HOW WE DESIGN SEISMIC SOLUTIONS?

The Case Study of an Industial Warehouse in Vicenza, Italy

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In a large industrial warehouse with over 300 square meters of surface area, made up from a part of a new construction and a part older.

The customer need is to support the Foam-Sprinkler system in compliance with the local legislation. Distinctive feature: the roof is made fromtiled “gill wings”, so the supporting system for the installation should be fixed on inclined surfaces with reduced thickness.

What is the perfect solution?

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Thanks to the new MQS components, it is possible to design an extremely flexible solution custom tailored and easy to assamble, but especially able to withstand the earthquake effects.

The flexible MQS system has been the same, because the warehouse have tight spaces and many obstacles due to the shape of the roof beams.

There was therefore the need to make decisions directly in the jobsite (with the customer IDROTERME), in relation to the arrangement of the pipes, their dimensions, their encumber. This required a continuing partnership between staff and the company carrying the Hilti technical team (sales engineer and technical department).

Hilti defined all the typical of the supports based on the customer needs.

The non structural element are usually measured using the so-called method of equivalent static lateral forces. In this case, a static force equivalent Fa (seismic force), acting on the element's center of gravity, it is established.

The vibrations of the building and of the elements of the element are taken into account but also the ability to absorb energy by deformation (energy dissipation) using some factors (coefficients).

How we calculate?

Seismic calculation

The calculation of seismic action on the non-structural elements, described within the Italian Seismic Code NTC 2008 is determined through the following formula:

                              Fa = (Sa x Wa) / qa

  • Fa : Horizontal seismic force acting at the non structural-element center of mass in the most unfavorable direction
  • Wa : Element weight
  • Sa : Maximum acceleration, dimensionless compared with the gravity acceleration, that the structural element undergoes during the earthquake and corresponding to the limit state under consideration 
  • qa : Structure Factor of the element

How to define the proper earthquake-resistant support for the facility?

Earthquake-resistant support

 

The seismic support often need to be braced, in order to be sufficiently rigid and counter agents horizontal seismic actions.
For this reason, it is possible to distinguish three basic types of earthquake-resistant supports:
Longitudinal bracing: braces arranged longitudinally to the main direction of the pipe or installation in general (eg.: resistance of the supports horizontal against forces acting along the axis of the pipe)
Cross bracing: braces arranged perpendicularly to the main direction of the pipe or the installation in general (eg .: resistance of the supports horizontal against forces acting transversely of the pipe)
4 ways bracing: structure composed of both longitudinal and lateral braces, therefore able to withstand all of the forces acting on the horizontal plane.

 

It is obviously advantageous set up the braces so that the braces distance is a multiple of the usual same hangers for the static support of the installation system.

THE SOFTWARE TO DESIGN AND BUILD FOR EARTHQUAKES

  • Hilti PROFIS Installation software for modular support systems

    Hilti PROFIS Installation Seismic software

    With the PROFIS Installation Seismic software, structural calculation can be developed in a simple and intuitive way by using Hilti systems for installation. The seismic module of the software allows the design and the analysis for seismic applications in accordance with current regulations. In the case of the industrial warehouse in question, Hilti has participated with the definition of all typological brackets based on the firm's specific requests, multiple inspections has be done, technical advice has be provided and at the end the installers received assistance during the different stages of the brackets assembly.

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