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I was thinking of the case where stresses are caused by shrinkage. In one form or another the problem of reinforcing for shrinkage cracking at re-entrent corners occurs in almost every concrete slab or wall. Chris Rohde Editor, Structural D-zine http://www.topica.com/lists/Structuraldzine

I have found some useful spreadsheets at http://yakpol.net/ Chris Rohde Editor, Structural D-zine http://www.topica.com/lists/Structuraldzine

The Australian code, and I guess most others, requires additional reinforcement at re-entrant corners, openings, etc to control cracks starting from the corners. We usually use trimmer bars at 45 degrees across the corner. Does anyone have a rational method to determine the quantity and...

In a grid structure part of the load will often be carried by torsional moments. If you don't want to design beams for torsional loads you can reduce the torsional stiffness of members by a factor of say 100. This should make torsional moments negligible for design. However you should then...

If I understand your description properly this sounds similar to what is being used in Australia. When tested these types of connections generally perform poorly. I suggest you have a look at these references; http://www.topica.com/lists/Structuraldzine/read "A new knee joint" JE...

I think the concrete will crack at right angles to the principal tensile stress, which is also parallel to the principal compression stress. Generally in a beam the angle will be between 30 degrees at low shear and 45 degrees at shear close to capacity. Chris Rohde Editor, Structural D-zine...

Even if you do decide to anchor the slab you should not do it by driving reinf bar into the ground. Eventually it will rust out and provide a corrosion path into the slab. Chris Rohde Editor, Structural D-zine http://www.topica.com/lists/Structuraldzine

There is a recent newsletter article on welded girders on http://www.topica.com/lists/Structuraldzine/read This might answer some of your questions.

JAE, A good reply. Regards

Xypex is an additive that appears to be quite effective. It causes the growth of insoluble crystals in cracks blocking water flow. It can be applied to the surface or added to the mix. Chris Rohde Editor, Structural D-zine http://www.topica.com/lists/Structuraldzine

A band off heavy reinforcement will increase stiffness, especially after cracking. In addition the band will have a much higher moment capacity, where you need it. Analysing the full moment field in an anisotropic panel, the properties of which are load dependent, is just too hard. Neither...

You don't generally need to combine roof live load with wind load. Roof live load is basically a construction or maintenance load. It is assumed that no-one will be on the roof during the design wind speed event.

Wim, won't you achieve those benefits by using steel fibers alone?

I have found that wind loads and seismic loads can often dominate the design for pipe racks but then my designs are often in cyclone (hurricane) regions and/or seismic regions. The sheeting on the windward side should shield the pipes and leeward sheeting and will probably be in your wind...

In the Australian code the values given for E, the elastic modulus, include an allowance for shear deformation. If you only want it to calculate deflections that should be enough. What do you want to know for?

Can you provide some additional info/detail on the cracking through phenomenon?  The first time I encountered this was soon after graduation when I was asked to do a report on a cracked slab. Briefly this was a long narrow slab supported on walls and exposed to the weather. The slab had...

Sorry, don't know where I got the steel beams from. The discussion still applies. i.e. what happens depends on the connection between the two sets of beams and their relative stiffness. As JAE says a lot of designs using simplistic assumptions are still performing well. If you use simple design...

One problem with one way slabs is that shrinkage can cause large cracks right through the slab. This is not so much of a problem in the load carying direction because flexural cracking forms a close crack spacing and hence tapered cracks of narrow width. Sometimes in long one way slabs you can...

Carl, I guess it means that the plastic fibres are performing no structural purpose in the hardened concrete.

Capper, in your case with monolithic construction I agree with designing for torsion, but if the connections between the steel and concrete beams are not rigid I doubt significant torsional moments would develop. That's why I suggested reducing the torsional rigidity AND provide minimum...