中午刚刚打了电话, 被告知PD current和case out of processing time are not the reasons to ask for the Service Request. 大家用的什么理由啊? 真倒霉. 可能碰上 了不nice的人. 说话特快还有口音, 说了一大堆没用的费话. 最后告诉我不行.
【在 a****r 的大作中提到】 : 纯粹技术讨论:如果deflection too large to meet code limit, what can you do : without increase section? : : ★ 发自iPhone App: ChineseWeb 8.1
m*t
29 楼
I was able to and just did. You may wanna try it again.
the
【在 f********f 的大作中提到】 : 中午刚刚打了电话, 被告知PD current和case out of processing time are not the : reasons to ask for the Service Request. 大家用的什么理由啊? 真倒霉. 可能碰上 : 了不nice的人. 说话特快还有口音, 说了一大堆没用的费话. 最后告诉我不行.
b*g
30 楼
Deflection of what? Concrete beam? How about doublely reinfoced section? or prestressed/posttensioned?
【在 a****r 的大作中提到】 : 纯粹技术讨论:如果deflection too large to meet code limit, what can you do : without increase section? : : ★ 发自iPhone App: ChineseWeb 8.1
j*l
31 楼
TSC, very promising, I think you will get it very soon! Best luck!
【在 a****r 的大作中提到】 : 已经是post-tension flat plate, because span to thickness ratio exceeds code : recommend, deflection exceeds L/240 : : ★ 发自iPhone App: ChineseWeb 8.1
a*r
40 楼
There is no min thickness requirement for PT slab. ACI exclusive chapter 13 in Prestressed design And span to thickness is on commentary in chapter 18, not in code provision
【在 a****r 的大作中提到】 : There is no min thickness requirement for PT slab. ACI exclusive chapter 13 : in Prestressed design : And span to thickness is on commentary in chapter 18, not in code provision : : ★ 发自iPhone App: ChineseWeb 8.1
a*r
42 楼
I agree.commentary is intend of code. it said span-thickness ratio should not exceed to xxx
Should not 可能不能作为mendatory 的要求,但是同时deflection也不能达到规范要 求就很能说明板厚不够的问题了。
★ 发自iPhone App: ChineseWeb 7.8
【在 a****r 的大作中提到】 : I agree.commentary is intend of code. : it said span-thickness ratio should not exceed to xxx
a*r
44 楼
Designer tried to push everything to limit. Long term deflection is a grey area.
【在 z******i 的大作中提到】 : Should not 可能不能作为mendatory 的要求,但是同时deflection也不能达到规范要 : 求就很能说明板厚不够的问题了。 : : ★ 发自iPhone App: ChineseWeb 7.8
z*i
45 楼
Whoever stamp the drawing shall make the final decision. If you gonna to stamp it, you can and you should force the designer to make the change. If you don't stamp it, document all the issues in formal documentation, sign it with the date for you own backup.
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【在 a****r 的大作中提到】 : Designer tried to push everything to limit. : Long term deflection is a grey area.
j*f
46 楼
Commentary是规范的解释,当然是规范的一部分,而且规范的要求只是设计的最低要求 ,deflection要同时满足immediate deflection and long term deflection, for long term deflection there is no "grey area', 设计的时候一定要给自己留有足够 的余地,即使deflection 满足了规范的最低要求,并不意味着设计就是安全的,我们 以前作的一个工程还在打官司。
13 provision
【在 a****r 的大作中提到】 : There is no min thickness requirement for PT slab. ACI exclusive chapter 13 : in Prestressed design : And span to thickness is on commentary in chapter 18, not in code provision : : ★ 发自iPhone App: ChineseWeb 8.1
z*i
47 楼
I looked over the code, I don't think long tem deflection is gray area. 9.5.4.3 — Additional long-term deflection of prestressed concrete members shall be computed taking into account stresses in concrete and steel under sustained load and including effects of creep and shrinkage of concrete and relaxation of steel. 9.5.4.4 — Deflection computed in accordance with 9.5.4.1 or 9.5.4.2, and 9.5.4.3 shall not exceed limits stipulated in Table 9.5(b). R18.12.3 — For prestressed flat slabs continuous over two or more spans in each direction, the span-thickness ratio generally should not exceed 42 for floors and 48 for roofs; these limits may be increased to 48 and 52, respectively, if calculations verify that both short- and long-term deflection, camber, and vibration frequency and amplitude are not objectionable. Short- and long-term deflection and camber should be computed and checked against the requirements of serviceability of the structure.
【在 a****r 的大作中提到】 : Designer tried to push everything to limit. : Long term deflection is a grey area.
比如你如何确定long term deflection factor use for computer model? Regular structure is 3, but for those structure in extreme span- thickness ratio, should I allow designer use 3? ACI 290 recommend 2-5.15
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【在 z******i 的大作中提到】 : I looked over the code, I don't think long tem deflection is gray area. : 9.5.4.3 — Additional long-term deflection of : prestressed concrete members shall be computed : taking into account stresses in concrete and steel : under sustained load and including effects of creep : and shrinkage of concrete and relaxation of steel. : 9.5.4.4 — Deflection computed in accordance with : 9.5.4.1 or 9.5.4.2, and 9.5.4.3 shall not exceed limits : stipulated in Table 9.5(b). : R18.12.3 — For prestressed flat slabs continuous over two or
【在 a****r 的大作中提到】 : 比如你如何确定long term deflection factor use for computer model? : Regular structure is 3, but for those structure in extreme span- thickness : ratio, should I allow designer use 3? ACI 290 recommend 2-5.15 : : ★ 发自iPhone App: ChineseWeb 8.1
I found this while I am reading ACI 209: Although creep and shrinkage effects may be higher in thin slabs than in beams (time-dependent deflections as large as 5 to 7 times the initial deflections have been noted,2g*3g the same approach for predicting timedependent beam deflections may, in most cases, be used with caution for flat plates and two-way slabs. These include Eqs. (3-7), (3-8), and (3-10) for the effect of compression steel, etc., and Eq. (4-3) for additional long-time deflections. The effect of cracking on the effective moment of inertia Ie, for flat plates and two-way slabs is discussed in Section 3.4 of this report. Seems like the deflection factor shall be higher than regular beam as the member gets thinner. You can recommend to use 5.0 based on the above section.
【在 a****r 的大作中提到】 : ACI 435R-95 apply to PT. It mentions deflection factor too. : : ★ 发自iPhone App: ChineseWeb 8.1
【在 z******i 的大作中提到】 : I found this while I am reading ACI 209: : Although creep and shrinkage effects may be higher in : thin slabs than in beams (time-dependent deflections as : large as 5 to 7 times the initial deflections have been : noted,2g*3g the same approach for predicting timedependent : beam deflections may, in most cases, be used : with caution for flat plates and two-way slabs. These : include Eqs. (3-7), (3-8), and (3-10) for the effect of : compression steel, etc., and Eq. (4-3) for additional : long-time deflections. The effect of cracking on the
【在 a****r 的大作中提到】 : 就是overall package很多detail很烂,会造成开裂,早期裂缝等等。that's why I : chase so hard. : Good practice not equal to code. Code never teaches us how to be a good : engineer. : : ★ 发自iPhone App: ChineseWeb 8.1
【在 j*****f 的大作中提到】 : Commentary是规范的解释,当然是规范的一部分,而且规范的要求只是设计的最低要求 : ,deflection要同时满足immediate deflection and long term deflection, for : long term deflection there is no "grey area', 设计的时候一定要给自己留有足够 : 的余地,即使deflection 满足了规范的最低要求,并不意味着设计就是安全的,我们 : 以前作的一个工程还在打官司。 : : 13 : provision
j*f
77 楼
这个一定要分情况, 有些简单的改造项目, 结构本身也比较简单,比如像沃尔玛那样 的结构 屋顶加roof top unit 一般如果柱子过荷5%以内,我都会让他过去,但是如果 是复杂的结构,或者新设计一定要满足规范要求,施工过程不是我们可以控制的,出现 的问题也是各种各样的,一但出现事故 上庭, 哪怕只有1%, 基本就输定了, 到时候 就是自己挖坑把自己埋了