钢管混凝土短柱的抗震性能和抗剪强度分析

钢管混凝土短柱在地震中易遭受脆性剪切破坏。为评估圆形或方形钢管短柱的性能,对轴向恒载和侧向往复荷载组合作用下的8个短柱构件进行了测试。测试的构件包括3个圆形钢管柱和3个方形钢管柱,另外2个为普通钢筋混凝土短柱(其中一个为圆形柱,另一个为方柱)。试验结果表明:普通钢筋混凝土短柱在遭受脆性剪切破坏时延性很差,但由于外层薄钢管对核心混凝土的包裹作用,使得钢管混凝土短柱的延性明显增强。圆形钢管混凝土短柱的侧向承载强度随着轴向加载率的增大而增大,但轴向加载率对其塑性变形能力的作用不大。对于方形钢管混凝土短柱,抗剪强度会随着轴向加载率的增大而增大,但塑性变形能力会随着轴向加载率的增加而减小。钢管混凝土短柱中,圆形钢管比方形钢管能更有效地防止核心混凝土发生剪切破坏。基于试验和分析结果,采用了改进的ACI设计方法来计算方形和圆形钢管柱的名义抗剪强度。     

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.     

Shear strength and behavior of tubed reinforced and steel reinforced concrete (TRC and TSRC) short columns

Tubed RC and SRC short columns are special kinds of concrete filled tubular columns but the steel tube does not pass through the beam–column connection and is shorter than concrete core. In areas that suffered earthquakes, the short columns are vulnerable to brittle shear failure. TRC and TSRC short columns are widely used in bridges, high-rise buildings and large factories. So it is important to investigate the behaviors and approaches to improve the ductility of these kind of columns. The aim of this study is to develop a nonlinear finite element model (FEM) for TRC and TSRC short columns and to compare the results with those experimentally captured. Depending on the FEM results, the elastic–plastic method was used to analyze the stress status of the steel tube. A modified ACI design method is adopted to calculate the nominal shear strength of TRC and TSRC short columns based on the FEM and analysis results.     

方钢管约束钢筋高强混凝土超短柱抗震性能试验研究

本文进行3个剪跨比为1.5的方钢管约束钢筋高强混凝土超短柱和1个钢筋混凝土对比试件的试验研究,试验中的主要参数为轴压比(0.35,0.45和0.55)。试验结果表明,由于钢管对核心高强混凝土的约束作用和钢管的抗剪作用,方钢管约束钢筋混凝土超短柱的抗剪承载力、延性、变形能力和耗能性能明显高于钢筋混凝土超短柱。轴压为0.35的方钢管约束钢筋混凝土超短柱的破坏模式为弯曲破坏,而轴压比为0.45和0.55的方钢管约束钢筋混凝土超短柱的破坏模式为剪切破坏。随轴压比的提高,方钢管约束钢筋混凝土超短柱的抗剪承载力提高,但延性系数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可能在下降段屈服。根据试验结果和钢管应力分析结果建立方钢管约束钢筋混凝土柱的抗剪承载力公式,提出设计建议,可为工程实践提供参考。     

钢管约束钢筋混凝土转换短柱抗震性能试验研究

钢管约束钢筋混凝土短柱具有优越的延性和弹塑性层间变形能力,因此在转换柱中应用时可显著提高转换结构的整体抗震性能。对大连中国石油大厦外筒的钢管约束钢筋混凝土转换短柱进行了抗震性能模型试验,模型比例为1∶6。试验中的主要参数为轴压比、剪跨比和对拉钢筋设置。试验结果表明,钢管约束混凝土短柱中,钢管对核心混凝土的有效约束限制了核心混凝土剪切破坏的产生,改变了钢筋混凝土短柱在水平地震作用下的剪切脆性破坏模式。在抗震工程中采用钢管约束钢筋混凝土柱可有效提高钢筋混凝土框架短柱的延性、弹塑性层间变形能力和耗能性能,从而显著提高结构的整体抗震性能。     

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.     

钢筋混凝土框架短柱抗剪承载力分析

总结了国内外几个主要的钢筋混凝土框架短柱抗剪承载力计算公式,结合太平洋地震研究中心(PEER)的短柱抗剪拟静力试验数据库,对各公式进行了对比分析,得出各公式计算的短柱抗剪承载力与试验结果基本成线性关系的结论.     

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.     

Axial load behavior and strength of tubed steel reinforced-concrete (SRC) stub columns

This paper presents experimental and analytical studies on the behavior of tubed SRC stub columns subjected to axial compressive load. Fourteen circular tubed SRC (CTSRC) and fifteen square tubed SRC (STSRC) stub columns were tested to investigate the failure mode and axial loaded behavior of tubed SRC columns. The effect of diameter/width to thickness ratio of the tubes was studied. The effect of height to diameter/width ratio of the separated tubes in tubed SRC columns was studied to investigate the effect of bond and friction between tube and concrete on the behavior of tubed SRC columns. The test results indicated that tubed SRC stub columns exhibited higher axial load capacity than common SRC columns with the same volumetric steel ratio. Elastic–plastic analysis on the steel tube was employed to study the mechanism of tubed SRC stub columns subjected to axial compression. Equations for the prediction of the axial load strength of tubed SRC stub columns were also proposed based on the proposed experimental results.     

大连市体育馆钢管约束钢筋混凝土短柱设计

钢管约束钢筋混凝土柱就是在普通钢筋混凝土柱外设置薄壁钢管,钢管在梁柱节点区断开,不直接承担纵向荷载,只对核心混凝土起约束作用。由于钢管不通过梁柱节点区,因此钢管约束钢筋混凝土柱与钢筋混凝土梁连接方便;且钢管约束钢筋混凝土柱承载力高,抗震性能优越,是一种具有广泛应用前途的新型组合结构形式。钢管约束钢筋混凝土柱在大连市体育馆工程中的应用,解决了钢筋混凝土超短柱抗震性能差的问题;且钢管约束钢筋混凝土柱的用钢量低,施工方便,经济效益和综合效益显著。     

钢管混凝土和套管混凝土短柱的抗剪强度和性能分析

TRC和TSRC短柱都是钢管混凝土柱的特殊形式。在这两种短柱中,钢管并不会跨越梁柱连接,并且长度也短于混凝土核心筒。在地震区,短柱容易产生脆性剪切破坏。TRC和TSRC短柱广泛应用于桥梁、高层建筑和大型厂房,所以对短柱的剪切破坏及如何提高此类柱的延性便显得非常重要。研究目的是为TRC和TSRC短柱的计算开发一个非线性有限元模型,并将计算结果与试验结果进行对比。基于有限元计算结果,采用弹塑性方法来分析钢管的应力状态,并利用一个改进的ACI设计方法去计算TRC和TSRC短柱的名义抗剪强度。     

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。     

玄武岩纤维布约束钢筋砼柱的轴心受压试验研究

玄武岩纤维由于其良好的力学性能、较好的稳定性和较低的价格使其在土木工程中的应用前景广阔,但目前玄武岩纤维在土木工程中应用的相关研究还极少。通过15根外包玄武岩纤维布（BFRP）约束钢筋混凝土圆柱轴心受压试验,对其进行分析,并考虑箍筋对约束柱极限强度的影响,提出FRP承载力计算公式,计算结果和大量试验结果吻合良好,可供工程设计和进一步研究。     

Seismic behavior and strength of square tube confined reinforced-concrete (STRC) columns

A steel tube confined reinforced-concrete (STRC) column is an ordinary RC column where most of the lateral ties are in the form of a thin steel tube. Twenty-three square tube confined concrete stub columns were tested in this paper under cyclic or monotonic axial compression. A design equation to calculate the axial load strength of square tube confined concrete stub columns is proposed in this paper. A total of five beam-columns have been studied under combined axial compression and lateral cyclic loads. The test results indicate that the columns confined with square steel tubes exhibit much higher flexural strength, displacement ductility, and energy dissipation ability than common RC columns confined with lateral ties. Fiber models were also developed for STRC beam-columns in this paper.     

梁高对钢筋混凝土梁抗剪强度的影响

根据钢筋混凝土梁的抗剪强度随梁高的增加而降低的观点，分析了现行规范GBJ10-89中(4．2．3-2)和(4．2．3-4)公式中存在的不足，并对此提出修正，以供参考。     

高层建筑短肢剪力墙与异形柱结构受力分析

阐述了新的高层住宅结构形式中短肢剪力墙和异形柱两种结构的受力特点，并分析了各自的结构计算、构造的相关问题，以提高结构的安全保障力，满足人们对住宅空间的要求。     

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.     

Seismic behavior of code designed steel plate shear walls

The AISC Seismic Design Provisions now include capacity design requirements for steel plate shear walls, which consist of thin web plates that infill frames of steel beams, denoted horizontal boundary elements (HBEs), and columns, denoted vertical boundary elements (VBEs). The thin unstiffened web plates are expected to buckle in shear at low load levels and develop tension field action, providing ductility and energy dissipation through tension yielding of the web plate. HBEs are designed for stiffness and strength requirements and are expected to anchor the tension field formation in the web plates. VBEs are designed for yielding of web plates and plastic hinge formation at the ends of the HBEs.This paper assesses the behavior of code designed SPSWs. A series of walls are designed and their behavior is evaluated using nonlinear response history analysis for ground motions representing different hazard levels. It is found that designs meeting current code requirements satisfy maximum interstory drift requirements considering design level earthquakes and have maximum interstory drifts of less than 5% for maximum considered earthquakes. Web plate ductility demands are found to be significantly larger for low rise walls than for high rise walls where higher modes of vibrations impact the response. The percentage of story shear resisted by the web plate relative to the boundary frame is found to be between 60% and 80% and is relatively independent of panel aspect ratio, wall height, or hazard level, but is affected by transitions in plate thickness. Maximum demands in VBEs in design level shaking are found to be considerably less than those found from capacity design for SPSWs with 9 or more stories.     

Coating protection of loaded RC columns to resist elevated temperature

The objective of the present research work is to determine the effect of different coating types with different thicknesses on the residual load capacities of reinforced concrete loaded column models when subjected to symmetrical temperature rise up to 650 °C for 30 min. Seventeen RC column specimens with concrete cover 1.0 cm and a specimen dimensions 10×15×70 cm³ were cast and reinforced with 4∅6 mm longitudinal reinforcement and 7∅3.5 mm stirrups equally distributed along the height. The concrete mix is designed to give characteristic strength, f_cu, of 25 MPa. Siliceous gravel aggregate has been used in preparing the concrete mix. Among the 17 column models, there are two uncoated specimens. One of them was tested directly in ambient temperature and the other was exposed to elevated temperature up to 650 °C for 30 min. The remaining 15 specimens are divided into five groups. Each group is used to investigate certain type of coating. Five different types of coating have been used in this study namely traditional-cement plaster, perlite-cement, vermiculite-cement, LECA-cement and perlite–gypsum. Three different thicknesses of each type of coating have been used in this study 1.5, 2.5 and 3.5 cm. Every column specimen was equipped with eight thermocouples to measure the temperature distributions inside the specimen at mid height. An electric furnace has been used in this work. Every specimen was exposed to the simultaneous effect of the axial service load and temperature of 650 °C for 30-min period. The readings of applied loads and thermocouples were recorded at 5-min interval. Testing the columns after cooling to obtain their residual axial load capacity showed that, perlite proves to be the most effective plaster in increasing the loaded column's resistance to elevated temperature. Specimens coated with vermiculite cement came in the second place. Specimens coated with LECA-cement came in the third place. Finally, specimens coated with traditional-cement came in the last place.     

钢筋混凝土短柱抗震概念设计

结合震害和试验资料对工程中常见的钢筋混凝土短柱破坏机理进行了分析,并从抗震概念角度出发,提出提高短柱承载力和延性的几种常见工程设计建议,从而避免在强震中建筑结构的倒塌、破坏。