Towards a Rational Design Procedure for Concrete Liquid Containing Structures

含液构筑物(LCS)作为环境工程设施的一部分，主要用于水和污水处理厂以及其他工业废物。在加拿大，它们通常以矩形或圆形的形式由钢筋混凝土建造。这些结构被认为是生命线设施，需要仔细设计和详细设计，以满足裂缝和渗漏控制的适用性要求。目前，北美几乎没有LCS设计的指导方针和标准。直到最近，加拿大标准协会(CSA)才制定了污水处理厂设计标准，该标准即将发布。美国混凝土协会(ACI委员会350)已经制定了混凝土LCS的代码和注释。对于这一重要的广泛类别的结构，不同的设计指南和标准之间存在着很大的不一致。这主要是由于对这些结构的抗震性能缺乏了解。近年来，申请人对混凝土LCS的性能进行了广泛的分析调查。结果表明，目前的设计规范和标准并不能反映这类结构的实际工作性能。主要关注的问题是受弯曲和/或直接拉伸的构件的裂缝宽度与渗漏之间的关系，由于约束而导致的温度和收缩对混凝土板和墙裂缝的影响，以及与地震荷载有关的问题。一个重要的问题是与反应修正系数R有关的，该系数用于确定地震引起的当量基面剪力。因此，计划在墙板连接上进行全尺寸试验。一个钢制水压室将安装在墙壁和基础的连接处，以模拟液体与储罐的相互作用，并能够检测储罐墙壁的关键区域内可能发生的泄漏。基于上述讨论，拟议研究的主要目标是通过分析和实验程序，为钢筋混凝土储罐制定合理的设计程序，以确保安全的防渗漏结构。在试验方案中，试件在包括静水压力和动力载荷的情况下，将同时接受液体压力和泄漏试验。根据这项研究的结果，将使用基于适用性要求和保护级别的性能标准来确定R值。该项目还包括以非线性有限元方法为基础的分析研究。此外，还将利用有限元方法对混凝土高架水箱的抗震性能进行分析研究。其目的是为代码决策提供必要的输入。

Liquid containing structures (LCS) as part of environmental engineering facilities are primarily used for water and sewage treatment plants and other industrial wastes. In Canada, they are normally constructed of reinforced concrete in the form of rectangular or circular configurations. These structures are considered as lifeline facilities that require careful design and detailing to meet serviceability requirements for crack and leakage control. There are currently few guidelines and standards available in North America for the design of LCS. Only recently, the Canadian Standards Association (CSA) has developed a Standards for the design of Wastewater Treatment Plants which is due to be published very soon. The American Concrete Institute (ACI Committee 350) has developed a code and commentary for concrete LCS. There is a great deal of inconsistency among different design guidelines and standards for this important broad class of structures. This is mainly due to the lack of understanding of the seismic behavior of these structures. In recent years, the applicant has carried out extensive analytical investigations on the behavior of concrete LCS. The results have indicated that the current design codes and standards do not represent the actual behavior of these types of structures. The main issues of concern are the relationship between the crack width and leakage for members subjected to flexure and/or direct tension, effects of temperature and shrinkage due to restraints on cracking in concrete slabs and walls as well as those issues related to seismic loading. One important issue is related to the response modification factor, R, used for determining the equivalent base shear because of earthquakes. As a result, full scale experiments are planned to be performed on wall-slab connections. A steel water pressure chamber will be installed at the connection of the wall-foundation to simulate the liquid-tank interaction and to enable the detection of possible leakage within the critical regions of the tank wall. Based on the above discussion, the main objectives of the proposed research study is to develop a rational design procedure, through analytical and experimental programs, for reinforced concrete tanks that assures a safe leak resistant structure. In the experimental program, specimens while under loads which include hydrostatic, and dynamic will be simultaneously subjected to liquid pressure and leakage tests. Based on the results of this study, a performance criterion based on serviceability requirements and the level of protection will be used to establish the R values. This project also includes analytical studies which will be based on non-linear finite element method. Also, analytical investigations on the seismic behavior of concrete elevated water tanks using the finite element method will be performed in this study. It is intended to provide the necessary input for code decision making.