A modular beam structure consisting of one or more collapsible, lockable and interconnectable support structure modules, and any transition module to change longitudinal direction of the structure. In addition, it is possible to attach onto one or more support structure modules a collapsible platform and/or wall or fence. The structure is at an upstream end or start end attachable, via a module end element, onto an attachment device, e.g. a wall or attachment block, via a support frame which is fixedly attached to the attachment device.