1,721,341 research outputs found
Nonlinear phased analysis of reinforced concrete tunnels under fire exposure
No full textFire analysis of precast segmental tunnels involves several problems, mainly related to the soil-structure interaction during fire exposure, coupled with material degradation. Temperature increase in the tunnel is the cause of thermal expansion of the lining, which is resisted by the soil pressure. Furthermore, the increase of temperature in the lining leads to severe damage to the reinforced concrete precast elements, which can jeopardise structural safety.This problem has been analysed using an ideal case of a precast segmental tunnel excavated in a stratified soil. The analysis has been conducted with a commercial nonlinear FE element code. Initially, excavation of the tunnel was modelled in order to predict stresses in the lining due to the soil pressure and eventually fire exposure was considered. The reinforced concrete lining was modelled with a crack model in order to simulate the actual behaviour.Results show the importance of considering the interaction with the soil and the degradation of the concrete lining
Caratteristiche meccaniche del Botticino Classico.
No full textBotticino Classico is analysed herein by means of a physical – mechanical characterisation through conventional and non conventional laboratory tests. In particular, uni-axial tests were carried out by adopting a close loop deformation control. These tests are suitable not only for the determination of the modulus of rupture but also for the knowledge of the post-peak behaviour. The tests have been performed by adopting specimens with different orientation respect to the sedimentation layers: the results show a mechanical uniformity of the material
Confronto tra le caratteristiche meccaniche di diversi livelli di estrazione del Botticino Classico.
No full text
Design Aspects on Steel Fiber Reinforced Concrete Pavements
No full textA numerical study on the fracture behavior of Steel Fiber Reinforced Concrete slabs on grade for industrial pavements is presented. Finite element analyses have been carried out by using
a commercial finite element code where user subroutines based on nonlinear fracture mechanics have been implemented to describe the progressive cracking behavior of SFRC.
The model is capable of simulating both primary and secondary cracks when they occur in concrete and it has been validated by comparing numerical predictions with experimental observations of full-scale tests on slabs on elastic subgrade under point loads in different positions. A real pavement with contraction or construction joints has been numerically simulated to investigate the stress and the strain fields for the most significant positions of
point loads
Flexural strength and notch sensitivity in natural building stones: Carrara marble and Dionysos marble.
No full textThe tensile behaviour of marble at failure is analysed. A series of monotonic and cyclic bending tests were carried out in the laboratory on geometrically similar specimens of different size. The strain distribution was monitored with strain gauges and laser interferometry techniques. Three and four point bending configuration were considered. It is shown that cyclic loads in a three point bending configuration induce permanent tensile deformation
Evaluation of the bearing capacity of fiber reinforced concrete sections under fire exposure
No full textAim of the paper is the evaluation of the bearing capacity of fiber reinforced concrete (FRC) sections, without any traditional steel reinforcement, subjected to different values of the fire duration. At this purpose, bending moment (M)-axial force (N) interaction envelopes are defined, through an analytical model based on the direct integration of the hot or residual mechanical properties of the material, throughout the member cross section. Finally, a parametric survey, specifically related to tunnel segments, with different geometries and FRC materials allows highlighting the worst (or better) scenarios
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