Modern Requirements for Strengthening and Upgrading Existing Buildings in Seismic Zones

Many existing buildings around the world do not meet the current earthquake resistance codes. Therefore, it requires strengthening and upgrading of such buildings, which may involve adding new floors or other structural elements. Design of such buildings is based on empirical dependences or numerical dynamic analysis. However, in both cases, the results often do not account for the building’s current condition, as many of these structures may have sustained damage and require maintenance or repairs, which could alter the original material and structural properties, making the dynamic parameters, used in design, unreliable. In some cases, these parameters may not correspond to the requirements of modern design codes and standards. As a result, the building after strengthened and/or upgrading may have some problems related to the properties of the new constructive scheme, which is based on unreliable parameters. This increases the probability of complaints and legal claims from building owners. To encourage construction contractors and investors to strengthen existing buildings, some countries have developed national programs. For example, in Israel, the National Outline Plan (TAMA-38) promotes the strengthening and upgrading of existing buildings by allowing for the addition of new areas (floors or other parts). Experimental measurement of buildings’ dynamic parameters at each stage of strengthening and upgrading allows for verification of the desired effects. This study demonstrates the application of this approach to an existing four-story reinforced concrete residential building. The research includes both the building’s experimental investigation and numerical analysis, with a comparison of the results. The findings indicate that the building should be designed using experimentally updated parameters. This approach results in a more reliable design, significantly reducing the number of complaints and legal claims.