Research On Mechanism Of Steel-concrete Composite Ribbed Net Based On Material Damage

As a new type of composite space structure,Steel-Concrete Composite Ribbed Shell has the characteristics of large span,large stiffness,high bearing capacity,convenient construction and low cost,and has good engineering application prospects.In this paper,the Composite Ribbed net is taken as the research object,and the bearing capacity,non-linear response and failure mode of the structure are studied by the method of static test of scale model and numerical simulation analysis of finite element.The structural performance changes under different influencing factors are studied by parameter analysis.From the point of view of material damage,the structure is divided into three parts.The damage distribution and state of the structure are analyzed,and the relationship between local damage and deterioration of structural performance is explored.Based on the damage state,the different stages of the structural stress process are divided,and the damage model of the structure is established(1)The performance test of Composite Ribbed net structure under static load is carried out,and the static indexes such as structural stress distribution,crack development and structural deformation characteristics are analyzed.Cracks occur late,but the number of cracks is large,the primary and secondary ribs can yield,and ultimately the main ribs will be destroyed,resulting in structural damage,and the structure shows good stiffness and ductility under load(2)Considering the inherent defects of the damage-plasticity constitutive model provided by ABAQUS,in order to comprehensively consider the material damage existing in the process of structural loading,the second development of ABAQUS software is carried out.By using the reflection algorithm,each incremental step of calculation is divided into elastic prediction,plastic correction and damage correction,and the cumulative effect of damage is considered.Based on the constitutive model of concrete material,concrete specimens and reinforced concrete beams are analyzed respectively.The results show that the constitutive model adopted in this paper has good accuracy and engineering applicability(3)Based on the constitutive model of concrete material with cumulative damage effect,the finite element numerical analysis model of Composite Ribbed network is established,and the mechanical properties of Composite Ribbed network under different influence factors are analyzed.The static performance of the structure is mainly affected by span,section size and rise-span ratio.It is found that the rise-span ratio has a significant effect on the damage of the structure.With the decrease of the rise-span ratio,the damage development of concrete materials will be delayed to a certain extent,and the damage location of concrete in the sub-rib intersecting joint area will shift to the direction of the main rib.The deflection of the structure is mainly affected by the span,and will be increased with the increase of the span.The height and width of rib section have a significant effect on ultimate bearing capacity,and the thickNess of rib plate is the secondary factor.With the increase of the size of composite rib section,the ultimate bearing capacity of structure will be greatly increased.With the expansion of material damage accumulation in structure,the mechanical performance of structure will deteriorate continuously,and the development of structural damage will experience from The damage degree of the main rib is higher than that of the secondary rib(4)Based on the experimental phenomena and the results of finite element parameter analysis,according to the damage distribution of the structure in different stress stages,the stress process of the structure is divided into five stages,namely,basic intact,slight damage,medium damage,serious damage and structural damage.In the process of loading,with the development of damage,plastic hinges are gradually formed in the joint area,and the final structure will behave as a local mechanism failure mode.In order to reflect the damage degree of each deformation area,the damage index of different damaged areas is constructed and the damage expression of the structure is obtained by linking the local damage of the structure with the deterioration of the overall performanceIn the formula,dz and dc denote the damage degree of the primary rib and the secondary rib respectively,?z and ?c denote the damage weight of the primary rib and the secondary rib respectively,indicating their importance in the structure.Their values are dz and dc corresponding to the primary and secondary rib when the structure reaches the ultimate load.Five performance stages of the structure are calibrated by the structural damage model.These five performance stages correspond to different ranges of structural damage factors.The preliminary validation of the model shows that the damage expression has certain accuracy.