Seismic response analysis of a new staggered storey isolated structure under mainshock-aftershock sequences

Figures & data

Figure 1. Comparison diagram of the three structures:(a) base isolated structure, (b) inter-storey isolated structure, (c) new staggered storey isolated structure (blank area represents frame, black shaded area represents isolated bearings).

Figure 2. Schematic diagram of the new staggered storey isolated structure.

Table 1. Section size parameters.

Component type	Component floor	Section size(mm)
Frame column	1–10	800 × 800
	11–24	700 × 700
Frame beam	1–24	350 × 750
Connecting beam	1–24	300 × 650

Figure 3. Material stress-strain curve: (a) concrete; (b) steel.

Figure 4. Plastic hinge curve (IO immediate occupancy; LS life safety; CP collapse prevention).

Figure 5. Force-displacement relationship of LRB.

Table 2. Bearing parameters.

Type	Effective diameter $\mathit{D}$(mm)	Vertical stiffness $K_V$(kN·mm^−1)	Equivalent horizontal stiffness $K_{\mathit{eq}}$(kN·mm^−1)	Stiffness before yield $K_u$(kN·mm^−1)	Yield force $Q_d$(kN)	Total rubber thicknes $\mathit{t}$(mm)
LRB800	800	2900	2.05	15.19	106	149
LRB600	600	2100	1.45	11.37	63	112

Table 3. Detailed information of the mainshock-aftershock ground motion sequences.

NO.	Event name	Station name	Mainshock ground motion					Aftershock ground motion
			Mw	PGA (g)	Rjb (kM)	Scale factor	Lowest Useable Frequency (Hz)	Mw	PGA (g)	Rjb (kM)	Scale factor	Lowest Useable Frequency (Hz)
1	Chi-Chi_Taiwan	CHY082	7.62	0.062	36.09	1.590	0.050	6.2	0.031	48.89	5.856	0.1
2	Coalinga	Skunk Hollow	5.77	0.292	11.7	1.0	1.0	5.09	0.138	10.55	1.0	0.375
3	MammothLakes	Long Valley Dam	6.06	0.271	12.56	2.259	0.138	5.69	0.193	14.28	19.068	0.375
4	Northridge	LA – Temple & Hope	6.69	0.183	28.82	2.272	0.2	5.28	0.038	26.42	49.154	0.3
5	Imperial Valley	El Centro Array #3	6.53	0.222	10.79	0.500	0.063	5.01	0.097	15.54	14.616	0.537

Figure 6. Acceleration time history of the mainshock-aftershock earthquake sequence.

Figure 7. Response spectrum curve of mainshock-aftershock sequences.

Table 4. Period comparison before and after isolated.

Modal	Fixed-base structure(s)	New staggered storey isolated structure(s)
1	2.251	3.867
2	2.069	3.856
3	1.905	3.616

Figure 8. Inter-storey displacement of the new staggered storey isolated structure: (a) single mainshock; (b) mainshock-aftershock.

Figure 9. Inter-storey displacement of the fixed-base structure: (a) single mainshock; (b) mainshock-aftershock.

Figure 10. Displacement comparison of staggered isolated bearings under mainshock-aftershock sequences.

Figure 11. New staggered layer isolated structure with different isolated layers: (a)the 1rd floor (base isolated structure), (b) the 3rd floor, (c) the 6rd floor, (d) the 8rd floor.

Figure 12. Base shear at different locations of upper isolated layer.

Figure 13. Base torque at different locations of upper isolated layer.

Figure 14. Inter-layer displacement angle at different locations of upper isolated layer.

Table 5. Stress and deformation of isolated bearings.

Bearing indicators	Compressive Stress (MPa)	Tensile Stress (MPa)	Maximum horizontal deformation(mm)
Single mainshock	19.78	0.75	361
Mainshock and aftershock	19.99	0.79	395

Figure 15. Stress distribution in core tube influences force: single mainshocks (a) and (c); mainshock-aftershocks (b) and (d).

Figure 16. Distribution of frame plastic hinge: single mainshocks (a) and (c); mainshock-aftershocks (b) and (d).

Figure 17. Hysteresis curve of isolated bearing under single mainshock and mainshock-aftershock sequences: (a) the upper isolated layer bearing; (b) the lower isolated layer bearing.

Figure 18. Hysteretic curves of upper and lower isolated layer bearings: (a) single mainshock; (b) mainshock-aftershock.