Structural Design for domestic projects has for decades been undertaken using simple tools for analysis and design, but are these still appropriate to meet the demands of the 21st century client?
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We are delighted to welcome Graham, Tracey, Riccardo and Debbie of T & F Design Partnership into our team, with effect from 1st June 2015.
Regular customers will know that T & F Design moved into offices with us at The White Horse in Pampisford at the beginning of February, so for some months we have been working together and developing the best features of both firms to take forward into the future.
The legal formalities are almost completed, which will see the incorporation of T & F Design Partnership into Structural Engineers Cambridge Limited, and we look forward to serving all of our clients with the expertise, vigour and helpfulness that has made our respective practices successful over many years.
This is an exciting time for all of us, and it has been a source of great satisfaction to see how well our team has worked to make the changeover happen smoothly. We’re looking forward to the future and we’re happy to explain what it means and how we plan to bring our constantly improving service and capabilities to your benefit.
T & F Designs’ phone numbers and email addresses will be maintained, so you will be able to contact us on (01799) 531313 as well as (01223) 833555 – we look forward to hearing from you (but Riccardo's special cheesecake will be long gone by then...)
The HSE has published a simple guide for small builders working in domestic construction projects - it can be found on http://www.hse.gov.uk/pubns/cis80.pdf
When working for a domestic client, the principal contractor will normally take on the client duties (to ensure the project has a plan for managing health and safety risks) as well as their own as principal contractor. If a domestic client does not appoint a principal contractor, the role of the principal contractor must be carried out by the contractor in control of the construction phase. Alternatively, the domestic client can ask the principal designer to take on the client duties (although this must be confirmed in a written agreement) and the principal contractor must work to them as ‘client’ under CDM 2015.
What is CDM and how does it affect me? Read this!
CDM stands for Construction Design and Managements Regulations and affects everyone involved with commissioning, designing or executing a construction project - even domestic clients.
The regulations have just changed and now even domestic clients are not exempt from the requirement to appoint a Principal Designer and a Principal Contractor. Commercial clients are responsible for ensuring that proper arrangements for managing the project safely are put in place and reviewed throughout the life of the project.
The Principal Designer is a new role that brings with it the specific responsibility to ensure that the Designers working on the project discharge their duties to eliminate, minimise or manage health and safety risks throughout their appointment.
The Principal Designer will support the Client in making sure pre-construction information is provided to those who will need it during the project, they will work with the Principal Contractor to ensure that the health and safety implications of design aspects and later changes are properly considered. They will support the Principal Contractor in drawing up the construction phase plan and in developing the health and safety file to provide to the client at the end of the project.
From all this it can be seen that the duties are very real and apply to everyone involved in construction - even those who previously thought the regulations did not apply to them (although in fact they probably did!). Structural Engineers Cambridge will be providing further help and guidance in this area throughout the year, and if you have any queries regarding this please contact us - we're happy to help.
The term "factor of safety" is widely misunderstood and often misused - so that is why structural engineers do not use it!
What we have instead is a system to ensure that the structure we design will withstand all the applied forces throughout the life of the structure, while remaining serviceable and safe. It is also necessary for the structure to be economical and environmentally sound, because to provide more structural capacity than necessary is wasteful and can in some cases be unsafe.
This system is called Limit State Design, where a factor is applied to the design actions (or loads) on the structure according to their type, and then combined for comparison against the design resistance (strength or stability) of the structure.
These factors are smaller than you may think - for Eurocode design, the factor on permanent actions (generally the weight of the building itself; in British Standard design it is called Dead Load) is 1.35 and for variable actions (Live Load or Imposed Load) it is 1.5.
A combination of these actions used for design would then result in the actual forces being increased by about 40-45%, which does not leave much room for guesswork or error! Other partial factors will apply for other types of action, for example wind pressure or accidental forces, or if resisting an overturning failure. These factors can be combined in several ways and it is notionally possible to achieve an overall factor of just over 20% on the characteristic (i.e. unfactored) actions, which the competent designer would not wish to do!
Within the standards for construction materials, there are also factors related to the probability of the material being able to meet the design values, so for a consistent material like steel the material factor is quite small (1.05) but for less consistent materials such as timber, concrete or soils the factors would be correspondingly greater in order to ensure that the actual material will reliably meet the design requirement.
While nostalgia for the seemingly simpler world of British Standard design remains strong, the use of Eurocodes for design is now established and gaining ground in the UK. However, care in their use is vital and even simple beam design has passed beyond the reach of the amateur.
For professional structural design, contact Structural Engineers Cambridge.