With the steady growth of China's economy and the increase of infrastructure scale, the scale of construction projects is getting larger and larger, and the structural forms are becoming more and more complex, which puts forward higher and higher requirements for the scientific and accurate management of civil engineering. Realizing informatization, intelligence, visualization and integration of civil engineering has become the requirement of modernization of civil engineering project management and the research hotspot in this field. Virtual Reality (VR) is a comprehensive and highly integrated high-tech, which is widely used in military, medical, design, art, entertainment and many other fields. The virtual reality technology of civil engineering involves various disciplines in the field of civil engineering, and has shown certain practicability, huge technical potential and broad application prospects [1].
Second, virtual reality technology and its characteristics
Virtual reality technology, also known as spiritual realm technology, is a brand-new comprehensive information technology that rose at the end of the 20th century. It combines digital image processing, computer graphics, multimedia technology, sensor technology and other branches of information technology, which greatly promotes the development of computer technology. VR technology is to transform the abstract and complex computer data space into something that users are familiar with intuitively. Its technical essence lies in providing an advanced man-machine interface. The local world generated by VR technology is artificial, not real, but when users enter this local world, they feel basically the same as the real world. Therefore, virtual reality technology has changed the boring, rigid and passive state between people and computers, and provided users with a humanized virtual information space. It creates a three-dimensional image world that reflects real-time physical changes and interactions for users through simulation, so that participants can directly participate in and explore the effects and changes of the environment in which virtual objects are located in the realistic experience of seeing, listening, touching and smelling, as if they were in the real world. Immersive virtual environment system is a large-scale integrated environment composed of subsystems with different functions and levels, including computer graphics, image processing and pattern recognition, intelligent interface technology, artificial intelligence technology, multi-sensor technology, voice processing and audio-visual technology, network technology, parallel processing technology and high-performance computer system. Therefore, virtual reality technology is a highly comprehensive high-tech information technology. Virtual reality technology has the following three characteristics.
1. Immerse
Virtual reality technology is based on the physiological and psychological characteristics of human vision and hearing, and realistic three-dimensional images are generated by computers. Users can put themselves in the virtual environment and become a member of the virtual environment by wearing interactive devices such as helmet display and data gloves. In the virtual environment, the interaction between users and various objects, just like in the real world, all the feelings are so realistic and there is an immersive feeling.
2. Interaction
Human-computer interaction in virtual reality system is an almost natural interaction. Users can interact not only with computer keyboards and mice, but also with special helmets, data gloves and other sensing devices. Users can check or manipulate objects in the virtual environment through their own natural skills such as language, body movements or movements.
3. Multiple perceptions
Because the virtual reality system is equipped with visual, auditory, tactile and kinesthetic sensing and response devices, users can get a variety of senses such as visual, auditory, tactile and kinesthetic in the virtual environment, so as to achieve immersive feelings.
3. The application of virtual reality technology in civil engineering
1. Application prospect of virtual reality technology in civil engineering
In civil engineering, people have to use abstract concepts to express very rich contents for a long time, such as using plan, section and elevation to form some prescribed symbols to represent three-dimensional buildings, and using abstract graphics and concise language to describe complex scenes to convey a lot of information. However, this way of information processing and transmission is influenced by the occupation, knowledge structure and understanding ability of the information receiver, so it is very difficult to communicate.
The development of virtual reality technology provides us with an extremely effective means to overcome this difficulty. Virtual reality can represent both the real world and the virtual world. When expressing the real world, we can break through the limitations of physical space and time to "transcend reality"; When representing the virtual world, it can also make the virtual objects in it show a three-dimensional sense of reality, so as to achieve the feeling of being there, and finally form a "three-dimensional information space that allows people to immerse themselves in it, transcend it, enter and exit freely and interact". Virtual reality technology provides users with a new man-machine interface. It uses computer to generate interactive three-dimensional environment, which can not only make participants feel the realistic existence of scenes or models, but also make real-time and accurate responses to participants' actions and operations.
2. The application field of virtual reality technology in civil engineering.
Due to the above advantages, virtual reality technology has been widely used in civil engineering and has broad application prospects. At present, the application of virtual reality technology in civil engineering mainly includes the following aspects [2].
Application of (1) in virtual construction process and construction structure calculation [3]
In practical engineering construction, the design of complex structure construction scheme and the calculation of construction structure are difficult problems. The key of the former is to express the spatial relationship between structural members and mechanical equipment in the construction site. The latter is that the deformation of the construction structure under construction state and load is greater than that after it is in place or after the structure is formed.
The design of complex structure construction scheme based on virtual reality refers to the establishment of three-dimensional CAD models (virtual models) of surrounding scenes, structural components and mechanical equipment in virtual environment, forming a computer simulation system with certain functions, making the models in the system have dynamic performance, assembling the models in the system in a virtual way, and modifying the construction scheme in the visual environment of human-computer interaction according to the results of virtual assembly. There are many factors involved in the construction of complex structures, such as the layout position and height of cranes, the selection of the center of gravity of cable wind rope, the location of component yard, the running route of cranes, the hoisting route of components, etc. All these must be considered in the design of construction scheme. If these problems are not considered enough, it will affect the progress and cost of engineering construction, and even lead to safety accidents.
Before the construction of a building structure, it is often necessary to check the stress state of the construction scheme. For example, in the construction of long-span spatial structures, not only the safety and feasibility of the construction process, but also the safety and reliability of the structure itself should be considered. In an exhibition center, the steel roof is supported on a steel mast, and both ends of the mast are tapered and hinged with the lower concrete structure. In order to reduce the deformation of steel truss and maintain the stability of the structure, a series of stay cables (front cables, rear cables and stability cables) and stay rods are adopted between steel roof truss and concrete to form a stable structural system. In the steel structure construction, different support schemes and different splicing schemes will have different effects on different parts of the structure, and with the installation of connecting rods, the stresses in these construction stages will remain in the structural parts, which will affect the final structural stress safety; Moreover, instability and deformation may occur in the process of the structure in place. This requires an accurate analysis of the construction process. Using virtual reality technology, we can analyze a lot of different schemes in a short time, thus ensuring the optimization of construction schemes.
(2) Application in engineering bidding.
The construction industry is the pillar industry in China, and the excessive competition in the construction market has been a long-term fact. Owners are in an absolutely favorable position in the operation of modern construction projects. In a limited time, how to make the owner and bid evaluation experts fully understand the preparation and approval of bidding documents is directly related to whether the contractor has the opportunity to win the bid. Therefore, the contractor not only pays attention to the technical feasibility and reasonable quotation of the bidding documents, but also pays great attention to the packaging of the bidding documents. Especially for large-scale projects, national key projects and international projects, the operation in this respect often begins at the project planning stage [4].
With the help of virtual simulation system, the construction process and method that can't be previewed are displayed, which not only saves time and construction investment, but also does not require the project manager to reply on the spot, and the advantages and disadvantages of the scheme are clear at a glance. This undoubtedly greatly increases the chances of the contractor winning the bid.
(3) Application in the field of visual computing
Visual computing will be an important development direction in the future. In scientific research, people will encounter a lot of data. In order to draw valuable rules and conclusions from it, it is necessary to analyze the massive data carefully. The data obtained by scientific calculation can be visualized or displayed in three-dimensional graphics, and the whole picture of the calculation results and their changes can be observed by changing the parameters interactively, so as to realize parameterized and visualized calculation, and virtual reality technology has developed by leaps and bounds.
When the finite element method is used to analyze the structure, the virtual reality technology can be used to give the stress situation of each point in the three-dimensional object through the depth of color, and different colors can be used to represent different isobaric surfaces; You can also change the angle at will and observe from any point. You can also use the interactive performance of VR to modify various data in real time, so as to compare various schemes and results. This makes the engineer's thinking more intuitive and the concept easier to understand. Applying visual computing technology to the design, engineering control and structural analysis of super-large complex structures will enhance the pre-and post-processing ability of computing software. For example, in the visual calculation of bridge engineering control and structural analysis, the dynamic demonstration of reverse (demolition) analysis structure, the display of ideal construction line type of structure, the display of design curve and measured fitting curve of main girder centroid in construction stage, the dynamic demonstration of forward branch bridge structure assembly, the graphic display of construction prediction, the display of internal force diagram of main girder, the display of stress distribution map of dangerous section and so on. More importantly, it can dynamically control the reanalysis of the structure and obtain the construction control data by means of graphics or images, and at the same time, it can dynamically demonstrate and control the design and construction process in real time.
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