输入边界条件
边界条件的输入方法如下。 Element Number (off) ; Model / Boundary / Supports
Select Single (Nodes : 1) Boundary Group Name>B-G1 Options>Add
Support Type> Dy, Dz, Rx (on) ? Select Single (Nodes : 16) Boundary Group Name>B-G1 Options>Add
Support Type>Dx, Dy, Dz, Rx (on) ? Select Single (Nodes : 31) Boundary Group Name>B-G2 Options>Add
Support Type> Dy, Dz, Rx (on) ?
图13. 定义边界条件 Node Number (on)
16
输入荷载
本例题针对恒荷载和预应力荷载进行施工阶段分析。移动荷载分析则需另行输入移动荷载数据。 Load / Static Load Cases
Name (恒荷载)
Type (Construction Stage Load) ? Name (Prestress 1)
Type (Construction Stage Load) ? Name (Prestress 2)
Type (Construction Stage Load) ?
图14. 输入静力荷载工况的对话框
17
输入恒荷载
使用 自重 功能输入恒荷载。 Load / Self Weight
Load Case Name > 恒荷载 Load Group Name > Selfweight Self Weight Factor > Z (-1)
图15. 输入恒荷载
18
当钢束施加张拉力，维持其一定的应变时，作用到钢束上的张拉应力随时间的推移逐渐减小，这个现象称之为松弛(Relaxation)。MIDAS/Civil采用Magura公式来考虑钢束的松弛。松弛系数为该式中与钢材有关的常数，一般钢材取值为10，低松弛钢材取值45。详见用户手册Analysis for Civil Structures的“预应力损失”。
输入钢束特性值
Load/ Prestress Loads / Tendon Property
Tendon Name ( Tendon ) ; Tendon Type>Internal Material>2: Tendon Total Tendon Area (0.0042997)
or
Tendon Area>15.2mm(0.6＂) Number of Tendon Area ( 31 ) ?
Duct Diameter (0.133) ; Relaxation Coefficient (45)?
Curvature Friction Factor (0.3) ; Wobble Friction Factor (0.0066)
Ultimate Strength (190000) ; Yield Strength (160000) Load Type>Post-Tension
Anchorage Slip>Begin (0.006) ; End (0.006) ?
图16. 输入钢束特性值
19
?
钩选固定(fix)的话该点的斜率为所输入的值，若不选则生成拥有适当斜率的曲线。
输入钢束形状
首先输入第一跨的钢束形状。
Hidden(on) ;
Element Number (on) ;
Node Number (off)
Model / Loads / Prestress Loads / Tendon Profile
Tendon Name (Tendon 1) ; Tendon Property>Tendon Select Window (Elements : 1 to 18) Straight Length of Tendon>Begin (0) ; End (0) Profile
1>x ( 0 ), y ( 0 ), z ( 1.5 ), fix (off)?
2>x ( 12 ), y ( 0 ), z ( 0.2 ), fix (on), Ry ( 0 ), Rz ( 0 ) 3>x ( 30 ), y ( 0 ), z ( 2.6 ), fix (on) , Ry ( 0 ), Rz ( 0 ) 4>x ( 36 ), y ( 0 ), z ( 1.8 ), fix (off) Tendon Shape>Straight Profile Insertion Point ( 0, 0, 0)
?
X Axis Direction>X ?
图17. 定义钢束形状 20
?