A parametric study on the axial behaviour of elastomeric isolators in multi-span bridges subjected to horizontal seismic excitations

Abstract

This paper investigates the potential tensile loads and buckling effects on rubber-steel laminated bearings on bridges. These isolation bearings are typically used to support the deck on the piers and the abutments and reduce the effects of seismic loads and thermal effects on bridges. When positive means of fixing of the bearings to the deck and substructures are provided using bolts, the isolators are exposed to the possibility of tensile loads that may not meet the code limits. The uplift potential is increased when the bearings are placed eccentrically with respect to the pier axis such as in multi-span simply supported bridge decks. This particular isolator configuration may also result in excessive compressive loads, leading to bearing buckling or in the attainment of other unfavourable limit states for the bearings. In this paper, an extended computer-aided study is conducted on typical isolated bridge systems with multi-span simply-supported deck spans, showing that elastomeric bearings might undergo tensile stresses or exhibit buckling effects under certain design situations. It is shown that these unfavourable conditions can be avoided with the rational design of the bearing properties and in particular of the shape factor, which is the geometrical parameter controlling the axial bearing stiffness and capacity for a 123Bull Earthquake Eng (2016) 14:1285-1310 DOI 10.1007 given shear stiffness. Alternatively, the unfavourable conditions could be reduced by reducing the flexural stiffness of the continuity slab.

Investigating the Performance of Isolation Systems in Improving the Seismic Behavior of Urban Bridges. A Case Study on the Hesarak Bridge

“…The properties of the isolators which need to be determined to complete the design include lead core diameter, isolator diameter, thickness and number of the rubber layers, thickness and number of steel reinforcing plates. Equations (5) through (9) have been used to calculate the LRB properties.…”

“…Lead plugs are inserted into these holes to add damping to the isolation system [8]. The occurrence of tensile forces in isolation bearings has been reported in many reconnaissance surveys such as those following the 2011 Tohoku earthquake and also in experimental shaking-table tests on isolated structures [9].…”

Seismic upgrading of isolated bridges with SF-ED devices: Analytical study validated by shaking table testing

“…The application concept of the proposed additional devices for seismic energy dissipation, [12][13][14][15][16][17], along with some devices for limitation of large displacements, has been introduced. Lately, the developments in this innovative earthquake engineering field have been intensified with complementary studies of various specific related phenomena, including pounding effect [18], axial behaviour of elastomeric isolators [19], semi-active dampers [20], as well as with studies devoted to qualitative upgrading of present technologies. Seismic design regulations of seismically isolated bridges are gradually being introduced, and are permanently upgraded [21], and implemented in many countries located in seismically active regions [22].…”

Seismic upgrading of bridges isolated with SF-ED devices: Large-scale model testing on shaking table

“…The concept of applying the proposed additional devices for seismic energy dissipation, [12][13][14][20][21][22], along with some devices for limitation of large displacements, has been introduced. Lately, the developments in this innovative earthquake engineering field have been intensified with complementary studies of various specific related phenomena, including the pounding effect [15], axial behaviour of elastomeric isolators [16], semi-active dampers [17], as well as with studies devoted to qualitative upgrading of present technologies. Seismic design regulations for seismically isolated bridges have been gradually introduced and are continuously upgraded [18] and implemented in many countries located in seismically active regions [19].…”