August 2008 Issue 3

Belt and Braces

Don’t know if it is the lack of trained engineers, sloppy management or consultancies that are risk averse, but the “belt and brace” designers seem to be coming out of the woodwork again.

Over 70% of our workload is in the design and build sector where we have built a reputation for delivering tender winning designs, on time every time.  This ensures that our clients win more tenders and maximize their profits.

However, we are sometimes approached by our D&B clients to give them advice on projects that they are tendering under a traditional contract.

They recognize that economies can be made on some of the structure, but need our input to cut their costs.  In these cases, we find savings that are large enough for our D&B client to win the tender and  pass on to their client, with a win win for all.

Is This a Rising Trend?

However, over the last few months our clients have been asking us to comment on engineering schemes that they even think are grossly overdesigned and they are right.  Our analyses of this growing trend can be summed up as below:

1.  The recommendations given in the site investigations are too loose and open to interpretation, ranging from acceptable to risk averse. Engineers then design to the risk adverse solution.

2. There seems to be a lack of understanding of how floor slabs interact with the ground. Often when the ground is perceived to be poor, we have seen examples of engineers detailing a thick floor slab and two layers of heavy mesh reinforcement, where in fact a 150mm floor slab with one layer of light mesh is sufficient.

3.  A poor understanding of how the superstructure relates to the rest of the building and how the loads are transferred through the building.

Example

An example of such design was passed to us last month to see where we could make savings. This was for a two storey, 18m wide office block, sat on ground more than adequate for simple pad foundations.

However, the tender design was piled foundation (5 piles on the inner columns) a 350mm suspended floor slab, with double reinforcement and an unbelievable heavy steel frame. Our contractor client cost this design out at £5m.

Our Solution

After a couple of hours, we re-jigged the design which panned out into a £300,000 saving.

For more information please contact us on:
01535 633350 or email: winmytender@pwaite.co.uk