High force-to-volume extrusion dampers and shock absorbers for civil infrastructure
High force-to-volume extrusion dampers and shock absorbers for civil infrastructure
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2006
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通讯作者：
G. Rodgers;J. Chase;J. Mander;Nicholas C. Leach;Caleb S. Denmead;L. Cleeve;D. Heaton
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作者：
G. Rodgers;J. Chase;J. Mander;Nicholas C. Leach;Caleb S. Denmead;L. Cleeve;D. Heaton
以受控和可重复的方式耗散地震、风和冲击载荷产生的结构能量的能力对于在一系列大环境载荷下保持结构完整性至关重要。基于挤压的阻尼技术是实现这些设计要求的一种很有前途的方法，并且已经广泛应用于基础隔震应用中。然而，当前设备的大尺寸阻止了限制其广泛使用的若干独特实现。本研究发展高力-体积比挤压阻尼器，其体积足够小，可用于典型的结构连接。重新定心挤压装置将该技术扩展到高冲击载荷应用。设计，分析和实验验证已经进行的铅挤压阻尼器足够紧凑，允许直接放置到通用柱部分标称350毫米深（W14）。峰值力水平高达450 kN，行程高达50 mm，具有最佳（几乎完全矩形）的磁滞回线。开发了具有一定重定心能力的用于高力冲击载荷应用的减振器，其刚度值高达3.6 MN/m，力水平高达300- 400 kN。这些后一种装置在工业结构冲击载荷应用中具有巨大的潜力，例如大型船舶的系泊。整体结果表明，最大的能量耗散与高的力/体积关系，可以开发和铅挤压阻尼器的特点。力和位移约束内的面积。先前的研究表明，这些设备可以产生显着减少地震反应的基础上频谱响应分析套概率缩放地面运动（罗杰斯等人，2006年）。本研究概述了高力-容积阻尼器的实验测试和开发。初步设计分析和一些实验验证的重新定心结构减震器提出进一步扩展这些设备的可能应用，以减少冲击载荷力，并提供重新定心能力，利用避免损坏的设计摇摆关节。独特的设备设计也显示，使非对称磁滞回线，最大限度地提高能量吸收，但最大限度地减少残留漂移。本研究的目的是提供一个实验调查的效力和实施高力-体积挤压阻尼器。它还提出了可能的未来发展可能通过优雅的设备设计与重定心能力。在这种情况下，先进的重定心装置使用这些相同的原则的设计空间也被提出。2设计和分析2.1实验装置的开发铅挤压阻尼器可以分为两组的基础上基本的设计差异。这些类型是收缩管型和膨胀轴型（Wellins和Porritt，1993年）。这两种类型都利用相同的基本概念，即通过将铅塑性挤压穿过由环形限制件形成的孔口来提供阻力。对于收缩管阻尼器，孔口由外筒的孔上的收缩部形成。相比之下，膨胀轴阻尼器利用中心轴上的流线型凸起。每一种的相对优点都有文件记录（Reinins & Porritt，1993），主要集中在易于制造和实现可预测和可重复性能的能力上。在本研究中构建和测试的原型是基于低成本和易于制造的凸出轴设计。初始原型的设计与基本尺寸如图1所示。还构建并测试了第二原型装置，其具有与图1所示类似的设计，但具有66 mm的内部圆柱体直径和20 mm的壁厚。与挤出过程相关的塑性变形吸收大量能量，并提供更硬的阻尼器，能够吸收比同等尺寸的流体粘性阻尼器多得多的能量，因为铅的体积模量要大得多。两个主要因素限制了可以耗散的能量。首先，基于尺寸和材料的轴屈服载荷限制了力水平。其次，阻尼器在重复循环时产生的热量软化了周围的铅并降低了电阻。这两个因素可以通过设备设计和制造来合理地管理。这种阻尼方法的一个主要问题是当工作材料被挤压通过限制时在工作材料内形成空隙。对于铅挤压阻尼器，这种空隙的形成是由于铅压缩、气缸壁的膨胀以及铸件中留下可被压缩的气隙或微尺寸空隙的缺陷。因此，当凸起移动通过材料时，它被压缩成较小的体积，留下一个尾随的空隙。因此，当凸起在随后的循环中穿过该空隙时，阻尼器经历较小的阻力并且耗散少得多的能量。为了最大限度地减少空隙的形成，在这项研究中，铅是预应力，这有助于减少铸造孔隙和空气间隙之前，阻尼器的使用。因此，空隙的尺寸（占总电极导线体积的百分比）被最小化，以优化最终器械设计的性能。
The ability to dissipate structural energy from seismic, wind and impact loads in a controlled and repeatable manner is essential to maintaining structural integrity for a range of large environmental loads. Extrusion based damping technology is a promising method of achieving these design requirements and is already widely used in base isolation applications. However, the large size of current devices prevents several unique implementations limiting their widespread use. This research develops high force-to-volume extrusion dampers small enough in volume for use in typical structural connections. Re-centering extrusion-based devices extend the technology to high impact loading applications. Design, analysis and experimental verification has been undertaken on lead extrusion dampers sufficiently compact to allow direct placement into universal column sections nominally 350mm deep (W14). Peak force levels up to 450kN with strokes up to 50mm are developed with an optimal (almost fully rectangular) hysteresis loop. Shock absorbers for high force impact loading applications with some recentering capability are developed, with stiffness values up to 3.6 MN/m, and force levels up to 300-400kN. These latter devices have significant potential for industrial structural impact loading applications, such as moorings of large ships. The overall results indicate that maximum energy dissipation with high force/volume relationships can be developed and characterized for lead extrusion dampers. area within the force and displacement constraints. Previous research has shown that these devices can produce significant reduction in seismic response based on spectral response analysis over suites of probabilistically scaled ground motions (Rodgers et al, 2006). This research outlines the experimental testing and development of high force-to-volume dampers. The preliminary design analysis and some experimental verification of re-centering structural shock absorbers presented further extends possible applications of these devices to reduce impact loading forces and provide re-centering capability to rocking joints that utilise the Damage Avoidance Design. Unique device design is also shown to enable nonsymmetric hysteresis loops that maximise energy absorption, but minimise residual drift. The goal of this research is to provide an experimental investigation into the efficacy and implementation of high force-to-volume extrusion dampers. It also presents possible future developments made possible by elegant device design with recentering capability. In this context, the design space for advanced recentering devices using these same principles are also presented. 2 DESIGN AND ANALYSIS 2.1 Experimental Device Development Lead extrusion dampers can be categorised into two groups based upon fundamental design differences. These groups are the constricted tube type, and the bulged shaft type (Cousins & Porritt, 1993). Both types utilise the same basic concept of providing a resistive force by plastically extruding lead through an orifice created by an annular restriction. For a constricted tube damper, the orifice is created by a constriction on the bore of the outer cylinder. In contrast, bulged shaft dampers utilise a streamlined bulge on the central shaft. The relative merits of each are documented (Cousins & Porritt, 1993) and focus primarily upon ease of manufacture and the ability to achieve predictable and repeatable performance. The prototypes constructed and tested within this research are based upon the bulged shaft design for low cost and ease of manufacture. The design of the initial prototype is presented with basic dimensions in Figure 1. A second prototype device was also constructed and tested, with a similar design to that shown in Figure 1, but with an internal cylinder diameter of 66mm, and a wall thickness of 20mm. The plastic deformation associated with the extrusion process absorbs large amounts of energy and provides a much stiffer damper capable of absorbing far more energy than an equivalent sized fluid viscous damper due to the much larger bulk modulus of the lead. Two major factors limit the amount of energy that can be dissipated. First, the shaft yield load, based on size and material, restricts force levels. Second, the heat produced by the damper on repeated cycles softens the surrounding lead and reduces resistance. Both factors can be reasonably managed by the device design and manufacture. One major issue with this method of damping is the formation of voids within the working material as it is extruded through the restriction. For a lead extrusion damper, this void formation is due to the lead compressing, expansion of the cylinder wall, and imperfections in the casting that leaves air gaps or micro-sized voids that can be compressed. Hence, as the bulge moves through the material it is compressed into a smaller volume, leaving a trailing void. Thus, as the bulge passes through this void on following cycles the damper experiences less resistance and dissipates much less energy. To minimize void formation in this study the lead is prestressed, which helps reduce casting porosity and air gaps before the damper is used. Thus, the size of the void, as a percentage of the total lead volume, is minimised to optimise performance of the final device design.