Study On Seismic Analysis And Design Method For Urban Viaduct With Single Column

Efficient and accurate seismic analysis as well as design for urban viaduct with single column is one of the urgent problems to be solved in engineering seismic field at home and abroad. According to transportation hall of Zhejiang province’s science and technology planning project, study on single column pier’s reasonable structural type and practical designing method, and construction department of Zhejiang province’s research promotion program, performance-ba-sed seismic theory analysis and experimental research for the pier of urban viaduct with single column. Based on this background, seismic analysis, design and evaluation methods for single column pier and bridge system have been conducted by relevant numerical calculation and theoretical analysis. Details of this study are mainly summarized as follows:(1) Seismic performance analysis for single column piers with different construction technology has been conducted based on different plastic hinge models. The most suitable plastic hinge model corresponding to each seismic evaluation indicator has been obtained. The studies can provide theoretical guidance for bridge seismic workers.(2) An improved nonlinear random vibration pseudo excitation method based on statistical linearization has been proposed. It breaks the bottleneck of low computing efficiency with random vibration method. It is more accurate than response spectrum analysis, and more effective than dynamic time procedure analysis. Taking urban viaduct with single column as the research example, and corresponding to the related influence parameters such as different height of pier, various span and span number, different apparent wave velocities and different coherent effect, we can find that the bottom of the pier’s internal force and displacement have different change laws as well as the top of the pier. The studies can provide accurate theory basis for seismic analysis of urban viaduct with single column.(3) Seismic fortification levels, performance levels, and the corresponding performance objectives for urban viaduct have been analyzed based on performance seismic design. Combined with the advantages of fuzzy logic control method, neural network method and the adaptive genetic algorithm, a performance-based seismic design method which considered the single column piers’ nonlinearity has been put forward. Through calculating single column piers with different cross section types, we can see that the optimal design result determined by this new algorithm not only satisfies seismic grade requirements and structure performance requirements, but also minimizes the construction cost. Pushover method has been used for analysis of the design results. Its’ capacity curve and test hysteresis loop’s envelope curve are basically the same. It shows that the proposed algorithm has good practicability and accuracy. Using this algorithm for seismic design of an urban viaduct’s pier, the optimal model can be determined easily, accurately and efficiently.(4) According to reliability theory and seismic energy analysis method, seismic design method based on hysteresis energy for urban viaduct with single column has been proposed.Through a case study, we can see that dynamic reliability is related to seismic spectra intensity factor and steady duration for urban viaduct with single column. Dynamic reliability will gradually decrease along with spectra intensity factor and steady duration.(5) Based on performance and seismic reliability, seismic performance theory has been analyzed under different seismic fortification levels for urban viaduct with single column. Through a case study, reliability research on the pier and the overall bridge have been conducted using nonlinear random finite element method and probability pushover method. We can see that the failure probability of whole bridge is greater than single concrete element, the failure probability of whole bridge will increase with the increase of PGA and magnitude, bridges are more likely to be damaged under the lateral seismic input, and it puts the structures at greater earthquake risk. The calculation results are basically identical using nonlinear random finite element method and probability pushover method, but the former’s calculated value is smaller and conservative.(6) Based on full probability theory and performance earthquake engineering framework, and taking IDA method into consideration, probabilistic seismic demand analysis has been conducted for the bridge structure. Combine seismic fragility curves with seismic hazard analysis, numerical simulation and calculation have been conducted for eight samples of urban viaducts with single column selected by Latin hypercube sampling method. Seismic performance evaluation from the sense of probability has been conducted eventually. We can see that eight samples of viaducts all satisfy multiple seismic fortification levels under the lateral and longitudinal seismic input. No matter at which performance level, the bridge samples can work normally, and have higher security reserves. It provides a simple and reliable seismic performance evaluation method for bridge workers.