Advanced Materials Research Vols. 753-755

Abstract: Based on the experimental data of mechanical performance of carbon fiber sheets, the statistical characteristics are obtained by symbolic statistical method. The characteristics of flexure capability of strengthened beams are established with a certain ratio of the strain of CFS to its ultimate strain for the failure due to the rupture of CFS by Monte-Carlo method. Reliability taking the aboved ratio as variable is analyzed to obtain its optimum value, on the basis of which the lower limit of CFS is decided that makes better consistency between calculated reliability indicator and object reliability indicator.

Abstract: Severe rutting, cracks and moisture damage are presented on conventional semi-rigid base asphalt pavements not long after completed in China. This phenomenon indicates that conventional philosophy on pavement design could not meet more and more frequent and heavy vehicle. With high structural capacity for high traffic volume and heavy loads, the Perpetual Asphalt Pavements (PAPs) solve those problems well. Meanwhile they need minimal or no major structural rehabilitation and/or reconstruction exercises in their life, which ensures low user-delay.Three PAPs, including semi-rigid base asphalt pavement, flexible base asphalt pavement, and combined base asphalt pavement, are put forward for the northeast area in China considering its climate, traffic characteristic. Finite element method is utilized to analyze response of PAPs under heavy loads. Two key factors, i.e. tensile horizontal strains at the bottom of asphalt layers and compressive vertical strains are investigated. Also the capacities of the structures on bearing overloading are estimated. Four types of wheel and axle, including single axle and single tire, single axle and dual tires, dual axles and dual tires, and tri axles and dual tires are adopted in finite element models. The shapes of tire-pavement contact area are either circular or rectangular to simulate standard load or overloading respectively. When rectangular shapes are adopted, the contact area sizes and the distribution of pressure are varied. Conventional asphalt concrete and high modulus asphalt concrete are adopted. Simulations are done. The competences of the three pavement structures on fulfilling long lives are evaluated.

Abstract: Properties of light-weight concrete congaing lightweight expanded clay aggregate differ from the ones of normal-weight concrete containing natural normal-weight aggregate. Particularly, when compared with natural normal-weight aggregate, these differences are due to lightweight aggregate being characterized by significantly lower strength and bulk weight as well as higher absorptivity. Properties of expanded clay lightweight aggregate influence the ones of light-weight concrete, too. Parameters obtained by means of Schmidt impact hammer non-destructive testing are influenced by series of factors, among others also concrete moisture. Moisture of light-weight concrete containing lightweight aggregate influences rebound number of Schmidt impact hammer. As to Schmidt impact hammer type N (2.25 Nm impact energy), rebound number on dry concrete exceeds the one on waterlogged concrete by 21 %. Correction coefficients for rebound number correction were defined taking into account moisture of light-weight concrete under testing.

Abstract: In order to improve the low temperature evaluation, on the basis of the low temperature bending test unit volume destruction to evaluate the low temperature crack resistance of asphalt mixtures. Since the destruction can be indicators of unit volume mixture critical flexural tensile strain and flexural strength of two indicators integrated. Therefore, use it to assess the low temperature crack resistance of asphalt mixture is more scientific, the indicators has also become a new method of low-temperature research areas.

Abstract: This article verifies the feasibility to impact rolling technology instead of dynamic consolidation in soil areas soil region reinforcement processing by impact rolling soil base reinforcement experiments .In this essay, high soil areas embankment large area of reinforcement processing has opened up a new way.

Abstract: Coarse aggregate of asphalt mixture is crucial to the road performance. In this paper, by using the method of uniform design research, particle size of the aggregate were studied influence to CBR value with nominal maximum particle size 13.2mm aggregate. Further to determine the critical particle size grade by gray relational degree theory.

Abstract: The dynamic effect analysis of transient unloading is one of main points to the mechanism of rock fragmentation by blasting. The paper introduces the details of rhe effect of instantaneous unloading to rock fragmentation by blasting. Use the dynamic finite element method to calculate the process of transient unloading of excavation; get some conclusions about transient unloading.

Abstract: In the time of low-permeability sandstone reservoir explored, effective stress rise gradually, stress sensitivity has happened, which cause permeability decline. Allowing to initial geostress, the study on Jilin oilfield Fuxin326 oil layer and made the rock core experiment are presented. The experimental results show that the stress sensitivity of this oil layer is small the regularity of permeability changes is in accordance with exponential function. The stress sensitivity of high permeability core is larger than low permeability. Moreover, experiments and theoretical analysis shows that low permeability core has a smaller permeability loss than high permeability core in load and unload process. Loading and unloading process leads to elastic plastic deformation of rocks, and it is the major reason which permeability can not return completely.

Abstract: Earthquake would cause unacceptable damage in reinforced concrete structures. In this paper, two retrofitting methods based on alternative load path are proposed for the reinforced concrete structure. One method is to add steel braces to the structure, and another one is to add tension cables to the structure. Pushover analyses for all frames are carried out using SAP2000. From the analysis results, steel braces or tension cables delay the formation of the first plastic hinge and failure of columns, and can better improve the seismic performance of reinforced concrete frame. The research results can be utilized for displacement-based seismic design and seismic performance evaluation of RC structures.

Abstract: Propagation characteristics of crack cross different elastic material interface is important to hydrodynamic fracture of control technology .It makes the specimens of rock and similar materials including interfacial layer to do theItype crack through three-point bending experiments. The text shows that the crack occurred deflection through the interface. Based on damage mechanics, establish the plasticity damage model to describe the sand-mudstone damage behavior. Using the numerical solution technology to simulate the loading cracking process, the experimental and numerical simulation results are in good agreement. The main reason causing the fracture deflection is that the difference of sand-mudstone mechanics of materials property results in interface shear stress increasing, and result in the Itype crack expand transform to the I-IImixed type mode crack. TheII type shear crack makes the crack lateral spreading on the interface. Finally, leading to fracture deflection, the extent of deflection is associated with materials properties of mudstone, Shale content is more low, the deflection is more weak, and vice versa. It is important significance to controlling hydro-fracturing fracture extension.