BUILDING MOTION CONTROL: SUPPLEMENTARY DAMPING SYSTEMS FOR TALL & SLENDER BUILDINGS

Transcription

1 BUILDING MOTION CONTROL: SUPPLEMENTARY DAMPING SYSTEMS FOR TALL & SLENDER BUILDINGS Sudeesh Kala, M.A.Sc., B.E. (Hons), P.Eng. Regional Manager Associate Rowan Williams Davies & Irwin Inc. (RWDI)

2 RWDI Company background Established in employees Global presence In Indonesia since 90 s Three Practice Areas: Climate Engineering Building Performance Environmental Engineering

3 Talk Overview Vibration Overview Why are we concerned with vibration? How much is too much? How to control it? Damping Inherent structural damping Uncertainty of asbuilt damping Tall and slender buildings = low damping Supplementary Damping Systems Types and example installations Design considerations Factory acceptance testing, installation, & commissioning

4 Vibration Overview

5 What s the big deal? Vibration is a Serviceability Limit State Like deflection or local deformation, vibration limits are not typically defined by any Building Code or regulatory agency A building can be absolutely safe, yet still be unfit for its intended purpose Excessive vibration can cause: Discomfort for occupants Structure-borne noise Cumulative damage (fatigue) to partitions, glazing Elevator cable collisions inside hoistway

6 WHY DOES IT HAPPEN? What causes vibration in tall & slender buildings? Wind Earthquakes Pedestrian Loading

7 Crosswind Response Across-Wind Loading (Vortex Shedding) Directions of fluctuating force wind Vortex shedding No vortex shedding - Sometimes vortex shedding affects serviceability design only - Requires additional structure or supplementary damping to satisfy serviceability demands Wind velocity

8 Vibration in Tall Buildings, Sights and Sounds

9 Sample acceleration predictions for a high-rise building How much is too much?

10 Damping

11 Damping in Structures Inherent Damping Internal External Cladding Material Internal friction Cracking Thermal effects Contact Areas Joints Connections Bearings Partitions Flooring/Ceiling Energy radiation to the soil

12 Damping in Structures How much? Considerable scatter in available data Tall buildings certainly don t seem predisposed to *high* levels of as-built inherent structural damping Damping is often observed to be amplitude-dependent Image Credit: Smith & Willford, Arup, Damping in tall buildings uncertainties and solutions, 17 th Congress of IABSE, 2008

13 Damping in Structures Overall Structural Damping = Inherent Damping + Supplemental Damping

14 Supplementary Damping Systems

15 Types of Supplemental Damping Systems Distributed: Viscous Dampers Visco-Elastic Dampers Used extensively for control of earthquake response in highly active seismic regions Might not participate in low-to-moderate wind events Inspection & Maintenance Image Credit: Tipping Mar

16 Types of Supplemental Damping Systems Solid Mass Type: Tuned Mass Damper (TMD) Various configurations possible Water/Liquid Type: Tuned Liquid Column Damper (TLCD) Tuned Sloshing Damper (TSD) Semi-Active Damper Active Damper

17 Wind-Induced Responses - Comparison Without Damper With Damper

18 TMD Examples: Taipei 101 Pinnacle Dampers Main Tower Damper

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20 Simple Pendulum TMDs Pendulum length based on: Also add space above & below for hardware

21 Simple Pendulum TMDs, for assorted periods If T = 5.5 seconds length = 25 (7.5 m) plus If T = 6.5 seconds length = 34 (10.5 m) plus If T = 8.0 seconds length = 52 (16 m) plus If T = 10.0 seconds length = 81 (25 m) plus Plus: Add 6.5 (2 m) for cable supports, beams, etc Can be very space-consuming (vertically)

22 Alternative: Dual-stage Pendulum TMD Height requirement approx. ½ of simple pendulum configuration, plus a little more Often still too space-consuming (vertically)

23 Trump Tower, New York City

24 Alternative TMD: Opposed Pendulums Uses less space than other TMDs Accommodates wide tuning range for any building frequency Can often be adapted into mechanical floors, with footprint of e.g. 40 x 40 (12 m square) Height requirement from 18 to 26 (5.5 m to 8m) *each case requires design investigation Can practically expect 5% damping

25 Bloomberg Tower, New York 55 floor mixed use Tower Animation demonstrating motion of TMD

26 Bloomberg Tower, New York

27 Liquid Instead of a Dense Solid Same general principle as TMDs a large body of mass oscillating out-of-phase with the primary structure, and dissipating precisely the right amount of energy per cycle Liquid-based dampers TLCD TSD Other abbreviations are common: Tunes Sloshing Water Damper (TSWD) Tuned Liquid Damper (TLD) Liquid Column Vibration Absorber (LCVA)

28 TLCD Example: Random House, New York 48 floor mixed-use Tower Animation demonstrating motion of TLCD

29 57 floor mixeduse Tower TLCD Example: Comcast Tower, Philadelphia

30 Tuned Sloshing Damper (TSD)

31 Tuned Sloshing Damper: Scale Model Testing Un-tuned response Resonant response

32 Tuned Sloshing Damper: Bi-directional A TSD can be designed to work in both directions Careful detailing is required to allow attainment of optimal tuning ratio and internal dissipation ratio in each perpendicular axis of as-built structure

33 Factory Acceptance Testing Most components can be assembled and tested in the factory before shipping to building for installation

34 Conclusions Benefits of Supplemental Damping Systems Can be used in combination with mass, stiffness, and/or aerodynamic changes to improve/hone building performance Very efficient means to absorb/resist wind energy Can help maximize leasable floor space Building comfort improvements Help reduce overall cost of structure

35 THANK YOU TEL: (+65)