# Concrete Silos: Failures, Design Issues and Repair/Strengthening Methods
## 2 Failure of Reinforced Concrete Silos
### Material Design Factors and the Failure of Reinforced Concrete Structures
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Grain** & **Moisture** & \multicolumn{2}{c}{**Angle of**} & \multicolumn{2}{c}{**Pressure Ratio**} \\  & **Content** & **Internal Friction** & **Measured** & \multicolumn{2}{c}{**Calculated _kf._**} \\  & **w.b. (\%)** & \(\phi\) **(\({}^{\circ}\))** & **Ks** & **Eurocode 1** & **Jaky** \\ \hline \multirow{4}{*}{Barley} & 10 & 27.8 \(\pm\) 0.4 & 0.45 \(\pm\) 0.02 & 0.59 & 0.48 \\  & 12.5 & 28.5 \(\pm\) 0.5 & 0.47 \(\pm\) 0.03 & 0.56 & 0.47 \\  & 15 & 31.2 \(\pm\) 0.3 & 0.43 \(\pm\) 0.02 & 0.50 & 0.43 \\  & 17.5 & 30.6 \(\pm\) 1.0 & 0.45 \(\pm\) 0.03 & 0.54 & 0.43 \\  & 20 & 33.2 \(\pm\) 0.5 & 0.39 \(\pm\) 0.03 & 0.51 & 0.40 \\ \hline \multirow{4}{*}{Corm} & 10 & 26.7 \(\pm\) 0.6 & 0.48 \(\pm\) 0.04 & 0.60 & 0.49 \\  & 12.5 & 31.7 \(\pm\) 0.5 & 0.40 \(\pm\) 0.03 & 0.52 & 0.42 \\ \cline{1-1}  & 15 & 32.0 \(\pm\) 1.4 & 0.36 \(\pm\) 0.05 & 0.51 & 0.41 \\ \cline{1-1}  & 17.5 & 33.4 \(\pm\) 0.8 & 0.34 \(\pm\) 0.03 & 0.50 & 0.40 \\ \cline{1-1}  & 20 & 33.6 \(\pm\) 1.5 & 0.30 \(\pm\) 0.05 & 0.51 & 0.39 \\ \hline \multirow{4}{*}{Oat} & 10 & 22.1 \(\pm\) 1.1 & 0.49 \(\pm\) 0.03 & 0.67 & 0.57 \\  & 12.5 & 22.4 \(\pm\) 0.9 & 0.44 \(\pm\) 0.04 & 0.68 & 0.56 \\ \cline{1-1}  & 15 & 24.0 \(\pm\) 0.5 & 0.45 \(\pm\) 0.03 & 0.64 & 0.54 \\ \cline{1-1}  & 17.5 & 23.9 \(\pm\) 1.0 & 0.40 \(\pm\) 0.03 & 0.66 & 0.54 \\ \cline{1-1}  & 20 & 26.4 \(\pm\) 1.7 & 0.41 \(\pm\) 0.06 & 0.63 & 0.50 \\ \hline \multirow{4}{*}{Wheat} & 10 & 25.7 \(\pm\)0.3 & 0.44 \(\pm\)0.02 & 0.62 & 0.51 \\ \cline{1-1}  & 12.5 & 26.2 \(\pm\) 0.4 & 0.38 \(\pm\) 0.01 & 0.61 & 0.50 \\ \cline{1-1}  & 15 & 27.0\(\pm\) 0.5 & 0.34 \(\pm\) 0.02 & 0.60 & 0.49 \\ \cline{1-1}  & 17.5 & 33.0 \(\pm\) 1.0 & 0.31 \(\pm\) 0.02 & 0.50 & 0.40 \\ \cline{1-1}  & 20 & 35.5 \(\pm\) 0.5 & 0.35 \(\pm\) 0.01 & 0.46 & 0.37 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Relationship between the bulk grain coefficient of internal friction and the moisture content for oat, corn, and barley [49]. Figure 1: Relationship between the moisture content and the coefficient of internal friction for wheat grain bulk [49]. The impact of bulk grain abrasion-induced concrete surface wear in silos can be mitigated. However, the mitigation of these risks is fundamentally dependent on the determination of the types of bulk solids that would be stored in the silos. For silos constructed to store specific types of bulk solids, the risks could be mitigated by the insertion of the sacrificial plates and the liners [47]. On the downside, it might not be possible to mitigate the risk of bulk grain abrasion in multi-purpose silo structures during the design phase. The lack of complete information concerning the intended purpose of the silos has significant consequences in the course of the useful life of the silo structure. In brief, the periodical wear and tear of the hopper walls could have catastrophic effects on the general integrity of the silo. On the downside, these factors have been under-appreciated in the silo design codes. A review of the four commonly used design codes namely the American Society of Agricultural Engineers ANSI/ASAE EP433 DEC1988 (R2011), American Concrete Institute ACI 313-97, British Standard BS EN 1991-4:2006, Australian Standard AS 3774-1996 [1] confirmed that the issue of bulk grain abrasion was excluded. The only related conditions considered in the codes were the flow types, loading, and discharge. On the downside, addressing material-related and bulk grain-related factors remains a challenge considering that that various contractors and suppliers are involved in the construction of the silos. The risks could be mitigated by working with qualified suppliers, regular inspections, and periodical review and inspections of the silo structures before the completion of the construction.