Comparison of Steel Tube Concrete Column with Steel Tube Concrete Composite Column Name:于海燕 ID Number:1130598 Column occupies an important position for the structural engineers,as a kind of important component in architectural structures.For high-rise buildings,although structure systems are divers,columns are still essential vertical bearing components and lateral resistance components And,the form has being changed,from the normal reinforced concrete column,a steel reinforced concrete column,steel tube concrete column,to the composite column,mega columns.This report only introduces the related contents concerning concrete filled steel tube(CFST)column and concrete filled steel tube composite column(hereinafter referred to as the composite column). 1.BASIC CONCEPT 1.1 Concrete filled steel tube column:filling the high strength concrete into the steel pipe,is an economic efficient way to overcome the high strength concrete brittleness,by combining steel tube concrete technology with high strength concrete technology.This is because:1)steel tube's hoop constraint effect to core high strength concrete can effectively overcome the high strength concrete brittleness;2)steel tube can be used as a template,and has both longitudinal reinforcement and the transverse stirrup function,and facilitates to place high strength concrete, especially can use advanced pump concrete pouring process,because inside steel reinforced skeleton is not needed;3)without concrete cover outside,makes full use of the capacity of high strength concrete. 1.2 Composite column:consists of the core CFST and the concrete outside,can be as square section rectangular section or circular cross section.Composite column inside and outside parts can be constructed in different period,or in the same period.Construction in different period means first casting inside concrete to form CFST,bearing part of the vertical load during the period of construction then the outside concrete.Construction in the same period means casting the inside and outside concrete at the same time. The comparison shows that both consist of high strength concrete and steel tube,and the hoop sets effect gives full play to the role of high strength materials.The main difference is that, no concrete cover outside the CFST but composite column RC outside the pipe,also the inside and outside concrete can be casted in different periods.In short,CFST composite column is the development of concrete filled steel tube column 2.BUILDING MAXIMUM HEIGHT The second and third class high-rise building maximum height using composite column structure,for frame structure and 9 degree seismic fortification,is the same with A level height
Comparison of Steel Tube Concrete Column with Steel Tube Concrete Composite Column Name: 于海燕 ID Number: 1130598 Column occupies an important position for the structural engineers, as a kind of important component in architectural structures. For high-rise buildings, although structure systems are divers, columns are still essential vertical bearing components and lateral resistance components. And, the form has being changed, from the normal reinforced concrete column, a steel reinforced concrete column, steel tube concrete column, to the composite column, mega columns. This report only introduces the related contents concerning concrete filled steel tube (CFST) column and concrete filled steel tube composite column (hereinafter referred to as the composite column). 1. BASIC CONCEPT 1.1 Concrete filled steel tube column: filling the high strength concrete into the steel pipe, is an economic efficient way to overcome the high strength concrete brittleness, by combining steel tube concrete technology with high strength concrete technology. This is because: 1) steel tube’s hoop constraint effect to core high strength concrete can effectively overcome the high strength concrete brittleness; 2) steel tube can be used as a template, and has both longitudinal reinforcement and the transverse stirrup function, and facilitates to place high strength concrete, especially can use advanced pump concrete pouring process, because inside steel reinforced skeleton is not needed; 3) without concrete cover outside, makes full use of the capacity of high strength concrete. 1.2 Composite column: consists of the core CFST and the concrete outside, can be as square section, rectangular section or circular cross section. Composite column inside and outside parts can be constructed in different period, or in the same period. Construction in different period means first casting inside concrete to form CFST, bearing part of the vertical load during the period of construction, then the outside concrete. Construction in the same period means casting the inside and outside concrete at the same time. The comparison shows that both consist of high strength concrete and steel tube, and the hoop sets effect gives full play to the role of high strength materials. The main difference is that, no concrete cover outside the CFST but composite column RC outside the pipe, also the inside and outside concrete can be casted in different periods. In short, CFST composite column is the development of concrete filled steel tube column. 2. BUILDING MAXIMUM HEIGHT The second and third class high-rise building maximum height using composite column structure, for frame structure and 9 degree seismic fortification, is the same with A level height
high-rise building's largest height according to the current industry standard concrete tall building technical regulation JG.3-2010:in the non-seismic design and seismic fortification intensity6.7.8 area,except the frame structure,the maximum height for other structure is the same with B level height high-rise building's largest height according to the current industry standard concrete structures of tall building technical regulation JG/3-2010. Table 1 comparison of building maximum height of CFST with composite structures Structure system non-seismic seismic fortification intensitv(CFST/composite design(CFST/ column) compos it intensity 6 intensity 7 intensity 8 intensity9 column) frame 70 60 55 45 25 Frame-shear wall 170 160 140 120 Partial 50 120 100 No allowed frame-supported shear wall frame core-tube 240/220 260/210 210/180 160/140 80/70 Tube in tube 300/300 280/280230/230170/17080/90 The table data shows that,both the maximum height in tube structure are equal,it is important to note that the maximum height in the frame-core tube structure for composite column is smaller. 3.CAPACITY CALCULATION Confinement effect greatly improves CFST's bearing capacity(30%50%).and the materials stress under service conditions improved with the same amplitude corresponding.Test and theoretical analysis shows that,when the confinement index is within 3 and procedures set by safety level,CFST still in elastic stage under test load,which satisfy with the basic requirements Take the the research ast the nd r between the two on axial bearing capacity calculation. It can be seen from the form above: .The formulas about CFSTaxial compression capacity are basically agreed. 2.Processes are different when considers the different confinement effect.Generally the high strength concrete in the composite colum is within C55~C80 range or even larger,thus the CFS compression bearing capacity design value N.=0.9g,0Af1+V+60)<0.9p,9,Af1+V1.56+1.56)=0.9,0.A1+1.8) can be smaller than that of CFST composite column. 3.pressure tothe of bearing capacity
high-rise building’s largest height according to the current industry standard concrete structures of tall building technical regulation JGJ3-2010 ; in the non-seismic design and seismic fortification intensity6,7,8 area, except the frame structure, the maximum height for other structure is the same with B level height high-rise building’s largest height according to the current industry standard concrete structures of tall building technical regulation JGJ3-2010 . Table 1 comparison of building maximum height of CFST with composite column structures Structure system non-seismic design (CFST/ composite column) seismic fortification intensity(CFST/ composite column) intensity 6 intensity 7 intensity 8 intensity 9 frame 70 60 55 45 25 Frame-shear wall 170 160 140 120 50 Partial frame-supported shear wall 150 140 120 100 No allowed frame core-tube 240/220 260/210 210/180 160/140 80/70 Tube in tube 300/300 280/280 230/230 170/170 80/90 The table data shows that, both the maximum height in tube structure are equal, it is important to note that the maximum height in the frame- core tube structure for composite column is smaller. 3. CAPACITY CALCULATION Confinement effect greatly improves CFST’s bearing capacity (30% ~ 50%), and the materials stress under service conditions improved with the same amplitude corresponding. Test and theoretical analysis shows that, when the confinement index is within 3 and procedures set by safety level, CFST still in elastic stage under test load, which satisfy with the basic requirements of the limit state design principle. Take the CFST as the research object, and contrast the similarities and differences between the two on axial bearing capacity calculation. It can be seen from the form above： 1. The formulas about CFST axial compression capacity are basically agreed. 2. Processes are different when considers the different confinement effect. Generally the high strength concrete in the composite column is within C55 ~ C80 range or even larger, thus the CFST compression bearing capacity design value 0.9 (1 ) 0.9 (1 1.56 1.56) 0.9 (11.8 ) u l e c c l e c c l e c c N A f A f A f can be smaller than that of CFST composite column. 3. Composite column does not consider eccentricity axis pressure to the influence of bearing capacity
only consider the effect of slenderness ratios Although the CFST is set in the composite column when the steel pipe diameter to thecolum ng moment.To make sure there are certain reserves,fully axial compression bearing capacity can't be used,therefore limit the axial pressure.The reduction coefficient can be taken as 1.0 because of the RC outside 4.Equivalent calculation length.Composite column's equivalent length is calculated in accordance with the relevant provisions of the CECS28-90.Both of the two consider the constraint condition and bending moment distribution gradient effect. Table 2 comparison of axial compression capacity of CFST with the CFST in composite column types CFST column CFST in composite column Axis pressure N≤N, N≤0.9N design value Axial N。=0.9p,9.A.∫1+fe) N.=9f.A1+1.80) capacity reduction 9,=1-0.115L./D-4, 9=1-0.1150.1d。-4)2, coefficient(sl (L.1D>4) l.1d。>4) enderness ratio) 9,=1L./D≤4 9=1.0,1.1dn≤4 1 reduction 9.=1+1.85eo1m. e/r.≤1.55 without consideration 0.3 ratio) p。= %1g-041>1.5S Equivalent atio L。=k .=H length Note:L-the actual length of the column:H-length of the cantilever column Table3 comparison of axial compression capacity of CFST with composite column CEST column composite column axial N.=0.9g,,Af.1+f(0)N=0.9p(fAm+fA.)+fnA1+1.80 n capacity L。=kL Bottom columns:1.0H,others:125H Note:H for the bottom column can be taken the height from foundation top face to the first layer,H for the others each laver can be taken the height between the two top of the floor laver. Both the concrete inside and outside contribute the composite column axial compression capacity.and the interior CFST reduction coefficient is taken as 1.0.So the bearing capacity of
only consider the effect of slenderness ratios. Although the CFST is set in the composite column section center, mainly carrying axial compression, but when the steel pipe diameter to the column section side length ration is large, the CFST should bear the a small amount of bending moment. To make sure there are certain reserves, fully axial compression bearing capacity can’t be used, therefore, limit the axial pressure. The reduction coefficient can be taken as 1.0 because of the RC outside 4. Equivalent calculation length. Composite column’s equivalent length is calculated in accordance with the relevant provisions of the CECS28-90. Both of the two consider the constraint condition and column bending moment distribution gradient effect. Table 2 comparison of axial compression capacity of CFST with the CFST in composite column types CFST column CFST in composite column Axis pressure design value N Nu Ncc 9Nu 0. Axial pressure bearing capacity N 0.9 A f (1 f ( )) u l e c c (1 1.8 ) Nu 1 f cc Acc reduction coefficient(sl enderness ratio) ( / 4) 1 0.115 / 4 L D L D e l e ， l 1，Le / D 4 ( / 4) 1 0.115( / 4) 1/ 2 1 e a e a l d l d ， 1 1.0，le / da 4 reduction coefficient （eccentricity ratio） / 1.55 1 1.85 / 1 0 0 c c e e r e r ， / 1.55 / 0.4 0.3 0 0 c c e e r e r ， without consideration Equivalent calculation length Le kL le H Note: L-the actual length of the column; H- length of the cantilever column. Table 3 comparison of axial compression capacity of CFST with composite column types CFST column composite column axial compressio n capacity N 0.9 A f (1 f ( )) u l e c c 0.9( ) (11.8 ) u co co y ss cc Acc N f A f A f effective length Le kL Bottom columns：1.0H，others：1.25H Note: H for the bottom column can be taken the height from foundation top face to the first layer, H for the others each layer can be taken the height between the two top of the floor layer. Both the concrete inside and outside contribute the composite column axial compression capacity, and the interior CFST reduction coefficient is taken as 1.0. So the bearing capacity of composite column of is higher than that of CFST column
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[ (11.8 )] 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
The strength of empty steel pipe should be checked according to the construction stage load for the laminated column constructed in different period,and the maximum compressive stress value is unsuitable more than .6fa(fa is steel pipe steel the compressive strength of the design value).Composite than can be through the test are determined,usualy desirable-.6 composite ratio m=N /N M-composite ratio of composite column constructed in different period. N-Composite column axis pressure design value. compression design valueacton the CFST before the outer RCeasted If Composite ratio is too large,the requirements of the composite bearing capacity cannot be satisfied:If too small,the characteristics of composite column cannot be given full play. 7 BEAM COLUMN JOINTS Table 5 beam-column joints types of CFST and composite column types CFST column composite column I outer strengthen rings(smaller 1.only one steel beam,see column diameter） figure 5 Steel beam-column connection 2.inner strengthen rings (larger 2.all the steel beams,see column diameter) Transfer shear:I ring bracket 2.Bearing pin 2.Steel plate fin transformation Transfer bending moment: 3.Steel pipe reinforced RC beam-column connection 1.Well type double beam transformation (Construction in the 2.ring be m 3.wear muscle ame period) single-girder 4.various width beam Note:the shear transfer and moment transfer forms are introduced respectively in the CFST structure,and Suitable forms combination is need in practice. 7.1 CFST structure 7.1.I Steel beam-column connection:
The strength of empty steel pipe should be checked according to the construction stage load for the laminated column constructed in different period, and the maximum compressive stress value is unsuitable more than 0.6fa(fa is steel pipe steel the compressive strength of the design value). Composite than can be through the test are determined, usually desirable 0.3-0.6. composite ratio m Ni / N M—composite ratio of composite column constructed in different period. N—Composite column axis pressure design value. Ni—axis compression design value act on the CFST before the outer RC casted If Composite ratio is too large, the requirements of the composite bearing capacity cannot be satisfied; If too small, the characteristics of composite column cannot be given full play. 7 BEAM COLUMN JOINTS Table 5 beam-column joints types of CFST and composite column types CFST column composite column Steel beam-column connection 1 outer strengthen rings (smaller column diameter) 2. inner strengthen rings (larger column diameter) 1. only one steel beam, see figure 5 2. all the steel beams, see figure 6 RC beam-column connection Transfer shear: 1 ring bracket 2. Bearing pin 1. Steel pipe breakthrough type 2. Steel plate fin transformation 3. Steel pipe reinforced transformation (Construction in the same period) Transfer bending moment: 1. Well type double beam 2. ring beam 3. wear muscle single-girder 4. various width beam Note: the shear transfer and moment transfer forms are introduced respectively in the CFST structure, and Suitable forms combination is need in practice. 7.1 CFST structure 7.1.1 Steel beam-column connection：
Figure 1 outer strengthen rings nner strengthen rings 7.1.2 Steel beam-column connection transfer shear Figure 2 ring bracket Bearing pin 7.1.3 Steel beam-column tra Figure3 Well Type Double Beam Ring Beam Well type double beam:1-CFSTcolumn:2-longitudinal reinforcements of double beam: 3-Additional inclined bars Ring beam:1-CFST colm:2the ring bars of ring beam:3longitudinal reinforcements of frame beam:4-stirrups of ring beam
Figure 1 outer strengthen rings inner strengthen rings 7.1.2 Steel beam-column connection transfer shear： Figure 2 ring bracket Bearing pin 7.1.3 Steel beam-column connection transfer bending moment： Figure 3 Well Type Double Beam Ring Beam Well type double beam：1—CFST column；2—longitudinal reinforcements of double beam； 3—Additional inclined bars Ring beam：1—CFST column；2—the ring bars of ring beam；3—longitudinal reinforcements of frame beam；4—stirrups of ring beam
Figure 4 wear muscle single-girde arious width beam 7.2 composite column 7.2.1 Steel beam-column connection: 悬臂梁段4420，焊缝承载力提高1.5倍 】型钢梁 海瓣土梁 混凝土 4920 运： 已1型钢梁 悬臂梁段 混凝土梁 浇筑孔 Figure 5 only one steel beam
Figure 4 wear muscle single-girder various width beam 7.2 composite column 7.2.1 Steel beam-column connection： Figure 5 only one steel beam
高强螺栓 多边形环状悬臂梁段 十字钢板加劲肋 I型钢梁 学 型钢粱」 浇筑孔 钢粱瘦板连接 Figure 6 all the steel beams 7.2.2 RC beam-column connection 梁纵筋 楼板上留浇筑孔浇筑孔 Figure 7Steel pipe breakthrough type 上层钢管 上层翅片 A 管外连接竖筋 12环箍 核心钢管 下层翅片 下层钢管
Figure 6 all the steel beams 7.2.2 RC beam-column connection： Figure 7 Steel pipe breakthrough type
管外连接竖筋用 柱箍筋 翅片 核心钢管】 必要时如此纵筋 管外连接竖筋 与管外连接竖筋焊接 外设筋筋 Figure Stee plate 翅片 淡孔 浇筑孔 翅片 环雍 混凝土分附网月 深：“必要丽设加劲板 必要时设加劲板核心钢管 翅片打 焊缝绑梁纵筋 绑条10 趨片
Figure 8 Steel plate fin transformation Figure 9 Steel pipe reinforced transformation
