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【正文】 01395ⅡⅡ變化點(diǎn)截面鋼束編號(hào)θθμXkx1e(θμ+kx)σσl1176。radN1 N2 N3 截面跨中ⅠⅠL/4變化點(diǎn)ⅡⅡ支點(diǎn)σl1(2)Anchorage deformation、steel retraction causes stress lossesPost tensioned structure should consider the influence of friction, its influence length is :the deformation value of anchor in tensioned end, 。 the control stress in tensioned end, the prestress value of anchor end except the value of pipe friction losses, 。versus of prestressed reinforcement elastic modulus to concrete elastic modulus, calculate as the concrete true strength when tensioned, is assumed as 90% design value, , we can obtain Concrete normal stress that all prestressed reinforcements’ resultant force at its application point caused, , section features use the first stage in the upper table。Steel loose coefficient, to low relaxation strand, =。Midspan section:l/4 section: Take midspan and l/4 cross section’s average value to calculate, so we haveMidspan section: L/4 section: 。oaS39。0bS0aS0x0S0b 面積距216387428 aax0x0bb Vq=245 τ= 計(jì)算纖維面積距剪應(yīng)力τ正應(yīng)力σ主應(yīng)力正應(yīng)力 第一階段凈面積Sn第二階段凈面積S39。oaS39。0bS0aS0x0S0b 面積距203304322 aax0x0bb Vq= τ=計(jì)算纖維面積距剪應(yīng)力τ正應(yīng)力σ主應(yīng)力正應(yīng)力 第一階段凈面積Sn第二階段凈面積S39。oaS39。0bS0aS0x0S0b 面積距204657417 aax0x0bb Vq=316 τ=計(jì)算纖維面積距剪應(yīng)力τ正應(yīng)力σ主應(yīng)力正應(yīng)力 第一階段凈面積Sn第二階段凈面積S39。oaS39。o第三階段凈面積Soσtpσcpepn= σcx= aa239266511主應(yīng)力 x0x0264139987σtp σcp 由以上可知混凝土主壓應(yīng)力最大值為*fck 由以上可知混凝土主拉應(yīng)力最大值為 The limit value of concrete principal pressive stress is , from the upper table, concrete principle pressive stress all lower the limit value, so its ok!check of principle stressWe know the maximum tension stress is 10. Check of crackingcracking check of normal section in short term Check midspan cross section:calculation of concrete prepressive cracking caused by prestressMidspan cross section: We have:calculation of concrete tensile stress caused by loadWe have concrete normal stress cracking For A type concrete structure, concrete tensile stress should satisfied with the following in short term: (C)The result satisfied with the request! Ok!!!in long term: ok!!!! racking check of inclined section in short term Take changing point section as an calculation section.principle stressTake aa as an exampleShear stress:剪力SnS39。0I0ynay39。0S0剪應(yīng)力正應(yīng)力主拉應(yīng)力主壓應(yīng)力aa198372000209028000224376000x0x0205824900217848900230929600bb137432000153368000159696000(2)limit value of principle tensile stressThe concrete principle tensile stress limit value in short term:According to the upper table, we know its meet the requirements. 11. Deformation calculate1) check of main beam deflection in short termL= C50 concrete elastic modulus: Take L/4 section’s as the average value.Simply supported beam’s deflection check formula is: (1) deflection caused by variable actionDeflection coefficient of main beam midspan: , variable load value in short Term is: . So the deflection caused by variable action is:Deflection caused by variable action that considered the long term load:（2）deflection caused by the first and second stage dead load in long term2) arch value caused by prestressUse L/4 section’s torque as the average of the beam:So the arch value is:The upper arch value caused by prestress that considered long term loading is :3） layout of prearch valueThe total deflection of beam is: There is no need to layout the prearch value.12. Local pressive calculate in anchor zoneAccording to the analysis to three prestressed cables anchor point, N2 is the critical cable, the anchor and reinforcement layout in beam end of N2 are shown in the following.Some size are revised as following: d=80mm。indirect influence coefficient, k=indirect reinforcement volume ratio,So the local pression meet the requirement.
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