第10部分按近似概率理论的极限状态设计法课程.pptVIP

* * Chapter 10 Limit State Design Based on Approximate-probability Theory 10.1 Limit State 10.2 Approximate-probability Limit State Design Method 10.3 Practical Design Expression 10.1 Introduction to the Limit State Design 1、Action , Direct action, Indirect action 10.1.1 Action （1）Action：It is the reasons that cause internal forces or deformation in structure. loads, thermal changes, differential settlement, etc. （2）Direct Action：concentrated or distributed Loads which are the forces directly applied on the structure. self weight of structure, pressure due to wind, etc. （3）Indirect Action：The other reasons except loads which cause internal forces or deformation in structure. Thermal deformation, differential settlement 2、Action effect、load effect (1) Action effect: It is the reaction of a structure to the action. Internal forces, deformation. (2) Load effect: It is the reaction of a structure to Loads. Internal forces, deformation. 3、 Classification of loads Dead loads Self-weight, Soil pressure, etc. Live Loads, Live load on floors, snow load ,etc. Permanent loads G Variable loads Q Accidental loads It may not occur during the lifetime of structure. Once occurring, its value is high and durational time is short. Explosive force, collision force, etc. (1) Characteristic Values (or Nominal Value) of loads Permanent loads GK Variable loads Qk Determined based on the dimensions of members and the unit weight of materials. According to the probability and statistic of loads, the maximum probable load under normal condition in the working time of structure. Illustrate by examples 4. Representative Values of loads (2) The Quasi-permanent Value of Variable loads Quasi-permanent Value Qq The sustained portion of variable load which chronically are applied on the structure. quasi-permanent value coefficient of variable loads Combination Value Qc (3) The Combination Value of Variable load combination value coefficient of variable loads Frequent Value Qf