Table 4: Clamping options for 0/90/0/90 hypar shells with central cutouts having ratio 0.2.

Number of sides to be clampedclamped edgesImprovement of frequencies with respect to simply supported shellsMarks indicating the efficiencies of clamping

0Simply supported no edges clamped (SSSS)0

(a) Along (CSSS)Slight improvement13
(b) along (SSCS)Slight improvement13
(c) along (SSSC)Slight improvement13
2(a) Two alternate edges (CSCS, SCSC)Good improvement28
(b) Two adjacent edges (CSSC, CCSS)Marked improvement82
33 edges excluding CSCCRemarkable improvement and frequency becomes almost equal to that of fully clamped shells94
3 edges excluding CCSC92
3 edges excluding CCCS93
4All sides (CCCC)Frequency attains a maximum value100