Research On Collapse Resistance Of Tall Formwork Support Based On ANSYS/LS-DYNA

In recent years,China’s demand in building,bridge and other infrastructure construction is increasing dramatically,and the use of formwork support,especially the tall formwork support,is inevitable in the construction of infrastructure.However,due to the lack of detailed research on the bearing capacity and anti-collapse performance of formwork support,collapse accidents of formwork support occurred frequently in recent years,resulting in heavy casualties.Therefore,based on the software ANSYS/LS-DYNA for the tall formwork support of four typical construction methods(including symmetrical,spiral two inclined rod layout and matrix,plum shape two unit frame plane combination),this paper mainly carried out the following work:(1)The finite element model was established,and LS-DYNA explicit dynamic analysis program was used to compare the bearing capacity and collapse process of tall formwork support under four typical construction methods.The results show: In the plum-shaped combination,the ultimate bearing capacity of the helical frame is improved compared with that of the symmetric inclined bar erection,but in the matrix pattern combination,the ultimate bearing capacity of the two inclined bar erection modes is close.In both the symmetric and the helical inclined bar erection modes,the ultimate bearing capacity of the plum-shaped frame is improved compared with the matrix frame.The difference of collapse process between symmetrical and helical inclined rod arrangement is whether the ultimate bearing capacity of vertical rods at different positions in the same unit frame has obvious regularity.The difference of collapse process between matrix-shaped and plum-shaped combination is instability sequence,instability pattern and bearing capacity of vertical pole at the same position.(2)The influence of structural parameters on the ultimate bearing capacity of tall formwork was obtained by modifying the initial bending rate of vertical rods,wall thickness of vertical steel pipe,longitudinal and transverse vertical bar spacing and horizontal bar step spacing.The results show: The ultimate bearing capacity of the vertical bar decreases with the increase of longitudinal and transverse vertical bar spacing,horizontal bar step distance and initial bending rate,and the influence of horizontal bar step distance and initial bending rate is more obvious.With the decrease of joint stiffness and wall thickness,the ultimate bearing capacity of the vertical rod decreases distinctly.(3)The finite element model was established,and the mechanical performance of the tall formwork braces after removing the vertical rods at different positions was analyzed by using the explicit dynamic analysis program LS-DYNA,and the anticontinuous collapse performance under the accidental action of the tall formwork braces under four typical construction methods was compared.The results show: Under normal construction load,the failure of vertical pole at any position will not cause the collapse of the tall formwork support due to accidental actions.Under the symmetrical inclined rod arrangement,the maximum axial force growth rate after failure of the first type of vertical rod is greater than that of the second type of vertical rod which is also located at angle,edge or inside.The maximum axial force growth rate after the failure of the vertical bars at angle is much higher than that of the vertical bars at the other positions under both the symmetrical and the helical inclined bars.Compared with matrix shape,the combination mode of plum blossom shape can effectively reduce the maximum axial force growth rate after the failure of the vertical bars at angle,but has little effect on the other positions.(4)Based on the above research contents,the finite element model of an engineering example is established,and the bearing capacity,collapse process and anticontinuous collapse performance under accidental action are studied by LS-DYNA explicit dynamic analysis program,and then corresponding suggestions are put forward to improve its anti-collapse performance.The results show: The bearing capacity and anti-continuous collapse performance of the frame can be improved effectively by using the helical and plum-shaped arrangement of inclined rods,and the stress state of the vertical rods at the corner should be monitored in real time and the vertical rods at the corner should be protected.