review(钢结构基本原理复习).ppt

1、1,钢结构基本原理复习,Design Principles of Steel Structure,Design Principles of Steel Structure,1 Summarize,Key 1: What are the features of steel structure?,(1) High strength of steel, light weight of structure（钢材强度高，结构质量轻） (2) Isotropic material, high reliability（材质均匀，可靠度高） (3) Convenient fabrication, quick

2、erection（制作方便，施工快速） (4) Good leakproofness（密闭性好） (5) Heat-resistant but not refractory（耐热不耐火） (6) Be corroded easily , maintained costly（易腐蚀，维修费用大）,The structural limit state,Key 2: The Design Method of Steel Structure,a. The ultimate limit states: The basic combination of load effects shall be cons

3、idered and, if necessary, the accidental combination of load effects shall also be considered. b. The serviceability limit state: The load standard combination of steel structure design is only considered.,Design Principles of Steel Structure,1 Summarize,(1) Higher fy and fu（有较高的fy 和 fu）,(2) Good Pl

4、asticity and impact toughness（有良好的塑性和冲击韧性）,(3) Good machinability（有良好的加工性能）,(4) Good adaptability to working circumstance（对环境良好的适应能力）,Design Principles of Steel Structure,2 steel material,Key 1: The requirements of steel structure material,Key 2: Failure modes of steel structure material,(1) Plastic

5、 failure (塑性破坏) There is obvious deformation or collapse omen before failure. (2) Brittle failure (脆性破坏) There is little deformation or no warning before failure. (3) 影响脆性破坏的因素化学成分、冶金质量、温度（低温）、冷作硬化、时效、应力集中、复杂应力。,Design Principles of Steel Structure,2 steel material,Design Principles of Steel Structu

6、re,2 steel material,Key 3: The main mechanical properties of steel,(1) Strength fu, fy fu, fy , f (2) Plasticity 材料发生塑性变形而不断裂的性质 (3) Cold bending performance钢材发生塑变时对产生裂纹的抵抗能力，是判别钢材塑性及冶金质量的综合指标。 (4) Impact toughness动力指标，钢材在断裂或塑变时吸收能量的能力，是强度与塑性的综合表现。 (5) Weldability (6) Durability,注：承重结构的钢材至少应保证fu, fy

7、 , d三项指标满足要求。,Key 4: Factors affecting the performance of steel,(1) The influence of chemical composition(化学成分) C, Mn, Si, S (hot shortness), P (Cold shortness). (2) The influence of steel-making (钢材生产过程) (3) Temperature influence (温度) High and low Temperature (4) Hardening influence (硬化) f, d , Akv

8、 (5) The influence of stress concentration (应力集中),Design Principles of Steel Structure,2 steel material,Key 5: Fatigue of steel structure,Design Principles of Steel Structure,2 steel material,(1) 疲劳破坏的特征： 脆性破坏 (2) 影响因素： 构件和连接的构造类型 循环次数 循环应力比 应力幅 残余应力,Key 6: Types of steel,(1) 碳素结构钢：代表Q235 (2) 低合金高强度

9、钢：代表Q345、Q390和Q420 (3) 钢材的牌号：例如：Q235A、Q235B和Q235C 有何区别 (4) 型钢(profiled steel): I-, H-, L-, T-, -shape.,Design Principles of Steel Structure,2 steel material,Key 1: The main types of connections,(1) welded connections (焊缝连接) 手工电弧焊、焊条与钢材适应 (2) bolt connections (螺栓连接) Common Bolts (refined bolts and cr

10、ude bolt) High-strength Bolts (friction-type and pressure-type) (3) rivet connections (铆钉连接),Design Principles of Steel Structure,3 Connections,Key 2: Types of Welds,(1) Groove welds (对接焊缝) 坡口形式；引、落弧板；变厚度与变宽度的连接 标注方法： (2) Fillet welds (角焊缝) 标注方法： (3) Strength and quality inspection of welding line（焊

11、缝质量检验与焊缝强度）,Design Principles of Steel Structure,3 Connections,Key 3: Details of fillet welding line,Design Principles of Steel Structure,3 Connections,板件hft,t6mm 边缘hft-(12)mm,t6mm,hf1.2t1(钢管构件除外),t1为较薄焊件厚度，t为板边角焊缝的板件厚度,；当t24，hf =t2,t2为较厚焊件。自动焊可减1mm；单面T形焊应加1mm,若超出限值，则超出部分在计算中不考虑。内力沿侧缝全长均匀分布者不限,t1为较薄

12、焊件厚度， lw为每条侧面焊缝的长度， b为两条侧面焊缝之间的距离,b16t1 ,当t112mm b190mm,t112mm,t1为较薄焊件厚度,1、轴心力作用下,Key 4: Calculations of Fillet welds,Design Principles of Steel Structure,3 Connections,受力分析：,校核:,1、轴心力作用下,例题详见作业。,Key 4: Calculations of Fillet welds,Design Principles of Steel Structure,3 Connections,2、N、M、V共同作用,Key 4

13、: Calculations of Fillet welds,Design Principles of Steel Structure,3 Connections,(1) 焊接应力产生原因：不均匀加热与冷却 (2) 焊接残余应力的类型： (3) 对结构性能的影响： 静力强度：无影响 结构刚度：降低 稳定承载力：降低 低温工作：变脆 疲劳强度：降低 (4) 减小焊接残余应力、变形的设计和工艺措施:,Key 5: The stress and deformation of welds,Design Principles of Steel Structure,3 Connections,(1)螺栓排

14、列：并列、错列 (2)螺栓排列：需要考虑受力、构造和施工要求 (3)端距要求：不应小于2d0 (4)中距要求：最小中距3d0 (5)排列要求：参见规范,Key 6: Details of bolts connecting,Design Principles of Steel Structure,3 Connections,（1）螺栓杆被剪断 （2）孔壁的挤压破坏 （3）板件被拉断 以上破坏形式予以计算解决,Key 7: Strength failure of the shear bolt,Design Principles of Steel Structure,3 Connections,（4

15、）板件端部被剪断（拉豁),（5）栓杆弯曲破坏,Key 7: Strength failure of the shear bolt,Design Principles of Steel Structure,3 Connections,普通螺栓群轴心力作用下抗剪计算,N1F,Key 8: Uniform shear of bolts group,Design Principles of Steel Structure,3 Connections,普通螺栓群轴心力作用下抗剪计算,Key 8: Uniform shear of bolts group,Design Principles of Stee

16、l Structure,3 Connections,Key 9: The working performance of bolt,Design Principles of Steel Structure,3 Connections,(1) 普通受剪螺栓： 从受力直至破坏经历四个阶段，由于它允许接触面滑动，以螺杆剪断或孔壁受压破坏的极限状态作为设计准则 (2) 普通受拉螺栓：以螺栓被拉断作为承载力极限状态 (3) 高强度螺栓： 高强度螺栓在拧紧时，螺杆中产生了很大的预拉力，而被连接板件间则产生很大的预压力。连接受力后，由于接触面上产生的摩擦力，能在相当大的荷载情况下阻止板件间的相对滑移。当外力超

17、过了板间摩擦力后，板件间即产生相对滑动。高强度螺栓摩擦型连接是以板件间出现滑动为抗剪承载力极限状态；而承压型是允许板件产生相对滑移后螺栓受力，最后以螺栓被剪断或挤压破坏为抗剪承载力极限状态。,(1) 弯曲屈曲：双轴对称工字型截面 (2) 扭转屈曲：双轴对称十字型截面 (3) 弯扭屈曲：单轴对称T型截面,Key 1: Buckling modes of strut,Design Principles of Steel Structure,4 Axial forced member,Key 2: Factors affecting column stability,Design Principle

18、s of Steel Structure,4 Axial forced member,Effect of residual stress in member (焊接残余应力) Initial out-of-straightness (初弯矩) Accidental non-concentric loading (初偏心) Different End Conditions (端部约束不同),Key 3: Checking of Axial forced member,Design Principles of Steel Structure,4 Axial forced member,（1）强度验

19、算,（2）刚度验算,Key 3: Checking of Axial forced member,Design Principles of Steel Structure,4 Axial forced member,（3）整体稳定验算,（4）局部稳定验算,Key 3: Design principles of Axial forced member,Design Principles of Steel Structure,4 Axial forced member,1）Equistability principle 双向等稳,2）Width limb and thin wall 宽肢薄壁,3）

20、Manufacture saving of labor 制造省工,4） Connect convenient 连接方便,Key 1: Factor influencing Mcr,Design Principles of Steel Structure,5 Beams,(1) EIy , GIt , EIw , Mcr.,(2) Spacing of lateral supports in the compression flange of beam, l1, Mcr.,(4) Loading position (a) on cross section: On top flange (a0),

21、 Mcr .,(3) Loading pattern,(5) The stronger restraint, Mcr .,(6) Geometric parameter about asymmetric section (截面不对称几何特性), By: enlarges the compression flange of beam, Mcr .,Key 2: Situations not be needed to cal. O.S. of beams,Design Principles of Steel Structure,5 Beams,（1）有刚性铺板密铺在梁的受压翼缘上并与其牢固连接，能

22、阻止受压翼缘侧向位移（截面扭转）时。 （2）H型钢或工字形截面简支梁受压翼缘自由长度与其宽度之比l1/b1不超过表5.3所列数值时。 （3）箱形截面简支梁的截面尺寸h/b06且l1/b095(235/fy)时。,1.强度验算： 包括正应力、剪应力、局部压应力验算，对组合梁还要验算翼缘与腹板交界处的折算应力。,(1) 正应力,(2) 剪应力,(3) 局部压应力,(4) 折算应力,Design Principles of Steel Structure,5 Beams,Key 3: Checking of beams,2.刚度验算：,均布荷载下等截面简支梁, 标准荷载下梁的最大挠度 受弯构件的挠度

23、限值，按表规定采用,梁的最大挠度可用材料力学、结构力学方法计算。,Design Principles of Steel Structure,5 Beams,Key 3: Checking of beams,3.整体稳定验算：,(1) 判断梁是否需要进行整体稳定验算。 (2) 如需要则按照梁的截面类型选择适当的计算公式计算整体稳定系数。 (3) 不论哪种情况算得的稳定系数大于0.6，都应采用修正公式进行修正。,(4) 采用公式验算整体稳定承载力是否满足要求。,Design Principles of Steel Structure,5 Beams,Key 3: Checking of beams,4.局部稳定验算：,) 对于焊接组合梁，翼缘可以通过限制板件宽厚比保 证其不发生局部失稳。 ) 腹板则较为复杂，一种方法是通过设置加劲肋的方 法保证其不发生局部失稳；另一种方法是允许腹板 发生局部失稳，利用其屈曲后承载力。,Design Principles of Steel Structure,5 Beams,Key 3: Checking of beams,(1) The GB code prov