Decision Making Based on Benefit-Costs Analysis: Costs of Preventive Retrofit versus Costs of Repair after Earthquake Hazards

The reduction of seismic risk through the retrofitting of historic buildings serves catastrophe management. In the application of such measures, actors from the spheres of the passive public, experts, as well as active affected people, are involved. The focus of this work is on planning management in the expert area, with a detailed view on the decision space between goals, means, benefits and costs. Buildings of a typology were modelled, and the models translated using a finite elements software with fibre-based modelling of plasticity. The concept of retrofit elements was developed, in order to connect building surveys, construction management, structural simulations, and costs computation based on devices, all related to these retrofit elements. With a view to the general methodology, in order to compare the costs for repairs to buildings after an earthquake with the costs associated with preventive retrofitting of an undamaged building, several cases were considered: damages on a non-retrofitted building, damages on retrofitted building, retrofitting on an undamaged building, retrofitting on a pre-damaged building, and the subsequent damages in an earthquake for the last two. The innovative part of this research lies in the use of the tension-elongation approach to models of building size. Such an analysis allows not only the description of ways of collapsing and the setting of limit states, but also exactly the specific amount and position of the structural members which fail in certain performance criteria. This type of results can form the basis for interdisciplinary studies, such as economic efficiency studies. The method was applied for early reinforced concrete buildings, which are common in Bucharest, Romania, in a deterministic method which takes into account recorded earthquakes. In conclusion, depending on the size of an earthquake, the timing and extent of the retrofit to be applied differ, if we are to obtain cost savings in preventive retrofitting compared to post-earthquake repair. This is presented through a range of costs curves.