Imposed loads of buildings EN1991-1-1

Imposed loads on buildings are those arising from occupancy. Values given in Eurocode 1 Part 1-1 (EN1991-1-1) Section 6, include:

• normal use by persons;
• furniture and movable objects (e.g. movable partitions, storage, the contents of containers);
• vehicles;
• anticipating rare events, such as concentrations of persons or of furniture, or the moving or stacking of objects which may occur during reorganization or redecoration.

The imposed loads can be modelled by uniformly distributed loads, line loads or concentrated loads or combinations of these loads.

For the determination of the imposed loads, floor and roof areas in buildings should be sub-divided into categories according to their use.

Heavy equipment (e.g. in communal kitchens, radiology rooms, boiler rooms etc) are not included in the loads given in this Section. Loads for heavy equipment should be agreed between the client and/or the relevant Authority.

For the design of a floor structure within one storey or a roof, the imposed load shall be taken into account as a free action applied at the most unfavourable part of the influence area of the action effects considered.

Where the loads on other storeys are relevant, they may be assumed to be distributed uniformly (fixed actions).

To ensure a minimum local resistance of the floor structure a separate verification shall be performed with a concentrated load that, unless stated otherwise, shall not be conlbined with the uniformly distributed loads or other variable actions.

Imposed loads from a single category may be reduced according to the areas supported by the appropriate member, by a reduction factor α_A.
α_A may be applied to the q_k values for imposed loads for floors and for accessible roofs, Category I.
The general method is : (EN1991-1-1 §6.3.1.2(10))
where:

• α_A ≥ 0.6 for categories C and D,
• Ψ₀ is the factor according to Eurocode 0 Annex A1 Table A1.1,
• A₀ = 10.0m²,
• A is the loaded area.

For the design of columns and walls, the imposed load should be placed at all unfavourable locations.
NOTE: The National Annex may introduce further simplifying rules. It is recommended that the maximum axial force may be calculated assuming the total imposed load on the floor of each story to be uniformly distributed.

Where imposed loads from several storeys act on columns and walls, the total imposed loads may be reduced by a factor α_n.
The general method is : (EN1991-1-1 §6.3.1.2(11))
where:

• n is the number of storeys (> 2) above the loaded structural elements from the same category.
• Ψ₀ is the factor according to Eurocode 0 Annex A1 Table A1.1,

The coefficients α_A and α_n are not to be taken into account simultaneously.

When the imposed load is considered as an accompanying action, in accordance with Eurocode 0, only one of the two factors Ψ (Eurocode 0, Table A1.1) and α_n (EN1991-1-1 §6.3.1.2 (11)) shall be applied.

The loaded areas shall be designed by using characteristic values q_k (uniformly distributed load) and Q_k (concentrated load).

NOTE: Values for q_k and Q_k are given in Table below.
Where a range is in this table, the value may be set by the National annex.
You can use our software to find the loads according to your country.
The recommended values, intended for separate application, are underlined.
q_k is intended for determination of effects and Q_k for local effects.
The National annex may define different conditions of use of this Table.

Where necessary q_k and Q_k should be increased in the design (e.g. for stairs and balconies depending on the occupancy and on dimensions).

For local verifications a concentrated load Q_k acting alone should be taken into account.

The concentrated load shall be considered to act at any point on the floor, balcony or stairs over an area with a shape which is appropriate to the use and form of the floor.
NOTE: The shape may normally be assumed as a square with a width of 50 mm.

Where floors are subjected to multiple use, they shall be designed for the most unfavourable category of loading which produces the highest effects of actions (e.g. forces or deflection) in the member under consideration.

Provided that a floor allows a lateral distribution of loads, the self-weight of movable partitions may be taken into account by a uniformly distributed load q_k which should be added to the imposed loads of floors obtained from Table above. This defined uniformly distributed load is dependent on the self-weight of the partitions as follows:

• for movable partitions with a self-weight ≤ 1kN/m wall length: q_k =0,5 kN/m²;
• for movable partitions with a self-weight > 1kN/m and ≤ 2kN/m wall length: q_k =0,8 kN/m²;
• for movable partitions with a self-weight > 2kN/m and ≤ 3kN/m wall length: q_k =1.2 kN/m²;

• the locations and directions of the partitions;
• the structural form of the floors.

The dynamic effects should be considered if appropriate.

Loads in industrial areas should be assessed considering the intended use and the equipment which is to be installed.
Where equipment such as cranes, moving machinery etc, are to be installed the effects on the structure should be determined in accordance with Eurocode 1 Part 3.

Actions due to forklifts and transport vehicles should be considered as concentrated loads acting together with the appropriate imposed distributed loads.
See Eurocode 1 Part 1-1 :

• §6.3.2.3 for more informations about actions induced by forklifts.
• §6.3.2.4 for more informations about actions induced by transport vehicles.
• §6.3.2.5 for more informations about actions induced by special devices for maintenance.

The load model which should be used is a single axle with a load Q_k with 1800mm of spacing between wheels axis and a uniformly distributed load q_k.
The axle load should be applied on two square surfaces with a 100mm side for category F and a 200mm side for Category G in the possible positions which will produce the most adverse effects of the action.
The characteristic values for q_k and Q_k are given in Table below.
NOTE: q_k is intended for determination of general effects and Q_k for local effects.
The National annex may define different conditions of use of this Table.

For roofs separate verifications shall be performed for the concentrated load Q_k and the uniformly distributed load q_k, acting independently.

On roofs (particularly for category H roofs), imposed loads need not be applied in combination with either snow loads and/or wind actions.

The characteristic values of the line load q_k acting at the height of the partition wall or parapets but not higher than 1,20m should be taken from Table below.

For areas susceptible to significant overcrowding associated with public events e.g. for sports stadia, stands, stages, assembly halls or conference rooms, the line load should be taken according to category C5.