Earthquake Engineering Research - HKU Libraries - The University ...

271
7)- C = Z;;i 2 (/ w *i/*,|) and V u yu ^^(f^x, /|x,|) , at two levels: before yielding and at the
initiating of collapse, respectively, define the degree of the unbalanced strength distribution at the two
sides of the center of mass. The variation of the value V^ ~ V^ shows the change of the possibility of the
occurring of the pure shear mechanism. Corresponding with the change of the strength eccentricity, this
value should represent the state of some weaker structural members being damaged on one side of the
center of mass while remaining elastic on the other side of the CM. Fig.4 does not show the peak value
directly
From the determination of the two critical boundary of the torsional-lateral coupling system, it can be
inferred that the seismic response of the base shear-torque is naturally divided into 3 regions that
represent respectively the linear elastic state, nonlinear state and the destroyed collapse state. The two
critical boundaries, which signify the initiating yield and collapse, can be established independently
based on the yield strength and the ultimate strength of structural members. This model can be directly
used to estimate both of the overall seismic capacity and the developing trends of the time history
response of the system base shear-torque to strong earthquakes even without complicated nonlinear
analysis.
«Collapse boundary of the state space
Yielding Boundary
* Dotted area: Time-history responses of the base shear-torque in earthquake simulation
test for specimen 2
Fig.5 comparison of the theoretically established state space of the base shear-torque with experimental results
Fig.5 shows the comparison of the theoretical state space of the base shear-torque with the experimental
results. The time-history shear-torque response of the bi-directional asymmetric single-story RC system
in 19 cases of ground excitations illustrates highly consistency with the state space established based on