Steel Truss Preliminary Design
Steel Truss Preliminary Design
(OP)
Hello Everyone,
I have a question about truss systems. I have been designing steel truss systems since last year. I am not the one making decisions of type of truss, height of truss or other parameters. My supervisors tell me these parameters and I am making the rest of the job. But I am not happy to fullfil what I am told. Because I want to learn how people making decisions according to the projects.
I am quite sure that my supervisor making decisions according to the their former job experience. I, of course, understand and respect their experience. But any advice will be very helpful.
I have attached a photo to show what I am thinking.
I have a question about truss systems. I have been designing steel truss systems since last year. I am not the one making decisions of type of truss, height of truss or other parameters. My supervisors tell me these parameters and I am making the rest of the job. But I am not happy to fullfil what I am told. Because I want to learn how people making decisions according to the projects.
I am quite sure that my supervisor making decisions according to the their former job experience. I, of course, understand and respect their experience. But any advice will be very helpful.
I have attached a photo to show what I am thinking.





RE: Steel Truss Preliminary Design
RE: Steel Truss Preliminary Design
The height of the truss at the center is dictated by the desired slope of the roof and the span of the truss. It can vary from almost flat to a pitch of 6/12 or some other pitch of the roof. This can be influenced by wind loading and snow loading. In areas of high snowfall, the pitch of the roof could be high to prevent snow drifts. If you lower the pitch of the roof in such areas, the truss has to be stronger because of the higher loads. For wind loads, the pitch is desired to be lower so that the lateral wind load is lower.
These are generalizations of these decisions.....there are many variables that can go into the decisions that you are questioning. The client often dictates many of these variables and some are dictated by engineering constraints.
RE: Steel Truss Preliminary Design
The real thing that making me uncomfortable is limits of this system. For instance, after 10m spans we have to think a truss system rather than a Beam-Column frame system. Because of a frame system becomes uneconomical and sections of beams become unnecessarily bold. These differences are key for a design
Thank you so much.
RE: Steel Truss Preliminary Design
After the building takes a basic shape, i.e. floor area, height, roof line, then the sizes of the structure can start to be determined preliminarily (using rough calculations or rules of thumb). This preliminary sizing allows the client to get a feel for the proposed cost and final structure shape, and more often than not a client realizes what they want may exceed what they can afford so this is the stage to make modifications to size, height, acceptability of interior columns etc.