钢结构基本原理课件 (3).ppt

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1、Properties of Steel Basic Principles of Steel Structures 2.1.1 Material Requirements for Steel Structures2.1.2 Steel Properties Determined by a Tension Test2.1.3 Steel Properties Determined by an Impact Test2.1.4 Steel Properties Determined by a Cold-bend Test2.1.5 Weldability of Structural Steels2.

2、1.6 Steel Properties under the Complexity Stress States2.1.1 Material Requirements for Steel StructuresHigh tensile strength and yield strength1.1.（2）High safety reserve（1）High structural bearing capacity（3）Light self-weight2.1.1 Material Requirements for Steel StructuresBetter plasticity and toughn

3、ess2.2.（1）The structure has sufficient deformation under static or dynamic load（2）Reduce the tendency to brittle failure（3）Adjust local peak stress2.1.1 Material Requirements for Steel StructuresGood process performance3.3.（1）Easy to process into various forms of structure（2）Processing does not caus

4、e a large adverse effect on the mechanical performance of the structure2.1.2 Steel Properties Determined by a Tension TestStandard stress-strain description for structural steel1.1.OACBDEFProportional limitElastic limitYield stressTensile strengthFig.2.1 Stress-strain diagram for low carbon steel or

5、 low alloy steelFailure2.1.2 Steel Properties Determined by a Tension TestTypical stress-strain diagram for structural steel1.1.（1）Elastic stage(OE segment)（2）Yield phase(EBF segment)（3）Strengthening stage(FC segment)（4）Necking stage(CD segment)E：Youngs modulus of steel,E=2.06 x 105 MPa.1 12.1.2 Ste

6、el Properties Determined by a Tension Testy：Yield stress of steel.For example,for Q235 steel,y=235 MPa.2 2u：Tensile strength of steel.For instance,for Q235 steel,u=370 MPa.3 3Typical stress-strain diagram for structural steel1.1.2.1.2 Steel Properties Determined by a Tension TestTypical stress-strai

7、n diagram for structural steel1.1.Fig.2.2 Idealized stress-strain picture for low carbon steel or low alloy steel2.1.3 Steel Properties Determined by an Impact TestCharpy specimen impact test for structural steel1.1.Fig.2.3 Test set-up for Charpy impact testHammer（1）Test set-up2.1.3 Steel Properties

8、 Determined by an Impact TestCharpy specimen impact test for structural steel1.1.（2）Charpy specimen1 1The Charpy specimen has a V-notch(shown in Fig.2.3).2 2Charpy specimens size is 10mm 10mm 55mm.3 3The specimen will rupture when the hammer drops at a certain height.2.1.3 Steel Properties Determine

9、d by an Impact TestImpact toughness for structural steel2.2.（1）Impact toughness1 1The impact of work done by the hammer is the impact toughness(Unit:J).2 2Impact toughness is a measure of the ability of structural steel to resistbrittle fracture under impact load.3 3Impact toughness is a comprehensi

10、ve expression of strength and plasticity.2.1.4 Steel Properties Determined by a Cold-bend TestThe cold-bend test for structural steel1.1.Fig.2.4 Test set-up for the cold-bend testBend the specimen from 0to 180（1）Test set-up2.1.4 Steel Properties Determined by a Cold-bend TestThe cold-bend performanc

11、e of structural steel2.2.（1）Cold-bend performance 1 1No cracks or delamination on the outside,inside,and sides of the specimen.2 2Cold-bend test is a good method to identify the quality of steel,mainlyplasticity and weldability.3 3Cold-bend performance is a comprehensive index to judge the plasticde

12、formation ability of structural steel and metallurgical quality.2.1.5 Weldability of Structural SteelsWeldability requirements of structural steel1.1.（1）The welding of the weld seam and the nearby metal is safe and reliable1 1 No welding cracks occur in the weld seam and the adjacent metal.2 2The pl

13、asticity and mechanical properties of the weld seam and the nearbymetal are not lower than the base material.2.1.5 Weldability of Structural SteelsWeldability control standards of structural steel2.2.（1）Weldability control standards of low carbon steel.1 1Carbon(C)content is controlled at 0.12%-0.20

14、%.2 2Manganese(Mn)content is less than 0.7%.3 3Silicon(Si)content is less than 0.4%.4 4Sulfur(S)content is less than 0.045%.5 5Phosphorus(P)content is less than 0.045%.2.1.5 Weldability of Structural SteelsWeldability control standards of structural steel2.2.（2）Weldability control standards of low a

15、lloy steel.1 1 Measured with the carbon equivalent.2 2Carbon equivalent,CE is less than 0.38%.（2-1）2.1.6 Steel Properties under Complexity Stress StateThe equivalent stress of steel under complex stress state1.1.（1）Expression of the equivalent stress zs.（2-2）Fig.2.5 Three-dimensional stress diagram2.1.6 Steel Properties under Complexity Stress StateApplication of the equivalent stress of steel 2.2.（1）Determination of stress state of steel.1 1 When zs y,steel is in the elastic state,where y is the yield strength.2 2 When zs y,steel is in the plastic state,where y is the yield strength.