《混凝土结构设计原理》双语 (10).ppt

Chapter 3 Design method 3.1 Functions which should be satisfied during design Reliability (可靠性） The properties of a structure or part of it will perform its intended function for a specified period of time under required condition Intended function Safety （安全性） 正常施工、正常使用条件下，能承受各种可能出现的外界作用而不发生破坏 偶然事件发生后，保持必要的整体稳定性 Serviceability （适用性） 正常使用条件下，有良好的使用性能。如吊车梁变形过大、水池开裂不能蓄水，虽然不引起倒塌，但已丧失使用功能。 Durability （耐久性） The ability of structures to fulfill its intended function during its intended life span. (在预订的时间内完成预订的功能的能力) Design purpose To achieve acceptable probabilities（概率） that a structure will not become unfit for its intended use – i.e., that will not reach a limit state. Specified period of time (设计基准期) 50 years Required condition Proper design, construction and maintenance 3.2 Uncertainties in reliability assessment Loads；（作用） Material strength, geometry of section, calculating methods （抗力 ） Random variables （随机变量） Design use the concept of probability and apply the methods of statistics 3.3 Review of probability theory Random variable A random variable is a variable whose values vary randomly and cannot be predicted precisely in advance Probability distribution function （分布函数） The probability distribution function of a random variable is probability for the random variable being smaller than or equal to a variable Probability density function （概率密度函数） Moment（矩）: 1st moment Mean value (Mathematical expectation(数学期望）) 2nd moment Variance （方差） Variance= Standard deviation（标准差） Coefficient of variation （变异系数） 3.4 Classification of design methods 水准Ⅰ 半概率法 水准Ⅱ 近似概率法 水准Ⅲ 全概率法 3.5 Limit State Design Two principal types of limit state: o?????? Ultimate limit state: The whole structure or its components should not collapse, overturn or buckle when subjected to design loads. o?????? Serviceability limit state: The structure should not become unfit for use due to excessive deflection, cracki