Question

Q3. Explain what is meant by “maximum absolute moment and shear in beams”. Your explanation must be based on cantilever beams and simply-supported beams subjected to single and multiple concentrated loads. (15 marks) Given a 3-axle truck with the following loads as shown in Figure Q3, determine the position of the truck that produces the maximum moment on a 24 m simply supported bridge when the train moves on the bridge. You may ignore the weight of the bridge and assume that the wheel loads shown are the total wheel loads. (10 marks) [Total: 25 marks] Wheel Loads: 10 kg 7500 kg 4.5 m 7500 kg 6.0 m Figure Q3

Answer 1

greatest which is the greater Manimum absolute momentó bending Maximum absolute berting moment is Valce of bending moment is the span. which can exist only one point in the span Valise than with other any point in the span. at Absolute manimum bending moment can exist at the fixed support of the Contilever beam. When train locede compared of moving from one end to other the absoluta marimum bending moment exist at fixed end CSscanned with CamScanner

b) b) Absolute maximum. bending moment can exist at mid-point of simple train loads (or), a concentrated boad movir moving on the beam, supported becam. When a ๆ i Cantiliver beam i) Simpla Surp>6. Багы, اه L 2. 7 -- a b L il Manimem absolute sheay forces Manimum absolute shear force greater reater Value shiecar force is the af can eniso at only one point in a beam when a Concentric (or) train of loads moving on the b ecem. CS Scanned with Cardscanner

a) Cantiliver beam: in case of cantiliver beim absolute maximum bending momene a) Canti liver beam: for the case of contiliver becam absolute menima shear force can existe at the support of fixed end when a loads are moving on it. n 1 स b). Simple Supported beamo in case of simple supported beam absoluta marimum Shear force can enish at either supports of the becam. Cori) CS Scanned with CamScanner

7500 lokg 75ooky ooky om B A c 27m Marimum moment would exist ats med point of the beam. for manimum moment can occur truck boads when the boats will reach the position due to moving following CSScanned with CamScanner

loka 7500kg 7500kg A B KE me 6m 1 12m 12m + + Gm ab 12712-6 om 7.sni fisme Asooky long 3.75 I 27 7500kg 3 7.sm 7.5m Gи, Gm Iob. for moment of c) EM) = 6* 450) + ( 3x 1508)+(995) man 67537.5 kg-m 662316.62 N-my CS Scanned with Camistanner

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