Abstract
A study of the sensitivity of bridge response to changes in non-geometric parameters was carried out using mainly the El Centro 1940 N-S earthquake component. The response of bridge decks supported on elastomeric or a combination of elastomeric and lead-rubber bearings is computed. The effects of variations in the following parameters on response were studied; a) a range of bearing properties, b) a range of abutment stiffnesses and abutment weights, c) different earthquake records and d) the effect of seismic waves propagating at various velocities and angles of attack with respect to the bridge centreline.
Highlights
The authors have described the influence that geometric factors such as pier heights and the number of spans [1] have on the seismic response of bridges mounted on elastomeric bearings or a combination of elastomeric and lead-rubber bearings
Bearings in any bridge will have different stiffnesses and in order to study the sensitivity of bridge response to variations in bearing properties a number of analyses were carried out with different bearing stiffnesses, strengths and postyield dissipator stiffnesses for the deck supported on a combination of elastomeric and lead-rubber bearings and rigid abutments (Bridge # 1 )
Parkfield earthquake always induces the greatest response. These figures are drawn for 5% critical damping and relate more closely to decks on elastomeric bearings. Those supported on lead-rubber bearings have a larger equivalent viscous damping ratio and the spectral displacements and accelerations will be smaller than shown in the Figures
Summary
The authors have described the influence that geometric factors such as pier heights (uniform or non-uniform) and the number of spans [1] have on the seismic response of bridges mounted on elastomeric bearings or a combination of elastomeric and lead-rubber bearings. Bearings in any bridge will have different stiffnesses and in order to study the sensitivity of bridge response to variations in bearing properties a number of analyses were carried out with different bearing stiffnesses, strengths and postyield dissipator stiffnesses for the deck supported on a combination of elastomeric and lead-rubber bearings and rigid abutments (Bridge # 1 ). All the properties were varied by +/- 20% and the results of the different analyses are shown in Table It shows that the natural period of the bridge could lie between 0.77 and 0.85 seconds, a range within which the spectral accelerations and displacements are generally changing rapidly. The variation in deck displacement at the piers is generally small, with maximum variations of +4% and - 5 % from the normal case, the exception being when both abutment bearing stiffnesses are 20% greater than the design value. BULLETIN OF THE NEW ZEALAND NATIONAL SOCIETY FOR EARTHQUAKE ENGINEERING, Vol 19, No 4, December 1986
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