环氧树脂-混凝土叠合结构的热应力分析

Analysis on Thermal Stresses in Epoxy-concrete Laminated Structure

为解决环氧树脂-混凝土叠合结构在温度变化时因两种材料变形不协调而造成结构破坏的问题,进行了环氧树脂-混凝土叠合结构的热应力研究,对结构在环氧树脂固化阶段、养护阶段、后固化阶段和使用阶段进行应力分析,提出各阶段环氧树脂中存在的热应力有收缩应力、固化应力、后固化应力和温度应力,给出了这些应力的计算公式,并进行了有限元计算和试验验证,结果表明:(1)从环氧树脂浇注到混凝土上那一刻开始,就会由于树脂的固化反应、以及温度的变化而在体系内部产生应力,主要包含收缩应力、固化应力、后固化应力、温度应力;(2)较小的弹性模量能有效降低环氧树脂-混凝土叠合结构的固化应力、后固化应力和温度应力,但常温下表现为低弹性模量的环氧树脂在低温时其弹性模量会急剧上升,有时会增加几十倍,大大增加了低温时的温度应力;(3)常温养护时,高温后固化的环氧树脂-混凝土叠合结构的内应力变化比较复杂,因高温后固化会降低环氧树脂的线性热膨胀系数,增加其弹性模量以及热变形温度,同时也会产生固化收缩,最终应力累积的计算需要大量试验数据;(4)环氧树脂最大平均弹性模量为131.9 MPa(20℃至-20℃的平均弹性模量,环氧树脂线胀系数取100×10^(-6)(m·m^(-1))/℃)时,可通过ASTM C884中相容性试验测试。

When epoxy-concrete laminated structure is subjected to a temperature change, thermal stress induced by the inconsistency of the deformation of epoxy and concrete would cause failure of the structure. To solve this problem, the formulas of thermal stresses in epoxy-concrete laminated structure is studied, the shrinkage stress, curing stress, post-curing stress and temperature stress are proposed based on the analysis of thermal stresses in epoxy-concrete laminated structure at curing stage, post-curing stage, and service stage, which are verified by FE analysis and experiments. The result indicates （ 1 ） due to curing shrinkage of epoxy and temperature changing, the stresses such as shrinkage stress, curing stress, post-curing stress and temperature stress occurred in the epoxy-concrete laminated structure once epoxy is cast on concrete ; （2） lower elastic modulus of epoxy will significantly reduce the curing stress, post-curing stress and temperature stress of epoxy-concrete laminated structure, but the lower elastic modulus of the epoxy tested at room temperature will sharply increase at low temperature, sometimes increase dozens of times, which will remarkably increase the temperature stress at low temperature; （3） when the cure stage is in room temperature, the changing of inner stress of the cured epoxy-concrete laminated structure after heating is complicated due to that post-curing in high temperature will reduce the thermal expansion coefficient of epoxy resin, enlarge the elastic modulus, Heat deflection temperature and curing shrinkage, which needs a mass of experiment data to achieve calculation of stress accumulation; （4） the epoxy resin will pass the compatibility test of ASTM C884 when the average elastic modulus of epoxy is less than 131.9 MPa （tested from 20 ℃ to -20℃ , the linear expansion coefficient of epoxy is set as 100 × 10-6（m· m-1 ）/℃）.