Resumo em Inglês:

Abstract Welding procedures for repairing corroded tubular structures are commonly used; however, composite material repairs are becoming popular since they do not use heat sources that might cause accidents. This paper provides a detailed description of the CFRP patch repair application in steel tubular members with a circular perforation originated from a prolonged corrosion process. The results of experimental tests on mid-scale unrepaired damaged and repaired steel tubes are reported. The predictions of the maximum loads recovered from a proposed numerical model lie close to the experimental observed values, justifying its usage for analysis of repaired tubular structures with circular cutouts when subjected to axial compression. Compared to unrepaired perforated tubes, the experimental results demonstrate a substantial strength recovery for repaired tubes. The value of this research for the oil and gas industry is that it demonstrates the feasibility of this kind of repair, which means reduced risk to the production unit and a shorter repair period.

Resumo em Inglês:

Abstract Based on the theory of single-phase elastic medium and unsaturated porous medium, the vibration isolation effect of composite multilayer wave impeding block (WIB) in the unsaturated ground under an underground dynamic load is investigated. The results show that the best vibration isolation effect can be obtained by designing the wave impedance ratio between the composite multilayer WIB and unsaturated ground. The composite multilayer WIB improves the vibration-damping bandwidth compared with the homogeneous WIB. The vibration isolation effect is better the closer the embedded depth of the composite multilayer WIB is to the vibration source, and its vibration isolation effect increases significantly with the increase of thickness, but when the thickness of the WIB exceeds a certain critical thickness, its vibration isolation effect decreases with the increase of thickness. Soil saturation has a significant effect on the vibration isolation effect of composite multilayer WIB in the unsaturated ground, and the composite multilayer WIB can achieve a better vibration isolation effect at low saturation.

Resumo em Inglês:

Abstract Metaconcrete is a newly manmade concrete where traditional aggregates are partially replaced by resonant aggregates. The metaconcrete slab can attenuate vibration in the specific frequency bandgap which are created by the locally resonant aggregates. To enhance the attenuation performance of metaconcrete slab, a dual-resonant aggregate was designed and embedded into the metaconcrete slab. Firstly, a mass-in-(mass-in-mass) analytical model is used to predict the bandgap characteristics of dual-resonant aggregates metaconcrete. Then, eigenfrequency investigation is conducted to acquire the dispersion curve of the periodic unit cell by using finite element software COMSOL Multiphysics. The effects of the mass and stiffness ratios parameters on the characteristics of bandgap are studied. The frequency responses of the dual-resonant aggregates metaconcrete reveal that the dual-resonant aggregates metaconcrete slab can acquire vibration wave mitigation in two designed frequency bands. The results offer a base for the optimal design of the metaconcrete slab for structural protections resist vibration loading.

Resumo em Inglês:

Abstract In typical dynamic soil-structure interaction (SSI) problems, the dynamic response a structure can be affected by the existence of some nearby structures, which is sometimes referred to as the dynamic structure-soil-structure interaction (SSSI). This effect is especially important in the earthquake engineering design of adjacent nuclear power plants, as the safety risk is relatively high. However, the current understanding on the SSSI of nuclear power plants is still insufficient. In this work, we use the finite element method to investigate the SSSI of two nuclear power plants located at a specific distance under earthquake excitation. Four nuclear-power-plant-soil systems are designed to account for the SSI and SSSI respectively, where the soil properties are obtained from drilling data. The effect of the SSSI on the nuclear power plants is studied by comparing the dynamic responses of four nuclear power plants-soil systems in vertical and horizontal directions, in which both layered soils and local weak interlayer soils are considered. The results of numerical study show that the presence of one nuclear power plant has a favorable effect on the seismic response of an adjacent nuclear power plant, such as reducing the displacement response, but this effect is limited. In addition, the SSSI effect is related to not only the soil properties, but also the direction of ground motion. Furthermore, the existence of soft soil layers complicates the SSSI effect. The results provide important insights for the construction and expansion of nuclear power plants.

Resumo em Inglês:

Abstract This paper presents the behavior of steel-concrete composite beams with fire protection using the finite element software ABAQUS. An extensive parametric study was carried out to verify the influence of the axial and rotational restraint stiffness, the influence of the spans and the influence of the variation of the fire protection coating, topic with few studies by other authors. The focus of this paper was to verify the axial forces on the supports to study the influence of these forces on the surrounding elements: columns and connections. The study shows that axial and rotational constraints have an important influence on the beams. The values of axial forces are proportionally greater as the beam span is increased. Also verified was that the beam behavior does not change with the variation of the fire protection coating. Finally, the study brings a new approach to the importance of investigating the forces of interaction between beams and columns, as theses forces can lead to unsafe design because the compressive forces in the interaction with the columns and the tensile forces in the catenary phase in connections.