| Plate rubber bearing of highway bridge is superposed in multi-layer rubber which uniform distribution and steel plate, and it is an important bearing and vibration device, the bearing function, the security and reliability of the structure, and the life of service are impacted in the quality, and its anti-friction performance is better, at the same time, it has the advantages of simple structure, easy to replace, buffer isolation, and the building height is low. The plain chloroprene rubber bearings are belonging to the normal temperature rubber bearing, and its suitable temperature is from-25to60. The plain chloroprene rubber bearing is an universal bearing, except the good physical properties of general rubber bearings, it has the advantages of weather resistance, flame retardant, oil resistance, chemical corrosion and other outstanding features. The heat resistance of plain chloroprene rubber is better to natural rubber and styrene-butadiene rubber, it can be used at the temperature of150in Short term, and it can be used at the temperature from90to110in4months. The life will reduce at50percent with the operating temperature reduce10. At the same time, the aging resistance of plain chloroprene rubber bearings is better, because of the role of the heat, light, and oxygen, the oxidation and decomposition will gradually appear, and the physical and mechanical properties will deline after the long using. It is easier to produce crystallization in the low temperature.China is in the temperate regions of the Northern Hemisphere, the climate characteristics are obvious. The four seasons are obvious in Northeast China, North China and Northwest China (except Qinghai), the temperature in winter is low and the temperature in summer is high. Based on the climate extremes data of military equipment, the average annual freeze-thaw cycle days is generally from60to130days in Northeast China, North China and Northwest China (except Qinghai), the temperature difference between day and night is about12in winter, this require the performance of plain chloroprene rubber bearings is better. But in summer, based on the date of "Climatic Data Center online" of the National Meteorological Center, the average temperature in summer is about25in these areas, higher performance of plain chloroprene rubber bearings is demanded in this climate of high temperature. At the same time, due to the the installation location and performance requirements of rubber bearings of the highway bridge, the impact of climate is more serious to highway bridge rubber bearings than to building rubber bearings. There are a lot of studies on the durability of rubber bearings at domestic and international, the studies on durability of plain chloroprene rubber bearings in the freeze-thaw cycle and thermal aging conditions have to be perfected from domestic and foreign research status. Therefore, the studies on the mechanical properties of plain chloroprene rubber bearings are conducted, and the studies provide a basis for the construction of the highway bridge. The main contents of the study are as follows:In order to investigate the changes of the mechanical properties of plain chloroprene rubber bearings of highway bridge in climate changes at low temperature, the changes of low-temperature climate were simulated by using standard freeze-thaw chamber, the plain chloroprene rubber bearings were processed25.50.75.100times. then the axial compression tests were carried. The impact of the carrying capacity, ultimate compressive strength, vertical stiffness, elastic modulus of compression of plain chloroprene rubber bearings of highway bridge under freeze-thaw cycle condition was studied through the contrastive analysis. The results showed that, the plain chloroprene rubber bearings were easier to brittle failure under freeze-thaw cycle than the standard sample, the phenomenon which plate exposure, cracks and layered damage was more serious. With deepening of degree in freeze-thaw cycle, the carrying capacity, ultimate compressive strength, vertical stiffness, elastic modulus of compression of the plain chloroprene rubber bearings were decreasing. It was analysed by the least square method which the changes of its compressive strength and comprcssive modulus, and the attenuation curve and attenuation function of50years were gived. It was basically in line with variation of power function which the law of compressive strength and compressive modulus. And it was greater impacted which the thickness was thinner of plain chloroprene rubber bearings.In order to investigate the mechanical properties of plain chloroprene rubber bearings of highway bridge in the condition of climate changes at low temperature, the shear tests were carried of the plain chloroprene rubber bearings of freeze-thaw cycles, study the variation of the shear capacity, shear strength, horizontal equivalent stiffness and elastic modulus of shear. The results showed that, compared with the standard test pieces, the plain chloroprene rubber bearings were easier to failure under freeze-thaw cycle, the cracks were larger, the partial was seriously damaged, shear failure were obvious. With deepening of degree in freeze-thaw cycle, the shear capacity, ultimate shear strength, horizontal equivalent stiffness, elastic modulus of shear of the plain chloroprene rubber bearings were decreasing. It was analysed by the least square method which the changes of its shear strength and shear modulus of50years, and the attenuation curve and attenuation function basically in line with the power function variation. and fitted well with the actual situation. In the same conditions of the freeze-thaw cycle, the various mechanical properties were better which the thickness was thicker of plain chloroprene rubber bearings, proposed using the thick specimens in the cold regions.In order to investigate the changes of the mechanical properties of plain chloroprene rubber bearings of highway bridge in climate changes at high temperature, the thermal aging process was simulated by using the high temperature chamber, the plain chloroprene rubber bearings were processed in20,40,60,80days by high-temperature chamber, then the axial compression tests were carried. The impact of carrying capacity, ultimate compressive strength, vertical stiffness, elastic modulus of compression of plain chloroprene rubber bearings under thermal aging condition was studied. The results showed that, under thermal aging, the plain chloroprene rubber bearings was easier to brittle failure, the phenomenon of damage was more serious. With deepening of degree in thermal aging, the carrying capacity, ultimate compressive strength, vertical stiffness, elastic modulus of compression were decreasing. It was analysed by the least square method which the changes of its compressive strength and compressive modulus of50years, and the attenuation curve and attenuation function were gived, it was basically in line with variation of power function which the law of compressive strength and compressive modulus. And it fitted better with the actual situation. And it was greater impacted which the shape parameter was smaller of plain chloroprene rubber bearings.In order to investigate the mechanical properties of plain chloroprene rubber bearings of highway bridge in the condition of climate changes at high temperature, the shear tests were carried with the specimen which were processed by thermal aging, the impact of shear capacity, shear strength, horizontal equivalent stiffness, elastic modulus of shear of plain chloroprene rubber bearings under thermal aging condition was studied. The results showed that, compared with the standard test pieces. the shear failure phenomenon of the specimens which processed by thermal aging was more serious, and the partial destruction was larger, the cracks were longer and wider. With deepening of degree in thermal aging, the shear capacity, ultimate shear strength, horizontal equivalent stiffnessand elastic modulus of shear were decreasing. It was analysed which the changes of its shear strength and shear modulus of50years, the shear strength and shear modulus were fitted by the least square method, the attenuation curve and attenuation function were basically in line with variation of power function, and were fitting better with actual. And in the same condition of the thermal aging, the mechanical properties were better which specimens with the bigger shape parameter. |
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