【正文】 behavior of t he abnormal joint s in re2 al st ructure and the seismic behavior of st ructure. Fig. 5 shows the p hoto of model . The test includes two step s. The fir st is the p seudo dynamic test . At t his step , El2Cent ro wave is inp ut and the peak acceleration varies f rom 50 gal to 1 200 gal . The seismic response is measured. The second is t he p seudo static test . The loading can’ t stop until t he model fail s. Fig. 7 Minor core The experiment shows t hat t he dist ribution and development of t he crack is influenced by t he rest rictive effect of the ort hogonal beam , and t he crack of joint core mainly dist ributes under t he orthogonal beam ( see Fig. 6) , which is different f rom t he result of t he plane joint test , but similar to J 4210. 3. 3 Analysis of test results 3. 3. 1 Mechanical analysis In t he experiment , t he location of the initial crack of t he exterior joint and the crushed position of concrete both appear in the middle of t he joint core , and t he position is near t he centerline of t he upper col2 umn. The initial crack and crushed position of t he concrete of the interior joint both appear in t he mi2 nor core ( see Fig. 4 ,Fig. 7) . For interior abnormal joint t he crack doesn’ t appear or develop in t he ma2 j or core out side of the mi nor core until t horough cracking takes place , while t he crack seldom appears in t he shadow region ( see Fig. 7) as the joint fail s. Therefore , for abnormal joint , t he shear capacity of t he joint core depends on t he properties of t he mi nor core , namely , on t he st rengt h grades of concrete , t he size and the reinforcement of t he mi nor core , get t he effect of t he maj or core dimension can’ t be neglected. Mechanical effect s are t he same will that of t he normal joint , when t he forces t ransfer to t he mi2 nor core t hrough column and beam and reinforcement bar . Therefore , t he working mechanisms of nor2 mal joint , including t russ mechanism , diagonal pression bar mechanism and rest rictive mechanism of stirrup , are also suitable for mi nor core of t he abnormal joint , but their working characteristic is not symmet rical when the load rever ses. Fig. 8 illust rates t he working mechanism of t he abnormal joint . When t he load t ransfer to mi nor core , t he diagonal pression bar area of mi nor core is bigger t han normal joint core2posed by small column and small beam of abnormal joint , which is due to t he pressive st ress diff usion of concrete pressive region of the beam and column , while at t he same time t he pression carried by the diagonal pression bar bees large. Because t he main part of bond force of column and beam is added to t he diagonal p ression bar but cont rasting wit h t he increased area of diagonal pression bar , t he increased action is small . The region in the maj or core but out of the mi nor core has less st ress dist ribution and fewer cracks. The region can confine t he expansion of t he concrete of t he mi nor core diagonal pression bar concrete , which enhances t he concrete pressive st rengt h of mi nor core diagonal pression bar . Making t he mi nor core as st udy element , the area increment of concrete diagonal pression bar in mi nor core is related to t he st ress diff usion of t he beam and column pressive region. The magni2 t ude of diff usion area is related to height difference of t he beam sections and column sections. Name2 ly , it is related to t he size of mi nor core section and maj or core section. Thus , the increased shear st rengt h magnit ude caused by mi nor core rest rictive effect on maj or core can be measured quantitative2 ly by t he ratio of maj or core area to mi nor core area. And it al so can be expressed that t he rest rictive effect is quantitatively related to t he ratio. Obviously , t he bigger t he ratio is and t he st ronger t he con2 finement is , t he st ronger t he bearing capacity is. The region in the maj or core but under the mi nor core still need stirrup bar because of t he hori2 zontal force t ransferred by bigger beam bar . But force is small . 3. 3. 2 load2displacement curves analysis Fig. 9 shows t he typical load2displacement curves at t he beam end of t he exterior and interior joint . The figure showing t hat t he rigidity of t he specimens almo st doesn’ t degenerate when t he initial crack appear s in t he core , and a turning point can be found at t he curve but it isn’ t very obvious. Wit h t he crack developing , an obvious t urning point can be found at t he curve , and at t his time , t he speci2 men yields. Then t he load can increase f urt her , but it can’ t increase too much f rom yielding load to ultimate load. When t he concrete at t he core collap ses and the plastic hinge occured at t he beam end , t he load begins to decrease rat her t han increase. The ductility coefficient of two kinds of joint s is basically more than 3 (except for J 3 9) . But it should be noted t hat the design of specimens is based on the principle of joint core failure. The ratio of reinforcement of beam and column tends to be lower t han practical project s. If t he ratio is larger , t he failure of joint is probably prior to t hat of beam and column , so t he hysteretic curve reflect s t he ductility property of joint core. Joint experiment should be a subst ruct ure test (or a test of posite body of beams and col2 umns) . So t he load2displacement curves at t he beam end should be a general reflection of t he joint be2 havior work as a subst ruct ure. Providing t hat the joint core fails af ter t he yield of beam and column (especially for beam) , t he load2displaceme