Resumo em Inglês:

Abstract This theoretical and experimental work deals with the power law evolution followed by the natural frequency f0 of a hanging, heavy and flexible plate as a function of its length L. When the plate length L is small enough, it behaves as an elastic plate whose weight can be neglected: it is well known that f0 evolves as a function of L−2. Nevertheless, when the plate length is increased, the mass has to be taken into account, and the previous evolution is not valid anymore. In the case of long elastic plates, f0∼L−1/2, just like hanging chains. These two power laws depend on the ratio L/Lc, where Lc is a critical length that writes as a function of the plate mass and the flexural rigidity. After the theory is developed and the plate motion equation is solved using a Galerkin expansion, we find the theoretical evolution of the natural frequencies as a function of length. Experiments were performed with three distinct materials and the natural frequency was systematically measured for a wide length interval. Our data points fit the above-mentioned limit cases and the intermediate case was calculated thanks to our Galerkin expansion.

Resumo em Inglês:

Abstract This paper investigates the behavior of a new form of V-shaped shear connector. The assessment of the proposed connector’s performance is conducted through an experimental work of fourteen push-out tests. The results show that the developed V-shaped shear connector is able to transfer higher shear load than the conventional shear connectors. In addition, its behavior is considered as ductile. Geometrical parameters of the connector are studied to observe their influence on its behavior. The experimental outcomes show that changing the length, width, and thickness of the connector significantly affects its ultimate strength while the connector's ductile behavior is preserved. Furthermore, the work proves that neither creating holes nor adding transverse reinforcement to the connector has significant effect on shear resistance and that the uplift-displacement of the connector is improved. A comprehensive comparison between the proposed shear connector and commonly used shear connectors is executed. Based on the experimental results, an empirical equation is suggested to predict the load capacity of the connector.

Resumo em Inglês:

Abstract The jet morphology of square and circular cross-section shaped charge with same inscribed circle diameter were observed by conducting an X-ray experiment. Depth-of-penetration tests at standoffs 80 and 160 mm were also carried out. The jet formation was studied by using AUTODYN software. The results showed that the jet of square cross-section shaped charge consists of a condensed part and a non-condensed part. The condensed part has similar characteristics to the corresponding part of circular cross-section shaped charge. And the non-condensed part is distributed at the jet tail. The non-condensed part consists of a main fluid moving along the axis and four off-axis fluids with off-axis velocity along the symmetry plane. The non-condensing of jet reduces the penetration depth of square cross-section shaped charge, the decreasing rate increased from 2.67% to 17.3% when the standoff is increased from 80 mm to 160 mm. When the inscribed circle diameter of the charge cross-section increases to 67.2 mm (1.2 times of 56 mm) and the liner structure remains the same, the square cross-section shaped charge will form a cohesive jet.

Resumo em Inglês:

Abstract In the present work the performance of finite element formulations with different reduced integration strategies is evaluated for Contact Mechanics applications. One-point quadrature and selective reduced integration are utilized here using hourglass control to suppress volumetric and shear locking for materials with incompressible plastic behavior and bending-dominated problems. A corotational formulation is adopted to deal with physically and geometrically nonlinear analysis and the generalized-α method is employed for time integration in the nonlinear dynamic range. The contact formulation is based on the penalty method, where the classical Coulomb’s law is used considering a convected coordinate system for three-dimensional friction with large deformation and finite sliding. Contact problems involving deformable and rigid bodies, as well as static and dynamic analysis, are investigated and results are analyzed considering the different underintegration formulations proposed here.

Resumo em Inglês:

Abstract In this paper, effect of uncertainty of fastening system properties on the wheel/rail dynamic force (WRDF) was investigated. For this purpose, two deterministic and epistemic models of vehicle/track interaction were developed, using the finite element method. Validity of the results obtained from the models was shown through comparison between the model results and those obtained from field tests. The effects of uncertainty of fastening system properties on the WRDF in different axle loads, vehicle speeds, rail irregularities and various track maintenance conditions were derived through probability and sensitivity analyses. Using the results obtained, some contours were developed to obtain the amplification of WRDF (due the uncertainty of fastening system properties) as a function of vehicle axle load, vehicle speed and track maintenance conditions.

Resumo em Inglês:

Abstract The aim of the current project is to carry out the FEA framework for predicting the flexural strength of notched foam concrete tested under three-point bending following the conducted experimental set-up. The investigated testing series have a variation of notch size opening in the foamed concrete beam. The Traction-separation relationship was used as a constitutive model to incorporate independent material properties and used in the modelling framework. Modelling techniques of 2D XFEM and CZM were adopted and later expanded to 3D XFEM models. Good agreement was found between the predicted structure response and experimental observation for all the investigated models. Crack was initiated at the crack tip and propagated to the beam edge under the applied load. It was found that the average discrepancies below 20% were found within XFEM techniques. Less agreement was found using the CZM models, partly due to the simplification of the adopted failure path. The modelling framework implemented in this project is potentially used as a predictive tool in estimating the flexural strength of the concrete beam with notches.

Resumo em Inglês:

Abstract Reinforced concrete thin walls buildings have become one of the most common alternatives for housing construction in Colombia. However, some studies on this system have reported that walls have a limited deformation capacity and may suffer brittle failures. In this paper, a numerical model developed in OpenSees was used to represent the behavior of thin and slender reinforced concrete walls. The model was evaluated and fitted with the experimental response of two representative walls of this type of construction in high seismic hazard zone, in addition to the results of cyclic tests of other investigations with walls of similar characteristics. The experimental response of the walls indicated that, despite reaching a moderate deformation capacity, for the 1% drift limit, the level of damage was severe and lost 77% and 67% of their initial stiffness, respectively, which confirms that their performance is limited and provides a warning that the design practices may be insufficient. The numerical simulation correlated well with the experimental response in terms of displacement capacity, strength, and hysteric behavior.

Resumo em Inglês:

Abstract A ballistic projectile launching device was used to study the penetration behaviors of tungsten alloy spherical fragments of various diameters into carbon fiber composite target plates of different thicknesses. Based on the ballistic test results, we obtained the relationship between ultimate penetration velocity, target plate thickness, and fragment diameter as well as the relationship between the fragment penetration energy and fragment incident velocity. Using dimensional analysis, we obtained a formula relating the incident fragment velocity and the fragment penetration energy, which showed good agreement with the experimental values. We also analyzed the main fracture mode and the energy absorption mechanism of the carbon composite target plate under high-velocity impacts of tungsten alloy spheres and investigated the experimental damage modes of the target plate at different fragment velocities during the ballistic impact.

Resumo em Inglês:

Abstract The current investigation focuses on the results of an experimental investigation of Square-plan-shape and Remodel-triangle-shape building model’s varied interference conditions between duplicate building models of 1:300 scale (at 100% blockage) on wind-induced pressure and base moments at fixed 10% of the height of the instrumented model. Under current working conditions, the study concludes that -1 > Interference Factor > 1 as experienced by the Remodel-triangle-shape model results in reduced performance of the instrumented model as opposed to the Square-plan-shape model. Front-to-Front interference condition of Remodel-triangle-shape model has the best overall performance in along-wind and crosswind directions, whereas Front-to-Back interference condition of Remodel-triangle-shape model has the best torsional performance. Back-to-Back interference of a Remodel-triangle-shape model should be avoided because the orientation of duplicate models attracts the most overturning moments in both the along-wind and crosswind directions of all interference conditions investigated in this study.

Resumo em Inglês:

Abstract The sheet metals are prone to large plastic deformation during forming processes. The study purpose is to investigate 1050A aluminum sheets thermomechanical behavior with ductile damage. A modified Swift model coupled to isotropic ductile damage and thermal effects was used. The forming parameters are introduced using Swift model coefficients and Erichsen index. An inverse identification procedure is applied to non-homogeneous Erichsen test results. Bulge test is then used to validate the identified parameters. Erichsen test (Punch force vs displacement) results were obtained by experimental testing and simulation to build the objective function. Aluminum 1050A plasticity flow parameters and ductile damage variables were identified using a part of Erichsen test results. The remaining part of Erichsen test and bulge test results were used for validation. The numerical approach allowed the detection of failure zones with respect to thermal gradient induced by heat exchange. Within the isothermal condition, equivalent stresses and strains for 1050A Aluminum were obtained by simulations and experimental data.