加载龄期及湿度对混凝土收缩徐变影响比较分析

Comparative Analysis of the Effect on Shrinkage and Creep of Concrete Due to Loading Age & Humidity

对《公路钢筋混凝土及预应力混凝土桥涵设计规范》(JTJ 023-85)和(JTGD62-2004)《铁路桥涵钢筋混凝土及预应力混凝土桥涵设计规范》99年版和2005年版、ASSHTO-1994规范中在相同条件下,通过不同的加载龄期、不同的环境相对湿度等其中一个参数变化时对各规范收缩应变、徐变系数进行分析和比较。主要结论为:混凝土收缩应变主要与环境的相对湿度有关;混凝土的徐变系数,各规范相差较大,铁路规范中徐变系数仅与加载龄期有关,与混凝土的所处相对湿度无关,且其徐变系数相差不大;公路规范中加载龄期及湿度均对其有影响,但湿度对混凝土徐变系数影响更为敏感;在设计和施工中尤其是混凝土前期养护时的湿度应重点关注。综合分析表明,JTGD62-2004考虑参数较多、较为合理,建议铁路规范进行适当调整。

Taking one parameter variation between different loading time and different environmental relative humidity which are coming from reinforced and pre-stressed cement concrete design of high-way bridge （JTJ 023-85 ）and （JTG D62-2004）,pre-stressed and reinforced cement concrete design of railway bridge published in 1999 and 2005,AASHTO 1994 into consideration,shrinkage strain and creep coefficient of cement concrete according to different design specification are analyzed and com-pared.Some conclusions can be gained as follows：shrinkage strain of cement concrete is mainly asso-ciated with the relative humidity of environment;creep coefficient of cement concrete changes greatly according to different designing specification,creep coefficient of cement concrete which is only related to loading time and not relevant to relative humidity has a little change in railway specification;but creep coefficient is sensitive to humidity which is influenced by loading time and humidity in highway specification.So,humidity factor should be paid more attention for cement concrete maintenance dur-ing process of design and construction.The shrinkage strain and creep coefficient of cement concrete is comparatively reasonable in highway specification because more parameters are considered and there is a need of some appropriate adjustment in railway specification.