Then, a force was applied over the sand surface, as distributed loading, by the piston of the bending machine through a wood plate, as Figs.1(b,c) illustrates. Sets of experimental data concerning the loading and displacement were recorded through a data acquisition system and plotted in curves providing the failure behavior of arches.

(a)

(b)

(c) Fig 1. (a) front view of test specimen; (b) specimen inside the box under the bending piston machine; (c) the bending machine with test specimen.

3. Modeling of structure and analysis results.

The specimens tested above were modeled to find numerical results and compared them to experimental ones. The geometry of model applied is the same as that used in tests. The constituent material was cement mortar with its axial compression strength of about 50 MPa. Two levels of simulation were executed. First of all, linear finite elements were used to model the curved frame (Fig.2a). At the second stage of simulation, a shell elements procedure with non-linear analysis was applied to model the structure, as is shown in Fig.2b. The loading of arch structure consists of two parts. One part is the self-weight of sand inside the box and the second one is the loading from the bending machine. In order to simulate the loading of sand inside the box, the weight of a sand column (Fig.3a) was considered above each element, calculated and applied to this element providing a total loading variation, as Fig.3b shows. Two scenarios for loading distributions were investigated. One concerns with the uniformly varied loading applied to the surface of curved frame at gravity direction as Fig.4a illustrates. In the second scenario, the uniform loading was applied perpendicular to the surface of curved frame, as is shown in Fig.4b. The last scenario could be con sidered in loading case of tunnels in geotechnical works, where over-existing ground layers create such a frictionless pressure on concrete arches.