钢结构桥梁的优势与特点还是非常的突出，外形轻盈美观，施工进度快，不开裂，对既有交通影响小等等
国外桥梁建设尤其是城市桥梁中钢结构采用的比例较高，为什么国内桥梁建设中采用得较少呢，这是个问题
6 h8 W) j& f) _, @( g有奖调查吧，选择或补充您认为可能的原因（可选两项）
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新的桥梁钢结构设计规范不知道什么时候能出来，公路规范一向难产，工民建和铁路钢结构设计规范早就换新了。

大跨度斜拉桥、悬索桥肯定是选钢结构咯，但是常用的中小桥钢结构不多，除了成本问题，应该中国的国情有关，或者说国外对桥梁更严格、细致：比如在国内混凝土桥的确存在很多问题，大家都晓得，但是目前就没有人会去理会，国外就不一样了，肯定要管，于是重心就转到钢结构了。

针对结构吧  不是所有的结构都是适合用钢结构的，有经济的原因  确实行政干预比较多，领导说不通过，讲再多也是白搭

大跨桥梁由于日常管理 养护，对钢材本身也是有要求的吧?而且我们国家的钢材好像没有跟国际接轨。

Cannot input Chinese, but still want to share my two cents about the steel/concrete bridge experience in the USA.
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The original post's description more likely refers to flyover or highway interchange. State DOT usually makes the decision to use whether steel or concrete alternative based on the BDR done by consulting firms. Two major factors will determine the type of the bridge to be constructed. The first one is direct construction cost, i.e., how much the tax payers will pay contractors to get the bridge built. The second one is Maintenance of Traffic (MOT), i.e., trying to have less impact on the existing traffic while building the bridge. Obviously, there might be considerable difference in those two aspects case by case. Usually, steel bridge has higher one-time cost than concrete one, but might have less impact in MOT. Thus, a steel alternative is quite often chosen by many State DOT, who have good experience in steel bridges. However, there seems to be a trend that more concrete bridges are chosen to be built in the USA.
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xiaoben2010 发表于 2011-6-19 13:29

                               
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" h+ ~9 ~9 y) R! KCannot input Chinese, but still want to share my two cents about the steel/concrete bridge experienc ...

# N5 l, K# y6 H. E9 p简单的翻译了一下：
6 R* b  A  o* z$ [不能输入汉字，但还是可以分享我的两个关于在美国钢/混凝土桥梁的经验。
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原帖（楼主帖？）的描述可能指的是指天桥或高速公路交汇处的桥梁。在美国，国家交通部通常作出是否使用钢或混凝土结构决定，决策依据来源于是咨询公司所做的BDR。两大因素将决定要建造的桥型。第一种是直接建造成本，即多少纳税人将支付承包商获得的桥梁建成。第二个是保通问题（MOT），即在建桥的同时减少对现有交通的影响。很明显，有可能在这两个方面各个案例相当大的差异。通常情况下，钢桥比混凝土桥可能会高于一个具体的时间成本，但可能减少影响交通的程度。因此，对于那些有着丰富经验的国家来说，钢桥就是一个很好的选择。然而，美国也似乎有越来越倾向于建造混凝土桥的趋势。

翻译有误啊，不能输入汉字。。。咋变不能引入中国了。。。

会做钢结构的人不多，而且维护费用高，除非跨境需要，一般都不会首选钢结构的

主要是太耗钱

个人认为主要是工程造价较高，另外施工工艺要求也较高，目前我国大多施工队伍的水平达不到要求。

维护费用高,另外施工工艺要求也较高，

Just a clarification of a couple of things:
(1) state DOT refers to "州交通部", not the US federal DOT. Many state DOT have created their own bridge design guidelines, which may override the AASHTO design codes in many aspects. Owners of bridges usually have the power to choose what code to be used in bridge design.
) H* W8 Y% E' B) h9 |0 H# x(2) BDR is for Bridge Development Report, which aims to select the most cost efficient bridge to fit the unique circumstances at the site.

1 z' d% k: v/ i7 h4 p! ^2 }It's true that steel bridge usually is more expensive than concrete one. The major reason is that steel bridge fabrication needs more labor, and labor is quite expensive in the States. That's why some contractor in CA started to get steel bridge members made in China recently. Besides, the standard for welding of steel members is very strict and high. Tension or stress reverse zone in fracture critical members needs to subject to Charpy V-Notch test and well documented. Nevertheless, steel plate or box girder bridges are still being chosen by many DOT case by case when the overall benefits are considered.

翻译下：
对楼上的翻译,澄清下2个问题
" w& M3 F. S: Y' k* n% l. s1）州交通部不是米国国家交通部，许多州都有自己的桥梁设计规范，很多方面和ASSHTO规范的规定时不一致的。业主可以自己选择用什么规范。
4 k/ p* Q0 G; [2 o5 F4 i0 n2）BDR是类似于我们国内的工可，用于选择最适合现场环境的最合适的桥梁。
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* L' Z9 z1 @! }, q诚然，钢桥比混凝土桥造价昂贵，但主要原因是钢桥的加工需要更多的劳动力，在美国劳动力成本是相当昂贵的。所以CA（加拿大？)很多承包商从中国进口钢桥的构件。另外，钢构件的焊接标准很高很严格，既受拉又受压的区域需要进行严重受损部件V口冲击试验（这个不一定准）并且有完整的证明。不过，钢板梁或钢箱梁桥在具体分析全面利益的情况下仍然被许多州交通部选择使用。

个人认为首先是具备丰富设计、施工、养护管理经验的公司、技术骨干、施工队伍较少，之前我们国家缺钢材、钢材质量不高，造成了近2、3十年修建的钢桥较少，积累的经验也较少，国家基础设施建设的发展速度相当快，钢材供应受到国外铁矿石垄断企业的定价机制制约。再者，我国钢材冶炼水平和发达国家还有相当的差距。以上原因是造成现状的主要因素。