1217 words - 5 pages

Effect of parameters on bending moment and shear force

The study compares the effect of parameters on bending moment and shear force produced by fatigue load models. The fatigue load models are again classified based on number of axles for the calculation of bending moment and shear force. The bending moment and shear force is calculated for simply supported span. Bridge span is adopted as variable. The maximum bending moment and shear force is calculated to study the effect on bending moment and shear force with increase in span.

Effect of number of axles on bending moment and shear force

Bending moment and shear force decreases as number of axles increases, because with increase in number of axles the distribution of load increases. For instance, for almost same gross vehicle weight and 50 m span: in Figure 14, Euro code two axle FLM 4 (GVW = 200 kN) and in Figure 16, three axle Schilling’s model (GVW = 222 kN) produces bending moment 2344 kN.m and 2283 kN.m respectively; in Figure 16, Euro code three axle FLM 4 (GVW = 310 kN) and in Figure 18, four axle BS 5400 model (GVW = 320 kN) produces bending moment 4239 kN.m and 3374 kN.m respectively; in Figure 18, four axle Laman’s model (GVW = 490 kN) and in Figure 20, Euro code five axle FLM 4 (GVW = 490 kN) produces bending moment 5280 kN.m and 5265 kN.m respectively. In all the three examples, the models of same gross vehicle weights are compared to see the effect of increase in number of axle and the reduction in bending moment is seen in all the three cases.

Effect of gross vehicle weight on bending moment and shear force

Bending moment and shear force increases with increase in gross vehicle weight. For instance, for 50 m span: in Figure 14, Bing and Wu’s fatigue load model having GVW equals to 115 kN produces bending moment 1363 kN.m; in Figure 14, European two axle FLM 4 having GVW equals to 200 kN produces bending moment 2344 kN.m; in Figure 16, AASHTO’s FLM having GVW equals to 325 kN produces bending moment 3334 kN.m; in Figure 20, European five axle FLM 2 having GVW equals to 630 kN produces bending moment 6794 kN.m. In all the four examples, increase in gross vehicle weight increases bending moment.

Effect of axle load ratio on bending moment and shear force

Bending moment and shear force is lesser for equally distributed axle loads rather than unequally distributed axle loads. For example, for 50 m span: in Figure 16, Schilling’s fatigue load model (GVW = 222 kN) having equal axle load ratio and in Figure 16, Bing and Wu’s fatigue load model (GVW = 230 kN) having unequal axle load ratio produces bending moment 2283 kN.m and 2517 kN.m respectively; in Figure 18, Euro code’s FLM 3 (GVW = 480 kN) having equal axle load ratio and in Figure 18, Laman’s fatigue load model (GVW = 490 kN) having unequal axle load ratio produces bending moment 5137 kN.m and 5280 kN.m respectively. In the above example it is proved that the bending moment is less when all the axle loads were equal while it was...

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