Utilization check of a Double Tapered Beam

• specific checks for apex zone
• section of maximum utilization checked as for single tapered beams
• support check

Links:

• https://github.com/Anthrazit68/NODEMaple
• https://www.moelven.com/globalassets/moelven-limtre/limtre_eksmpl_digital.pdf
• https://www.moelven.com/globalassets/moelven-limtre/limtreboka_2015_el2.pdf