1- From a structural point of view, is it possible to slightly increase the weight of the glass infill in a metal curtain wall panel if the resulted load would still be well below the designed load capacity for the panel frames and anchors (given the factors of safety)?
An example of this would be replacing single panes with double panes, or double panes with triple panes of glass - i.e., adding an additional glass lite of similar thickness. So if the new glass infill would make the weight of the curtain wall panel equal to say 1.2 of its original actual weight, would that be acceptable in concept if the original structural design incorporated a factor of safety for dead load of say 1.65 for the frames and 2.34 for the anchors (assume the same for wind load)?
2- Are there precedents of facade retrofits (reclad or reglazing) where glass infills were replaced with heavier ones while the existing frames and anchors were maintained?
3- What are the standard field tests to determine the load capacity of a curtain wall panel and anchors in an existing building?
Thanks
1. I feel it is possible ut may depend on various factors. For instance, the design pattern, the hight of the cladding, the nature and material specification of tensioning systems. I suggest as well that due attention should be given to the ability for the cladding system to bear the load so increased considering the allowable factor of safety for such designs and system.
2. I am not aware of any precedents where infills of curtain walling were increased in weight / load. I guess it is not common. My experience with a hospital in Doha Qatar where periodic maintenance was carried out on curtain wallling shows tremendous need for re-strengthening the tensioning system to bear similar loads of original designed pattern and material specified. Another experience I had was a games village hostels converted to an hospital in same Doha where there were requirements to change the pattern design of the curtain walling and the outcome again was that, it could not accommodate the new intended design because of the weakened tensioning over time. I think age of the structure also counts.
3. Standard test relating to this that are usually carried out was tensioning test and load test.
The size of the glazing pocket minus the thickness of the available gaskets - assuming it is a gasketed system - will determine whether or not you can install thicker (heavier) glazing, even if the frames and attachments will take the additional weight, as will the supporting elements on the building. Some manufacturers make varying sized gaskets to accommodate different thicknesses of glass.
If the frame system is not gasketed, and is silicone adhered one side, there is no problem other than checking the capacity of the anchorages.
Some systems are combination gasket and silicone adhered with adjustable pressure plate retention of the glazing. These should be no problem either.
The ASTM E1105 test is a field test for both structural capacity and water intrusion. I have had this test performed many times with success.
Ladd P. Ehlinger, AIA
recently, I've just read an article regarding the integration of prefabricated facade modules. I thought it might be helpful for your question.
sincerely,
Negin
Conference Paper A zero-energy refurbishment solution for residential apartme...
Thanks, Femi, Ladd, and Negin for your answers.
PS: Please assume that the design of the curtain wall system can take thicker glass infills.
(Given that the concern is purely structural and to further clarify the question for future answers, I just wanted to eliminate the variables that are related to the design of the system).
Thanks
Considering structural modeling inaccuracy, I do not see any problem.
Yes you can but take into consideration notes suggested by Femi Alofe.
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