Statistical calibration of federal highway administration simplified models for facing tensile forces of soil nail walls

This study first develops a database containing 56 measured facing tensile forces from instrumented soil nail walls during or at completion of construction. Based on the compiled database, the accuracies of both default and modified federal highway administration (FHWA) simplified models for estimation of short-term facing tensile forces are evaluated. Here, accuracy is defined by the model bias computed as the ratio of measured to predicted facing tensile force. The analysis results show that predictions are highly conservative and highly dispersive using the default model, and moderately conservative and medium dispersive using the modified model. Moreover, the prediction accuracy is statistically correlated with magnitudes of the computed facing tensile forces and several model input parameters. An out-of-sample approach is used to develop and validate a recalibrated FHWA model which is then demonstrated to have least empirical constants but best accuracy compared to the default and modified models. The biases for the three models are characterized as lognormal random variables. An example of reliability-based analysis for facing flexure limit state is illustrated to both elaborate the application and highlight the benefit of using the recalibrated model for design practice from the perspective of cost-effectiveness.

     

结合物联网与云技术的测绘实训管理平台设计与实现

测绘实训管理平台是针对测绘类专业实训课程,以移动互联网、物联网环境为基础,构建面向移动教学环境和自主学习服务的实训教学支撑平台。平台以测绘类专业实训教学任务的规划、组织、实施和监督管理为核心,涵盖多种形式实训教学资源的集成、共享与分发过程,通过测绘仪器设备数据的实时读取,做到实训任务可管理、可量化、可评价,可以帮助任课教师持续改进实训课程教学方式,优化教学过程、提升教学效果、降低劳动强度。本文首先分析了目前高职院校实训教学的基本现状,并介绍了移动互联时代教学的技术特点,进而介绍了测绘实训管理平台的设计思路与实现方法。平台的设计和研究也对实际生产中移动互联与云技术的应用具有借鉴意义。