Secondary Development Of ABAQUS Fiber Beam-Column Element And Its Application In Seismic Analysis Of Bridges

The key to elastoplastic seismic response analysis of bridge structures is to select nonlinear beam-column elements that can accurately simulate the nonlinear mechanical behavior of ductile pier members.Compared with the solid element and the concentrated plastic hinge element,the elastoplastic fiber beam-column element has both computational efficiency and accuracy and has been widely used in seismic analysis of civil engineering structures.In this thesis,an elastoplastic fiber beam-column element is developed by using the secondary development function of the general finite element software ABAQUS and applied to the seismic research of bridges.The main research contents of the thesis include:(1)Using the UMAT program interface provided by ABAQUS,a variety of constitutive models suitable for three-dimensional elastoplastic analysis of fiber-beam elements are developed,including two concrete constitutive models(Concrete01,Concrete02)and four steel constitutive models(Steel01~Steel04).The concrete constitutive models can be used to model both the unconfined and confined cocrete material fibers of the reinforced concrete column sections while the steel constitutive models can be used to model the steel material fibers of the sections.(2)Numerical tests of single-material comlumns were conduted to validate the the correctness of the steel constitutive model.The loading conditions considered in the test include both axial and lateral monotonic or cyclic loadings.The elasto-plastic response of the columns members under all loading conditions have shown full compliance with the theoretical expectations.Two pseudo-static experiments of reinforced concrete columns are numerically simulated with the developed elastoplastic fiber beam-column element to show its applicability and good convergence.The numerical hysteresis curves of different steel constitutive models are basically consistent with the experimental hysteresis curves,especially those of Steel03 and Steel04.(3)The elastoplastic fiber beam-column element developed by ABAQUS is applied to the calculation of bridge pier deformation capacity in combinitiaon with the seismic design code of bridges in China.The static elastoplastic analysis method is used to study the displacement capacity of bridge piers under earthquake actions.Based on the specification,two methos for calculating the allowable displacement of the piers are compared,namely,the method by using the plastic hinge length and method of using the crititcal plastic hinge zone section curvature as the control parameters.The results show that even if the second method is used,the calculated displacement capacity of piers is still dependant on the length of the plastic hinge.The allowable displacement decreases as the length of the plastic zone element decreases.When the value is equal to the standard value,the numerical result of the allowable displacement is consistent with the standard calculation result.When the length of the plastic hinge element is less than the specified value,the calculated allowable displacement result is safe.(4)Based on the developed fiber beam-column element,the ABAQUS software is used to establish the finite element model of a reinforced concrete continuous rigid frame bridge for dynamic time history analysis under seismic actions.The strength check of the bridge under the action of E1 earthquake and the deformation check under the action of E2 earthquake were carried out.The main novelties of the thesis include:(1)The exstiting constitutive model Steel01 which considers the end bond slip of reinforced concrete columns was realized in ABAQUS for the first time.Furthermor,two new constitutive models,namely Steel03 and Steel04 were proposed based on the exist models.The Steel03 model adjusts the loading and unloading hysteresis rule based on the existing model to make it more reasonable to consider the Bauschinger effect.The Steel04 model introduces the strength degradation and end bond slip caused by cumulative damage based on the existing model.Both constitutive models can simulate the elastoplastic seismic response of reinforced concrete piers very well.(2)The static elastoplastic analysis of the pier is realized in the ABAQUS software with the self-developed fiber beam-columns element for the first time and the idea of calculating the allowable displacement of the pier according to the specification is proposed.The work of this thesis greatly enriches the steel and concrete material libraies of the ABAQUS/standard module.The developed elastoplastic fiber beam-column element has been shown to be suitable to 3D seismic analysis of brideges.And the present work has provided a good reference on how to use the fiber beam-column element in ABAQUS in combination with the Chinese seismic design specifications for seismic analysis of full bridges.