加拿大安大略省北部Nipigon River大桥发生断裂

       据悉，由于寒冷天气，加拿大安大略省北部新建的Nipigon River大桥发生断裂，导致连接加拿大东部和西部的唯一道路——加拿大横贯公路(Trans-Canada)交通中断。




据悉，Nipigon River大桥于2015年9月底开通，是安省第一座索拉桥，大桥的西行路段可双向行驶。目前东行路段道路仍在施工当中，预计2017年完工。


安省省警表示，大桥发生断裂是由于机械问题，因此Nipigon River大桥将会无限期地关闭。但当地媒体却表示，造成大桥断裂的原因可能是桥梁伸缩装置破损。
OPP称，当主管部门赶到现场，他们发现在桥的西侧已经伸出道路上方约60厘米。


桥面出现断裂后，警方封锁了附近11号和17号公路的交通。

17号高速公路是通过安大略省横贯加拿大的公路，连接加拿大东部和西部的唯一道路的最主要途径。它的关闭，预计会对周边社区产生重大影响。
OPP表示，大桥已经在两个方向被关闭并进入“无限期”休整。目前，尚未能确定该桥交通的恢复时间。

事故最新调查进展，有消息称：桥梁连接部的高强螺栓断裂，连接部的钢材来自中国，拉索来自西班牙。

              

是天气寒冷主梁收缩造成的，还是边跨索力过大导致主梁向上弯曲造成的？

主梁有明显的向上变形，以前是不是用的拉力支座，支座破坏导致事故的发生。

就照片分析，天气寒冷，拉索收缩，长度越长收缩量越大，产生的拉力增量越大，显然，拉力增量分布从主塔到梁端是逐渐增大的，梁端出线大的上挠分力，支座承受不住自然就断裂了。

转自微信群讨论：

       从提供的现场照片来看，估计应是设计原因导致的破坏。桥端上下游两侧翘曲高度差异还是比较大，这应属于高风速下结构颤振引起的主梁扭曲破坏（塑性变形破坏）。从提供的图片看，设计采用H型索塔+平行拉索体系+无横撑，这类索塔几乎不能给主梁提供抗扭刚度，而主梁又采用了抗扭刚度较弱的开口钢梁（图上看不太清楚，感觉应该是开口箱），两个不利结构叠加，出现颤振破坏的概率就很大了。
         1.斜拉桥、悬索桥都是竖向弯曲振型出现在前几阶振型中，扭转振型出现的要晚些，越靠前的振型越容易出现，因此（1）在低风速下容易出现涡激振动，（2）高风速下容易出现颤振。
         2.（1）涡激振不发散，一般属于竖向弹性变形范围，不会引起结构破坏，但影响行车舒适即影响正常使用，（2）颤振一般就是主梁扭转或弯扭耦合，因扭转是发散的，故发生颤振后结构位移会越来越大，即共振。颤振与结构扭转频率和扭弯频率比都有关系，这两者越小越容易导致颤振发生。
         3.本桥跨径虽不大，但设计采用H形索塔平行拉索体系、索塔之间无横梁、主梁开口截面、主梁宽跨比又很小，两个独立塔柱纵桥向反向摆动时会加剧主梁扭转，以上不利因素叠加导致本桥扭转频率和扭弯频率比很低，极有可能导致颤振的发生。

如此看来现今我们中国的设计师还考虑的更周全些喽！

截面确实不是闭口的

上传一些该桥的布置图以及施工照片，图片来自网络。
看图片该桥应该是施工了单幅后就开放了交通。
纵梁横向联系均为开口截面工字型梁。

Bolts, cables examined as officials investigate Nipigon Bridge collapse

Forty steel bolts that were meant to keep the deck of the new, $100-million Nipigon River Bridge securely fastened down have been sent to two independent labs in Ontario for testing and analysis as provincial officials continue to search for what caused the bridge to buckle.

Still, the hope is to have the bridge that crosses the Nipigon River re-opened to two lanes of traffic by the end of February, restoring the link along the TransCanada Highway between eastern and western Canada, Ontario Transportation Minister Steven Del Duca told reporters in a conference call Tuesday morning.

The bridge has been reduced to one lane of traffic since Jan. 10 when it suddenly broke apart – with one section of it lifting 60 centimetres. It had only been opened for a couple of months when it failed.

It is on the only route through Canada, and is regularly used by commercial truck drivers. Drivers now face delays of between five and 10 minutes as a pace car guides the traffic across at a speed of about 25 kilometres an hour.

Exactly what caused last week’s break in the bridge remains a mystery. The Ministry of Transportation does not know how much all this will cost or who is responsible.

“We are taking into account at this point a number of possible factors and we haven’t ruled anything out,” said Mr. Del Duca, who stressed that the design of the bridge met the Canadian Highway Bridge Design Code and was built to withstand winds of more than 100 km/h and temperatures below -40 C.

One possible factor being looked at is the role of the 40 bolts, which are 22 millimetres in diameter and 150 mm in length, and secured the deck of one lane to beams. The bolts were manufactured by R.J. Watson, a reputable firm, in New York State. 螺栓由R.J.Watson 制造。

Mr. Del Duca said the bolts are being examined by the National Research Council of Canada and the University of Western Ontario.

The bolts will undergo a visual and chemical analysis. Experts will also look at their “mechanical properties,” a “determination of the nature of the failure,” and a comparison of how they stack up to the design specifications, according to Mr. Del Duca, who read a statement describing the operation.

Officials are also studying the tension on cables that help support the bridge. This is Ontario’s first “cable-stayed bridge” – the weight of the deck is supported by overhead cables.

Gerry Chaput, assistant deputy minister, provincial highways management division of the Ministry of Transportation, said that because the buckling was at one end of the bridge, there was some concern the cables were too tight.

He said this issue has been reviewed, and that the tension on the cables was appropriate for the loads and other factors affecting the bridge. However, he said, they continue to “look at numerous factors as to what caused the failure.”

Queen’s University civil engineering professor Mark Green said that officials will want to find out through the analysis of the bolts whether they had adequate strength for the job they were doing; some grades of steel are much stronger than others and are better at lower temperatures.

In addition, he said a visual examination of the bolts will show whether they were pulled apart or sheared-off, which will help in analyzing the combination of factors that may have led to the bridge buckling.

He said the encouraging news is that the bridge is intact.

“So it’s just really determining … is there something with these bolts that it wasn’t exactly as expected. Were they loaded in some way that wasn’t exactly understood?” he said.

Progressive Conservative transportation critic Michael Harris said that testing materials for this bridge should not be taking place after the fact.

“It’s too late then,” he said. “Where was the oversight and the proper engineering testing to ensure quality materials were being used and that the construction was being done as per plan, if the plan was even proper in the first place.”

Nipigon River Bridge updates

January 25, 2016      

• Visual examination of the bolts has  been completed by both labs.
• Physical testing of the bolts to begin today.
• Expected wait time to cross less than five minutes.
  

      January 22, 2016      

• Physical testing of the bolts will begin Monday at both NRC and Surface Science Western.
• Conceptual repair designs submitted for review.
  

      January 21, 2016      

• Bridge and roadway lights activated to improve safety.
• Associated Engineering (Ont.) Ltd. will conduct an independent review of the repair design.
  

      January 20, 2016      

• Expected wait time to cross less than five minutes.
  

      Statement by the Minister of Transportation on Nipigon River Bridge      NEWS      January 19, 2016
      "I am pleased to provide an update on the Nipigon River Bridge situation.
      Earlier today, Minister of Northern Development and Mines Michael Gravelle and I spoke with municipal and First Nations representatives from across the region to provide them with a progress update on both the work to find a cause for the recent bridge issue and our progress in re-opening both lanes of the bridge to traffic.
      Two respected research and testing facilities have been selected to conduct testing of the bolts from the bridge: Surface Science Western and the Faculty of Engineering at Western University and the National Research Council of Canada.
      This week, the labs will be completing an independent, visual ‎examination of the bolts.  Once that examination is complete, the two labs will be in a better position to determine how long the full testing will take. Full testing will include a chemical analysis of the bolts, a determination of the nature of the failure, a confirmation of the mechanical properties of the bolts as well as a comparison of the bolts to design specifications.  We have expressed to both research labs that this testing is a top priority for our government, however, it is important that we get it right, and that will take some time.
      This testing will help the ministry determine the cause of the issue and develop a permanent solution.
      The ministry continues to work with the Ontario Professional Engineers who performed the design of the bridge at WSP (formerly McCormick Rankin Corp in Mississauga), and the Canadian firm that provided additional cable stayed bridge expertise, Buckland Taylor in British Columbia. The design was performed in accordance with the Canadian Highway Bridge Design Code and is capable of withstanding the necessary Code design parameters for winds in excess of 100 km/h and climatic conditions including freezing temperatures well below -40 degrees celsius. The tensioning of the cables has been confirmed however, the ministry has not yet ruled out any factors in its investigation of the cause. All of this work, combined with the results from the Western University and NRC analysis, will help the ministry determine the cause of the issue and allow our engineers to begin the development of a permanent solution.‎ Together with the contractor, a joint venture with Bot Construction Canada and Ferrovial Agroman Canada Inc., and their suppliers from within North America, significant efforts will continue to provide a safe and reliable solution that will open the bridge to two lanes.
      The ministry is also currently reviewing a number of repair options to open the Nipigon River Bridge to two lanes of traffic. Each option proposes a different connection method and location to connect the bridge deck to the foundation. The chosen solution will also be peer reviewed by Ontario and other Canadian engineers.
            To complete the work, occasional lane closures and temporary short-term full closures of the bridge during off-peak hours will be necessary.  Notice of the complete closures will be provided well in advance to the neighbouring communities and travelers through our website and 511, MTO’s Road Information Line.  Our goal is to re-open the bridge to two lanes by the end of February.            Work on the demolition of the old bridge remains paused as we focus on fully reopening the bridge to traffic and implementing a permanent solution.
      Again, please be assured that I take my responsibilities for road safety seriously. That is why the design of the Nipigon River Bridge was completed by professional engineers licensed in Ontario. The design is in compliance with the Canadian Highway Bridge Design Code which considers regional climate conditions.
      I would like to thank everyone for their continued patience. MTO will continue to provide regular updates to the public as information becomes available. I would also like to thank Michael Gravelle for his leadership on behalf of the local community. For the latest information on highway closures, the public can call 511 or check Ontario.ca/511."
      January 18, 2016      

• Traffic signals are now being used to move one lane of traffic over the bridge.
• Expected wait time to cross less than five minutes.
  

      January 15, 2016      

• Two independent testing facilities have been selected to conduct testing to determine the cause of the bolts failure: National Research Council of Canada in Ottawa and Surface Science Western at Western University.
• Testing work is expected to ‎start on Monday.
• Wait times continue to be less than five minutes.
  

      January 14, 2016      

• Minister  Gravelle and Minister Del Duca attended site yesterday and met with Mayor  Richard Harvey from the Town of Nipigon and Chief Wawia and council members  from Red Rock FN including regional Chief Pelletier for Robinson Superior  Treaty and Chief Hardy from‎ Biinjitiwaabik Zaaging  Anishinaabek
• 24-hour  monitoring of the bridge joints and bearings continues.
• One  lane of traffic continues to move over the bridge, under flagging conditions  and with a pace vehicle.
• Expected  wait time to cross less than 5 minutes
  

      Statement by the Minister of Transportation on Nipigon River Bridge      NEWS      January 11, 2016
      The  following statement is from the Hon. Steven Del Duca, Ontario’s Minister of  Transportation:
      “As  Ontario’s Minister of Transportation, my number one priority is the safety of  all roads and highways in this province.  
      On Sunday afternoon, the OPP closed the Nipigon River  Bridge to traffic due to safety concerns.  
      Ministry staff worked through the night to rectify the  situation, using counterweights to level the bridge surface. An engineering  inspection was also completed to ensure the safety of the bridge and the  travelling public.  
      Keeping  Ontario moving is a shared priority of all involved, and I commend the  hardworking crews who laboured throughout the night to return this important  piece of highway infrastructure to the safe, driving condition all Canadians  expect.
      As of this statement, one lane is open for cars and  regular weight transports.  Staff are continuing to work to determine when  oversized trucks can use the bridge
      Crews  remain on site to identify the cause of the issue and updates from MTO will be  communicated as they become available. For the latest information on highway  closures, the public can call 511, MTO’s Road Information Line or check www.Ontario.ca/511.      
      My  colleague Minister Michael Gravelle will be visiting Nipigon River Bridge this  morning. I look forward to visiting the site later this week to survey the site  myself and I will provide a further update at that time.
      Again,  I would like to thank all affected travellers, the local First Nations  communities and townspeople along Highway 11/17 for their patience and  understanding as we took the necessary steps to return this piece of critical  infrastructure back to service.”