Establishing Construction Scheduling Progress Curve based on

Buidling Information Modeling Quantity Takeoffs

Kun-Chi Wang

, Wei-Hao Wu

, Pei-Yuan Hsu

, Abdoul-Aziz Gansonre

Wei-Chih Wang

and Cheng-Ju Kung

Department of Civil Engineering, National Chiao Tung University, Hsinchu, Taiwan

Concord Tech Co., Ltd, Taipei, Taiwan

Keywords: Building Information Modeling, Construction Schedule Control, Quantity Takeoff, Cost Cumulative Curve

(S-curve), Scheduling Activities, Cost Items.

Abstract: A cost cumulative progress curve (called S-curve) is often used as a basis for effective schedule control

which is a key to the success of construction projects. In establishing a planned S-curve of a construction

project, the cost of each scheduling activity must be determined. Furthermore, the contractual costs

associated with the cost items should be fully distributed to all scheduling activities. However, the

relationships between scheduling activities and cost items are complex because these relationships may be

1-to-1, many-to-1 or many-to-many relations. This research proposes a searching algorithm to conduct

quantity takeoffs in Revit and QTO to facilitate the establishment of the planned S-curve. The proposed

search algorithm defines different search steps (using various searching parameters, such as "floor",

"physical object", "cost item", and "area") to identify corresponding cost items associated with different

types of activities. The benefits of the proposed algorithm is demonstrated by applying it to a high-tech

facility building in northern Taiwan.

1 INTRODUCTION

Project scheduling is a fundamental task in the

management and execution of construction projects

(Hendrickson and Au 2003). A cost cumulative

curve (called S-curve), a graphical representation of

the cumulative progress of a construction project,

from start to finish, is often used as a basis for

effective schedule control of a project. In

constructing a planned S-curve of a construction

project, the cost of each scheduling activity must be

determined. Notably, the contractual costs associated

with the cost items should be fully allocated to all

scheduling activities.

To calculating the costs of an activity, first, one

needs to determine the quantities of the planned

construction materials (such as reinforced steel, form,

and concrete) associated with the activity. Then,

based on the unit prices associated with the

construction materials, the costs of the activity are

obtained by multiplying the quantities and unit

prices. However, finding the construction materials

associated with each activity is complicated because

the relationships between activities and construction

materials (or cost items) may be 1-to-1, many-to-1

or many-to-many relations.

Consider a many-to-many relationship for

example. Both activities, setting 1st-floor

columns/walls steel and setting 1st-floor beams/slabs

steel, are related to the costs of two cost items

(construction materials), SD420W steel and SD420

steel. Furthermore, for instance, the activities of

280kgf/cm2 concrete grouting for the 1st floor slab,

the 2nd floor slab and the 3rd floor slab represent a

many-to-one relationship, where “many” activities

corresponds to “one” cost item (280kgf/cm2

concrete). Although this above calculation process is

possible, it is highly time-consuming and error-

prone.

Recently, BIM quantity takeoffs capacity has

progressively shown its effectiveness (Shen and Issa

2010; Chen 2011; Chai 2012; Wijayakumar and

Jayasena 2013). This study thus intends to utilize

BIM quantity takeoffs capacity to support the

quantity takeoffs of each scheduling activity for

obtaining the costs, leading to the establishment of a

planned S-curve for effective schedule control.

139

Wang K., Wu W., Hsu P., Gansonre A., Wang W. and Kung C..

Establishing Construction Scheduling Progress Curve based on Buidling Information Modeling Quantity Takeoffs.

DOI: 10.5220/0005522901390144

In Proceedings of the 10th International Conference on Software Engineering and Applications (ICSOFT-EA-2015), pages 139-144

ISBN: 978-989-758-114-4

 2015 SCITEPRESS (Science and Technology Publications, Lda.)

2 LITERATURE REVIEW

2.1 BIM Quantity Takeoffs

While traditional estimation methods conduct

quantity takeoffs from 2D CAD drawings, a BIM

tool can obtain the required data and measurements

for quantity takeoff from a 3D model (Rundell 2006;

Shen and Issa 2010). Recently, many researchers in

Taiwan have developed BIM-based tools to support

quantity takeoffs. For example, Chen (2011) used

Autodesk Revit to perform quantity takeoffs for a

twelve-story reinforced concrete office building. His

study showed that the quantities of concrete and

steel extracted from BIM were 0.5% and 3.7% less

than the conventional estimation, respectively. Chai

(2012) developed a Revit API program to

automatically calculate the quantities of forms.

Regarding the quantities of forms, for instance, the

BIM generates the results were close to the ones

calculated manually, with only 1% difference.

2.2 BIM and Cost Estimates

Eastman et al. (2011) pointed out that although there

are BIM-based quantity takeoffs tools available to

assist the cost estimates, there is no BIM software

with full estimation functions. Therefore, a cost

estimator must either export the BIM quantities into

the cost estimation software, Link the BIM tool

(software) to the cost estimation software through an

API, or export BIM model data into a BIM-based

cost estimation software (Rundell 2006; Eastman et

al. 2011).

3 MODEL FOR ESTABLISHING A

S-CURVE

This study proposes a model to establish S-curves of

construction projects. The proposed model consists

of four steps, as shown in Fig. 1: (1) developing a

BIM model associated with cost items, (2)

conducting searching algorithms to perform quantity

takeoffs in Autodesk QTO, (3) mapping contractual

unit prices from cost estimation software, and (4)

converting to Excel to build a S-curve. These four

steps are described in the following subsections.

Step 1: Developing a BIM Model Associated

With Cost Items.

In the proposed model, first, a BIM model with the

level of detail (LOD) 300 must be built. This BIM

model is composed of physical components and

information parameters. Physical components are

such as columns, beams, walls, slabs, doors,

windows and rooms.

The information parameters in each physical

component are divided into two parts: additional

geometric parameters and cost-item parameters.

Besides to the geometric data (such as length, width,

height, area, and volume) of a physical component,

additional geometric parameters are required to

conduct quantity takeoffs. For instance, the

information required to conduct the quantity takeoffs

for the steels of a wall include: the data of length and

height of the wall from the common geometric

parameters; and, the data of spacing of horizontal

bar, spacing of vertical bar, steel unit weight, and the

number of bar layer for this wall from the additional

geometric parameters.

To add the cost items associated with each

physical component, this study uploads the

contractual cost items to the Revit using the

"keynotes", "assembly codes", and "family type

catalogs" functions in Revit. This step sets a base to

enable each physical component to map the cost

items that specify the construction materials used in

erecting the component.

Step 2: Conducting Searching Algorithms to

Perform Quantity Takeoffs

in Autodesk QTO.

The model proposes to apply the search takeoff tool

in Autodesk QTO to create takeoff objects (that is,

cost items associated with each activity) and then

quantify the objects. To specify the takeoff objects

needs to set search criteria first. The proposed search

algorithm defines various search criteria (floor,

physical object, cost item, and area) with respect to

different types of scheduling activities (structure,

site work, and finishes activities).

For example, the structure activities are such as

setting steel of 1st floor columns/walls, setting steel

of 1st floor beams/slabs, setting form of 1st floor

columns/walls, setting forms of 1st floor

beams/slabs, etc. Thus, in the structure activities, the

search criteria are floor (1st, 2nd, 3rd, etc.), physical

object (column, wall, beam, and slab), and cost item

(involved construction materials).

Specifically, for instance, activity “setting steel

of 1st floor columns/walls” includes two physical

components: columns and walls. Each component is

associated with two cost items, namely, “steel,

SD420, labor and material included” and “steel,

SD420W, labor and material included”. The takeoffs

of steel in this activity are performed in four steps:

ICSOFT-EA2015-10thInternationalConferenceonSoftwareEngineeringandApplications

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Figure 1: Proposed model.

• Step 2.1: In the search takeoff tool, use “1st

floor” (floor), “column” (physical component)

and “steel, SD420, labor and material included”

(cost item) as search criteria to retrieve all the

columns that use “steel, SD420, labor and

material included” and are located on the first

floor. The geometric parameters of columns are

used to quantity the column steel via takeoff

formulas.

• Step 2.2: Step 2.1 is repeated for the other cost

item (steel, SD420W, labor and material

included) of “column”.

• Step 2.3: Step 2.1 is repeated for "wall" and cost

item (steel, SD420, labor and material included).

• Step 2.4: the quantities of steel of “wall”, cost

item (Steel, SD420W, labor and material

included) are also obtain through the same

process.

Notably, several structure activities are

associated with the same cost items “steel, SD420,

labor and material included” and “steel, SD420W,

labor and material included”. Therefore, the example

here relates to a many-to-many relationship (i.e.,

many activities-to-two cost items).

Step 3: Mapping Contractual Unit Prices from

Cost Estimation Software.

After conducting step 2, the cost items associated

with quantity takeoffs in each activity are transferred

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to a cost estimation software (called Public

Construction Cost Estimation System or PCCES)

that is widely used in Taiwan. Via PCCES, the

contractual unit price of each cost item is retrieved

automatically. As a result, the costs of the cost items

in each activity can be computed.

Step 4: Converting to Excel to Build a S-curve.

The costs of each activity calculated in PCCES are

exported to a MS Excel file. Next, in an activity, the

costs are uniformly allocated in the activity duration

to obtain the daily costs. Notably, the activity costs

are related to direct costs. Indirect costs of a project,

such as safety and health fees, and quality control

fees, are assumed to be uniformly spread out the

entire project duration. Finally, the daily costs of

various activities in each day can be obtained,

resulting into the establishment of a progress curve

(or S curve) of the project.

4 CASE STUDY

4.1 Project Description

The case study concerns a project that involves a

high-tech related building in northern Taiwan. This

building built with RC has three upper-structure

floors and two underground-structure floors. The

total building floor area is 14,966 m2, and the

construction budget is approximately US$7.4

million. And the project contractual duration is 598

days. This project has an intermediate schedule

associated with 93 activities, in which the numbers

of structure, site work, and finishes activities, are 59,

9, and 25, respectively.

4.2 Evaluations and Results

First, a 3D BIM-based model was built using

Autodesk Revit Architecture, as shown in Fig. 2.

This BIM model is composed of physical

components and information parameters (including

additional geometric parameters and cost-item

parameters). This BIM model is then transferred to

Autodesk QTO to conduct quantity takeoffs.

In performing step 2, Fig. 3 presents a snap shot

of applying the search takeoff tool to quantify the

cost item, “steel, SD420, labor and material

included" of activity “setting steel of 1st floor

columns/walls”.

After going through the modeling steps 1~4, Fig.

4 displays the established S curve in the project.

Figure 2: Autodesk Revit model of case project.

Figure 3: Searching criteria in QTO.

4.3 Discussions

During the course of this case study, lessons learned

are summarized as follows.

• In establishing an S curve, if the duration of an

activity is too short (for example, one or two

weeks; the case of a detailed schedule), then

numerous activities will be involved, increasing

the computation effort in QTO. If the duration is

too large (for example, two or three month; the

case of a milestone schedule), the QTO effort is

much less, but the accuracy of an S-curve

decreases. Hence, this study recommends to use

an intermediate schedule.

• The search algorithm can reduce errors in

mapping the activities and cost items. However,

the current algorithm is still performed manually.

• An S curve is often done after the project

contract has been awarded, in which the

•

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10%

15%

20%

25%

30%

35%

40%

45%

50%

55%

60%

65%

70%

75%

80%

85%

90%

95%

100%

Project time

Figure 4: Established S curve of case project.

contractual quantities already exit. In a cost item,

if the overall quantity extracted by QTO differs

from the contractual quantity, one may need to

adjust the extracted quantity.

5 CONCLUSIONS

The relationships between scheduling activities and

cost items may be 1-to-1, many-to-1 or many-to-

many relations, which are very complicated to

specify the costs of each activity. This study

proposes a searching algorithm to conduct quantity

takeoffs in Revit QTO to facilitate calculate the

costs of each activity. To do so, the search algorithm

uses the "keynotes", "assembly codes", and "family

type catalogs" functions in Revit to connect the

activities and their corresponding cost items. Next,

the search algorithm defines different search steps

(using various searching criteria, such as "floor",

"physical object", "cost item", and "area") to identify

various cost items associated with different types of

activities (including structure, temporary, and

finishes activities). Then, the extracted quantities of

cost items associated with each activity is transferred

to a cost estimation software, which can provide the

unit prices of corresponding cost items for obtaining

the total cost of the activity. At last, integrating the

costs of activities and the schedule, a planned S

curve of a construction project can be established to

support schedule control.

A case study has shown the benefits of the

proposed search algorithm and model. Future

research directions are as follows. For instance,

some of the steps in conducting search algorithms

and modeling are not automated. Using API to

performing these steps automatically should improve

the user friendliness.

ACKNOWLEDGEMENTS

The authors would like to thank the Ministry of

Science and Technology in Taiwan (Contract No:

MOST 103-2622-E-009-022-CC3) for their financial

support. We also thank the Concord Tech Company

for their technical assistance regarding the use of

Autodesk software. We are also indebted to Ming-

Feng Yeh, Jang-Jeng Liu, Yuan-Yuan Cheng and

Ming-Tsung Lee for providing valuable information

and practical experience.

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