In order to analyze the load carrying capacity of prestressed concrete box girders, failure behaviors of in-situ deteriorated continuous prestressed concrete box girders under loading are experimentally observed and a...In order to analyze the load carrying capacity of prestressed concrete box girders, failure behaviors of in-situ deteriorated continuous prestressed concrete box girders under loading are experimentally observed and a finite failure analysis method for predicting behaviors of box girders is developed. A degenerated solid shell element is used to simulate box girders and material nonlinearity is considered. Since pre-stressed concrete box girders usually have a large number of curve prestressed tendons, a type of combined element is presented to simulate the prestressed tendons of box girders, and then the number of elements can be significantly reduced. The analytical results are compared with full-scale failure test results. The comparison shows that the presented method can be effectively applied to the failure analysis of in-situ continuous prestressed concrete box girders, and it also shows that the studied old bridge still has enough load carrying capacity.展开更多
To analyze the characteristics of ground vibration caused by blasting demolition of urban overpass, in this paper we introduced the measurement method and then studied the characteristics of recorded ground vi- bratio...To analyze the characteristics of ground vibration caused by blasting demolition of urban overpass, in this paper we introduced the measurement method and then studied the characteristics of recorded ground vi- brations. Through the analysis of peak acceleration, peak frequency and duration, results indicated that the ver- tical component of vibration is the most important in the region close to the collapse point; the collapse of bridge segments will lead to superposition of ground vibration, and isolation measures can reduce the peak ac- celeration but increase the duration of vibration; blasting and collapse vibration cause no damage to the re- served structure which indicates that blastin~ demolition is a safe and effective method.展开更多
The key technologies of precision blasting were put forward based on the characteristics of urban via- duct blasting demolition in complicated surroundings. Initial bending instability mechanics model of reinforcing s...The key technologies of precision blasting were put forward based on the characteristics of urban via- duct blasting demolition in complicated surroundings. Initial bending instability mechanics model of reinforcing steel bar frame of blasting fragmented pier and sequenced collapsed dynamic model were established for quanti- tative blasting design. Technologies of water pressure blasting were applied in multi-cell box girder fragmenta- tion. The detonating network of non-electric duplication crossover was adopted for the safety and reliability of ultra-long delay. The rationality of blasting scheme and parameters were validated by physical model test. Harm- ful effects were forecasted and controlled by integrated protective technologies. Specialization, cooperation, pre- cision, execution （SCPE） project management method was put forward for precision management. The key tech- nologies of precision demolition blasting can provide reference for similar proiects.展开更多
基金Post-Doctoral Innovative Projects of Shandong Province(No.200703072)the National Natural Science Foundation of China(No.50574053)
文摘In order to analyze the load carrying capacity of prestressed concrete box girders, failure behaviors of in-situ deteriorated continuous prestressed concrete box girders under loading are experimentally observed and a finite failure analysis method for predicting behaviors of box girders is developed. A degenerated solid shell element is used to simulate box girders and material nonlinearity is considered. Since pre-stressed concrete box girders usually have a large number of curve prestressed tendons, a type of combined element is presented to simulate the prestressed tendons of box girders, and then the number of elements can be significantly reduced. The analytical results are compared with full-scale failure test results. The comparison shows that the presented method can be effectively applied to the failure analysis of in-situ continuous prestressed concrete box girders, and it also shows that the studied old bridge still has enough load carrying capacity.
文摘To analyze the characteristics of ground vibration caused by blasting demolition of urban overpass, in this paper we introduced the measurement method and then studied the characteristics of recorded ground vi- brations. Through the analysis of peak acceleration, peak frequency and duration, results indicated that the ver- tical component of vibration is the most important in the region close to the collapse point; the collapse of bridge segments will lead to superposition of ground vibration, and isolation measures can reduce the peak ac- celeration but increase the duration of vibration; blasting and collapse vibration cause no damage to the re- served structure which indicates that blastin~ demolition is a safe and effective method.
文摘The key technologies of precision blasting were put forward based on the characteristics of urban via- duct blasting demolition in complicated surroundings. Initial bending instability mechanics model of reinforcing steel bar frame of blasting fragmented pier and sequenced collapsed dynamic model were established for quanti- tative blasting design. Technologies of water pressure blasting were applied in multi-cell box girder fragmenta- tion. The detonating network of non-electric duplication crossover was adopted for the safety and reliability of ultra-long delay. The rationality of blasting scheme and parameters were validated by physical model test. Harm- ful effects were forecasted and controlled by integrated protective technologies. Specialization, cooperation, pre- cision, execution （SCPE） project management method was put forward for precision management. The key tech- nologies of precision demolition blasting can provide reference for similar proiects.
