Improvements to lead-extrusion damper technology

Cousins, W. J.; Porritt, T. E.

doi:10.5459/bnzsee.26.3.342-348

Cited by 26 publications

(23 citation statements)

References 5 publications

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“…A recent review of wall slip possibilities in non-Newtonian flows can be found in [39]. Concerning the present application, the interface between the shaft and the extruded material is often lubricated and the shaft surface is polished [8,9]. Hence, in the present study, in order not to overly increase the complexity of the problem, it was decided to apply the simple Navier slip boundary condition on the polished shaft and the no-slip boundary condition (Eq.…”

Section: Problem Definition and Governing Equationsmentioning

confidence: 99%

“…Here the "fluid" is actually a ductile solid material which is forced to flow through an annular contraction. Such dampers can carry significant loads and have been proposed and used for seismic protection of structures using lead as the plasticallydeforming material [8][9][10]. Lead recrystallizes at room temperature and thus recovers most of its mechanical properties immediately after extrusion, so that lead extrusion dampers can undergo a large number of cycles of operation without performance degradation.…”

Section: Introductionmentioning

confidence: 99%

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Viscoplastic flow in an extrusion damper

Syrakos

Dimakopoulos

Georgiou

et al. 2016

Journal of Non-Newtonian Fluid Mechanics

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Numerical simulations of the flow in an extrusion damper are performed using a finite volume method. The damper is assumed to consist of a shaft, with or without a spherical bulge, oscillating axially in a containing cylinder filled with a viscoplastic material of Bingham type. The response of the damper to a forced sinusoidal displacement is studied. In the bulgeless case the configuration is the annular analogue of the well-known lid-driven cavity problem, but with a sinusoidal rather than constant lid velocity. Navier slip is applied to the shaft surface in order to bound the reaction force to finite values. Starting from a base case, several problem parameters are varied in turn in order to study the effects of viscoplasticity, slip, damper geometry and oscillation frequency to the damper response. The results show that, compared to Newtonian flow, viscoplasticity causes the damper force to be less sensitive to the shaft velocity; this is often a desirable damper property. The bulge increases the required force on the damper mainly by generating a pressure difference across itself; the latter is larger the smaller the gap between the bulge and the casing is. At high yield stresses or slip coefficients the amount of energy dissipation that occurs due to sliding friction at the shaft-fluid interface is seen to increase significantly. At low frequencies the flow is in quasi steady state, dominated by viscoplastic forces, while at higher frequencies the fluid kinetic energy storage and release also come into the energy balance, introducing hysteresis effects.

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Section: Problem Definition and Governing Equationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Viscoplastic flow in an extrusion damper

Syrakos

Dimakopoulos

Georgiou

et al. 2016

Journal of Non-Newtonian Fluid Mechanics

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“…where F is the damper force; C a a force constant, _ x the velocity of the damper shaft with respect to the outer casing; a the velocity exponent (a = 0.11-0.15) [11,12].…”

Section: Experimental Investigationmentioning

confidence: 99%

“…If Equations (7), (9), (11), and (12b) are substituted into Equation (13) and re-arranged, then K 2 can be written as follows:…”

Section: B) A)mentioning

confidence: 99%

“…Under full cyclic loading, the model must incorporate connection behavior for both positive and negative rotations in the presence of prestressing tendons that are not centrally located (j + 6 ¼ j -) with respect to the beam centreline. Under these conditions, the model parameters M gap , M yield , K 2 and Δ o are all directionally dependent, as they are all a function of the fractional lever-arm j, as defined in Equations (7), (11), (14), and (27), respectively. To accommodate this directional dependence, the values need to be switched based on the direction of loading, and the associated value of either j þ PT or j À PT in Figure 3(b).…”

Section: Overall Connection Modelingmentioning

confidence: 99%

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Modeling cyclic loading behavior of jointed precast concrete connections including effects of friction, tendon yielding and dampers

Rodgers

Mander

Chase

2012

Earthq Engng Struct Dyn

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SUMMARY Reversed cyclic loading behavior of jointed precast prestressed concrete beam‐to‐column connections are computationally modeled and validated against full‐scale experimental results. Response simulations are performed with and without supplemental high force‐to‐volume (HF2V) energy dissipation devices. The experimental specimen is a three‐dimensional corner connection of a jointed precast concrete frame structure, utilizing unbonded post‐tensioned tendons consisting of high‐alloy, high‐strength thread‐bars. The joint region is armored, to avoid damage, by providing steel plates at the beam–column (rocking) contact points. The analytical model of the connection is developed to include modifications for the effects of changing connection behavior. These effects are friction within the prestressing system, yielding of the prestressing tendons, reduction or elimination of prestress attributable to prior tendon yield, and directional dependence caused by an asymmetrical prestress system. Particular attention is given to developing a robust model that can accommodate small reversals in the displacement loading. The model is extended to incorporate the effects of the HF2V energy dissipation devices and the associated flexibility from the elements that connect the devices to the structure. Although the model is applied to the use of HF2V (lead extrusion) energy dissipation devices, it is general and can accommodate any non‐linear rate‐dependent damper. The computational model is based almost entirely on rational mechanics and shows good agreement with the full‐scale experimental observations. Copyright © 2012 John Wiley & Sons, Ltd.

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Semi‐explicit rate‐dependent modeling of damage‐avoidance steel connections using HF2V damping devices

Rodgers

Mander

Chase

2010

Earthq Engng Struct Dyn

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A rate-dependent modeling technique is developed for moment resisting steel connections that utilize non-linear viscous dampers. First, a model of the Maxwell-type is developed that considers the non-linear viscous damper and connection flexibility for translational motion. This model is compared to experimental results at several input motion frequencies to validate the results. The model is then extended to represent an exterior steel beam-to-column connection using damage avoidance design and non-linear viscous dampers. By including terms to represent structural member and connection flexibility, using appropriate geometric transformations the model can be formulated to give the overall lateral load-drift structural performance. Validation analysis shows good agreement between experimental observations and the model predictions.

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Improvements to lead-extrusion damper technology

Cited by 26 publications

References 5 publications

Viscoplastic flow in an extrusion damper

Viscoplastic flow in an extrusion damper

Modeling cyclic loading behavior of jointed precast concrete connections including effects of friction, tendon yielding and dampers

Semi‐explicit rate‐dependent modeling of damage‐avoidance steel connections using HF2V damping devices

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