钢管混凝土(SRC)短柱的轴向受压性能和强度分析

给出轴压下钢管混凝土短柱性能的试验和理论研究。共对14根圆钢管混凝土短柱和15根方钢管混凝土短柱进行试验,以研究钢管混凝土短柱的失效模式和轴压性能。分析了直径(或宽度)、相对厚度比对钢管性能的影响。试验结果表明:在相同配钢率的前提下,钢管混凝土短柱比普通混凝土短柱的受压承载力大。钢管的弹塑性分析可用于研究轴压下钢管混凝土短柱的破坏机理。基于已有的试验成果,提出求解钢管混凝土短柱的轴向受压强度的方程式。     

Behavior and strength of tubed RC stub columns under axial compression

This paper presents an experimental and analytical study on the behavior of axially compressed tubed RC stub columns. Forty specimens including twenty circular tubed RC (STRC) and twenty square tubed RC (STRC) stub columns were tested to investigate the failure mode and axial load strength of tubed RC columns subjected to axial compression. The effect of diameter/width to thickness ratio of the tubes and compressive strength of concrete were also studied. The effect of height to diameter/width ratio of the separated tube in tubed RC columns was studied to investigate the effect of bond and friction between tube and concrete on the behavior of tubed RC columns. Elastic–plastic analysis on the steel tube was employed to study the mechanism of tubed RC stub columns subjected to axial compression. Equations for the prediction of the ultimate axial load strength of tubed RC stub columns were proposed and the results from prediction were compared with the test results.     

轴力作用下钢管短柱的性能和强度分析

对轴力作用下钢管短柱的性能和强度进行了试验和数值分析。对包括20个圆形和方形钢管混凝土短柱在内的40个构件进行了试验,以分析其在轴压作用下的破坏模式和轴向承载强度。同时也对管的径(宽)厚比和混凝土的抗压强度的影响进行了分析。对钢管混凝土柱中管的高径(宽)比的影响进行分析,以探究钢管和混凝土之间的粘结和摩擦对钢管混凝土柱性能的影响。利用钢管的弹塑性分析研究轴压下短柱的受力机制。提出了公式用以预测钢管混凝土短柱的极限轴向承载强度,并将预测结果与试验结果进行了对比。     

方钢管约束钢筋混凝土轴压短柱试验研究与分析

进行了20个方钢管约束钢筋混凝土短柱的轴压力学性能试验研究,试验的主要参数为钢管宽厚比(50,70和100)和混凝土强度(C50,C80)。试验结果表明：方钢管约束钢筋混凝土柱中被分隔钢管的高度对其轴压承载力和延性无明显影响。随钢管宽厚比增大和混凝土强度的提高,轴压短柱的延性降低。采用弹塑性应力分析方法对钢管进行了全过程应力分析,分析结果表明,方钢管约束钢筋混凝土轴压短柱的峰值荷载点并不对应钢管的屈服点,钢管在轴压短柱达到峰值荷载后屈服。根据试验结果和钢管的应力分析结果,建立了方钢管约束钢筋混凝土短柱的轴压承载力计算式,试验结果与计算结果吻合良好。并提出了设计建议。图8表2参12     

圆CFRP-钢复合管约束高强混凝土短柱轴压试验研究

为研究圆CFRP-钢复合管约束高强混凝土短柱轴压受力性能,进行了6个CFRP-钢复合管约束高强混凝土（CFRP-steel composite tubed high-strength concrete,C-STC）柱和2个CFRP约束高强混凝土（CFRP-confined high-strength concrete,CC）柱、1个钢管约束高强混凝土（steel tubed high-strength concrete,STC）柱对比试件的轴压试验研究,得到了试件轴向荷载-位移曲线和CFRP及钢管的应变。结果表明：C-STC柱在轴压荷载作用下发生剪切破坏;约束模式对其前期刚度影响较小,相同CFRP层数的C-STC柱和CC柱的荷载-位移曲线第二线性段斜率近似相等;随着CFRP层数增多,短柱承载力和变形能力均能得到提高;钢管应力分析表明,STC柱钢管在峰值荷载附近屈服,C-STC柱钢管约在荷载-位移曲线第二线性段起点处屈服,钢材强度得到充分发挥。结合试验结果对已有文献中约束混凝土强度计算模型进行验证,并给出了建议的C-STC柱承载力计算式。     

Seismic behavior and strength of tubed steel reinforced concrete (SRC) short columns

The seismic behavior of tubed SRC short columns has been investigated by testing eight specimens subjected to combined constant axial compression and lateral cyclic load. Three circular tubed SRC columns (CTSRC) and three square tubed SRC (STSRC) columns were tested in this research with two common SRC columns for comparison. Different axial load ratios (n₀=0.3, 0.4 and 0.5) have been adopted for the constant axial load. The test results indicate that the shear strength, plastic deformation capacity, ductility index, and energy dissipating capacity of the tubed SRC short columns were much higher than those of the SRC columns with the same steel ratio and axial compressive load. The lateral load strength of CTSRC and STSRC short columns increased with an increment in axial load level, while the axial load ratio has no obvious effect on the plastic deformation capacity of CTSRC and STSRC short columns. The steel tubes prevented the shear failure of the concrete more effectively in the circular columns than in the square ones. Shear connector studs should be used in CTSRC and STSRC short columns to prevent bond failure between concrete and flanges of the steel section. A modified ACI design method was adopted to calculate the nominal shear strength of STSRC columns as well as CTSRC columns.     

Seismic behavior and moment strength of tubed steel reinforced-concrete (SRC) beam-columns

The seismic behavior of tubed SRC beam-columns has been investigated by testing six specimens subjected to combined constant axial compression and lateral cyclic load. Two circular tubed SRC columns (CTSRC) and two square tubed SRC (STSRC) columns as well as two common SRC columns as comparison were tested in this paper. Different axial load ratio (n₀ = 0.3 and 0.5) have been adopted for the constant axial load. The test results indicated that the flexural strength of a CTSRC column was much higher than that of a common SRC column with the same steel ratio and axial compressive load, whereas there was little difference on the flexural strength of a STSRC columns and a common SRC column. The ductility, plastic deformation capacity and energy dissipation capacity of CTSRC and STSRC columns were much higher than those of common SRC columns with the same steel ratio and axial compressive load. The flexural strength increased as the axial load ratio increased for CTSRC and STSRC columns, while an opposite trend was observed for the plastic deformation capacity. The flexural strength and plastic deformation capacity of CTSRC columns were clearly higher than that of the STSRC beam-columns with the same steel ratio and axial load ratio. A modified EC4 code method has been proposed for the calculation of the moment strength for tubed SRC columns.     

Behavior and strength of circular tube confined reinforced-concrete (CTRC) columns

An experimental investigation was conducted on the behavior of circular tube confined reinforced-concrete (CTRC) columns. Eighteen CTRC stub columns were tested under cyclic or monotonic axial compression. The results of the elastic-plastic analysis on the steel tubes indicate that the steel tube yields at the peak load point in the stub columns under axial compression. In addition, a design equation to calculate the axial load strength of CTRC columns is proposed. A total of five columns including one circular reinforced-concrete (CRC) column and four CTRC columns have been studied under combined axial compression and lateral cyclic load. The test results indicate that CTRC columns exhibit much higher flexural strength, displacement ductility and greater energy dissipation ability than CRC columns confined with hoop ties. The flexural strength increases as the axial load ratio or concrete compressive strength increases for CTRC columns, while the ductility is barely affected by the increase in axial load or concrete compressive strength. It is proposed that the moment strength of the cross section of CTRC columns can be calculated using a modified ACI code method.     

Mechanical performances of concrete-filled steel tubular stub columns with round ends under axial loading

An experimental study of 22 concrete-filled round-ended steel tubular (CFRT) stub columns under axial compression is conducted compared with 4 circular concrete-filled steel tubular (CFT) stub columns. The influences of width–thickness ratio, concrete strength, steel yield strength and wall-thickness of steel tube on the ultimate bearing capacity of the CFRT columns are discussed. The 3D finite element (FE) model is also developed to analyze the behavior of the CFRT columns under axial compression. From the results, local buckling of the round-ended steel tube associated with shear failure of in-filled concrete could be observed. With the increasing width–thickness ratio, the corresponding load–strain curves have a shorter elastic–plastic stage. The parametric studies indicate that the concrete strength, tube thickness and width–thickness ratio of the steel tube also have a great effect on the ultimate bearing capacity. The numerical results also show that the confinement effect of the stub columns decreases with the increasing width–thickness ratio. A practical calculation formula for the bearing capacity of the CFRT stub columns is proposed, which is well in agreement with the experimental results.     

方钢管约束型钢混凝土短柱抗震性能试验研究

进行了3个剪跨比为1.5的方钢管约束型钢混凝土短柱和1个相同用钢量的型钢混凝土对比试件的拟静力试验研究,试件的主要变化参数为轴压比(0.3,0.4和0.5)。试验结果表明：轴压比为0.3的方钢管约束型钢混凝土柱的破坏模式为弯曲破坏,而轴压比为0.4和0.5的方钢管约束型钢混凝土柱的破坏模式为剪切破坏和粘结破坏相结合。相同用钢量条件下,方钢管约束型钢混凝土短柱的受剪承载力、延性、层间变形能力和耗能性能明显优于型钢混凝土柱。随轴压比的增加,方钢管约束型钢混凝土短柱的受剪承载力提高,但延性和极限变形能力降低。对钢管的弹塑性应力分析结果表明：水平荷载施加过程中,发生弯曲破坏试件的钢管不屈服,而发生剪切破坏试件的钢管在下降段屈服。图8表2参13     

Experimental investigation on concrete-filled stainless steel stiffened tubular stub columns

This paper presents an experimental investigation on concrete-filled normal-strength stainless steel stiffened tubular stub columns using the austenitic stainless steel grade EN 1.4301 (304). The stiffened stainless steel tubes were fabricated by welding four lipped angles or two lipped channels at the lips. Therefore, the stiffeners were formed at the mid-depth of the sections. In total, five hollow columns and ten concrete-filled columns were tested. The longitudinal stiffener of the column plate was formed to avoid shrinkage of the concrete and to behave as a continuous connector between the concrete core and the stainless steel tube. The behavior of the columns was investigated using two different nominal concrete cubic strengths of 30 and 60 MPa. A series of tests was performed to investigate the effects of cross-section shape and concrete strength on the behavior and strength of concrete-filled stainless steel stiffened tubular stub columns. The measured average overall depth-to-width ratios (aspect ratio) varied from 1.0 to 1.8. The depth-to-plate thickness ratio of the tube sections varied from 60 to 90. Different lengths of columns were selected to fix the length-to-depth ratio to a constant value of 3. The concrete-filled stiffened stainless steel tubular columns were subjected to uniform axial compression over the concrete core and the stainless steel tube to force the entire section to undergo the same deformations by blocking action. The column strengths, load–axial strain relationships and failure modes of the columns are presented. Several comparisons were made to evaluate the test results. The results of the experimental study showed that the design rules, as specified in the European specifications and the ASCE, are highly conservative for square and rectangular cold-formed concrete-filled normal-strength stainless steel stiffened stub columns.     

Hysteretic behavior and design of square tubed reinforced and steel reinforced concrete (STRC and/or STSRC) short columns

The square tubed reinforced and steel reinforced concrete (STRC and STSRC) short columns are ordinary RC and/or SRC short columns where most of the lateral reinforcement is in the form of thin-walled steel tubes. In this study, six specimens of STRC and STSRC short columns were experimentally tested under constant axial compression and cyclic lateral load to investigate the seismic performance of both kinds of structure. The main parameters were the axial load ratio and status of longitudinal reinforcement. Nonlinear 3D finite element model was developed to simulate the monotonic behavior and strength of tested specimens. The behavior and strength of extra assumed specimens were predicted using the developed FEM model. Depending on the test and analysis results, a design formula was proposed to predict the shear strength of STRC and/or STSRC short columns.     

Behavior of square tubed reinforced-concrete short columns subjected to eccentric compression

This paper presents the experimental and theoretical studies on square tubed reinforced-concrete (TRC) short columns under eccentric compression. The main parameters of the test specimens included eccentricity and width-to-thickness ratio of the steel tube. The axial load versus lateral deformation curves, stresses in the steel tubes and the observed failure modes were discussed. The test results indicated that the eccentrically loaded specimens exhibited good ductile behavior with a bending failure mode. A new approach to determine the effective lateral confining pressure for TRC columns with square section was proposed. A numerical analysis model was developed to simulate the mechanical behaviors of square TRC short columns. Valuable attempts were made to describe the variation rules between the parameters in stress block method for tubed concrete and the magnitude of confinement. Furthermore, the axial force versus moment capacity interaction diagrams of square TRC columns were calculated.     

带肋方钢管混凝土轴压短柱试验研究及有限元分析

以方钢管宽厚比和加劲肋高厚比为主要变化参数,进行了14个带肋方钢管混凝土轴压短柱试验研究;同时采用有限元软件ABAQUS对带肋方钢管混凝土轴压短柱的荷载-变形关系进行了计算,计算结果与试验结果吻合良好。同时从应力-应变关系、核心混凝土和钢管的纵向应力分布及其相互作用等方面对比分析了无肋、单肋和双肋方钢管混凝土轴压短柱的受力性能。分析结果表明：设置加劲肋不仅提高了核心混凝土的纵向应力,而且明显减小了钢管管壁的拉应力区范围,改善了管壁的稳定性;带肋试件的约束作用主要集中在钢管角部和加劲肋处,随着每边加劲肋数量的增加,角部约束力明显增大。图13表1参11     

螺旋筋增强方钢管混凝土柱的轴压性能及参数分析

为研究螺旋筋增强方钢管混凝土(SRCFSST)柱的轴压性能,以螺旋筋间距、螺旋筋直径、螺旋圈与方钢管的径宽比、方钢管壁厚、混凝土强度等级、纵筋为变化参数,对23个短柱试件进行了轴心受压破坏试验。基于试验实测数据,就各变化参数对SRCFSST轴压性能的影响规律进行了深入的参数分析,其中在延性分析部分引入了基于耗能的延性系数。研究结果表明：SRCFSST试件的表观破坏形态与普通方钢管混凝土的相似;当螺旋筋配筋率≥1.5%时,荷载位移曲线由下降型转化为强化型,并出现四个关键特征点,破坏前预兆明显;在增加相同用钢量的条件下,增加螺旋筋的含钢量时承载力、峰值应变及延性均大幅提高,而增加方钢管和纵筋的含钢量时仅承载力有小幅提高,峰值应变、延性均无明显变化;基于参数分析的结果,对采用SRCFSST的轴压构件的最优配钢方式提出了设计建议。     

方钢管钢筋混凝土短柱与方钢管钢骨混凝土短柱的滞回性能分析及设计

方钢管钢筋混凝土短柱与方钢管钢骨混凝土短柱(STRC与STSRC)是将纵向钢筋置于冷弯薄壁钢管中。在这项研究中,对6根STRC和STSRC短柱进行固定轴压力下和往复侧向压力下的试验研究,分析两种构件的抗震性能。主要参数为轴压比和纵筋的配筋率。建立三维非线性有限元模型,模拟试件的性能和强度。基于试验和数值模拟结果,提出计算STRC和STSRC短柱剪切强度的设计公式。     

Behavior of thin walled steel tube confined concrete stub columns subjected to axial local compression

The behavior of thin walled steel tube confined concrete (STCC) stub columns subjected to axial local compression was experimentally investigated in this paper. A total of 46 specimens, including 36 STCC specimens and 10 plain concrete specimens, were tested. The main parameters varied in the tests are: (1) sectional types: circular and square; (2) local compression area ratio (concrete cross-sectional area to local compression area): from 1 to 25; (3) steel tube width (or diameter)-to-wall thickness ratio, B(or D)/t, from 52.1 to 104.7. It was found that the ultimate bearing strength of the composite sections decreases with increase local compression area ratio. The confinement action of the steel tube to core concrete and the ultimate strength of the locally loaded STCC specimens decrease with increase in steel tube width (or diameter)-to-thickness ratio. It was also found that, generally, circular steel tubes have higher confinement to their concrete core than those of the tubes with square sections when the composite members are subjected to axially local compression.     

Tests and calculations for hollow structural steel (HSS) stub columns filled with self-consolidating concrete (SCC)

The behaviour of self-consolidating concrete (SCC) filled hollow structural steel (HSS) stub columns subjected to an axial load was investigated experimentally. A total of 50 specimens were tested. The main parameters varied in the tests are: (1) sectional types: circular and square; (2) steel yielding strength: from 282 to 404 MPa; and (3) tube diameter or width to wall thickness ratio (D/t or B/t): from 30 to 134.A mechanics model is developed in this paper for concrete-filled HSS stub columns. A unified theory is described whereby a confinement factor (ξ) is introduced to describe the composite action of the steel tube and the filled concrete. The predicted load versus deformation relationship was in good agreement with test results. The theoretical model was used to investigate the influence of important parameters that determine the ultimate strength of the composite columns. The parametric and experimental studies provide information for the development of formulae for the calculation of the ultimate strength and the axial load versus axial strain curves of the composite columns. Comparisons are made with predicted stub column strengths using the existing codes, such as ACI-1999, AISC-LRFD-1999, AIJ-1997, BS5400-1979 and EC4-1994.     

Experimental study on behavior of circular concrete-filled high- strength steel tubular stub columns under compression

为了研究高强钢管混凝土短柱的承载性能，进行了13个高强圆钢管混凝土短柱轴压试验，从破坏模式、荷载-位移关系、承载力、残余承载力和延性方面对内填普通强度混凝土和超高性能混凝土的短柱受力性能进行了对比分析，研究了钢管强度、混凝土强度以及径厚比对两种钢管混凝土短柱的轴压性能影响。试验结果表明：钢管混凝土短柱的破坏模式与等效径厚比相关，分为腰鼓型破坏和剪切型破坏两种；在相同钢管强度及径厚比条件下，内填普通强度混凝土的短柱较内填高性能混凝土的短柱具有更高的承载力提高系数和残余承载力比，以及更好的延性。同时，将试验承载力结果与我国GB 50936—2014《钢管混凝土结构技术规范》、欧洲规范BS EN 1994-1-1：2004和美国规范ANSI/AISC 360-16中相关公式计算结果进行对比，发现现行规范一定程度上高估了高强钢管超高性能混凝土短柱的承载力。结合已有试验统计数据与高强圆钢管混凝土短柱试验结果，对圆钢管高强及超高强混凝土短柱受压截面承载力计算公式进行修正，得到偏安全的短柱轴压承载力计算公式。     

高强圆钢管混凝土短柱轴压承载力试验研究

为了研究高强钢管混凝土短柱的承载性能,进行了13个高强圆钢管混凝土短柱轴压试验,从破坏模式、荷载-位移关系、承载力、残余承载力和延性方面对内填普通强度混凝土和超高性能混凝土的短柱受力性能进行了对比分析,研究了钢管强度、混凝土强度以及径厚比对两种钢管混凝土短柱的轴压性能影响。试验结果表明：钢管混凝土短柱的破坏模式与等效径厚比相关,分为腰鼓型破坏和剪切型破坏两种;在相同钢管强度及径厚比条件下,内填普通强度混凝土的短柱较内填高性能混凝土的短柱具有更高的承载力提高系数和残余承载力比,以及更好的延性。同时,将试验承载力结果与我国GB 50936—2014《钢管混凝土结构技术规范》、欧洲规范BS EN 1994-1-1：2004和美国规范ANSI/AISC 360-16中相关公式计算结果进行对比,发现现行规范一定程度上高估了高强钢管超高性能混凝土短柱的承载力。结合已有试验统计数据与高强圆钢管混凝土短柱试验结果,对圆钢管高强及超高强混凝土短柱受压截面承载力计算公式进行修正,得到偏安全的短柱轴压承载力计算公式。