Seismic retrofit of industrial structures with inverted V bracings: influence of the seismic vertical component

The structural configuration of industrial facilities is frequently design in function of equipment requirements and operability conditions, such as the need to guarantee adequate space to infrastructures and to foresee the update of the equipment and components, in order to keep up with the technological evolution. For such a reason, existing industrial facilities usually are characterized by a not optimized structural behavior, in particular for what concern the behavior against the seismic action. A typical example is represent by support structures of heavy equipment for the storage of material, silos or vessels, realized with inverted V shaped braces. Those diagonal elements are frequently used to withstand both the horizontal actions and the vertical loads. In such a way, the braces, being permanently compressed, are more susceptible to buckling phenomena. It should also be noted that such structural configuration can strongly hinder eventual seismic retrofit interventions. In the present paper several strategies for the seismic retrofit of support structures with inverted V shaped braces will be analyzed, evidencing the advantages and disadvantages for each solution. In order to provide a realistic overview of the possible solution, a real industrial facility is deeply analyzed through a consistent set of incremental dynamic analyses.