Applies To
	Product(s):	STAAD.Pro
	Version(s):	ALL
	Environment:	ALL
	Area:	Analysis Solutions
	Subarea:	Time History Analysis
	Original Author:	Sye Chakraborty Bentley Technical Support Group

In our research, We want to use a TMD(tuned mass damper) installed on the floor of a building to reduce the response of structure under earthquake. The TMD include a mass(m), a spring(k) and a damper(c). How can I put these three things on the building in STAAD? Thank you very much.

Mass is entered the way you have entered it, using joint forces to represent weight in calculating modes.
Springs to ground are entered through the Support command.
Staad does not have dampers, just modal damping. However, if the TMD has a first frequency much lower than the rest of the structure, then that first mode can be given the damping that you want and the rest of the structure (all of the remaining modes) given a different damping.

STAAD requires mass to be defined in each direction of motion not just in the Y direction.
You may need more modes than the default 6.

If the El Centro data is every 0.01 seconds then there is a 26.88 second integration time span. You may want to stop at a lesser time.
The integration step size, DT, should not be as large as you have entered. Use 0.0016 or less.

CUT OFF MODES 20
CUT OFF TIME 8

DEFINE TIME HISTORY DT 0.0013
TYPE 1 ACCELERATION
READ ELCENTRO.TXT
ARRIVAL TIME
0
DAMPING 0.05

LOAD 1 TIME HISTORY LOAD
SELFWEIGHT Y -1
JOINT LOAD
2 7 TO 10 12 14 16 18 20 FY -957
11 TO 20 FY -1040
JOINT LOAD
21 FY -590
SELFWEIGHT X -1
JOINT LOAD
2 7 TO 10 12 14 16 18 20 FX -957
11 TO 20 FX -1040
JOINT LOAD
21 FX -590
GROUND MOTION X 1 1
PERFORM ANALYSIS