The Study Of Cracks Influence On The Bridges Structure Durability In Northwest China

The northwest region of China is located in the abdomen of the mainland.Because of the climatic features such as scarce precipitation,large temperature changes,low relative humidity,strong ultraviolet rays,and large winds,special natural climate conditions such as freeze-thaw cycles,alternating hot and cold wet and dry weather,and wind erosion are formed.This kind of environment is a great test for the service life of the bridge structure.Most of the bridge structures in the northwest region are far from the actual design life,and they will fail due to severe degradation of the durability.Based on the research results of the durability of bridge structure at home and abroad,this dissertation conducts an on-site inspection of the bridge structure in Gansu Province in Northwest China,analyzes the causes of the cracking,and explores the mechanism of the durability of the bridge structure in service.The main work of this paper is as follows:(1)This dissertation focuses on the specific geography and climatic environment in Northwest China and combines the field survey of the bridge to analyze the mechanism of crack generation and the impact on the durability performance of the bridge structure.(2)The presence of concrete cracks shortens the path of carbon dioxide and water transport to the interior of the concrete,accelerating the derusting of the steel bars in the cracking zone.In this thesis,the finite element software ANSYS was used to analyze the effect of cracks on the carbonization of concrete,and the effect of cracks on the durability of the bridge structure was recognized.(3)Combined with the ?Design specification for highway reinforced concrete and prestressed concrete bridge?JTG D62-2012 and?Specification for concrete structure design?GB 50010-2010.Taking the bridge(upper line)as an example,this paper introduces the crack indicator B by using the hierarchy method,and calculates the influence of concrete cracking on the bearing capacity of the bridge structure.(4)Based on reliability theory and durability performance indicators of bridge structures.Taking the Beidaihe Bridge as an example,the Monte Carlo method is used to calculate its reliability index.Then analyze the impact of cracks on the durability of the bridge structure.(5)Taking the special climate environment in the northwest region as the background,the mechanism of the cracking of the bridge structure in the northwest region was analyzed from three aspects of frost damage,salt damage and concrete neutralization,and appropriate preventive measures were proposed accordingly.Finally,a reinforcement technology is proposed for cracks in bridge structures in Northwest China,and the reinforcement effect is calculated and analyzed using finite element ANSYS.