The Study On Moisture Damage Of Steel Bridge Deck Pavement

Moisture damage is one of the early disease model of typical steel bridge deck pavement,a lot of steel bridge deck pavement in China in the early have appeared different degree of moisture damage,hot and humid and rainy areas of steel bridge deck pavement moisture damage phenomenon is particularly serious,take off a layer of pavement,cracks and potholes,beat,loose diseases such as serious influence driving safety and comfort,reduce the service life of pavement,even aggravate the orthotropic bridge deck system of steel plate and weld early to produce local cracking.The moisture damage of steel bridge deck pavement is closely related to the dynamic water pressure under the action of driving load,and is also closely related to the structural characteristics of orthotropic steel bridge deck system.It is of great significance to grasp the action mechanism and main influencing factors for preventing such diseases.Based on the basic theories of seepage consolidation and fracture mechanics,this paper establishes the mechanical model of moisture damage of steel bridge deck pavement,studies and identifies the main factors of moisture damage of steel bridge deck pavement based on laboratory test and engineering observation.On this basis,combined with recent domestic practice,this paper proposes the measures to prevent moisture damage of steel bridge deck pavement.First of all,based on the basic theory of Boit seepage consolidation,the steel bridge deck pavement of asphalt concrete as elastic porous media system,using ABAQUS finite element is adopted to establish the model of orthotropic steel bridge deck pavement system,analyzed the driving load,speed,the permeability coefficient of pavement and elastic modulus of pavement layer of the influence of pore water pressure distribution.The results show that under the action of traffic load,the pavement layer will produce positive pore water pressure first,and then pump suction with vacuum negative pressure,which will accelerate the damage of pavement layer under repeated action.When the driving speed and load were kept at 60km/h and 0.7MPa respectively,and the temperature was increased from 5°C to 35°C,the maximum pore water pressure of the pavement layer correspondingly increased from 155.88 k Pa to 436.88 kpa,nearly three times of the original.The maintaining temperature and acting load were 25°C and 0.7MPa respectively,the driving speed increased from 40km/h to 120km/h,and the maximum pore water pressure of the pavement increased from 234.22 k Pa to 393.03 k Pa,1.7 times of the original.The maintaining temperature and driving speed were 25°C and 60km/h respectively,the acting load increased from 0.5MPa to1.1MPa,and the maximum pore water pressure of the pavement increased from 202.17 k Pa to444.69 k Pa.Therefore,high temperature,heavy load and high speed will aggravate the hydrodynamic pressure.Secondly,based on the theory of elastic fracture mechanics and finite element software ABAQUS is adopted to establish the zone extended finite element method(XFEM)model of crack of the orthotropic steel bridge deck pavement,analyzes the dynamic water pressure caused by vehicle load effect on the crack tip J integral,and the axle load and young’s modulus of pavement materials,quantity and depth of a crack on the influence law of crack tip J integral,and the crack extension in the quantitative study of pavement.When the crack depth increases from 1cm to 4cm,the J integral at the crack tip has little change under the same hydrodynamic pressure.When the crack depth and hydrodynamic pressure are 3cm and 0.4MPa respectively,the crack length increases from 2cm to 20 cm,and the J integral of the crack tip gradually increases from 0.701N/m to 2.301N/m.It can be seen that the crack length has a great influence on the J integral of the crack tip.When the length and depth of the fracture were 20 cm and 3cm respectively,1,2,3 and 4 cracks were preset at the same spacing.The results showed that when the hydrodynamic pressure was the same,the variation range of the J integral value was not more than 15%,and the number of cracks had little influence on the J integral of the fracture tip.When the pavement temperature is changed from 5°C to 30°C,the length and depth of the fracture remain 20 cm and 3cm,respectively.The J integral value changes a lot.When the hydrodynamic pressure is 0.4MPa,the J integral value corresponding to 5 ° C is 0.61N/m,and the J integral value corresponding to 30 ° C is 2.94N/m,an increase of nearly 400%.Therefore,temperature has a great impact on the fracture expansion.Then,in view of the steel bridge deck surfacing,early bubble disease more common is based on the first-order shear deformation plate theory,simplifying the steel bridge deck surfacing bubble expand to interface crack propagation process,the virtual crack closure technique is adopted to establish the pavement bubble model,will beat cutting-edge energy rate as an index of bubble expand,analyzed the diameter,load size,the thickness of the surfacing layer thickness ratio and elastic modulus on the influence of the energy release rate bubble tip.When the elastic modulus of pavement and the load at the bubble are 3900 MPa and 0.4MPa respectively,the thickness of pavement is 0.05 m,the diameter thickness ratio(the radius of bubble/the thickness of pavement)increases from 1 to 5,and the energy release rate also increases from 0.96 J /m2 to 130.03 J /m2.When the radius of the bubble is 0.1m and other parameters remain unchanged,the thickness of the pavement layer increases from 0.04 m to 0.08 m,and the energy release rate also decreases from10.12 J /m2 to 3.01 J /m2.When the radius of the bubble and the thickness of the pavement layer are0.1m and 0.05 m respectively,the load at the bubble increases from 0.2MPa to 0.8MPa,and the energy release rate also increases from 0.32J/m2 to 23.24J/m2.The elastic modulus of the pavement increased from 1GPa to 5GPa,and the energy release rate also decreased from 18.74J/m2 to4.02J/m2,while the radius of the bubble,the thickness of the pavement and the vertical uniform distribution load remained unchanged.Therefore,the heavy load,high temperature and so on will accelerate the expansion of the bubble,and the pavement layer is thinner and relatively large diameter thickness will also accelerate the expansion of the bubble.Finally,according to the research results and domestic engineering practice,the Suggestions and engineering measures to prevent moisture damage of steel bridge deck pavement are put forward.