Fluid Viscous Dampers General Guidelines for Engineers Including a Brief History

[sabooryan]

Fluid Viscous Dampers General Guidelines for Engineers Including a Brief History

Author(s)/Editor(s): Alan Klembczyk - Mark Berquist - Richard DePasquale - Sean Frye - Amir Gilani- David Lee- Aaron Malatesta - John Metzger- Robert Schneider- Chris Smith- Douglas Taylor - Shanshan Wang - Craig Winters | Size: 30 MB | Format: PDF | Quality: Original preprint | Publisher: taylor devices company | Year: 2018 | pages: 268

The end of the Cold War in 1990 heralded a restructuring period for the American military and defense industry. One of the outcomes of this new era was that political and economic change allowed previously restricted technologies to become available to the general public. This conversion of defense technology is typified by highly advanced products and services that suddenly appeared in the marketplace, seemingly out of nowhere. Perhaps the best known of these is the now ubiquitous Internet, which in reality came from 1970's defense technology intended for use by government agencies in the event of nuclear war.
In the civil engineering field, high capacity fluid dampers have transitioned from defense related structures to commercial applications on buildings and bridges subjected to seismic and/or wind storm inputs. Because fluid damping technology was proven thoroughly reliable and robust through decades of Cold War usage, implementation on commercial structures has taken place very quickly.
Indeed, over the last 30 years, utilizing various types of added-damping devices in structures has emerged as a useful, reliable and predictable tool in significantly improving the resiliency of structures to a dynamic input. Much research and testing have been performed that verifies the benefits of incorporating added-damping devices in structures. Linear and non-linear fluid viscous dampers continue to demonstrate excellent performance in reducing deflection, acceleration response, interstory drift and stress. Damping device designs that have been well proven through decades of use are available in configurations that provide forces that depend on input velocity, deflection, or a combination of both.
Although various building codes have emerged throughout the world that address methods and response requirements of structures when utilizing damping devices, these codes do not provide a general comparison in improved resiliency that is realized through their use.
The concept of damping within a structural system can have different meanings to the various engineering disciplines. To the civil engineer, damping may mean only a reference note on a seismic or wind spectral plot, “5% damped spectra” being the most common notation. To the structural engineer, damping means changes in overall stress within a structure subject to shock and vibration, with frequent arguments whether a structure will have “2%, 3%, 4%, but not more than 5%” structural damping. On the other hand, mechanical engineers do not necessarily view damping as a benevolent feature, since machines, by definition, are supposed to transmit forces and motions efficiently, without energy losses. Thus, the need for damping in a machine often signifies that an engineering design error has been made.
In the classical mechanical engineering text “Vibration Theory and Applications,” William Thomson [1] avoids a single, direct definition of damping by offering the following descriptions: “Vibrating systems are all more or less subject to damping because energy is dissipated by friction and other resistances. Since no energy is supplied in free vibration, the motion in free vibration will diminish with time, and is said to be damped.
It follows from these descriptions that a damper is an element which can be added to a system to provide forces which are resistive to motion, thus providing a means of energy dissipation. Assuming that this working definition will suffice for general use, the next area of interest is to generally describe the functional output of a damper. As with the definition of damping, the functional output of a damper is somewhat controversial, since different output equations exist within the context of the various engineering disciplines.
Alternatively, damping can be defined as that attribute of a dynamic system that results in a decrease in the amplitude of oscillation. This results in the removal of some amount of energy in that system.
In keeping with the law of conservation of energy, this energy is actually transformed into another form. Consequently, the term “damper” can be defined as that mechanism or internal property that provides this transfer of energy. Typically, damping converts mechanical energy into heat. This heat is then dissipated to the surroundings through any of the 3 modes of heat transfer defined as conduction, convection and radiation.
Fluid viscous dampers operate by providing a resisting force only when moving. They do not add stiffness to a structure, and they do not carry any static load.
Like automobiles driven on a bumpy road, buildings in seismic regions are a dynamic problem. Who would ever buy or manufacture a car without shock absorbers? The dynamic laws of physics are the same for each.
It is with great pleasure that Taylor Devices offers this damper manual as a guide for engineers with various levels of experience in order to take advantage of this technology that has been successfully transitioned from previous applications to now improve the dynamic performance of structures and to help save lives throughout the world.

Code:

***************************************
Content of this section is hidden, You must be registered and activate your account to see this content. See this link to read how you can remove this limitation:

http://forum.civilea.com/thread-27464.html
***************************************

This post has been made by CivilEA Post-Generator V2.3.1

[bridgeengineer]

please reupload

thanks