Shear Characteristic Changes in Blended Rubber of Elastomeric Bearings due to Aging

Rubber bearings are widely used for seismic retrofit of bridges because they reduce the seismic force by making the vibration period of the bridge longer and distributing the seismic force to all the piers. However, they have the disadvantage of being easily aged compared to steel bearings as well as having variations in the shear stiffness. The shear characteristic changes in the blended rubber for the rubber bearings were analyzed, specifically, the aging accelerated by heat. The higher the aging temperature and longer the exposure time, the greater is the maximum stress and strain at that time, and the greater is the shear stiffness. This implies that the seismic performance gradually deteriorates due to aging as the service period becomes longer. This can provide the basis for the mechanical model of the aging bearing.

Assessment of the Suitability of Elastomeric Bearings Modeling Using the Hyperelasticity and the Finite Element Method

The paper presents modeling of bridge elastomeric bearings using large deformation theory and hyperelastic constitutive relations. In this work, the simplest neo-Hookean model was compared with the Yeoh model. The parameters of the models were determined from the elastomer uniaxial tensile test and then verified with the results from experimental bearing compression tests. For verification, bearing compression tests were modeled and executed using the finite element method (FEM) in ABAQUS software. Additionally, the parameters of the constitutive models were determined using the inverse analysis method, for which the simulation results were as close as possible to those recorded during the experimental tests. The overall assessment of the suitability of elastomer bearings modeling with neo-Hookean and Yeoh hyperelasticity models is presented in detail.

Modeling and analysis of a prestressed girder bridge prior to diagnostic load testing

Progressive deterioration is a problem that affects road infrastructure, especially bridges. This requires the development of methods for its adequate detection and revision, one of them being load testing. Within load testing, finite element analysis (FEA) models provide initial information to understand the behavior of a structure and plan accordingly, which represents a fundamental step towards a precise structural evaluation of a bridge. This study focused on the modeling and analysis of the static response of the bridge over the river Lili in Cali, Colombia, a prestressed girder bridge programmed to undergo a diagnostic load test. A linear FEA model was created with information from a manual survey and from other bridges’ plans designed and built under the regulations in force at the time. Due to the absence of plans and design specifications for the bridge, variations were applied to certain model parameters (stiffness of diaphragms and elastomeric bearings), to quantify their effect on the overall behavior of the bridge. The analysis included obtaining the critical position for the design vehicles, the transversal distribution of stresses and determining the influence of the variation parameters in the response of the structure. Results showed that the critical combinations for bending moment and shear were when the loads were the closest to the exterior girders, being these elements the most affected. The variation on the modulus of elasticity for the diaphragms and the stiffness of the elastomeric bearings did not significantly influence the results for bending moment and shear, nor the critical position. Girder distribution factors (GDF) from the model were compared to previous research, finding similarities in shape and value with other FEA models and experimental results. Finally, an instrumentation plan focused on the girders of the bridge was proposed based on the zones where the maximum effects are expected. The findings in this study show how linear FEA models provide initial but relevant information regarding the critical position of design vehicles, the distribution of stresses and the expected values for bending moment and shear under design loads.