Virtual Design and Construction in Horizontal Construction-05!03!12

7/29/2019 Virtual Design and Construction in Horizontal Construction-05!03!12

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Virtual Design and Construction in Horizontal Infrastructure Projects

By Eric Cylwik and Kevin Dwyer

May 3, 2012

In the past year, the Heavy/Civil Division of Sundt Construction, Inc.,based in Tempe, Ariz., has

used virtual design and construction (VDC) to transform its approach to the construction of

horizontal infrastructure projects like highways and bridges. VDC allows Sundt to design the

best construction solutions for project owners by facilitating communications, reducing change

orders and requests for information, eliminating rework, increasing productivity and quality,

shortening schedules, creating computerized as-built drawings and specifications, and most

importantly reducing costs.

Sundt led the industry in applying Building Information Modeling (BIM) to vertical construction

projects like office buildings, and is now transferring the lessons learned in that arena to

horizontal projects. Although the principles, methods, software, hardware, and equipment

involved in VDC and BIM are similar, participants in horizontal projects are wary of the BIM

acronym because they believe that it applies exclusively to buildings. Therefore, Sundt uses the

more neutral designation of VDC when referring to the creation and use of intelligent,

parametric, interactive computer models in the realm of horizontal projects.

Process

VDC is not simply an improved tool it is an improvedprocessaimed at facilitating

communication between participants at all levels. VDC improves the process and experience for

owners, architects, engineers, general contractors, subcontractors, suppliers, and the public in thedesign and construction of complex, expensive, and time-consuming horizontal construction

projects, regardless of the delivery method whether its design-bid-build, design-build, or

construction manager at risk. When different portions of the improved process are executed

under the right conditions at the right time, the process enhancements are seen and felt by

everyone on the project team.

Sundt began applying VDC to horizontal construction projects by asking questions about current

construction methods and looking for technologies that improve capability, efficiency, and

quality. Since the initial use of BIM, Sundt began searching for technologies to enhance specific

horizontal construction processes. After a year of research, development, and testing, Sundt,along with other stakeholders, are reaping the benefits.

Sundt first recognized the link between BIM and VDC as applied to horizontal projects while

working on light rail projects. Similar to clash detection on HVAC and other systems in

vertical building projects, VDC allowed Sundt to model and detect clashes between

underground utilities like sewers and water lines. However, clash detection on horizontal projects


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is arguably more critical because of the inherent differences between most vertical and horizontal

construction projects. Unlike vertical projects, which are usually unoccupied until completed,

builders of many horizontal projects must accommodate traffic during construction and VDC

helps with the process.

Sundt plans to create construction-ready VDC models during preconstruction of most horizontalprojects and believes that the models have the potential to transform all phases of the

construction process from surveying to paving to recording as-built information and everything

in between including excavation and forming. Since VDC is in its infancy, Sundt continues to

evaluate enhancements.

Differences between Vertical and Horizontal Construction

Construction processes in the world of vertical buildings are often repeated and repeatable. For

instance, builders may use the exact same formwork when placing concrete decks on two

separate buildings. The same trusses and supports used to support one deck can be used on thefloor above as well as on a deck at a project across town. Horizontal projects are different. The

design and construction of highways, bridges, roads, and associated utilities are more complex

due to changing surface conditions and the need to tie into existing infrastructure elements. VDC

allows Sundt to cope with complexity while improving efficiency and meeting contractual

requirements.

When building roads, bridges or utility projects, builders must deal with the variable contours of

the land, site conditions, and the need to coordinate traffic during construction. In view of these

factors, the software and methods used in VDC often have to be more flexible than those used in

BIM. In contrast to the deck example cited earlier, the inherent complexity of horizontal projectsprevents the creation and use of single static elements of a model over the entire scope of a

project. A single section of a road can easily have more than ten different conditions that can

change in a short span.

VDC on Horizontal Projects

The VDC process may begin by

obtaining a 3D laser scan of the project

site that is accurate to within a

millimeter. A 3D laser scan measures

any visible objects by timing how long

it takes light to bounce back. This

method creates millions of very precise

measurements that together create a

point cloud. Figure 1 shows the millions of

points as white dots that represent real structures and objects. This model can be navigated in 3D

and the user can take measurements directly in the program. This allows estimators to

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incorporate the laser scan into a preliminary VDC model based on the design that allows them to

explore existing conditions and evaluate proposed construction methods such as project phasing,

traffic control, excavation sequencing, and material selection. Figure 2 demonstrates how an

estimating team reconstructed an existing

bridge.

Estimates created within the context of

VDC can require more time and effort at the

beginning, but the resulting models are

accurate and flexible enough to handle

many project variables and alternative

scenarios. Because the models are created

within a 3D virtual environment, estimators

can evaluate different construction methods

without incurring the costs of mockups or prototypes.For instance, at the click of the mouse, an estimator can

change a Type A Shored Trench, to a Type B Single

Bench Trench, or even a Type C Multiple Bench

Trench in an effort to explore quantity, productivity, and

cost impacts. Figure 3 shows sample options that an

estimator can select. Beyond selecting general shapes such

as vertical or stepped sides, they can also specify

parameters like slopes and distances. Instead of spending

time calculating quantities by hand, estimators may focus

their efforts on adding value by delivering the best solutions

to project owners. As the VDC model evolves, project

teams can identify and resolve coordination issues before

construction begins and costs are incurred. For instance,

Sundt is able to model existing and new utilities and to rectify clashes before encountering the

conditions in the field. Figures 4, 5, and 6 are taken from a three-mile-long light rail project

through the heart of Phoenix, Ariz. Being able to see underground was critical to ensuring all

costs were captured and accounted for in the estimate. Not only can this process uncover

Figure2

Figure4 Figure5 Figure6

Figure3


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coordination issues, it can also reveal construction issues because methods such as trenching are

incorporated in the model. In VDC software, common trench styles, such as those in Figure 3,

are simplified down to basic and specific instructions regarding distances and angles, such as

the trench bottom is six inches below the invert elevation, or the trench width is five feet.

VDC software approaches instructions like these with packets of commands called

subassemblies.

Subassemblies

Subassemblies are small, intelligent sets of instructions that electronically depict road surfaces,

retaining walls, typical road details, bridges, grading standards, rail tracks, utilities, trenching

methods and more. Subassemblies are stored in libraries within the VDC software and inserted

where appropriate. Figure 7 represents a small sample of instructions that are used in a

subassembly. It shows starting from a specific point and moving a certain distance horizontally

and vertically based on input from the user. Subassemblies are parametric in that they allow the

components to stretch inappropriate ways to

accommodate the specific

application. Imagine a

stretchy piece of paper: if

it were parametric, it could

stretch to 11 x 17, 24 x 36, or even 5 x 3, all while still being

the same piece of paper. Similar stretching is accomplished through

parametric subassemblies. For instance, a road subassembly can

stretch to accommodate various road widths, thicknesses of aggregate

base course or asphaltic concrete, or changes to the slope of the

shoulder.

Owners, including departments of transportation, often define these

types of instructions in their standard specifications. For example, a

Type I retaining wall subassembly may contain consistent

dimensions for the footings, specific requirements for the footing toe,

and adjustable dimensions for the height of the footing wall. To

model these features, subassemblies contain variables such as footing

width, wall thickness, and wall height along with rules or algorithms

to define slopes and other features. Based on specific input, subassemblies calculate physically

accurate shapes. These shapes contain information about quantities, survey points, and guide

machines in conjunction with total stations or the global positioning system.

VDC models are often able to implement subassemblies by reading the types of spreadsheets that

estimators have traditionally created. For instance, when estimators take off a retaining wall, they

Figure7

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typically generate a spreadsheet with cells that represent the top of wall profile, top of footing

profile, and the structural type of the wall.

Figure 8 is a typical department of transportation retaining wall. It defines the shape of a

retaining wall similar to a subassembly. The standard defines the thickness of the footing from

the top of footing point down a distance of B as the first instruction. The second instruction ofa subassembly might be to go W units over, creating the width of the footing. Now the

subassembly knows the shape and size of the footing. Figure 9 is a sample showing the values

for all of the variables associated with the retaining wall. Figure 10 shows the final result: a

subassembly based on the logic from Figure 8 and the dimensions from Figure 9. The diagonal

lines on the left represent a decision made by the subassembly. The spreadsheet, along with a 3D

topographical file or laser scan, can provide the

input needed for a subassembly to create

retaining walls based on real world information,

not guesses or assumptions.

In contrast to relying solely on spreadsheets,

models also incorporate real world coordinates to

calculate existing and finished grades and

provide more accurate takeoffs of cut and fill

quantities. An excellent example is a 45-foot

trench on a site improvement project that Sundt

was recently awarded. Traditionally, an estimator

would have reviewed the plans to figure out the

average existing surface elevation and the average trench

depth. He or she would plug those numbers into a spreadsheet to calculate the excavation

quantities. The same is also true for calculating volumes of shapes that curve, for example, a

retaining wall that bends as it approaches an intersection. VDC software can calculate volumes

on a curve just as easily as volumes on a straight

section of road.

By using a VDC model, estimators can calculate

every foot of the trench from exact existing

elevations and exact trench depths and apply a slope

formula to figure out the exact amount of excavation

required. The set of commands in the subassembly

can incorporate intelligent commands like, start at

the invert elevation of the pipe at the current

station, and the next command can be if the

existing grade is more than twenty feet, build trench

A. If it is less than twenty feet, build trench B.

Figure9

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Laser scanning improves the process further since it provides up-to-date information on the

existing terrain instead of relying on outdated data. Other examples are bridges that typically

follow standard tub, stem, or beam designs promulgated by departments of transportation with

the profile and slope information applied. Using estimators spreadsheets, VDC models can

generate quantities of materials needed along with the capability to plan the work. An estimator

can utilize this same file to generate survey quality data on specific points or surfaces of the

bridge.

Fourth and Fifth Dimensions

Modeling projects properly during the estimating process allows construction teams to link the

schedule the fourth dimension (4D) and budget the fifth dimension (5D) to the three

dimensional model and to begin

construction immediately after receipt of

the notice to proceed. A detailed phasing

plan for complex steel arches is shown inFigure 11. Not only does this model

include the physical pieces to install, it

shows the order and the phasing of the

scaffolding.Sending VDC models tosubcontractors facilitates the development

of shop drawings and allows the

incorporation of subsidiary models

prepared by subcontractors for their scopes

of work. VDC can be used as a platform

for communication of the huge volumes of information contained in a project, as opposed to a

CAD file that only contains line work. VDC also facilitates the creation of animations that

dramatically demonstrate the construction process over time and allows Sundt to identify the

most efficient means of construction.Recently, Sundt self-performed deep

excavations with shoring subcontractors by

creating a VDC model that showed the

volumes to be excavated for an

underground structure. Sundt was able to

calculate the surface area that required

shoring at the end of each shift. This

process allowed Sundt and its

subcontractors to communicate better as

well as reduce costs and possible time

impacts of miscalculated quantities. Having specific quantities for each shift ensured that

proper crews and equipment were onsite based on each days need. Figure 12 is an excavation pit

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for a basement thirty feet underground. The model was not only able to calculate specific dirt

volume quantities, but also the area exposed when the volumes were removed.

Ancillary Benefits of VDC

Other benefits flow from VDC models. For instance, project managers and superintendents mayuse quantity information generated by VDC models to create work plans as shown in Figure 12,

generate daily reports, and provide feedback on the status of construction. In addition, the public

may view models in order to visualize and monitor construction activities and coordinate travel

and work plans.

In Portland, Ore., Multnomah County instituted a public relations program on the Sellwood

Bridge project that allowed Sundt to publish construction models suitable to the needs of the

public. A series of videos atwww.sellwoodbridge.orgshows construction phasing for this

complex bridge project that

involves moving an existingbridge almost sixty feet to

carry traffic while a new

bridge is built. Figure 13

shows the bridge after the

move to its temporary

location. The object in red is

the original bridge pier.

Traffic flow is represented

with green arrows.Another example illustrates the advantages of VDC. Traditionally, surveyors have calculated the

points needed to define the location of roads by plugging numbers into as many as six different

formulas. Since the complexity of roads varies considerably, it is difficult to define the typical

amount of time and expense of using traditional

methods. Nevertheless, to demonstrate the

advantages of VDC, Figure 14 illustrates a

typical 20-step process for calculating bridge

points. A surveyor following traditional

processes might spend 20 hours calculating the

1,400 points needed to define a complex sectionof road, if we assume that each point takes an

average of one minute to calculate (a

conservative assumption).

Figure13

Figure14


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In contrast, by using VDC and creating models of typical road sections, surveyors can

visualize the project, understand the requirements, and avoid spending large blocks of time

solving math problems that computers can solve instantaneously. Based on Sundts experience,

using this method can easily reduce calculation time by up to thirty percent. If discrepancies

arise, the survey crew can use the construction documents to verify features and components in

the model.

VDC and Equipment

After the participants on a horizontal construction project verify the VDC model and set the

controls on the jobsite, operators can upload files containing the alignment and 3D surface of the

road to computers in heavy equipment like graders or excavators. The surface model provides

operators with information needed to grade roads or dig trenches. A computer screen in the

grader or excavator displays exactly where to cut or fill based on the location of the blade or

bucket. When work has progressed to the point of the final pass, operators can turn on automated

machine guidance and allow computers to make the millions of micro adjustments needed toachieve a perfect grade.

For example, when lowering the profile of an existing 5,000-foot stretch of Interstate-17 in

Arizona, Sundt used this process to ensure proper survey calculations and loaded the model

directly into computerized monitors on heavy civil equipment. Not only did it save time by

eliminating the need for a two-man survey crew to spend two weeks blue topping the road

(placing wooden stakes to define the top of the grade), the productivity rate of Sundts equipment

and crews increased significantly since there was constant and direct communication via

automated machine guidance. Sundt was able to deliver a quality product to the owner without

need for rework.

Other efficiencies that flow from VDC include less wear and tear on equipment, reduced fuel

consumption, and fewer injuries. In addition, VDC models can adjust to changes in elevation,

baseline, superelevated roadways, and drainage conditions as well as blending finished grades

into other construction elements. For instance, one segment of roadway might daylight at a 4:1

grade while ten feet way it might daylight at 3:1. Figure 15 shows an intelligent model with five

different road scenarios on

the left, and a standard option

on the right. The model is

able to read conditions anddecide which scenario to use.

VDC also allows surveyors to

establish elevations for specific points on concrete bridges in a one-step process, instead of the

traditional two-step process. By using a 3D model of the proposed deck surface, computerized

equipment is able to calculate real time cut and fill dimensions for any spot on the bridge. They

Figure15


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no longer have to collect 3D points in the field and then return to the office to calculate the

corresponding proposed elevations by hand. The model computes the required coordinates by

comparing real world data uploaded into the model against the design coordinates in real time

out in the field. The surveyors equipment uses the same process as the grader to display real

time information showing existing conditions compared to proposed conditions. As a result,

surveyors can give instant feedback about any given point on a bridge and no office calculation

time is required.

One of the greatest benefits of VDC is that it facilitates the discovery of clashes and coordination

issues within the virtual environment of the computer not in the field and consequently

reduces requests for information and change orders along with the associated health and safety

risks. On a recent project involving a complex trenching method, Sundt utilized VDCs accurate

dimensional modeling capabilities to comply with OSHA regulations that stipulate that if the

bottom of a trench is more than twenty feet deep, it needs to have a bench in the sidewall to

prevent the walls from caving in and potentially injuring workers. VDC leads to solutions by

enhancing communications between participants by allowing them to visualize challenges in an

intuitive environment that may be manipulated to illustrate problems and create solutions.VDC also improves quantity calculations and reduces raw material costs. For example, models

allow builders to know instantly whether they have placed the proper quantities of materials like

aggregate base course because the model is linked directly to computers in the cabs of heavy

equipment. Traditionally, builders erred on the side of placing too much material rather than too

little in order to meet or exceed specifications. In short, teams using VDC experience fewer

communication problems due to the wealth of information communicated via virtual design and

construction software. When a designer specifies a road width or structural thickness, it is

communicated to every stakeholder through VDC software on demand and the designers intent

is not hidden in hundreds of pages of project plans and specifications.

Case Study

Recently, Sundt submitted a

bid on a medical hospital

project for the U.S. Army that

included placing a sewer pipe

forty-five feet below grade.

Traditionally, on this type ofproject estimators would have

used an Excel spreadsheet

similar to the one showed in

Figure 16 that includes

information about depth and the existing grade with the concomitant potential for errors. In

contrast, a VDC model allowed the estimator to evaluate the process quickly and efficiently.

Figure16


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By analyzing different scenarios with a VDC model, the estimator analyzed daylight slopes on

the side of the trench, which allowed Sundt to make an informed decision regarding the best

method of construction. The VDC model allowed the estimator to evaluate three scenarios:

digging the entire trench in one pass and moving all of the dirt elsewhere on the site; a two-pass

method that involved moving excavated dirt two times; and a two-pass method that involved

moving the dirt once. Each scenario implied different quantities and costs. The model allowed

Sundt to visualize the sections of the trench based on the alignment and profile of the pipe.

Using VDC, the estimator explored a two-step process to install the sewer pipe at a lower cost

than using traditional methods. The first step analyzed using a scraper to plough out a flat area

twenty-five feet below the existing grade. The area excavated followed the slopes of the existing

parcel as well as the alignment and profile

of the proposed sewer pipe while

automatically displaying offset and

elevation information.

To reduce construction costs, the scraper

will dig the trench wide enough to hold

the dirt excavated from the twenty-foot

trench required for installation of the pipe

at forty-five feet below grade. This

innovative method avoids the costs and

delays associated with placing the dirt in

trucks, hauling it to another location

during construction, and then hauling itback to fill the trench. Figure 17 is a

section through the proposed trench. The

orange area illustrates the first scraper

pass, the light green the excavator pass,

and the dark green where the extra dirt

was placed. Figure 18 is the 3D model

showing a section every twenty-five feet.

In addition, the VDC model of the trench

was loaded directly onto scrapers andexcavators with automated machine guidance. This provided instant feedback to the operators

and ensured that the trench precisely followed the model used to estimate the project. As a

bonus, during construction Sundt generated as-built information at no additional cost using the

GPS features on the excavator.

Figure17

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Contrary to the concerns of current industry professionals, participants do not necessarily need to

become experts on using VDC software because subassemblies or templates can read

spreadsheets that provide the information needed by models. After the information is loaded and

checked, intelligent templates or subassemblies can precisely calculate angles, elevations, grade

breaks, and volumes. Estimators may then use the resulting model to take off quantities and to

plan the project since the model is a byproduct of the estimate.

Conclusion

Lagging productivity and adversarial relationships plague the construction industry. As part of its

commitment to deliver quality horizontal projects to owners on time and within budget, Sundt

has demonstrated that VDC improves the constructionprocessand frees skilled professionals to

concentrate on creating solutions instead of calculating quantities or fixing problems in the field.

VDC enables all participants in a horizontal construction project owners, architects, engineers,

general contractors, subcontractors, suppliers, and the public to visualize the entireprocess in a

seamless, holistic way and to create innovative techniques to meet increasingly constrainedbudgets and deadlines. Sundt invites all participants to join us as we explore the possibilities.

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Virtual Design and Construction in Horizontal Construction-05!03!12