It’s no secret that earthquakes come in all sizes with varying degrees of damage depending on the geographic locations where they occur. And even a small one on the Richter scale that strikes in an impoverished nation can be more damaging than a larger one that occurs in a city where all buildings have been designed to a stricter building code.
According to Charney, attaining acceptable structural performance is a problem even when the current building codes are used as intended for the structural design.
“In my opinion, the current building codes are insufficient because buildings designed according to these codes have evolved only to avoid collapse under very large earthquakes. These same buildings, subjected to smaller, more frequent earthquakes, may have excessive damage, as happened during the 1994 Northridge, California earthquake. I tell my students that good performance for these buildings is not in their DNA,” Charney said.
In the future, structural engineers will base their designs on the concepts of Performance Based Earthquake Engineering (PBEE), where the objective is to control damage and provide life-safety for any size of earthquake that might occur. Charney and Singh said they are developing a variety of new structural systems that “will inherently satisfy PBEE standards, yet have negligible damage when subjected to frequent earthquakes, acceptable damage from moderate earthquakes, and a low probability of collapse during the rare, severe earthquake.” To achieve their goal, they are creating four new PBEE compliant systems called hybrid yielding, standard augmented, advanced augmented, and collapse prevention systems.Charney explained the hybrid yielding system is an improved configuration of an existing system. The key aspect of this enhanced system is that certain components in a structure are designed to yield sooner than what would occur in a traditional system, and other components are designed to yield later. By controlling the sequence of yielding, the dissipation of the seismic energy that comes with the early yielding should allow the structure to meet low-level and mid-level performance requirements, and the residual stiffness provided through delayed yielding will enhance life safety under larger earthquakes.
The standard augmented system will provide an enhanced performance because it utilizes devices called visco-elastic solid or viscous fluid dampers to help control vibrations. “The additional damping provided by these devices is intended to enhance a system’s performance primarily at the mid-level limit states,” Charney said.The third system, the advanced augmented, uses the damping devices in conjunction with special metallic yielding devices. “Typically the combination of the devices is two-phased, with the yielding component only engaging after a certain deformation occurs in the damping component,” Charney said.
He described the last system, the collapse prevention system, as “being analogous to an air bag in a car”. This system is completely passive until it is needed. It is designed for use in situations where the damage associated with frequent or occasional earthquakes is negligible, but a total structural collapse cannot be tolerated.
The researchers said all four new designs have common features; they improve structural integrity by limiting residual deformations, controlling dynamic stability, and minimizing the uncertainty in predicting response.
To complete all of this work, Charney says he will develop a computer program that will automatically set up and execute all of the structural analysis required for assessing compliance with the next generation of PBEE. Potentially, he will be analyzing hundreds of thousands of mathematical models of buildings, using one of Virginia Tech’s supercomputers. Charney and Singh have three Ph.D. degrees and several master’s students working on these projects. The project team is called VT-ACES, where ACES stands for Advanced Concepts in Earthquake-engineered Systems.
Charney is the author of Seismic Loads, a Guide to the Seismic Load Provisions of ASCE 7 published in 2010 by the American Society of Civil Engineers (ASCE). He is a regular seminar speaker for ASCE on the subject of earthquake engineering. In addition, he has developed two educational earthquake engineering computer programs NONLIN and EQ-Tools. These programs, used worldwide, have been recently updated though a grant received from the Building Seismic Safety Council.The College of Engineering (http://www.eng.vt.edu/) at Virginia Tech is internationally recognized for its excellence in 14 engineering disciplines and computer science. The college's 6,000 undergraduates benefit from an innovative curriculum that provides a "hands-on, minds-on" approach to engineering education, complementing classroom instruction with two unique design-and-build facilities and a strong Cooperative Education Program. With more than 50 research centers and numerous laboratories, the college offers its 2,000 graduate students opportunities in advanced fields of study such as biomedical engineering, state-of-the-art microelectronics, and nanotechnology. Virginia Tech, the most comprehensive university in Virginia, is dedicated to quality, innovation, and results to the commonwealth, the nation, and the world.
* Disaster management: A complex world brings new vulnerabilities(http://www.vtnews.vt.edu/articles/2009/12/2009-943.html)
* Assessing the seismic hazard of the central-Eastern United States (http://www.vtnews.vt.edu/articles/2011/01/010611-engineering-greenearth.html)This story can be found on the Virginia Tech News website:
Lynn A. Nystrom | VT News
Rock solid: Carbon-reinforced concrete from Augsburg
11.10.2016 | Universität Augsburg
Heating and cooling with environmental energy
22.09.2016 | FIZ Karlsruhe – Leibniz-Institut für Informationsinfrastruktur GmbH
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.
"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...
COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.
In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...
'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.
Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
21.10.2016 | Health and Medicine
21.10.2016 | Information Technology
21.10.2016 | Materials Sciences