Mid-span section:
NPI?(?con??lI)Ap?(1395?76.68?92.82?27.76)?2520?3216.28(KN)
?pc,l/22?(t,90)MMNPINPIep?(?)?G1?u?G2?7.67MPa AnInWnp?(tu,20)WOP
l/4 section:
NPI?(1395?76.68?58.38?27.76)?2520?3105.09KN
?pc,l/4?4.76MPa
?pc?(7.67?4.76)/2?6.22MPa
??ApA?0.00424
?EP?5.065
?ps?1?e2psi2?1?e2psI0/A0
Take mid-span and l/4 cross section’s average value to calculate,
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so we have
Mid-span section: eps?ep?1141.1mm L/4 section:
eps?ep?1046.2mm
eps?(1135.52?1000.91)/2?1098.7mm;
A20?887723mm
I0?323.488?109mm4
?ps1?1063.72?320.212?109/892.119?103?4.01
?l6?76.87mpa
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Summarize table about each sections’ stresses losses and effective pre-stress
各截面钢束预应力损失平均值及有效预应力汇总表 跨中截面 L/4截面 变化点截面 支点截面 预应力阶段σlⅠ=σl1+σl2+σl4 σl1 90.797158 80.890958 25.396677 0.505211 σl2 0.00 31.646 91.36 140.84 σl4 27.54522635 27.54522635 27.54522635 27.54522635 σlⅠ 118.34 140.08 144.3 168.89 使用阶段σlⅡ=σl5+σl6 σl5 30.77813486 30.77813486 30.77813486 30.77813486 σl6 76.873 76.873 76.873 76.873 σlⅡ 107.6507 107.6507 107.6507 107.6507 钢束有效预应力 预加力阶段 使用阶段 1276.6576 1169 1254.9174 1250.6985 1226.1076 1147.3 1143 1118.5
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9.Stress check
1)Short-term normal stress check
(1)Concrete grade is C45 at cast, transport and set-up stage. Carrying prestress and self-weight, the normal stress of edge section concrete should fit:
t?cc?0.70 f’ck
(2)The normal stress of half-span section on short-term condition
upper edge:
t?ct?NpIAn?NpIepnWnu??MG1Wnu
?MG1Wnbbottom edge:
??tccNpIAnNpIenWnb
NPI??PI?AP?3216.58?103N
Take the first stage as its section features:
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t?ct?0.92MPa (C) t?cc?12.61MPa(C)
?0.7ftk'(?0.7?29.6?20.72MPa)
2）long-term normal stress check
（1）stress check of pre-stress reinforcement in long term the steel cable stress is:
???PII??EP?kt?0.021MPa?0.5fck(?0.65?32.4?16.2MPa)
（2）concrete primary stress check in long term Take II--II section as an example: : calculation of area moment:
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