Abstract
Abstract Precast concrete girders on bearing pads are subjected to instability depending on several variables such as span length, initial imperfections and bearing pads behavior. On this paper, numerical models are developed in order to assess the instability limit loads and the rotational stiffnesses of the pads in many combinations of span length, cross section of the girder and lateral sweep. The lift off phenomenon is considered in each analysis by a bearing pad model composed by springs with compression only behavior, with good results in comparison with the experimental values of the technical literature. The increase in spans and initial imperfections causes a decrease in the rollover limit load. The lift off effect is aggravated as the lateral eccentricities increase. In the analyzed combinations, the reduction of the rotational stiffness is about 37% for the critical situation, which span length about 40 m and lateral sweep of L/300, with loss of contact between 50% and 60%.
Highlights
There exist various reports concerning the collapse of precast beams, which were supported on neoprene bearing pads (OESTERLE et al.[1]; BAIRÁN; CLADERA [2])
The present study looked at creating models of beams on elastomeric bearing pads for beam section combinations, spans and eccentricities, as a means to obtain information pertinent to lateral displacements on beams that result from a concentrated load applied to the middle of the span
Based on results obtained from parametric studies the following conclusions are drawn: a) Comparing the two experimental studies: Hurff [8] and Consolazio, Hamilton and Beery [3], the model of beam constituted on solid elements and supported on a simplified pad model, provided adequate values for rotation and lateral displacement in the middle of the span
Summary
There exist various reports concerning the collapse of precast beams, which were supported on neoprene bearing pads (OESTERLE et al.[1]; BAIRÁN; CLADERA [2]). Few numerical studies have been performed to represent the behavior of long beams under rollover failure, when only supported on neoprene bearing pads (KRAHL; CARRAZEDO; EL DEBS [5]; LEE [6]; CARDOSO; LIMA [7]) This field of research requires greater investigation in the field of experiment, as well as numerical, in order that recommendations can be established. Highlighted here is that faced with various accidents that have been reported, until the present moment, there does not exist any type of normative code that establishes recommendations for this stage of construction In this context, the present study aims at numerically analyzing the variation in effective stiffness of the elastomeric bearing pads, under precast beams, for the limit load of lateral instability. The length of the beam, the cross section geometry, the effects of initial lateral imperfections (eccentricity), along with the characteristics of the elastomeric bearing pads are all considered as the principal variables
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