Metal actually expands and contracts with weather change, and leaving some small gap in between tray sections is a must. When the distance between the metals is too low, the metals will push against each other and bend. When it is excessive, the tray will be weak and. In this guide, the expansion gaps are explained to be calculated, as well as how to select materials such as aluminum or steel. ” In 1993 NEC Article 318 there are no requirements for the handling of the thermal contraction and expansion of cable tray. Cable tray system designs that do NOT take this. Cable trays are a crucial component of electrical infrastructure, supporting the routing and management of cables within buildings and industrial settings. To mitigate these risks. e tray system. This paper examines the causes, implications, and mitigation of thermal dynamic stress in metallic cable tray systems, focusing on thermal expansion and contraction, the resulting internal stresses, and potential damage to both the t ay and cables.