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By Valentin Shustov landmark projects or those with practically unlimited budgets. The irony of the situation lies in the fact that engineers are under no pressure to make the control effective: the contemporary building regulations require neither performance based design nor performance testing. Due to this, the inadequate regulations permit indiscriminate implementation of this technology. |
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No wonder: neither optimization study of dynamic structural control in general nor with respect to controlling devices parameters K (lateral stiffness) and C (damping) were performed until recently (Shustov, 1997) when the Charts of Seismic Performance (CSP) technique was introduced. A CSP resembles the isoseismic maps of seismic zonation. However, the contours here connect the points of equal Mitigation Factor in the domain of K and C coordinates. |
| Mitigation Factor (MiF) equals a ratio of the maximum story drift without structural control to that with the control (Shustov, 1994). If isolation is effective, MiF >1 holds. Otherwise, MiF<1, which should not be tolerated even for any limited range of ground frequencies. |
| The CSP
will reduce often lengthy and costly computations at a conceptual / preliminary
design stage and will considerably simplify the decision making process.
Charts of Seismic Performance for a given building's structural type is a system consisting of a number of individual charts like one shown on the right. The data from the previous research (Shustov, 1993), having been transformed into terms of MiF, reveal its dependency on a story number N and earthquake intensity. Therefore, a system of CSPs constitutes a matrix where the horizontal rows account for different numbers of stories while the vertical ones represent different seismic intensities . |
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Each element of the system
matrix, an individual CSP, relates to
a certain structural type and height of a building and to a certain magnitude
of earth shaking. The rectangles on the plane K-C should account
for possible deviations in the control device's stiffness and damping characteristics
and may be called the Control Devices Footprints.
Having been projected on the corresponding chart levels, they screen the
areas of the anticipated mitigation.
In order to start, the user needs to specify a particular chart to deal with. Then make projections of the targeted footprints, say A, B and C, on the chosen chart (on the left). It is obvious that the device A has the best MiF. |
| The global optimization technique with the help of Charts of Seismic Performance represents an expansion of the response spectra approach to the MDOF building systems. It provides a user-friendly graphical environment that may prevent unwarranted extrapolation of favorable and overoptimistic judgments onto the range of parameters where those judgments do not not belong. |
| Shustov, V.,
1993, "Base
Isolation: Fresh Insight", Technical Report to NSF BCS-9214754,
SRE, Los Angeles, CA. Shustov, V., 1994, "Energy Absorbing Technique: Challenge of Proportioning", Proc. 3rd Int'l Conf. on Structures under Shock and Impact, Madrid, Spain. Shustov, V., 1997, "Future Seismic Codes and Earthquake Insurance", Proc. 66th Annual SEAOC Convention, San Diego, CA. |
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