Pendulum-type structure

For the damage identification a FE-model was built the box-girders were modeled with shell elements, the massive bridge ends with volumetric elements and the asphalt layer and non-structural parts with added masses. With regard to the supports at one of the intermediate pillars, there is a hinge the other supports are of the pendulum type. At these pendulum supports, the horizontal movement is somewhat restricted due to the reinforcement bars that cross the contact areas. 

Use of impact sled tests is the most common technique for determining the postcrash dynamic behavior of an aircraft occupant. The impact sled and target tracking facilities available at National Institute for Aviation Research (NIAR) were used to conduct a study on occupant responses in a crash environment. Parallel analysis capabilities, including a multibody dynamic model of the occupant and a finite element model of seat structures, have been developed. The analysis has been used to reasonably predict the Head Injury Criteria (HIC) as compart with the experimental impact sled tests for an occupant head impacting a panel. A nonlinear viscoelastic contact force model was shown to better predict the experimental data on the contact forces than the Hertzian models. Suitable values of the coefficients in the contact force model were obtained and the correlations between the coefficients, HIC, and maximum deformation of the front panel were determined. A non-sled test method of pendulum-type has been designed to determine the head injuries as well as the performance of each particular impact absorber. 

Surface viscosity has an important influence on the deformation of films and can also provide information about structure. Gaines [14] describes various methods of measuring this quantity. The damped torsion pendulum as developed by Langmuir and Schaefer [65] is probably the best device for making such measurements. Recent measurements of this type have been made by Buhaenko et al. [66]. Malcolm [67, 68] and Daniel and Hart [69] have carried out experiments which illustrate the important influence which viscosity has on the study of isotherms. 

The first pendulum (of inverted type, that is with its mass above and its spring below) has its mass essentially formed by the shell and by that part of the contained liquid (located in the lower part) which follows the tank in its oscillation. The second pendulum, linked to the first one in the upper part, has its mass formed by that part of the liquid (located in the upper part) which oscillates in an autonomous way relative to the shell. The recall forces for the two pendulums are, respectively, the elastic recall force of the support structure and the gravity force. 

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