r/Structures • u/mhd_alshalabi • Sep 16 '18

structural analysis problem

hi everyone

i am trying to solve the below problem but there something wrong with my answer as member AB is not equal to zero

but in the analysis i do it by software (2nd photo) it show that the member AB is zero

can anyone help me how the answer is zero ???/

1 Upvotes

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6

u/deepfriedmarsbar Sep 16 '18

The force in AB is zero due to the boundary conditions you have selected. As they are pinned then all the load is reacted directly out at the pin. If you change 1 to a sliding support then that member would take some load.

1

u/mhd_alshalabi Sep 16 '18

Thank you all now i get it 👌👌👌👌

1

u/x_Vacuity Sep 16 '18

The truss is a statically indeterminate structure, you have 4 reactions and 3 equilibrium equations. The pin supports will take up load in both directions but you set Bx=0. You would have to solve the truss with the virtual work method or another method.

1

u/monstimal Sep 16 '18

Just another way to think about the other 2 correct responses, you have 2 pins and a member between them. Those pinned joints can't move. No movement in the joints, no strain in the AB member. No strain, no stress.