At about 9:00 a.m. on February 1, 2013, a truck loaded with explosives was traveling from west to east to the Yichang River Bridge in Hongyang Township at 741km+900m on the Lianhuo Expressway (in Sanmenxia Mianchi County, Henan Province) when it suddenly exploded, resulting in the southern half of the bridge being blown up and the northern half of the bridge deck being loosened. A number of moving vehicles fell 30 meters under the bridge.
Sanmenxia police said more than 80 meters of the 160-meter Yichang River Bridge, which is about 30 meters above ground, collapsed. Twenty people have been searched and rescued, with 10 confirmed dead and 11 injured, four of them seriously, and the injured have been rushed to hospitals for resuscitation. The injured have been rushed to hospitals for rescue. The hospitals for rescue are the Mianchi County People's Hospital; the Mianchi County Hospital of Traditional Chinese Medicine; the General Hospital of the Yi Coal Group; and the People's Hospital of Yima City. The reporter also learned from the Henan Highway Traffic Police Headquarters that the highway traffic police, the fire brigade, the road administration and 120 personnel had rushed to the scene for emergency rescue. The north and south halves of the roadway were all bombed and collapsed with a bridge height of 30 meters and a length of more than 80 meters. The scene has been cleaned up 2 small cars, 6 large cars, did not find the bus crashed.
Implementation of traffic control, the cause of the bridge collapse incident is the delivery of fireworks car explosion, caused by the bridge collapse. In the afternoon of the 4th, Lianhuo high-speed Yichang bridge collapse accident 10 victims of the list was released, of which 8 men, 2 women, respectively, from Henan, Shandong, Jiangsu and other places.
Name Gender Domicile
Zhang Chunfu male Shandong Gaomi City
Feng Junke male Henan Pingdingshan
Hou Yanxin male Henan Anyang City
Golden Yi male Henan Decorative Sichuan County
Dong Zhengong male Jiangsu Pizhou City
Sun Yowen male Shandong Zhangqiu City
Wang Gaozhong male Jiangsu Nantong City
Chen Jin Yun female Jiangsu Nantong
Wang Luzhou male Jiangsu Dongtai
Shen Yulan female Jiangsu Dongtai Original title: surviving piers did not see the hoop reinforcement bridge deck fracture like a knife cut - Yichang Bridge collapse: the pier reinforcement is too little?
At 9 a.m. on Feb. 1, 2013, the Yichang Bridge on the Henan Mianchi section of the Lianhuo Expressway, a truck loaded with fireworks from west to east, suddenly exploded, resulting in the southern half of the bridge being destroyed, and the northern half of the bridge boards being loosened. Ten people have been confirmed dead and 11 injured, four of them seriously. Two small cars and six large vehicles were cleared from the crash site.
At the site of the collapsed bridge, the Times reporter did not find the presence of hoops within a section of broken piers. As we all know, the concrete piers should be equipped with enough reinforcing steel, vertical steel and horizontal steel (hoop bars) to form a reinforcing cage in order to withstand enough heavy load. But Yichang Bridge abutment, according to professionals, rebar "steal too much".
Surviving piers did not see the tendons
The day after the explosion, the morning of February 2, the scene is still a mess. Twisted, even disintegrated front end, blown tires, scattered with a variety of goods and debris, layers upon layers. Broken bridge decks and piers were also mixed in.
When the bridge collapsed, the two piers supporting the bridge deck broke and collapsed, and from the photos of the scene released by the media on the day of the accident on Feb. 1, there is still a section of more than 10 meters long of cylindrical steel overlaying the scene.On Feb. 2, this section of the piers has been moved.
The Times reporter at the scene found a section of broken piers, the length of 80cm or so, cylindrical surface has been broken, but still maintains the basic outline. Several vertical threaded steel bars remained on the periphery of the cylinder, and judging by the grooves on the surface, the vertical bars encircled the periphery of the abutment in a circle.
At another part of the site, the fallen bridge deck overlay a longer section of the fractured cylindrical abutment, but the Times reporter could only see vertical rebar in the fractured cross-section as well, with no rebar horizontally.
"The rebar inside the piers is called reinforcement." A senior architectural designer told the Times, "The reinforcing bars of a bridge pier should theoretically be in the form of a reinforcing cage, which is made of steel bars woven into a cage. Reinforcing steel is like a person's skeleton, if the skeleton is too small, the person can't stand up."
"The horizontal reinforcement that crosses with the vertical reinforcement to form the cage is generally called hoop reinforcement. From the photo (referring to the scene picture taken by the reporter) of this node, this point of reinforcement is not enough, can only see the vertical reinforcement, the horizontal direction of the hoop can not be seen. This is completely nonsense. This is what is often said in the industry: the rebar 'stole too much'." The above source pointed out.
The professional further explained: the bridge pier is mainly to withstand the pressure from the bridge deck, the use of concrete compression performance is good, but the concrete tensile (to withstand the horizontal direction of the tension) can not be, the tensile properties of steel reinforcement is good. Abutment inside the addition of steel, the strengths of the two are combined into one. Bridge piers to withstand horizontal (lateral) loads, an analogy, there is a force from the side of the bridge to push the bridge, this time, the rebar will have to withstand such a force.
"Look at this bridge abutment, more than 30 meters high, longitudinal rebar, no matter how thick you are, 30 meters away must be soft, so you need to use a fine hoop. High-speed rail and urban elevated construction photos online, look at their reinforcing cages to know." The person introduced, the general design specification requirements, the spacing of the hoop is 10-15cm, in some connection position but also appropriate encryption, the hoop also use the threaded steel bar (the surface of the flute-like protrusion), the minimum diameter of 6mm.
Design or construction problems
Time Weekly reporter has been with the Henan Department of Transportation of the highway enterprise executives, the executive insisted that There is no problem with the design and construction of the Yichang Bridge, "the bridge is required not to withstand lateral, horizontal tension."
People who don't know about bridge structures also know that the shock waves created by the explosion were directed in all directions, and naturally there were horizontal forces rushing toward the bridge, and the general design of civilian bridges does not take into account the conditions of the explosion.
But the bridge design but had to consider seismic requirements. Earthquake loads are also three-dimensional direction, vertical and horizontal. Moreover, seismic design of bridges is mandatory in all countries of the world.
China's seismic design codes for highway bridges can be divided into three generations: the first generation of the Social Code for Seismic Resistance of Highway Engineering (1977 Code), which was implemented in 1977; the Code for Seismic Resistance of Highway Engineering (1989 Code), which has been in force since 1990; and the newest generation of the Rules for Seismic Resistance Design of Highway Engineering (2008 Rules), which is dated 2008.
The Ministry of Transportation issued the "1989 Code" in the 3.4.4 specification requirements, seismic structural body should have obvious calculation sketch and reasonable seismic action transfer route; reinforced concrete members should be a reasonable choice of size, configuration of reinforcing steel, to increase the ductility, to avoid the shear before the bending damage and reinforcing steel anchorage bonding before the member damage. Before the destruction of members, etc.. In addition, Article 10.5 specification lists the shear capacity calculated by the formula, just frame reinforced concrete piers horizontal capacity and allowable ductility coefficient.
The above professionals pointed out that the "ductility" refers to the tensile (horizontal) capacity of concrete members. Article 10.5 of the specification listed in the formula "horizontal force", is to rely on concrete, longitudinal reinforcement and hoop *** with the role of the meaning.
Professor Liu Jianxin, professor and doctoral supervisor of the bridge department of Chang'an University Highway School, pointed out in the article "Wenchuan Earthquake and Changes in Seismic Design Code for Highway Bridges in China" that "through the structural potential plastic stranded area of the configuration of the reinforcement bars (especially hoop reinforcement), to improve the degree of constraints on the core of the concrete to increase the structural capacity of plastic deformation and to ensure that structural bearing capacity. This design is called ductile design, which in essence is the exchange of increased structural displacement and stiffness reduction for lower seismic force input."
"The piers do not have or lack of hoops, either the design unit is sloppy on-site construction jerry-built, at least the ability to resist earthquakes did not meet the specification requirements." The above professionals pointed out.
Luosan Highway (Luoyang-Sanmenxia), where the Yichang Bridge is located, began construction in January 1998, and the 1989 specification, which was in effect at the time, had already set forth requirements for increased ductility.
Professor Liu Jianxin told the Times that according to the time of construction, the Yichang Bridge should be subject to the 1989 Code. The specification does not specifically provide for increased ductility, and only takes into account ductility in the coefficient, the concept and calculation formula is not clear. "(Although) there is no specific that, as a construction, there should be hoop reinforcement, not that one is not there, then it is not a bridge pier."
Based on the on-site pictures, Prof. Liu Jianxin said the hoop reinforcement of the bridge pier is not visible. But he said he could not make a strictly negative judgment. He emphasized that the basis for the judgment made would be more scientific and clearer if the fractured piers were dissected for inspection.
Compared with Professor Liu Jianxin, the above judgment of the industry is more clear: "photos show the fractured abutment, you can see that part of the rebar has been pulled out of the rebar and concrete contact cross-section is clearly visible, the cross-section is clearly visible in the case of the 80-centimeter-long bridge abutment, did not find the hoop bar, it is certainly there is a problem. "
The bridge breaks like a knife cut
"The shock wave caused by the explosion and earthquake level force is not the same, (explosion) force how to calculate, it is not easy to say." Liu Jianxin said, "The force of the explosion is blocked by the carriages, it should be toward the ling surface, upward to the left to the right forward and backward. And the energy of the earthquake is very large, an explosion should be no more than the destructive force of the earthquake."
It's easy to understand that the 2008 Wenchuan earthquake caused a large number of bridges to collapse in the quake zone. And January 14, 2009, Wuhu Yangtze River Bridge, 1 km section, a two-vehicle collision, a truck loaded with more than 6 tons of "skyrocket" fireworks produced an explosion and fire (Yichang Bridge fireworks vehicles containing more than 9 tons of Leizi gun), the vehicle was burned beyond recognition, but the bridge has not been damaged, the Wuhu Yangtze River Bridge, although it was once a temporary interrupted, but the same day it resumed traffic.
Liu Jianxin also pointed out that the Yichang Bridge belongs to the simply supported beam bridge, "in the abutment above the discontinuous, the bridge deck residual rebar, is the continuity of the bridge deck, rather than structurally and discontinuous, is not a structural rebar."
The above industry insiders also pointed out that the roadway is laid on the abutments of the concrete box girders or steel box girders, these box girders are to ensure that the roadway is leveled with, is not the main force structure. That is to say, in the case of horizontal displacement of the bridge deck he is not limit the role of.
"From the concrete box girder connection points remaining on the bridge deck, there are two problems: one is that the rebar is not anchored into the concrete box girder at a sufficient depth; and there is a problem with the nodes of the connection because the nodes seen in the photographs are completely destroyed, and the rebar is being pulled straight out." He explained the depth of the rebar anchored into the concrete should be 45 times the diameter of the rebar, "According to the code, the rebar should be exposed a little longer. There are curved hooks on the head of the rebar, so if the vertical depth is not deep enough, horizontal depth is fine. But I suspect the anchors were not deep enough to make an effective connection to the concrete steel beam."
"The collapsed pavement, which didn't move too much horizontally, suggests that it was the piers that collapsed first due to insufficient reinforcement, causing a kind of chain reaction, with the concrete box girders going down after them." The source pointed out.
"If there is enough reinforcement, the local concrete steel box girder cracks or collapses, but does not collapse instantly. Such an example is really rare, the bridge accident is basically seven twisted more, and the Yichang Bridge accident is equivalent to this section of the bridge is basically no more, the fracture of the bridge is very flat, in engineering terms, basically a knife cut." The source told reporters.
The unspeakable responsible
Yichang Bridge is located in the Luo three high-speed in January 1998 to start construction, the planned construction period of 46 months, the design estimate of 4.29 billion yuan. According to a publicity material at the time, Luo three high-speed is Henan's second batch of World Bank loans to build key transportation projects, at that time is Henan highway construction history of the largest one-time investment, the most complex geological terrain, the construction of the most difficult project.
The road is 135.549 kilometers long, the project is divided into eight contract sections, in November 1998, Henan Provincial Department of Transportation and Henan Provincial Highway Management Bureau set up the establishment of Luoyang to Sanmenxia Expressway Construction Front Command (hereinafter referred to as the Luosan Command), on behalf of the former to undertake the Luosan high-speed construction project duties and tasks. Upon completion, the highway assets belong to Henan Provincial Highway Development Limited Liability Company (hereinafter referred to as Henan Gaofa).
The media had pointed out that the construction unit of Luosan Expressway is Luosan Command, but in fact, Luosan Command should be the construction unit.
The Times reporter asked the Henan Provincial Department of Transportation and the publicity department of Henan Gaofa Company for confirmation, and the other party did not disclose the specific location of the contract section. According to the publicity materials mentioned above, the eight contract sections start from Luoyang city center and are arranged in order from east to west. The scope of the first contract section is the suburb of Luoyang to Mengjin County section, by the then Ministry of Transportation First Engineering Bureau a construction.
Mengjin is further eastward, with Xin'an, eastern Mianchi, Yima and western Mianchi in that order, to Sanmenxia City. The second contract section will be undertaken by the Third Division of the Highway Engineering Bureau of Henan Province and the Fifteenth Bureau of China Railway*** together; the third contract section will be undertaken by the Sixth Division of the Third Bureau of China Railway, whose project manager is Wu Zhandong; and the fourth contract section will be undertaken by the First Division of the Eleventh Bureau of China Railway, whose project manager is Jia Qiyou.
The Xu Gou Special Bridge of the fourth contract section, which was honored with the "Luban" award, is in Mianchi. According to the judgment, the specific constructor of the Yichang Bridge is not out of the construction units of the second to fourth contract sections.
Shi Fa-liang, then director of the Henan Provincial Transportation Department, wrote in the preface to this publicity material: "The entire line of participants overcame ...... many difficulties, carried forward the spirit of unity and pragmatism, integrity and efficiency, and selfless dedication, and successfully accomplished the construction tasks assigned by the provincial government and the Department of Transportation," he said. ...... in the Ministry of Transportation, the provincial Department of Transportation organized by the successive quality inspection have been praised ......"
December 2001, Luosan high-speed open to traffic. A year later in December 2002, Shi Faliang was "double regulation", 2006 was sentenced to life imprisonment, becoming the third director of the Henan Provincial Department of Transportation was sentenced. (Source: Time Weekly)