As a structure is a system of an interconnected member meant to carry an externally applied load, it is important to identify every type of action/load imposed on. These loads are can be in the form of forces, moments, acceleration, temperature, and/or settlement.

Depending on the international code/standard to be used, the minimum loads that need to be applied to buildings, bridges or other structures have to be specified accordingly.

Here let us see how these loads are considered according to Eurocode [EN] and later on coming posts,we do the same for other codes including ACI318 and ASCE 7-10.

EN 1990, informally Eurocode 0, classifies action [F] based on different factors. these are

  • Variation in time

Based on the time duration whereby the load is applied on a structure, action can be classified as:

              –  Permanent Action (G):  –loads due to self-weight of structural, and non-structural members, fittings and

                 fixed equipment, prestressing force, water, and soil pressure.

             –  Variable Action (Q): loads due to imposed floor loads, snow loads, wind loads, and action due to traffic

             –  Accidental Action (A): loads due to explosions, fire, and impacts from vehicles.

             –  Seismic Action (AE): is a load-induced on structures as a result of ground motion.

Well, while classifying action on structures based on the time duration where they are applied on, one has to ask a question, So for how long the building is serviceable? Of course, this query had already addressed on EN 1990, Table 2.1.

The answer to the above question gets more crucial in dealing with earthquake-resistant building design.

  •  Origin

          –  Direct Action: loads applied directly to the structure in contact.

          – Indirect Action: loads applied indirectly to the structure including settlement of supports, and temperature effect.

  •  Nature of structural response

            –  Static Action: actions/loads that does not cause significant acceleration of the or structural members.

           – Dynamic Action: actions/loads that cause significant acceleration of the or structural members.

EN1990 provides principles that are common for structures of diffent type and material and the section on the structural analysis provides guidance on the modeling of static action, dynamic action and fire actions

  •  Spatial variation

          –  Fixed Action: action that has a fixed distribution and position over the structure or structural member such that the magnitude and direction of the action are determined unambiguously for the whole structure or structural member if this magnitude and direction are determined at one point on the structure or structural member.

          – Free Action: action that may have various spatial distributions over the structure.

Furthermore, the permanent load self-weight represented by, Gk provided that the variability of G is small and the statical distribution not known can be calculated on the basis of the nominal dimension. If not G is used as Gk,supp or Gk,inf  as upper and lower values, respectively.

Likewise, variable action has also four representative values, including:

  •   Characteristic value, Qk
  •   Combination value, Ψ0Qk
  •   Frequent value, Ψ1Qk
  •   Quasi-permanent value, Ψ2Qk

This post will continue soon on a related topic of the design situation and load combination as per EN1990.

If you are new to Eurocode refer to this post.

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