Foldable structures are very important for the purpose of rapid construction and bridging system. Such structural element can be utilized in disaster relief operations. In the early days, portable structure such as military bridges were made from steel, causing the weight of the structure to be huge, subsequently it will be costly to operate. To overcome these problems, aluminium and metal alloy were introduced to reduce the weight of such structure. Use of composite material such as Carbon Fiber Reinforced Polymer (CFRP) emerges as a lighter alternative being considered to be the primary material for the portable structure. The use of the CFRP as a primary material is due to its high strength to weight ratio, thus make it lighter than steel and other alloy. In this research, a long-span portable structure is analysed and designed using finite element method. Several dynamic simulations are made to test various possible lay-up including use of core in order to increase strength and stiffness of the member. From the trials it can be concluded that with proper design and fabrication, CFRP is capable of carrying the designed dynamic load. Furthermore, use of core layers for top flange can improve the performance of the structure significantly, while use of core to the webs stiffen the webs against buckling and further improve the overall performance of the structure.