Re: framed system A curtain is a vertical carrier element with a ratio of at least 7 on its long side to its short side. (TDY.3.6.1.1) The carrier system, which does not have any curtains running through all floors, is the "Frame" system. In case there is a curtain in the carrier system, the system is a "Curtain-Framed" system. If all vertical carrier elements in the system are curtains, the system is "Curtain" system. Building Structural System Behavior Coefficients are given in TDY Table 2.5.