# Concrete Silos: Failures, Design Issues and Repair/Strengthening Methods
## 3 Design Issues in Reinforced Concrete Silos
### Design Factors
#### 3.1.4 Seismic Activity and Other Natural Phenomenon  
Considering the adverse effects of anthropogenic contamination of the environment, the design of new silos in the US should take into account the stresses introduced by natural phenomena such as storms and cyclones in coastal areas and earthquakes in geologically active areas [71, 72]. The present research is limited on the silo design interventions that have been made to limit the impact of strong winds in the cyclone and hurricane-prone southern states such as Florida, South Carolina, North Carolina, Texas, and Virginia [72]. The lack of relevant data elevates the risk of structural damage given the wind compression pressure, and radial displacements are proportional to the silo eight [9].  
According to [PERSON] [72], the impact of seismic activity on the structural integrity of RC silos is dependent on a key set of parameters, including the state of loading-unloading, and support systems--columns or shear walls. Lateral displacements induced by seismic activity were higher in fully filled silo structures and stiff hopper walls. Therefore, the inclusion of support columns contributed to the risk of structural failure after earthquakes. In place of support columns, shear walls are highly effective. The height of the silo should also be controlled in regions with high seismic activity--a lateral displacement of 4.0-6.5 mm was observed in full silo structures with a height above 10 m [72]. The least displacement was reported in empty silo structures. The repair and strengthening of silo structures are discussed in Section 4.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Type of** & **Unit Weight** & **Angle** & \begin{tabular}{c} **Effective Angle** \\ **of** \\ **Repose** \\ \end{tabular} & \begin{tabular}{c} **Lateral** \\ **of Internal** \\ **Friction** \\ \end{tabular} & \
\begin{tabular}{c} **Max. Flow** \\ **Pressure** \\ **Ratio** \\ \end{tabular} &
\begin{tabular}{c} **Mass. Flow** \\ **Pressure** \\ **Multiplier** \\ **C\({}_{\textbf{o}}\)** \\ \end{tabular} \\  & \(\gamma\)**1** & \(\gamma_{\textbf{u}}\) & \(\varphi_{\textbf{r}}\) & \(\varphi_{\textbf{il}}\) & \(\varphi_{\textbf{iu}}\) & \(K_{\textbf{lv}}\,\lambda_{\textbf{l}}\) & \(K_{\textbf{w}}\,\lambda_{\textbf{u}}\) \\  & **Lower** & **Upper** & **Lower** & **Upper** & **Lower** & **Upper** \\  & **kN/m\({}^{3}\)** & **kN/m\({}^{3}\)** & **Degrees** & **Degrees** & **Degrees** & **Degrees** & **Degrees** \\ \hline Alumina & 10.0 & 12.0 & 27 & 25 & 40 & 0.42 & 0.53 & 1.40 \\ Barley & 7.0 & 8.5 & 20 & 26 & 33 & 0.50 & 0.63 & 1.35 \\ Cement & 13.0 & 16.0 & 28 & 40 & 50 & 0.45 & 0.58 & 1.40 \\ Cement clinker & 15.0 & 18.0 & 33 & 42 & 52 & 0.41 & 0.52 & 1.40 \\ Flour (wheat) & 6.5 & 7.0 & 40 & 23 & 30 & 0.36 & 0.46 & 1.45 \\ Fly ash & 8.0 & 14.0 & 22 & 30 & 35 & 0.41 & 0.52 & 1.45 \\ Iron ore pellets & 19.0 & 22.0 & 35 & 35 & 45 & 0.35 & 0.45 & 1.40 \\ Lime, hydrated & 6.0 & 8.0 & 40 & 35 & 45 & 0.35 & 0.45 & 1.40 \\ Limestone powder & 11.0 & 13.0 & 30 & 40 & 60 & 0.35 & 0.45 & 1.45 \\ Maize & 7.0 & 8.5 & 30 & 28 & 33 & 0.45 & 0.58 & 1.40 \\ Phosphate rock & 16.0 & 19.0 & 27 & 35 & 55 & 0.35 & 0.45 & 1.40 \\ Sand: coarse dry & 14.0 & 17.0 & 30 & 30 & 40 & 0.41 & 0.52 & 1.40 \\ Sand: quartz & 15.0 & 17.0 & 30 & 35 & 40 & 0.35 & 0.45 & 1.40 \\ Slag: granular, dry & 10.5 & 12.0 & 40 & 35 & 38 & 0.36 & 0.47 & 1.40 \\ Soya beans & 7.0 & 8.0 & 23 & 25 & 32 & 0.47 & 0.60 & 1.30 \\ Sugar & 8.0 & 9.5 & 29 & 33 & 38 & 0.45 & 0.58 & 1.40 \\ Wheat & 7.5 & 9.0 & 20 & 26 & 32 & 0.50 & 0.63 & 1.30 \\ \hline \hline \end{tabular}
\end{table}
Table 7: Relationship between lateral pressure, flow, and friction, and type of bulk material [23].