筒体结构在水平力作用下,框筒中除了腹板框架抵抗部分倾覆力矩外,翼缘框架柱承受拉、压力,可以抵抗水平荷载产生的部分倾覆力矩。框筒结构具有很大的抗侧移和抗扭刚度,又可增大内部空间的使用灵活性,对于高层建筑,框筒、筒中筒、束筒都是高效的抗侧力结构体系框筒也可着成在实腹筒上开了很多小孔洞,但它的受力比一个实腹筒要复杂得多。
剪力滞后现象使翼缘框架各柱受力不均匀,中部柱子的轴向应力减少,角柱轴向应力增大,见图8-1,腹板框架各柱抽力也不是直线分布(剪力滞后造成的)。
腹板框架在水平力作用下一端受拉,另一端受压,角柱受力最大。翼缘框架受力是通过与腹板框架相交的角柱传递过来的,图8-2是翼缘框架变形示意,角柱受压力缩短,使与它相邻的裙梁承受剪力(受弯),因此相邻柱承受轴压;第二个柱子受压又使第二跨裙梁受剪(受弯),相邻柱又承受轴压,如此传递,使翼缘框架的裙梁和柱都承受其平面内的弯矩、剪力与轴力(与水平力作用方向相垂直)。由于梁的变形,使翼缘框架各柱压缩变形向中心逐渐递减,轴力也逐渐减小,这就是剪力滞后现象;同理,受拉的翼缘框架也产生轴向拉力的剪力滞后现象。腹板框架的柱轴力也呈曲线分布,角柱轴力大,中部柱子轴力较小(与直线分布相比),腹板框架剪力滞后现象也是由于裙梁的变形造成的,使角柱的轴力加大。
影响剪力滞后的因素很多,影响较大的有:①柱距与裙梁高度。②角柱面积。③框筒结构高度。④框筒平面形状。 实际上,影响剪力滞后大小的主要因素是裙梁剪切刚度与柱轴向刚度的比值,要求形成密柱(小柱距),实际是减小裙梁的跨度,减小裙梁跨度或加大其截面高度,都能增大裙梁的剪切刚度。梁的剪切刚度愈大,剪力滞后愈小。
模型采用两榀两层框架模型,其中左侧模型两层框架梁均采用抗弯无限刚模拟。右侧模型顶层框架梁采用抗弯无限刚模拟,一层框架梁采用实际截面实际刚度模拟。顶部两端点均施加1000kn水平推力。其余模型参数均一致。
柱轴力分布图
(1)蓝色实线为一层、二层均采用抗弯无限刚模拟的柱轴力分布结果,可以看出其分布呈明显的直线分布,与我们常规的桩基验算公式一致(都是假定承台或顶部盖梁抗弯无限刚,可以协调柱变形保证为平截面假定)
(2)红色虚线为一层采用实际梁抗弯刚度的柱轴力分布结果,可以看出其分布呈明显的曲线分布,边部柱轴力明显比蓝色曲线大很多,且中间柱轴力小于蓝色曲线,与平截面假定分布相差较大。这就是明显的剪力滞后效应。
(3)从下面的变形图也可以佐证以上观点。当然,本次模拟仅分析了梁刚度对剪力滞后的影响,其余角柱截面尺寸、柱间距等因素均未考虑,仅为说明剪力滞后的概念及原理。
Z向变形图(一层楼无限抗弯刚度)
Z向变形(一层楼实际抗弯)
一个是柔性变形,水变形存在剪力滞后,鸭子扒水效率不高。一个是刚性变形,刨土效率高。
*VERSION
9.1.0
*UNIT ; Unit System
; FORCE, LENGTH, HEAT, TEMPER
KN , M, KJ, C
*STRUCTYPE ; Structure Type
; iSTYP, iMASS, iSMAS, bMASSOFFSET, bSELFWEIGHT, GRAV, TEMPER, bALIGNBEAM, bALIGNSLAB, bROTRIGID
0, 1, 1, NO, NO, 9.806, 0, NO, NO, NO
*REBAR-MATL-CODE ; Rebar Material Code
; CONC_CODE, CONC_MDB, SRC_CODE, SRC_MDB
GB10(RC), HRB400, GB10(RC), HRB400
*NODE ; Nodes
; iNO, X, Y, Z
1, 0, 0, 0
2, 5, 0, 0
5, 10, 0, 0
7, 15, 0, 0
9, 20, 0, 0
11, 25, 0, 0
13, 0, 4, 0
15, 5, 4, 0
17, 10, 4, 0
19, 15, 4, 0
21, 20, 4, 0
23, 25, 4, 0
25, 0, 0, 6
26, 5, 0, 6
27, 10, 0, 6
28, 15, 0, 6
29, 20, 0, 6
30, 25, 0, 6
31, 0, 4, 6
32, 5, 4, 6
33, 10, 4, 6
34, 15, 4, 6
35, 20, 4, 6
36, 25, 4, 6
37, 2.5, 0, 0
39, 12.5, 0, 0
41, 22.5, 0, 0
43, 2.5, 4, 0
45, 12.5, 4, 0
47, 22.5, 4, 0
49, 2.5, 0, 6
50, 12.5, 0, 6
51, 22.5, 0, 6
52, 2.5, 4, 6
53, 12.5, 4, 6
54, 22.5, 4, 6
55, 7.5, 0, 0
57, 17.5, 0, 0
59, 7.5, 4, 0
61, 17.5, 4, 0
63, 7.5, 0, 6
64, 17.5, 0, 6
65, 7.5, 4, 6
66, 17.5, 4, 6
1000, 0, 4, -6
1001, 2.5, 4, -6
1002, 5, 4, -6
1003, 7.5, 4, -6
1004, 10, 4, -6
1005, 12.5, 4, -6
1006, 15, 4, -6
1007, 17.5, 4, -6
1008, 20, 4, -6
1009, 22.5, 4, -6
1010, 25, 4, -6
2000, 0, 0, -6
2001, 2.5, 0, -6
2002, 5, 0, -6
2003, 7.5, 0, -6
2004, 10, 0, -6
2005, 12.5, 0, -6
2006, 15, 0, -6
2007, 17.5, 0, -6
2008, 20, 0, -6
2009, 22.5, 0, -6
2010, 25, 0, -6
*ELEMENT ; Elements
1, BEAM , 1, 1, 1, 2000, 0, 0
2, BEAM , 1, 1, 2, 2002, 0, 0
3, BEAM , 1, 1, 5, 2004, 0, 0
4, BEAM , 1, 1, 7, 2006, 0, 0
5, BEAM , 1, 1, 9, 2008, 0, 0
6, BEAM , 1, 1, 11, 2010, 0, 0
7, BEAM , 1, 2, 1, 37, 0, 0
8, BEAM , 1, 2, 2, 55, 0, 0
9, BEAM , 1, 2, 5, 39, 0, 0
10, BEAM , 1, 2, 7, 57, 0, 0
11, BEAM , 1, 2, 9, 41, 0, 0
12, BEAM , 1, 1, 13, 1000, 0, 0
13, BEAM , 1, 1, 15, 1002, 0, 0
14, BEAM , 1, 1, 17, 1004, 0, 0
15, BEAM , 1, 1, 19, 1006, 0, 0
16, BEAM , 1, 1, 21, 1008, 0, 0
17, BEAM , 1, 1, 23, 1010, 0, 0
18, BEAM , 1, 3, 13, 43, 0, 0
19, BEAM , 1, 3, 15, 59, 0, 0
20, BEAM , 1, 3, 17, 45, 0, 0
21, BEAM , 1, 3, 19, 61, 0, 0
22, BEAM , 1, 3, 21, 47, 0, 0
23, BEAM , 1, 1, 25, 1, 0, 0
24, BEAM , 1, 1, 26, 2, 0, 0
25, BEAM , 1, 1, 27, 5, 0, 0
26, BEAM , 1, 1, 28, 7, 0, 0
27, BEAM , 1, 1, 29, 9, 0, 0
28, BEAM , 1, 1, 30, 11, 0, 0
29, BEAM , 1, 3, 25, 49, 0, 0
30, BEAM , 1, 3, 26, 63, 0, 0
31, BEAM , 1, 3, 27, 50, 0, 0
32, BEAM , 1, 3, 28, 64, 0, 0
33, BEAM , 1, 3, 29, 51, 0, 0
34, BEAM , 1, 1, 31, 13, 0, 0
35, BEAM , 1, 1, 32, 15, 0, 0
36, BEAM , 1, 1, 33, 17, 0, 0
37, BEAM , 1, 1, 34, 19, 0, 0
38, BEAM , 1, 1, 35, 21, 0, 0
39, BEAM , 1, 1, 36, 23, 0, 0
40, BEAM , 1, 3, 31, 52, 0, 0
41, BEAM , 1, 3, 32, 65, 0, 0
42, BEAM , 1, 3, 33, 53, 0, 0
43, BEAM , 1, 3, 34, 66, 0, 0
44, BEAM , 1, 3, 35, 54, 0, 0
45, BEAM , 1, 1, 37, 2001, 0, 0
46, BEAM , 1, 1, 39, 2005, 0, 0
47, BEAM , 1, 1, 41, 2009, 0, 0
48, BEAM , 1, 1, 43, 1001, 0, 0
49, BEAM , 1, 1, 45, 1005, 0, 0
50, BEAM , 1, 1, 47, 1009, 0, 0
51, BEAM , 1, 1, 49, 37, 0, 0
52, BEAM , 1, 1, 50, 39, 0, 0
53, BEAM , 1, 1, 51, 41, 0, 0
54, BEAM , 1, 1, 52, 43, 0, 0
55, BEAM , 1, 1, 53, 45, 0, 0
56, BEAM , 1, 1, 54, 47, 0, 0
57, BEAM , 1, 1, 55, 2003, 0, 0
58, BEAM , 1, 1, 57, 2007, 0, 0
59, BEAM , 1, 1, 59, 1003, 0, 0
60, BEAM , 1, 1, 61, 1007, 0, 0
61, BEAM , 1, 1, 63, 55, 0, 0
62, BEAM , 1, 1, 64, 57, 0, 0
63, BEAM , 1, 1, 65, 59, 0, 0
64, BEAM , 1, 1, 66, 61, 0, 0
65, BEAM , 1, 2, 37, 2, 0, 0
66, BEAM , 1, 2, 55, 5, 0, 0
67, BEAM , 1, 2, 39, 7, 0, 0
68, BEAM , 1, 2, 57, 9, 0, 0
69, BEAM , 1, 2, 41, 11, 0, 0
70, BEAM , 1, 3, 43, 15, 0, 0
71, BEAM , 1, 3, 59, 17, 0, 0
72, BEAM , 1, 3, 45, 19, 0, 0
73, BEAM , 1, 3, 61, 21, 0, 0
74, BEAM , 1, 3, 47, 23, 0, 0
75, BEAM , 1, 3, 49, 26, 0, 0
76, BEAM , 1, 3, 63, 27, 0, 0
77, BEAM , 1, 3, 50, 28, 0, 0
78, BEAM , 1, 3, 64, 29, 0, 0
79, BEAM , 1, 3, 51, 30, 0, 0
80, BEAM , 1, 3, 52, 32, 0, 0
81, BEAM , 1, 3, 65, 33, 0, 0
82, BEAM , 1, 3, 53, 34, 0, 0
83, BEAM , 1, 3, 66, 35, 0, 0
84, BEAM , 1, 3, 54, 36, 0, 0
*MATERIAL ; Material
1, CONC , C60 , 0, 0, , C, NO, 0.05, 1, GB10(RC) , , C60 , NO, 3.5992e+07
*SECTION ; Section
1, DBUSER , 900*900 , CC, 0, 0, 0, 0, 0, 0, NO, NO, SB , 2, 0.9, 0.9, 0, 0, 0, 0, 0, 0, 0, 0
2, DBUSER , 600*1800 , CC, 0, 0, 0, 0, 0, 0, NO, NO, SB , 2, 1.8, 0.6, 0, 0, 0, 0, 0, 0, 0, 0
3, DBUSER , 600*1801 , CC, 0, 0, 0, 0, 0, 0, NO, NO, SB , 2, 1.801, 0.6, 0, 0, 0, 0, 0, 0, 0, 0
*SECT-SCALE ; Section Stiffness Scale Factor
; iSEC, AREA_SF, ASY_SF, ASZ_SF, IXX_SF, IYY_SF, IZZ_SF, WGT_SF, GROUP, iPart ; line 1
3, 1, 1, 1, 1, 1e+08, 1e+08, 1, , 1
*DGN-SECT
1, DBUSER , 900*900 , CC, 0, 0, 0, 0, 0, 0, NO, NO, SB , 2, 0.9, 0.9, 0, 0, 0, 0, 0, 0, 0, 0
2, DBUSER , 600*1800 , CC, 0, 0, 0, 0, 0, 0, NO, NO, SB , 2, 1.8, 0.6, 0, 0, 0, 0, 0, 0, 0, 0
3, DBUSER , 600*1801 , CC, 0, 0, 0, 0, 0, 0, NO, NO, SB , 2, 1.801, 0.6, 0, 0, 0, 0, 0, 0, 0, 0
*STLDCASE ; Static Load Cases
; LCNAME, LCTYPE, DESC
L , L ,
*DGN-CTRL ; General Design Data
; bFRAMEX, bFRAMEY, bAUTOKF, LC1, LC2, LC3, LC4, LC5, RT, DT, bAF, bMO, bSF, iSTRUCTMATL, iSTRUCT, b02Q0UpLimit, 02Q0UpLimit ; 1st line
; STORY1, XMIN1, XMAX1, YMIN1, YMAX1, RMIN1, RMAX1 ; 2nd line
; ... ; ...
; STORYn, XMINn, XMAXn, YMINn, YMAXn, RMINn, RMAXn ; n+1th line
NO, NO, NO, , , , , , 1, 3D, YES, NO, NO, 0, 1, NO, 2
*CONSTRAINT ; Supports
; NODE_LIST, CONST(Dx,Dy,Dz,Rx,Ry,Rz), GROUP
1000to1010 2000to2010, 111111,
*MEMBERTYPE ; Modify Member Type
; ELEM_LIST, TYPE, SUBTYPE
1to6 12to17 23to28 34to39 45to64, COLUMN, 1
*USE-STLD, L
*CONLOAD ; Nodal Loads
; NODE_LIST, FX, FY, FZ, MX, MY, MZ, GROUP,STRTYPENAME
25, 1000, 0, 0, 0, 0, 0, ,
30, 1000, 0, 0, 0, 0, 0, ,
31, 1000, 0, 0, 0, 0, 0, ,
36, 1000, 0, 0, 0, 0, 0, ,
; End of data for load case [L] -------------------------
*LOADCOMB ; Combinations
; NAME=NAME, KIND, ACTIVE, bES, iTYPE, DESC, iSERV-TYPE, nLCOMTYPE, nSEISTYPE ; line 1
; ANAL1, LCNAME1, FACT1, ... ; from line 2
NAME=1, CONC, STRENGTH, 0, 0, , 0, 0, 0
ST, L, 1
*LC-COLOR ; Diagram Color for Load Case
1, CONC , C60 , 1, GB10(RC) , ,C60 , NO, 1, NO, 0, GB(RC), HRB400, HRB400, , , 42000, NO, 0, 0, , , , 0, NO, 1, , , , 0, 0, 0
*ENDDATA
知识点:筒体剪力滞后模拟与分析
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