reffirodonverm.ga Key Terms Section , for guidance on estimating construction contingency. construction cost estimating from planning phases through modification of Construction Cost Estimate - The independent review processes. Estimating Building Costs Calin M. Popescu University of Texas at Austin Austin, Texas, U.S.A.. Kan Phaobunjong Turner Construction Company Houston.
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Building Materials & Construction Planning Textbook free. Pages·· MB·19, CONSTRUCTION COST ESTIMATING GUIDE for CIVIL WORKS. approximately estimate construction costs of future residential-commercial buildings. An estimate model consists of the cost analysis of completed construction. PDF | Building actors need accurate estimates in order to efficiently undertake the construction of buildings. The knowledge of real expected costs of construction.
The design and construction of a building is a team activity, and increasingly each activity and each type of specialty is supported and augmented by its own computer applications. Interoperability identifies the need to pass data between applications, and for multiple applications to jointly contribute to the work at hand.
Completing the Forecast: Characterizing and Communicating Uncertainty for Better Decisions Using
Interoperability eliminates the need to replicate data input that has already been generated, and facilitates smooth workflows and automation. Data exchanges between two applications are typically carried out in one of the four main ways listed below: Direct, proprietary links between specific BIM tools 2. Proprietary file exchange formats, primarily dealing with geometry 3. Public product data model exchange formats 4. XML-based exchange format Direct links provide an integrated connection between two applications, usually called from one or both application user interfaces.
While a direct linking of application is a runtime and binary interface, and exchange format is implemented as a file of human readable text format. In , an industry consortium was initiated to develop a class library for representing construction project information and facilitating project data exchange among software serving the AEC industry. The consortium was initially called Industry Alliance for Interoperability. In , the Alliance was renamed to International Alliance for Interoperability IAI and became a global standards-setting organization representing diverse constituencies including architects and engineers, software manufacturers, government agencies, contractors, building owners and product manufacturers IAI Website, IFC is a comprehensive data representation of the building model.
The IFC object descriptions deal with not only full 3D geometry but also relationships, process, material properties, cost, and other behavior data Hamilton et al. Integrating a CAD model with IFC enables the accurate geometric representation to be integrated with structural and behavior elements and facilitates linking with external applications. According to Khemlani AECbytes Website, , the IFC data model is likely to become the international standard for data exchange and integration within the building construction industries.
XML allows definition of the structure and meaning of some data of interest; that structure is called a schema. The different XML schemas support exchange of many types of data between applications. This creates more possibilities for BIM to be used by different participants during a construction project. Applications associated with BIM are discussed in section 3.
It is useful during the design phase, during actual construction and after the construction has been completed. BIM uses interoperability to enable the exchanging of information between different applications.
Interoperability, as discussed in section 3. Therefore, BIM could be used as a tool to help improve not only the construction process but it also helps to manage the facility after the construction is completed. Concept and Feasibility Study Before the owner approaches an architect, it is necessary to determine the size of the building, its functionalities and features that can be built within the budget and time constraints.
The goals and expectations could be achieved if the concept and feasibility study of the project are within the acceptable limitations. A rough sketch of building model built and linked to a cost database can be a tremendous assistance to an owner.
BIM could be used as an application to help owner during the concept and feasibility study. This reduces the amount of time and number of errors, while generating project drawings.
Also, when changes are made to a model, the drawings are updated and may be regenerated as soon as the modifications are made. The coordination of mechanical, electrical and plumbing MEP , architectural, and structural systems can be achieved through the fully integrated 3D models that BIM provide. Design time could be shortened and design errors and omissions can be reduced. Rework due to the design flaws could be avoided with this coordination of work. It also gives an earlier insight into the design problems and provides an opportunity for a design to be improved continuously.
It allows the designer to see if the design intent of the project has been achieved. The intent of the design is the arrangement of features and dimensions that has been specified at the conceptual design of the project.
Purposes of spaces and rooms can be visualized at an earlier stage of construction where changes can be made with little to no addition cost. Estimates that use conceptual BIM consisting of components can provide owners with quick feedback on various design scenarios. BIM provides quantity takeoff tools to create faster, better detailed, and more accurate estimates.
During the construction of a project, owners and estimators struggle with the ability to respond to design and requirement changes and to understand the impact of those changes on the overall project budget. By linking the design model to an estimating application, the project team can speed up the quantity takeoff and overall estimating process to get faster feedback on proposed design changes.
Improve Energy Efficiency and Sustainability The green building trend is leading many owners to consider the energy efficiency of their facilities and the overall environmental impact of their projects.
Sustainable building is good business practice and can lead to greater marketability of a facility. Building models provide several advantages over traditional 2D models due to the richness of object information needed to perform energy or other environmental analyses. Daylight analysis, glare, and solar heat gain are a few scenarios that help reduce the cost of operation for the facility. The parametric nature of the BIM model makes design changes easier and it automatically updates the necessary documentations.
Owners also pay the cost for construction delays or lengthy project durations, either in interest payments on loan, delayed rental income, or other income from sales of goods or products. The application of BIM to support coordination and prefabrication can result in improved field productivity, reduced field effort, and reductions in the overall construction schedule, which results in on-time delivery for the owner. BIM models can also be used to create a 4D model by adding the time dimension.
Owners and their service providers often encounter unforeseen conditions that even the best digital models cannot foresee. Teams using digital models are often in a better position to respond to unforeseen conditions.
Local Code Compliance Owners and their design teams must work with a variety of jurisdictions to ensure their facilities meet design, performance, and work place safety codes. Regulatory personnel also face challenges for ensuring compliance and conformance during design and construction. A potential benefit of a building information model is the ability to automatically analyze and check the model for code compliance. These errors are eliminated with the adaptation of virtual 3D model.
Clashes can be identified before the construction in the field begins. BIM shows exactly how the component will fit into the project. Necessary information for the component is provided within the model. Fabrication of components on site would be faster through better coordination, better connections, better assembly planning and training.
Lean Construction Lean construction is a way to design production systems to minimize waste of materials, time, and effort in order to generate the maximum possible amount of value Koskela et al. BIM maximizes the efficiencies by providing accurate model information and the material resources needed for the different stages of construction. It provides the basis for better planning and scheduling.
This helps ensure that labor, equipment, and material are ready at the job site when they are needed. Facility Operation and Management Systems BIM helps produce higher quality and maintainable infrastructure through interactive review of coordinated models. Interactive review of the model allows owners to virtually access and simulates maintenance procedures. BIM could be used to quickly populate a facility management database. Since BIM is updated throughout the construction of the project, it can also be used as the as- built plans that are used to manage the facility.
Maintenance work and impact to retrofits could be evaluated by using the visual and intelligent models to help facility managers. A model, which has been updated throughout the construction, is a tool with great accuracy for operating and managing the completed building. BIM can be used as an advanced facilities management tool. It could be used for an evacuation plan, fire protection simulation, thermal calculation and air-conditioning analysis Eastman et al.
The transition from early adoption of technology to the mainstream practice is expected in the near future. The future impact of BIM can be separated into different parties and participants. Architects and engineers will be able to explore different designs while keeping the cost and schedule of the project in check. Virtual reality will enable exploration of different environmental impact scenarios such as sun studies, wind analysis, and energy efficiency. Engineers will also be able to do the structural analysis aspect of the model.
Owners will be able to see 3D visualization of the project at an earlier stage. Change orders and material changes will be instantaneously updated throughout the model. BIM will allow faster and easier calculation of the construction cost. The collaboration of both designers and the contractors can help minimize delays during construction. Estimators are able to use the properties provided in the model to estimate the cost of construction.
Labor intensive tasks during estimating process can be simplified. BIM facilitates collaboration between project participants.
Interoperability also enables different applications to be developed. BIM delivers many significant benefits and tools for all participants during various phases of the project. This thesis will utilize BIM as a technology to develop a visual approach to construction cost estimating. Although there are technologies to assist with the cost estimating process, inefficiencies still abound.
During the process of construction cost estimating, the estimator must learn about the design and conditions of the project. A lot of data are needed to prepare an estimate.
Reviewing drawings, extracting information for quantity takeoff and looking up the latest cost information from the cost databases are tasks that estimators must accomplish. The latest findings in cognitive psychology, a branch of science that relates to how humans process information, will be examined for this purpose.
In addition to cognitive psychology, visualization technology can also help improve how humans understand and process information. Computer aided design CAD and building information modeling BIM , which have been discussed in Chapter 3, are two examples of how visualization is currently used in the construction industry.
Visualization is useful not only in the design process but also during the construction. This chapter will discuss cognitive theory along with virtual reality. According to visual computing theorists and dual processing theory, a basic way to effectively facilitate the connection between internal mind and external environment is to improve the visibility of the information embedded in the data. A good external representation will be one that links naturally to the internal representations that people are capable of forming, thereby supporting their overall cognitive process.
Using lines and symbols to represent the thoughts and ideas of engineers and designers often provides a more effective means of communicating these concepts than verbal descriptions Scribner and Anderson, According to Bertoline et al. There are three types of processors: Attention is needed to facilitate and control this cognitive system. Each processor has specific functions.
The perceptual processor senses, detects, and accepts inputs from the external world and stores parts of the input in the working memory. The cognitive processor interprets, manipulates and makes decisions about the inputs. The motor processor is responsible for interpreting cognitive decisions into physical actions. As stated earlier, the processors work with memory in order to process information. Capacity to store data is differed in two types of memory.
A chunk of data is a unit of information such as name. The capacity and retention of long-term memory is practically unlimited, however, retrieval of information can be difficult. It is very important to understand how the processors and memories work together.
Research in the field of cognitive science and human-computer interaction has shown limitations of human brain during the information-processing task. First, the user will not notice screen changes that fall within an interval of milliseconds. Second, the user cannot be expected to work with more than seven chunks of information simultaneously; displaying more chunks means the user will concentrate on some parts of the screen, ignoring other parts. Third, retrieval of information that is not expected to be in working memory will probably degrade both speed and accuracy during information processing.
This is very important for software developers to keep in mind during design of software such as an estimating program. According to Gardiner and Christie , realizing that designing for human- machine cognitive compatibility can help make a machine more acceptable and more useful to its intended user. The benefits of realizing the use of cognitive science in developing software are many.
Less training is needed to use the software, errors in using it are less likely, more complex operations can be carried out by more people, work can be done faster, and more interesting work can be done with little or no undesirable stress on the user Gardiner and Christie, The knowledge that users bring to the interaction and the way in which they develop their understanding will influence the ease of use of the software Hammond et al.
Whether it is to see if the designed building would fit in the surrounding environment or owner requirements have been fulfilled.
Estimating in Building Construction
One way to view a project during the design is by using virtual reality. Virtual reality is about creating acceptable substitutes for real objects or environments for training, entertainment, or design purposes Vince, ; Gutierrez, Vexo, and Thalmann, Virtual reality is about using computers to create images of 3D environments within which one can participate in real time and experience a sensation of being there Vince, ; McMenemy and Ferguson, ; Gutierrez, Vexo, and Thalmann, The presence could be found in the form of navigation and interaction.
The use of virtual reality is to immerse the user in the display Richards, Virtual reality requires real time graphics and a stereoscopic display that is used for producing the depth for 3D images. Commonly used technologies include but are not limited to head-mounted displays HMD , personal computers PC , workstations, cave automation virtual environments CAVE , large screen systems, and virtual tablets.
Interaction can be achieved using a tracking device, which may be integrated in the HMD itself, for tracking head and body movement. Data gloves can be used to track hand movements. Computer mice can be used to navigate and interact on the personal computer level.
These devices let the user point to and manipulate objects in the virtual scene Vince, ; Gutierrez, Vexo, and Thalmann, According to Richards and Vince , Virtual reality can be a model for other types of visualization systems and a test system for display and interactive techniques. The benefits of seeing a product as a true 3D object is immense, and the ability to explore different perspectives of the project before anything is built are immeasurable.
Designers will be able to explore different design alternatives to maximize value.
One advantage of using virtual reality in construction industry is its capability to represent complex building components as a three dimensional graphical object. This helps user to visualize a project better than with 2D drawings. Since virtual reality could be used to explore designs before they are built, engineers and designers can use the technology to visualize structures before actually building them McMenemy and Ferguson, In addition to visualizing buildings and structures, designers and engineers are also able to interact with them.
Engineers can use virtual reality in many applications, such as structural analysis and construction cost estimating. In this study, a virtual model of a project is created by extracting the geometry and material properties from each element in a CAD model. Microsoft DirectX Library is used to create a virtual environment using the extracted information.
Construction cost estimating can then be done by walking in the building and selecting elements in the virtual model for estimating. Next section will discuss interactive visualization in more detail. Virtual reality and interactive visualization can be used to perform estimating while navigate in a virtual model f the building.
Information could be extracted from the model during navigation. A cost estimating application is needed in order to use extracted information. The next chapter will discuss computer database technology and how a cost estimating database can be developed for an estimating application. These data need to be organized in a way that they can be easily accessed.
One way to solve the problem is to use a database for storage of the data. A database is a storage facility or a collection of related records or documents. Databases are designed, built, and populated with data for a specific purpose and has an intended group of users and some applications in which these users are interested Retik and Langford, The estimating software designed for visual estimating adopts database technology to store all the information necessary for estimating.
The cost estimating database will also be used to store new estimate information. This chapter will discuss why databases are used, database models especially the relational model, and how the estimating database used in this study was designed.
A database is an organization or a collection of related data. It is designed specifically to manage large bodies of information, and store data in an organized and structured manner that makes it easy for users to manage and retrieve data when required Agarwal et al. It is very much like a spreadsheet. However, a database is designed to perform some very specific tasks which a spreadsheet is not able to do effectively.
These are some of the reasons why databases are used Agarwal et al. Databases help in maintaining large amounts of data, and thus completely replace voluminous paper files. Searches for a particular piece of data or information in a database are much faster than sorting through piles of paper. It is a dull work to maintain files by hand; using a database completely eliminates such maintenance. Database systems can easily be updated and so provide accurate information all the time and on demand.
These models present three ways of logically perceiving the arrangement of data in the file structure Bagui and Earp, Following is a brief description of each database model. Hierarchical Database Model The hierarchical model represents data using hierarchical tree structures.
Each hierarchy represents a number of related records, arranged in multi-level structures, consisting of one root record and any number of subordinate levels Retik and Langford, This can be seen in Figure Hierarchical Database Model Network Database Model The network model was developed as a successor to the hierarchical model. The network model represents data as record types with more complex many-to-many relationships.
This allows flexibility in describing different structures and relationships. Figure shows how network model is arranged. Tables consist of a number of rows, each row containing the same number of columns Carter, A database based on the relational model was developed by E.
Codd during the s. A relational database allows the definition of data structures, storage, and retrieval operations and integrity constraints. Figure shows how data is viewed in the relational model. This is where data is kept within the database. System tables are special tables that SQL Server uses to help it work with the database.
These tables contain information within rows and columns. These provide a definition of each single item of information that builds up to a table definition. A column is made up of cells that all hold data. Each cell can hold a different type of data. Although they are restricted to what the data within it relates to, the type of data it will hold, and how much information can be stored in it.
Each table must have at least one column. A row is made up of one cell from every column defined for the table. There can be any number of rows in a table; the limitation is set by the disk space, the amount of disk space that was defined as the maximum in database creation definition, or the amount of disk space in the server. A row will define a single unit of information, such as, a person name, address, phone number, etc.
Rows are also called records. SQL or structured query language is database computer language designed for managing data in the relational database management systems. Stored procedures are permanently stored in the database, ready for use at any time. These can be regarded as predefined lists of information that can inform the database how the data is physically sorted and stored, or they can be used to find rows of data quickly using information supplied by a SQL query and matching this information to data within columns.
An index consists of one or more columns from the table it is defined for, but it is not possible for an index to cover more than one table.
Index is very much like the index of a book, which is used to locate a piece of information faster than looking through the book page by page. These can be thought of as virtual tables. Views can contain information combined from several tables and can present a more user- friendly interface to the data.
Views can also add a great deal of security to an application, but they do give reduced functionality over the use of stored procedures or direct access to the tables. Views can also be indexed to speed processing of data within.
Since in this study a relational database is used for keeping data for cost estimating purposes, it would not be a relational database at all if database relationship is not discussed. The following section will provide the definition of relationship in the relational database model and how it works with data. It is impossible to have a physical link, although a physical line is drawn between two database tables when graphically illustrating the structure of a database. The following sections present specific details about relationships, starting with a look at cardinalities.
Cardinalities Cardinality is a description of how many of one record type relate to the other, and vice versa. Mapping cardinalities, or cardinality ratios, express the number of entities to which another entity can be associated via a relationship set. Three main types of cardinality can exist in a database, these are; One-to-one, One-to-Many, and Many-to- Many. For each row in Table A, there is at most only one related row in Table B, and vice versa. This relationship is typically used to separate data by frequency of use to optimally organize data physically.
Typically, there is no real reason for one record in one table to match just one record in another. For example, one department can have only one department head. For example, a customer can have many orders, but an order can only belong to one customer. For each row in Table A, there are zero, one, or more related rows in Table B, and vice versa. Although it can happen relatively frequently, many-to-many relationship is not so easy to achieve.
It also requires a special technique to implement. This relationship is actually implemented in a one-many-one format, so it requires a third table often referred to as a junction table to be introduced in between that serves as the path between the related tables.
An example of a many-to- man relationship might be where an order can have many products and a product can belong to many orders. Now that all the cardinalities have been explained, keys will be discussed next. Keys Relationships are represented by data in tables.
To establish a relationship between two tables, data in one table must be related to rows of data in another table. A key is one or more columns of a relation that is used to identify a row. In relational database management system, it mainly works with two types of keys: Primary Keys A primary key is an attribute column or combination of attributes columns whose values uniquely identify records in an entity.
Before choosing a primary key for an entity, an attribute must have the following properties: Besides helping in uniquely identifying a record, the primary key also helps in searching records as an index automatically gets generated when assigning a primary key to an attribute.
Foreign Keys A foreign key is an attribute that completes a relationship by identifying the parent entity. Foreign keys provide a method for maintaining integrity in the data called referential integrity, this will be discussed in the following section and for navigating between different instances of an entity.
Every relationship in the model must be supported by a foreign key. Data Integrity Data integrity means that data values in a database are correct and consistent. There are two aspects to data integrity: This is to guarantee that primary key values exist for all rows.
The requirement that primary key values exist and that they are unique is known as entity integrity. Once a relationship is defined between tables with foreign keys, they key data must be managed to maintain the correct relationships to enforce referential integrity. Referential integrity requires that all foreign key values in a child table either match primary key values in a parent table or, if permitted, be null.
This is also known as satisfying a foreign key constraint. Normalization Normalization is a technique for avoiding potential update anomalies, basically by minimizing redundant data in a logical database design.
Normalized database designs usually reduce update processing costs but can make query processing more complicated. These trade-offs must be carefully evaluated in terms of the required performance profile of a database.
Often, a database design needs to be denormalized to adequately meet operational needs.
Normalizing a logical database design involves a set of formal processes to separate the data into multiple, related tables. The result of each process is referred to as a normal form.
Five normal forms have been identified in theory, but most of the time third normal form 3NF is as far as needed in practice.
This thesis will not get into detail about normal form. The cost estimating database will use 3NF. Now that all the necessary components of relational database have been described, cost estimating database will be described in the following section.
The ability to integrate this data into the estimating process would be beneficial during an estimate. A cost estimating database was developed to store all the data required for the estimating application developed in this study.
The application is named Visual Estimating Application. This section will present what should be stored in the cost estimating database, how the database was designed using the relational database model, and how the estimating data are related to each other. The cost of a building element is the sum of the costs of the work items necessary for the construction of the element.
The data needed for estimating include labor, equipment, material costs and productivities. Figure shows the schema of the database developed for storing the necessary data. The following will discuss each table in the cost estimating database. Labor Table: The labor table is used to keep data for each labor trade.
A code is assigned to each labor trade because it is easier to find a labor trade by code rather than searching by its description. Description attribute is used to store the name of the labor trade, and BaseHourlyRate attribute keeps the cost for each labor in the database. Figure shows a sample list of labor trades stored in the Labor table. Labor Table Equipment Table: Equipment table is used to store equipment-related data. Equipment data that is required to be stored in the equipment table include equipment code, equipment description, and equipment cost per day.
Similar to labor code, equipment code is uniquely assigned to each piece of equipment. This is to help make it easier to find equipment, rather than trying to find it by using equipment name.
Equipment cost per day reflects the rental cost per day for the equipment. However, the database in this study only stores the rental cost on the daily basis. Figure shows a list of equipment from the Equipment table in the cost estimating database.
Equipment Table Material Table: Material code is used similarly as labor code and equipment code where each material is assigned a code for easy access. Material description is provided in the description attribute. A unit for each material is also needed because different material can have different units of measurement. Cost of material is also displayed as cost per unit. Figure shows a list of materials in the Material table. Crew is related to both Labor and Equipment.
To make up a crew, there must be at least one or more labor and zero or more equipment.
The relationships between crew and labor tables and crew and equipment tables are many-to-many. This relationship is actually implemented in a one- many-one format, so it requires a third table, also known as a junction table, which serves as the path between the related tables. Crew table in Figure was created to keep crew data. Although it was only developed with one attribute, CrewCode, it is necessary and plays an important role by identifying both labor and equipment makeup for each crew.
This is to show that there are a number of laborers for that particular crew code. C-1, Carp, 3 row specifies that there are three carpenters in the C-1 crew and C-1, Clab, 1 row means there is one common laborer in the C-1 crew. Since there is no equipment for C-1 crew, no equipment row is entered. Item table is used to store information for different work items. Item code and item description define the work item. A code is a unique number that is used to provide easy access to each item.
Description is used to provide more information about the item. Each item has a unit which is used to define its quantity.
Each item has a crew that builds the item. Crew productivity rate is the rate that represents a typical number of units that the crew can install in a normal eight- hour day. Material attribute specifies the material code that is installed by the crew. Figure shows examples of items in the Item table. Item Table Assembly Table: Assembly code is used to uniquely identify an assembly. Assembly description provides the assembly with a definition. Image of the assembly is stored in the Picture attribute.
Since the relationship of assembly and item can be classified as many-to-many; one assembly can have many items, and one item can be included in many assemblies. For example, A — Concrete footing uses three items, so AssemblyCode and ItemCode are all indicated in the table.
Although there are several database models, the relational database model was adopted in this study. This chapter described the database schema, the structure of the tables in the estimating database and their relationships. It discusses various components of the application, the function of each component and how they are related to each other. Available methods, such as digitizing tablet and on-screen quantity takeoff, require manual inputs, albeit currently they are forefront technologies in construction cost estimating.
In a project where there are thousands of elements to be estimated, this proves to be tedious and very time consuming. To minimize the tedious process and provide visualization at the early stages of building process, a Visual Estimating Application VEA is developed to provide the connection between building information modeling and the process of construction cost estimating.
VEA not only does help in repeated calculations, summarizing and reporting, but it also helps extracting information from CAD models. The application of BIM and visualization technology in estimating makes it easier for estimators facing this task on a regular basis. This chapter discusses the objectives of VEA and an overview of its architecture. Since BIM contains information about the model, it has become increasingly important in both architectural and engineering practices.
For construction cost estimating, the geometry and properties of elements are necessary. This information can be extracted from BIM easily. In VEA, an estimator can see exactly the location and relationships among building elements while walking inside the building. Looking up cost information for estimating is also available from a custom database. VEA and its architecture will be discussed in the following sections.
The application and its components are shown in Figure These components will be discussed individually in the following sections. Using the extracted information and Microsoft DirectX graphics library, a virtual prototype of the project is created in the visualization module Van Verth and Bishop, , Karshenas, Section 6. The visualization module allows estimators to navigate and interact with the virtual environment.
First and third person cameras are developed for navigation while input devices are used to interact with the model. This will be discussed in further detail in section 6. Visual Estimating Application Architecture 6. Other integrations use database connectivity such as ODBC to translate between software programs.
Integration based on application programming interface or API offers a very close link between applications. Revit API allows independent software developers to create software programs that can access elements in the Revit model. Even individual Revit users and companies are taking advantage of the API to create their own custom tools and add-on modules Rundell, The visualization system module extracts not only element geometry, but also element material properties.
This module was designed with a custom graphics engine, full navigational control, and two-way communication with the CAD engine.
It was developed using Microsoft DirectX graphics library. Capabilities of the visualization system include Karshenas, Navigation in a visualization system model includes orbiting or flying over a model using a third person camera, or walking around and inside the model with a first person camera.
Both camera function and input devices are discussed in more details below. These properties can be encapsulated into a single entity commonly called virtual viewer or camera which allows the user to control which objects lie in his or her current view Pepke, , Van Verth and Bishop, Virtual viewer or a camera is a combination of the position of the eye and direction in which the viewer is looking.
This controls which object lies in the current view. As shown in Figure , the virtual camera in the 3D environment is defined by the following three vectors: Since they are orthogonal, by normalizing them, an orthonormal basis could be created. Using this basis together with the view position, a new frame relative to the world coordinate system could be specified. This is known as the view frame or view space. View Frame Relative to the World Frame. Visual Estimating Application uses mouse and keyboard to allow the user to navigate and interact with the 3D model.
Other input devices such as 3D mouse and game controller can be used to provide easier navigation as they have been used by many video games or other visualization application. Data gloves can also be used to interact with the model as the user can use them to move or grab objects in the virtual environment.
Chapter 5 provided an in depth discussion of the cost estimating database and its architecture. It accesses and uses both the cost estimating database and the visualization module. It also provides an interface for maintaining the estimating database.
Estimating module was developed for user-friendliness and simplicity. In order to successfully develop and implement the module, several guidelines were established. The guidelines are as follows Karshenas, These guidelines will allow fast access to the information necessary for preparing an estimate and eliminate a lot of repetitive and tedious estimating tasks. It includes an estimating module, a visualization module and a database. The visualization module is used to help the estimator navigate and interact with the project model.
The cost estimating database keeps all the cost data necessary for estimating. The next chapter will demonstrate the application applied to a simple cost estimating case. Step-by-step procedure will be provided along with screen shots taken from the application. There will be two parts in this case study: The database management part will discuss database access, adding to, editing, and deleting from the database. The visual estimating part will explain the procedure for extracting information from a Revit model, selecting an element for estimating, selecting an assembly from the cost database, reviewing the item quantities, summarizing and creating an estimate report.
After extraction, the user does not need the parent software Revit Architecture and the Revit model file. Revit Element Extractor 7. The main functions of this interface are discussed below. Navigation inside a 3D model is done by using the mouse and the keyboard. To move forward, the right key is pressed. To look around the building, the left key is pressed and the mouse is moved around to the desired direction. To look up and down, both left and right keys must be pressed together.
Element Selection: This enables users to select any element in a 3D model to be estimated. An element is highlighted after it has been selected.
One can use the database interface to add data to, edit, and delete data from the database. This will be shown in more detail in section 7. Figure shows where the button is located. Database Management Button in the Visualization Walk-Through Application After the user selects the database management button, a dialog box will appear with nine buttons representing nine different tables in the database.
Figure shows this dialog box along with the buttons that the estimator can select to organize each of the nine tables. Database Management Dialog Box The cost estimating database can also be access through the Visual Estimating Application via the management menu as shown in Figure The estimator can bring up a table by selecting its menu item.
An element can be matched to an assembly from the cost estimating database for pricing. Step-by-step description of the cost estimating module will be discussed in section 7. Users can choose whether to add, edit, or delete data from different tables in the cost estimating database.
After the button is clicked, textboxes are enabled for the user to input data into the database as can be seen in Figure Editing or Updating Data To edit or update data in the estimating database, data has to be selected first. The selection can be done using the data grid view that shows content from the database.
Selected data and its attributes are then shown in textboxes. Roof is selected and the update button is clicked. A dialog box will appear, as shown in Figure Asphalt roof picture was selected. A picture was also added. This is shown in Figure where an item in the dialog box is selected to be deleted.
An item is selected to be deleted. This section provides a step-by-step procedure to describe the visual method to construction cost estimating. Step 1: The Revit Architecture menu is customized for element information extraction. Step 2: Figure shows a few elements drawn in the visualization system. Model shown in the visualization system module.
Step 3: Selecting an Element for Estimating After a 3D model of a building is created in the visualization system, estimating can start by selecting an element from the model. In Select state, an element can be selected by clicking the element. When an element is selected, it will turn to a pink color. This can be seen in Figure where a wall has been selected.
A wall is selected using the walkthrough camera. Step 4: An estimating dialog box will appear with information regarding the selected element. Geometry information could include width, length, height, area, and volume depending on the kind of element that has been selected for estimating.
The estimator can then select the database assembly that matches the element for estimating. Figure shows an assembly is being selected for the selected element for estimating. Estimating dialog box shown during an assembly is being selected. Step 5: Clicking the Takeoff button shows a dialog box with items that are included in the assembly, as shown in Figure Each item has to be adjusted for the element being estimated. For example, number of bricks needed depends on the size of the brick used.
This can be done by selecting the property for the item. A dialog box will appear after the property has been selected. The estimator must also provide waste percentages for each item.
Different Items for the Assembly is shown in the dialog box. Step 6: Saving Items and item Quantities to the Database After items in the assembly have been adjusted, it can then be saved.
The estimator can choose whether to save the assembly in an existing project or a new project. If the estimator wants to save the element in an existing project, the application will check whether the element has already been estimated.
If the element has already been estimated, a warning will be pop-up and ask whether to replace the previously saved data. Step 7: Reviewing an Estimated Item and Creating an Estimating Report After all model elements have been estimated, the estimator can review the estimate by using the Review Dialog Box, as shown in Figure The estimator can edit the data in this dialog box before an estimate report is created.
Item Cost Estimating Summary Figure shows an estimate report. Estimate reports can be saved in PDF file format for future use. It also introduced the use of visualization in estimating. The developed application digitally transfers project information from a BIM model to the estimating application; this reduces the manual data entry which is a very time consuming process.
This study provided a visual approach for estimating that allows an estimator to walk inside a virtual building and select elements for estimating interactively. A visualization module is used to help the estimator navigate and interact with the model. A cost estimating database is used to store cost data for the Visual Estimating Application. Although several database models can be used for storing cost data, the relational database model was adopted in this study.
The visualization module uses Microsoft DirectX graphical library to generate a virtual prototype of the project. The Visual Estimating Application matches an element extracted from a Revit model to an assembly from the cost estimating database for preparing an estimate.
An estimate report could also be generated. Although some of the tedious estimating tasks have been eliminated, the estimator input is still a must.
Different project has different methods of construction and circumstances. Even though computers can assist some process during estimating, it could only do so much while judgment and experience of estimator is also needed. Visual Interface for Cost Estimating: Visual approach to construction cost estimating provides visual aids to the estimator, making the estimating process more intuitive and simple.
This application transfers the necessary information from a BIM model to the estimating software. This eliminates the tedious and time consuming process of manual data entry quantity takeoff. Visual Cost Estimating as an Educational Tool: The Visual Estimating Application can be used as an effective educational tool for students who have no experience in construction cost estimating.
This requires: Making access to cost estimating information intuitive and fast. Automating extraction of building element geometry and material from CAD models. Exposing student to as many actual construction operations as possible.
Foundation for Future Research and Improvements: This research provides a good foundation for developing not only an educational tool, but also a new way to approach cost estimating commercially. Future research and improvements for the Visual Estimating Application is provided in more detail in section 8.
The answer to this question will vary, depending on depth of analysis by students. Local city government's pertain to commercial and residential buildings, city streets, water, and sewer type projects. The owner generally is interested in the cost of major components of the project, rather than the cost of construction materials.
For example, if the estimated cost exceeds the owner's permissible budget, cuts must be made by eliminating a building, or parts of a building, rather than merely reducing the cubic yards of concrete or pounds of steel. During negotiations, the contractor will likely have to reformat the estimate to enable the owner to make decisions on how to derive a contract amount that matches available funds.
The contractor may unbalance the bid by decreasing the unit price of the under estimated quantity and increasing the cost of another bid item, resulting in increased cost to the owner. The contractor may underbid the job to win the contract, then look for change orders during construction to obtain additional money.
The reduced quantity of work may result in reduced profit for the contractor. The contactor may have an excessive number of over-sized equipment on the job, resulting in reduced profit.
The contractor may file a claim against the owner, which will cause legal expenses. Prepare a list of methods a contactor may use to obtain costs above the bid amount. The contractor may underbid the job to win the contract and then issue change orders for additional cost.
The contractor may file claims against the owner of the project.Equipment and Furnishings F: This would include the head office overheads and other common costs or non-project-specific costs.
Although there are technologies to assist with the cost estimating process, inefficiencies still abound. Jump to Page. A modern example of innovation in this regard is the introduction of microchips on tools and equipment. Sources of information would include the client.
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