Determining Wind Loads for Canopy Roof Structures According to EN 1991-1-4

Technical Article on the Topic Structural Analysis Using Dlubal Software

  • Knowledge Base

Technical Article

If a canopy roof (for example, a filling station roof) should be designed, a load determination with regard to Section 7.3 of EN 1991‑1‑4 is required. This article shows the design of a slightly inclined troughed roof, with an example.

Determining Coefficients

To determine the load, the force coefficients cf and the entire pressure coefficients cp,net according to Table 7.6 to Table 7.8 should be used. If there is an obstruction below or immediately next to the roof (for example, stored goods), the degree of the obstruction has to be determined and interpolated in the tables between ϕ = 0 (unobstructed) and ϕ = 1 (totally obstructed).

To determine the resulting entire pressure coefficient, a classification of surfaces is performed similar to that of closed buildings. This only applies to the design of the roof covering and its anchorage elements.

Position and Form of Resulting Wind Power

To design the supporting structure, it is necessary to apply the resulting wind power in the distance of d/4 of the windward side. d is the dimension for the roof surface downwind. Graphic 7.17 displays six possible load arrangements depending on the sign of the force coefficient.

Since the wind load is acting as a surface load and not as a nodal load on the roof covering, and its centroid position amounts to 1/4 of the roof length, it is necessary to find an appropriate load situation that takes this into consideration. Such an eccentric load arrangement leads to a highly loaded stability analysis of possible central supports. One possible load arrangement would be a surface load in the shape of a square parabola, because its center of gravity is situated in 1/4 of the length.

Example: Trough Roof

Length = 15 m
Width = 12 m
Height of valley = 6 m
Roof inclination = -5 °
Wind load = 0.5 kN/m²
No obstruction → ϕ = 0
cf = +0.3 maximum all ϕ
cf = -0.5 minimum ϕ = 0

Resulting Wind Force

RFEM and RSTAB contain the load generators for enclosed buildings with a rectangular ground plan. It can be selected if the load is applied only to the walls, the roof, or the entire building.

Supporting structures for canopy roofs cannot be calculated automatically. However, the load generator with levels can be used after determining the coefficients.

Wind Pressure

Fw,max = cf · qh(ze) · Aref = 0.3 · 0.5 · 15 · 12cos 5° = 27.10 kN

Wind Suction

Fw,min = cf · qh(ze) · Aref = -0.5 · 0.5 · 15 · 12cos 5° = -45.17 kN

Friction forces according to Section 7.5 are not considered in this example.

Largest Load Ordinates of Parabolic Load

Attention is paid only to load positions 2 and 5. Load positions 3 and 6 are not necessary due to the symmetry.

Load Ordinates

q(Pressure) = 27.1123 = 6.775 kN/m = 0.45 kN/m²q(Suction) = -45.17123 = -11.293 kN/m = -0.75 kN/m²

With these load ordinates and using this quadratic equation, if necessary in Excel, the variable load values per x-location can be determined and exported to RFEM or RSTAB.

Author

Dipl.-Ing. (FH) Walter Fröhlich

Dipl.-Ing. (FH) Walter Fröhlich

Product Engineering & Customer Support

Mr. Fröhlich takes care of the processing of user questions in the customer support and is also responsible for the development in the field of steel construction.

Keywords

EN 1991-1-4 Self-supporting roof Wind load Trough roof

Reference

[1]   EN 1991-1-4: Eurocode 1: Actions on structures - Part 1-4: General actions - Wind actions

Downloads

Links

Write Comment...

Write Comment...

  • Views 22662x
  • Updated 11/09/2021

Contact Us

Contact Dlubal

Do you have further questions or need advice? Contact us via phone, email, or chat or find suggested solutions and useful tips on our FAQ page available 24/7.

(267) 702-2815

info-us@dlubal.com

ACI 318-19 Concrete Design in RFEM 6

ACI 318-19 Concrete Design in RFEM 6

Webinar 01/20/2022 2:00 PM - 3:00 PM EST

Online Training | English

Eurocode 3 | Steel Structures According to DIN EN 1993-1-1

Online Training 02/10/2022 8:30 AM - 12:30 PM CET

Event Invitation

NCSEA Structural Engineering Summit

Conference 02/15/2022 - 02/16/2022

Online Training | English

Eurocode 2 | Concrete Structures According to DIN EN 1992-1-1

Online Training 02/25/2022 8:30 AM - 12:30 PM CET

Online Training | English

Eurocode 5 | Timber Structures According to DIN EN 1995-1-1

Online Training 03/17/2022 8:30 AM - 12:30 PM CET

Event Invitation

2022 NASCC: The Steel Conference

Conference 03/23/2022 - 03/25/2022

Event Invitation

International Mass Timber Conference

Conference 04/12/2022 - 04/14/2022

Event Invitation

Structures Congress 2022

Conference 04/21/2022 - 04/22/2022

Considering Construction Stages \n in RFEM 6

Considering Construction Stages in RFEM 6

Webinar 01/13/2022 2:00 PM - 3:00 PM CET

AISC 360-16 Steel Design in RFEM 6

AISC 360-16 Steel Design in RFEM 6

Webinar 12/14/2021 2:00 PM - 3:00 PM EST

Introduction to New RFEM 6

Introduction to the New RFEM 6

Webinar 11/11/2021 2:00 PM - 3:00 PM EST

Timber Structure Design in RFEM 6 and RSTAB 9

Model and Design Timber Structures in RFEM 6 and RSTAB 9

Webinar 11/11/2021 2:00 PM - 3:00 PM CET

Glass Design with Dlubal Software

Glass Design with Dlubal Software

Webinar 06/08/2021 2:00 PM - 2:45 PM

Blast Time History Analysis in RFEM

Blast Time History Analysis in RFEM

Webinar 05/13/2021 2:00 PM - 3:00 PM EST

Timber Structures | Part 2: Design

Timber Beam and Surface Structures | Part 2: Design

Webinar 05/11/2021 2:00 PM - 3:00 PM

Plate and Shell Buckling Utilizing Dlubal Software

Plate and Shell Buckling Utilizing Dlubal Software

Webinar 03/30/2021 2:00 PM - 2:45 PM

CSA S16:19 Steel Design in RFEM

CSA S16:19 Steel Design in RFEM

Webinar 03/10/2021 2:00 PM - 3:00 PM EST

RFEM 5
RFEM

Main Program

Structural engineering software for finite element analysis (FEA) of planar and spatial structural systems consisting of plates, walls, shells, members (beams), solids and contact elements

Price of First License
3,540.00 USD
RSTAB 8
RSTAB

Main Program

The structural engineering software for design of frame, beam and truss structures, performing linear and nonlinear calculations of internal forces, deformations, and support reactions

Price of First License
2,550.00 USD