The Dynamic Behaviour of Lift Ropes and Components under Seismic Excitation

Transcription

1 The Dynamic Behaviour of Lift Ropes and Components under Seismic Excitation Stefan Kaczmarczyk Professor of Applied Mechanics Promosso da

2 Outline Introduction Lifts Installations traction lifts Seismic excitation Seismic damages in lift installation components Dynamic models and some results Safety codes / preventive measures

3 Introduction

4 Lift Research and Education programme: MSc/MPhil / PhD Lift Systems Engineering Systems Dynamics and Vibration Control Lift Traffic Analysis Safety Codes and Standards Annual lift and escalator conference Open access peer reviewed journal Biannual Symposium The Mechanics of Slender Structures

5 Lift installations Lifts: non structural building components, the main types: Traction Drive Hydraulic Drive Rack & Pinion Drive Screw drive Pneaumatic drive

6 Traction lift Machine/ drive unit Hoistway with guide rails Car/ sling assembly Hoistway with guide rails F y F x 1999 Elevator World Inc. compensating cables Suspension ropes F y F x F k Buffers in the pit Counterweight assembly

7 Traction lift: roping Machine room 1:1 Reeving 2:1 Reeving Travelling cables

8 Traction lift: safety gear Rocking arm overspeed governor Pivoted bob weight overspeed governor 1852, Elisha Otis, the safety elevator Cam type safety gear Governor rope Captive roller instantaneous safety gear Governor rope Progressive safety gear 1999 Elevator World, Inc. Governor tension weight

9 Seismic damage to lift installation Guide rail brackets/ anchorage Bent guide rails Roller guides broken/ loose Counterweights derailed / collided with the cars Machine room equipment moved / damaged Suspension ropes damaged/ jumped out of the traction sheave/ diverter pulleys Compensating cables damaged / out of their grooves Travelling cables broken/ hung up tangled in the hoistway

10 Rope dynamics / vibration v, v, v w, w, w u, u, u Longitudinal Lateral Out-of-plane Lateral in-plane

11 Tall buildings and structures: base excitation x(t) m s(t)

12 Tall buildings and structures (3) Tall buildings / towers sway at low frequencies. An adverse situation arises when the building structure is excited near its natural fundamental frequency. The building sway is the main cause of large motions of suspension / compensating ropes. They occur due to long period ground motions (e.g. Mid Niigata Prefecture Earthquake in 2004, Great East Japan Earthquake in 2011). At building sites far away from the epicentre conventional seismic detection systems (switches) often do not register the low acceleration/ low frequency (below 0.5 Hz) long period ground waves.

13 Tall buildings and structures (5) The ground acceleration at a site far from the epicentre may not be sufficiently high to trigger seismic detectors. However, the sway of tall buildings increases, and elevator ropes resonate with the building motion. Lateral rope vibration may then cause entanglement in the elevator shaft or damage to shaft equipment. Compensating sheave

14 Whirling motion simulation model x (m) x (m) Freq. of the rope Lateral In-Plane (Model) expriment Frequency (Hz)

15 Simulation model w 0 (t) v 0 (t) L 3 x 3 Equations of motion developed for each section of the suspension and compensating system r q M1 M car x 2 Deterministic models and stochastic models L 1 x 1 v 1 u 1 w 1 u 2 w 2 v 2 M E 2 A 2 m cwt 2 L 2 z Z 0 q M2 E 1 A 1 m 1 x 4 L 4 ground M s w q M3 comp s v

16 Simulation model: frequencies vs length The natural frequencies of the lift rope system vary with the length of the ropes. L 2 L 3 M cwt Z 0 L 4 M car L 1 ground M comp Hz; Hz

17 Simulation model: animation w 0 (t) v 0 (t) q M1 M car Z 0 x 1 L 1 v 1 z 1 w 1 ground M q M3 comp

18 Simulation model: animation L 2 L 3 M cwt Z 0 L 4 M car L 1 ground M comp

19 Codes and Standards / Technical Reports ASME / ANSI A17.1 CSA B44 Safety Code for Elevators and Escalators SECTION 8.4: elevator safety requirements for seismic risk zone 2 or greater EN defines additional requirements to EN 81 20/50 covering lifts in seismic conditions ISO/TR 25741: 2008 provides a compilation of relevant safety standards pertaining to protection of the user and vertical transportation equipment during seismic activity. ASME TR A Guide for Elevator Seismic Design

20 Mitigating measures Optimization of the suspension rope and compensation rope, governor rope tensions to shift the resonance frequency regions Lift well: protection of snag points Rope guards to prevent ropes jumping from the sheaves /pulleys Compensating rope sheave tie down Seismic switches / detection systems Upon activation of a seismic switch, all elevators with traction machines, counterweights, and selective, collective, or group automatic operation that are in motion shall proceed to the nearest available floor, open their doors, and shut down (A17.1). All registered car and landing calls shall be cancelled. New calls shall be ignored; A lift in motion shall reduce the speed or stop and proceed to the next possible landing away from the counterweight or balancing weight with maximum 0.3 m/s car speed. (EN81 77). Counterweight displacement detectors When the counterweight displacement switch is activated, the elevator, if in motion, shall initiate an emergency stop and then proceed away from the counterweight at a speed of not more than 0.75 m/s (150 ft/min) to the nearest available floor, open the doors, and shut down (A17.1). Position restrainers to the car and counterweight frames Reinforced guide rails

21 THANK YOU Promosso da