4.4钢筋混土柱.ppt

4.4 Reinforced Concrete Column ;Axial Compression ; In addition to the common type of compression member, i.e. vertical elements in structures, compression members include arch ribs, rigid frame members inclined or otherwise, compression elements in trusses or shell. ;除了一般的受压构件，即结构中的竖向构件，受压构件还包括拱肋，斜的刚架构件，桁架或壳结构中的受压构件。 ;配置纵向结构型钢、钢管或管形材料并配有各种类型横向钢筋的复合受压构件，无论是否配置附加的纵向钢筋。;The main reinforcement in columns is longitudinal, parallel to the direction of the load, and consists of bars arranged in a square, rectangular, or circular pattern.;Lateral reinforcement, in the form of individual relatively widely spaced ties or a continuous closely spaced spiral, serves several functions.;for one 作为其中一个; 举例来说;For this purpose, longitudinal and transverse steel is wired together to form cages, which are then moved into the forms and properly positioned before placing the concrete. ;For another, transverse reinforcement is needed to prevent the highly stressed, slender longitudinal bars from buckling outward by bursting the thin concrete cover.;Behavior of Axially Loaded Short Column;当荷载作用在钢筋混凝土短柱形心时，应力低于;普通箍筋柱在荷载Na作用下破坏。在此荷载下，由于混凝土压碎或向外沿斜面受剪破坏，纵筋由于在箍筋之间向外弯曲而破坏，如图（4.26a）所示。 ; It is at this stage that the confining action of the spiral has a significant effect, and if sizable spiral steel is provided, the load will ultimately fail the column by causing the spiral steel to yield . ;; (a) Unsupported bars buckle (b) Concrete shell spalls off Failure of tied and spirally reinforced concrete column;Short Columns under Combined Axial Force and Moment;When a member is subjected to combined axial compression N and moment M, such as in Figure 4.28(a), it is usually convenient to replace the axial load and moment with an equal load N applied at eccentricity ;当柱子承受轴力N以及弯距M的共同作用时，如图4.28a，通常用轴力N作用在距离轴心e=M/N处取代构件承受的轴力和弯矩，如图4.28b所示，是一种很简便的方法。 ;Balanced failure;在这种破坏方式下，远离轴向力作用点一侧的受拉钢筋屈服，同时受压区混凝土达到0.0033的极限压应变。;当相对偏心距e0/h0较小时，或尽管相对偏心距e0/h0较大，但受拉钢筋配置较多时，柱子会发生受压破坏。 ;这种破坏表现为离荷载作用点近的一侧混凝土压碎钢筋受压屈