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Shared computer-aided structural design model for construction industry (infrastructure)
Computer-Aided Design 40 (2008) 778–788 www.elsevier.com/locate/cad
Shared computer-aided structural design model for construction industry (infrastructure) M. Hassanien Serror a,∗ , Junya Inoue b , Yoshinobu Adachi c , Yozo Fujino d a Department of Civil Engineering, Cairo University, Giza, Egypt b Department of Material Engineering, The University of Tokyo, Tokyo, Japan c Intelligent Systems Laboratory, SECOM Co. Ltd., Tokyo, Japan d Department of Civil Engineering, The University of Tokyo, Tokyo, Japan
Received 12 September 2006; accepted 13 July 2007
Abstract The current interaction between participants in a construction project requires much time and is often a cause of mistakes and misunderstandings. Improvement of this interaction may therefore contribute to an improvement of the construction process as a whole. The lack of interoperability is the main problem behind such interaction drawbacks. In this paper, an infrastructure for a technology transfer model, namely Shared Computer-Aided Structural Design (sCAsD) model, is developed. It is built upon three basic building blocks: the Standard for the Exchange of Product Model Data (STEP, ISO-10303) Parts 104 and 107, the CIMsteel Integration Standard (CIS/2.0) resources, and the Industry Foundation Classes (IFC) standard that is being developed by the International Alliance for Interoperability (IAI). The sCAsD model is an extension for the structural domain/view of the IFC model, providing professional standardization within the synergy effect of the IFC. The model infrastructure is explained and discussed in terms of model schemata. In addition, model feasibility is studied within two assessments for model schemata and model realization in the construction industry. The former assessment has verified the robustness and effectiveness of the model through using a model interface in data handling within an application of an integrated earthquake simulation. Meanwhile, the assessment of model realization has validated the roadmap of model implementation in the construction industry through IAI. The model has been accepted as a formal IAI project, namely ST-7, and is being supported by IAI Japan chapter. c 2007 Elsevier Ltd. All rights reserved.
Keywords: Construction industry; Structural design; Interoperability; Industry foundation classes; Product model standard; Model infrastructure
1. Introduction The construction industry is a complex industry that obligates different parties from different disciplines to interact with each other to produce the final product, which is the construction project. At any stage of the project lifecycle, any interaction drawback would affect drastically all subsequent stages. Moreover, quality degradation and cost and time ineffectiveness increase by being late in observing such drawbacks along the project lifecycle. Several initiatives are taken by the industry and by computeraided design (CAD) developers to integrate the digital project information into CAD systems. An effort that concerns the implementation of a methodology for sharing product information through a distributed object model is described ∗ Corresponding author. Tel.: +201 0166 6852; fax: +202 2634 3849.
E-mail address: [email protected] (M. Hassanien Serror). c 2007 Elsevier Ltd. All rights reserved. 0010-4485/$ - see front matter doi:10.1016/j.cad.2007.07.003
by van Leeuwen et al. [1–3]. The “collaborative working” and “prototyping” have both been identified within the industry as two methods of working that can help organizations become more profitable and productive [4]. In addition, the concept of “collaborative prototyping” has been identified as a process that challenges existing cultural attitudes and working processes and advocates a change in the way conventional projects are managed, in order to achieve a more competitive industry [5]. The advent of the Internet has opened and given, particularly, the developing countries and the world, in general, a transformation into collective intelligence societies linked to digital communication. In the context of architectural designs and construction industries, the birth of Internet-based computer-aided design (iCAD) solutions [6] has offered a new dimension to architectural practice. The function of CAD has expanded as a tool to communicate and collaborate as well as to better control all phases of the architectural practices.
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Fig. 1. The conventional interaction among structural design participants.
Trials have been conducted [7] to explore the technical issues related to the integrated use of CAD and virtual environments within the house building sector of the construction industry and to investigate the practical use of the new technology. Collaborative working in the construction industry is becoming a reality as many activities are performed globally with actors in different geographical locations. The International Alliance for Interoperability (IAI) [8] is one of these initiatives and activities for collaborative working in the construction industry through integrating digital project information into CAD systems. IAI mission has been taking place, since 1995, using the information technology (IT) to enable interoperability among construction industry participants. IAI defines interoperability as “an environment in which computer programs can share and exchange data automatically, regardless of the type of software or of where the data may be residing. It empowers the owner and user of information” [8]. Accordingly, IAI is developing data models that are compliant with the Standard for the Exchange of Product Model Data (STEP, ISO-10303) [9] for construction industry disciplines based on the required information to be exchanged. The overall container of these data models is called the Industry Foundation Classes (IFC) standard. IFC is an evolving international information exchange standard that allows project participants to work across different software applications with data continuity. To account for global relationships, in many countries the so-called “chapters” [8] are established, which work on several projects by extending the IFC model. Each chapter is a separate organization that is established according to local custom, with the goal of serving the needs of a geographical region and contributing to the overall IFC specification development process. Chapter members represent different sectors: the construction industry, software vendors, and academia. Many multinational software vendors get involved in the IAI mission to implement the IFC standard and to deliver technology/interoperability to realworld projects [10]. It has become a high-level business for
them to get certified in the world of information technology and interoperability. The collaborative working environment for construction, which is known as Web-based IFC Shared Project EnviRonment (WISPER), [11,12] is an example of many efforts [13–17] that are building on the IFC model. This environment supports: architectural design, visualization, estimating, planning, specifications, and supplier information, where a Web and an IFC-based environment are developed. In this paper, an extension for the structural domain/view of the IFC model is developed. The paper is organized as follows: problem statement is spelled out; model infrastructure is explained and discussed; assessments for model schemata and model realization in the construction industry are performed; and the concluding remarks are provided. 2. Problem statement In the structural design domain of the construction industry, traditional means of data sharing, such as paperbased documents or non-interoperable electronic-based files, require practitioners to re-enter/re-process the data as their respective software applications do not share the data format. Consequently, project teams lose crucial design and construction information as the project evolves, which ends up with quality degradation and time/cost ineffectiveness [18], as shown in Fig. 1. In this paper, an IFC-based infrastructure for a technology transfer model, namely Shared Computer-Aided Structural Design (sCAsD) model, is developed. The aim of this model is set to elaborate interoperability among structural design participants–such as designers, steel fabricators, concrete fabricators or construction managers–along the project lifecycle. This affords a new methodology of interaction, namely electronic interaction (E-Interaction). Such interaction enables a faster design iteration cycle that permits: exploring more design alternatives, obtaining more accurate design specifications, simulating more operational behaviors, and
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Fig. 2. An overview for the structural analysis process.
configuring more freedom to designers. The details behind the scenario of E-Interaction and its application to real-world projects are beyond the scope of this paper and will be presented in a separate paper. The objective of this paper is set to explain and discuss the infrastructure of the sCAsD model along with assessments for model schemata and model realization in the construction industry. The IFC-based interoperability within the structural domain is initiated through the work conducted in the ST series of IAI projects [19–21], with ST-1 to ST-6 having addressed: a steel frame construction model; a reinforced concrete construction model; a pre-cast concrete construction model; a structural analysis model; a structural timber construction model; and a further extension for the steel construction model, respectively. It is obvious that the ST series of IAI projects had paid much attention to the development of construction/fabrication-related data models, such as the defined geometric representations of steel members and connections in the ST-6 project and how to exchange these representations with different industry participants. The development of analysis-related models is initiated in the ST-4 project [20,21] that has defined the mechanical model of a structure along with static loads. According to Fig. 2, the discrete model (Finite Element Model, FEM) is essential to complete the structural analysis process, where it provides the discrete solution. Consequently, there is a need to extend the work of the ST-4 project to define: FEM model, dynamic loads, and analysis results. The authors proposed the sCAsD model to IAI International Technical Management (ITM) as an extension of the ST-4 project. In June 2005, it has been accepted as a formal IAI project with the coding name “ST-7” [22]. 3. Model infrastructure The sCAsD model is developed based on three basic building blocks, namely: STEP (ISO-10303) parts 104 and 107 [23], CIMsteel Integration Standard (CIS/2.0) resources [24], and IFC standard [8]. The authors have
conducted peer review/discussion for parts 104 and 107 of STEP and CIS/2.0 resources to explore their entities and structure [25]. In addition, the Resource and Domain layers of the IFC model architecture have been extended in order to incorporate the infrastructure of the extension model. Consequently, model originality results from the combination between the professional standardization of structural analysis entities and the synergy effect of the IFC model. It is worth noting that the typical exchange formats of STEP standard [9] can be used to exchange the sCAsD model among structural design participants, which are the same exchange formats of the IFC standard. Hereafter, the infrastructure of the sCAsD model is explained and discussed in terms of four model schemata: dynamic analysis schema, FEM schema, structural analysis results schema, and relationships schema. They are described, briefly, in four development processes that affect the Resource and Domain layers of the IFC model architecture as follows: 1. Process 1 has two sub-processes. The first defines structural dynamic actions (only earthquake action is in the scope), and the second defines dynamic boundary conditions. This process affects the IfcStructuralLoadResource schema of the Resource layer. 2. Process 2 has three sub-processes. The first defines FEM model entities, the second integrates FEM model entities with each other, and the third connects structural actions to FEM model entities. This process affects the Domain layer by adding the IfcFiniteElementAnalysisDomain schema. 3. Process 3 has two sub-processes. The first affects the IfcMeasureResource schema of the Resource layer and the IfcStructuralAnalysisDomain schema of the Domain layer by defining the measure resources and the basic entities of structural analysis results, respectively. The second affects the IfcFiniteElementAnalysisDomain schema of the Domain layer by assigning structural analysis results to FEM model. 4. Process 4 has two sub-processes. The first defines relationships for mechanical integration between FEM
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Fig. 3. Process 1 IDEF0 diagram for the development of the Shared Computer-Aided Structural Design Model.
model and architectural model; meanwhile, the second defines relationships for physical integration. This process affects the IfcFiniteElementAnalysisDomain schema of the Domain layer. A detailed explanation for model schemata can be found in the Ref. [25] where the EXPRESS, EXPRESS-G, and WHERE RULES of the model have been provided. It is worth noting that integrity with the existing IFC entities is maintained, which is an important condition for IFC extension validation by the IAI Modeling Support Group (MSG). 3.1. Dynamic analysis schema Fig. 3 shows the IDEF0 diagram [26] of process 1. It clarifies process implementation through identifying the required input and the applied control for sub-processes. Among IFC entities, two inputs are identified: the static structural action resources, created by the ST-4 project, and the property resources. The definition of dynamic actions is controlled by: the form of equivalent static load, the employed design code for response spectrum analysis, and the earthquake time history. Three categories of earthquake dynamic actions are defined. The first is an equivalent static action IfcStructuralLoadEquivalentStatic to specify a static action that is equivalent, in mechanical response, to the dynamic action. The second is a response spectrum action IfcStructuralLoadResponseSpectrum to specify a dynamic action that is calculated from a response spectrum of a design code, or a jagged response spectrum of a specific earthquake ground motion. The third is a time-history action IfcStructuralLoadTimeHistory to specify a dynamic action that is calculated from an earthquake displacement, velocity, or acceleration time history. The defined dynamic action eventually
references a static action for an equivalent static action or a list of static actions for modal and time-history dynamic actions, inheriting static action attributes. The linear boundary conditions, created by the ST-4 project, are extended to the non-linear form. In addition, dynamic displacement, velocity, and acceleration boundary conditions are defined through the entity IfcBoundaryNodeConditionDynamic. 3.2. Finite element model schema Fig. 4 shows the IDEF0 diagram of process 2. It clarifies process implementation through identifying the required input and the applied control for sub-processes. Among IFC entities, two inputs are identified: the topological representation for FEM entities representation, and the structural action resources to be assigned to FEM entities. The F1 sub-process is controlled by: the degrees of freedom, the boundary conditions, the space dimensions, and the mechanical behavior. The FEM model entities (elements, nodes, and integration points) are defined through the abstract entity IfcFiniteElementModelItem. The integrated FEM model, however, is contained in an IfcFiniteElementModel entity that is referenced by an IfcFiniteElementAnalysisModel entity, which combines the integrated FEM models with the applied loads and analysis results. The IfcFemNode has: a Position list attribute to specify node positioning coordinates, a DegreesOfFreedom list attribute to specify node degrees of freedom, and an optional AppliedCondition attribute that references an IfcBoundaryCondition entity. The IfcFemIntegrationPoint has an optional RelativePosition list attribute to specify a specific relative position of the integration point with respect to its relevant FEM element. The
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Fig. 4. Process 2 IDEF0 diagram for the development of the Shared Computer-Aided Structural Design Model.
IfcFemElement is an abstract entity for FEM elements that have been categorized, according to space dimensions, into: curve, surface, and volume elements in addition to a special element category for spring, damper, and mass elements. The methodology that is adopted here to integrate the FEM entities within the FEM model is to reference the FEM nodes and integration points from the IfcFemElement abstract entity through the list attributes Connectivity and IntegrationPoints, respectively, and the FEM element, in turn, is referenced within an IfcFiniteElementModel entity through the Elements set attribute. For the connectivity of structural actions to FEM model entities, the IfcFemStructuralAction, which is an abstract entity for FEM node and element structural actions, is defined. In addition, the IfcFemElementStructuralAction is an abstract entity for FEM curve, surface, and volume element structural action. Each entity, in turn, references an IfcStructuralAction entity through an Action attribute to pick the required static or dynamic structural action and to assign it to the relevant FEM entity. A set of IfcFemStructuralAction entities is referenced by an IfcFemStructuralActionGroup entity that is referenced by the IfcFiniteElementAnalysisModel entity through the LoadedBy set attribute. 3.3. Structural analysis results schema Fig. 5 shows the IDEF0 diagram of process 3. It clarifies process implementation through identifying the required input and the applied control for sub-processes. Among IFC entities, two inputs are identified: the IFC measure resources for structural analysis results, and the IFC structural action resources from which analysis results are calculated (including the defined dynamic actions). The A1 sub-process is controlled
by the form of the structural analysis result (straining or straining action). The A2 sub-process is controlled by the type of FEM entity (element, node, or integration point). Two categories of structural analysis results are identified under the abstract entity IfcStructuralResult. The first is IfcStructuralResultStrainingAction that is an abstract entity for straining action results: forces and stresses. The second is IfcStructuralResultStraining that is an abstract entity for straining results: strain, displacement, velocity, and acceleration. To assign structural analysis results to FEM model entities, the IfcFemStructuralResult is defined as an abstract entity for IfcFemNodeStructuralResult and IfcFemElementStructuralResult for FEM node and element structural results, respectively. The IfcFemElementStructuralResult is an abstract entity for FEM curve, surface, and volume element structural results. Each of these entities references one/list-of IfcFemStructuralResultPacket entity through Result/AssignedSubsequentResults attribute to pick the required static or dynamic structural result, from a packet form, and to assign it to the relevant FEM entity. The IfcFemStructuralResultPacket is considered to be the provider for static as well as dynamic analysis results through its attributes. The attributes are able to provide modal and timehistory results for dynamic analysis through associated Mode and TimeStep list attributes. In the case of curve, surface, and volume FEM element, structural result may be varied within the element. Consequently, parameterization values have been used to describe the distribution of the structural result. For example, the IfcFemVolumeElementStructuralResult entity has a list attribute VolumeParameterizationUValues that contains the “U ” parameter values that are needed to define positions on the used IfcFemVolumeElement. The additional needed “V ” and “W ” parameter values are contained in the list attributes
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Fig. 5. Process 3 IDEF0 diagram for the development of the Shared Computer-Aided Structural Design Model.
VolumeParameterizationVValues and VolumeParameterizationWValues, respectively. A vector of “U ”, “V ”, and “W ” values is identified by the same index of the lists containing the “U ”, “V ”, and “W ” values. Hence, by the separate list AssignedSubsequentResults, static or dynamic analysis result values are assigned to these positions. In addition, structural results may be assigned to FEM element integration points through the list attribute IntegrationPointResults that references list of IfcFemIntegrationPointStructuralResult entity. Moreover, grouping of FEM results can be handled through the IfcFemStructuralResultGroup. The IfcFiniteElementAnalysisModel entity, which is the foranalysis FEM model, references all the defined IfcFiniteElementModel entities through a set attribute FiniteElementModels. The groups of FEM actions and results are assigned to the for-analysis model through the set attributes LoadedBy and HasResults, respectively.
Fig. 7 shows the IDEF0 diagram of process 4. It clarifies process implementation through identifying the required input and the applied control for sub-processes. Among IFC entities, three inputs are identified: the IFC architectural model, the IFC mechanical model (created by the ST-4 project), and the IFC relationship resources. The R1 sub-process is controlled by the inheritance of both the mechanical and architectural entities. The R2 sub-process, however, is controlled by the inheritance of only the architectural entities. Fig. 8 shows, in EXPRESS-G, the IfcRelAssignsToFiniteElementModels entity that assigns one or more IfcFiniteElementModel entities to a relevant mechanical/architectural model. This is handled by the IfcFiniteElementModelAssignmentSelect type that references either a mechanical model (ex. IfcStructuralMember) or a physical model (ex. IfcBuildingElement, IfcBridgeSegment or IfcBridgePrismaticElement). 4. Model assessment
3.4. Relationships schema Fig. 6 shows an overview for the integration statement between the architectural model that is defined in the IFC model (the architectural view of IFC), and the FEM model that is defined in this work, ST-7 project. Two integration methodologies have been provided, namely: mechanical FEM and physical FEM. In the mechanical FEM, a mechanical model is first extracted from the architectural model through an idealization process and then discretized to FEM model through a discretization process. In the physical FEM, however, the FEM model is extracted directly from the architectural model by merging the idealization and discretization processes into one process, i.e. a mechanical model is extracted implicitly.
This section studies the feasibility of the proposed sCAsD model through performing two assessments. The first is for the schemata and the second is for a model realization roadmap in the construction industry. Model schemata assessment is intended to ensure the robustness and effectiveness of the developed model. Model realization assessment, however, is intended to validate the roadmap of model realization/implementation in the construction industry. 4.1. Model schemata assessment The authors have developed a DOSE (Distributed Objectbased Software Environment) [28–31] for urban system integrated simulation under the risk of urban-scale hazards such
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Fig. 6. An overview for the integration process between the architectural model and the FEM model.
Fig. 7. Process 4 IDEF0 diagram for the development of the Shared Computer-Aided Structural Design Model.
as earthquakes. The informal, dynamic, and evolving characteristics of the urban system interdisciplinary simulation participants create many challenges for the disconnected top-down system simulation. DOSE is envisioned as a distributed simulation service software environment running in parallel with the activities of urban system simulation participants which are: GIS-Model, CAD-Model, Geotechnical-Model, Hazard-Model and Vulnerability Analysis Model. An object-based infrastructure is developed [28] where DOSE architecture, scalability, and interoperability are the basic environment building blocks. An earthquake hazard application scenario is applied to realworld urban systems, city of Kobe (Kobe district) and Bunkyo
city (Tokyo district) in Japan [29]. Fig. 9 shows an overview for DOSE infrastructure and simulation participants. Through a component object model (COM) interface, namely KeyInterfaceIO, DOSE is used as a schema assessment tool for the sCAsD model. The KeyInterfaceIO interface is built on two main components. The first is STRCOMplus (STRucture Component Object Model plus an application), which is an application programming interface (API) for the structural domain/view of IFC object model including the sCAsD extension model [25]. The second is IFCsvr (IFC Server), which is one of the available tools for Input/Output (I/O) IFC-compliant data [27]. As shown in
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Fig. 8. EXPRESS-G representation for the integration relationship between the FEM model (IfcFiniteElementModel) on one side and the mechanical model (IfcStructuralMember) and the architectural model (IfcBuildingElement, IfcBridgeSegment, and IfcBridgePrismaticElement) on the other side through the IfcRelAssignsToFiniteElementModels entity.
Fig. 9. DOSE environment infrastructure and simulation participants.
Fig. 9, The STRCOMplus API is employed in the CAD-Model of DOSE to construct CAD representation for urban system structures and the IFCsvr is employed in DOSE interface to input/output IFC-compliant data. An application of an integrated earthquake simulation (IES) is conducted where a virtual city of eighty buildings is constructed for shaking under an earthquake disaster. The objective of this application is set to test the robustness and effectiveness of the sCAsD model schemata. Consequently, no emphasize is placed on DOSE capability/performance, ground motion characteristics, or buildings response.
Fig. 10(a) shows CAD representation for the virtual city where a three-storey building is used as a typical building in the virtual city. Fig. 10(b) and (c) show the mechanical and the FEM model of the typical building, respectively. The mechanical model is extracted from its IFC representation in STEP Part-21 format; meanwhile, a finite element analysis tool [32] is used for generating the FEM model from the mechanical model, and for conducting the dynamic analysis. Figs. 11 and 12 show a pseudo-code for the application of DOSE in the IES. The object-based structure of the sCAsD model is obvious in the process of setting the virtual city
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Fig. 10. The CAD model for (a) The eighty-building virtual city; (b) The typical-building mechanical model; and (c) The typical-building FEM model.
Fig. 11. Pseudo-code for the application of DOSE in the integrated earthquake simulation using STRCOMplus API and IFCsvr tool.
with data, as shown in Fig. 11. After creating each building element in a relevant category (beam, column, bracing, slab, etc.), elements are assigned to their relevant building storey.
Each group of building stories, in turn, is assigned to its relevant building and each building is assigned to its relevant site. Eventually, all sites are assigned to an IFC project entity
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Fig. 12. Pseudo-code for I/O interface of DOSE application in the integrated earthquake simulation using IFCsvr tool, it exports a STEP file.
Fig. 13. An illustrative I/O example command of DOSE application in the integrated earthquake simulation, among huge number of FEM nodes a specific data of a particular node can be retrieved.
(IfcProject). These tasks are performed using STRCOMplus API. Fig. 12 shows an I/O interface that is created by the IFCsvr tool for DOSE application in the IES. Fig. 13 shows an illustrative I/O example command of the application of DOSE in the IES. Among the huge number of FEM nodes, the command retrieves the x-component of position coordinates of a particular node. This node is a connectivity node of an element that is a shell quadrilateral element of a slab FEM mesh. This slab is of the first storey of one of the buildings that is located in a particular site of IES domain. It is obvious that the object-based structure of the sCAsD model schemata has enabled robust and efficient management and handling for simulation data. From enormous data sets a small piece of information can be extracted and retrieved efficiently. 4.2. Model realization assessment The authors submitted the sCAsD model proposal to IAI International Technical Management (ITM) and it has been accepted as a formal IAI project, on June 2005, with the coding name “ST-7” [22]. The project is being supported by IAI Japan chapter civil/structural engineering group, where the authors have been afforded the membership in the group and the leadership of the project. The realization roadmap of ST-7 project and, in turn, the sCAsD model consists of nine steps (defined by IAI for integration into an IFC release) [8]: (1) preparation of project proposal; (2) proposal submission to IAI ITM; (3) definition of information requirements; (4) preparation of process model
and information requirements; (5) review process model, information requirements, and draft extension model; (6) preparation of extension model documents; (7) submission of extension model documents to MSG; (8) integration of extension model into IFC; and (9) release the extension model as standard. The current status of the ST-7 project is at step five: “review process model, information requirements, and draft extension model”. Two workshops have been held for the review process. The first workshop has been held on November, 2005, among construction industry people and software vendors at IAI Japan chapter, hosted by Kajima Corporation. Meanwhile, the second workshop has been held on December, 2005, among academics at the University of Tokyo, hosted by the department of Civil Engineering. In addition, DOSE development is considered to be an application-based review for the ST-7 object model. Subprojects have been started with IAI China chapter [14] and with Cybernet [33] to implement ST-7 object model in a group of commercial structural analysis software packages, such as ETABS, ANSYS, and SAP2000. These subprojects are also considered to be application-based reviews for the ST-7 object model. Materials of workshops, discussions, and subprojects status can be found in the Ref. [25]. 5. Concluding remarks It is difficult to quantify the benefits of collaborative working practices because of the complexity of combining multiple implementation techniques. In the construction industry, there is a need to develop an easy to follow business case and prognostic tool, which can be used to demonstrate the benefits and ultimately increase the uptake of collaborative working. This is the essence of the problem that is being considered by the International Alliance for Interoperability (IAI) through Industry Foundation Classes (IFC) development projects. In this paper, an infrastructure for a technology transfer model, namely Shared Computer-Aided Structural Design (sCAsD) model, is developed. It is built on three basic building blocks: the Standard for the Exchange of Product Model Data (STEP, ISO-10303) Parts 104 and 107, CIMsteel Integration Standard (CIS/2.0) resources, and the IFC standard that is being
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developed by IAI. The sCAsD model is an extension model for the structural domain/view of IFC object model, providing professional standardization within the synergy effect of IFC. Model infrastructure is explained and discussed in terms of model schemata. In addition, two assessments are provided for model schemata and model realization in the construction industry. Model schemata robustness and effectiveness are verified through robust and efficient data management/handling in an application based on an integrated earthquake simulation, where the model interface is employed to manage/handle simulation data. It is found that from enormous data sets a small piece of information can be extracted and retrieved efficiently. On the other hand, the roadmap for model realization in the construction industry is validated through IAI. The model has been accepted as a formal IAI project, namely ST-7, and is being supported by IAI Japan chapter. It is worth noting that real-world application for the sCAsD model is planned through collaboration with industry participants who are IAI members. This application is necessary to have more concrete conclusion and to understand the flaws and weakness of the proposed model within realworld projects. Acknowledgments We are grateful for the support provided by the Japan Society for the Promotion of Science (JSPS), Japan MEXT, and the International Alliance for Interoperability (IAI, Japan chapter, Civil/Structural Engineering group). We would like to thank the review board of the journal. References [1] van Leeuwen JP, van der Zee A. Distributed object models for collaboration in the construction industry. Automation in Construction 2005;14:491–9. [2] van Leeuwen JP. Computer support for collaborative work in the construction industry. In: Proc. of the international conference on concurrent engineering. 2003. [3] van Leeuwen JP, Fridqvist S. Object version control for collaborative design—characteristics of the concept-modelling framework, E-activities and intelligent support in design and the built environment. In: 9th EuropIA international conference. 2003. [4] Foresight, Constructing the future, Foresight Construction association programme, DTI, UK, URL: www.foresight.gov.uk; 2001. [5] Yeomans SG, Bouchlaghem NM, El-Hamalawi A. An evaluation of current collaborative prototyping practices within the AEC industry. Automation in Construction 2006;15:139–49. [6] Husin R, Rafi A. The impact of Internet-enabled computer-aided design in the construction industry. Automation in Construction 2003;12:509–13. [7] Whyte J, Bouchlaghem N, Thorpe A, McCaffer R. From CAD to virtual reality: Modelling approaches, data exchange and interactive 3D building design tools. Automation in Construction 2000;10:43–55. [8] IAI. Release 2x2 of IFC, URL: http://cig.bre.co.uk/iai international/; 2005. [9] ISO STEP language and parts of ISO 10303, URL: http://www.tc184-sc4. org/SC4 Open/SC4 Work Products Documents/STEP (10303)/; 2005. [10] IAI. Implementation Software Packages Compliant to IFC, URL: http://www.bauwesen.fh-muenchen.de/iai/ImplementationOverview.htm; 2005.
[11] Faraj I, Alshawi M, Aouad G, Child T, Underwood J. An industry foundation classes Web-based collaborative construction computer environment: WISPER. Automation in Construction 2000;10:79–99. [12] Alshawi M, Aouad G, Faraj I, Child T, Underwood J. The implementation of the industry foundation classes in integrated environments. In: CIB W78 conference. 1998. p. 55–66. [13] Tanyer AM, Aouad G. Moving beyond the fourth dimension with an IFC-based single project database. Automation in Construction 2005;14: 15–32. [14] Xue Yuan D, Tse-Yung PC. Creating structural model from IFC-based architectural model. In: Proc. of the joint international conference on computing and decision making in civil and building engineering. 2006. p. 3687–95. [15] Yasaka A, Kataoka H, Kasima K, Takeda M, Usami M, Yabuki N, et al. The development of the reinforced concrete structural model on IFC specifications. In: Proc. of the joint international conference on computing and decision making in civil and building engineering. 2006. p. 3116–25. [16] Yungui L, Baichun L. Information-Share based upon IFC standard in engineering construction. In: Proc. of the joint international conference on computing and decision making in civil and building engineering. 2006. p. 114–24. [17] Robert RL. Mapping between the CIMsteel integration standards and industry foundation classes product model for structural steel. In: Proc. of the joint international conference on computing and decision making in civil and building engineering. 2006. p. 3087–96. [18] Latham M. Constructing the team. Final report of the Government/Industry review of procurement and contractual arrangements in the UK construction industry HMSO, London; 1994. p. 7. [19] IAI. IFC extension projects, URL: http://ce.vtt.fi/iaiIFCprojects/ ListProjects.jsp; 2005. [20] Romberg R, Niggl A, van Treeck C, Rank E. Structural analysis based on the product model standard IFC. ICCCBE-X. Weimar (Germany); 2004. [21] Weise M, Katranuschkov P, Scherer RJ. A proposed extension of the IFC project model for structural analysis. In: Proc. of ECPPM. 2000. p. 229–38. [22] IAI. ST-7 extension project, URL: http://groups.yahoo.com/group/ST-7/; 2005. [23] STEP resource schemas, Application integrated resources, finite element analysis, URL: http://www.steptools.com/support/stdev docs/ express/step irs/index.html; 2005. [24] CIMsteel integration standards release 2: 2nd edition, URL: http://www. cis2.org/ and http://www.cis2.org/LPM6.exp; 2005. [25] IAI. ST-7 extension project files, URL: http://groups.yahoo.com/group/ ST-7/files/; 2005. [26] IDEF (Integrated DEFinition methods), URL: http://www.idef.com/; 2005. [27] IAI-International, IFC developers software tools, URL: http://www. iai-international.org/software/Tools%20for%20IFC%20developers.html# other tools; 2005. [28] Hassanien Serror M, Inoue J, Hori M, Fujino Y. Distributed object-based software environment for urban system integrated simulation under urbanscale hazard: I-Infrastructure. Earthquake Engineering and Structural Dynamics 2007;36(11):1545–60, doi:10.1002/eqe.706. [29] Hassanien Serror M, Inoue J, Hori M, Fujino Y. Distributed object-based software environment for urban system integrated simulation under urbanscale hazard: II-Application. Earthquake Engineering and Structural Dynamics 2007;36(11):1561–79, doi:10.1002/eqe.705. [30] Hassanien Serror M, Inoue J. Interoperability in an IFC-Compliant integrated earthquake simulation. In: Proc. of the 10th inter. conference on civil, structural, and environmental engineering computing. Rome (Italy): Civil-Comp Press; 2005. [31] Hassanien Serror M, Inoue J, Ichimura T, Hori M. Kernel-based message passing interfaced integrated earthquake simulation. In: Proc. of the 10th inter. conference on civil, structural, and environmental engineering computing. Rome (Italy): Civil-Comp Press; 2005. [32] Computer & Engineering SAP2000 product version 7.4; 2005. [33] Cybernet FEM simulation, http://www.cybernet.co.jp/english/products/ meca cae.html; 2007.
Shared computer-aided structural design model for construction industry (infrastructure) M. Hassanien Serror a,∗ , Junya Inoue b , Yoshinobu Adachi c , Yozo Fujino d a Department of Civil Engineering, Cairo University, Giza, Egypt b Department of Material Engineering, The University of Tokyo, Tokyo, Japan c Intelligent Systems Laboratory, SECOM Co. Ltd., Tokyo, Japan d Department of Civil Engineering, The University of Tokyo, Tokyo, Japan
Received 12 September 2006; accepted 13 July 2007
Abstract The current interaction between participants in a construction project requires much time and is often a cause of mistakes and misunderstandings. Improvement of this interaction may therefore contribute to an improvement of the construction process as a whole. The lack of interoperability is the main problem behind such interaction drawbacks. In this paper, an infrastructure for a technology transfer model, namely Shared Computer-Aided Structural Design (sCAsD) model, is developed. It is built upon three basic building blocks: the Standard for the Exchange of Product Model Data (STEP, ISO-10303) Parts 104 and 107, the CIMsteel Integration Standard (CIS/2.0) resources, and the Industry Foundation Classes (IFC) standard that is being developed by the International Alliance for Interoperability (IAI). The sCAsD model is an extension for the structural domain/view of the IFC model, providing professional standardization within the synergy effect of the IFC. The model infrastructure is explained and discussed in terms of model schemata. In addition, model feasibility is studied within two assessments for model schemata and model realization in the construction industry. The former assessment has verified the robustness and effectiveness of the model through using a model interface in data handling within an application of an integrated earthquake simulation. Meanwhile, the assessment of model realization has validated the roadmap of model implementation in the construction industry through IAI. The model has been accepted as a formal IAI project, namely ST-7, and is being supported by IAI Japan chapter. c 2007 Elsevier Ltd. All rights reserved.
Keywords: Construction industry; Structural design; Interoperability; Industry foundation classes; Product model standard; Model infrastructure
1. Introduction The construction industry is a complex industry that obligates different parties from different disciplines to interact with each other to produce the final product, which is the construction project. At any stage of the project lifecycle, any interaction drawback would affect drastically all subsequent stages. Moreover, quality degradation and cost and time ineffectiveness increase by being late in observing such drawbacks along the project lifecycle. Several initiatives are taken by the industry and by computeraided design (CAD) developers to integrate the digital project information into CAD systems. An effort that concerns the implementation of a methodology for sharing product information through a distributed object model is described ∗ Corresponding author. Tel.: +201 0166 6852; fax: +202 2634 3849.
E-mail address: [email protected] (M. Hassanien Serror). c 2007 Elsevier Ltd. All rights reserved. 0010-4485/$ - see front matter doi:10.1016/j.cad.2007.07.003
by van Leeuwen et al. [1–3]. The “collaborative working” and “prototyping” have both been identified within the industry as two methods of working that can help organizations become more profitable and productive [4]. In addition, the concept of “collaborative prototyping” has been identified as a process that challenges existing cultural attitudes and working processes and advocates a change in the way conventional projects are managed, in order to achieve a more competitive industry [5]. The advent of the Internet has opened and given, particularly, the developing countries and the world, in general, a transformation into collective intelligence societies linked to digital communication. In the context of architectural designs and construction industries, the birth of Internet-based computer-aided design (iCAD) solutions [6] has offered a new dimension to architectural practice. The function of CAD has expanded as a tool to communicate and collaborate as well as to better control all phases of the architectural practices.
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Fig. 1. The conventional interaction among structural design participants.
Trials have been conducted [7] to explore the technical issues related to the integrated use of CAD and virtual environments within the house building sector of the construction industry and to investigate the practical use of the new technology. Collaborative working in the construction industry is becoming a reality as many activities are performed globally with actors in different geographical locations. The International Alliance for Interoperability (IAI) [8] is one of these initiatives and activities for collaborative working in the construction industry through integrating digital project information into CAD systems. IAI mission has been taking place, since 1995, using the information technology (IT) to enable interoperability among construction industry participants. IAI defines interoperability as “an environment in which computer programs can share and exchange data automatically, regardless of the type of software or of where the data may be residing. It empowers the owner and user of information” [8]. Accordingly, IAI is developing data models that are compliant with the Standard for the Exchange of Product Model Data (STEP, ISO-10303) [9] for construction industry disciplines based on the required information to be exchanged. The overall container of these data models is called the Industry Foundation Classes (IFC) standard. IFC is an evolving international information exchange standard that allows project participants to work across different software applications with data continuity. To account for global relationships, in many countries the so-called “chapters” [8] are established, which work on several projects by extending the IFC model. Each chapter is a separate organization that is established according to local custom, with the goal of serving the needs of a geographical region and contributing to the overall IFC specification development process. Chapter members represent different sectors: the construction industry, software vendors, and academia. Many multinational software vendors get involved in the IAI mission to implement the IFC standard and to deliver technology/interoperability to realworld projects [10]. It has become a high-level business for
them to get certified in the world of information technology and interoperability. The collaborative working environment for construction, which is known as Web-based IFC Shared Project EnviRonment (WISPER), [11,12] is an example of many efforts [13–17] that are building on the IFC model. This environment supports: architectural design, visualization, estimating, planning, specifications, and supplier information, where a Web and an IFC-based environment are developed. In this paper, an extension for the structural domain/view of the IFC model is developed. The paper is organized as follows: problem statement is spelled out; model infrastructure is explained and discussed; assessments for model schemata and model realization in the construction industry are performed; and the concluding remarks are provided. 2. Problem statement In the structural design domain of the construction industry, traditional means of data sharing, such as paperbased documents or non-interoperable electronic-based files, require practitioners to re-enter/re-process the data as their respective software applications do not share the data format. Consequently, project teams lose crucial design and construction information as the project evolves, which ends up with quality degradation and time/cost ineffectiveness [18], as shown in Fig. 1. In this paper, an IFC-based infrastructure for a technology transfer model, namely Shared Computer-Aided Structural Design (sCAsD) model, is developed. The aim of this model is set to elaborate interoperability among structural design participants–such as designers, steel fabricators, concrete fabricators or construction managers–along the project lifecycle. This affords a new methodology of interaction, namely electronic interaction (E-Interaction). Such interaction enables a faster design iteration cycle that permits: exploring more design alternatives, obtaining more accurate design specifications, simulating more operational behaviors, and
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Fig. 2. An overview for the structural analysis process.
configuring more freedom to designers. The details behind the scenario of E-Interaction and its application to real-world projects are beyond the scope of this paper and will be presented in a separate paper. The objective of this paper is set to explain and discuss the infrastructure of the sCAsD model along with assessments for model schemata and model realization in the construction industry. The IFC-based interoperability within the structural domain is initiated through the work conducted in the ST series of IAI projects [19–21], with ST-1 to ST-6 having addressed: a steel frame construction model; a reinforced concrete construction model; a pre-cast concrete construction model; a structural analysis model; a structural timber construction model; and a further extension for the steel construction model, respectively. It is obvious that the ST series of IAI projects had paid much attention to the development of construction/fabrication-related data models, such as the defined geometric representations of steel members and connections in the ST-6 project and how to exchange these representations with different industry participants. The development of analysis-related models is initiated in the ST-4 project [20,21] that has defined the mechanical model of a structure along with static loads. According to Fig. 2, the discrete model (Finite Element Model, FEM) is essential to complete the structural analysis process, where it provides the discrete solution. Consequently, there is a need to extend the work of the ST-4 project to define: FEM model, dynamic loads, and analysis results. The authors proposed the sCAsD model to IAI International Technical Management (ITM) as an extension of the ST-4 project. In June 2005, it has been accepted as a formal IAI project with the coding name “ST-7” [22]. 3. Model infrastructure The sCAsD model is developed based on three basic building blocks, namely: STEP (ISO-10303) parts 104 and 107 [23], CIMsteel Integration Standard (CIS/2.0) resources [24], and IFC standard [8]. The authors have
conducted peer review/discussion for parts 104 and 107 of STEP and CIS/2.0 resources to explore their entities and structure [25]. In addition, the Resource and Domain layers of the IFC model architecture have been extended in order to incorporate the infrastructure of the extension model. Consequently, model originality results from the combination between the professional standardization of structural analysis entities and the synergy effect of the IFC model. It is worth noting that the typical exchange formats of STEP standard [9] can be used to exchange the sCAsD model among structural design participants, which are the same exchange formats of the IFC standard. Hereafter, the infrastructure of the sCAsD model is explained and discussed in terms of four model schemata: dynamic analysis schema, FEM schema, structural analysis results schema, and relationships schema. They are described, briefly, in four development processes that affect the Resource and Domain layers of the IFC model architecture as follows: 1. Process 1 has two sub-processes. The first defines structural dynamic actions (only earthquake action is in the scope), and the second defines dynamic boundary conditions. This process affects the IfcStructuralLoadResource schema of the Resource layer. 2. Process 2 has three sub-processes. The first defines FEM model entities, the second integrates FEM model entities with each other, and the third connects structural actions to FEM model entities. This process affects the Domain layer by adding the IfcFiniteElementAnalysisDomain schema. 3. Process 3 has two sub-processes. The first affects the IfcMeasureResource schema of the Resource layer and the IfcStructuralAnalysisDomain schema of the Domain layer by defining the measure resources and the basic entities of structural analysis results, respectively. The second affects the IfcFiniteElementAnalysisDomain schema of the Domain layer by assigning structural analysis results to FEM model. 4. Process 4 has two sub-processes. The first defines relationships for mechanical integration between FEM
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Fig. 3. Process 1 IDEF0 diagram for the development of the Shared Computer-Aided Structural Design Model.
model and architectural model; meanwhile, the second defines relationships for physical integration. This process affects the IfcFiniteElementAnalysisDomain schema of the Domain layer. A detailed explanation for model schemata can be found in the Ref. [25] where the EXPRESS, EXPRESS-G, and WHERE RULES of the model have been provided. It is worth noting that integrity with the existing IFC entities is maintained, which is an important condition for IFC extension validation by the IAI Modeling Support Group (MSG). 3.1. Dynamic analysis schema Fig. 3 shows the IDEF0 diagram [26] of process 1. It clarifies process implementation through identifying the required input and the applied control for sub-processes. Among IFC entities, two inputs are identified: the static structural action resources, created by the ST-4 project, and the property resources. The definition of dynamic actions is controlled by: the form of equivalent static load, the employed design code for response spectrum analysis, and the earthquake time history. Three categories of earthquake dynamic actions are defined. The first is an equivalent static action IfcStructuralLoadEquivalentStatic to specify a static action that is equivalent, in mechanical response, to the dynamic action. The second is a response spectrum action IfcStructuralLoadResponseSpectrum to specify a dynamic action that is calculated from a response spectrum of a design code, or a jagged response spectrum of a specific earthquake ground motion. The third is a time-history action IfcStructuralLoadTimeHistory to specify a dynamic action that is calculated from an earthquake displacement, velocity, or acceleration time history. The defined dynamic action eventually
references a static action for an equivalent static action or a list of static actions for modal and time-history dynamic actions, inheriting static action attributes. The linear boundary conditions, created by the ST-4 project, are extended to the non-linear form. In addition, dynamic displacement, velocity, and acceleration boundary conditions are defined through the entity IfcBoundaryNodeConditionDynamic. 3.2. Finite element model schema Fig. 4 shows the IDEF0 diagram of process 2. It clarifies process implementation through identifying the required input and the applied control for sub-processes. Among IFC entities, two inputs are identified: the topological representation for FEM entities representation, and the structural action resources to be assigned to FEM entities. The F1 sub-process is controlled by: the degrees of freedom, the boundary conditions, the space dimensions, and the mechanical behavior. The FEM model entities (elements, nodes, and integration points) are defined through the abstract entity IfcFiniteElementModelItem. The integrated FEM model, however, is contained in an IfcFiniteElementModel entity that is referenced by an IfcFiniteElementAnalysisModel entity, which combines the integrated FEM models with the applied loads and analysis results. The IfcFemNode has: a Position list attribute to specify node positioning coordinates, a DegreesOfFreedom list attribute to specify node degrees of freedom, and an optional AppliedCondition attribute that references an IfcBoundaryCondition entity. The IfcFemIntegrationPoint has an optional RelativePosition list attribute to specify a specific relative position of the integration point with respect to its relevant FEM element. The
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Fig. 4. Process 2 IDEF0 diagram for the development of the Shared Computer-Aided Structural Design Model.
IfcFemElement is an abstract entity for FEM elements that have been categorized, according to space dimensions, into: curve, surface, and volume elements in addition to a special element category for spring, damper, and mass elements. The methodology that is adopted here to integrate the FEM entities within the FEM model is to reference the FEM nodes and integration points from the IfcFemElement abstract entity through the list attributes Connectivity and IntegrationPoints, respectively, and the FEM element, in turn, is referenced within an IfcFiniteElementModel entity through the Elements set attribute. For the connectivity of structural actions to FEM model entities, the IfcFemStructuralAction, which is an abstract entity for FEM node and element structural actions, is defined. In addition, the IfcFemElementStructuralAction is an abstract entity for FEM curve, surface, and volume element structural action. Each entity, in turn, references an IfcStructuralAction entity through an Action attribute to pick the required static or dynamic structural action and to assign it to the relevant FEM entity. A set of IfcFemStructuralAction entities is referenced by an IfcFemStructuralActionGroup entity that is referenced by the IfcFiniteElementAnalysisModel entity through the LoadedBy set attribute. 3.3. Structural analysis results schema Fig. 5 shows the IDEF0 diagram of process 3. It clarifies process implementation through identifying the required input and the applied control for sub-processes. Among IFC entities, two inputs are identified: the IFC measure resources for structural analysis results, and the IFC structural action resources from which analysis results are calculated (including the defined dynamic actions). The A1 sub-process is controlled
by the form of the structural analysis result (straining or straining action). The A2 sub-process is controlled by the type of FEM entity (element, node, or integration point). Two categories of structural analysis results are identified under the abstract entity IfcStructuralResult. The first is IfcStructuralResultStrainingAction that is an abstract entity for straining action results: forces and stresses. The second is IfcStructuralResultStraining that is an abstract entity for straining results: strain, displacement, velocity, and acceleration. To assign structural analysis results to FEM model entities, the IfcFemStructuralResult is defined as an abstract entity for IfcFemNodeStructuralResult and IfcFemElementStructuralResult for FEM node and element structural results, respectively. The IfcFemElementStructuralResult is an abstract entity for FEM curve, surface, and volume element structural results. Each of these entities references one/list-of IfcFemStructuralResultPacket entity through Result/AssignedSubsequentResults attribute to pick the required static or dynamic structural result, from a packet form, and to assign it to the relevant FEM entity. The IfcFemStructuralResultPacket is considered to be the provider for static as well as dynamic analysis results through its attributes. The attributes are able to provide modal and timehistory results for dynamic analysis through associated Mode and TimeStep list attributes. In the case of curve, surface, and volume FEM element, structural result may be varied within the element. Consequently, parameterization values have been used to describe the distribution of the structural result. For example, the IfcFemVolumeElementStructuralResult entity has a list attribute VolumeParameterizationUValues that contains the “U ” parameter values that are needed to define positions on the used IfcFemVolumeElement. The additional needed “V ” and “W ” parameter values are contained in the list attributes
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Fig. 5. Process 3 IDEF0 diagram for the development of the Shared Computer-Aided Structural Design Model.
VolumeParameterizationVValues and VolumeParameterizationWValues, respectively. A vector of “U ”, “V ”, and “W ” values is identified by the same index of the lists containing the “U ”, “V ”, and “W ” values. Hence, by the separate list AssignedSubsequentResults, static or dynamic analysis result values are assigned to these positions. In addition, structural results may be assigned to FEM element integration points through the list attribute IntegrationPointResults that references list of IfcFemIntegrationPointStructuralResult entity. Moreover, grouping of FEM results can be handled through the IfcFemStructuralResultGroup. The IfcFiniteElementAnalysisModel entity, which is the foranalysis FEM model, references all the defined IfcFiniteElementModel entities through a set attribute FiniteElementModels. The groups of FEM actions and results are assigned to the for-analysis model through the set attributes LoadedBy and HasResults, respectively.
Fig. 7 shows the IDEF0 diagram of process 4. It clarifies process implementation through identifying the required input and the applied control for sub-processes. Among IFC entities, three inputs are identified: the IFC architectural model, the IFC mechanical model (created by the ST-4 project), and the IFC relationship resources. The R1 sub-process is controlled by the inheritance of both the mechanical and architectural entities. The R2 sub-process, however, is controlled by the inheritance of only the architectural entities. Fig. 8 shows, in EXPRESS-G, the IfcRelAssignsToFiniteElementModels entity that assigns one or more IfcFiniteElementModel entities to a relevant mechanical/architectural model. This is handled by the IfcFiniteElementModelAssignmentSelect type that references either a mechanical model (ex. IfcStructuralMember) or a physical model (ex. IfcBuildingElement, IfcBridgeSegment or IfcBridgePrismaticElement). 4. Model assessment
3.4. Relationships schema Fig. 6 shows an overview for the integration statement between the architectural model that is defined in the IFC model (the architectural view of IFC), and the FEM model that is defined in this work, ST-7 project. Two integration methodologies have been provided, namely: mechanical FEM and physical FEM. In the mechanical FEM, a mechanical model is first extracted from the architectural model through an idealization process and then discretized to FEM model through a discretization process. In the physical FEM, however, the FEM model is extracted directly from the architectural model by merging the idealization and discretization processes into one process, i.e. a mechanical model is extracted implicitly.
This section studies the feasibility of the proposed sCAsD model through performing two assessments. The first is for the schemata and the second is for a model realization roadmap in the construction industry. Model schemata assessment is intended to ensure the robustness and effectiveness of the developed model. Model realization assessment, however, is intended to validate the roadmap of model realization/implementation in the construction industry. 4.1. Model schemata assessment The authors have developed a DOSE (Distributed Objectbased Software Environment) [28–31] for urban system integrated simulation under the risk of urban-scale hazards such
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Fig. 6. An overview for the integration process between the architectural model and the FEM model.
Fig. 7. Process 4 IDEF0 diagram for the development of the Shared Computer-Aided Structural Design Model.
as earthquakes. The informal, dynamic, and evolving characteristics of the urban system interdisciplinary simulation participants create many challenges for the disconnected top-down system simulation. DOSE is envisioned as a distributed simulation service software environment running in parallel with the activities of urban system simulation participants which are: GIS-Model, CAD-Model, Geotechnical-Model, Hazard-Model and Vulnerability Analysis Model. An object-based infrastructure is developed [28] where DOSE architecture, scalability, and interoperability are the basic environment building blocks. An earthquake hazard application scenario is applied to realworld urban systems, city of Kobe (Kobe district) and Bunkyo
city (Tokyo district) in Japan [29]. Fig. 9 shows an overview for DOSE infrastructure and simulation participants. Through a component object model (COM) interface, namely KeyInterfaceIO, DOSE is used as a schema assessment tool for the sCAsD model. The KeyInterfaceIO interface is built on two main components. The first is STRCOMplus (STRucture Component Object Model plus an application), which is an application programming interface (API) for the structural domain/view of IFC object model including the sCAsD extension model [25]. The second is IFCsvr (IFC Server), which is one of the available tools for Input/Output (I/O) IFC-compliant data [27]. As shown in
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Fig. 8. EXPRESS-G representation for the integration relationship between the FEM model (IfcFiniteElementModel) on one side and the mechanical model (IfcStructuralMember) and the architectural model (IfcBuildingElement, IfcBridgeSegment, and IfcBridgePrismaticElement) on the other side through the IfcRelAssignsToFiniteElementModels entity.
Fig. 9. DOSE environment infrastructure and simulation participants.
Fig. 9, The STRCOMplus API is employed in the CAD-Model of DOSE to construct CAD representation for urban system structures and the IFCsvr is employed in DOSE interface to input/output IFC-compliant data. An application of an integrated earthquake simulation (IES) is conducted where a virtual city of eighty buildings is constructed for shaking under an earthquake disaster. The objective of this application is set to test the robustness and effectiveness of the sCAsD model schemata. Consequently, no emphasize is placed on DOSE capability/performance, ground motion characteristics, or buildings response.
Fig. 10(a) shows CAD representation for the virtual city where a three-storey building is used as a typical building in the virtual city. Fig. 10(b) and (c) show the mechanical and the FEM model of the typical building, respectively. The mechanical model is extracted from its IFC representation in STEP Part-21 format; meanwhile, a finite element analysis tool [32] is used for generating the FEM model from the mechanical model, and for conducting the dynamic analysis. Figs. 11 and 12 show a pseudo-code for the application of DOSE in the IES. The object-based structure of the sCAsD model is obvious in the process of setting the virtual city
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Fig. 10. The CAD model for (a) The eighty-building virtual city; (b) The typical-building mechanical model; and (c) The typical-building FEM model.
Fig. 11. Pseudo-code for the application of DOSE in the integrated earthquake simulation using STRCOMplus API and IFCsvr tool.
with data, as shown in Fig. 11. After creating each building element in a relevant category (beam, column, bracing, slab, etc.), elements are assigned to their relevant building storey.
Each group of building stories, in turn, is assigned to its relevant building and each building is assigned to its relevant site. Eventually, all sites are assigned to an IFC project entity
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Fig. 12. Pseudo-code for I/O interface of DOSE application in the integrated earthquake simulation using IFCsvr tool, it exports a STEP file.
Fig. 13. An illustrative I/O example command of DOSE application in the integrated earthquake simulation, among huge number of FEM nodes a specific data of a particular node can be retrieved.
(IfcProject). These tasks are performed using STRCOMplus API. Fig. 12 shows an I/O interface that is created by the IFCsvr tool for DOSE application in the IES. Fig. 13 shows an illustrative I/O example command of the application of DOSE in the IES. Among the huge number of FEM nodes, the command retrieves the x-component of position coordinates of a particular node. This node is a connectivity node of an element that is a shell quadrilateral element of a slab FEM mesh. This slab is of the first storey of one of the buildings that is located in a particular site of IES domain. It is obvious that the object-based structure of the sCAsD model schemata has enabled robust and efficient management and handling for simulation data. From enormous data sets a small piece of information can be extracted and retrieved efficiently. 4.2. Model realization assessment The authors submitted the sCAsD model proposal to IAI International Technical Management (ITM) and it has been accepted as a formal IAI project, on June 2005, with the coding name “ST-7” [22]. The project is being supported by IAI Japan chapter civil/structural engineering group, where the authors have been afforded the membership in the group and the leadership of the project. The realization roadmap of ST-7 project and, in turn, the sCAsD model consists of nine steps (defined by IAI for integration into an IFC release) [8]: (1) preparation of project proposal; (2) proposal submission to IAI ITM; (3) definition of information requirements; (4) preparation of process model
and information requirements; (5) review process model, information requirements, and draft extension model; (6) preparation of extension model documents; (7) submission of extension model documents to MSG; (8) integration of extension model into IFC; and (9) release the extension model as standard. The current status of the ST-7 project is at step five: “review process model, information requirements, and draft extension model”. Two workshops have been held for the review process. The first workshop has been held on November, 2005, among construction industry people and software vendors at IAI Japan chapter, hosted by Kajima Corporation. Meanwhile, the second workshop has been held on December, 2005, among academics at the University of Tokyo, hosted by the department of Civil Engineering. In addition, DOSE development is considered to be an application-based review for the ST-7 object model. Subprojects have been started with IAI China chapter [14] and with Cybernet [33] to implement ST-7 object model in a group of commercial structural analysis software packages, such as ETABS, ANSYS, and SAP2000. These subprojects are also considered to be application-based reviews for the ST-7 object model. Materials of workshops, discussions, and subprojects status can be found in the Ref. [25]. 5. Concluding remarks It is difficult to quantify the benefits of collaborative working practices because of the complexity of combining multiple implementation techniques. In the construction industry, there is a need to develop an easy to follow business case and prognostic tool, which can be used to demonstrate the benefits and ultimately increase the uptake of collaborative working. This is the essence of the problem that is being considered by the International Alliance for Interoperability (IAI) through Industry Foundation Classes (IFC) development projects. In this paper, an infrastructure for a technology transfer model, namely Shared Computer-Aided Structural Design (sCAsD) model, is developed. It is built on three basic building blocks: the Standard for the Exchange of Product Model Data (STEP, ISO-10303) Parts 104 and 107, CIMsteel Integration Standard (CIS/2.0) resources, and the IFC standard that is being
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developed by IAI. The sCAsD model is an extension model for the structural domain/view of IFC object model, providing professional standardization within the synergy effect of IFC. Model infrastructure is explained and discussed in terms of model schemata. In addition, two assessments are provided for model schemata and model realization in the construction industry. Model schemata robustness and effectiveness are verified through robust and efficient data management/handling in an application based on an integrated earthquake simulation, where the model interface is employed to manage/handle simulation data. It is found that from enormous data sets a small piece of information can be extracted and retrieved efficiently. On the other hand, the roadmap for model realization in the construction industry is validated through IAI. The model has been accepted as a formal IAI project, namely ST-7, and is being supported by IAI Japan chapter. It is worth noting that real-world application for the sCAsD model is planned through collaboration with industry participants who are IAI members. This application is necessary to have more concrete conclusion and to understand the flaws and weakness of the proposed model within realworld projects. Acknowledgments We are grateful for the support provided by the Japan Society for the Promotion of Science (JSPS), Japan MEXT, and the International Alliance for Interoperability (IAI, Japan chapter, Civil/Structural Engineering group). We would like to thank the review board of the journal. References [1] van Leeuwen JP, van der Zee A. Distributed object models for collaboration in the construction industry. Automation in Construction 2005;14:491–9. [2] van Leeuwen JP. Computer support for collaborative work in the construction industry. In: Proc. of the international conference on concurrent engineering. 2003. [3] van Leeuwen JP, Fridqvist S. Object version control for collaborative design—characteristics of the concept-modelling framework, E-activities and intelligent support in design and the built environment. In: 9th EuropIA international conference. 2003. [4] Foresight, Constructing the future, Foresight Construction association programme, DTI, UK, URL: www.foresight.gov.uk; 2001. [5] Yeomans SG, Bouchlaghem NM, El-Hamalawi A. An evaluation of current collaborative prototyping practices within the AEC industry. Automation in Construction 2006;15:139–49. [6] Husin R, Rafi A. The impact of Internet-enabled computer-aided design in the construction industry. Automation in Construction 2003;12:509–13. [7] Whyte J, Bouchlaghem N, Thorpe A, McCaffer R. From CAD to virtual reality: Modelling approaches, data exchange and interactive 3D building design tools. Automation in Construction 2000;10:43–55. [8] IAI. Release 2x2 of IFC, URL: http://cig.bre.co.uk/iai international/; 2005. [9] ISO STEP language and parts of ISO 10303, URL: http://www.tc184-sc4. org/SC4 Open/SC4 Work Products Documents/STEP (10303)/; 2005. [10] IAI. Implementation Software Packages Compliant to IFC, URL: http://www.bauwesen.fh-muenchen.de/iai/ImplementationOverview.htm; 2005.
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