Performance evaluation of portable bridges using numerical simulations and laboratory tests

Portable bridges are important for ground mobility to transport troops and vehicles through gaps like rivers, valleys, and lakes, or when an existing bridge gets damaged because of natural disaster or being attacked by enemy. Imported and expensive portable bridges have been deployed in such situation. The objectives of this research are to design and evaluate the performance of locally produced CFRP, AA 6061 T6 and Hybrid beams and their steel connectors. The available materials in this country were selected in order to produce affordable beams and also to reduce dependency on imported portable bridges. Aluminium design manual (ADM) and trilateral design and test code for military bridging and gap-crossing equipment (TDTC) were used in designing and testing of beams. Detailed design of the beam was carried out by numerically simulating the beams using MSC Patran/Nastran finite element software. The simulations were constrained by allowable strength of material and vertical displacement limit of L/180. Wet hand layup method was selected in fabrication of CFRP and Hybrid beams prototype, while AA 6061-T6 beam prototype was fabricated using welding method. Strains and displacements were recorded during structural testing of the beam. Maximum load that can be supported by CFRP beam is 11.3 kN which is lower than design load of 12.7 kN due to preliminary failure of CFRP layers at compression joints. AA 6061-T6 and Hybrid beam have shown good performance that they are able to support load up to the ultimate load (U). Addition of CFRP layers at the bottom flange of beam has reduced tensile strains and vertical displacements of beam by 38 % and 9 %, respectively against AA 6061-T6 beam. Production cost of AA 6061-T6 and Hybrid beam is only at 33.3% of imported LEGUAN bridge. It can be concluded that the joints of CFRP beam need to be redesigned in order to improve performance of the beam. The redesigned joints were used successfully in AA 6061-T6 and Hybrid beam that show good performance as designed. The beams can be produced locally using available materials and technology in Malaysia at a much lower cost than the imported product.