Question 6.8: Determine the design seismic force on the parapet of the hea......
Determine the design seismic force on the parapet of the health care facility in Example 6.7.
Use Flowchart 6.10 to determine the seismic force on the parapet.
1. Determine S_{DS} , S_{D1} and the SDC.
The design accelerations and the SDC are determined in Example 6.7.
The parapet is assigned to SDC C, which is the same SDC as the building to which it is attached (13.1.2).
2. Determine the component amplification factor a_p and the component response modification factor R_p from Table 13.5-1 for architectural components.
Assuming that the parapet is not braced, a_p = 2.5 and R_p = 2.5 from Table 13.5-1.
3. Determine component importance factor I_p in accordance with 13.1.3.
Since the parapet does not meet any of the three criteria that require I_p =1.5, then I_p =1.0 .
4. Determine the horizontal seismic design force F_p by Eq. 13.3-1.
F_{p}={\frac{0.4\,a_{p}S_{D S}W_{p}}{\left\lgroup\frac{R_{p}}{I_{p}}\right\rgroup}}\left\lgroup1+2{\frac{z}{h}}\right\rgroupAssuming that the thickness of the parapet is 8 in. and that normal weight concrete is utilized, W_p = 8×150 /12 =100 psf.
Since the parapet is attached to the top of the structure, z / h =1.
Thus,
F_{p}={\frac{0.4\times2.5\times0.45\times100}{\left\lgroup{\frac{2.5}{1.0}}\right\rgroup}}\bigl(1+2\bigr)=54 psf
Minimum F_p = 0.3S_{DS} I_pW_p =13.5 psf
Maximum F_p =1.6S_{DS} I_pW_p = 72.0 psf
The 54 psf seismic load is applied to the parapet as shown in Figure 6.9.
