The invention relates to a wind turbine blade (5) comprising at least two wind turbine blade sections (12, 13) that include one or more strengthening structures (6, 6a, 6b), the ends (14, 15) of said strengthening structures being connected in a connection joint. The ends include corresponding connection surfaces, the one or more relevant dimensions of said surfaces being larger than the dimensions of the transverse surfaces of the strengthening structures at said ends. The one or more relevant dimensions of said connection joint are larger than that of the adjacent strengthening structure. The invention also relates to a wind turbine blade in which the at least two wind turbine blade sections include a number of substantially oblong carbon fiber strips and strips of one or further materials such as wood or glass fiber. The invention further relates to a wind turbine blade section, an assembly plant for assembling wind turbine blade sections (12, 13) and to a method and use of such wind turbine blades.