Advanced Materials Research Vols. 163-167

Abstract: This paper studies properties of concrete under the action of water-reducing retarder and expansive agent; gives the optimal design calculation method of cooling water pipe in the construction technology: mainly considering pipe’s diameter, distance, cooling water’s flow, temperature, time etc; studies the optimization to the concretes construction method. Midas/Civil, one finite element analysis soft-ware, analyses mass concrete construction of the whole process of the temperature field and stress field in the numerical simulation, considering the admixtures and construction technology. The results show that commonuse of admixtures and reasonable construction technology are the important means of controlling cracks.

Abstract: Based on the finite strip thought and displacement interpolation function of Bernoulli-Euler beam element, using the transformation relationship between skew coordinate and Cartesian coordinate system, a new kind of thin parallel slab element was established, element stiffness matrix and consistent mass matrix were derived. The vibrating frequency of simply supported skewed slab was calculated. Computing results were compared with theoretical results and Ansys results. The maximum error was 2.68%. Changing the mesh density of skew slab, the convergence of present element was tested. Examples show that this element has the features of high precision and strong convergence. At last, the vibrating frequency coefficients of skew slab bridge with different ratios of span to width were provided, which can be adopted to compute the vehicle’s impact factor of skew slab bridge by specification method.

Abstract: According to the phenomenon of pavement cracking in low temperature in Northeast China, AC-13I and AK-13I of the two gradations, SBS, Methyl Cellulose fiber and steel fiber are adopted to research the mechanics parameters of reinforced asphalt mixture by Indirect tension test at minus 10 degrees centigrade entering on pavement material. Improvement of the low-temperature indirect tensile strength, stiffness and deformation capacity of asphalt mixture is analyzed and mechanisms are revealed. The results indicate that low-temperature crack resistance of steel fiber-reinforced AC-13I asphalt mixture is improved significantly, it is better for the cold area in Northeast.

Abstract: In order to determine the deformation performance index limits for medium-height RC shear wall components based on Chinese codes with the shear span ratio between 1.0 and 2.0, the reliability of the nonlinear finite element method was first verified by four typical medium-height shear wall components experiments in some literatures. Then, the nonlinear finite element method was applied to analyze a set of medium-height RC shear wall components designed according to current Chinese codes. Parametric studies were made of the influence of shear span ratio λ, axial compression ratio μ and main flexural reinforcement ratio of confined boundary members ρflex. Finally, the deformation performance index and its limits of the medium-height RC shear wall components under severe earthquakes are presented by the finite element model results.

Abstract: The corrosion of reinforcement embedded in concrete bridge deck slabs has been the cause of major deterioration and of high costs in repair and maintenance. Fibre reinforced polymers (FRP) exhibit high durability in combination with high strength and light weight. The majority of research with FRP bars for reinforcing concrete has been on simply supported beams and slabs where the low value of elasticity of FRP has meant that the service behaviour has been critical. These differences have been attributed to the low value of elasticity of many FRPs compared to steel. However, laterally restrained slabs, such as those in bridge deck slabs, exhibit arching action or compressive membrane action (CMA), which has a beneficial influence on the service behaviour such as the deflection. Based on the previous research on CMA in steel reinforced concrete bridge deck slabs, a modified theoretical method were established according to the material properties of GFRP reinforcement. The proposed prediction method showed a good collection of some reported GFRP reinforced slabs experimental tests.

Abstract: At present, the national norms of temporary support structure in building construction has not officially promulgated. there was no uniform standard in the structure design and construction, which leaded to the collapse of construction accidents occurring from time to time. Through measuring mechanical behavior of support system of coupler, the statics have obtained that loads of temporary support has been gradually imposed on the structure by step construction in the construction process. Construction loading is a complex process of construction mechanics. The measured axial force is larger than standard one by JGJ130-2001. The results shows the load structure suffered has been not fully taken into account. As the load of erecting pole of top and bottom is not the same, the height of structure bearing capacity has been considered in design. As the second-order effecting on structure, both horizontal rod and bridging bear a certain horizontal force in the construction process. The value of bridging stress is larger. In the structure design calculations, the arrangement of bridging should be paid more attention to improve the stability of the entire frame. The obtained results provides experiment basis for support system designed.

Abstract: The main purpose of damage inspection of the bridge components is to ensure the safety of a bridge and to identify any maintenance, repair, or strengthening which that need to be carried out. The essential damages that occur in reinforced concrete bridge include different type of cracks, scalling and spalling of concrete, corrosion of steel reinforcement, deformation, excessive deflection, and stain. The main objectives of this study are to inspect the appearance of Jiamusi highway prestressed concrete bridge and describe all the damages in the bridge structural components, and to evaluate the structural performance of the bridge structure under dead and live loads. The field tests that are adopted in this study are the depth of concrete carbonation test, compressive strength of concrete test, corrosion of steel reinforcement test, and static load test. According to inspection of the bridge structure appearance, the overall states of bridge structure in good and there are not serious damages, but there are diagonal and longitudinal cracks in the inside web of box girder within block No.8 and 9. Expansion joints suffer from serious damage such as deformation of expansion joint rubber, dislocating, shedding, and cracking. The field test results show that the concrete of the bridge structure has not carbonation; the strength of concrete in good state; there is not corrosion in steel reinforcement; The values of load test for vertical deflection, strain, and stress are less than the theoretical values and the results of cracks observation show that there is not changing in the length of diagonal cracks in the web of box girder when the load test is applied. This indicates that the working state and carrying capacity of the bridge structure in good state.

Abstract: Bond stress between concrete and shape steel makes both materials cooperate as a whole, but diminished at final stage of loading period. A shear model is established to throw illumination on mechanism of bond failure. Tensile stress in concrete leaded to bond cracks and eventually the bond failure, which is due to the shear passing from concrete to shape steel. A new approach for bearing capacity of SRC columns with bond failure is put forward which based on the equivalent law of shear stress and shear stress distribution of rectangular section for formula derivation, the calculated results are consistent with those of the test.

Abstract: The damage process of pure cement pastes with water to cementing material ratios of 0.30, 0.40, 0.50 and 0.60 and fly ash modified pastes with mass fraction of 10%, 30%, 40% and 55% were studied by using ammonium chloride solution with concentrations of 6 mol/l. The total leaching depth, leaching depth, porosity and compressive strength of these pastes leached for 14, 28, 56, 91 and 140 days were tested. The influences of W/C ratio and fly ash content on these properties were analyzed, the relationship between the two factors and the corrosion resistance of pastes was summarized. The results show that the total leaching depth of fly ash modified paste is larger than that of pure cement paste. However, the fly ash modified paste suffers various degree of lowered increment in porosity and strength loss (in percentage) in connection with the added content.

Abstract: In this paper we present a new constitutive model for concrete. The framework is originally proposed for shape memory alloy, a kind of crystalline material. We show how to apply this framework for non-crystalline material: concrete. The resulting yield surface and stress-strain relationship are compared with that of experiment reported in the literature.