A steel frame of eight storeys, three bays of 6 m each way: HEB400 columns built in at the ground, IPE450 beams and a 200 mm concrete slab at every floor, meshed twice a bay so that it shares the beams' nodes. The El Centro earthquake shakes the ground along x.
The first 12 s of El Centro, as they happened, the movement drawn larger than it is. Under it, the ground's acceleration and the roof's movement along x, over the same 12 s: the roof swings back and forth about once a second, behind the ground.
The model
| Group | What it does |
|---|---|
| 1 - Geometry | The sliders, and a Python component that draws the frame from them: the columns, the beams cut twice a bay, a slab mesh at every floor, the columns' feet, and the corner of the roof the charts follow. |
| 2 - Members | S355 HEB400 columns and IPE450 beams from Steel Section Library, as ForceBeamColumn; 200 mm of concrete, a Plate Fiber Section, as ASD Shells. |
| 3 - Supports | Every column built in at the ground. |
| 4 - Ground motion | The El Centro record from a Python component, its first Duration seconds times Ground motion scale; a Path Time Series of it; a Load Pattern of the UniformExcitation type, along the direction it shakes. |
| 5 - Transient analysis | Assemble; Damping, Rayleigh's from Damping and its two frequencies; the Newmark Integrator; Analysis Step, a step a sample of the record; Analysis Settings for a transient analysis with the Linear algorithm, one solve a step, as an elastic model needs; and Run Analysis. |
| 6 - Results | A Model View of the analysed model at Step, deformed 40 times, its elements' edges and its supports drawn, its colours in iso-surfaces on the slabs over 0 to 120 mm for every step alike, with a Legend. Drag Step to go through the record. |
The ground motion
El Centro, 18 May 1940, the north-south component: 0.32 g at its peak, 2 s in, the first 12 s of it. A Path Time Series of its accelerations shakes the ground under the whole structure through a Load Pattern's UniformExcitation type, and Run Analysis follows it step by step, 0.02 s at a time, a transient analysis with Newmark's average acceleration. The structure's own weight is its mass. Damping is Rayleigh's, 5% of critical at two frequencies that bracket the modes that matter. Ground motion scale makes the record stronger or weaker, Duration takes more or less of it.
What it shows
The building sways along the shaking, more the higher up, its top 125 mm off at the most, 4.5 s in; the iso-surfaces on the slabs show each floor moving as one. Add storeys and it sways slower and further.
The moment it moves the most, and the record up to then.
