Research On The Progressive Collapse Resisting Performance Of Spatial Truss Structure

With the rapid development of economy,large-span space structures are widely used in the large public architectures,such as terminal buildings,stadiums,exhibition hall and so on.Such buildings are usually densely populated.Once the event of collapse happened,it would cause serious casualties and property losses.So it is very important to study the anti-collapse performance of large-span space structures.The spatial truss structure is researched,the deep analysis of the progressive collapse resisting performance of one stadium steel roof is carried out.And two types of loads are considered,extreme snow load and earthquake action.ABAQUS was used to make the numerical simulation of the spatial truss.Sensitivity index was presented based on the stress ratio and sensitivity analysis was carried out under the static effect.The distribution pattern of sensitive components and key components were acquired.Moreover,effects of the height-span ratio,structural span and its cross-section form on the progressive collapse performance of spatial trusses were also analyzed.The progressive collapse modes subjected to extreme load were simulated.Initial failure members were introduced by setting predefined fields and the damage cumulative effect was considered in the progressive collapse analysis of the spatial truss structure subjected to earthquakes.Under the different failure modes of the structure,dynamic responses including failure acceleration,ultimate displacement and yield elements ratio were investigated.Effective measures were proposed to improve the progressive collapse performances.The theoretical basis for the engineering design of the spatial truss structure was provided.The main conclusions are as follows:1)The sensitive components of structures with inverted triangular cross-section are upper chord members and web members(A and B-type)at end-span,while the sensitive components of structures with positive triangular cross-section form are lower chord members at mid-span and web members(A and B-type)at end-span.Key components are the A-type web members near the supports.The progressive collapse performance of the structure can be improved effectively by increasing the sectional area of key components.2)With the increase of the height-span ratio and the decrease of the structural span,both of the sensitivity index at the same position and the distribution range of sensitive components increase in spatial trusses with the same stress ratio.When the initial failure is the upper chord member,subsequent failure members are less and the structure collapses more suddenly compared to the A-type and B-type web member.Under the static effect,the ultimate displacement of the spatial truss structure is at the range of 1/100 to 1/70 of the span.3)The weak positions are the upper chords and the lower chords in the mid-span of the main truss within the scope of 3/8L as well as the upper chords of the middle support truss.When the initial failure is introduced,the failure acceleration of the structure decreases from 13.3% to 40.0% and ultimate displacement decreases from 1.6% to 30.9% which are at the range of 1/90 to 1/65 of the span.While the initial failure is the compression member,dynamic instability failure occurs.While the initial failure is the tension member,dynamic strength failure occurs.4)After setting cross diagonal bracings,the out-of-plane buckling of the main truss is effectively restrained and the anti-collapse performance of the structure is improved.The failure acceleration increases from 5.8% to 73.7% and ultimate displacement decreases at the range of 1/145 to 1/80 of the span.Meanwhile,dynamic strength failure occurs.