Research On The Performance Of A New Prefabricated Concrete Columns Strengthened Locally By UHPC Shell

Building industrialization can effectively reduce labor intensity,standardize and accelerate the construction process,and reduce environmental pollution in line with the concept of green environmental protection under the premise of ensuring construction quality.Therefore,under the new situation of transformation and upgrading of the construction industry,green development and improvement of efficiency and quality,building industrialization is being carried forward in full swing.Precast concrete frame structure has become one of the most important structural forms in the field of building industrialization due to its components such as beams and columns that are easy to be modularized and standardized.At the same time,with the continuous breakthroughs in the field of building materials,Ultra-high Performance Concrete(UHPC)with ultra-high strength,high toughness and high durability has made great progress and has been preliminarily applied in the field of infrastructure construction.The combination of UHPC and precast concrete columns can achieve complementary advantages,reduce the risk of local damage and improve its seismic performance.This paper is based on the Natural Science Foundation-Seismic Behavior and Design Method of the Precast Concrete Frames Strengthed Locally by Prefabricated UHPC Shells(5180081127).Since there are a large number of vertical interface between UHPC shell and post-cast concrete,this paper start with the study on the influence of different interface treatment methods on the shear performance of UHPC-NC interface.Based on the study of interface level,the prefabricated UHPC shells are used to strengthen the weak part of the prefabricated concrete column.A new type of UHPC-NC composite prefabricated column is proposed,and its seismic performance is studied.The main work and conclusions are as follows:(1)At the interface research level,the UHPC-NC interface shear performance test is carried out.The test specimens are divided into two which was divided into two types of rebar with or without interfacial pin bolt,including three types of bubble film,three types of keyway,water washing and other interfacial treatment methods,with a total of 18 z-shaped shear specimens.Based on the analysis of test results such as load-slip curve,shear strength,shear stiffness,and interface roughness,the 28 mm bubble film was finally selected as the vertical interface treatment method for component level research.(2)At the component research level,the full-scale quasi-static load experimental study of prefabricated concrete columns strengthened locally by UHPC shell was carried out.The experimental specimens include a cast-in-place control specimen,a traditional prefabricated column control specimen,and four new UHPC-NC composite prefabricated column specimen.The experimental results and phenomena were analyzed systematically,including failure pattern,hysteresis curves,skeleton curves,strength,stiffness,deformation capacity,energy dissipation capacity and stress of rebars.It is showed that the new type of prefabricated column proposed in this paper can effectively avoid local damage at the foot of the column,and the seismic performance is better than traditional prefabricated columns in some respects.(3)Finite element analysis software ABAQUS was used to establish the finite element model of the new precast column.By comparing the simulation results with the experimental results,the accuracy and reproducibility of the model were verified.Based on this model,the influence of key parameters such as thickness,height,volume stirrup ratio of UHPC shell and axial compression ratio on the performance of the new precast concrete columns was studied through parametric analysis.Finally,the research contents and results of this paper are summarized.According to the experimental results and the finite element parametric analysis,the optimization and improvement suggestions of prefabricated concrete columns strengthened locally by UHPC shell are put forward,and the problems to be solved and the possible research directions in the future are prospected.