DOI 10.1007/s12205-014-0455-9 pISSN 1226-7988, eISSN 1976-3808 www.springer.com/12205
Implementing Earned Value Management using Bridge Information Modeling
Mohamed Marzouk* and Mohamed Hisham**
Received September 4, 2012/Revised May 17, 2013/Accepted August 26, 2013/Published Online May 20, 2014
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Abstract
Building Information Modeling (BIM) has widely become an effective tool in engineering and construction fields. It could be used in: generating shop drawings; detecting clashes; estimating quantities; and controlling documents. Applying BIM technology on bridges is named Bridge Information Modeling (BrIM). Bridge Information Modeling (BrIM) is an intelligent representation of bridges since it contains all information needed about bridges through their whole lifecycle. This paper presents the use of Building Information Modeling in cost and time management of infrastructure bridges. BIM-based cost estimation application is presented which is capable to carry out approximate cost estimate; and detailed cost estimate. The application is designed in a flexible manner to be used with default values, or user defined values. Different performance measurement indexes are used in order to control the cost and schedule during execution phase of construction projects. This application integrates BIM with Earned Value (EV) concept to determine the project status at specific reporting date. A case study is presented to demonstrate the use of the developed modules.
Keywords: building information modeling, infrastructure bridges, bridge information modeling, cost estimate, time and cost control, earned value
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1. Introduction
Bridges are main infrastructures that constitute the trans- portation system. They are very important assets that connect and facilitate transportation between different areas across many barriers. Bridges represent a sizable portion in major highways projects and they require large investments. Engineering processes in bridge projects are always carried out in a conventional manner, such as: using normal electronic drafting (CAD) in creating shop drawings, performing manual quantity takeoffs and cost estimation, construction method selection based on project manager experience, manual controlling of documents, and conventional bridge management in operation and maintenance phase. Because of the large investments required by bridges, cost management must be applied to bridges in an effective and accurate manner.
Cost Management includes the processes involved in estimating, budgeting and controlling costs (PMI, 2008). Cost estimating is the process of predicting the costs of a project based on the required materials, labor and time constraints; it is critical in construction projects for both budgeting and scheduling (Sattineni and Bradford 2011). Cost Estimation can also be defined as a predictive process used to quantify, cost, and price the resources required by the scope of an asset investment option, activity, or project (Dysert, 2008). Different bridge cost
estimation models were developed (Fragkakis and Lambropoulos, 2004; Kim et al., 2009; Sirca and Adeli, 2005; Fragkakis et al., 2011). The obtained activity cost estimates are used in budgeting. Cost is then controlled during execution to complete project within the defined budget. This could be achieved by applying different techniques such as: Earned Value Manage- ment, and Variance Analysis (PMI, 2008). Earned Value is the most common performance measuring technique that integrates scope, schedule, and cost in one system, and it measures the performance of the project in terms of cash. By applying Earned Value technique at any date during project execution, the budget and schedule status could be determined, and thus, cost and schedule could be controlled in order to achieve project objectives. Khamidi et al. (2011) presented the implementation of Earned Value Management on a Malaysian infrastructure project. They proved that Earned Value Management facilitates the project team to carry-out more in-depth assessment of project status and predicts future performance trends as well.
Zawistowski (2010) presented a modification to Earned Value method through utilization of the Monte Carlo simulation method and the fuzzy logic theory for more complex risk analysis related to time and cost.
A Building Information Model (BIM) is a digital representa- tion of physical and functional characteristics of a facility. As such, it serves as a shared knowledge resource for information TECHNICAL NOTE
*Professor, Structural Engineering Department, Cairo University, Giza, Egypt; Adjunct Professor, Construction Engineering and Management Program, Nile University, Egypt (Corresponding Author, E-mail: [email protected])
**Graduate Student, Construction Engineering and Management Program, Nile University, Egypt (E-mail: [email protected])
about a facility forming a reliable basis for decisions during its lifecycle from inception onward. A basic premise of BIM is collaboration by different stakeholders at different phases of the life cycle of a facility to insert, extract, update or modify information in the BIM to support and reflect the roles of that stakeholder. The BIM is a shared digital representation founded on open standards for interoperability (NIBS, 2007). Building Information Modeling provides great benefits to all project parties. For the designer, BIM eases the creation of different design alternatives, and the designer can perform modifications to the design in a short time and with minimal effort. For the contractor, BIM reduces the site errors because of the early coordination between models and the better project visualization.
For the owner, an integrated Building Information Model is created at the end of the construction containing all information about the project. Building Information Modeling allows teams in different regions and countries to work together to create designs, solve problems, and complete projects faster (Marzouk et al., 2010). BIM has been applied in different fields related to engineering and construction. Goedert and Meadati (2008) integrated construction process documentation with BIM, while Sacks et al. (2010) presented the interaction between lean construction and BIM. Autodesk (2005) illustrated the use of BIM in sustainable design, and BIM. Sacks et al. (2009) presented BIM-based visualization to support lean construction.
Bridge Information Modeling (BrIM) has great effect on the improvements of the three main concerns of bridges stakeholders which are quality, schedule, and cost, and it is needed for bridges since it creates consistency in information in different phases from design to maintenance. BrIM can also be used in choosing suitable construction methods and planning site activities to avoid space conflicts (Marzouk et al., 2010). Bridge information modeling goes beyond traditional bridge design by fostering data reuse in different processes. So, 3D model of the bridge can serve as a window into the vast information asset, and organizations can begin to optimize business processes that cross the bridge lifecycle by more flexible access to information about the bridge (Peters, 2009). Chen et al. (2006) presented the benefits of 3D parametric bridge modeling compared to traditional 2D techniques. These benefits are: automated checking and coordination, compatibility with direct analysis, and full production support. Marzouk and Hisham (2011) integrated BrIM with the main modules of bridge management systems such as: database, inspection, and condition assessment modules in order to facilitate decision making regarding main- tenance and rehabilitation of infrastructure bridges. Marzouk and Hisham (2013) presented the integration of BrIM with Genetic Algorithms in order to optimize the locations of mobile cranes during the construction phase of bridges, taking into con- sideration existing conditions of site, surrounding areas, safety, and schedule constraints.
The 3D BIM model can be 4D model by connecting model elements to time schedules, and it can be 5D model by integrating cost estimation with model components. 5D feature is
considered a model-based cost estimating process that integrates the object attributes from the 3D model of the designer with the cost information from database of the estimator. Using the 3D model to estimate rather than the 2D drawings is not only quicker but also eliminates scope for errors and omissions (Tiwari et al., 2009).
Autodesk (2007) presented different methods of getting quantities and material definitions out of a Building Information Model into a cost estimating system. These methods include:
utilizing BIM Application Programming Interface (API), ODBC connectionto estimating programs, and output to Excel. Shen et al. (2007) explained that BIM models are not rich enough to cover the richer details of the real trade practices, and that they lack the mechanism to provide multiple trades views at various detailed levels. There are significant limitations when BIM applications are applied to generate detailed construction estimates due to the lack of a configurable construction knowledge base in BIM’s data model. BIM applications are able to generate accurate physical quantities of materials used in the design. However, due to the lack of context for construction methods and procedures, these material quantities cannot be used directly to generate labor and equipment quantities (Shen & Issa 2010). In order to overcome this problem, they applied BIM-Assisted Detailed Estimating (BADE) approach which allows estimators to apply their own domain-specific judgments to the design features with the assistance of 3D visualization and quantity data from BIM models. Marzouk and Hisham (2012) presented a methodology for using BrIM as an effective tool in performing cost estimates via a methodology that integrates visualization feature of BrIM with specific attributes of the BrIM model intelligent components. They developed a program using C# language in order to extract the visualization conclusions and other components’ attributes to MS Excel spreadsheet. This sheet assists in performing cost estimates, and reviewing the estimates. They also presented a methodology for generating cash flow and required payments by integrating the developed program with 4D feature of BrIM. This paper presents intelligent cost estimation and project control applications utilizing BrIM. The benefits of the developed applications compared to other current practices are:
• The developed applications are bridge-specific applications that consider the common bridge components, construction methods’ knowledge, and market prices.
• The developed cost estimation application is capable to perform estimates in two levels which are approximate, and detailed. Both levels could be utilized according to user preference either by using built-in database (construction knowledge) or user’s inputs.
• The developed project control application integrates BrIM with Earned value technique in order to measure project performance in two levels which are element level or task level considering defined control accounts.
• The developed applications save effort and time as they perform their functions in an automated manner directly from the BrIM model.
2. Proposed Brim Cost Estimation Application The presented BrIM methodology for cost estimation of infrastructure bridges includes two different modules. The first module is an approximate cost estimate module which depends on extracting quantities from BrIM model, and multiplying these quantities by their equivalent unit costs which could be either default values existing in this module, or inserted by the user.
The second module is a detailed cost estimation module which depends on integrating BrIM with bridge construction knowledge related to productivity of labors and equipment, materials’ costs, and rates of labors and equipment. This module allows the use of default construction knowledge, or user defined construction knowledge in two levels which are: element level, or project level. The default values of the approximate estimate module, and the construction knowledge of the detailed estimate module, are both considered as database of the developed cost estimation applications. The structure of this database was developed considering the common practice in tendering bridge projects in Egypt. The output of the two estimation modules is created in Excel Sheet presenting the bridge elements and their corresponding costs.
The development of the two modules required integration of existing software packages (such as Tekla Structures (2014), and MS Excel), and other created attributes and programs (using C#
programming language) as follows: creating new attributes for each element type in the commercially utilized BIM software that has been used in this research which is named Tekla Structures software. This was achieved by modifying
“objects.inp” file in Tekla Structures system, these modifications create new attributes’ tabs for elements in Tekla Structure software; and utilizing Application Programming Interface (API) of Tekla Structures software by using C# programming language in order to integrate intelligent attributes of BrIM model with bridge construction knowledge and create MS Excel estimate sheets (Appendix 1 presents part of the developed C# code).
Detailed description of the two modules is presented in the following sub-sections.
2.1 Approximate Estimate Module
In the approximate estimate module, any bridge is divided into two main portions which are: substructure, and superstructure.
The substructure includes: piles, pile caps or footings, piers, and abutments. The superstructure includes: beams, and slabs. The two main factors that constitute the approximate estimate module are: elements’ quantities, and unit costs. This module depends on extracting elements’ quantities from BrIM model and multiplying these quantities with their unit costs in order to obtain total cost of each element which is automatically written to MS Excel file in addition to other element properties. Fig. 1 shows the methodology used by the approximate estimate module to obtain cost estimates of bridges.
Each element in the BrIM model has different attributes such as:
length, width, height, material type, area, weight, volume, user
defined attributes, etc. In most cases of cost estimates, the element’s measuring unit (such as square meters, cubic meters, kilograms, etc.) required to be used in the approximate estimate varies according to the element type and material. The measuring units of different element types and materials are defined in the approximate estimate module. The substructure elements include:
piles (CFA (Continuous Flight Auger) or Bored), piers and abut- ments, and footings or pile caps. Piles, piers and abutments are modeled using Column Component in Tekla Structures. A new attribute was added to Column Component properties that allows the selection of the column type from three types which are: piers or abutments; CFA piles, and Bored piles. The module captures the column type, and then it extracts the Length attribute in case of piles (as the measuring unit used in cost estimate of piles is linear meters), while it extracts the Volume attribute in case of piers or abutments (as the measuring unit of piers and abutments is cubic meters). The footing or pile cap elements are modeled using Pad Footing Component. The module captures the Volume attribute of these elements (as the measuring unit of footings and pile caps is cubic meters).
The most common superstructure cross sections are: box sections, and slab and beam sections. The box section consists of: upper slab, webs, and bottom slab; while the slab and beam type consists of: single deck slab, and beams (which are precast beams in most cases). The module is designed to calculate the cost of the bridge superstructure by capturing the Surface Area of the upper slab in case of box sections, and the Surface Area of the single deck slab in case of slab and beam sections, and then the module multiplies the extracted surface area with unit cost which varies according to the construction method used. Eight construction methods are considered in this module which are:
stationary formwork on ground, stationary formwork on elevated Fig. 1. Approximate Estimate Module Methodology
platform, free cantilever using 2 travelers, free cantilever using 1 traveler, advanced shoring system, erecting using launching truss, erecting using cranes, and incremental launching. The module identifies the slab type based on the Slab Description property added to Slab Component in Tekla Structures. It also identifies the construction method based on the Construction Method property added to Slab Component. Fig. 2 shows the added properties to Slab Component in Tekla Structures software.
The approximate estimate module includes default unit costs for all the previous elements. These default unit costs were obtained from experts working in the field of bridge construction. The module has also a user interface that allows inserting user defined unit costs based on user preferences and market conditions. Fig. 3 shows the main user interface of the approximate estimate module. After defining the unit costs type (whether default or user defined); the module creates MS Excel cost estimate sheet. This sheet contains information of each element in separate row in addition to the element cost. The
included information are: element ID, which is a unique property; element type; element quantity; and element cost, which is obtained by multiplying the extracted quantity (based on element type) with its equivalent unit cost (either default or defined by user in the main user interface).
2.2 Detailed Estimate Module
The detailed cost estimation process is always a complex process as it requires extensive knowledge of productivity estimates of each element type, labor and equipment rates, and material costs, in addition to the quantities’ calculations of elements. Despite its complexity, the detailed cost estimation process gets accurate and reliable results than the approximate cost estimation process. The detailed estimate module presented in this paper facilitates the process of detailed estimation. It includes default bridge construction knowledge that is required to perform detailed cost estimate. The user has the choice to use the default knowledge or to add his/her own knowledge in two levels which are: project level, and element level. The productivity data utilized in the default construction knowledge was obtained based on interviews that had been conducted with engineers working in bridge engineering & construction fields.
The detailed estimate module performs an automated process that integrates the bridge construction knowledge with the elements’ quantities (or attributes) which is also extracted automatically from the BrIM model based on the element type.
Fig. 4 shows the methodology used by the detailed estimate module to perform cost estimation.
2.3 Bridge Construction Knowledge
The required bridge construction knowledge to perform detailed cost estimation varies according to the element type, and construction method. For the substructure, four types of elements Fig. 2. Added Properties to Slab Components in Tekla Structures
Fig. 3. Approximate Estimate Module
Fig. 4. Detailed Estimate Module Methodology
are taken into account, which are: Bored Piles; CFA Piles;
Footings or Pile Caps; and Piers or Abutments. Bored Piles, CFA Pile, and Piers or Abutments are all modeled using the Column Component in Tekla Structures. Therefore, customized new properties are created in the Column Component. This tab allows the user to select the element type (whether Bored Pile, CFA Pile, or Pier or Abutment). It also includes separate attributes for both cases (piers or abutments, or piles). In case of Bored Piles, the user has to select the soil type from two types which are: sand or clay soil; or rocks. In case of CFA Piles, the selection must be sand or clay soil as this type is not applicable to rocks (this type of piles is also limited to radii less than or equals to 80 cm). The previous mentioned attributes have to be set before considering the method of estimate (either using default knowledge or user defined knowledge). Example of the substructure knowledge is the Piles knowledge which includes: cost of excavating machine (LE/day); labors cost (LE/day); productivity of labors and excavating machine (L.M/day); concrete material cost (LE/m3);
steel reinforcement material cost (LE/kg); steel reinforcement labors productivity (kg/day); and steel reinforcement labors cost (LE/day). Based on this knowledge, the required quantities to be extracted from the BrIM model by the detailed estimate module are: Length; Volume; and Steel Reinforcement Weight.
For the superstructure elements, the detailed estimate module
takes into account two construction methods which are:
stationary formwork on ground, and erecting using cranes. The cross section type considered in the stationary formwork on ground method is the box section; while the cross section considered in the erecting using cranes method is the slab and beam section. The box section consists of upper slab, webs, and bottom slab; while the slab and beam section consists of precast beams, and cast in place single deck slab. Upper Slabs, Webs, Bottom Slabs, and Single Deck Slabs are all modeled using the Slab Component in Tekla Structures, so, a new properties tab was created in the Slab Component. This tab allows the user to select the slab type (Upper Slabs, Webs, Bottom Slabs, or Single Deck Slabs). This attribute has to be set before considering the method of estimate (either using default knowledge or user defined knowledge). Example of the superstructure knowledge is the Slabs knowledge which includes: productivity of formwork labors (m2/day); formwork labors cost (LE/day); concrete material cost (LE/m3); concrete pump cost (LE/day); steel reinforcement material cost (LE/kg); steel reinforcement labors productivity (kg/day); and steel reinforcement labors cost (LE/
day). Based on this knowledge, the required quantities to be extracted from the BrIM model by the detailed estimate module are: Volume; Surface Area; and Steel Reinforcement Weight.
The knowledge of substructure, and superstructure elements
Fig. 5. Detailed Estimate Module Main User Interface for Project Level
exists in the detailed estimate module with default values. The user can use his/her own values in two levels which are: project level;
and element level. In the project level, the user adds the values in a main single user interface according to the element type as shown in Fig. 5. For example, by adding user values to the Upper Slab type section presented in the user interface, these values will be applied to all elements in the model with the type “Upper Slab”. In the element level, the user adds the values to each element of the model in separate user interfaces according the element type. This could be valuable feature in case of elements having same type but different constructability due to any reasons. Fig. 6 shows separate user interfaces for different element types.
2.4 Creating Estimate Sheets
For each element, and based on the used knowledge, the detailed estimate module calculates material cost (e.g., concrete cost, and steel reinforcement cost), labor cost (e.g., formwork labor cost, and steel reinforcement labor cost), and equipment cost (e.g., crane cost, and concrete pump cost). It then creates MS Excel sheet containing the calculated costs of each element in addition to the element ID; element type; material cost; labor
cost; and equipment cost.
3. Performance Measurement using Earned Value Technique
Monitoring project schedule and expenses is a main task carried out by project managers. This monitoring allows the project manager to make decisions that controls the duration and costs of different activities in order to meet project objectives with respect to time and budget. In order to determine the status of the project schedule and budget at any date, performance measuring techniques must be applied. The most common performance measuring technique is called Earned Value (EV) Technique. The EV technique integrates scope, schedule, and cost in one system, and it measures the performance of the project in terms of cash. The main quantities used in EV technique are defined as follows (Nagrecha, 2002):
• Budgeted Cost of Work Scheduled (BCWS) or Planned Value (PV): The budget of work scheduled to be accomplished within a given time period.
• Budgeted Cost of Work Performed (BCWP) or Earned Fig. 6. Element Level User Interfaces
Value (EV): The budget of completed work within a given time period.
• Actual Cost of Work Performed (ACWP) or Actual Cost (AC): The actual cost incurred in accomplishing the work performed within a given time period.
The project budget status at any date is determined by calculating the Cost Variance (CV) based on the following equation:
(1) If CV > 0; the project is considered under budget, and if CV <
0; the project is considered over budget
The project budget status at any date could also be determined by calculating the Cost Performance Index (CPI) based on the following equation:
(2) If CPI > 1; the project is considered under budget, and if CPI <
1; the project is considered over budget
The project schedule status at any date is determined in terms of cash by calculating the Schedule Variance (SV) based on the following equation:
(3) If SV > 0; the project is considered ahead of schedule, and if SV < 0; the project is considered behind schedule.
The project schedule status at any date could also be determined in terms of cash by calculating the Schedule Performance Index (SPI) based on the following equation:
(4) If SPI > 1; the project is considered ahead of schedule, and if SPI < 1; the project is considered behind schedule.
4. Brim Performance Measurement Module This module utilizes the EV concept to measure the performance at any date. The module could be used in two levels which are: task level, and element level. In both levels, the user has to insert the current date in the main interface of the module (as shown in Fig. 7), while the planned and actual values insertion method varies from one level to another, as it is inserted in the existing Task Manager Module of Tekla Structures Software in case of task level, while it is inserted in a developed separate user interface of each element in case of element level.
The developed BrIM Performance Measurement Module considers a specific structure of control accounts. These control accounts are considered the common denominator where cost and time data could be acquired and maintained. Each task or element has to be assigned to a specific control account. The
structure of these control accounts consists of three main components. The first component is the Zone where the task or the element is being executed. This component could be represented by three characters which could be defined according to the user preference. The second component is the
CV=BCWP ACWP–
CPI BCWP
ACWP---
=
SV=BCWP BCWS–
SPI BCWP
BCWS---
=
Fig. 7. BrIM Performance Measurement Module
Fig. 8. Breakdown of Work Types (Packages)
Fig. 9. Example of Control Account Representation in the Devel- oped Model
work type or package that the task or the element could be categorized under. This component consists of five characters;
the first three characters are either “SUB”, representing that the task or the element belongs to the sub-structure, or “SUP”, representing that the task or the element belongs to the super- structure; the last two characters are numeric values representing the trades that the task or the element belongs to. The breakdown of the work types (packages) is shown in Fig. 8. The third component of the control account deals with the responsible contractor/sub-contractor. This component could be represented by three characters which could be defined according to the user preference. An example of control account dealing with pile construction by contractor “C15” in Zone number “A01” is shown in Fig. 9.
In the task level, the module deals with each task separately, where 4D feature of BrIM is applied. This feature depends on connecting the model objects with their related tasks in the time schedule. In order to achieve this feature, Task Manager Module of Tekla Structures is used. This module (Task Manager), allows the generation of time schedules by two different methods:
manual creation of tasks and sequencing, or importing schedules from other scheduling softwares; it also allows linking schedules with model components, and inserting planned and actual data.
For each task, the components of the control accounts are defined as task user attributes. BrIM Performance Measurement Module captures the control account components, planned dates, total planned task budget (planned workload), and percentage completed at the current date inserted by the user in the main interface. The BrIM Performance Measurement Module could also capture the actual cost/actual workload if defined in the task level. In case of not defining actual values in the task level, the actual values have to be inserted by the user in the control account level. The BrIM Performance Measurement Module then calculates EV parameters for each task or control account as per below equations.
BCWS is calculated based on the following equations:
When current date is later than planned finish date;
(5) When current date is earlier than planned finish date;
(6) BCWP is calculated based on the following equations:
(7) ACWP is calculated based on the following equation:
ACWP
= Actual Cost of task at current date (actual workload) (8)
The BrIM Performance Measurement Module calculates Cost Variance (CV), and Schedule Variance (SV) as presented in Eqs. (1) and (3), respectively, and it determines the budget status (under budget or over budget), and the schedule status (ahead of schedule or behind schedule). The BrIM Performance Measurement Module could be easily adjusted to calculate status of budget & schedule by using CPI and SPI as presented in Eqs. (2) and (4), and thus, forecasted Estimate at Completion (EAC) could be calculated based on the following equation:
(9) The BrIM Performance Measurement Module then creates MS Excel sheet that includes: task ID; task name; control account components; control account; BCWS; % completed; BCWP;
ACWP; CV; SV; budget status; and schedule status.
In the element level, a separate interface is used for each element. This interface (named “Earned Value”), is located in the user defined attributes of each element. This interface (as shown in Fig. 10), allows the user to insert the components of the control account. The work type (package) is selected from an option list containing the defined work types, while the zone and the contractor are inserted by the user. The user is also allowed to insert planned dates, actual dates, % completed, actual payments related to the element (if exist), and the method of calculating planned total cost. Two methods of calculating planned total cost exist in an option list. The first option is using the element quantity and defined unit cost by the user. In this case, for each element, the module extracts the element quantity directly from the BrIM model and multiplies it by the unit cost inserted by the user in the “Earned Value” interface. The second method is using the total element budget inserted by the user in the “Earned Value” interface. The module then performs EV calculations as defined in Task Level. The BrIM Performance Measurement Module then creates MS Excel sheet that includes: element ID;
element type; control account components; control account;
BCWS=Total Task Budget
BCWS
Current Date Planned Start–
( )
Planned Finish Planned Start–
( )
---×(Total Task Budget)
=
BCWP=%Completed×(Task Total Budget)
EAC Budget at Completion ---CPI
=
Fig. 10. Earned Value Interface on Element Level
BCWS; % completed; BCWP; ACWP; CV; SV; budget status;
and schedule status.
5. Case Study
This section presents the implementation of the presented modules on Abo-Diab bridge, located in Al-Buhayrah governorate, Egypt. The bridge length is 170 meters divided into three parts which are:
• Part 1: the length of this part is 75 meters divided into 3 equal spans. The superstructure is composed of 2 cast in place concrete box sections.
• Part 2: the length of this part is 45 meters. The superstructure is
composed of steel beams and bracings, and concrete deck slab.
• Part 3: the length of this part is 50 meters divided into 2 equal spans. The superstructure is the same as part 1.
The presented modules were implemented on part 3, which was modeled using Tekla Structures Software as shown in Fig. 11.
The Detailed Estimate Module was implemented on the upper slab of one span of one of the box sections slabs, and one pile cap (shown in Fig. 12). The created Excel sheet containing the cost estimate is shown in Fig. 13. The Approximate Estimate Module was implemented on the substructure of part 3, including piles, pile caps, piers, and abutment. The created Excel sheet is shown in Fig. 14.
The BrIM Performance Measurement Module was applied on this case study for the task level. The project time schedule was developed and linked to the model elements using Task Manager Module of Tekla Structures Software (as shown in Fig. 15). The control account components were defined for each task. The Planned Value (PV) of piles and pile caps activities are 331,500 LE and 405,000 LE, respectively. Given the percent completed for piles and pile caps are 100% and 25%, whereas, the actual payment for piles and pile caps
Fig. 11. BrIM Model of Part 3
Fig. 12. Different BrIM Model Elements Selected for Detailed Esti- mation
Fig. 13. Detailed Estimate Sheet of the Selected Elements
Fig. 14. Approximate Estimate Sheet
are 345,000 LE and 90,000 LE (see Fig. 16). By running BrIM Performance Measurement Module (Task Level); it captures the control account, planned, and actual information, then it performs the Earned Value calculations and determines the budget and schedule status. It then writes the results to MS Excel sheet as shown in Fig. 17.
Although the cost estimation modules presented in this paper facilitates the cost estimation process of bridges, it is limited to direct costs only which are: materials costs, labors costs, and equipment costs. It doesn’t take into account indirect costs such as: overheads, taxes, bonds, insurances; and contingency. The used construction knowledge could be expanded to include these indirect costs in order to obtain more accurate estimates.
6. Conclusions
The paper presented the application of Bridge Information Modeling (BrIM) in cost and time management of infrastructure bridges. The presented application is bridge-specific application that performs its function in an automated manner in order to perform cost estimates and measure performance at any date throughout the project execution. It is designed in a flexible manner to be used with default values, or user defined values. The paper presented cost estimation applications which consist of two modules. The first module is approximate estimate module. This module extracts the elements’ quantities directly from BrIM Fig. 15. Schedule Generation and Link to BrIM Model Elements
Fig. 16. Representing Earned Value Parameters in Task Manager Module
Fig. 17. Created Excel Sheet and EV Calculations
model based on the defined element measuring unit. The module then multiplies these quantities with their equivalent unit prices which exist in the module with default values, or with the unit prices defined by the user in the module user interface. The modules then creates Excel sheet including information and cost of each element. The second module is detailed estimate module.
This module depends on integrating construction knowledge with BrIM quantities extraction to obtain detailed estimates. This construction knowledge includes productivity estimates, different materials costs, and labors and equipment rates. It exists with default values or could be set by the user in the user interface in two levels which are element level, and project level. The modules creates Excel sheet including information, materials cost, labors cost, and equipment cost of each element. The detailed estimate module is limited to two construction methods of bridge superstructure which are: stationary formwork on ground, and erecting using cranes. The cross section type considered in the stationary formwork on ground method is the box section; while the cross section considered in the erecting using cranes method is the slab and beam section. The paper also presented BrIM Performance Measurement Module. This module works in two levels which are: task level and element level considering defined control accounts. On task level, the module utilizes Task Manager Module of Tekla Structures Software to extract planned and actual values, and then performs Earned Value calculations. The modules creates Excel sheet including task information, different Earned Value parameters, and budget and schedule status. On the element level, several user interfaces are available for each element, so that the user could add the planned and actual values of each element separately. The module utilizes this data to perform Earned Value calculations, and determine budget and schedule status. The module finally writes the results in Excel sheet. A case study was presented to demonstrate the presented modules.
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Appendix. Developed C# Code
