Construction Engineering and Infrastructure Management, Asian Institute of Technology, Bangkok, Thailand
Steve Rowlinson
Department of Real Estate and Construction, The University of Hong Kong, Hong Kong
Introduction
Safety is considered as one of the project’s success factors. Poor safety management may result in accidents that impact on human, economic, and legal issues. The human impact involves both physical and psychological pains suffered by worker and his family. The economic impacts increase direct and indirect costs of the organization. In addition, there is the legal impact that relates to a breach of safety regulations. Therefore, it is necessary to consider safety and health as a project success factor along with other project success factors, such as time, project and quality.
Safety management covers from planning to implementation. Safety planning must be conducted prior to a construction activity for determining safety measures needed. The planning is the first fundamental step for managing safety. However, there is a problem with the conventional safety planning in construction project management.
The problem is related with loose relationships of plans: safety plan, project scheduling, and project drawings that are in 2D representation. This problem causes difficulties in using and analysing safety plans. For this reason, Kartam (1997) integrated safety plan with project scheduling. However, project design (i.e., drawings) was not included in his study. Without integrating project design, safety engineer will have difficulties in visualizing how the site will look; and this is important in determining safety hazards occurring.
This paper discusses our 4DCAD-Safety research that aims to integrate 4DCAD (i.e., 3DCAD objects and project time schedule) and construction site safety plan for assisting users in analysing and utilizing safety plans in terms of what, when, where, and why a safety measure is needed. This paper explains how a 4DCAD-Safety application is designed, developed, and tested.
Construction safety planning
Safety planning plays its important roles in construction project management for reducing unnecessary cost and delays related to undesired accidents. Safety planning ensures that safety will be taken into account along with costs, schedules, quality and other important job goals.
Safety planning includes identifying all potential hazards and hazardous operations and safety measures. This safety planning can be enhanced into safety risk management system by adding more tasks: identifying safety hazards, classifying risks, controlling the risks and monitoring the implementation. Among these tasks, safety hazard identification is the most important, since failure to identify safety hazards means safety measures are not adequately investigated.
Safety planning is traditionally managed separately from project planning/scheduling task. However, there must be a method to link these planning tasks. There are two reasons for explaining why the link is important. First, the safety plans must be linked with the construction schedule because safety engineers need to identify when safety measures on the safety plans must be used. Secondly, the safety engineers have to use construction drawings for developing the safety plans because these drawings have the information related to why and where safety measures are chosen. Kartam (1997) has developed Integrated Knowledge Intensive System for Construction Safety and Health Performance Control (IKIS-Safety System) that integrates safety and health requirement (i.e., safety plan) into a CPM-based project schedule. This integration provides a way to manage safety and health performance proactively rather than reactively, and alert construction manager and all involved parties when reviewing the CPM schedule (MacCollum 1995: 130; Kartam 1997). IKIS-Safety system helps users to know when a safety measure (i.e., what) is used since it is integrated with project scheduling; however, IKIS-Safety does not support adequate information for analysis. In our study, we consider that providing adequate information for safety engineers to analyse a safety plan in terms of why, when, where a safety measure (i.e., what) is important.
In order to provide adequate information, integrating the safety plan with 4DCAD, i.e., 3D object plus scheduling, is crucial. The 3D object should be used because it provides What- You-See-Is-What-You-Get (WYSIWYG) benefit. In conventional construction project, most of the objects are represented using 2D drawings. Collier (1994) noted that this 2D representation is a bottleneck since engineers have to convert this drawing into 3D mental picture which is a tedious task. Since creating this 3D mental picture is already a tedious task, combining the 2D drawing with safety planning increases the difficulty. As a solution, 3D model computer representation can be adopted.
4DCAD technology for managing construction projects
Koo and Fischer (2000) defined Four-Dimensional Computer Aided Design (4DCAD) as a result of integrating 3D objects to the fourth dimension, time. The 3D and time integration allows users to run a visualization of the planned construction process of the project. The first idea was conceived in 1986–1987 when Bechtel collaborated with Hitachi Ltd to develop the Construction CAE=4D Planner software (Simons, 1988 cited in Rischmoller, 2000). The 4D model aims to overcome deficiencies of the traditional planning and control, such as bar charts and network diagrams, that do not effectively represent and communicate the spatial, temporal, and non-precedence information.
In conventional project planning, a contractor has to abstract the visual description of a project design into a textual description of activities and construction schedule. Later at the construction stage, engineers have to visually conceptualize the sequence of construction, and the 3D mental model of construction objects for construction purposes. In 4D environment, this tedious process is eliminated since the 4D model explicitly represents the relationship between the description of a facility (3D object) and the construction schedule (McKinney and Fischer, 1998).
4DCAD facilitates 3D construction products to be visualized along with construction processes on a computer screen therefore users need not to interpret construction products and processes in their minds. In other words, users can visualize the construction processes, as they would be actually carried out in reality. Potential benefits of 4DCAD have been extended by adding additional dimension, such as resources constraint management (Sripasert and Dawood, 2002), and nD-modelling (Rowlinson and Yates, 2003; Lee et al., 2004).
The benefit of 4DCAD can also be used for safety planning purposes in which the 4DCAD technology can be integrated with safety plan for providing safety engineers for analyzing what, when, where, and why a safety measure is needed. This integration is called 4DCAD-Safety.
4DCAD-Safety
System functionalities
4DCAD-Safety application is designed to facilitate safety engineers to analyse and utilize a safety plan. For this purpose, necessary information, i.e., 1) what safety measures are needed, 2) why, 3) where, and 4) when they are needed, must be provided. The information related with type of safety measures can be stored in a database, so that engineers can retrieve this information when they need it for planning safety measures in a project. When the engineers have to determine type of safety measures need to be used, their decision is influenced by two aspects: the physical condition of the project, represented in project designs; and the project progress, represented in a project schedule. The physical condition affects engineers’ decision in terms of where and why the safety measures are needed. Similar tasks conducted in different conditions may need different safety measures, e.g., constructing a column at the perimeter of a building has different hazard exposure compared to constructing a column at the centre of the building. This means safety engineers need to know where the safety measures will be used in order to analyse why they need to be used. The other aspect, project progress, also affects the reason for why a safety measure is needed because project progress may temporarily create different safety hazards.
In order to include what, why, where, and when aspects, the 4DCAD-Safety is equipped with three main components: 1) 4DCAD simulator, 2) safety library and plan, and 3) 4DCAD-Safety simulator. The 4DCAD simulator is used to simulate the project progress for a specific date. The safety library and plan are used to determine what types of safety measures are needed. Finally, the 4DCAD-Safety simulator is used to simulate specific safety measures chosen for a specific project progress. In other words, the simulation generates the project progress at a specific date and safety measures related; and this is useful for the engineers to analyse what safety measures are needed, why, when and where they are needed.
A case example for illustrating the 4DCAD-Safety is presented below.
4DCAD simulation. The 4DCAD simulation engine aims to generate, manipulate and simulate the 4DCAD model. Before generating the 4DCAD model of the whole project, all subschedules from the subcontractors need to be combined into one main schedule otherwise some construction products may not be shown during the simulation. Hence, the first feature provided in this function is to combine subschedules of subcontractors into a main schedule of a contractor. (Note: this feature is optional.)
The 4D simulation can be obtained by making the 3D objects visible or invisible according to the construction scheduling. Ongoing and completed 3D objects are set as visible while the rests are set as invisible. The ongoing objects are represented in blue colour, while the completed objects are in green.
Safety library and planning function. A safety plan contains safety measures to prevent accidents. In order to generate a safety plan, 4DCAD-Safety is equipped with two safety features: safety library and safety planning.
A safety library contains several safety data collected from regulatory standards and safety engineers’ experience, e.g., installing a guardrail to protect workers from falling from an open slab. Due to the nature of a library as a storage function, the safety library may have a lot of safety data; and this creates difficulties for a user to find the specific safety data in the safety library. For solving this problem, a keyword system is used to filter safety data. For example, when a user filters the safety library with the ‘Piling’ keyword, every safety data holding this keyword will be shown, such as 1) use earmuff, 2) use safety helmet, and 3) use eyes protection.
A safety plan is created by assigning the safety data, compiled from the safety library, into an activity. The relationship between construction task (or activity) and safety data is illustrated in Figure 1.
System architecture
4DCAD-Safety system architecture consists of four parts (see Figure 2): 1) MS ProjectTM, 2) AutoCADTM or AutoDesk Architecture DesktopTM, 3) Database, and 4) the 4DCAD-Safety application (i.e., an interface application). The construction project scheduling is created using MS ProjectTM software. The advantage of using MS ProjectTM is in its ability to export a schedule file to a database file using an ODBC (Open Database Connectivity) function; and therefore the construction schedule developed using MS Project can be easily converted into a MS Access database. The system database is designed to store three categories of data: 1) safety plan, 2) imported construction schedules, and 3) 3D objects group. For visualizing construction products, AutoCADTM software is used for developing the 3D computer objects as well as displaying them for 4D simulation purpose. Reasons for choosing AutoCAD or AutoDesk are: 1) it supports functions that can be accessed using programming languages, such as Visual Basic, and 2) this software is commonly used in the AEC industry. One important function for the purpose of 4D simulation is ‘visibility’ property of AutoCAD in which this property can be turned-off to hide an object, and turned-on to display an object. In addition, rendered images in the AutoCAD can be saved in DFX file which then can be open as 3D objects using WorldUpTM, a virtual reality software. Viewing 3D objects in World Up facilitates a better visualization since user is provided with sophisticated walkthrough mechanism to explore the 3D objects. The last part, 4DCAD-Safety interface, developed using Visual Basic programming language, aims to integrate the system database and AutoCADTM or AutoDeskTM. ADO technology that connects objects (e.g., a list box, a combo box, and so on) to the system database through MS Jet OLEDB 4.0 Provider is adopted in this application. In relation to the connection between the 4DCAD-Safety interface and AutoCADTM, this study utilized ActiveX technology to control every object, method, property, and event of AutoCADTM.
Database design. The 4DCAD-Safety system database was developed using a relational database by using MS Access application. Its data can be mainly categorized into three main groups: products, processes, and safety plan. Figure 3 illustrates the database structure of 4DCAD-Safety system that consists of main tables (i.e., entities): ‘Group’, ‘4DLink’, ‘Task’, ‘SafetyLink’, ‘SafetyLibrary’, and ‘SafetyKeyword’.
‘Task’ table is needed to store main scheduling data from the MS project: TaskID, WBS, Task Name, Start Date, and Finish Date. From MS project schedule, this data must be exported to a MS Access database file. All construction activities in the MS Access database must be assigned into groups because some of the activities are not represented in the 3D models. For example, constructing column activity is usually elaborated into four activities: installing rebar, installing formwork, concreting, and stripping off the formwork; and this four activities can be grouped together to represent ‘constructing column’ activity which is linked into a 3D model of the column (see Figure 3). In order to group tasks from the ‘Task’ table and assign them to relate with a group of 3D objects, an additional entity so called 4Dlink table is created. In this 4Dlink, the relationship between ‘Group’ and ‘Task’ table is set as ‘a group can contain many tasks, but one task can be a part of a group only’.
The ‘Group’ table stores data of 3D objects such as group name, WBS, and work area. One group might contain one or more 3D objects that are similar and must be built at the same time, for example, a group of second floor slabs, which represent slabs from different areas.
In relation to safety planning, the ‘SafetyLibrary’ table is created as the library of safety data. It stores records of predefined safety measures collected from regulatory standard and safety engineers’ experience. For example, install a guardrail to protect workers to fall from an open slab. This safety library is used to create a safety plan stored in a composite entity, ‘SafetyLink’ table. This table relates several safety data in the library with a construction task in ‘Task’ table. This enables safety measures in a safety plan to be displayed along with construction products and construction processes being simulated in the 4D simulation. For example, the roof truss installation task needs some safety measures such as equipping a safety helmet, and providing a safety belt. When the 4D simulation reaches roof objects (construction products) and roof truss installation tasks (construction processes), these safety measures will be displayed.
The last table, ‘Safety Keyword’ aims to assist users to list the specific records of safety library based on their keywords, e.g., list all records of safety library related to a task, then users can choose suitable safety measures displayed. For example, when the users use ‘excavation’ keyword, the database will suggest safety helmet and install a temporary shoring, then the user may choose which measures are suitable.
4DCAD-Safety interface. The 4DCAD-Safety interface, developed using Visual Basic programming language, is designed for integrating system database and AutoCADTM or AutoDeskTM. The interface is mainly divided into three parts: 1) 4DCAD interface (see area 1 in Figure 4), 2) safety interface (see area 2 in Figure 4), and 3) viewing part (see area 3 in Figure 4).
The 4DCAD interface is designed for controlling the 4D components consisting of object groups, related tasks, and lists of tasks for providing the 4D generating function and the simulation function. The 4D generating function aims to generate relationships between the object groups and their related tasks, while the simulation function aims to run 4DCAD-Safety simulation. These two functions are the main objective of this application.
The safety interface is created for communicating a safety plan to user when its related 4DCAD model is being simulated (i.e., being constructed in real world). Moreover it also enables a user to develop a new or modify an existing safety library as well as integrate safety plans with 4DCAD model.
The viewing part, AutoCADTM or AutoDeskTM application, is to display 3D objects and 4D simulation. Each interface is designed to work consistently with others. For example, when, according to the scheduling, fourth columns are on being constructed (in the section 1 of Figure 4), the viewing part will display the columns being constructed (in the section 2 of Figure 4) as well as the safety measures related (in the section 2 of Figure 4).
The 4DCAD system can be further expanded into a virtual reality visualization by exporting the simulated 3DCAD into a virtual reality object (Figure 5). User can easily does a walkthrough to any location in the simulated construction progress. This virtual reality visualization can magnify the benefits of 4DCAD safety in terms of analysing and interpreting safety measures in terms of what, why and where the measures are needed. In addition, the visualization can also be used as a material for group discussion within safety engineers for safety knowledge socialization.
Introduction
Safety is considered as one of the project’s success factors. Poor safety management may result in accidents that impact on human, economic, and legal issues. The human impact involves both physical and psychological pains suffered by worker and his family. The economic impacts increase direct and indirect costs of the organization. In addition, there is the legal impact that relates to a breach of safety regulations. Therefore, it is necessary to consider safety and health as a project success factor along with other project success factors, such as time, project and quality.
Safety management covers from planning to implementation. Safety planning must be conducted prior to a construction activity for determining safety measures needed. The planning is the first fundamental step for managing safety. However, there is a problem with the conventional safety planning in construction project management.
The problem is related with loose relationships of plans: safety plan, project scheduling, and project drawings that are in 2D representation. This problem causes difficulties in using and analysing safety plans. For this reason, Kartam (1997) integrated safety plan with project scheduling. However, project design (i.e., drawings) was not included in his study. Without integrating project design, safety engineer will have difficulties in visualizing how the site will look; and this is important in determining safety hazards occurring.
This paper discusses our 4DCAD-Safety research that aims to integrate 4DCAD (i.e., 3DCAD objects and project time schedule) and construction site safety plan for assisting users in analysing and utilizing safety plans in terms of what, when, where, and why a safety measure is needed. This paper explains how a 4DCAD-Safety application is designed, developed, and tested.
Construction safety planning
Safety planning plays its important roles in construction project management for reducing unnecessary cost and delays related to undesired accidents. Safety planning ensures that safety will be taken into account along with costs, schedules, quality and other important job goals.
Safety planning includes identifying all potential hazards and hazardous operations and safety measures. This safety planning can be enhanced into safety risk management system by adding more tasks: identifying safety hazards, classifying risks, controlling the risks and monitoring the implementation. Among these tasks, safety hazard identification is the most important, since failure to identify safety hazards means safety measures are not adequately investigated.
Safety planning is traditionally managed separately from project planning/scheduling task. However, there must be a method to link these planning tasks. There are two reasons for explaining why the link is important. First, the safety plans must be linked with the construction schedule because safety engineers need to identify when safety measures on the safety plans must be used. Secondly, the safety engineers have to use construction drawings for developing the safety plans because these drawings have the information related to why and where safety measures are chosen. Kartam (1997) has developed Integrated Knowledge Intensive System for Construction Safety and Health Performance Control (IKIS-Safety System) that integrates safety and health requirement (i.e., safety plan) into a CPM-based project schedule. This integration provides a way to manage safety and health performance proactively rather than reactively, and alert construction manager and all involved parties when reviewing the CPM schedule (MacCollum 1995: 130; Kartam 1997). IKIS-Safety system helps users to know when a safety measure (i.e., what) is used since it is integrated with project scheduling; however, IKIS-Safety does not support adequate information for analysis. In our study, we consider that providing adequate information for safety engineers to analyse a safety plan in terms of why, when, where a safety measure (i.e., what) is important.
In order to provide adequate information, integrating the safety plan with 4DCAD, i.e., 3D object plus scheduling, is crucial. The 3D object should be used because it provides What- You-See-Is-What-You-Get (WYSIWYG) benefit. In conventional construction project, most of the objects are represented using 2D drawings. Collier (1994) noted that this 2D representation is a bottleneck since engineers have to convert this drawing into 3D mental picture which is a tedious task. Since creating this 3D mental picture is already a tedious task, combining the 2D drawing with safety planning increases the difficulty. As a solution, 3D model computer representation can be adopted.
4DCAD technology for managing construction projects
Koo and Fischer (2000) defined Four-Dimensional Computer Aided Design (4DCAD) as a result of integrating 3D objects to the fourth dimension, time. The 3D and time integration allows users to run a visualization of the planned construction process of the project. The first idea was conceived in 1986–1987 when Bechtel collaborated with Hitachi Ltd to develop the Construction CAE=4D Planner software (Simons, 1988 cited in Rischmoller, 2000). The 4D model aims to overcome deficiencies of the traditional planning and control, such as bar charts and network diagrams, that do not effectively represent and communicate the spatial, temporal, and non-precedence information.
In conventional project planning, a contractor has to abstract the visual description of a project design into a textual description of activities and construction schedule. Later at the construction stage, engineers have to visually conceptualize the sequence of construction, and the 3D mental model of construction objects for construction purposes. In 4D environment, this tedious process is eliminated since the 4D model explicitly represents the relationship between the description of a facility (3D object) and the construction schedule (McKinney and Fischer, 1998).
4DCAD facilitates 3D construction products to be visualized along with construction processes on a computer screen therefore users need not to interpret construction products and processes in their minds. In other words, users can visualize the construction processes, as they would be actually carried out in reality. Potential benefits of 4DCAD have been extended by adding additional dimension, such as resources constraint management (Sripasert and Dawood, 2002), and nD-modelling (Rowlinson and Yates, 2003; Lee et al., 2004).
The benefit of 4DCAD can also be used for safety planning purposes in which the 4DCAD technology can be integrated with safety plan for providing safety engineers for analyzing what, when, where, and why a safety measure is needed. This integration is called 4DCAD-Safety.
4DCAD-Safety
System functionalities
4DCAD-Safety application is designed to facilitate safety engineers to analyse and utilize a safety plan. For this purpose, necessary information, i.e., 1) what safety measures are needed, 2) why, 3) where, and 4) when they are needed, must be provided. The information related with type of safety measures can be stored in a database, so that engineers can retrieve this information when they need it for planning safety measures in a project. When the engineers have to determine type of safety measures need to be used, their decision is influenced by two aspects: the physical condition of the project, represented in project designs; and the project progress, represented in a project schedule. The physical condition affects engineers’ decision in terms of where and why the safety measures are needed. Similar tasks conducted in different conditions may need different safety measures, e.g., constructing a column at the perimeter of a building has different hazard exposure compared to constructing a column at the centre of the building. This means safety engineers need to know where the safety measures will be used in order to analyse why they need to be used. The other aspect, project progress, also affects the reason for why a safety measure is needed because project progress may temporarily create different safety hazards.
In order to include what, why, where, and when aspects, the 4DCAD-Safety is equipped with three main components: 1) 4DCAD simulator, 2) safety library and plan, and 3) 4DCAD-Safety simulator. The 4DCAD simulator is used to simulate the project progress for a specific date. The safety library and plan are used to determine what types of safety measures are needed. Finally, the 4DCAD-Safety simulator is used to simulate specific safety measures chosen for a specific project progress. In other words, the simulation generates the project progress at a specific date and safety measures related; and this is useful for the engineers to analyse what safety measures are needed, why, when and where they are needed.
A case example for illustrating the 4DCAD-Safety is presented below.
4DCAD simulation. The 4DCAD simulation engine aims to generate, manipulate and simulate the 4DCAD model. Before generating the 4DCAD model of the whole project, all subschedules from the subcontractors need to be combined into one main schedule otherwise some construction products may not be shown during the simulation. Hence, the first feature provided in this function is to combine subschedules of subcontractors into a main schedule of a contractor. (Note: this feature is optional.)
The 4D simulation can be obtained by making the 3D objects visible or invisible according to the construction scheduling. Ongoing and completed 3D objects are set as visible while the rests are set as invisible. The ongoing objects are represented in blue colour, while the completed objects are in green.
Safety library and planning function. A safety plan contains safety measures to prevent accidents. In order to generate a safety plan, 4DCAD-Safety is equipped with two safety features: safety library and safety planning.
A safety library contains several safety data collected from regulatory standards and safety engineers’ experience, e.g., installing a guardrail to protect workers from falling from an open slab. Due to the nature of a library as a storage function, the safety library may have a lot of safety data; and this creates difficulties for a user to find the specific safety data in the safety library. For solving this problem, a keyword system is used to filter safety data. For example, when a user filters the safety library with the ‘Piling’ keyword, every safety data holding this keyword will be shown, such as 1) use earmuff, 2) use safety helmet, and 3) use eyes protection.
A safety plan is created by assigning the safety data, compiled from the safety library, into an activity. The relationship between construction task (or activity) and safety data is illustrated in Figure 1.
System architecture
4DCAD-Safety system architecture consists of four parts (see Figure 2): 1) MS ProjectTM, 2) AutoCADTM or AutoDesk Architecture DesktopTM, 3) Database, and 4) the 4DCAD-Safety application (i.e., an interface application). The construction project scheduling is created using MS ProjectTM software. The advantage of using MS ProjectTM is in its ability to export a schedule file to a database file using an ODBC (Open Database Connectivity) function; and therefore the construction schedule developed using MS Project can be easily converted into a MS Access database. The system database is designed to store three categories of data: 1) safety plan, 2) imported construction schedules, and 3) 3D objects group. For visualizing construction products, AutoCADTM software is used for developing the 3D computer objects as well as displaying them for 4D simulation purpose. Reasons for choosing AutoCAD or AutoDesk are: 1) it supports functions that can be accessed using programming languages, such as Visual Basic, and 2) this software is commonly used in the AEC industry. One important function for the purpose of 4D simulation is ‘visibility’ property of AutoCAD in which this property can be turned-off to hide an object, and turned-on to display an object. In addition, rendered images in the AutoCAD can be saved in DFX file which then can be open as 3D objects using WorldUpTM, a virtual reality software. Viewing 3D objects in World Up facilitates a better visualization since user is provided with sophisticated walkthrough mechanism to explore the 3D objects. The last part, 4DCAD-Safety interface, developed using Visual Basic programming language, aims to integrate the system database and AutoCADTM or AutoDeskTM. ADO technology that connects objects (e.g., a list box, a combo box, and so on) to the system database through MS Jet OLEDB 4.0 Provider is adopted in this application. In relation to the connection between the 4DCAD-Safety interface and AutoCADTM, this study utilized ActiveX technology to control every object, method, property, and event of AutoCADTM.
Database design. The 4DCAD-Safety system database was developed using a relational database by using MS Access application. Its data can be mainly categorized into three main groups: products, processes, and safety plan. Figure 3 illustrates the database structure of 4DCAD-Safety system that consists of main tables (i.e., entities): ‘Group’, ‘4DLink’, ‘Task’, ‘SafetyLink’, ‘SafetyLibrary’, and ‘SafetyKeyword’.
‘Task’ table is needed to store main scheduling data from the MS project: TaskID, WBS, Task Name, Start Date, and Finish Date. From MS project schedule, this data must be exported to a MS Access database file. All construction activities in the MS Access database must be assigned into groups because some of the activities are not represented in the 3D models. For example, constructing column activity is usually elaborated into four activities: installing rebar, installing formwork, concreting, and stripping off the formwork; and this four activities can be grouped together to represent ‘constructing column’ activity which is linked into a 3D model of the column (see Figure 3). In order to group tasks from the ‘Task’ table and assign them to relate with a group of 3D objects, an additional entity so called 4Dlink table is created. In this 4Dlink, the relationship between ‘Group’ and ‘Task’ table is set as ‘a group can contain many tasks, but one task can be a part of a group only’.
The ‘Group’ table stores data of 3D objects such as group name, WBS, and work area. One group might contain one or more 3D objects that are similar and must be built at the same time, for example, a group of second floor slabs, which represent slabs from different areas.
In relation to safety planning, the ‘SafetyLibrary’ table is created as the library of safety data. It stores records of predefined safety measures collected from regulatory standard and safety engineers’ experience. For example, install a guardrail to protect workers to fall from an open slab. This safety library is used to create a safety plan stored in a composite entity, ‘SafetyLink’ table. This table relates several safety data in the library with a construction task in ‘Task’ table. This enables safety measures in a safety plan to be displayed along with construction products and construction processes being simulated in the 4D simulation. For example, the roof truss installation task needs some safety measures such as equipping a safety helmet, and providing a safety belt. When the 4D simulation reaches roof objects (construction products) and roof truss installation tasks (construction processes), these safety measures will be displayed.
The last table, ‘Safety Keyword’ aims to assist users to list the specific records of safety library based on their keywords, e.g., list all records of safety library related to a task, then users can choose suitable safety measures displayed. For example, when the users use ‘excavation’ keyword, the database will suggest safety helmet and install a temporary shoring, then the user may choose which measures are suitable.
4DCAD-Safety interface. The 4DCAD-Safety interface, developed using Visual Basic programming language, is designed for integrating system database and AutoCADTM or AutoDeskTM. The interface is mainly divided into three parts: 1) 4DCAD interface (see area 1 in Figure 4), 2) safety interface (see area 2 in Figure 4), and 3) viewing part (see area 3 in Figure 4).
The 4DCAD interface is designed for controlling the 4D components consisting of object groups, related tasks, and lists of tasks for providing the 4D generating function and the simulation function. The 4D generating function aims to generate relationships between the object groups and their related tasks, while the simulation function aims to run 4DCAD-Safety simulation. These two functions are the main objective of this application.
The safety interface is created for communicating a safety plan to user when its related 4DCAD model is being simulated (i.e., being constructed in real world). Moreover it also enables a user to develop a new or modify an existing safety library as well as integrate safety plans with 4DCAD model.
The viewing part, AutoCADTM or AutoDeskTM application, is to display 3D objects and 4D simulation. Each interface is designed to work consistently with others. For example, when, according to the scheduling, fourth columns are on being constructed (in the section 1 of Figure 4), the viewing part will display the columns being constructed (in the section 2 of Figure 4) as well as the safety measures related (in the section 2 of Figure 4).
The 4DCAD system can be further expanded into a virtual reality visualization by exporting the simulated 3DCAD into a virtual reality object (Figure 5). User can easily does a walkthrough to any location in the simulated construction progress. This virtual reality visualization can magnify the benefits of 4DCAD safety in terms of analysing and interpreting safety measures in terms of what, why and where the measures are needed. In addition, the visualization can also be used as a material for group discussion within safety engineers for safety knowledge socialization.
Testing and evaluations
Respondents’ opinions
In order to validate that the system can achieve the system objectives and benefits the construction industry, tests were conducted by two senior project managers and one senior project management consultant. The testers used the 4DCAD-Safety application, and then they were asked to answer a structured questionnaire. The questionnaire addressed two main issues: functionality, usefulness of the 4DCAD-Safety; and operability, easiness to use the system.
From Table 1, the result showed that the application is useful to assist users in analyzing construction sequence, informing spatial information and scheduling information. Moreover, the respondents were very satisfied with the application that provides them information to analyse safety planning information in terms of what, when, where and why safety measures are needed. They also considered that the application is relatively easy to use, except for generating a 4DCAD model. Generating the 4DCAD model is not easy because 1) it is difficult to develop a 3D model of a large-scale construction project, and 2) the process to link a construction scheduling and the 3D model is quite difficult. This is addressed for further research development.
System benefits and limitations
4DCAD-Safety provides general and specific benefits. The general benefits are related with the 4DCAD simulation features that have been investigated by previous researches. The specific benefits are uniquely related with the 4DCAD-Safety developed in our research.
The general benefits of 4D simulation are 1) the 4DCAD-Safety application visualizes 3D objects of a construction project, the disparity in participants’ experience or knowledge that lead to different interpretation is less significant and communication among participants can be improved (Koo and Fischer, 2000), and 2) the application can be applied to visualize and interpret construction sequence on a computer display rather than in their mind. This allows users to better understand construction sequence and detect potential problems in construction drawings as well as schedules prior construction starts (McKinney and Fischer, 1998; Kang et al., 2002).
There are two specific benefits related to the 4DCAD-Safety application. First, related with safety planning function, when construction activities are progressing according to the project calendar, the application can display safety measures that are required to carry out specific works. Secondly, since the displayed safety plan is related to the construction activities represented in 3D model, the application facilitates safety engineers to visualize spatial and physical information of construction activities and their products. This facilitates safety engineers to know and analyse what safety measures are needed to be installed, prepared, or provided for current activities and where, when, as well as why they are needed. For a better quality of visualization, 3D image rendered in AutoCAD can be saved as DFX file since this file format can be opened using World UpTM. One significant benefit of viewing 3D objects in World Up is that user can have a better walkthrough mechanism for exploring the objects (Hadikusumo and Rowlinson, 2001; 2003). As an additional benefit, the 4DCAD-Safety application has a feature for combining subcontractors’ schedules and a contractor’s schedule as well as their safety plans. This combination allows all safety plans from one organization to be communicated to other organizations since they might interact directly or indirectly in order to perform their jobs.
There are two limitations of the system: 1) the 4DCAD uses early start and finish for the simulation purposes. This must be further researched to include late start and finish, and 2) the 4DCAD uses scheduling information stored in MS Access database which is created by exporting the MS Project file to MS Access file. Therefore, the system does not support real time updating of the construction schedule.
Conclusion
4DCAD is an emerging powerful technology to manage construction projects. Several researchers have identified its advantages in terms of betterment of 1) project representation which reduces design interpretation among project members, and 2) understanding of construction sequences.
This 4DCAD technology can also be utilized to manage construction site safety. In this research, the 4DCAD is further developed into 4DCAD-Safety which supports information to safety engineers for analysing and utilizing what safety measures are needed, when, where and why they are needed.
The 4DCAD-Safety consists of four main components: AutoCADTM, Microsoft ProjectTM, Database, and 4DCAD-Safety Interface. The AutoCAD is used for modelling and displaying the 3D objects that represent the physical condition of a project. Microsoft Project is used for scheduling construction activities. Thus, by integrating the scheduling into the 3D objects, the 4DCAD technology is achieved. The database is used to store project scheduling exported from Microsoft Project, safety library and safety planning. Finally, the interface is developed to integrate the three components. The integration allows a safety plan to be simulated according to the 4DCAD simulation. Additional technology, Virtual Reality, can be added to create a virtual walkthrough mechanism. This technology facilitates users to be flexible in observing the virtually real site condition progress from any positions; and therefore a better understanding of what safety measures are needed, when, where and why they are needed is obtained.
This paper was published in the journal for “Construction Innovation 2005; 5: 99–114”. Full paper is available upon request.
Respondents’ opinions
In order to validate that the system can achieve the system objectives and benefits the construction industry, tests were conducted by two senior project managers and one senior project management consultant. The testers used the 4DCAD-Safety application, and then they were asked to answer a structured questionnaire. The questionnaire addressed two main issues: functionality, usefulness of the 4DCAD-Safety; and operability, easiness to use the system.
From Table 1, the result showed that the application is useful to assist users in analyzing construction sequence, informing spatial information and scheduling information. Moreover, the respondents were very satisfied with the application that provides them information to analyse safety planning information in terms of what, when, where and why safety measures are needed. They also considered that the application is relatively easy to use, except for generating a 4DCAD model. Generating the 4DCAD model is not easy because 1) it is difficult to develop a 3D model of a large-scale construction project, and 2) the process to link a construction scheduling and the 3D model is quite difficult. This is addressed for further research development.
System benefits and limitations
4DCAD-Safety provides general and specific benefits. The general benefits are related with the 4DCAD simulation features that have been investigated by previous researches. The specific benefits are uniquely related with the 4DCAD-Safety developed in our research.
The general benefits of 4D simulation are 1) the 4DCAD-Safety application visualizes 3D objects of a construction project, the disparity in participants’ experience or knowledge that lead to different interpretation is less significant and communication among participants can be improved (Koo and Fischer, 2000), and 2) the application can be applied to visualize and interpret construction sequence on a computer display rather than in their mind. This allows users to better understand construction sequence and detect potential problems in construction drawings as well as schedules prior construction starts (McKinney and Fischer, 1998; Kang et al., 2002).
There are two specific benefits related to the 4DCAD-Safety application. First, related with safety planning function, when construction activities are progressing according to the project calendar, the application can display safety measures that are required to carry out specific works. Secondly, since the displayed safety plan is related to the construction activities represented in 3D model, the application facilitates safety engineers to visualize spatial and physical information of construction activities and their products. This facilitates safety engineers to know and analyse what safety measures are needed to be installed, prepared, or provided for current activities and where, when, as well as why they are needed. For a better quality of visualization, 3D image rendered in AutoCAD can be saved as DFX file since this file format can be opened using World UpTM. One significant benefit of viewing 3D objects in World Up is that user can have a better walkthrough mechanism for exploring the objects (Hadikusumo and Rowlinson, 2001; 2003). As an additional benefit, the 4DCAD-Safety application has a feature for combining subcontractors’ schedules and a contractor’s schedule as well as their safety plans. This combination allows all safety plans from one organization to be communicated to other organizations since they might interact directly or indirectly in order to perform their jobs.
There are two limitations of the system: 1) the 4DCAD uses early start and finish for the simulation purposes. This must be further researched to include late start and finish, and 2) the 4DCAD uses scheduling information stored in MS Access database which is created by exporting the MS Project file to MS Access file. Therefore, the system does not support real time updating of the construction schedule.
Conclusion
4DCAD is an emerging powerful technology to manage construction projects. Several researchers have identified its advantages in terms of betterment of 1) project representation which reduces design interpretation among project members, and 2) understanding of construction sequences.
This 4DCAD technology can also be utilized to manage construction site safety. In this research, the 4DCAD is further developed into 4DCAD-Safety which supports information to safety engineers for analysing and utilizing what safety measures are needed, when, where and why they are needed.
The 4DCAD-Safety consists of four main components: AutoCADTM, Microsoft ProjectTM, Database, and 4DCAD-Safety Interface. The AutoCAD is used for modelling and displaying the 3D objects that represent the physical condition of a project. Microsoft Project is used for scheduling construction activities. Thus, by integrating the scheduling into the 3D objects, the 4DCAD technology is achieved. The database is used to store project scheduling exported from Microsoft Project, safety library and safety planning. Finally, the interface is developed to integrate the three components. The integration allows a safety plan to be simulated according to the 4DCAD simulation. Additional technology, Virtual Reality, can be added to create a virtual walkthrough mechanism. This technology facilitates users to be flexible in observing the virtually real site condition progress from any positions; and therefore a better understanding of what safety measures are needed, when, where and why they are needed is obtained.
This paper was published in the journal for “Construction Innovation 2005; 5: 99–114”. Full paper is available upon request.
The abstract is also copied and posted.
Abstract: Safety planning in construction project management is separated from other planning functions, such as scheduling. This separation creates difficulties for safety engineers to analyse what, when, why and where safety measures are needed for preventing accidents. Another problem occurs due to the conventional practice of representing project designs using two-dimensional (2D) drawings. In this practice, an engineer has to convert the 2D drawings into three-dimensional (3D) mental pictures which are a tedious task. Since this conversion is already difficult, combining these 2D drawings with safety plans increases the difficulty. In order to address the problems, 4DCAD-Safety is proposed. This paper discusses the design and development of 4DCAD-Safety application and testing its usefulness in terms of assisting users in analysing what, when, where and why safety measures are needed.
Key words: accident prevention; computer aided simulation; computer graphics; hazards; Safety
Address for correspondence: B.H.W. Hadikusumo, Assistant Professor, Construction Engineering and Infrastructure Management, Asian Institute of Technology, Bangkok, Thailand. E-mail: kusumo@ait.ac.th
