Advanced Materials Research Vols. 250-253

Abstract: The local vibration of a bridge under moving train is the source of low frequency noise radiated from the structure. Local vibration of bridges has not been widely studied compared to global vibration that leads to serviceability and safety problems. The local vibration of an urban rail transit U-shaped girder is simulated with the proposed mode superposition based train-track-bridge dynamic interaction model. The computed local acceleration responses under various train speeds are then verified by those obtained from field test, in terms of time-histories, spectra, peak-to-peak values and root mean square (RMS) values. It is founded that the main frequencies of the local acceleration of this girder are below 100 Hz. The proposed method and the computed local vibration could be further applied to predict the bridge-borne noise.

Abstract: Recycle utilization of building waste is the tendency of building material for environment protection & sustainable development. Mechanical properties of molded products using building waste (MPBW) were investigated. The main parameters are focus on molded pressure, dosage of building waste added into cement and fly ash. The results of experiments showed that molded products using concretes debris as fine aggregates have stronger mechanical properties. The strength of product increased along with molding pressure increase under 15MPa , but it was almost no increase when the molding pressure was up from 15MPa to 20MPa.The addition of building waste has little effect on the compressive strength of product when its dosage range from 50% to 100% .The strength of product had obviously changed after using fly ash partially substitute for cement, when fly ash replace two thirds cement, the product strength of 28d was 15.4MPa, and was still higher than that of the normal wall materials. Later strength of the product had markedly increased, its 180d compressive strength achieved 25.2MPa. Test results confirmed: using building waste, panel, block and other products with better mechanical properties could be manufactured by adjusting the molded pressure and the dosage of building waste and fly ash.

Abstract: In this paper, polycarboxylic type high performance water reducers have been synthesized through using TPEG modified monomer. If synthetic temperature and addition time of copolymer monomers can be controlled, the performance of polycarboxylic superplasticizer will be improved. Testing results indicates that when temperature is at 60~65°C, addition time of copolymer monomers is three hours, the performance of superplasticizer is best. Through High Performance Liquid Chroma- tography (HPLC) testing, we can find it is almost the same with the famous brand abroad of the same type. The ues of polycarboxylic type high performance water reducers cooperated with naphthalene series high range water reducing agents thereby markedly improv the workability of concrete mixture.

Abstract: For analyzing reduction vibration effect of high-rise isolated structure with LRB, experimental research on shaking table of isolated structure model on a scale down of 1:16 in two-direction earthquake wave input was conducted. Ratio similitude design of model and earthquake wave input was unified for reflection dynamical characteristic of actual structure in the test. Earthquake responses of isolated top structure acceleration and interblended displacement have been analyzed. The experimental result indicts that isolated top structure acceleration and interblended displacement were reduced. Therefore the isolation technology for high-rise structure also has better reduction vibration effect.

Abstract: Salt Water intrusion is a recurrent phenomenon over the world. This study has purpose to find a new biological way to solve this problem. Sporosarcina Pasteurii, known for its application in biogrouting solutions, was injected into four experimental columns submitted to salt water injection. The bioremediated carbonation reaction was induced by injection of calcium chloride and urea during a three weeks period and results were observed by a new injection of salt water. The increase of salt concentration in the columns after biological treatment shows a slowing down of salt propagation after treatment.

Abstract: The ground fracture already becomes one of main city's geological disasters in China, this geological disaster is quite serious in Xi'an, of Shaanxi province capital city. In this city the ground fracture growth is intense, the causes of the fracture are very complex, the building and engineering structures to be able to have the serious destruction where the fracture passed through its base. In China national civil engineering design codes, the method which designs about buildings on the site of ground fracture is the blank, only Shaanxi Province engineering construction standard gives some specifications for site investigation and engineering design to the Xi'an ground, use the measure that is get out of the way to the building destruction, and rules the smallest required safety distance. Discovers the security problem of the engineering structures located in the ground fracture site is a complex topic, the Shaanxi Provincial engineering design standards have some deficiencies in the theory aspect. Reckon it is necessary to systematically research this topic. These work include more widely and deeply to investigate the ground fractures activity, found the ground uneven settlement modes in fracture belt, and analyzes safe reliability of all kind of building structure on the fracture site, as well as, analyses structures seismic capability.

Abstract: Effective combination and carry-loading together between steel and concrete play important roles for the steel-concrete composite structure. The steel-concrete composite joint decides the constructing safety and life-cycle performance as the key member for the steel-concrete composite arch bridge. The stress distribution in the steel-concrete composite joint was studied by model test under pressure-bending load. And the stress transfer was probed in the steel box, composite joint and reinforced concrete box. The result shows that the steel and reinforced concrete boxes are under elastic compression in the steel-concrete composite joint. The bearing plate can effectively reduce the stress in concrete and steel boxes. This plate and stiffener can smoothly transfer and scatter the stress from steel box to concrete box. The failure mode is concrete cracking near the interface between steel box and concrete box under large eccentric compression.

Abstract: Because double side drift excavation method named eye excavation method has been a mature and reliable excavation method, it has normally been used in tunnels with super cross-section and super large section area. However, the construction speed using this method is very slow. One of reasons is that the construction technology of this method would be more and complex. The other is that all construction workers, materials, equipment would be extremely difficult for their up and down, and that the ballast rock would have to be moved by artificial when the upper step of the middle guide hole would be excavated. In this paper, to speed up the process of excavating tunnel with super cross-section and super large section area underpass extra-high building, the elastic-plastic numerical simulations for the tunnel named Industry and Trade Station of the third line in Chongqing Rail Transit were made in four excavation methods conditions. The four excavation methods is respectively the double side drift excavation method to the first excavation in main building side, the double side drift excavation method to the first excavation in podium side, the single side drift excavation method in the upper step to the first excavation in main building side and the single side drift excavation method in the upper step to the first excavation in podium side. The main building is named Industry and Trade building with 22 floors. The results showed that the single side drift excavation method in the upper step could Insure the building and tunnel when the support measures were reasonable, that the guide hole beside the little surface load should firstly be excavated by whether double side drift excavation method or single side drift excavation method, and that these would provide a reference for some similar engineering.

Abstract: This paper will introduce the basic methods of soil-structure dynamic interaction at home and abroad, and analysis the advantages and disadvantages of these methods. Finally, the paper will put forward opinions on the research tendency of soil-structure dynamic interaction. With the development of urbanization, the urban population, planning area and urban environment are faced with tremendous stress, so developing and utilizing the underground space becomes the concerns of many cities. In recent decades, the underground structure has been widely used in urban construction, transportation, national defense engineering, and hydraulic engineering and so on. Especially in the urban construction, with underground railway which has been seemed as the large-capacity backbone and fast public transport system has become an important issue of urban passenger traffic solution. In our country, there are still large potential in developing and utilizing the underground structure and the structure forms will become more and more complicated. China is a strong and frequent earthquake country, the earthquake-proof problems about the underground structures such as Long-span subway station has become city astigmatic engineering and the important research content on disaster prevention and mitigation. These researches can ensure the safe use of underground structures and reduce natural disasters to humankind. To the subway station and the tunnel structure, soil characteristics significantly influence the structure seismic response and destruction features. In seismic response process, the overburden of gravitational can greatly affect on the structural seismic response. The solution to the underground structure seismic problem should focus on two aspects: on one hand we should focus on the research of soil-structure dynamic interaction; on the other hand, we should deal with soil’s half-limitlessness simulation problem.

Abstract: Based on the brittle fracture theory of composite crack, and then overlapping the stresses at the end region of a crack under tension-shear or compression-shear failure conditions, the relationships of parameters in rock macroscopic and microscopic are determined by combining the Hoek-Brown failure criterion. There are many valuable conclusions through a series of loading and unloading triaxial laboratory tests on rock samples. The tension-shear fracture under the unloading triaxial tests at pre-peak is different from the compression-shear fracture under the loading triaxial tests. The Hoek-Brown criterion for rock is applicable and validity under the condition of loading triaxial tests. Because the uniaxial compressive strength is not the fundamental characteristic of rock, the virtual uniaxial compressive strength is proposed for the first time considering the unloading problem. Comparing with the loading tests, the Hoek-Brown material parameters of rock samples change greatly under unloading at pre-peak, and the virtual uniaxial compressive strength improves and Hoek-Brown material constant m reduces.