Design the columns for each of the building frames shown in Figs. 2.79 (a) and (b) for minimum weight such that the natural frequency of vibration is greater than \(50 \mathrm{~Hz}\). The mass of the floor \((m)\) is \(2000 \mathrm{~kg}\) and the length of the columns \((l)\) is \(2.5 \mathrm{~m}\). Assume that the columns are made of steel and have a tubular cross section with outer diameter \(d\) and wall thickness \(t\).

Figure 2.79:-

Transcribed Image Text:

EI x El W W b f b EI (a) EI - El EI (b) -El FIGURE 2.79 Building frame.