Compare response spectrum, isolator displacement, and base-shear reduction to see how period shift and damping work together.
Parameters
Fixed-base period
s
Building period before isolation.
Isolated period
s
Target isolated period.
Equivalent damping
%
Equivalent damping including isolators.
Input PGA
g
Peak ground acceleration.
Effective mass
t
Participating building mass.
Results
—
Acceleration reduction
—
Isolation displacement
—
Base shear
—
Period shift
Isolation response spectrum
Isolation displacement
Base shear reduction
Model and equations
$$T=2\pi\sqrt{M/K},\quad V\approx M S_a(T,\xi)$$
Base isolation lengthens the period and adds damping to reduce superstructure acceleration. Real design also checks nonlinear hysteresis, displacement limits, wind, and vertical motion.
How to read it
The spectrum view shows where longer period lowers acceleration.
The displacement view shows the price paid for acceleration reduction.
The base-shear view compares force demand against fixed-base behavior.
Learn Base Isolation Period Shift by dialogue
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When reading Base Isolation Period Shift, where should I look first? Moving Fixed-base period changes both the plots and the result cards.
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Start with Acceleration reduction, but do not treat the number as the whole answer. Use Isolation response spectrum to confirm the assumed state, then read Isolation displacement for the distribution or trend. The spectrum view shows where longer period lowers acceleration.
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I can see why Fixed-base period changes Acceleration reduction. How should I judge the influence of Isolated period?
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Move Isolated period in small steps and watch Isolation displacement. That reveals which term is controlling the result. Base isolation lengthens the period and adds damping to reduce superstructure acceleration. Real design also checks nonlinear hysteresis, displacement limits, wind, and vertical motion. A single operating point is not enough; sweep the realistic scatter range.
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What is Base shear reduction for? It feels like the ordinary curve already tells the story.
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Base shear reduction is for finding boundaries where the condition becomes risky or margin collapses quickly. The displacement view shows the price paid for acceleration reduction. In Explaining early benefit of base isolation, the important question is often what happens after a small change, not only the nominal value.
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So if Acceleration reduction is within the target, can I accept the condition?
🎓
Treat this as a first-pass review. It helps with Comparing isolated period and damping candidates and Checking displacement order before time-history analysis, but final decisions still need standards, measured data, detailed analysis, and vendor limits. The base-shear view compares force demand against fixed-base behavior.
Practical use
Explaining early benefit of base isolation.
Comparing isolated period and damping candidates.
Checking displacement order before time-history analysis.
FAQ
Start with Acceleration reduction and Isolation displacement. Then use Isolation response spectrum to confirm the assumed state and Isolation displacement to read distribution or bias. The spectrum view shows where longer period lowers acceleration
Move Fixed-base period alone, then move Isolated period by a comparable amount and compare the change in Acceleration reduction. Base shear reduction shows combinations where margin or performance changes quickly.
Use it for Explaining early benefit of base isolation. Instead of trusting a single point, widen the input range and check whether Acceleration reduction keeps enough margin before moving to detailed analysis.
Base isolation lengthens the period and adds damping to reduce superstructure acceleration. Real design also checks nonlinear hysteresis, displacement limits, wind, and vertical motion. Final decisions still require standards, measured data, detailed analysis, and vendor limits.