# Seismic Upgrade of an Existing Reinforced Concrete Building Using Steel Plate Shear Walls (SPSW)
## 6 Conclusions  
This paper investigates the seismic retrofit and upgrade of an existing r/c building using SPSWs. SPSWs are able to provide both stiffness and ductility; however, their actual behavior has to be appropriately represented in the numerical model. Additionally, the placement and configuration of the SPSWs is a critical factor concerning their contribution to the anticipated seismic performance of the building.  
Three different options are utilized herein to model SPSWs, and the seismic performance of the retrofitted r/c building is assessed by a number of NLTH analyses. From the results of these analyses, in terms of specific seismic response indices and plastic hinge formations to the members of the building, it is concluded that short-length SPSWs in conjunction with an orthotropic membrane model (OMM) for them provide the best option. As an alternative good option, one may select a finite element model (FEM) instead of the OMM; on the other hand, the equivalent brace model (EBM) is not recommended. Taking into account that discretization by membrane elements in conjunction with orthotropic material properties are common options in all modern structural analysis software, the implementation of an OMM for the SPSW is easy and leads to accurate response results.  
The retrofitted SPSWs r/c building under study exhibits desirable transient and residual interstorey drift characteristics, as well as a substantial increase in base shear and energy dissipation capacity. As a general conclusion and essentially a final suggestion to be made, in the imminent or future revision of modern seismic retrofit codes [3; 35], the option of utilizing SPSWs for seismic upgrading purposes of existing r/c buildings should be  
Figure 19: Principal tensile stresses S11 (in MPa)—Orthotropic Membrane Model (OMM), t = 9.0 mm.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Seismic Motion** & **Von Mises Stress** & **Status** & **S11 (MPa)** & **S22 (MPa)** \\ \hline
1a & 126.0 & Not yield & 221.7 & 4.6 \\
1b & 350.7 & Yield & 272.4 & 6.6 \\
2a & 110.5 & Yield & 239.1 & 4.7 \\
2b & 124.3 & Not yield & 211.0 & 3.9 \\
3a & 158.2 & Not yield & 229.9 & 4.8 \\
3b & 196.8 & Yield & 247.2 & 6.2 \\ \hline \hline \end{tabular}
\end{table}
Table 15: Maximum Von Mises and principal stress to SPSWs, status of the SPSW.  
added. In this sense, both the FEM and OMM options for modeling SPSW can be proposed; nevertheless, the OMM option may be preferred because it represents the tension-field action of the SPSW better than the FEM option. Obviously, the final decision with respect to the configuration of the SPSW strongly depends on the r/c building to be retrofitted.  
Conceptualization, N.B. and G.P.; Methodology, N.B. and G.P.; Software, N.B. and G.P.; Supervision, G.P.; Validation, N.B. and G.P.; Writing--original draft, N.B and G.P.; Writing--review & editing, G.P. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The data that support the findings of this study are available from the authors upon reasonable request.  
The authors declare no conflict of interest.