Model for analysis of fiber-reinforced clayey soil

Fiber-reinforced soils have many applications in improving the response of clayey soils. In this paper, an analytical model for the analysis of fiber-reinforced soil in the framework of modified cam clay model is presented. The analytical model is verified using experimental results from the standard undrained triaxial tests with pore water pressure measurements. Tests have been conducted on clayey soil specimens reinforced with randomly oriented discrete coir fibers with different percentages of fiber contents. Numerical simulations of triaxial compression tests on fiber-reinforced clay specimens were also performed. Results are presented in the form of stress vs. strain curves for plain soil as well as fiber-reinforced soil for various fiber contents based on the model developed. The results demonstrate the applicability of proposed analytical model in predicting the stress strain response of fiber-reinforced soils.     

光纤光栅技术在工程变形监测中的应用

介绍了光纤光栅技术在工程变形监测中的应用,简述了光纤光栅监测的技术原理及光纤光栅的制作方法。     

Improved Removal of Indoor Volatile Organic Compounds by Activated Carbon Fiber Filters Calcined with Copper Oxide Catalyst

Heating, ventilating, and air‐conditioning (HVAC) systems ensure indoor air quality and provide a comfortable environment. However, the conventional HVAC systems only provide indoor ventilation and adjust temperature and humidity. This work removes indoor volatile organic compounds (VOCs) using a feasible and novel air‐cleaning for an HVAC system, to remove indoor VOCs. An activated carbon‐fiber (ACF) filter calcined with copper oxide (CuO) catalyst, called a CuO/ACF catalyst filter, was the developed kit. Formaldehyde, a major VOC, was chosen as the target pollutant. Experiments were performed to confirm the filtration ability of the CuO/ACF catalyst filter in removing formaldehyde in a stainless‐steel chamber equipped with a simplified HVAC system. Total air exchange rate (ACH) was controlled at 0.5 and 1.0 h⁻¹, the fresh ACH was 0.15 and 0.30 h⁻¹, and relative humidity (RH) was set at 30 and 70%. A first‐order decay of formaldehyde existed in the controlled chamber when the two pretreated CuO/ACF catalyst filters were employed. Experimental results demonstrate that the CuO/ACF catalyst filters removed formaldehyde effectively. The decay constant was 0.425 and 0.618 h⁻¹ for 0.5 and 2.0 ppm formaldehyde, respectively. Moreover, the formaldehyde decay rate increased as total ACH, fresh ACH, RH, and the Cu(NO₃)₂ concentration for calcination of CuO/ACF catalyst filter increased.     

基于GIS的岩溶塌陷分布式光纤监测系统的研发

结合某地区的岩溶塌陷分布式光纤监测的工程实例,开发出一套基于GIS技术的分布式光纤监测数据管理系统。该系统具有监测数据自动入库、监测数据可视化、监测信息查询与对比、监测点实时预警等功能,是一套集智能化分析与决策化管理为一体的多功能管理系统。     

光纤布拉格光栅在季节冻土路基应变检测中的应用

介绍了现行光纤布拉格光栅（FBG）测试技术的应用领域、传感原理以及常用的封装方式,探索将FBG用于季节冻土路基这种隐蔽工程应变检测中的适应性。主要工作有：（1）基于FBG测试技术的植入梁方法,在传感器布设方面,根据不同测试对象提出了两种封装布设方式：浅置短距离半柔性探测杆和深置长距离半刚性探测杆两种封装布设方式;（2）针对现场测试需要,对电源、光纤传感器、数据采集及分析等整套现场测试系统进行了比较优选;（3）选择两处季节冻土路基作为埋设场地并开展为期1 a的观测。测试结果表明：FBG在-20～30 ℃的温差范围内保证了很高的存活率,所提出并实现的季节冻土路基应变测试系统具有较高的测试灵敏度和可靠性。该套测试系统为隐蔽工程的物理性质指标测试提供了新的技术手段。     

利用有限元方法模拟力学拉伸试验以钢纤维混凝土为例

力学试验是获取岩石等许多工程材料力学性能的主要方法之一。 但是对某些特殊材料, 由于影响其力学性能的因素众多, 单纯通过试验来获取其力学性能, 成本高, 过程复杂。 如工程抗震中目前普遍使用的钢纤维混凝土(SFRC), 很难单纯通过力学试验来获取钢纤维的分布对其力学性能的影响。 本文基于随机方法对钢纤维混凝土建立有限元模型, 利用数值模拟的方法来估计钢纤维的分布和体积率对钢纤维混凝土拉伸性能的影响。 通过与试验结果比较验证了其可行性, 结果表明钢纤维的分布对钢纤维混凝土屈服前的力学性能影响较小, 对屈服后的应力-应变特征影响较大。 当钢纤维体积率从1%变化到2%, 钢纤维混凝土的屈服强度与体积率大致为线性关系, 强度随之增加。     

地面气象观测硬件集成系统中以太网光纤收发器硬件设计

为了集成云、能见度、天气现象等新型地面自动化观测设备,中国气象局提出了硬件集成系统设计方案,文中主要解决硬件集成系统和计算机之间的通信。根据硬件集成系统设计方案,介绍了基于光纤以太网专用芯片(KS8995MAI)的多模以太网光纤收发器硬件设计方法,此收发器通过一对光纤可以将自动气象站数据、新型观测仪器等多种传感器数据经过光纤以太网统一发送到终端计算机。测试结果表明:方案实现了气象观测数据大容量、远距离的传输。     

基于光栅传感的模型测量系统应用研究

模型试验作为解决复杂工程问题的一种有效手段已越来越受到重视。然而,与目前发展较快的模型试验系统和较为成熟的相似理论相比,测试技术相对滞后的问题依然存在。测量的精度与稳定性不能满足模型试验的需求。基于光纤/光栅传感技术的高精密性、稳定性和机光电一体的特性,结合模型试验的特殊测量要求,通过改进数据接收算法,研制了基于光学传感技术的模型位移/应变测量系统,包括光栅传感模型位移和光纤传感模型应变测试系统。该系统稳定、精度高、抗干扰,并能监测不连续位移。将该系统应用于注采气压变化条件下盐岩地下储气库变形特征地质力学模型试验中,测得了气压变化条件下围岩位移收敛和径向应变蠕变规律,测得在不同稳压阶段和不同注采气速率条件下围岩变形的不同特征。试验数据为合理确定盐岩储气库运营气压和注采气速率提供帮助,对盐岩储气库的安全稳定运营有重要意义。     

光纤Bragg光栅传感技术在隧道模型试验中应用

在模型试验中,锚杆一般尺寸较小,应变监测较为困难,可将光纤Bragg传感技术（FBG）应用于隧道模型试验中解决该问题。基于西安地铁二号线4个典型断面实际工况进行隧道模型试验,将自行设计封装的光纤Bragg光栅传感器粘贴在锚杆模型表面,监测其在不同应力状态下的应变。根据隧道开挖前、隧道开挖后、衬砌支护后、抗裂极限状态和极限破坏状态5个应力状态的实测数据,得到锚杆轴力在隧道受力过程中的变化规律。试验结果表明,锚杆受力大小在隧道开挖前后有一定变化。衬砌支护后,随围岩压力增加,锚杆轴力基本呈增加趋势,拱顶附近锚杆承受压力,支护后压力变化不大;拱肩到墙角的锚杆承受拉力,衬砌支护后受力开始增加;锚杆在含水率大的黄土隧道中受力较大,更能发挥其作用。文中方法在模型试验中的应变监测方面提出新的可靠途径。     

A regularized fiber element model for reinforced concrete shear walls

Reinforced concrete shear walls are used because they provide high lateral stiffness and resistance to extreme seismic loads. However, with the increase in building height, these walls have become slenderer and hence responsible of carrying larger axial and shear loads. Because 2D/3D finite element inelastic models for walls are still complex and computationally demanding, simplified but accurate and efficient fiber element models are necessary to quickly assess the expected seismic performance of these buildings. A classic fiber element model is modified herein to produce objective results under particular loading conditions of the walls, that is, high axial loads, low axial loads, and nearly constant bending moment. To make it more widely applicable, a shear model based on the modified compression field theory was added to this fiber element. Consequently, this paper shows the formulation of the proposed element and its validation with different experimental results of cyclic tests reported in the literature. It was found that in order to get objective responses in the element, the regularization techniques based on fracture energy had to be modified, and nonlinearities because of buckling and fracture of steel bars, concrete crushing, and strain penetration effects were needed to replicate the experimental cyclic behavior. Thus, even under the assumption of plane sections, which makes the element simple and computationally efficient, the proposed element was able to reproduce the experimental data, and therefore, it can be used to estimate the seismic performance of walls in reinforced concrete buildings. Copyright © 2016 John Wiley & Sons, Ltd.