Research

FOCUS ON RESEARCH
AE Newsletter - Spring/Summer 2001
ARE VIBRATING FLOORS SHAKING YOU UP? By Dr. Linda Hanagan, ’85, ’92, P.E., Assistant Professor I have been conducting research on the serviceability of building floor systems (floor vibrations) for about ten years. During this time, my research has had two main thrusts: repairing light-weight floor systems prone to excessive vibration; and exploring better ways to predict the expected vibration behavior before construction. My research on repairing lightly damped floor systems implements active control technology to improve the dynamic behavior of a floor system subjected to resonant excitations like walking, dancing, and aerobics. Specifically, I have developed an Active Floor Vibration Control System that can be installed on the floor or in the ceiling cavity below with very little disruption to the occupants. The goal of the active control scheme is to add damping to the floor system, thus improving the floor system response with respect to human perception. The Active Floor Vibration Control System is similar in concept to the tuned mass damper (TMD) in that it relies on a moving mass to dissipate energy in the floor system. The advantage of the active system, which utilizes floor velocity measurements in a feedback loop, is that it requires much less moving mass to effect the same degree of control as a TMD. One study showed that the TMD would need to weigh as much as 30 times more. When TMDs have been ruled out as a repair option because the existing structure can’t support the additional weight, the active system could be the only viable option. Initially, the active control system was developed to control excessive vibrations due to walking excitation. Controlling larger excitations, like dancing and aerobics, wasn’t possible due to the very restrictive force limitation of the electromagnetic actuator used in the control loop. Since my initial research (funded in large part by the National Science Foundation and described in several publications listed on my web site), the Active Floor Vibration Control System has been further refined to control larger excitations on low frequency floors such as long-span ballroom floors and spectator balconies. Along with Penn State’s Intellectual Property Office, I am pursuing a patent and have partnered with a private company to make this system commercially available. Perhaps by the next newsletter, I will be able to report our first permanent installation!	While providing a new repair option for vibrating floors does have merit, research to provide design engineers with better tools to predict vibration behavior and anticipate vibration problems is also important. The goals of this research are to better quantify the vibration behavior of in-place floor systems using a case study approach and to bring a realism to this very complex phenomenon. This research was actually precipitated by my stint as a lecturer of an AISC Short Course: Designing Steel for Serviceability. I taught the hour on “Control of Floor Vibrations,” which basically introduced the then-new Design Guide 11: Floor Vibrations Due to Human Activity. From this experience, as well as other interactions within the design community, I have witnessed emotions on this subject that range from confusion to frustration and even open hostility toward those whom they identify as “experts” in the area. The negative feelings seem to be mostly the result of a lack of information available to the designer. To provide more information to designers, we are developing a “floor vibration” web site. (We hope to have the website available linked from the PSU/AE web page before the end of the year.) The core of this continually evolving website will be a database comprised of floor vibration case studies. The case studies include actual measurements from in-place floors, comparisons with predicted behavior, and discussions of occupant reactions. We will include all types of floors from typical office floors to long-span ballroom floors to floors supporting sensitive equipment. The information from this database will also be used by myself, and hopefully others, to improve existing guidelines and to develop more sophisticated and accurate methods of evaluation. This research, currently underway, has been supported in part by the National Science Foundation, the American Institute of Steel Construction (with AE alumni Charlie Carter ’89 (B.A.E.), ’91 and Keith Grubb ’91 (B.A.E), ’93 (M.S.), Milton Steel (with AE alumni Vel Holcombe ’64 and Chris Holcombe ’90), and New Columbia Joist (with AE alumnus Drew Potts ’88). I, along with the students whose education has been funded in part by this project, gratefully acknowledge this support. For this project to be a complete success, we also need you! If you have a floor system that you would like to have measured, and that we could include in our database, get in touch with me either through email (hanagan@psu.edu) or by phone (814-863-2084). Do you have a floor vibration question or problem? Give me a call, and I’ll see what I can do.

FOCUS ON RESEARCH

AE Newsletter - Spring/Summer 2001

ARE VIBRATING FLOORS SHAKING YOU UP?
By Dr. Linda Hanagan, ’85, ’92, P.E., Assistant Professor

I have been conducting research on the serviceability of building floor systems (floor vibrations) for about ten years. During this time, my research has had two main thrusts: repairing light-weight floor systems prone to excessive vibration; and exploring better ways to predict the expected vibration behavior before construction.

My research on repairing lightly damped floor systems implements active control technology to improve the dynamic behavior of a floor system subjected to resonant excitations like walking, dancing, and aerobics. Specifically, I have developed an Active Floor Vibration Control System that can be installed on the floor or in the ceiling cavity below with very little disruption to the occupants. The goal of the active control scheme is to add damping to the floor system, thus improving the floor system response with respect to human perception.

The Active Floor Vibration Control System is similar in concept to the tuned mass damper (TMD) in that it relies on a moving mass to dissipate energy in the floor system. The advantage of the active system, which utilizes floor velocity measurements in a feedback loop, is that it requires much less moving mass to effect the same degree of control as a TMD. One study showed that the TMD would need to weigh as much as 30 times more. When TMDs have been ruled out as a repair option because the existing structure can’t support the additional weight, the active system could be the only viable option.

Initially, the active control system was developed to control excessive vibrations due to walking excitation. Controlling larger excitations, like dancing and aerobics, wasn’t possible due to the very restrictive force limitation of the electromagnetic actuator used in the control loop. Since my initial research (funded in large part by the National Science Foundation and described in several publications listed on my web site), the Active Floor Vibration Control System has been further refined to control larger excitations on low frequency floors such as long-span ballroom floors and spectator balconies. Along with Penn State’s Intellectual Property Office, I am pursuing a patent and have partnered with a private company to make this system commercially available. Perhaps by the next newsletter, I will be able to report our first permanent installation!

While providing a new repair option for vibrating floors does have merit, research to provide design engineers with better tools to predict vibration behavior and anticipate vibration problems is also important. The goals of this research are to better quantify the vibration behavior of in-place floor systems using a case study approach and to bring a realism to this very complex phenomenon. This research was actually precipitated by my stint as a lecturer of an AISC Short Course: Designing Steel for Serviceability. I taught the hour on “Control of Floor Vibrations,” which basically introduced the then-new Design Guide 11: Floor Vibrations Due to Human Activity. From this experience, as well as other interactions within the design community, I have witnessed emotions on this subject that range from confusion to frustration and even open hostility toward those whom they identify as “experts” in the area. The negative feelings seem to be mostly the result of a lack of information available to the designer.

To provide more information to designers, we are developing a “floor vibration” web site. (We hope to have the website available linked from the PSU/AE web page before the end of the year.) The core of this continually evolving website will be a database comprised of floor vibration case studies. The case studies include actual measurements from in-place floors, comparisons with predicted behavior, and discussions of occupant reactions. We will include all types of floors from typical office floors to long-span ballroom floors to floors supporting sensitive equipment. The information from this database will also be used by myself, and hopefully others, to improve existing guidelines and to develop more sophisticated and accurate methods of evaluation.

This research, currently underway, has been supported in part by the National Science Foundation, the American Institute of Steel Construction (with AE alumni Charlie Carter ’89 (B.A.E.), ’91 and Keith Grubb ’91 (B.A.E), ’93 (M.S.), Milton Steel (with AE alumni Vel Holcombe ’64 and Chris Holcombe ’90), and New Columbia Joist (with AE alumnus Drew Potts ’88). I, along with the students whose education has been funded in part by this project, gratefully acknowledge this support.

For this project to be a complete success, we also need you! If you have a floor system that you would like to have measured, and that we could include in our database, get in touch with me either through email (hanagan@psu.edu) or by phone (814-863-2084). Do you have a floor vibration question or problem? Give me a call, and I’ll see what I can do.

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