Structural Calculations for a GRP Gatehouse

Structural Calculations for a GRP Gatehouse


GRP gatehouses and kiosks remain a popular choice for many customers, where their combination of easy installation, minimal maintenance and design flexibility makes them the ideal choice for a wide range of applications in a variety of locations.

The Client

A UK-based manufacturer of gatehouses, kiosks and bespoke enclosures.

The Brief

Our client has a long history of manufacturing gatehouses and enclosures to the highest standards and can point to numerous examples of their products being able to withstand a range of environmental conditions over many years in the field.

Increasingly, however, their customers are seeking even greater levels of assurance as to the suitability of their products. For this reason, they approached Coventive to provide structural calculations to verify the suitability of the proposed gatehouse design and construction.

Our Approach

Identifying the load cases

For this analysis, the following load cases were considered:

  • wind load and snow loads;
  • self-weight and;
  • personnel loads.

Optimising the design

In common with many manufacturers of GRP enclosures, our client had designed the gatehouse based upon the use of a tried and method of construction; consisting of GRP sandwich laminate wall panels incorporating an encapsulated timber frame. The GRP roof would also be supported by a timber frame.

In jobs such as this, our input to the design stage typically involves advising on the dimensions and positioning of the timber battens which make up the frame, providing guidance on the location and type of fixings to be used and identifying areas where additional, local reinforcement might be required.

Carrying out the structural analysis

A linear elastic structural analysis of this system was conducted using the finite element method. Unfactored loads were used and then compared with the factored allowable stresses for the various materials of construction.

Maximum stresses in the walls (left) and roof (right) under combined wind and snow loads.

Individual load cases were analysed, as well as a combination of wind and snow loads. Personnel loads were not combined with either wind or snow loads because it was assumed that maintenance would not be carried out when the roof was covered with snow or when significant wind was acting on the structure.

Maximum bolt forces were identified and used to calculate maximum stresses in the bolts.

The outcomes

The stresses and deflections predicted by the finite element analysis were within the maximum allowable values for the various materials of construction. Therefore our client was able to present their customer with an independent report, showing that their product was suitable for the specified conditions.


Computer-aided Design (CAD)

Our design engineers can help you visualise your products using computer-aided design (CAD), or can prepare your existing CAD models for structural analysis

Design Codes and their Application

Where there is a requirement to design a composite component in accordance with a specific standard or norm, we can work with you to ensure design compliance

Design Verification

We can provide an independent verification that the design of your composite product is fit-for-purpose, or advise you on modifications that might be necessary

Finite Element Analysis (FEA)

A computational tool for simulating and analysing the response of a structure to applied mechanical or thermal loads - used for design verification and optimisation



Their low weight, durability and mouldability are the key drivers for using composites in infrastructure applications. Lightweight composite bridges, tanks and pipes can be easily installed, whilst allowing designers to achieve freeform shapes.  Our consultants can help you assess the fitness for purpose of your composite structures.

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