Glass Breakage in a Fire

Maybe try the Building Research Establishment?

Del

How did you obtain the value ?

hi,

i didnt calculate it, i found it in a research paper where they had done a lot of tests and compared other research. that is why i am not sure how correct it is. plus i cannot cite it for my work as it is not a scientific journal, but i dont fancy reading through 100's of articles!

Thermal glass breakage happens due to thermal strain. The time rate of change for the tempurature is as important as the total temperature obtained. In my house fire the windows crazed when the water from the fire hoses hit them. At least that is what the fireman told me.

It is then a school work yes?

If it so you should work yourself through the documentation since it is part of the learning process.

I can only give you some hints. When in the window pane a temperature gradient develops there is a thermal dilatation associated to it, this means that the heated surface being at a higher temperature will increase due to it and the cold surface will increase less so that the window pane will bend. When the strain will reach the limit for glass it will break.

Since glass has a low thermal diffusibility heat travels in it at low speed, if the temperature goes up fast the glass panel will break at a lower temperature than when the temperature will rise slowly because the gradient will be bigger.

As you see it is a complex question which can not be answered as simply as you expect.

You could try if you have a multi physics soft in your facility to compute the strains versus time and considering the temperature rise speed.

thanks for your reply.

i am doing this for uni but it is not a part of the work as such.

i am investigating a housefire scenario and want to know if the windows will break therefore allowing more air in and idecreasing the time in which it takes to reach flashover.

i have already established that flashover will occur.

Why would you suspect the time for flashover would decrease if the environment is purged?

The cause of the breakage will be do to the expanding atmosphere inside the sealed unit forcing out on the panes until one or the other breaks. The temperature at which this will happen will be determined by the glass thickness, what the atmosphere inside is composted, whether the glass is tempered, what the material is that forms the seal between the two pieces of glass, and the rate of temperature increase.

So you need a set of specs on the IGU (Insulated Glass Unit)

Thicker glass and tempered glass will hold greater pressure so the temperature would increase. Some IGU's are filled with gases like argon which would change the temp. A slow rate of temp. increase may melt the sealant sealing the IGU relieving internal pressure.

The AAMA only give standards for a test. Which applies to fire rated IGU. Which very few if any home windows have installed.

thanks everyone for your comments. i think this is another one of those things where there are just so many variables to consider that you could be here for a very long time! (as is the way with fire science). i think i will just write up about the diffrent variables that could affect whether the glass in the windows would break and the effect this may have on the fire, as best i can that is!