Failure Mechanism And Performance Evaluation Of Reticulated Shells Under Severe Seismic Motion Based On Damage Cumulative Constitutive Model

As a major form of large span space structures, reticulated shells developed fastin last30years for its excellent shape and mechanical behavior. China spans Circum-Pacific seismic zone and Eurasia seismic zone with frequent strong earthquakes.Huge amount of money needed for building or repairing before or after earthquakejustify the great necessity to evaluation the anti-seismic performance of reticulatedshells. However, the failure mechanism of reticulated shells under seismic motion, isnot well understood. Based on the mentioned above, this paper take a deeplyinvestigation on the failure mechanism of reticulated shells under seismic motionsbased on the damage cumulative constitutive model. And then the evaluation of anti-seismic performance of reticulated shells is completed. The main contents in thispaper are shown as following.1. Test on the hysteretic behavior of circular steel pipe and materialconstitutive model considering material damage cumulationThe setup applicable for three-dimensional loading is designed and then itsstability is verified by comparing test. Test is conducted on fifty circular steel tubeswith10groups of load schemes and their hysteretic behavior is investigated. Finite-element model is developed using a user-defined material sub-routine UMATencoded incorporating ABAQUS to consider material damage cumulation. Then, theparameters in the constitutive model is developed using the goodness of fit betweennumerical simulation and test results. Finally, a generalized constitutive modelconsidering damage cumulation is developed using the least square method with50groups of results. The numerical simulation using different material constitutivemodels is conducted. It is found through comparison that the perfect elasto-plasticcan only simulate the mechanics behavior in the range of elastic. Effect of damagecumulation becomes more and more obvious with increase of plasticity. The simulatecurves using the damage cumulative constitutive model are in good agreement withtest curves which proves not only the constitutive model is accurate but also the user-defined material sub-routine is applicable for theoretical analysis.2. Failure pattern of reticulated shells under severe seismic motion and ashaking table test on dynamic strength failureThe failure mechanism of single-layer reticulated shells considering damagecumulation under dynamic load is investigated by the material constitutive model and the UMAT using finite element software ABAQUS.The failure mechanism of single-layer reticulated shells considering damage cumulation under dynamic load isinvestigated. It is found that two failure patterns of the structure, dynamic instabilitydue to geometrical non-linearity and dynamic strength failure due to material non-linearity under dynamic load, are described. What is more, the performance ofstructure changes obviously especially its failure load decreases obviously whenconsider material damage cumulation. A shaking table test of single-layer reticulateddome is conducted to understand dynamic strength failure of single-layer reticulateddome under seismic motion. The free vibration property and the dynamic responsesof the single-layer reticulated dome under small or strong seismic motions areobtained; the performance of this model presents large deformation and obviousmaterial plasticity under seismic motion with an amplitude of1500cm s2whichindicates dynamic strength failure is appeared due to severe plastic development. Thenumerical simulation using different material constitutive models are conducted，the results show that the simulate curves using the damage cumulative constitutivemodel are in good agreement with test curves.3. The parametric analysis of failure mechanism of reticulated shells andstructrue damage modelThe vast scale parametric analysis of the failure mechanism of reticulated shellsis conducted by whole-course analysis method using the damage cumulative materialdamage model. The responses regularity of reticulated shells is investigated underdifferent ratio of rise to span, member cross-section, roof mass, length-width ratioand seismic motions. And then the failure characteristic and regularity of reticulatedshells under seismic motion is investigated by statistic analysis of the responsesunder different damage level. Based on the mention above, the damage state of thestructures under seismic motions is quantified using two structural damage models,one is based on multiple structural responses and another is based on deformationand energy.4. The seismic vulnerablity analysis of reticulated shells and anti-seismicperformance evaluation methodThe performance levels of reticulated shells are defined by its characteristic.And then the graded performance levels are quantified using structural damagemodel. The seismic vulnerability of the graded performance levels is conducted byconsidering the variance of different seismic motions. The exceeded probability ofearthquake with different intensities in a given design period is calculated using seismic hazard analysis. The failure probability of reticulated shells under earthquakeis calculated using the seismic hazard analysis and seismic vulnerability analysis.The anti-seismic performance evaluation of reticulated shells is completed using therelationship between structural failure probability and economic loss as well ascasualty loss.