when we make a case , say e.g.-
operating ( T3, D3)+ dynamic hogging (D1)+ static hogging (D4) + Normal ship accleration/ deflection in X direction (U1,D6)+Normal ship accleration/ deflection in Z direction (U3,D8)which is -
W+D1+D3+D4+D6+D8+T3+P1+H+U1+U3 -
My question is- U1 is acceleration in +ve X and U3 is acceleration in +ve Z. Corresponding structural deflections for tall structures supported from main deck are D6 and D8. Normal practice is D6 and D8 used in these cases are also positive as received from structural design group corresponding to +ve value of U1 and U3 respectively.But as per dynamic behavior when D6 is positive the corresponding inertial acceleration on pipe has to be in opposite direction and hence both U1 and D6 can not have same sign in this case. The signs should be opposite . Same logic for U3 and D8. PLEASE ADVICE .