大跨径混凝土箱梁桥有效温度与应变的实测分析

基于苏通大桥辅助航道桥运营期两年内实测的温度、气象和应变数据,对混凝土箱梁的有效温度与应变进行了分析。结果表明:箱梁的尺寸越小,有效温度变化的范围越大,设计基准期为100年的墩顶梁和跨中箱梁的有效温度范围分别为(-4.3℃,37.3℃)和(-6.1℃,42.2℃);大气前3天的最高(低)平均温度与箱梁有效温度的相关性系数高达0.97,通过回归分析得到的箱梁有效温度与大气前3天平均最高(低)温度的关系式,可用来对箱梁有效温度进行预测。最后提出了修正混凝土收缩、徐变效应的方法,并使用箱梁有效温度对主墩墩底混凝土的竖向相对应变和支座截面箱梁顶板混凝土的纵向相对应变进行了预测。     

盐城市沿海大规模滩涂开发利用评估

利用遥感技术并通过多渠道信息对照分析得到盐城市规划阶段内的岸线变化,结合实地调研、专家咨询等对垦区的空间布局、用地功能定位、滩涂资源持续供应能力、生态环境保护以及综合试验区建设等方面进行评估。结果表明:盐城市滩涂开发匡围进展总体偏慢,应根据工程区域的自然条件变化、地方的经济发展需求等对下一阶段的开发进行局部调整;盐城市可开发的滩涂资源量仍有较大剩余,基础设施建设总体上与垦区的开发进展相协调,可持续开发能力较强;大规模滩涂开发利用将对水沙动力条件、海洋生态环境等多方面产生影响,应针对江苏沿海环境特征,建立围垦环境影响的综合评价体系,为今后滩涂的可持续开发利用提供依据。     

Temperature gradients in concrete box girder bridge under effect of cold wave简

The temperature distributions of a prestressed concrete box girder bridge under the effect of cold wave processes were analyzed. The distributions were found different from those under the effect of solar radiation or nighttime radiation cooling and should not be simplified as one dimensional. A temperature predicting model that can accurately predict temperatures over the cross section of the concrete box girder was developed. On the basis of the analytical model, a two-dimensional temperature gradient model was proposed and a parametric study that considered meteorological factors was performed. The results of sensitivity analysis show that the cold wave with shorter duration and more severe temperature drop may cause more unfavorable influences on the concrete box girder bridge. Finally, the unrestrained linear curvatures, self-equilibrating stresses and bending stresses when considering the frame action of the cross section, were derived from the proposed temperature gradient model and current code provisions, respectively. Then, a comparison was made between the value calculated against proposed model and several current specifications. The results show that the cold wave may cause more unfavorable effect on the concrete box girder bridge, especially on the large concrete box girder bridge. Therefore, it is necessary to consider the thermal effect caused by cold wave during the design stage.