# A Review of the Performance of Infilled RC Structures in Recent Earthquakes
## 4 Case Study
### Assessment of Possible Strengthening Interventions  
The selection of the strengthening technique and the level of intervention is a rather complex procedure because many factors of different nature come into play. The fundamental parameters governing the structural response of the building when submitted to seismic actions are stiffness strength and ductility [52]. In addition, some factors affect this process, such as socio-economic issues, cost-benefit aspect and importance of the building, work duration, conditioning of the utilisation of the structure, functionality and compatibility with the intervention and the original architecture of the building [53]. In any case, selecting the strengthening strategy to adopt and its implementation should be developed based on the results of a preliminary structural assessment. The strengthening plan can be classified according to these two major groups [52], namely:  
Global structural system intervention techniques: Most situations are less costly than the intervention in all structural members. Especially if these types of intervention require temporary interdiction of the building, demolition and/or reconstruction of non-structural elements such as masonry infill walls or false ceilings. The most well-known, economics and efficient global strengthening techniques are: RC structural shear walls; steel braces with and without energy dissipation (shear link); seismic isolation; mass reduction or another technique including tuned mass; and liquid dampers or a hybrid combination of active and passive energy-dissipation device. Member intervention technique: this type of strategy aims to increase the deformation capacity of deficient components to not reach their limit state as the building response at the required level. Some structural elements do not have the adequate strength, stiffness or deformation capacity to satisfy the strengthening objectives. Members without good strength, stiffness and/or ductility can be strengthened using various types of techniques. The most familiar member interventions are: RC jacketing, steel jacketing, CFRP jacketing, injection of cracks, epoxy resin injections, shotcrete and others. This strategy tends to be  
Figure 28: Non-linear dynamic analysis results: Maximum inter-storey drift ratio (**a**) longitudinal direction and (**b**) transverse direction. the most economical approach to strengthening when only a few buildings' components are inadequate. Four types of strengthening solutions were tested to improve the seismic behaviour of the building under study: RC jacketing of the ground floor columns (solution 1), the addition of RC shear walls at the ground floor (solution 2) and the addition of steel braces without (solution 3) and with shear links (solution 4). Their seismic design was performed with the primary purpose of fixing/eliminating the vertical stiffness irregularity and by taking into account the stiffness of each infill wall given by the [PERSON] proposal [47]. One of the strengthening techniques proposed to the building under study is the RC column jacketing (strengthening solution 1) of the ground floor columns. The SeismoStruct [12] can consider RC jacketing columns by assuming the initial section and the upgrade section (considering the disposition of the longitudinal reinforcement bars, confinement provided by the transversal reinforcement). The software allows for using elements with lumped-plasticity (with a fixed length, so-called plastic-hinge). Fibre discretisation was adopted to represent the behaviour at the section level, where each fibre is associated with a uniaxial stress-strain law. An increment dimension of all the columns located at the ground floor dimension was assumed to be about 40 cm and 20 cm, in the longitudinal and transverse direction, respectively. The numerical model takes into account the jacketing material mass and the stiffness during the analysis. The new cross-sections of these columns are designed according to Eurocode 2 [53] and Eurocode 8 [54].