NEHRP Clearinghouse

Active Control for Seismic-Resistant Structures on Embedded Foundation in Layered Half-Space.
Cheng, F. Y.; Suthiwong, S.
National Science Foundation, Arlington, VA.; National Center for Earthquake Engineering Research, Buffalo, NY., August 1996, 297 p.
Identifying Number(s)
The response behavior of seismically excited frame structures with active control and boundless soil is investigated. Mathematical models based on the existence or absence of structure-soil interaction (SSI) and/or control are presented. With SSI consideration, the frequency-dependent property of unbounded nonhomogeneous soil and foundation embedment is applied. Optimal closed-loop laws are established based on the generalized performance index. In the control system considering SSI effects, foundation translation and rocking are included in the control rule. Algorithms are implemented in the time domain. Studies indicate the strong influence of foundation embedment and depth of soil layer on soil-rocking coefficients and consequently on structural response. In a certain structure, additional modes as a result of the foundation's degrees of freedom dominate and hence result in distinct structural response behavior. In the control system including SSI effects, reduction of structural response is a result of the decrease in foundation rocking rather than relative floor translation which occurs where the structure is fixed at its base. Futhermore, the effect of control force in strengthening the system's stiffness and damping is reduced in the case of a structure founded on soft soil.
; Dynamic response; Half spaces; Earthquake resistant structures; Earthquake engineering; Structural design; Soil-structure interactions; Foundations (Structures); Vibration damping; Stiffness; Coefficients; Active control; Degrees of freedom; Mathematical models; Algorithms; Excavation; Closed loop systems; Dynamic structural analysis