The BOW Project - · PDF fileThe BOW Project – Geodetic Surveying Applied | 2012 The BOW...

The BOW Project

Presented by:

Roger Leeman / MMM Group Limited

The BOW Project – Geodetic Surveying Applied | 2012

The BOW Project

• 58 story (236m) high rise in downtown Calgary

• Once completed will be the tallest building in Western

Canada and future home of the EnCana Corporation.

• ~1.9M ft2 office building

• MMM Responsible for Following Survey Scope:

• Coordinate System

• Project Control Network

• Structural Steel Plumbing and As-builts

• Construction Layout

• Site Survey for +15 Connections

• Real Property Survey

• Strata Subdivision


Horizontal Coordinate System

• Inherited local rectangular system with assumed arbitrary origin

• The local system was represented by a series of wall targets

• Additional levels of control were added and surveyed

• A coordinate transformation was performed to allow for rigorous transformations between local and geodetic systems

• Both local and geodetic coordinates were published for all network stations

• The control network was re-surveyed and re-adjusted on a quarterly basis during the life of the project

• After each re-survey, the network was re-adjusted and any statistically significant coordinate updates were published


Levels of Horizontal Control

• PDC Continuously Operating GPS Reference Stations • Pleiades Data Corp continuously operating GPS Reference Network (2

Stations within 5km)

• Framework Control • Permanent brackets on surrounding stable infrastructure (i.e. bridge

abutments)

• Roof Top Control • Leica 360 Degree Prisms / GPS Antenna mount

• Local Building (Floor) Control • Laser plummet used to plumb horizontal control upward


Vertical Coordinate System

• Local datum had been established

• Local system referenced by wall targets and site benchmark

• Local datum referenced to Calgary ASCM/HPN markers

• A small shift was determined between the local vertical

datum and the ASCM City datum

• Local datum also referenced to Framework Control markers

• The vertical datum was checked to reference benchmarks

on quarterly basis during the life of the project

• Precise steel chains used to extend elevations upward


Project Control Network


• Framework Control • Used to monitor movement of interior roof top prism network.


• Roof Top Control

• 12 roof top control markers

established

• Allowed for observations with

both GPS and Total Stations

• Direct Occupation with Total

Station

• Resection from anywhere on site


Equipment

• Precision Electronic Total Stations

• Leica TS30 – 0.5” angular accuracy / 0.6mm + 1PPM distance accuracy

• Leica TPS1201 – 1” angular accuracy / 1mm + 1.5PPM distance

accuracy

• Robotic and Automatic Target Recognition capability

• On-board least squares resection routine

• GPS

• Leica GPS1230 and Viva systems

• Dual frequency, geodetic quality receivers

• Static accuracy

• 5mm + 0.5 PPM horizontal

• 10mm + 0.5 PPM vertical

• RTK accuracy

• 10mm + 1.0 PPM horizontal

• 20mm + 1.0 PPM vertical

• RTK accuracy increased by averaging observation time over a few

minutes


Equipment

• Spirit Levelling

• Leica DNA03

• Transfer of vertical control

• Rod considerations (go invar!)

• Precise ~0.0003m / turn

• Easy to use and quick


Structural Steel Plumbing / As-builts

• Worked from roof tops of surrounding buildings

• Precise total stations used up to about level 33

• Both direct observation from roof top control markers or resection

techniques used

• GPS techniques used after about level 33


A Dynamic Work Environment

• As the building exceeds a certain cross section to height ratio

building dynamics must be considered and accounted for

• For the Bow, this became significant above level 30.

• Factors affecting building movement

• Wind Loading

• Solar Heating

• Temperature

• Artificial Loading (Cranes/Equipment/People)


Options for Compensating for Building Movement

• Option 1 (Neutral Building)

• Work from on-building locations

• Assume at some point in time the building is in a “neutral” state;

nominally, the early morning hours

• No wind

• No sun

• Stable temperature

• Establish control on the structure when building is in that neutral state

• Very difficult to establish control in stable locations that afforded good

access and visibility

• Option 2 (Monitor and Correct for Building Displacement)

• Work from off-building locations

• Determine building displacement from neutral state and correct for

displacement in near real-time

• For layout survey to proceed, building displacement (deviation from

plumb line) must be compensated for in near real time

• Determine displacement with digital inclinometers


Precision Inclinometer - Leica Nivel 220

• Two-axis high precision inclination sensor

• Optoelectronic data converted to digital output signal


Leica Nivel Inclinometers

• Installed 6 inclinometers (Floors G, 12, 24, 36, 48, 54)

• Measure x inclination, y inclination, time and temperature

• Measures offset in milliradians (mrad) / mm/m

• The height of the Nivel is required in order to determine the

displacement

• Accuracy of .005 mrad

• On-site computer logs data

• Data accessible via Internet remote desktop connection


Inclinometer Tests / Calibrations

• A number of tests were run before inclinometers were used

• Set on tribrach – test x and y movements

• 2 inclinometers on same Column

• 2 inclinometers set on same column (ground and 12)

• Switch inclinometers between ground floor and level 12

• 1 inclinometer set at center of building, 1 inclinometer set near exterior of

building (level 24)

• Calibrate when building in “neutral” state in early morning (1am-6am)

• No solar heating

• Wind minimized

• Loading minimized

• Constant temperature

• Inclinometers were monitored for a minimum of 1 week before they

were brought into service to establish baseline data


Typical Inclinometer Plot – N6

0.500

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1.000

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1.500

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Movem

ent

(mra

ds)

X Values

Y Values


Inclinometer / GPS Correction Process

• Structural steel column positioned in approximate position by steel

contractor

• RTK/GPS observations performed on column (nominal 2 minute

observation time)

• Inclinometer data for same 2 minute observation time accessed

• Computer program used to determine building displacement from

neutral state, i.e. plumb line

• Design coordinate of column adjusted to compensate for building

displacement

• Surveyor advises contractor of movement required to position

column in design location


Structural Steel Layout and As-Builts • Tower displacement values derived from inclinometer system used to correct

GPS positions and provide required results.


Column Plumbing-

RTK GPS

• Uses • Layout of Steel Columns

• Advantages/Considerations

• Safety

• Setup considerations

• Base Station Selection

• Urban Canyon L30 and below

• Dynamic structure


Building Floor Control

• Responsible to set control on every floor

• Used by all contractors for layout and as-builting

• 6 horizontal control points established on ground

level and plumbed upwards

• Benchmark set on every floor - elevations extended

upward from ground level

• Set grid lines


Floor Control - Laser Plummets

• Sokkia LV1

• Accuracy +/- 5”

• Range ~100m

• Class 2 Visible beam

• Uses

• Transfer (plumb) horizontal floor

control upward as building grew


• Conduits were placed in each floor to

enable plumbing

• Easy to use and quick

• Plexiglass used to catch the beam

• Diameter of the laser beam


Floor Control- Robotic Total

Stations

• Uses

• Floor Control

• Gridline Layout

• Edge of slab layout

• As-builts

• Transfer of Vertical Control


• Onboard Resection routine

• Sets of Angles

• Stable floor setups sometimes difficult


Floor Control – Total Stations


Floor Control - Steel Chains

• Uses

• Transfer of vertical control


• Requires a precisely calibrated chain

• Requires vertical path to hang freely

• Once setup it becomes very accurate

and fast to transfer elevations.

• Corrections must be applied to

account for:

- Temperature

- Elongation

- Tension


3D Laser Scanning

• Uses

• Accurate as-built of complex features

and connections


• Accuracy

• Speed


Scanning Data


Vertigo RTK GPS


Questions

The BOW Project - · PDF fileThe BOW Project – Geodetic Surveying Applied | 2012 The BOW...

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