Advanced Materials Research Vols. 163-167

Abstract: Based on the theory of diffusion and mass transfer, a theoretical neutralization model for fly ash concrete eroded by acid rain was proposed. The values of the model parameters were studied, and the calculation formula of effective diffusion coefficient DA was established considering both material and environmental aspects. The model was verified by acid rain erosion test results, and the results calculated by the model agree well with test results. The model proposed in this paper can be used to predict neutralization depth of fly ash concrete subjected to acid rain attack.

Abstract: This paper summarizes the theories of the concrete damage under frost action. Based on experiments done by researchers in and abroad, the water conversion and the moisture content change in the concrete during the freeze-thaw cycles are analyzed. In this paper, the affection of the expansion and contraction of ice on concrete at temperatures in the usual freeze-thaw test range is particularly taken into consideration. At last, a qualitative process of the concrete damage under frost action is proposed.

Abstract: An accelerating calculation of reliability analysis on strength and stiffness for frame structure was derived. The method of numerical analysis was combined with recurrence formula, to generatelimit state function of continual variational structure. This methodcan simplify the algorithm for identifying systemic dominant failure modes, because the repeated assembly of global stiffness matrix and repeated inverse matrix operation in analysis are avoided. A new criterion of degenerating the structure into mechanism is introduced. Continual analysis of variational structure can be realized.

Abstract: This paper deals with the steel/concrete interface of a corroded beam B2CL1 after a 23 years exposure in chloride environment. XRD, SEM and Raman techniques were performed to investigate the chemical compositions and the spatial distribution of corrosion products. The experimental results illustrate that the corrosion product layer is a multi-layer constituted as marbling structure. It is composed of a mix of iron oxides and iron oxi-hydroxides. Iron species were found in the vicinity of concrete mainly in cracks, as it was already observed in the literature.

Abstract: The experimental study and finite element analysis of RC beams strengthened with CFRP board are introduced in this essay. Test research of six beams stuck with CFRP board on their tension faces has been carried out on rigidity by contrasting with three non­strengthened beams. Three specimens are primary loading beams and the others are secondary loading beams, the calculating formula for the short-term rigidity on the section of concrete beams strengthened with CFRP board has been established. Calculation is carried out on short-term deflection of RC beams strengthened with CFRP board subjected to primary load and secondary load. The results indicate that the RC structure can be strengthened effectively by sticking with CFRP board, so that the expansion of crack and rigidity of beam can be controlled especially, and the experimental results compared with those predicted by the formula in resemblance.

Abstract: Freeze-thaw cycles have the impact on mechanical properties of the concrete in northern areas of China. In this paper, on the basis of the damage degree of freeze-thaw cycles and experiment data, for C30~ C50 concrete after freeze-thaw cycles, the loss rate of relative dynamic elastic modulus and the relation between compressive stress-strain are analyzed. Compounding good frost resistance of concrete is one of important measures to improve durability of concrete, and degradation patterns of mechanical properties are found. This study may serve as prediction of the service life of concrete in cold regions.

Abstract: The present study describes an experimental investigation on shear behavior of GFRP-concrete hybrid beams, consisting of reinforced concrete beams combined with U-shaped glass fiber reinforced polymer pultruded profile constructed as combined tensile reinforcement, permanent formwork and corrosion resistance. A total of six beams were tested, three served as control beams and the remaining were implemented with U-shaped GFRP composites. Test results show that hybrid beam provides significant increase in shear capacity when compared to control RC beam.

Abstract: At present, seismic strengthening design reference period of the existing building is usually equal to 50 years in China, sometime this is uneconomic and unreasonable. In this paper, determining principle of seismic strengthening design reference period for the existing building with different importance is presented. The seismic strengthening design level of the existing building is put forward. After the shape factor of intensity probability distribution function is used to represent the seismic hazard characteristic of different areas, the seismic hazard curve formula of design acceleration A_max and earthquake influence coefficient α_max are deduced according to the seismic hazard curve of intensity. The seismic strengthening design ground motion parameter for the existing building with different importance is researched in detail by use of hazard curve formula of seismic ground motion parameter based on seismic hazard characteristic zone. At last, the method and the calculation step are explained by a calculation example. The result shows that for the existing building with different design reference period, using same design parameter is unreasonable in different seismic hazard characteristic zone, and the method is more scientific than the code method.

Abstract: In this paper, earthquake-resistance behaviors of existing masonry structures are evaluated based on a certain masonry building. The existing masonry structure is evaluated in its defects of primary design and construction measurements, seismic bearing capacity and durability. Based on results of evaluation, the seismic reinforcement design is introduced for improving earthquake-resistance behaviors of the whole building and its weak positions. In the seismic reinforcement concept design, the ductility of the masonry structure is improved in bearing seismic loading and plastic deformation. Further more, the masonry building is reinforced for avoiding collapse due to the weak positions of its bottom and top layers, stair halls, short walls and wall corners. Evaluation results and the corresponding seismic reinforcement design are significant for safety of both existing and newly designed masonry structures in earth-quake areas.

Abstract: A new method of inflicting equivalent pre stress is suggested to simulate mechanism on reinforcement of pre stress anchor cable on crack prevention of different angle by mini-plastic zone displacement by finite element method. The change rule of displacement of middle points of crack faces, the change of stress strength gene and strain is compared under different pre-stress consolidated condition. When the angle of crack is 450, the consolidated role of rock mass is the best evident. The effect of compression of jointed rock mass is larger than the effect of shear under pre-stress consolidated condition.