Research On Status Evaluation Method And Monitoring System Of Spatial Latticed Structures Via Dynamic Approach

Large-span structures are widely used in China. At present, over 20,000,000 m~2 large-span structures have been built. It is estimated that there will be over 3,000,000 m~2 being constructed every year, large-span structures in China has generated a great deal of interest and these structures have entered a new era of fast development. A lot of material and new technology have been used, with the structural system and topology more and more complicated, as a result the large-span space structures have been the symbols of the national building science and technology. The large-span space structures are usually used in gymnasiums, airport buildings, exhibition halls, theatres, etc., and most of them are large-scale public architectures which usually house thousands of occupants, so the security of the building is very important. Lots of accidents were reported both home and abroad, most of which were due to the mistakes in design and construction, so it is necessary to carry out the measurement and estimation to buildings after construction. The traditional approach concerns the welding, bolt, displacement etc., while some important parameters such as load and restrict stiffness were ignored in fact. However, the dynamic behavior is usually more important than static parameters. The main research work in article concerns the status evaluation method and measurement system via dynamic approach, and the research work on measurement, estimation and alert to the newly-completed spatial structures or the old buildings in service is valuable and significant.Detailed researches are carried out about condition assessment and health monitoring system of space structures, which are built and completed in recent years. Some related important problems about structural condition assessment are lucubrated and a series of new methods are proposed. The main contents of this dissertation are described as follows:1. The paper illustrates and proves the rule of dynamic character variation against the mass loading changing on space latticed structures in theory, simulation and model test. The result shows that the valiation trends of the first several mode shape and frequency is almost the same when the roof mass load changes, with each mode frequency value increasing or decreasing in same scale, and mode jumping never occurs.2. The paper illustrates and proves the rule of dynamic character variation against the restrict stiffness changing on space latticed structures in theory, simulation and model test. The result shows that the valiation trends of the first several mode shape and frequency is very different when the restrict stiffness changes, with some mode frequencies change obviously while others not so significant, and mode jumping occurs sometimes.3. Based on the rule of dynamic character alteration against the roof load and restrict stiffness changing, a method was proposed to evaluate the roof load and restrict stiffness by combining the changing quantity and rate of first several mode frequencies.4. Compared with traditional wired sensor system and considering the characteristics of spatial structures, we designed and developed the research work on a new type of wireless sensor system, which are more suitable to the measurement application in large-span spatial structures.5. For mini-size, low power, lowcost and high reliability design, the electronic components are compared, analysed and selected. On this base, the modular design method is used for designing and debugging sensing module, micro-processing module, wireless communication module and power supply module, thus a wireless acceleration sensor node with digital interface is integrated using the above modules. The hardware design of wireless sensors are functional modularity, energy efficiency, measure accuracy, configuration flexibility, and network extensibility, which can meet the acceleration measurement requirements in civil engineering.6 . By designing the MCU program on sensor node, we realized wireless communication and constituted the topology of wireless sensor network. The three layer wireless sensor network topology consisting of node-subsidiary base, station-major base and station. And the wireless sensor network can be visited from long-distance while the network system is connected to the Internet. We designed the management software on PC, and realized the function of mode analysis and cable force calculation.