An inertial macroelement for bridge abutments

Abstract

In recent years, the designers of long girder bridges in seismic areas have frequently opted for a continuous deck. One implication of this choice is that in many instances bridge abutments are called upon to carry large seismic forces, engaging the dynamic response of the soil–abutment system. To deal with this problem, this paper describes the formulation of a novel one-dimensional, inertial macroelement for simulating the dynamic behaviour of bridge abutments. The non-linear force–displacement relationship is characterised by a multi-surface plasticity model using a rigorous thermodynamic approach. The plastic response of the model is bounded by the ultimate capacity of the soil–abutment system that includes dissymmetry of the soil response in active and passive loading directions, while inertial effects transferred by the near-field approach embankment are simulated through appropriate participating masses in the macroelement formulation. The paper describes a straightforward calibration procedure of the proposed macroelement for horizontal, longitudinal loading of the abutment. The macroelement has been incorporated into a simplified, global, finite-element model of a multi-span girder bridge and validated through comparisons with results from a full three-dimensional (3D) dynamic time domain analysis under seismic loading. The inertial macroelement predictions of abutment deformations, axial deck loads and pier reaction forces are in very good agreement with the 3D soil–structure interaction model, and are achieved at much lower computational costs. The proposed inertial macroelement represents a significant improvement over existing simplified models based on linear response of the soil–abutment system.

On the seismic performance of straight integral abutment bridges: From advanced numerical modelling to a practice‐oriented analysis method

“…In particular, these latter modes represent the first and second modes of the approach embankments in the longitudinal direction, whose modal properties are nearly coincident to the ones obtained with the 3D model. As it was demonstrated in recent and less recent studies, 38,39,48 the embankment modes strongly affect the structural performance because they are related to the flexural behaviour of the abutments (see Figure 6).…”

“…4 The measurements provided by Werner et al 24 on two highway overcrossings located in California (Painter Street Overcrossing and the Meloland Road Overcrossing) during strong motion were taken as the reference for many numerical studies. [24][25][26][27][28][29][30][31][32][33][34][35][36] All these studies, as well as other advanced numerical investigations carried out by Elgamal et al, 37 Gorini and Callisto 38 and Gorini et al 39 on different soil-bridge layouts pointed out the central role played by the approach embankments on the overall dynamic response. Simplified analytical and numerical models 32,[40][41][42] have been proposed through the years for a direct consideration in the seismic design of bridges of the frequency-dependent inertial forces developing in the embankments.…”

“…The focus is on the longitudinal response of the integral bridge as the one more affected by dynamic soil-structure interaction. [37][38][39]48 The dynamic perturbation for the coupled soil-bridge models therefore consists of a purely longitudinal seismic motion.…”

“…on two highway overcrossings located in California (Painter Street Overcrossing and the Meloland Road Overcrossing) during strong motion were taken as the reference for many numerical studies 24–36 . All these studies, as well as other advanced numerical investigations carried out by Elgamal et al., 37 Gorini and Callisto 38 and Gorini et al 39 . on different soil‐bridge layouts pointed out the central role played by the approach embankments on the overall dynamic response.…”

“…The construction sequence described in Section 2.2 was implemented in OpenSees and Sap2000. The reader can refer to Gallese et al39 for a detailed description of the strategy used in the 3D model. As per the ROM, as already said, in OpenSees the construction stages are implemented in the model by means of elements whose parameters are progressively updated (e.g.…”