Download - 2 Lecture 07

Building Information Modeling

BIM for Contractors

Jinyue Zhang @ University of Toronto 29/07/2013 BIM for Contractors 1

Agenda• Types of construction firms

• Information related to contractors from BIM

• Processes to develop a building model for contractors

• Design error detection and clash detection

• Quantity take-off and cost estimating

• Construction analysis and planning

• BIM and other management applications

• Offsite fabrication

• Use of BIM onsite

• Contract and organization changes

29/07/2013 BIM for Contractors 2

Types of construction firms• A fragmented market

– Average firm size is 9 employees.– 91.6% construction firms hire less than 19 employees.– 61.6% construction employees work in small firms (less then 19

people).

• The majority of construction firms fall in the specialty trade category (mainly small subcontractors)


Types of construction firms• General contractors

– Self-perform + subcontract– Construction management +

subcontract everything

• Home builders– Act as developers

(client+contractor)– Buy a land, apply for zoning

changes, plan and construct infrastructures, design and build the home, then sell it

• Subcontractors– Specialize in one area of type of work– Selected by GC based on competitive bids or long-established

collaboration

• Fabricators– Produce a range of standard products and custom items, mainly offsite

• Design builders– Assume responsibility for both design and construction– Serve as the single point of responsibility for the entire project


The changing business practices• The old days

– Drawings and specifications (hardcopy or softcopy) as the starting point

• Even architects used 2D or 3D CAD systems– Quantity take-off in a manual approach

• Time-consuming, tedious, error-prone– As a result, not much technical analysis until the very late phase

of design• Cost estimate, schedule, constructability

• The methodology is beginning to change– Recognized value of BIM– Early involvement of contractors, even fabricators – Building models from architects to contractors

• At least, for adding detailed information about cost and schedule• For construction planning, coordination, fabrication, procurement,

etc.













Information related to contractors from BIM• Detailed building information

– An accurate 3D model to provide graphic views and to extract quantity and component property information

• Temporary components– Equipment, formwork, and others for sequencing and planning

• Specifications associated with each component– Cross-link to textual specifications for procurement, installation

and commissioning

• Analysis data related to performance levels and project requirements– Structural loads, heating and cooling loads, targeted luminance

levels, etc. for procurement, fabrication, and MEP detailing

• Design and construction status– To track and validate the progress of components relative to

design, procurement, installing, and testing.

• Information related to operation for BOT contract29/07/2013 BIM for Contractors 7












A contractor’s building model from scratch• Contractors to add additional, construction-specific

information– Either from 2D drawings or from a 3D geometric model

• Two levels of building models– 3D only, no parametric components, for visual representation:

clash detection, constructability review, visualization, and 4D sequencing

– Hybrid 3D/parametric model, for analysis and detailing


A contractor’s building model from BIM• For non-BIM components

– Convert 2D drawing to BIM components in shared models– Be very careful for model updates

• Changes made outside the model• Version tracking













Detection of clashes and design errors• Type of clash

– “hard clash”: objects occupy the same space – “soft clash” or “clearance clash”: objects are too close for

adequate access, insulation, safety, maintenance, etc.

• The old days– Overlay individual system drawings on a light table

• With CADD– Overlay CAD layers in a 2D CAD system

• The drawbacks– Visually and manually identify potential conflicts– Slow, costly, error-prone (may overlook)– Depend on the use of up-to-date drawings

Three different types of clash detection• By visual check

• By checking physical spaces

• By rules


Building service system walk through



Clash detection with 3D models and BIM• 3D geometric models and BIM, are they different?

– 3D geometric models: no semantics– BIM: different levels of semantics and details

• Clash detection with 3D geometry– Often return a large number of meaningless clashes

• A wall abutting another wall• A pipe cutting through a wall

– Not good on non-solid objects• Only detect clashes between surfaces

• Clash detection with BIM– 3D geometry-based clash detection with semantics– Selectively check clashes between specified systems

• For example, mechanical system and plumbing system– Combined with rules to perform detection for soft clashes

• For example, the clearance between mechanical components and the subfloor is less than two feet


Requirements on BIM for clash detection• A building model with an appropriate level of

detail– Have sufficient details for pipelines, ducts, structural

components (concrete or steel), etc.– Subcontractors to participate in the model

development process as early as possible

• Multi-discipline coordination is desired– Face-to-face meeting or Web conferencing– Building models and different views to be displayed in

front of each design team– Agreed-upon-changes to be entered into the building

model prior to the next clash detection run– Don’t ignore any minor change – it may cause clashes


Two types of clash detection tools• Clash detection within BIM design tools

– Available in most BIM authoring tools– Allow quick clash detection during design

• Separate BIM integration tools to perform clash detection– Used by contractors to integrate multiple design models– Sophisticated to identify more types of soft and hard clashes– Workflow is likely to be one way and not bidirectional

• Any identified clashes cannot be fixed immediately because the integrated model have no bidirectional path connected with the original models

– Examples• Autodesk’s Navisworks Manage package• Solibri Model Checker


Solibri Model Checker













Quantity take-off and cost estimating• Cost estimating in early design

– Cannot wait until the end of design work to get an estimate– Parametric cost estimate: an approximate value in early design

stage– Based on major building parameters

• Parking garage: number of parking spaces• Commercial building: number and area of each type of commercial

space, number of floors, quality level of material– A manual process: no definition about object types in some 3D

sketching tools

• Cost estimating during design development– Move the early design model into BIM software– Capable to extract counts of components, area and volume of

spaces, material quantities – Define building models with appropriate level of detail

• Rebar in concrete footings or studs in walls– Require early participation of GC and trade contractors


BIM not to replace estimators

• An estimator’s role– Extract counts and measurements– Assess conditions in the project WRT project cost

• Unusual wall conditions, unique assemblies, etc.

– BIM just to • facilitate the time-consuming, tedious, error-prone tasks• Quickly visualize, identify, and assess conditions

• Options to use BIM to support cost estimating– Export building object quantities to estimating

software– Link the BIM tool directly to estimating software– Use a BIM quantity take-off tool


Export quantities to estimating software

• A feature provided by many BIM tools

• Spreadsheet or external database

• 100+ commercial estimating packages

• Microsoft Excel: the most commonly used one

• May not support automatic update when the building model changed


Directly link BIM to estimating software• Link the BIM authoring tool directly to an estimating

package– Via a plug-in or a third-party tool

• Plug-ins available in all major estimating software packages– Sage Timerline via Innovaya, U.S. Cost, Nomitech, Vico

Estimator– Associate objects in a building model with assemblies, recipes,

or items in the estimating package

• Assemblies or recipes to define what steps and resources are needed for construction of the components– Activities and steps needed for the construction

• Place forms, place rebar, pour concrete, cure, cladding– Resources: labour, equipment, material, etc.

• Graphically link the estimate with objects in the building model to spot objects having no cost estimate associated


Use a quantity take-off tool• Specialized quantity take-off tools

– Import data from various BIM tools to estimating software– No need to learn all features in a given BIM tools

• Examples:– Autodesk QTO, Exactal CostX, Innovaya, VICO Takeoff Manager


Autodesk QTO with Timberline


Implementation guide for BIM-based estimating• BIM is only a starting point

– Not able to deliver a full estimate in an automated way

• Start simple– Manual take-off digital take-off BIM-based take-off

• Start by counting then with a single trade– Component schedules such as door and windows

• Start in one tool, then move to an integrated process– Perform take-off in the BIM tools or by a specialized take-off

application first, then integrate estimating in BIM-based business process

• Set explicit level of detail expectations– Understand the level of detail in the building model then set the

level of expectation in estimating













Construction analysis and planning• Construction planning and scheduling

– Sequence activities in space and time– With constraints of procurement, resource, spaces, etc.

• Traditional approaches– Gantt chart

• A type of bar chart to show project schedule• May indicate some dependencies

– Scheduling software packages• Microsoft Project, Primavera SureTrak, P3, etc• Create, update, communicate project schedule using reports and

display approaches• Use Critical Path Method (CPM) in scheduling

• Some features useful for construction planning– VICO Control: location-based scheduling to schedule crews in

multiple locations– Monte Carlo simulation to consider uncertainties

4D simulation example


4D Simulation on pipeline installation



4D models to support construction planning• Early 4D models in construction

– 3D model + time association– Visualization of the sequential construction – Support visual planning in the context of space and

time

• 4D model may have different requirements than BIM– Different objects to be grouped together if to be

constructed at one time– One large object to be divided into pieces if not be

constructed at one time– Temporary structures and lay-down areas to be

included


Benefits of 4D simulation• Communication with project team

– Visually communicate the planned construction process to all team members

– Capture both the temporal and spatial aspects of a schedule

• Communication with local community– Present to laypersons regarding possible community impacts

• Site logistics– Manage lay-down areas, location of large equipment, etc.

• Trade coordination– Coordinate the expected time and space flow of trades – Coordinate work in small spaces

• Compare schedules and track construction progress– Compare different schedules


4D modeling approaches

• Manual method using 3D or 2D tools

• Built-in 4D features in a 3D or BIM tool

• Export 3D/BIM to 4D tool and import schedule


Manual, CAD-based methods• Manual 4D models

– Started decades ago– Using colored pencils and drawing– Different colors to represent sequences– A third-party to create a high-end movie or rendered animations

to visually present to viewers

• CAD-based 4D models– Colors or shadings to digitally markup CAD drawings– CAD systems to turn entities on and off

• Drawbacks– Expensive, time-consuming– Difficulty to change, update or do real-time scenario planning


BIM tools with 4D capability• 4D modeling in BIM tools

– Foundation: 3D building model with individual building objects– Enabler: an object property or parameter – Approach: filter objects in views based on their properties

• Two examples:– Revit

• “phase” assigned to each object• 4D snapshots only, no direct integration with schedule data

– Tekla Structure• Multiple links between physical objects and task objects• Visualization of 4D sequencing with color-coded objects based on

time-dependent attributes

• For most BIM tools– Have no built-in “date” or “time” capabilities– Need specific 4D modules or add-on tools to link to schedule

data29/07/2013 BIM for Contractors 35

Major BIM tools and their 4D capabilities


Major BIM tools and their 4D capabilities


Specialized 4D modeling tools• Data from 3D/BIM tools to be imported into 4D modeling tools

– Normally geometry and a minimal set of properties

• Schedule to be created in 4D modeling tools or imported from scheduling tools

• Links building components to construction activities


Considerations in selecting a 4D application• BIM import capabilities

– Minimum: geometry, name, unique ID

• Schedule import capabilities– File format? Support to link with a database?

• Merge/update for 3D/BIM building model– Does the 4D tool take multiple models? Such as from architects and MEP

designers.

• Reorganization– A wall created as “3rd Floor East Interior Wall” to be named as “Wall00687”?

• Temporary components– Scaffolds, excavation areas, storage areas, cranes, etc

• Animation– Visualization of 4D sequencing or just 4D snapshots?

• Analysis: – Check time-space conflict?

• Output: – Snapshots for specified periods of time? Movies with predefined views?

• Automatic linking– Link all walls starting “Wall_3rdFloor” to one specific activity


Navisworks: 4D Sequencing













BIM and other management applications• Track variances between budget and actual cost

– Actual costs to be imported to BIM for comparison with the budget, example of VICO Cost Explorer

• Check project status– A property “status” of each object, for example, “in design,”

“approved for construction review,” “in fabrication,” and “complete”, with different colors

• Facilitate procurement purchasing– Real-time pricing of components, for example 1stPricing to

support AutoCAD, ArchiCAD, ADT, Revit

• Improve safety management– Visual model to help construction team to assess conditions and

identify unsafe areas

Check construction status by point cloud

29/07/2013 BIM for Contractors 42 29/07/2013 BIM for Contractors 43

BIM and other management applications• Track variances between budget and actual cost

– Actual costs to be imported to BIM for comparison with the budget, example of VICO Cost Explorer

• Check project status– A property “status” of each object, for example, “in design,”

“approved for construction review,” “in fabrication,” and “complete”, with different colors

• Facilitate procurement purchasing– Real-time pricing of components, for example 1stPricing to

support AutoCAD, ArchiCAD, ADT, Revit

• Improve safety management– Visual model to help construction team to assess conditions and

identify unsafe areas

Safety

29/07/2013 BIM for Contractors 44 29/07/2013 BIM for Contractors 45












BIM for offsite fabrication

• Components to be produced and/or assembled offsite in factories– To reduce labour cost and risks associated with onsite

work– Require considerable planning and accurate design

information

• BIM to automate offsite fabrication– Accurate 3D geometry, detailed material

specifications and finishing requirements, updated delivery sequence, etc

• More discussion in next lecture













Use of BIM onsite

• Onsite installation need to be field-verified– Human errors may happen– Building models to be used for verification

• Automated technologies to support field verification, guide lay-out, and track installation– Laser scanning technologies– Machine-guidance technologies– GPS technologies– RFID tags


3D laser scanning technologies• Laser measurement devices to report data

– directly to a BIM tool for verification – Interactively create models for existing buildings

• An example– Letterman Digital Center in San Francisco– Wrong positioning of a concrete column– Detected by daily laser scanning just before concrete pouring


Other technologies• Machine-guidance technologies

– Guide and verify grading and excavation activities

• GPS technologies– GPS-enabled mobile devices working with building models

• RFID (Radio Frequency Identification) tags– Track the delivery/installation of components onsite













Contract and organization changes• Early contribution from

contractors– A key factor to achieve most

benefits of BIM

• New project organizational approach need new contracts to – encourage close collaboration – Share risk and set fees

• AGC’s (Associated General Contractors) efforts – The Contractors’ Guide to

Building Information Modeling, now 2nd Edition

Download - 2 Lecture 07

Top Related