Shear Capacity Calculation Analysis of Reinforced Concrete Beams Based on Truss-arch Model

According to the theory of truss-arch model, the shear mechanism of reinforced concrete beam was analyzed, and formula of shear bearing capacity was proposed. In this formula, softening effect of concrete and the arch function were taken into account, and the coefficients in the formula were amended with experimental data. When the performance difference between the structural material and the original material is huge, the code formula of shear bearing capacity calculation is inapplicable. After the computation, the ratio of the results calculated by truss-arch model theory formula and the results calculated by the current code formula was close to 1, and the standard deviation coefficient and coefficient of variation were smaller than those of standard formula results, and the results calculated by truss-arch model formula were in good agreement with the experimental results. The collected experimental data was calculated with the shear capacity formula in ACI318-08, and the calculation results showed that United States building code was more conservative than the standard of China. The results indicate that the shear bearing capacity formula based on truss-arch model can be used for computation of shear bearing capacity of reinforced concrete beams.     

Experimental Study on Size Effect of Flexural Behavior of Reinforced Concrete Beams

Reinforced concrete specimens with concrete compressive strength varied from 46.5 to 50.6 MPa and with depth of cross section from 250 mm to 1 000 mm subjected to bending were tested. Size effects of flexural behavior with respect to bending capacity and deformation capacity were investigated based on the analysis of the test results and those of high-strength specimens (fcu=72.1~72.4 MPa) of which the geometry and reinforcement layouts were identical to those of specimens tested in this study. It is shown that beam depth does not has any apparent influence on nominal cracking moment, nominal yield moment and nominal ultimate moment, and that it has significant influence on displacement ductility and plastic rotation capacity of plastic hinges of members. For normal-strength concrete specimens and high-strength concrete specimens, both the displacement ductility and the plastic rotation capacity decrease with the increasing of depth in the similar ways, and are independent of concrete strength. It is also demonstrated that the lengths of plastic hinges of members with different depth and concrete strength are approximately equal to the depth.     

Tests on Cracking Behaviors of Reinforced Concrete Beams Underlong- Term Sulphate Attack

In this paper,six reinforced concrete beams dismounted from their worksites under long-term sulphate attack are studied.The authors analyzed the working properties and cracking moment of the reinforced concrete beams under long-term sulphate attack,suggesting that the reinforced concrete beams under long-term sulphate attack may have more favorable cracking-resistant behavior in some circumstances.     

Suggestion for Moment Modulation of Prestressed Concrete Continuous Beams

Based on the information from China and overseas,a design suggestion for moment modulation of post-tensioned prestressed concrete continuous beams with bond has been put forth in this paper. The result calculated by the suggestion is consistent with the result of varying rigidity method.     

Experimental Study on Flexural Behavior of Reinforced Concrete Beams Strengthened With Ferrocement Mortar

Experimental research on flexural behavior of the different grade RC beams strengthened with ferrocement mortar through six RC beams is carried out. The matching of original component concrete to the composite mortar strength rank is studied and its influence on bending strength, the crack-resisting capacity and the bending stiffness of RC beams is analyzed. Based on plane cross-section assumption and the experimental results, the formulas of the theoretical ultimate strength capacity and stiffness are brought forward. The calculated results fit well with the experimental results, to provide a theoretical reference for actual engineering designs.     

Cause Analysis and Treatment Measure on Cracks in New Reinforced Concrete Restricted by Old Web Concrete

In this paper, the cause analysis about cracks on the new concrete web poured in multi -span continuous box -girder of a main bridge was introduced. This bridge is a prestressed concrete one with variable cross sections and an 80 -meter main span. When casting reinforced concrete in large volume in box girder during vehicle transport service, the shrinkage cracks in cast -in place reinforced web concrete were formed due to the restriction of old web concrete. Then, the control measure taken on these cracks is discussed.     

Analysis Theory of Unbonded Prestressed Concrete Continuous Beams

In this paper, the energy method has been used to study the change of the secondary moment of unbonded prestressed concrete continuous beams and it has been contrasted with bonded prestressed beams. The question, whether the secondary moment changes or not while loading, was answered. It shows that the primary secondary moment does not change when increment method is adopted to study the beams, but the total secondary moment will change while the force in prestressed reinforcement changes.     

Fractal Dimension Study of Sky Types

Zenith luminance converting factor is the characteristic parameter of sky luminance distribution,which is not related to regions.The fractal dimension value of the change process of zenith luminance converting factor shows that the sky can be divided into four types as CIE standard clear sky,pseudo- clear sky,pseudo- overcast sky and CIEstandard overcast sky.This is more suitable for the study of sky lumimance distribution with the exception of a few particular weather conditions.     

Investigation on Shear Strength of Reinforced Concrete Beams without Web Reinforcement

On the basis of available testing data of simply supported reinforced concrete beams without web reinforcement under two-point concentrated loads,the dominant factors contributing to shear performance are identified,and the basic laws are correspondingly quantitatively described.The shear design equations of China Design Code of Reinforced Concrete Structures,ACI Code,together with two other expressions of shear of RC beams without web reinforcement,are thus calibrated to identify their accuracy in describing the shear mechanism of such members.     

Study on Sky Luminance Distribution with Fractal Theory

Based on the fractal principle, this paper suggests a calculating expression of the relative luminance distribution in cloudy sky which belongs to the category of intermediate sky, it was proved to be suitable.     

A Fractal Model of the Microstructure

In this paper,a fractal model about the microstructure of spheroidal-graphite is presented through the research on the surface form and the analysis to microregion. The fractal dimension is calculated and the forming mechanism is also discussed.     

Effect of Varying Longitudinal Reinforcement Ratios on Shear Behavior of Reinforced Concrete Beams Without Web Reinforcement

Effect of varying longitudinal reinforcement ratios on shear behavior of reinforced concrete simply supported beams without web reinforcement was analyzed in this paper, with emphasis on both shear ultimate capacity and failure mode, on the basis of available testing data. Generic laws were thus obtained and codified methods, including ACI Code and China Design Code of Reinforced Concrete Structures, were evaluated as a result.     

Effective Thermal Conductivity of a New Material of Graphite Foam Based on Fractal Theory

The new material of graphite foam is a good thermal-conductivity material. With fractal theory, the fractal character of this novel porous material is discussed. Then a thermal-conductivity model of graphite foam is proposed. The relationship formula of effective thermal conductivity is presented by using thermal resistance method. The volume fractal dimension and effective thermal conductivity of this material are calculated. This new method for calculation is significant for porous material.     

Experimental Study on the Extended Length of Negative Reinforcement Cut-in Phases in Continuous Beams

In this paper through the static loading tests of 6 inflexion zones and 2 cantilever zones in full-size constrained R/C beams, the stress performance in rebars cut-in-phases and subjected to negative moment is studied. The stress properties of extended length of rebars with different shear-span ratiosare analysed on basis of the full measurement of strain distributions combined with the investigation on state and regularity of the diagonal cracks development and series of new knowledge are obtained. It is found that current Concrete Design Code provisions on the extended length are inadequate for the high shear-span ratio and superfluous for the low shear-span ratio. The theoretical and experimental foundations are provided for determining proper value of extended length for rebars cut-in-phases.     

基于DEM 的重庆长江流域水系分维估算

摘要：基于数字高程模型,本文利用ArcGIS9.3的水文分析模块,根据不同的集水面积阈值, 提取了重庆长江流域河网信息,通过网格法计算了相应的水系分维。根据集水面积阈值与水系分维的相互关系, 确定该流域水系分维值为1. 036,经计算得到的河网特征以及流域信息与实际河流水系特征及流域信息基本吻合。     

Application of Fractal Theory in the Petroleum Gas Testing of Seismographical Channel

The seismographical channel is a chaotic time series.The trajectory of the motion of chaos in some region of the phase space via fold,torsion and stretch infinite times,constitutes a self similarity structure with infinite hierarchical imbeddings.We process the date of cross section of reflection point of the joint wells which are composed by the signals of the practical seismographical channel,using the method of reconstructing phase space (i.e. the Grassberger Procaccia algorithm) to compute the correlation dimension of each channel,and compared with the data of the practical drilling wells,and we explain the relationship between the correlation dimensions and the results of the drilling wells.They are agreeable quite well.     

Test on Seismic Behaviors of Reinforced Concrete Beams Composite Rehabilitation with Bonded Carbon Fiber Reinforced Polymer and Steel Plate

Neither the Carbon Fiber Reinforced Plastic nor the steel plate strengthening concrete components shows sufficiency in improving the structures' seismic behaviors independently, while they complement each other by the way of composite strengthening. Six reinforced concrete beams, five of which are strengthened, were comparatively and experimentally tested under low frequency cyclic load to investigate their mechanical performances such as characteristic of resilience, hysteretic curve, seismic behaviors, skeleton curve, degeneration of rigidity and loading capacity. It is indicated that the way of composite strengthening can boost the beams′ ultimate bearing capacity, ductility and deformability capacity effectively, and it can delay rigidity degeneration and improve the seismic behaviors of the beams. Also, the CFRP and steel plate can work together very well.