Load distribution method at the node based on the force method and optimum design of cantilever length for lattice beam
The disadvantages of the simplified load distribution method for lattice beam are its inability to consider the effects of loads acting on other nodes of the beam in both directions,and subjective assumptions about the type of beams on Winkler foundation.To overcome the above disadvantages of the simplified load distribution method for lattice beam,a load distribution method is proposed based on the force method.According to the static equilibrium conditions and the deformation compatibility conditions at the nodes,the new load distribution method can distribute the loads acting on the nodes to the vertical beams and the cross beams running in both directions respectively,by constructing and solving a system of linear equations.In addition,this paper introduced a case of a slope reinforced by lattice beams,and the cantilever lengths of the vertical beams and cross beams were proportionally increased.Under the conditions of different subgrade reaction coefficients,the loads acting on the nodes of the lattice beams were assigned to the vertical beams and the cross beams based on the new load distribution method,and the bending moments of each beam were calculated separately.Using the absolute value of the ratio between the maximum positive bending moment of the cantilever and the maximum negative bending moment at the mid-span close to 1 as the evaluation index,the optimum cantilever lengths of the lattice beam were evaluated.The load distribution results show that the loads assigned to the vertical beams and the cross beams gradually become more constant as the cantilever lengths increase.The bending moment results show that the influence of the cantilever lengths on the bending moments gradually decreases as the subgrade reaction coefficient increases.Under the conditions of different subgrade reaction coefficients,the maximum positive bending moment of the cantilever and the maximum negative bending moment at the mid-span of each beam tend to be equal when the cantilever span ratio is between 0.2 and 0.4.Therefore,the introduction of this new load distribution method based on the force method provides a reliable theoretical basis for accurate internal force analysis and optimum design of cantilever length of the lattice beam.
lattice beamload distribution methodforce methodcantilever lengthoptimum designWinkler foundation modelslope engineering