4.SHEAR CAPACITY The steel tube in CFST column,is a kind of special form of reinforcement,and the three dimensional connous reinforcement field,acting as both longitudinal reinforcement and lateral stirrup.Usually,CFST mainly bears compression-bending effect,and the shear reinforcement field correspond is determined after the determination of the steel pipe specifications and hoop index according to the compression-bending member.so shear reinforcement design is not needed the other reinforced concrete member does.Previous test observation shows that failures are bending type when shear span to column diameter ratio a/D is larger than 2,and in the general construction project,the value is greater than 3.In some cases,such as large-span overloaded beam joints area,small shear span problem,which will influence the design of CFST,should be considered.In order to solve the problem,China construction science research institute carried ou the special shearing test research,which is applicable to transverse shear act on the pipe outer wall in pressure. Table 4 comparison of shear capacity of CFST with composite column types composite column shear capacity V≤(W+0.1N"1-0.45√a/D) V≤0.25[B.fmAm+fA(1+1.80)] V。=0.2Af.(1+30) Applicabl /D2and ransverse shear act on the conditions pipe outer wall in pressure others Consider the tube constraints'enhancing effect on the compressive strength 5.LOCAL COMPRESSION In addition,there are related regulations about local compression and tension and moment capacity for the CFST.but nothing for composite columns. 6.COMPOSITE RATIO In the composite co indifferent period,the coreCFSThas been under part verticl load,before the RCoutside ad aluetothe compression value ratio called composite ratio. 4. SHEAR CAPACITY The steel tube in CFST column, is a kind of special form of reinforcement, and the three dimensional continuous reinforcement field, acting as both longitudinal reinforcement and lateral stirrup. Usually, CFST mainly bears compression-bending effect, and the shear reinforcement field correspond is determined after the determination of the steel pipe specifications and hoop index according to the compression-bending member, so shear reinforcement design is not needed the other reinforced concrete member does. Previous test observation shows that failures are bending type when shear span to column diameter ratio a/D is larger than 2, and in the general construction project ,the value is greater than 3. In some cases, such as large-span overloaded beam joints area, small shear span problem, which will influence the design of CFST, should be considered. In order to solve the problem, China construction science research institute carried out the special shearing test research, which is applicable to transverse shear act on the pipe outer wall in pressure. Table 4 comparison of shear capacity of CFST with composite column types CFST composite column shear capacity ( 0.1 )(1 0.45 / ) V  V0  N  a D 0.2 (1 3 ) V0  Ac f c    0.25[  (11.8 )] c co co cc Acc V f A f Applicable conditions a/D<2 and transverse shear act on the pipe outer wall in pressure — others — Consider the tube constraints’ enhancing effect on the compressive strength 5. LOCAL COMPRESSION In addition, there are related regulations about local compression and tension and moment capacity for the CFST, but nothing for composite columns. 6.COMPOSITE RATIO In the composite column constructed in different period, the core CFST has been under part vertical load, before the RC outside casted. CFST’s vertical load value to the composite column’s axial compression value ratio called composite ratio