This text book covers the principles and methods of load effect calculations that are necessary for engineers and designers to evaluate the strength and stability of structural systems. It contains the mathematical development from basic assumptions to final equations ready for practical use. It starts at a basic level and step by step it brings the reader up to a level where the necessary design safety considerations to static load effects can be performed, i.e. to a level where cross sectional forces and corresponding stresses can be calculated and compared to the strength of the system. It contains a comprehensive coverage of elastic buckling, providing the basis for the evaluation of structural stability. It includes general methods enabling designers to calculate structural displacements, such that the system may fulfil its intended functions. It is taken for granted that the reader possess good knowledge of calculus, differential equations and basic matrix operations. The finite element method for line-like systems has been covered, but not the finite element method for shells and plates. .