I'm hoping I can find a place to ask these types of questions as a student or layperson. Please no rude flames or responses. I am asking for help because the material is currently a bit out of reach for me. Can I get some help to understand. Thank you. From Analysis of Arches by Trupti Sonavane there are figures attached. A point load is said to be established for example in this case it may be said 10Kn for an arch of 12 ft in diameter. There is a defined equation SigMA = BY * 2 * x1 - P(x1+x2) to determine a moment about support A of the arch as defined in the detail. As BY is the vertical reaction and P is defined to be 10Kn is the vertical reaction also 10Kn and if not how is BY to be determined? In addition I understand that there is an output of the function called SigMA (moment about A) however it is unclear to me what that number really actually means physically to the structure for instance is SigMA a vertical moment and if the moment (SigMA) is exceeded what does that mean for the structure?