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The car body shell is a self- supporting rigid structure, made and composed of large ___________ extrusion sections connected by ___________. The shell is designed as a ___________: all profiles are welded together in a ___________ direction. This type of design principle is known as “___________”, providing high rigidity of the car body whilst using a ___________amount of material. This feature is beneficial to fulfilling the important goal of transporting a large number of passengers. The car body strength can meet the following: ___________ load, static load, impact load applied under operating conditions. Additionally, it is also for all working conditions of ___________, lifting, rescuing, ___________, coupling and ___________multiple unit trains to the depot.