Structural Optimization Crashworthiness And Strength Analysis Of Midi Bus Structure In Static And Rollover Condition

Midi-buses are a valuable vehicle to transport services and goods in Ethiopia's rural and urban areas.rnHowever, midi-bus are indirectly regulated through inspecting the end product (finished bus) duringrnlicensing for the public transport business in Ethiopia. Because of the lack of engineering analysis andrntesting procedures, the reliability and crashworthiness of a midi-bus are compromised and ultimatelyrncosting human lives and the overweight of the bus. Moreover, the weld formation and their types havernbeen done without scientific reasons. Consequently, this method leads to a catastrophic structuralrnfailure during accidents.rnThis research aimed to analyze the original midi-bus structure based on the static strength and rolloverrnanalysis using United Nations Regulation 66 via numerical investigation (ANSYS & LS-DYNA).rnMoreover, four design optimizations of the midi-bus structure were conducted: reinforcement designrn(����������������; numerical optimization (Response Surface Optimization (RSO) in ANSYS DesignXplorerrnfor static case (model – IIstat); Successive Response Surface Method (SRSM) in LS-OPT for rolloverrncase (model – IIroll)); and combined design approach (model - III) by merging of the static and rolloverrnoptimized models. Furthermore, the effect of full and spot arc welding on the quasi-static analysis ofrnfloor-wall and roof-wall connections was evaluated.rnThe result shows that the maximum deformation in static and tare-weight rollover cases occurs at thernbaseline structure's roof section and pillar A and bays from one to three, respectively. The bendingrnstiffness of the reinforced design (model – I), model – IIstat, and model – III (combined) was increasedrnby 41.65 % (1911.4 N/m), 55.8 % (2,563.1 N/m), and 58.1 % (2,667 N/m), as compared to the baselinernstructure. Moreover, compared to the baseline model, the structure's weights of the reinforced modelrn(model – I), model – IIstat, and model – III (combined) were effectively reduced by 5.23 %, 7.73 %,rnand 2.33 %, respectively. In addition, model – IIroll exhibited the weight of the reinforced model by 5.6rn% in the rollover case. During structural connection, full and spot arc welding are formed at the edgesrnand corners of the frames. Accordingly, these types of welds highly affect the energy absorbingrncapacity of the floor-wall and roof-wall connections. Generally, this research gives vital informationrnon the midi-bus structure weight, stiffness, and crashworthiness capability from slight to severe loadingrncases for both static and rollover conditions. Moreover, this research suggests the new optimized busrnstructure and better weld type while welding the structural connections.

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