Research On The Modeling Method And Energy Dissipation Performance Of New Joint In Fabricated Structure

As a new type of joint connection for prefabricated concrete frame structure,unsymmetrical hybrid connection is characterized by merits including easy construction and shortened construction period.In recent years,this new type of joint has been adopted in some practical engineering projects including Tongxin Huayuan Kindergarten Project by Green Industry Investment Co.,Ltd.of China Construction Third Engineering Bureau.The joint of a prefabricated concrete structure plays a vital role in seismic behavior of the structure.For joint of unsymmetrical hybrid connection,the unbonded section of energy-dissipating bars is the important energy-dissipating part and initial length of this unbonded section is critical.Both domestic and overseas design specifications of concrete structures currently provide no specific design formulas and structural requirements for initial length of unbonded section of energy-dissipating bars.Finite-element analysis program currently adopted in academic research has shortcomings in various aspects including local stress and strain analysis,damage analysis and contact analysis.In addition,research achievements obtained lack specifics and cannot be regarded as applicable design basis.Therefore,it is urgent to propose a better method for modeling joints to establish more elaborate finite-element models for unsymmetrical hybrid connection joints and proceed more in-depth study of seismic behavior.In order to perform a sophisticated study of unsymmetrical hybrid connection joints and present solutions for designing initial length of unbonded section of energy-dissipating bars for structures adopted in Tongxin Huayuan Kindergarten Project,a method for establishing a three-dimensional finite-element model of connection joints is presented in this paper.Meanwhile,validity and reliability of this three-dimensional modeling method are verified by analyzing and comparing failure forms of the joints,curves of hysteretic loop,skeleton curves and strain of the reinforcement bars with low-cycle reciprocating tests on the unsymmetrical hybrid connection joints.In accordance with design data of south building of the Tongxin Huayuan Kindergarten Project and proven modeling method,3 sets of three-dimensional finite-element models of unsymmetrical hybrid connection joints are established.Energy-dissipating performance of the unsymmetrical hybrid connection joints and effect on the energy-dissipating performance of connections joints by unbonded section of energy-dissipating bars are analyzed in terms of curves of hysteretic loop,skeleton curves,energy-dissipating capability,and stiffness degradation.Analysis results indicate that reasonable initial length of unbonded section can ensure sufficient energy-dissipating performance and rotational stiffness of the joints.