Florida International University pedestrian bridge collapse

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The FIU Pedestrian Bridge Collapse
FIU Bridge NTSB inspection.jpg
National Transportation Safety Board members inspecting the collapsed pedestrian bridge on March 16
Time 1:47 p.m. EDT
Date March 15, 2018 (2018-03-15)
Location University Park and Sweetwater, Florida, U.S.
Type Bridge collapse
Deaths 6
Non-fatal injuries 9
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On March 15, 2018, a 175-foot-long (53 m), recently-erected section of the FIU Sweetwater UniversityCity pedestrian bridge collapsed onto the Tamiami Trail (U.S. Route 41).

The initial construction on the pedestrian bridge was located in front of the campus of Florida International University (FIU) in University Park, a suburb west of Miami, Florida, United States, and was in the process of post-tension rod adjustment when it suddenly failed.[1] The road beneath it had been opened to traffic. Several occupied vehicles were crushed underneath, which resulted in six deaths and nine injuries.[2]

Background

The FIU Sweetwater UniversityCity pedestrian Bridge, located just west of the intersection of Tamiami Trail (Southwest 8th Street) and Southwest 109th Avenue[3], was planned to connect the FIU campus to student housing neighborhoods in Sweetwater.[4] It was intended to improve pedestrian safety, as the busy crosswalks at this wide, busy intersection had been identified as a safety hazard and the site of fatal collisions.[5] The $14.2 million project was funded with a $19.4 million Transportation Investment Generating Economic Recovery (TIGER) grant from the United States Department of Transportation in 2013, along with state agencies.[6] The bridge itself cost $9 million to construct.[7]

The main companies behind the construction project are Munilla Construction Management (MCM), a Miami-based construction management firm, and FIGG Bridge Engineers, a Tallahassee-based firm.[8] Unlike most bridges in Florida, the design for this project was overseen by the university itself, not the Florida Department of Transportation.

Florida International University is known for its expertise in accelerated bridge construction, and has attracted international scholars as PhD students. It is home to the federally-funded Accelerated Bridge Construction University Transportation Center, which sponsors industry conferences and seminars.[9][10]

Bridge layout

Elevation Engineering Drawing of Proposed FIU Sweetwater Pedestrian Bridge

The full 320-foot-long (98 m) pedestrian bridge was to cross both a major roadway and a parallel water canal with two separate spans connected at a faux cable-stay tower. The main, roadway-crossing span was 175 ft long, the shorter canal span was to be 99 ft long. An elevator and stairs at the south end added 31 ft, and at the north end, 15 feet, for a total bridge length of 320 feet.[11] At the bridge site, the Tamiami Trail roadway has six lanes of traffic plus two turn lanes. The main span was rolled into place and set on support columns on March 10, five days before the collapse. The canal span, access ramps, and faux cable-stay tower had not yet been built. Pedestrian use was to begin when the whole project was complete. The school was on spring break at the time of collapse.[1] The section of the bridge that collapsed weighed 950 short tons (860 metric tons) and fell onto several vehicles on the roadway below.

Bridge construction and design

Construction of the bridge began in March 2016 and was scheduled to be completed in December 2018.[7][12] The bridge's main span was assembled adjacent to the highway using accelerated bridge construction (ABC), a technique promoted at the university.[1] It was lifted into place on the morning of March 10, five days before the collapse, during a weekend closure of the highway.[13][14]

FIU-Sweetwater UniversityCity Bridge
Coordinates Lua error in Module:Coordinates at line 668: callParserFunction: function "#coordinates" was not found.
Carries Pedestrian traffic
Crosses Tamiami Trail
Locale University Park and Sweetwater, Florida, U.S.
Characteristics
Total length 320 feet (98 m)
Longest span 175 feet (53 m)
History
Engineering design by FIGG Bridge Engineers
Constructed by Munilla Construction Management
Construction cost $14.2 million
Collapsed March 15, 2018
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The new pedestrian bridge was designed to connect the campus to student housing in a dramatic sculptural way, and also to showcase the school's leadership in the ABC method of rapid bridge construction.[15][16]

The bridge was a post-tensioned concrete structure.[15] Concrete structures are generally 10 times heavier than equivalent steel designs.[17] The bridge was made using a new formulation for concrete intended to stay cleaner than standard concrete formulations.[18] In the main bridge span, the concrete floor deck, roof, and diagonal struts each contained post-tensioning cables whose compressive effect on the concrete could be adjusted after the concrete was cured.[15] Adjustments were expected each time the span was moved onto a different foundation with different support points.

The full bridge project was styled to look like a cable-stayed bridge, with a pylon tower and high cables for dramatic effect. But functionally and structurally it was actually a truss bridge, with the spans being fully self-supporting.[15][19][20] The bridge spans used a novel concrete truss design invented for this project, a "re-invented I-beam concept". Concrete truss bridges are rarely constructed, and few exist.[21] The vertical web of the beam was a series of triangulated concrete diagonal struts along the centerline, and the diagonal angles of the struts varied across the bridge so they would align with pipes from the center pylon, in the eventual faux cable-stayed appearance.[22]

A specification change from FDOT (https://cdn2.fdot.gov/fiu/11-FIU-Pylon-Location-Meeting-10-31-16.pdf) late in the planning phase required relocating the entire structure 12 feet (4 meters) north to allow for a future bus lane right-of-way near the canal instead of the opposite side of the road, causing some changes in construction.[23]

The concrete walkway deck was to act as the horizontal bottom flange of a wide I-beam, and the concrete roof canopy was to function as the horizontal top flange of the I-beam.[15] The walkway was thus nearer to ground level than in a standard design where the walkway is placed on top of the structural support system.[15] This reduced the number of steps to climb. The deck carries the entire weight of the bridge span, as a tension load.

The canopy carries the structure's main compressive loads. The diagonal struts carry either compression or tension forces, depending on their angle and position. The struts contain post-tensioning rods that connect the flanges, and are adjusted as needed.[24] VSL was the company contracted for the post tensioning (PT) of the new bridge. Post-tensioning of a diagonal member may be one of the reasons for the structural failure of the FIU bridge. Concrete is much more prone to crack than steel in trusses. [25] Certain cracks could compromise the cable/rod anchorings, making failure inevitable when the post-tensioning operation began.[26]

The bridge was meant to last more than 100 years, and to withstand a Category 5 hurricane, according to a statement by the university.[27]

Collapse

Schematic of the bridge. Green: collapsed parts, Blue: not installed at the time of the collapse. The diagonal beam that was undergoing post-tension cable/rod adjustment at the time of the collapse is highlighted in red.

Reports of cracking

On March 13, the third day after lifting of the main span, the project's lead engineer discovered cracks at the north end of the span (the end that later broke). He reported this by voicemail to a Florida Department of Transportation (FDOT) employee. He thought this was not an immediate safety issue, merely something that would need to be repaired later. The FDOT recipient was away for several days and did not hear this message until the day after the collapse.[28][29]

At 9 a.m. on March 15, a university employee heard a loud "whip cracking" sound while under the bridge span, waiting for a red traffic light.[30] At the same time, the design-build team met for about two hours at the construction site to discuss the cracks discovered on March 13. Representatives from both FIU and the FDOT were present. The FIGG lead engineer's conclusions were that the structural integrity of the bridge was not compromised and that there were no safety concerns raised by the presence of the crack.[31]

The mayor of Miami-Dade County, Carlos A. Giménez, said that workers conducted a stress test on the morning of March 15.[32]

Collapse

At 1:47 p.m., the north end of the installed bridge span sagged deeply as the first diagonal fractured, folded, and immediately dropped the heavy full span onto the roadway below. A surveillance video shows the collapse sequence took only a few video frames.[33]

United States Senator and FIU adjunct professor Marco Rubio tweeted that engineers were tightening loosened cables on March 15:[32] Workers were adding more tension to the steel rod (tendon) inside a concrete diagonal strut at the north end.[28] The National Transportation Safety Board, who are investigating the collapse, stated that crews were applying "post-tensioning force" on the bridge before the collapse.[34]

The tensioning rod that was being tightened at the time of the collapse, with a hydraulic tensioning machine (blue) still attached to its end, extends from the canopy in the upper left of this image.

At this time, it is not clear why the post-tensioning operation by VSL company was being carried out at the time of the collapse as the bridge diagonal member support they were working on would have already been in compression. The bottom joint of diagonal member #11 (which contains the anchor nut for the post-tensioning rod) apparently failed explosively, during the post-tensioning operation, causing the bridge to collapse. Currently, it remains unknown why the joint may have failed, although post-tensioning remains a possible contributor.[35]

The span that collapsed weighed 950 short tons (861 tonnes).[36]

At the time of the collapse, the roadway was open and there were multiple cars stopped at a traffic light under the span.[37][38] A driver who survived the collapse reported small rocks fell onto her car just before the car got smashed.[39] A worker saved himself when he heard cracking and locked his safety harness just before the collapse.[40] Eight cars were reported to have been crushed. Six people were killed and nine others were injured; while early reports said that the death toll was expected to rise,[2] authorities said on March 18 that all bodies had been accounted for.[41] Five of the victims were killed immediately when the bridge fell; one died at the hospital. An employee of VSL, Navaro Brown, 37, worked for the company contracted to apply post-tensioning and died in the collapse. Two other employees of the company were hospitalized. The other deceased victims of the tragedy were identified as Alberto Arias, 53, Brandon Brownfield, 39, FIU student Alexa Duran, 18, Rolando Fraga, 60, and Oswaldo Gonzalez, 57.[42][43][44]

Aftermath

On March 16, the Florida Highway Patrol announced Southwest 8th Street between Southwest 107th and 117th Avenues and the eastbound Southwest 8th Street exit from the Homestead Extension of Florida's Turnpike would be closed indefinitely while debris removal and investigations were conducted.[45] Debris from the bridge was cleared by March 24, allowing Southwest 8th Street to be reopened.[46] A team of 15 people from the National Transportation Safety Board (NTSB) began their investigation on the morning of March 16.[47] On March 19, 2018 the first civil lawsuit was filed against Figg Bridge Engineers, MCM, Bolton Perez & Associates, the project’s consulting engineer, Louis Berger, and Network Engineering Services for reckless negligence.[48]

Inquiry

Members of the NTSB's Go Team for the investigation boarding an FAA plane to travel to Miami.

On March 15, 2018 the National Transportation Safety Board (NTSB) launched a Go-team to investigate the bridge collapse. The accident number assigned is HWY18MH009. [49] On March 16, 2018 the NTSB Investigators held their first press conference to discuss the inquiry into the bridge collapse. Noteworthy points from the meeting included a statement that the inquiry was in the very early stages, that cracks in the bridge superstructure did not necessarily make the bridge unsafe, that on-site investigations would take about a week, that preserving perishable evidence was crucial, and that bridge workers were applying a "post-tensioning force" on the bridge before the failure.[50] Also on March 16, 2018 the FDOT released a letter to the public with information about the bridge collapse:

According to standard procedures, FDOT issued a permit at the request of FIU’s design build team to close SW 8th Street during the installation of the FIU pedestrian bridge on Saturday, March 10. While FDOT has issued, following a request from the FIU design build team, a blanket permit allowing for two-lane closures effective from January through April, at no time, from installation until the collapse of the bridge, did FDOT receive a request to close the entire road. The department was also not made aware by the FIU design build team of any scheduled “stress testing” of the bridge following installation and has no knowledge or confirmation from FIU’s design build team of “stress testing” occurring since installation. Per standard safety procedure, FDOT would issue a permit for partial or full road closure if deemed necessary and requested by the FIU design build team or FIU contracted construction inspector for structural testing.

Additionally, in the interest of full transparency, FDOT is today releasing the transcript of a voicemail left on a landline on Tuesday, March 13, by W. Denney Pate, FIGG’s lead engineer responsible for the FIU pedestrian bridge project. The transcription is below and audio is available HERE:

“Hey Tom, this is Denney Pate with FIGG bridge engineers. Calling to, uh, share with you some information about the FIU pedestrian bridge and some cracking that’s been observed on the north end of the span, the pylon end of that span we moved this weekend. Um, so, uh, we’ve taken a look at it and, uh, obviously some repairs or whatever will have to be done but from a safety perspective we don’t see that there’s any issue there so we’re not concerned about it from that perspective although obviously the cracking is not good and something’s going to have to be, ya know, done to repair that. At any rate, I wanted to chat with you about that because I suspect at some point that’s gonna get to your desk. So, uh, at any rate, call me back when you can. Thank you. Bye.”

This voicemail was left on a landline and not heard by an FDOT employee until Friday, March 16 as the employee was out of the office on assignment. When the employee returned to his office today, Friday, March 16, he was able to listen to the voicemail.

In addition to the voicemail transcribed above, on Wednesday, March 14, Alfredo Reyna, the Assistant LAP Coordinator and an FDOT consultant, received a phone call from Rafeal Urdaneta, a Bolton Perez & Associates employee, notifying him of a midday meeting scheduled for Thursday, March 15 with W. Denney Pate and other members of the FIU design build team that are responsible for the project. FDOT is routinely included in meetings during LAP project construction. Reyna attended the meeting which occurred shortly before the bridge failure and collapse and was not notified of any life-safety issues, need for additional road closures or requests for any other assistance from FDOT.

The responsibility to identify and address life-safety issues and properly communicate them is the sole responsibility of the FIU design build team. At no point during any of the communications above did FIGG or any member of the FIU design build team ever communicate a life-safety issue. Again, FIGG and the FIU design build team never alerted FDOT of any life-safety issue regarding the FIU pedestrian bridge prior to collapse.

The tragic failure and collapse of the pedestrian bridge at FIU is the subject of an active and ongoing investigation led by the National Transportation Safety Board (NTSB) as well as local and state law enforcement investigations. As FDOT assists in these investigations, we will continue our internal review and release all pertinent information as quickly as possible while ensuring its accuracy.

[51]

On March 21, 2018 the NTSB sent out the following press release:

Investigators secured a contract Tuesday to have a company remove components from the bridge that we believe warrant additional examination and testing. These components include sections of the floor, the canopy, a vertical member and a diagonal member; all from the north end of the structure. These components were in the area of where the failure occurred. In addition to these components, we obtained additional core samples from this area to supplement the core samples we obtained earlier. Shipping the core samples along with some recovered rebar and tensioning rods to the Turner Fairbank Highway Research Center, in McLean, Virginia, for testing and evaluation. The investigative team has obtained an exemplar tensioning rod and hydraulic unit used by the construction crew to make tension adjustments to the tensioning rods. These items are also being shipped to the Turner Fairbank Highway Research Center for evaluation and testing. The larger bridge components the investigative team is removing, are being stored at a secured Florida Department of Transportation facility, under the control of the NTSB. The additional examinations and forensic deconstruction of these components will occur there. The investigative team has confirmed that workers were adjusting tension on the two tensioning rods located in the diagonal member at the north end of the span when the bridge collapsed. They had done this same work earlier at the south end, moved to the north side, and had adjusted one rod. They were working on the second rod when the span failed and collapsed. The roadway was not closed while this work was being performed.

Also, on March 21, 2018 U.S. Transportation Secretary Elaine Chao asked the department’s inspector general to probe whether a federally funded UniversityCity pedestrian bridge complied with all rules.[52] A subsequent internal memorandum from the Inspector General of the U.S. Department of Transportation, dated March 22, 2018 included the following statements:[53]

The Florida International University pedestrian bridge was funded in part through the Department of Transportation's (DOT) Transportation Investment Generating Economic Recovery (TIGER) discretionary grant program.1 The Federal Highway Administration administered the grant funds for the project. On March 19, the Secretary of Transportation requested that we initiate an audit to evaluate whether the project complied with Federal requirements and specifications. On March 20, Senator Bill Nelson, Ranking Member of the Committee on Commerce, Science, and Transportation, requested that we also review the implementation and oversight roles of all parties on the project. We share these concerns about the collapse, and we are committed to supporting the Department's efforts to improve transportation safety. Accordingly, the objective of our audit will be to assess whether the Florida International University pedestrian bridge met Federal and DOT requirements for the TIGER application, approval, and grant agreement processes.

On March 28, 2018 the Miami Herald reported they were denied access to FIU documents related to the bridge construction, citing federal regulations that prevent release of non-public information related to the bridge construction and design project when an NTSB investigation is in progress. A lawyer for Reporters Committee for Freedom of the Press indicated more information should be released under the Florida Sunshine Law, due to intense public interest in the collapse.[54]On May 2, 2018, the Miami Herald filed a lawsuit against FDOT in Florida's Leon County Circuit Court to compel the FDOT to release emails, meeting minutes and other records relating to the bridge's design and construction.[55]On May 3, 2018, a lawyer for the NTSB wrote a letter to Judge Cooper of the 2nd Judicial Circuit of Florida in Tallahassee, FL urging the court to deny a ruling that would favor the Miami Herald plaintiff, for the release of any bridge information generated after a February 19, 2018 cutoff date:

I write to provide you with additional information about the National Transportation Safety Board's (NTSB) ongoing investigation into the collapse of the Florida International University(FIU)/Sweetwater pedestrian bridge on March 15, 2018, as well as to confirm the restrictions in place on the Florida Department of Transportation (FDOT) regarding disclosure of investigative information. It is my understanding that the NTSB's investigation impacts Miami Herald Media Company v. Florida Department of Transportation, Case No. 2018 CA 000993, which is pending before you.

The NTSB appreciates that you wish to progress the Miami Herald case. Since the beginning of our investigation, pursuant to 49 C.F.R 831.13, the NTSB has prohibited the Florida Department of Transportation and all other parties to our investigation from releasing investigative information in response to public records requests absent NTSB approval. In this context, the term "party" means an organization appointed to provide technical assistance to the NTSB. It is not an adversarial designation. Party participation in our investigation is critical, as the parties possess unique technical information about the specifics of the bridge design, construction and installation processes, as well as events which occurred in the days leading up to the accident. It is important to note that in addition to the ongoing NTSB investigation, the bridge collapse is also the subject of multiple other ongoing investigations. Specifically, there are federal criminal investigations being conducted by at least two federal agencies, as well as several federal regulatory investigations, and a criminal investigation being conducted by the Miami-Dade police department. All of the investigating agencies are parties to the NTSB investigation, and have significant interest in not having investigative information publicly released at this time. Recognizing the intense public interest in this accident, the NTSB has undertaken to authorize release of as much investigative information as possible while ensuring the integrity of the ongoing investigations. To that end, and in coordination with the other investigative agencies, we have authorized FDOT to release, pursuant to Florida law, all responsive materials in its custody or control which existed on or before February 19, 2018. This restriction remains in place as to all investigative information, not limited to information developed during the course of the investigation after the accident. See 49 C.F.R 831.13(a) l . The February 19, 2018 cutoff date is not arbitrary; we conducted an initial review of the evidence and determined that while the earlier information is important, it is not as critical to the investigations as information after that date. I have engaged in telephone conversations with counsel for the Miami Herald to explain the scope of our restrictions, and to explain that the restrictions of 49 C.F.R 831.13 are temporary; once they are lifted by the NTSB, parties to our investigation, including FDOT, will no longer be prohibited from releasing the investigative information they possess. Further, the NTSB has committed to periodically review the materials which remain restricted, and to authorize release as soon as possible consistent with the needs of the investigation. The NTSB is deliberately and carefully conducting the investigation because of its utmost concern for the public's safety. Through its investigative work, the NTSB determines the probable cause of the collapse and develops safety recommendations to prevent a similar accident from occurring in the future. Safety is the NTSB's mission. The agency does not regulate the transportation industry, and except in small measure related to the licensing of pilots and mariners, the NTSB does not enforce transportation laws. Instead, it is an independent accident investigation agency. The NTSB has an exemplary record of industry and other government agencies implementing its safety recommendations, even though they are nonbinding. The recommendations are accepted because (1) the agency's independence ensures that it is impartial and objective; and (2) the agency commits considerable resources and expertise to each investigation to formulate a safety-centered solution. In a complicated investigation such as this, cooperation from witnesses and others involved in the design, construction and installation of the bridge is critical. If investigative information is released prematurely, it can lead to witnesses refusing to talk to us, changing their stories, or potentially destroying evidence. We have also found that premature public disclosure results in reduced cooperation by the parties to our investigation because suddenly they are focused on public relations concerns and responding to often erroneous information in the press, rather than diligently assisting our investigation to understand the causes of the accident.

[56]

On May 7, 2018 the Miami Herald reported they had received a copy of a memo with photographs from FIU dated February 28, 2018 that had been sent to the Munilla Construction Management company, the bridge project's builder. The memo, which has since been rescinded back from Public view, purportedly urged the bridge engineer to respond to their concerns about significant cracks in the concrete joint at connection between the No. 11 truss and the bridge deck.[57]

See also

References

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  2. 2.0 2.1 Shapiro, Emily; Doom, Justin (March 16, 2018). "Bridge collapse death toll likely to rise as investigators sift through rubble". ABC News. Retrieved March 16, 2018. 
  3. "FIU Bridge Collapse: Four Dead, 8 Cars Trapped Underneath". CBS Miami. March 15, 2018. Retrieved March 17, 2018. 
  4. Ashaboglu, Selin (March 15, 2018). "Miami Pedestrian Bridge Collapses". ARCHITECT. Retrieved March 15, 2018. 
  5. Rodriguez, Marybel (August 22, 2017). "Pedestrian Bridge In The Works For FIU Students To Cross Busy 8th Street". CBS 4 Miami. Retrieved March 15, 2018. 
  6. "FIU Pedestrian Bridge Construction Using Innovative Approach By Swinging Into Place". CBSLocal. WFOR-TV. March 10, 2018. Retrieved March 15, 2018. 
  7. 7.0 7.1 Harris, Alex (August 24, 2017). "A walking bridge for FIU students is coming soon. But it's too late for one student". Miami Herald. Retrieved March 15, 2018. 
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  9. Bridge Collapse Saps Spirits and Research Efforts at Florida International University, By PATRICIA MAZZEI and STEPHANIE SAUL, New York Times, March 17, 2018
  10. "Home - Accelerated Bridge Construction". Accelerated Bridge Construction. Retrieved March 19, 2018. 
  11. "General Plan and Elevation" (PDF). Florida International University. Retrieved March 23, 2018. 
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  14. Madan, Monique O. (March 8, 2018). "If you plan to drive on SW Eighth Street this weekend, you'll be rerouted here". Miami Herald. Retrieved March 15, 2018. 
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  18. News, F. I. U. (March 10, 2018). "#DidYouKnow the new pedestrian bridge that will connect our FIU and the @CitySweetwater is the first in the world to be constructed entirely of self-cleaning concrete? #WorldsAheadpic.twitter.com/lQVJh09Pv2". @FIUnews. Retrieved March 17, 2018. 
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  21. Bridgehunter. "concrete truss bridges". Retrieved March 21, 2018. 
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  29. "Bridge collapse victim's uncle rages at 'incompetence'". 
  30. "FIU employee heard a loud crack crossing under the bridge. Hours later, it collapsed.". miamiherald. Retrieved March 17, 2018. 
  31. Mier, Alyse (March 17, 2018). "FIU statement" (Press release). FIU. Retrieved March 17, 2018. 
  32. 32.0 32.1 "Rubio says engineers were tightening loose cables when the FIU bridge collapsed". miamiherald. Retrieved March 17, 2018. 
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  36. Cochrane, Karen (March 16, 2018). "Pedestrian Bridge FAQ" (Press release). FIU. Retrieved March 17, 2018. 
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  44. "New video surfaces of FIU bridge collapse from view of driver who witnessed it". 
  45. "Southwest 8th Street To Be Closed As Bridge Collapse Is Investigated". CBS Miami. March 16, 2018. Retrieved March 16, 2018. 
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  51. http://www.fdot.gov/info/CO/news/newsreleases/default.shtm
  52. Editorial, Reuters. "U.S. Transportation Secretary seeks probe of fatal Florida bridge...". 
  53. https://www.oig.dot.gov/sites/default/files/Audit%20Announcment%20-%20DOT%E2%80%99s%20Oversight%20of%20Pedestrian%20Bridge%20Project%5E3-22-18.pdf
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  55. http://www.miamiherald.com/news/local/community/miami-dade/article210298454.html
  56. https://cloudup.com/cW7td9cgf3o
  57. http://www.miamiherald.com/news/local/community/miami-dade/article210449384.html

External links