Research On The Overall Stability Of Prestressed Angled Crossarm Stringer

The stringed beam structure is a new type of space structure that has emerged in previous years.After years of development,stringed beam structure is no longer a simple structure with a vertical brace and cable system as a whole.Especially the arrangement of the crossarm,with the continuous deepening and development of research in this field,many different configurations have been gradually derived from the original single vertical brace arrangement.Although there are many configurations of the stringed beam,the core of the same is that the structure connects the bending member and the tensile member through the struts,and at the same time applies a certain prestress to the cable to improve the stability and Carrying capacity.At the same time,the prestress will cause a certain reverse arch of the structure.After the load and self-weight are generated,the structure will basically return to the initial state.In this paper,based on the model of the plane diagonal brace string structure,the finite element software ABAQUS is used to model the various mechanical properties of prestressed angled crossarm string structure under concentrated load or uniform load.In addition,this paper uses the structure height,brace angle and cable diameter and the connection methods of beams and crossarm to derive plane prestressed angled crossarm stringer with different configurations.A total of 240 cases of prestressed angled crossarm stringer are established.First,structural statics is used to derive the initial prestress of the cable under two different connection methods in this paper: the crossarm is rigidly connected to the beam and the crossarm is hinged to the beam.Secondly,linear analysis is performed on several structural models to obtain the buckling load and buckling modes of the structure,and the linear analysis results of the structures under different connection modes are compared.At the same time,the nonlinear analysis of the structure is also within the scope of the study and the analysis results are output;the relationship between the mid-span displacement and the bearing load is used to make statistics and in-depth research on the maximum bearing capacity of all configurations.After the above analysis and research,not only has a comprehensive understanding and analysis of the prestressed diagonal brace string structure,but also can be optimized in different structures,and provides avaluable reference for practical engineering.The main results of this study are:1.A method for determining the initial prestress is proposed for this research object.Based on this method,the expression of initial prestress is obtained and verified.In this paper,the structure height,brace angle and cable diameter are taken as the structure's own properties to explore their influence on prestress.The results show that the relationship between the initial prestress and the cable diameter is negatively related,and the prestressed hinged structure of the rigid structure with the same configuration is larger.The magnitude of the prestress of the two structures is negatively related to the structural sagittal height and the prestress of the rigid structure is greater,but the prestressing gap between the two structures gradually decreases with increasing sagging height;There is a negative correlation between the initial prestress of a rigidly connected structure and the crossarm angle,The relationship between the initial prestressing force of the hinged structure and the brace angle is positively correlated.2.The modeling process of prestressed braced string beams in ABAQUS is described in detail.The linear buckling modal was calculated by the linear analysis and the results of buckling load were studied.The statistics show that all the configurations exhibit a total of five buckling modal shapes and this paper names the five buckling modal shapes.Among them,the number of the structure's mode showing the two half-wave shapes in the forward direction and the two half-wave shapes in the reverse direction increases with the increase of the strut angle and the structure vector height of the research subject.When the sagittal height of the structure and the angle of the crossarm are too large,the instability of the crossarm will occur in the prestressed string,and the hinge structure is particularly obvious.The buckling load of the structure has a negative correlation with the cable diameter;the crossarm angle has a greater effect on structures with larger sagittal heights,and also has a negative correlation;After comparison,it is found that the buckling load of rigid structures is generally greater than the buckling load of hinged structures when the structure's sagittal height is small,the advantage of buckling load of the small cable diameter rigid connection structure is obvious.3.Based on the calculation formula of the initial prestress,the buckling mode andbuckling load in the linear analysis,this paper presents the preparations and specific steps for the nonlinear analysis of the prestressed angled crossarm string structure.The nonlinear analysis results under the two conditions of concentrated load and uniform load show that the maximum bearing capacity of the structure under the concentrated load is positively related to the cable diameter and the sagittal height of the structure.The results show that the maximum bearing capacity of the structure under concentrated load is positively related to the cable diameter and sagittal height of structure.The maximum bearing capacity of a small cable diameter structure will decrease as the crossarm angle increases,while the maximum bearing capacity of a large cable diameter structure will increase as the crossarm angle increases.It was found that the hinged structure needs to be equipped with a cable system with a higher tensile strength by introducing a cable with a tensile strength of 1470 MPa as a reference.In addition,this article's research on the uniform load conditions only focuses on specific configurations.Select the specific structural sagittal height,cable diameter,crossarm angle and explore using the control variables.Analysis shows that for this particular configuration,the maximum bearing capacity is positively related to the sagittal height of the structure and the cable diameter;the effect of the crossarm angle on the overall stability of the structure is not obvious.Only when the crossarm angle is too large can the structural stability be improved.The arrangement of the angled crossarm has created more possibilities as an innovation point of this research object.This paper focuses on the effects of structural sagittal height,brace angle,and cable diameter on overall stability,and conducts a more comprehensive analysis and research on the prestressed angled crossarm prestressed string from different angles.It is expected to provide effective reference and help for the future research work of this kind of structures.