design-in-steel

Obtaining the correct size for a steel beam lintel is tricky. That’s why it’s always left to a Structural Engineer. But if you’re comfortable working out the approximate load acting on your beam, then there are simple methods you can use in order to estimate the size you need. Read the rest of this entry »

TEDDS have released a product bulletin to make customers aware of an “un-conservative” feature in their column baseplate design module. All engineers in the UK who have used this feature may need to re-check their baseplate designs using another method, or using the updated version of TEDDS. Whilst not wishing to give TEDDS bad press, we felt it prudent to make this information available to our readers, given the wide usage of TEDDS in the UK. The distributors of TEDDS (CSC) have taken the responsible step in notifying customers of this flaw, and we congratulate them for doing so. See this link for product info.

The British Constructional Steelwork Association have released the following forecast regarding steel prices in 2009:

“Steel prices, along with prices for concrete and rebar, have seen dramatic increases over recent years driven by global demand, particularly from China and India. The demand has been both for steel and the raw materials for steelmaking eg iron ore and coal. However in recent months there have been reductions in global demand which has resulted in a steel prices plateauing.

Looking forward through 2009, it is likely that there could be steel price reductions in the first half of 2009. However the fundamentals of world steel supply in the medium and long term are unchanged and it is anticipated that global demand and prices will eventually rebound, the key question is exactly when and this, of course, is a little difficult to forecast.

The expectations for the price of iron ore and coal would suggest modest price reductions in 2009 (though these may a while to feed into the supply chain). Whilst energy costs in the UK remain stubbornly high, shipping and other ancillary costs will react to the market volumes, falling in the short term and potentially rising with the anticipated recovery in demand..

In summary BCSA is confident that steel prices are highly unlikely to increase in the first quarter of 2009 and modest price falls are anticipated. There may be a recovery in the second quarter but again this will be modest and offset by cheaper raw material supply. The likelihood of volatility in prices seen in 2008 is very remote.”

So what if Wembley Stadium has cracks in it. Buildings crack don’t they? How big is it? Over 1 inch wide? 40 feet long? Oh dear.

So what should we make of today’s announcement? The officials say that there’s nothing to worry about; but those who witnessed the crack opening up were scared half to death. Here’s the official statement:

“As with all large structures, the stadium has been designed with movement tolerance factored in. Reports suggesting that there is a crack in the stadium as a result of this movement are incorrect.”

In the UK, structural steel must be designed by qualified structural engineers to British Standards or Eurocodes. These codes are designed along the lines of limit state philosophy. What this means to you and me is that the structure of a building must not fail to carry out its intended function. This applies to structural strength, but also many other serviceability factors. One of these factors is deflection, or movement. A building structure may move, but not so much that people feel unsafe or uncomfortable, nor should it move so greatly that finishes (e.g. plaster) are damaged. It seems both of these “limit states” have been exceeded, and therefore the building could be unfit for use.

But the situation could be much worse than that. The structural engineers who designed this stadium would (or should) have taken movement into account. If a crack of 1.5 inches has opened up in the plaster, either the designer made a mistake, or the builder did. It could point to a small error such as the builder forgetting to put in a movement joint. It could also point to incorrect assumptions made by the structural designer, completely invalidating his design. Should this worry you? Well, that depends on whether you’re going anywhere near Wembley Stadium!

The SCI/Corus blue book is an invaluable source of geometric and structural data for British steel sections. It is now available online at the following location:

http://csbluebook.steel-sci.org

The first in our Glossary of Terms series. We aim to build this up into an exhaustive visual database of steel terms. First up is the portal frame ridge, or apex:

Purlin: A secondary structural member that transfers the load from roofing material to the primary structure.

Rafter: A primary steel roof member upon which the rest of the roof structure is supported, usually made up of Universal Beam sections.

Rafter Stay: A steel strut which connects the bottom flange of the rafter to the purlins, providing some restraint to lateral torsional buckling in the rafter.

Ridge Purlin: Name given to the purlins located nearest the roof ridge.

Purlin Cleet: Bracket welded to the rafter to which purlins are fixed. It is designed to limit rotation of the purlin.

Apex Haunch: Deepening of the rafter at the apex where bending moment is greater than what can be resisted by the rafter itself.

End Plate: A plate welded to the end of a steel member so that it may be connected to another member, usually by bolting.

Click on the image to see full size.

The main steel detailing software packages used in the UK are listed below along with website links.

StruCad

by AceCad software: www.acecad.co.uk

One of the most popular products in the UK with structural and architectural steelworkers alike.

X-Steel

by Tekla: www.tekla.com/uk

Probably the most polished steel detailing software available, but also the highest priced.

Advance Steel

by CADS: www.cadsglobal.com/advance_steel_home

A relative newcomer offered by CADS who are best known for their excellent RC detailing software.

ProSteel 3D

by Struc Soft (recently bought by Bentleys): www.strucsoftsolutions.com/prosteel3d

Little used in this country, but well worth looking at. They have recently brought out a lite version which may be a great benefit to structural engineers and small fabricators who don’t need to detail entire buildings.

New Steel Construction is a monthly magazine produced jointly by the SCI, BCSA and Corus. It contains articles related to steel construction, software reviews, news, and case studies. At times the magazine is offered free of charge and can be obtained by emailing admin at new-steel-construction.com

The website offers a fully searchable archive of back issues at www.steelconstruction.org

Steel prices continue to rise rapidly by some 22% globally this year. But what’s causing this?

“Demand for steel has risen exponentially as such emerging countries as China and India create the infrastructure that ultimately will house, transport and service the largest and wealthiest populations on the planet.”

See the full article here