摘要
目前,我国正处于基础设施建设的高速期,混凝土工程量巨大,减少和避免混凝土的开裂意义重大。检测与评价混凝土的开裂敏感性,是采取有效措施减少或避免混凝土开裂的前提。混凝土结构施工中裂缝的产生与温度应力有直接的关系,温度变化对结构的应力状态具有重要的影响。
本文主要针对温度—应力试验机温湿度控制系统展开研究,总结国内外研究现状,系统分析了温度和湿度变化对混凝土抗裂性能的影响,采用理论与实际相结合的研究方式,设计出温度—应力试验机温湿度控制系统。
论文首先介绍了温湿度控制的基本原理和温度—应力实验机的发展状况,叙述了温湿度控制方法的研究与现状、虚拟仪器技术和数据库软件SQL Sever 2000的特点。然后,根据混凝土温湿度检测的特点与检测方法,提出了温湿度控制系统的总体方案,包括硬件方案和软件方案。
硬件设计主要分为数据采集和温湿度控制两大部分。数据采集部分主要完成多路信号调理和多通道的数据采集,主要采用信号调理板和数据采集控制卡实现;温湿度控制部分主要是按照试验要求通过控制卡驱动执行机构完成温湿度调节,主要采用温控模板和环境箱实现。
软件设计是系统的核心部分,它基于LabVIEW平台开发,主要由数据采集、数据处理与显示和温湿度控制等3大功能模块组成,此外还包括硬件板卡的驱动程序。数据采集模块包括初始化程序,参数设置程序和数据采集程序,主要完成对温湿度电压信号的采集。数据处理与显示模块主要完成对温湿度电压信号数据的标定,采用加权平均值法将电压值转换成温湿度数据,通过调用数据库实现数据的存储与查询,并采用数值显示和图形显示相结合的方式,准确显示不同时刻的信号值及其变化趋势。温湿度控制模块主要实现对于温湿度的调节。按照控制指令实现对温控模板和环境箱温湿度执行机构的控制,拟采用PID控制算法。
During a high-speed period of basic facility construction in China, large engineering quantity of concrete makes it much important to reduce and avoid concrete crazing. Measuring and evaluating concrete crazing sensitivity is first operative step to keep away from its cracks. The emergence of cracks is direct relation to temperature-stress, and the temperature change has the important influence to the structure-stress condition.
In order to work out the temperature & humidity control system, aiming at the Temperature-Stress Testing machine temperature & humidity control system, summarize the domestic and foreign present researches, analyze the influence to the concrete anti-crazing caused by the changes of the temperature and the humidity, and adopt the research method which combined the theory and practice.
Firstly introduce the basic control principle of the temperature & humidity and the development condition of the temperature-stress testing machine, narrate the research method and the present situation, the virtual instrument technology and the characteristics of the database software SQL Sever 2000. Then, according to the examination characteristic and method of the concrete temperature & humidity, put forward the whole plan of the temperature & humidity control system, including hardware plan and software plan.
The hardware design is divided into two aspects: data acquisition and temperature & humidity control. Data acquisition is mainly made use of the signal-conditioning board and the data acquisition control card to realize multi-channel signal-conditioning and signal acquisition, temperature & humidity control aspect utilizes the temperature control template and the environment simulation box to realize the accommodation of temperature & humidity through executive implement drove by the control card, according to the experimental request.
The software design is the key part of the system design, which based on LabVIEW development platform, includes data acquisition module, data processing and display module, control module, as well as some hardware drive procedure. Data acquisition module, which is made up of the initialization procedure, the parameter setting procedure and signal acquisition procedure, mainly accomplishes the acquisition of the temperature & humidity signal. Data processing and display module achieves the signal transform through weighted-average method, transfers database to realize data storage and inquiry, exactly displays the signal at the different time and the trend via the united way of the numeric display and the graph. Control module adopts PID arithmetic to realize the temperature & humidity adjustment.
引文
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