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The cost and effort of modeling existing bridges from point clouds currently outweighs the perceived benefits of the resulting model. There is a pressing need to automate this process. Previous research has achieved the automatic generation of surface primitives combined with rule-based classification to create labeled cuboids and cylinders from point clouds. Although these methods work well in synthetic data sets or idealized cases, they encounter huge challenges when dealing with real-world bridge point clouds, which are often unevenly distributed and suffer from occlusions. In addition, real bridge geometries are complicated. In this article, we propose a novel top-down method to tackle these challenges for detecting slab, pier, pier cap, and girder components in reinforced concrete bridges. This method uses a slicing algorithm to separate the deck assembly from pier assemblies. It then detects and segments pier caps using their surface normal, and girders using oriented bounding boxes and density histograms. Finally, our method merges oversegments into individually labeled point clusters. The results of 10 real-world bridge point cloud experiments indicate that our method achieves very high detection performance. This is the first method of its kind to achieve robust detection performance for the four component types in reinforced concrete bridges and to directly produce labeled point clusters. Our work provides a solid foundation for future work in generating rich Industry Foundation Classes models from the labeled point clusters.

As the information from diverse disciplines continues to integrate during the whole life cycle of an Architecture, Engineering, and Construction AEC project, the BIM Building Information Model/Modeling becomes increasingly large. This condition will cause users difficulty in acquiring the information they truly desire on a mobile device with limited space for interaction. The situation will be even worse for personnel without extensive knowledge of Industry Foundation Classes IFC or for nonexperts of the BIM software. To improve the value of the big data of BIM, an approach to intelligent data retrieval and representation for cloud BIM applications based on natural language processing was proposed. First, strategies for data storage and query acceleration based on the popular cloud-based database were explored to handle the large amount of BIM data. Then, the concepts "keyword" and "constraint" were proposed to capture the key objects and their specifications in a natural-language-based sentence that expresses the requirements of the user. Keywords and constraints can be mapped to IFC entities or properties through the International Framework for Dictionaries IFD. The relationship between the user's requirement and the IFC-based data model was established by path finding in a graph generated from the IFC schema, enabling data retrieval and analysis. Finally, the analyzed and summarized results of BIM data were represented based on the structure of the retrieved data. A prototype application was developed to validate the proposed approach on the data collected during the construction of the terminal of Kunming Airport, the largest single building in China. The case study illustrated the following: 1 relationships between the user requirements and the data users concerned are established, 2 user-concerned data can be automatically retrieved and aggregated based on the cloud for BIM, and 3 the data are represented in a proper form for a visual view and a comprehensive report. With this approach, users can significantly benefit from requesting for information and the value of BIM will be enhanced.

Significant difficulties remain in exchanging information between building information modeling BIM tools. The industry foundation classes IFC exchange schema is too generic to capture the full semantic meaning needed for direct use by different construction project stakeholders' BIM tools. Although BIM standards that prescribe model view definitions MVD for domain-specific exchanges are under development, insufficient semantic definition of exchanges prevents achievement of the full potential of BIM through seamless interoperability. We propose an innovative approach for supplementing an IFC exchange file with semantically useful concepts inferred from the explicit and implicit information contained in the building model. A prototype software was implemented to test the applicability of the approach. It consists of a rule-processing engine and allows composition of inference rule-sets that can be tailored for different domains. The tests demonstrate semantic enrichment with precast concrete building models, adding inferred joint, slab aggregation and connection concepts.

The planning of large infrastructure facilities such as inner-city subway tracks requires the consideration of widely differing scales, ranging from the kilometer scale for the general routing of the track down to the centimeter scale for detailed design of connection points. On the one hand this implies the utilization of both, Geographic Information Systems (GIS) as well as Building Information Modeling (BIM) tools, for performing the required analysis, modeling, and visualization tasks. On the other hand, a sound foundation of handling multi-scale representations is required. Although multi-scale modeling is already well established in the GIS field, there are no corresponding approaches in Infrastructure BIM so far. However, multi-scale concepts are also much needed in the BIM context, as the planning process typically provides only rough information in the early stages and increasingly detailed and fine-grained information in later stages. To meet this demand, this article presents a comprehensive concept for incorporating multi-scale representations with building information models, with a particular focus on the geometric-semantic modeling of shield tunnels. Based on a detailed analysis of the data modeling methods used in CityGML and the requirements present in the context of infrastructure planning projects, we discuss potential extensions to the BIM data model Industry Foundation Classes (IFC) for incorporating multi-scale representations of shield tunnels. Particular emphasis is put on providing means for preserving the consistency of the representation across the different Levels-of-Detail (LoDs), while taking into account both semantics and geometry. For realizing consistency preservation mechanisms, we propose to apply a procedural geometry description which makes it possible to define explicit dependencies between geometric entities on different LoDs. The modification of an object on a coarse level consequently results in an automated update of all dependent objects on the finer levels. Finally, we discuss the transformation of the IFC-based multi-scale tunnel model into a CityGML compliant tunnel representation.

Virtual Construction (VC) applications encounter difficulty in sharing and exchanging information with one another due to the long periods of interoperability limitation. To address these issues, an Industrial Foundation Classes-based graphic information model (IFC-GIM) is developed according to the exchange requirement of VC, and using the representations of three models in the IFC schema and its extension by defining the dynamic property set and properties for animation. The three models include the physical object model, the construction information model, and the realistic model. An OpenGL-based VC platform is developed and applied to a 440-m-high building to implement the IFC-GIM. The results demonstrate that the proposed IFC-GIM lays the foundation for data sharing and exchange among VC systems and other IFC-compliant applications, which, in turn, significantly reduces the modeling effort for VC and increases the value of VC results. Furthermore, animation is applied to simulate construction activities by the VC platform in addition to color and transparency, enhancing realistic feelings in 4D applications.

After a short discussion of different types of models being involved in the process of numerical simulation in civil engineering, we focus on the analysis of indoor air flow through complex geometries. All models are derived from a product data model based on Industry Foundation Classes. Concepts of the Lattice-Boltzmann method are described, being used as the numerical kernel of our simulation system. We take advantage of spacetrees as a central data structure for all geometry related objects. Finally, we describe some advanced postprocessing and visualization techniques allowing to efficiently analyze huge amounts of simulation data.

Research has been conducted for the appli- cations of Industry Foundation Classes (IFC), developed by International Alliance for Interoperability (IAI) for building product model-based information sharing and exchange. This article presents the results and lessons learned from a research project, titled "A Development of the 3D Object-Based Product Model and Application," jointly performed by the research teams of two universi- ties in Korea. An integrated information system called Design Information Management System (DIMS) has been de- veloped with a focus on representation of design informa- tion based on IFC and its association with schedule, esti- mation, and structural engineering information. With the integration of information from various sources, DIMS can represent project information in multiple viewpoints through the hierarchical classification of building com- ponents. It also calculates the quantities of each building component and helps users to recognize the correspond- ing 3D graphic objects in the CAD system. This article dis- cusses considerations, processes, and methods used dur

As a contribution to the international efforts toward the development of an integrated technology (IT) for managing project information, a major research project has been undertaken at the University of Salford. Based on advances in international standards in data models, i.e., the Industry Foundation Classes (IFCs), and communication protocols, i.e., the Common Object Request Broker Architecture (CORBA), this project has successfully developed and implemented a three-tier computer architecture environment to integrated design and construction applications. The IFC data model has been implemented as the single project database in an open and distributed computer environment whereby the World Wide Web has been used as the delivery medium. This article explains the background of this project, outlines other international efforts in this field, introduces the concept of the three-tier computer architecture, and discusses the proposed structure for the integrated environment along with its implementation issues.