《4.4.ReinforcedConcreteColumn汇总》由会员分享，可在线阅读，更多相关《4.4.ReinforcedConcreteColumn汇总（42页珍藏版）》请在金锄头文库上搜索。
1、4.4 4.4 Reinforced Concrete Column4.4.1 Types of ColumnnColumns are defined as members that carry loads chiefly in compression.nColumns carrynaxial compressive loadsnbending momentncompression forces dominate. 4.4.1 Types of ColumnnUsually columns carry bending moment as well, about one or both axes
2、 of the cross-section. bending moment about y axisnBending action may produce tensile force over a part of the cross-section. Classification of ColumnsnBased on loadingnAxially loaded columnnEccentrically loaded columnnBiaxially loaded columnseccentrically ik5sentrikEliik5sentrikEli. 偏轴地偏轴地Biaxially
3、 loaded columnsAxially loaded columnClassification of ColumnsAxially loaded columnloads are assumed acting at the centroid of column section.centroidcentroid 5sentrCid5sentrCid 质心质心偏心受力偏心受力MNcNte0=M/NcNce0=M/NtNt转化为Nce0load acts at a distance e from the centroid of column section. Eccentrically load
4、ed columnClassification of ColumnsThe distance e could be along the x or y axis, causing moments either about the x axis or y axis.moments about the y axismoments about the x axisEccentrically loaded columnClassification of ColumnsnBiaxially loaded columnsnload is applied at any point on the column
5、section, causing moments about both the x axis and y axis simultaneously.Biaxially loaded columnsClassification of ColumnsnBased on lengthnShort columnsnLong columnsnShort columnsncolumns failure is due to ncrushing of concrete nyielding of steel barsnReach full load capacity upon failuren Long colu
6、mns (slender columns)长柱长柱nbuckling effect 屈曲屈曲and slenderness ratio长细比长细比must be taken into considerationnreducing the load capacity of the column relative to that of a short column. 在同等条件下，即截面相同，在同等条件下，即截面相同，配筋相同，材料相同的条件配筋相同，材料相同的条件下，长柱下，长柱承载力承载力低于短柱承低于短柱承载力载力Classification of ColumnsnBased on late
7、ral reinforcementnColumns reinforced with longitudinal bars and lateral ties.普通箍筋柱纵筋箍筋：侧向约束纵筋、抗剪bhClassification of ColumnsnBased on lateral reinforcementnColumns reinforced with longitudinal bars and continuous spirals.螺旋箍筋柱螺旋箍筋柱Classification of ColumnsnBased on lateral reinforcementnComposite com
8、pression members组合柱组合柱 nreinforced longitudinally withn structural steel shapes 型钢型钢nstructural steel pipe 钢管钢管nstructural steel tubing 5tju:biN5tju:biN管形材料管形材料nwith or without additional longitudinal barsn with various types of lateral reinforcementReinforcement in columns 配筋形式配筋形式nThe main reinfor
9、cement in columns is longitudinal, parallel to the direction of the loadnLateral reinforcement ： arranged in a square, rectangular, or circular pattern. 纵筋箍筋：侧向约束纵筋、抗剪内折角处！bhReinforcement in columns 配筋形式配筋形式nLateral reinforcementn Ties nindividual relatively widely spaced nSpiralsncontinuous closely
10、 spacednFunctions of lateral reinforcementnhold the longitudinal bars in positionsnprevent longitudinal bars from bucklingnLateral reinforcement, in the form of individual relatively widely spaced ties or a continuous closely spaced spirals, serves several functions. max.80mm Min. 80mm tiestiesspira
11、lspiralnFor one, such reinforcement is needed to hold the longitudinal bars in positions in the forms while the concrete is being placed.n For this purpose, longitudinal and transverse steel are wired together to form cages, which are then moved into the forms and properly positioned before placing
12、the concrete. 钢筋骨架nFor another, transverse reinforcement is needed to prevent the highly stressed, slender longitudinal bars from buckling outward by bursting the thin concrete cover.4.2.2 Short ColumnsnBehavior of Axially Loaded Short Column When an axial load is applied to a reinforced concrete sh
13、ort column, the concrete can be considered to behave elastically up to a low stress of about 1/3 fc 当轴向应力小于当轴向应力小于1/3 fc时，短柱的压缩变形主要为弹性变形。时，短柱的压缩变形主要为弹性变形。nTwo different types of failure occur in columns, depending on whether ties or spirals are used. ntied column fails suddenly at the load Nanspiral
14、ly reinforced column continues to deflect nA tied column nfails at the load Na n concrete fails by crushing or shearing outward along inclined planes混凝土被压碎崩裂混凝土被压碎崩裂n longitudinal steel bars fail by buckling outward between ties箍筋之间的纵向钢筋压屈而向外凸出箍筋之间的纵向钢筋压屈而向外凸出shearing outward along inclined planesns
15、pirally reinforced columnnwhen the same load Na is reached, nlongitudinal steel and the concrete within the core are prevented from moving outward by the spiral. nThe concrete in the outer shell spalls off nconfining action of the spiral starts to take effect nif sizable spiral steel is provided, th
16、e load will ultimately fail the column by causing the spiral steel to yield. nSpirally reinforced columnnThe axial strain when the column fails can be much larger than that at which the shell spalls off.The ultimate bearing capacity of a short column reinforced with longitudinal bars and lateral tie
17、s nIf the load on the column is increased to reach its ultimate strength,nconcrete will reach the maximum strength n steel will reach its yield strengthDetailing Requirements for ReinforcementnMaterial Strength ：nConcrete strength has a pronounced effect on the strength capacity of a column. The hig
18、h strength concrete C30-C40 or higher grade are generally used.n受压构件的承载力主要取决于混凝土强度，一般应采用强度等级较高的混凝土。目前我国一般结构中柱的混凝土强度等级常用C30C40。nReinforcements of grade HRB335 or HRB 400 are used, and the high strength bars are not recommended.n钢筋：通常采用级和级钢筋，不宜过高。nDetailing of Column Longitudinal ReinforcementnThe rat
19、io of longitudinal steel area to gross concrete cross-section area is in the range from 0.6 percent to 5 percent. nThe lower ratio limit is necessary to ensure resistance to bending moment not accounted in the analysis and to reduce the effects of creep and shrinkage of the concrete under sustained
20、compression. n考虑到实际结构中存在偶然附加弯矩的作用（垂直于弯矩作用平面），以及收缩和温度变化产生的拉应力，规定了受压钢筋的最小配筋率nDetailing of Column Longitudinal ReinforcementnRatios higher than 5 percent not only are uneconomical, but also would cause difficulty owing to congestion of the reinforcement, particularly where the steel must be spliced. n考
21、虑到施工布筋不致过多影响混凝土的浇筑质量，全部纵筋配筋率不宜超过5%。nMost columns are designed with ratios below 2 percent. nDetailing of Column Longitudinal ReinforcementnLarger diameter bars are used to reduce placement costs and to avoid unnecessary congestion.一一般般宜宜采采用用根根数数较较少少，直直径径较较粗粗的的钢筋，以保证骨架的刚度。钢筋，以保证骨架的刚度。n The diameter o
22、f the longitudinal reinforcement should not be less than 12mm.纵纵向向受受力力钢钢筋筋的的直径不宜小于直径不宜小于12mmnA minimum of four longitudinal bars is required when the bars are enclosed by spaced rectangular or circular ties.n柱中纵向受力钢筋不少于根柱中纵向受力钢筋不少于根nDetailing of Column Longitudinal ReinforcementnSpacing between long
23、itudinal bars measured along the periphery pE5rifEripE5rifEri should not exceed 300mm.n侧面上的纵向受力钢筋中距不宜大于侧面上的纵向受力钢筋中距不宜大于300mmnWhen the depth of the eccentrically loaded column is greater than 600mm, additional longitudinal bars with a diameter of 10-16mm should be placed on the lateral sides.n当偏心受压柱的
24、截面高当偏心受压柱的截面高度度h600mm时，在柱的时，在柱的侧面上应设置直径为侧面上应设置直径为10-16mm的纵向构造钢筋的纵向构造钢筋nDetailing of Column Longitudinal ReinforcementnLongitudinal bars in a column are generally spliced at mid-storey height, away from the section of maximum stress.nWhere the column cross-section dimensions change, longitudinal bars
25、 need to be offset. The slope of the offset bar should not exceed 1 in 6. Horizontal ties are needed within the offset with a spacing not to exceed 10 times the minimum diameter of longitudinal bars or 200 mm, whichever is less. Detailing of Column Ties or HoopsnTo prevent buckling of longitudinal b
26、ars, all bars of tied columns shall be enclosed by lateral ties.n受压构件中的周边箍筋应做成封闭式受压构件中的周边箍筋应做成封闭式。nThe ties must be at least 1/4 of the maximum longitudinal bar diameter and at least 6mm. n箍筋直径不应小于箍筋直径不应小于d/4（d为纵向钢筋的最大直为纵向钢筋的最大直径），且不应小于径），且不应小于6mm。 Detailing of Column Ties or HoopsnThe vertical spac
27、ing of ties in columns should not exceed 15 times the minimum diameter of longitudinal bars , 400mm, or the smallest dimension of the column size, whichever is the least.n箍筋间距不应大于箍筋间距不应大于400mm及构件截面的短边尺及构件截面的短边尺寸，且不应大于寸，且不应大于15d（d为纵向受力钢筋的最小为纵向受力钢筋的最小直径）。直径）。 Detailing of Column Ties or HoopsnWhen the
28、 overall reinforcement ratio is greater than 0.03, hoops should be used with a spacing not to exceed 10 times the minimum diameter of longitudinal bars, but not larger than 200mm. The minimum hoop diameter is specified to be 8 mm.n当当柱柱中中全全部部纵纵向向受受力力钢钢筋筋的的配配筋筋率率大大于于3%时时，箍箍筋筋直直径径不不应应小小于于8mm，间间距距不不应应大大
29、于于纵纵向向受受力钢筋最小直径的力钢筋最小直径的10倍，且不应大于倍，且不应大于200mm； Detailing of Column Ties or HoopsnThe ties shall be so arranged that every corner and alternate longitudinal bar shall have lateral support provided by the corner of a tie having an included angle of not more than 135 degree , and no longitudinal bar sh
30、all be farther than 300mm on either side from such a laterally supported bar.Detailing of Column Ties or HoopsnIn members with large axial forces and small moment, longitudinal bars are spaced more or less uniformly around the perimeter. nWhen bending moments are larger, much of the longitudinal ste
31、el is concentrated at the faces of highest compression or tension, i.e., at maximum distance from the axis of bending. highest compression or tensionDetailing of Column SpiralsnSpiral columns require a minimum of six longitudinal bars. Spacers should be used to maintain the design spiral spacing and
32、 to prevent distortions.n The clear spacing between turns of the spiral must not exceed 80mm or 1/5 of its core diameter ，whichever is less. n箍筋为螺旋环或焊接圆环，间距不应大于箍筋为螺旋环或焊接圆环，间距不应大于80mm及及0.2dcor（dcor为构件核心直径，即螺旋箍筋内皮直径），为构件核心直径，即螺旋箍筋内皮直径），且不宜小于且不宜小于40mm。Detailing of Column SpiralsnSpirals should be ancho
33、red at each column end by providing an extra one and one-half turns of spiral bar. nSpirals may be spliced by full mechanical or welded splices or by lap splices with adequate lap lengths. nWhile spirals are not required to run through the column-to-floor connection zones, ties should be inserted in
34、 those zones to maintain proper confinement, especially if horizontal beams do not frame into these zones.Detailing of Column SpiralsnIn addition, a minimum ratio of spiral steel is imposed such that the structural performance of the column is significantly improved, with respect to both ultimate load and the type of failure, compared with an otherwise identical tied column.
