Structural Style Design And Analysis On Reliability Of Cable Barrier In Cold Area

It was reported that the direct property losses caused by traffic accidents has been up to 1.88 billion in China in 2005. One third of the fatal accidents occurred in the road-side collision of single accident annually. Also, it is on the rise. For the traffic accidents that rushing out of the road and driving into the oppositely directed lanes, the installation of crash barriers is one of the irreplaceable and the most effective measures.Based on the relevant literatures, the paper establishes a simplified calculation model of cable barrier and derives relevant formula. Also, the corresponding program is work out using Visual Fortran 6. The reliability analysis of flexible barrier performance is made by changing the initial tension of cable, distance from the ground, material of middle post and the friction factor between bracket and cable. Then the design project is brought forward. The paper includes five chapters. And chapter three and chapter four are the emphasis part in the paper.Chapter 1 mainly talks about the study background, study method and study content. As one of effective preventive measures, the setting up of traffic crash barrier reasonably can prevent moving vehicles running off the road or into the opposite lane and reduce traffic accidents and its severity. In addition, it can also induce sightline to comfort the driver and passengers and reduce their fatigue. Britain, the United States and Japan have been engaged in flexible barrier trials and research work. But there is lacks of the responding research work in our country. So the paper brings forward the main study content by comparing the method of crash between the vehicles and rash barriers.Chapter 2 introduces the barrier sorts, evaluation criteria and design conditions of barriers. According to the stress of characteristics, barriers can be sorted into rigid barrier, semi-rigid barrier and flexible barrier. Cable barrier is the main representatives of flexible barrier. To determine what performance the barriers up to can be called "good" involves biomechanics, ergonomics, traffic accident statistics, facilities engineering and many other disciplines. From the angle of function, the barrier must have considerable mechanical strength and rigidity to withstand the vehicle collision to prevent more vehicles running out of the road(bridge);Meanwhile, the rigidity can not be too much, so that the passenger can be well protected from harm or mitigated the damage. Obviously, these two requirements are contradictory. And this brings difficult to crash barrier design. To resolve the "contradictory" depends on the three design conditions: vehicle mass, impact velocity, impact angle.Chapter 3 mainly establishes a simplified mechanical model and relevant formula are derived according to the features of cable barriers. Cable barrier consists of initial tension cables fixed on a series posts,which depends on the cable to resist the collision vehicle by cable and absorb the collision energy. It has lots of advantages such as strong adaptability, security, construction convenience, the maintenance convenience and so on. According to the principle of the interaction of vehicle collisions with the barriers, a vehicle collision with the cable barrier on the assumption certain conditions, establishes a simplified mechanical model, the calculation formula are derived.Based on the former formula, Chapter 4 works out the relevant program using Visual Fortran. The influence to the flexible barrier performance is analyzed by changing the parameters. And the corresponding design project is proposed.Finally, the analysis on reliability of the design is made. The observation is carried out on the flexible barrier which installs in Dehui -Nong'an connection. The temperature coefficient of the cable tensile stress can be calculated. Cable initial tension directly affects the anti-crash performance and safety. And the temperature changes also have some impact on the cable tensile stress. The reasonable range of the initial tension is 30KN~50KN in the northern by appropriate calculation using the program mentioned above.Through analyzing the affection of the ground clearance of cable barrier and the proportion of vehicles on the flexible barrier, this chapter proposes the ground clearance of cable barrier is respectively 0.35m,0.48m,0.66m,0.79m,0.92m.It is found that the influence of the material and the distance between middle post on the energy distribution is quite small. But it has some impaction on the maximum tensile stress. The smaller is the distance between middle posts, the higher is the yield stress. The maximum tensile stress is bigger. So it should be chosen reasonably according to the practical situation.The distance between middle posts is 6m and material is Q235 in the paper. In addition, during the course of the cars and the flexibility barrier collision, the proportion of energy wasted due to friction is smaller. But lot of energy is consumed by cables. By changing the block contact form of engagement, Cable's effect can be fully played in order to improve the protective effects of flexibility barriers.Finally, the reliability analysis of flexible barrier is conducted. End part is the main resisting force components of flexible barrier. Once it is damaged, the whole flexible barriers will be ineffective. Otherwise, the repair is very difficult. Therefore, the end post should have high safety factor. By calculating collisions of different condition, the end post safety factor is greater than 1.76 and cable's is1.58. The most dynamic deformation and the lateral acceleration completely satisfy the specification. The design is reasonable.Chapter 5 is the conclusion of the paper. Also, the problem to be resolved is pointed out.