# Seismic Reinforcement of a R.C. School Structure with Strength Irregularities throughout External Bracing Walls

^{1}

^{2}

^{*}

## Abstract

**:**

## 1. Introduction

^{2}/level. A large number of thin r.c. columns, together with a set of short columns at the top of the ground floor (Figure 3) are seismically vulnerable. Original drawings are available (Figure 4, Figure 5 and Figure 6). Poor quality of the concrete is another relevant and emblematic aspect of seismic vulnerability of the building. In this sense, the considered example represents a typical situation of r.c. constructions that must be urgently enforced.

## 2. Analysis before Intervention

- (i)
- Evaluation of shear behavior (brittle mechanism).
- (ii)
- Evaluation of compression-bending behavior (ductile mechanism).

## 3. Results of analysis

_{R}) of the unreinforced state was estimated, with the following formulas:

_{C}refers more specifically to the acceleration to the bedrock that determines severe damage and therefore a loss of structural resistance; PGA

_{D}is the acceleration value with the probability of exceeding 10% in 50 years (return period 712 years);

_{R}

_{C}is the return period of the structure before intervention, and T

_{R}

_{D}is the return period associated at the ultimate limit state (712 years).

_{R}) of the earthquake.

_{R}(Figure 15) confirmed the sensitivity of the structure to the variation in distribution of the material, with lower risk for Case 1 and higher risk for Case 2, with respect to uniform distribution of the concrete strength.

## 4. Seismic Retrofitting

## 5. Discussion and conclusions

## Acknowledgments

## Author Contributions

## Conflicts of Interest

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**Figure 3.**Details of seismic vulnerability: (

**a**) slender columns close to a double height spacing; (

**b**) squat element (brittle shear force) in r.c. columns.

**Figure 9.**Pushover capacity curves in X (

**a**) and Y (

**b**) direction, with “uniform” pattern load distribution.

**Figure 11.**Extreme distributions of material irregularity: (

**a**) CASE 1 (X direction); (

**b**) CASE 2 (Y direction).

**Figure 15.**Seismic risks index for (

**a**) reference return period and (

**b**) peak ground acceleration (PGA).

**Figure 17.**Phases of the intervention in A pavilion: (

**a**) Micropiles anchoring, before casting of the concrete foundation; (

**b**) Demolition of the slab to ensure the connectivity of the opposing bracing walls; (

**c**) Insertion of the steel reinforcing with profiles HEB100.

Material | fc (MPa) | Ec (MPa) | fy (MPa) |
---|---|---|---|

Concrete | 248 | 28,904 | - |

Steel | - | - | 3699 |

Model | Mode | T (s) | Mx | My |
---|---|---|---|---|

Rigid floor | 1 | 0.450 | 0.78 | - |

2 | 0.445 | - | 0.63 | |

Flexible floor | 1 | 0.494 | - | 0.70 |

2 | 0.445 | 0.37 | 0.77 |

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**MDPI and ACS Style**

Sassu, M.; Puppio, M.L.; Mannari, E.
Seismic Reinforcement of a R.C. School Structure with Strength Irregularities throughout External Bracing Walls. *Buildings* **2017**, *7*, 58.
https://doi.org/10.3390/buildings7030058

**AMA Style**

Sassu M, Puppio ML, Mannari E.
Seismic Reinforcement of a R.C. School Structure with Strength Irregularities throughout External Bracing Walls. *Buildings*. 2017; 7(3):58.
https://doi.org/10.3390/buildings7030058

**Chicago/Turabian Style**

Sassu, Mauro, Mario Lucio Puppio, and Eleonora Mannari.
2017. "Seismic Reinforcement of a R.C. School Structure with Strength Irregularities throughout External Bracing Walls" *Buildings* 7, no. 3: 58.
https://doi.org/10.3390/buildings7030058