Seismic Performance Of Reinforced Slag-Based Geopolymer Concrete Beam-Column Interior Joint

As a new type of building material with environmental protection,slag-based geopolymer concrete has been received more attention by researchers.At present,however,the study on geopolymer concrete structure is mainly at the material level.The study on the performance of geopolymer concrete structure members is very few,which hinders its application in practical engineering.Beam-column joints are the most important and most complex members in frame structures,so studying their seismic performance is of great significance.The similarities and differences of seismic performance between geopolymer concrete beam-column joints and ordinary concrete beam-column joints and the influence of axial compression ratio,shear compression ratio,and bonding condition on geopolymer concrete beam-column joints are urgent problems to be studied and clarified.In addition,the applicability and improvement of the joint design control conditions in the ordinary reinforced concrete codes for the joints in geopolymer concrete beams and columns are also the key issues to promote the practical application of geopolymer concrete.In the present study,the seismic performance of the slag-based geopolymer concrete beams-columns joint was studied to the above problems,and the main work was as follows:(1)9 geopolymer concrete interior joint specimens and 3 ordinary concrete interior joint specimens were tested under low cyclic loading.The crack development and failure mode were recorded,and the hysteretic curve,strain of longitudinal bars and stirrups of beams and columns,shear deformation of the joint core of 12 specimens were obtained.Furthermore,the change law of hysteretic performances of specimens,such as ductility,strength degradation,stiffness degradation,and energy dissipation capacity,was analyzed.(2)The differences in seismic performance between geopolymer concrete interior joints and ordinary concrete interior joints were comparatively studied.It is found that there are significant differences in crack development during the failure of geopolymer concrete joints.In terms of ductility,strength degradation,stiffness degradation,energy dissipation capacity,and shear deformation in the joint core,regarding most performance,the geopolymer concrete joints are worse.(3)The effect of three axial compression ratios(0.1,0.3,0.5)on the seismic performance of reinforced geopolymer concrete beam-column joints at two shear compression ratios(high and low)was studied.The following conclusions were drawn: increasing axial compression ratio has a favorable influence on the seismic performance of the geopolymer concrete joints at low shear compression ratio,and there is a change law of first favorable and then unfavorable at the level of high shear compression ratio.(4)The applicability of the control conditions for the aseismic design of interior joints in the existing ordinary concrete design code to geopolymer concrete is evaluated.The control conditions in GB50010-2010 in China are not applicable,so it is suggested to modify the formula of seismic shear capacity,the upper limit of shear-compression ratio,and the control conditions of bonding condition.American code ACI318-19 is applicable to joints in geopolymer concrete except for the control conditions of bonding condition,so it is suggested that only the control conditions of bonding condition should be modified.