So,I started to work in crane production industry . I suppose to choise the correct IPE profile for my jib crane (which looks like this one http://www.eotcranes.org/wp-content/uploads/2015/05/Post-Mounted-Jib-Crane.jpg ) , but no one in engineering department wants to explain me how to choose correctly (they all extra busy :( ) . First of all , I see that they calculate deflections ,which I don't get why ? Why deflections are a factor ? But anyway,my main question is how I choose the correct profile in my crane ? Ok,I suppose to find the most "problematic" stresses . How do I find them in IPE profile ? And then , I compare them to standart Sy of steel (RS37 grade) ?