## 8 Comparing the Seismic Demand Obtained from the Different Codes  
A comparison is presented in this section to check the consequences of adopting one or the other of the four different codes referred to by the Lebanese standard, namely PS-92, UBC, IBC and EC8. For this purpose, a series of linear analyses have been conducted on the same archetype given in Figure 11, the fundamental period of which is T = 0.39 s. This allows for an objective weighting of the demand imposed on a structure with a fundamental period that typically places acceleration demands on the plateau of the design spectra (or in its vicinity), thereby allowing seismic demands to be high. Firstly, MRSAs on the archetype have been performed, with reference to the elastic spectra given by the four codes and to the \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Ground Type**} & \multirow{2}{*}{**X Acceler.**} & \multicolumn{3}{c}{**Rood Displacements**} & \multicolumn{3}{c}{**Total Base Shear**} \\ \cline{3-6}  & & & **Abs. Diff. (\%)** & **Mean (\%)** & **Abs. Diff. (\%)** & **Mean (\%)** \\ \hline \multirow{8}{*}{A} & 1 & 4.8 & & 3.7 & \\  & 2 & 3.4 & & 3.6 & \\  & 3 & 1.9 & & 2.9 & \\  & 4 & 2.9 & 3.6 & 3.4 & 4.3 \\  & 5 & 7.8 & & 2.3 & \\  & 6 & 2.2 & & 5.7 & \\  & 7 & 2.3 & & 8.8 & \\ \hline \multirow{8}{*}{B} & 1 & 3.3 & & 3.4 & \\  & 2 & 9.6 & & 5.0 & \\  & 3 & 1.9 & & 2.9 & \\  & 4 & 3.2 & 4.1 & 2.5 & 3.9 \\  & 5 & 1.5 & & 1.6 & \\  & 6 & 5.3 & & 7.5 & \\  & 7 & 3.8 & & 4.3 & \\ \hline \multirow{8}{*}{C} & 1 & 1.7 & & 0.1 & \\  & 2 & 10.5 & & 4.9 & \\  & 3 & 2.1 & & 2.8 & \\  & 4 & 9.9 & 4.7 & 11.4 & 4.1 \\  & 5 & 0.8 & & 3.5 & \\  & 6 & 4.3 & & 1.9 & \\  & 7 & 3.8 & & 4.3 & \\ \hline \multirow{8}{*}{D} & 1 & 3.3 & & 3.5 & \\  & 2 & 1.5 & & 7.0 & \\  & 3 & 5.2 & & 4.0 & \\ \cline{1-1}  & 4 & 5.8 & 4.6 & 1.5 & 3.3 \\ \cline{1-1}  & 5 & 5.8 & & 2.7 & \\ \cline{1-1}  & 6 & 9.9 & & 3.7 & \\ \cline{1-1}  & 7 & 0.4 & & 0.7 & \\ \hline \multirow{8}{*}{E} & 1 & 1.4 & & 5.9 & \\ \cline{1-1}  & 2 & 9.3 & & 1.0 & \\ \cline{1-1}  & 3 & 6.9 & & 2.4 & \\ \cline{1-1}  & 4 & 2.7 & 4.6 & 12.8 & 4.9 \\ \cline{1-1}  & 5 & 5.1 & & 10.6 & \\ \cline{1-1}  & 6 & 1.4 & & 1.0 & \\ \cline{1-1}  & 7 & 5.7 & & 0.4 & \\ \hline \hline \end{tabular}
\end{table} 
Table 11: Summary of the results of the non-linear time-history analyses. categories of site/soil A, B, C, D and E. The two variables assessed are roof displacements and base shear force. The results obtained through the MRSA for the different codes are presented in Figure 12. Both topographical factors \(\tau=1\) and \(\tau=1.4\) are considered for the PS92 spectra. Figure 12 shows that, in general, and as expected, soft soils impose higher displacement and force demands. Some exceptions are found for S2 and S3 soils when referring to the PS92 standard, and for E soils and C soils when referring to IBC and EC8 spectra, respectively. For very stiff soils (PS92-S0, UBC-SA, IBC-SA, and EC8-SA), the values of the roof displacement are relatively uniform between the different codes, with a maximum difference of 31.09% between the highest (EC8-SA) and the lowest (PS92-S0, \(\tau=1\)) values. For very soft soils (PS92-S3, UBC-SE, IBC-SE, and EC8-SE), the highest difference (89.05%) is observed once again between the results relevant to PS-92 (\(\tau=1\)) and EC8 (see Figure 12a). Similarly, when the base shear force is concerned, a maximum difference of 31.52% and of 90% was found, respectively, for very stiff soils and for soft soils between PS92 (\(\tau=1\)) and EC8. When a topographic factor \(\tau=1.4\) is considered in the PS92 spectra, the difference between the roof displacements obtained with EC8 and PS92 lowers to 6.29% for very stiff soils and to 35.03% for soft soils. Similarly, the difference between base shear forces lowers to 6.77% for very stiff soils and to 35.55% for soft soils. It should be noted, however, that \(\tau=1.4\) is the maximum value of the topographical factor, provided by PS92 for very high slopes of the site.