The Study On Mechanical Properties Of Plate Natural Rubber Bearings Under The Conditions Of Erosion Environments

The plate natural rubber bearing which is a combination of rubber and steel plate is important force bearing and seismic vibration device for Highway Bridges. It is widely used in our country in the past 20 years, and its quality and work stress directly affect the bearing on the role, function, safety, reliability and service life. According to the survey, rubber bearings of almost every highway have some degree of degradation, and their use life is far lower than the design life even broken badly before the opening for traffic, since the products standard JT/T4-93 and corresponding specifications were promulgated. The factors influencing the quality are in many aspects. Construction quality, production process, selection of raw materials (rubber, filler and the like) quality, bridge design (including the design and selection of bearings) are always considered.Under the trend of rubber bearing is widely applied, its performance directly affects our daily life and the safety of life and property. This paper considers the main environmental factors, including hot and humid environment, acid rain environment (including nitric acid rain, sulfate type acid rain and sulfur nitrate mixed acid rain), freeze thawing, salt freezing environment and thermal aging environment etc. and studies on the change of rubber bearings in mechanical properties and durability under a separate action of various environmental factors. Its purpose is to improve the condition assessment process of rubber bearings, and to develop new technology assessment standards as the basis for inspection and testing of rubber bearings for Highway Bridges.For the study of the stress characteristics and performance change of plate natural rubber bearings in hot and humid environment, the specimen are dealt in high-low alternating heat chamber for 20,40,60,80 and 100d,then compressed axially and sheared horizontally. Its changes of the mechanical properties can be studied from ultimate compressive strength, ultimate shearing strength, compressive elastic modulus, shearing elastic modulus, vertical stiffness, level equivalent stiffness etc. The attenuation model of natural rubber bearings created by the least square method can be used to derived the fitting curve and the attenuation function in order to estimate roughly the effects which environmental factors have on the mechanical properties of rubber bearings.For the study of the stress characteristics and performance change of plate natural rubber bearings in acid rain environment, the specimen are immersed in a certain concentration of nitric acid, sulfuric acid solution and the 1:1 volume ratio of mixed solution of sulphate nitrate for 20, 40,60,80 and 100d.then compressed axially and sheared horizontally. Its changes of the mechanical properties can be studied from ultimate compressive strength, ultimate shearing strength, compressive elastic modulus, shearing elastic modulus, vertical stiffness, level equivalent stiffness etc. The attenuation model of natural rubber bearings created by the least square method can be used to derived the fitting curve and the attenuation function in order to estimate roughly the effects which environmental factors have on the mechanical properties of rubber bearings.For the study of the stress characteristics and performance change of plate natural rubber bearings in alternate freezing and thawing environment, the specimen are dealt in standard test box of freezing and thawing for 25,50,75,100 and 150 times freeze-thaw cycle, then compressed axially and sheared horizontally. Its changes of the mechanical properties can be studied from ultimate compressive strength, ultimate shearing strength, compressive elastic modulus, shearing elastic modulus, vertical stiffness, level equivalent stiffness etc. The attenuation model of natural rubber bearings created by the least square method can be used to derived the fitting curve and the attenuation function in order to estimate roughly the effects which environmental factors have on the mechanical properties of rubber bearings.For the study of the stress characteristics and performance change of plate natural rubber bearings in salt freezing environment, the specimen are soaked in a concentration of 3% NaCl solution, and dealt in high-low alternating chamber for 20,40,60,80 and 100d,then compressed axially and sheared horizontally. Its changes of the mechanical properties can be studied from ultimate compressive strength, ultimate shearing strength, compressive elastic modulus, shearing elastic modulus, vertical stiffness, level equivalent stiffness etc. The attenuation model of natural rubber bearings created by the least square method can be used to derived the fitting curve and the attenuation function in order to estimate roughly the effects which environmental factors have on the mechanical properties of rubber bearings.