# A Site-Specific Response Analysis: A Case Study in Hanoi, Vietnam
## 2 An Insight of the Vietnamese Seismic Design Code TCVN 9386: 2012  
The TCVN 9386: 2012 was developed based on EC-8. However, there were some significant changes [4] to conform with the local Vietnamese conditions. Firstly, the seismic map has been developed from the data obtained from Vietnam Institute of Geophysics (VIG) [16] as shown in Figure 2. Secondly, the importance factors and importance classes in TCVN 9386: 2012 are slightly different from those of EC-8. In TCVN 9386: 2012, there were five importance classes with importance factors ranged from 0.75 to the value corresponding to the possible maximum acceleration. Note that there is no required earthquake resistance for the final importance class (i.e., class IV) in the Vietnamese design code, whereas the EC-8 is classified into four importance classes with importance factors ranged from 0.8 to 1.4. The importance classes and importance factors specified by EC-8 and TCVN 9386: 2012 are listed in Tables 1 and 2, respectively. Thirdly, as the strongest earthquake regions have a magnitude greater than 5.5 on the local magnitude scale and lack data to establish the spectral curves, the TCVN 9386: 2012 used only the type 1 elastic response spectra in two types of EC-8 as the design response spectrum for all regions in Vietnam. Figure 3a shows the detailed type 1 elastic response spectra of EC-8 or the design response spectrum in TCVN 9386: 2012. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Importance Class** & **Buildings** & **Recommended Importance Factor, \(\gamma\)1** \\ \hline I & Building of minor importance for public safety, e.g., & 0.8 \\  & agricultural building, etc. & 1.0 \\ II & Ordinary building, not belonging in the other categories & 1.2 \\ III & Building whose seismic resistance is of importance in & 1.2 \\  & view of the consequences associated with a collapse, e.g., & 1.4 \\  & schools, assembly halls, cultural institutions, etc. & \\  & Building whose integrity during earthquakes is of vital & \\ IV & importance of civil protection, e.g., hospitals, fire & 1.4 \\  & stations, power plants, etc. & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Importance class and recommended importance factors values in Eurocode 8 (EC-8) [15]. Figure 2: Ground acceleration map for (**a**) Vietnam [4] and (**b**) Hanoi. The horizontal elastic response spectrum \(S_{e}(T)\) is determined by the following expressions:  
\[0\leq T\leq T_{\rm B}:\ S_{\rm e}(T)=a_{\rm g}\cdot S\cdot\left[1+\frac{T}{T_{\rm B }}\cdot(\eta\cdot 2.5-1)\right] \tag{1}\]  
\[T_{\rm B}\leq T\leq T_{\rm C}:\ S_{\rm e}(T)=a_{\rm g}\cdot S\cdot\eta\cdot 2.5 \tag{2}\] \begin{table}
\begin{tabular}{c c c} \hline \hline
**Importance Class** & **Buildings** & **Recommended Importance Factor, \(\gamma_{1}\)** \\ \hline Special & The building has special importance, not allowing any damage by the earthquake. & Designed with maximum possible acceleration \\  & The building has vital importance for the protection of & \\ I & the community, its function must not be interrupted & 1.25 \\  & during the earthquake. & \\  & The building has an importance in preventing & \\ II & earthquake consequences, if collapsed causing great loss & 1.0 \\  & of life and property. & \\ III & The building does not belong to importance classes: & \\  & special, I, II, and IV. & \\ IV & The building has minor importance for the safety of & 0.75 \\  & human life. & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Importance class and recommended importance factors values in TCVN 9386: 2012 [14]. Figure 3: Elastic response spectra (5% damping) [4]: (**a**) general type and (**b**) for ground types A to E.  
\[T_{\rm C}\leq T\leq T_{\rm D}:\ S_{\rm e}(T)=a_{\rm g}\cdot S\cdot\eta\cdot 2.5 \cdot\left[\frac{T_{\rm C}}{T}\right] \tag{3}\]  
\[T_{\rm B}\leq T\leq T_{\rm C}:\ S_{\rm e}(T)=a_{\rm g}\cdot S\cdot\eta\cdot 2.5 \tag{4}\]  
where:  
\(S_{e}(T)\): is the elastic response spectrum. \(T\): is the vibration period of a linear single-degree-of-freedom system.