东南大学：《建筑力学 Architectural Mechanics》课程教学课件（英文讲稿）A21 Dynamic Loading

Dynamic Loadingmi@se.er.cn

Dynamic Loading mi@seu.edu.cn

Contents·Static vs.Dynamic Loading（静载与动载）·Structural Members under Constant Acceleration （匀加速构件)·Structural Members under Constant Rotation （匀速转动构件)·Horizontal Impact onAxial Members（水平放置杆件的水平冲击)·Horizontal Impact onBeams（竖直放置梁的水平冲击）·VerticalImpactonBeams（水平放置梁的竖直冲击）·Vertical Impact with an Initial Velocity（带有初速度的竖直冲击）2

• Static vs. Dynamic Loading（静载与动载） • Structural Members under Constant Acceleration（匀加 速构件） • Structural Members under Constant Rotation（匀速转 动构件） • Horizontal Impact on Axial Members（水平放置杆件 的水平冲击） • Horizontal Impact on Beams（竖直放置梁的水平冲击） • Vertical Impact on Beams（水平放置梁的竖直冲击） • Vertical Impact with an Initial Velocity（带有初速度的 竖直冲击） 2 Contents

Static vs. Dynamic Loading. Static Loading: external loadsare gradually increased to adefinite value and subsequentlyare held in constant: Dynamic Loading: the magnitude and/ordirection of external loads vary as a function oftime. This type of loads generate significantacceleration within structural members thatcannot be neglected2.65 in万式1.10B16in.12ft3

• Static Loading: external loads are gradually increased to a definite value and subsequently are held in constant. Static vs. Dynamic Loading • Dynamic Loading: the magnitude and/or direction of external loads vary as a function of time. This type of loads generate significant acceleration within structural members that cannot be neglected. 3

Structural Members under Constant Acceleration. Given: P, A and a: Find: the stress developed in the steel ropeNR: Solution by the method of statnamic:P1. Inertia force: F =一agP2. Axial force in rope: N = P+Pa/ggg3. Normal stress developed in rope:Napaa1+(1+6AAggN△Od4.Dynamic load factor:N△a8Sstst2

P a Structural Members under Constant Acceleration • Given: P, A and a. • Find: the stress developed in the steel rope. • Solution by the method of statnamic: 1. Inertia force: 2. Axial force in rope: 3. Normal stress developed in rope: 4. Dynamic load factor: 1 d d d d st st st N a k N g                P F a g  1 d P a N P a P g g           (1 ) 1 d d st N P a a A A g g              Nd P Pa g/ 4

Structural Members under Constant Rotation. Given: O, A, p and D: Find: the stress developed in the flange of the flying wheel. Solution by the method of statnamic:1. Inertia force acting on unit length:Dla = p.1. A.0?2D2. Circumferential force:PADOD?243. Circumferential stress:xFna = po'D?Hd4A5

Structural Members under Constant Rotation • Given: ω, A, ρ and D. • Find: the stress developed in the flange of the flying wheel. • Solution by the method of statnamic: x y  FN FN 1. Inertia force acting on unit length: 2. Circumferential force: 2 2 N 0 1 sin 2 2 4 d D AD F q d          4 2 2 D A FNd d     3. Circumferential stress: 2 1 2 d D q A       D ω 5