2.0.1 Allowable stress method JIPKIC 结构盘计原课 l、Basic concepts Allowable [stress method ]-a maximum stress of a section reach or exceed allowable stress,and then element fails o s[o]= strengthof material safety factor o.≤o.]=A concrete stress RC member Steel stress Where :k and k are stafey factors
safety factor strength o f material = c c c c k f = s s s s k f = RC member： concrete stress Steel stress Where ： are stafey factors. s k and k c 1、Basic concepts §2.0.1 Allowable stress method Allowable [stress method ]—a maximum stress of a section reach or exceed allowable stress, and then element fails
JPKIC RC structures as an example 结构设计原理 jhepniheipledstucturedesgn Assume steel and concrete as elastic material Plane section assumption that deformation keep a section The tensile strength of concrete may be neglected ● Strains of steel and concrete at contact are equal &=8 E bx h A b Schematic of allowable stress method of RC element
c RC structures as an example ⚫ Assume steel and concrete as elastic material ⚫ Plane section assumption that deformation keep a section ⚫ The tensile strength of concrete may be neglected ⚫ Strains of steel and concrete at contact are equal b x h s s As c c bx 2 As Schematic of allowable stress method of RC element s ci =
JPKIC 2、features 结构设计原黑 1,safety factor K>1,a lager k will have a higher safety and more material. 2.Without consideration of diversity of function 1 )load-carrying capacity. 2)service performance,crack and deformation. 3,The determination of safety is by experience judgment and no scientific basis. 3,applicable condition Non-line-shape structures,such dam,spatial shell structures. No equations in code.So elastic mechanism method is a useful tool
2、features 1、safety factor K >1, a lager k will have a higher safety and more material. 2、Without consideration of diversity of function 1）load-carrying capacity. 2) service performance, crack and deformation . 3、The determination of safety is by experience judgment and no scientific basis. 3、applicable condition Non-line-shape structures, such dam, spatial shell structures. No equations in code. So elastic mechanism method is a useful tool
JPKIC 结构计原黑 S 2.0.2 Fracture design method -1930s l、basic concept The inner force reaches ultimate inner force under loading, and then element fails.Taking flexural RC element as an example,as M≤M./k where is the inner force of section,is ultimate inner force of a cross section,k is a safety factor
§2.0.2 Fracture design method ——1930s 1、basic concept Mu M M k u M The inner force reaches ultimate inner force under loading, and then element fails. Taking flexural RC element as an example, as where is the inner force of section, is ultimate inner force of a cross section, k is a safety factor
JIPKIC 结构设计原理 RC structure as an example The principle of structure design Fracture stage as a basis Without consideration of concrete tensile strength Equavilent rectangular stress block for computation bx h A Schematic of fracture stage of RC element
b x h As 0 h s As f c c f bx 2 Schematic of fracture stage of RC element RC structure as an example ⚫ Fracture stage as a basis ⚫Without consideration of concrete tensile strength ⚫Equavilent rectangular stress block for computation