UNDERSTANDING BRITTLE FAILURE OF CONCRETE AGAIN

On the basis of analysing the cause of brittle failure ofconcrete,a conclusion that it is necessary to distinguish brittleness andbrittle failure and a new point of view about evaluating brittleness ofconcrete are proposed.A simple and reliable method about the directtension test of concrete is analysed theoretically.     

CARBONATION OF THE AUTOCLAVED SILICATE CONCRETE

The carbonation of the concrete in the air is an unavoidable natural process,Itmakes the volume and strength of the concrete change and the alkality reduce,So the structure in-side concrete and the durability both become worse. The carbonation resistance of the autoclaved sil-icate concrete is tested by the means of speeding up the carbonation artificially and also with the ex-periment of the natural carbonation for 6 years. It is very good for recognizing it correctly andspreading.The carbonation of the new concrete material is discussed.     

STUDY ON THE HARDENING AGENT OF LIME-SAND CONCRETE

his paper introduces M and KM agents used in cement concrete successfully asearly strength agents.They are used in lime-sand concrete in the laboratory.Through the experi-ments,it is verified that both agents can increase the strength of lime-sand concrete on weaker auto-claving conditions and KMagent is better than M agent.Under the condition of this experiment,theoptimum proportion of the agents in lime-sand concrete and the optimum autoclaving schedules areexplored and the effects of saving energy of the two kinds of agents are estimated.     

A STUDY OF THE HYDRATION AND STRENGTH DEVELOPMENT OF SPONTANEOUS COMBUSTION GANGUE CEMENT

In this paper, by means of X-ray analysis and scanning electron microscope technology, the hydration and strength development of spontaneous gangue cement under the condition of normal atmospheric temperature and steam curing are analysed. This work provides experimental and theoretical basis for the usage of spontaneous combusted gangue cement.     

THE STUDY OF ANTI-SEISMIC BEHAVIOR OF THE TOP CORNER JOINTS OF REINFORCED CONCRETE FRAME WITH THE INCLUSION OF STEEL FIBRES

This paper first discusses the limited effect of steel fibre reinforcement on plain concrete and reinforced concrete. Then, making a comparison among the test results of three full-scale top corner joint assemblies of frame, in which only two of them are added with steel fibres in joint zone. The advantageous and disadvantageous influence in anti-seismic aspect is investigated after adding steel fibres in the joint zone. Finally, this paper gives an overall comment on the application future of using the steel fibres in every kinds of joint of anti-seismic reinforced concrete frame.     

储粮熏蒸剂的发展动态与前景

本文扼要介绍了当前主要储粮熏蒸剂的发展动态与前景，包括溴甲烷的淘汰问题、磷化氢的现状与前景、熏蒸能力有限的敌敌畏、面临淘汰的氯化苦、对环境友好但应用成本较高的二氧化碳和氮气、研究中的氧硫化碳和甲基磷、重新评价的甲酸乙酸、二硫化碳、环氧乙烷等的情况，并对新熏蒸剂研究开发前景进行了简单分析。     

THE DETERMINATION OF A CRACK IN STEEL FIBRE REINFORCED LIME-SAND CONCRETE

This paper studies the determination of a crack in steel fibre reinforced lime-sand concrete and its precision by acoustic emission(AE).The main AE paramters which influencethe precision of the determination of a crack are introduced,The properties of the lime-sand concretecan be increasted greatly with the steel fibre,The result in this paper can be used in the study of fi-bre re inforced cement concrete.     

THE FULL LOADING HISTORY ANALYSTS OF PRESTRESSED CONCRETE GRIDS WITH UNBONDED TENDONS

This paper presents a matrix structural analysis of variable stiffness on the complete loading history of prestressed concrete grids with unbonded tendons. A model of torsional rigidity affected by moment is derived by the analogy of space truss, and the effect of torque on flexural rigidity is also studied. In order to calculate the increment of stresses in tendons, a corresponding equation is created. Comparison of calculation shows well agreement with the experimental results.     

BAND DAMAGING CRACK MODEL OF CONCRETE

This paper presents a fracture model of concrete,band damaging crack model (BDCM).The BDCM can be used to analyze mechanical behaviour of concrete effectively and easily.Compared with test results;numerical results calculated by the BDCM are very precise.     

BEHAVIOR OF THE REINFORCED CONCRETE FRAME CORNER JOINTS SUBJECTED TO CLOSING LOADS

In this paper, experimental results on the tests of 15 full-scale reinforces concrete frame corner joints subjected to closing loads arereported. The primary variables are the compressive strength of eoncrete, thesteel ratio and the ratius of main bar bend. In order to investigate the stressdistributiens of the concrete in the cores of the joints, a nonlinear finiteelement analysis of the frame corner jonts is carried out. Possible damage andfailure modes of the frame corner joints are discussed herein. Based on observedand computed results, the formulae in terms of the steel ratio and the ratius ofmain bar bend and the corresponding useful recommendations are made for thedesign of the frame corner joints.     

A PRELIMINARY STUDY ON THE FRACTAL DEMENSIONS OF LIME SAND CONCRETE

Fractal geometry is a branch of applied mathmatics in 1975,and it is used to describe the surface character of irregular bodies. This paper applies fractal demension to study the micropores structures of lime sand concrete,and concludes that it can be used to describe the microp-ores. Their radii are less than 100A. The fractal demensions of lime sand concrete are measured by MlP(mean indicated pressure) technique. The results have shown that the stronger the autoclaving schedules,the less the fractal demensions of lime sand concrete;the larger the water solid ratio(W/S),the larger the fractal demensions,and the calcium silicate ratio(C/S) has the effect on the fractal demensions of lime sand concrete. A pore structure parameter, mean pore radius is also proposed.     

NUMERICAL CONCRBTE-SIMULATING OF MESO-LEVEL STRUCTURE OF CONCRETE

Theoretical analysis on the numerical simulation meso-level structure of concrete is sttJdied systennatically a ndsome simulated restiIts are givL1ii in this paper.THL3 existi ng prub-lems on the numerical simulation of meso-level structtire and discussed.     

A STUDY ON HYDRATE AND CARBONATE RESISTANCE OF CONCRETE WITH GANGUE CEMENT

This paper studies the hydrates and the characteristicsof micro-structure of concrete with gangue cement before and after carbonation under different curing conditions.It is compared with Portlandcement concrete,and the carbonate resistance of concrete with ganguecement is studied too.     

CALCULATING SYSTEM FOR SECOND-ORDER EFFECT IN THE COLUMNS OF REINFORCED CONCRETE FRAMES

This paper makes an analysis and comparison of the calculatingsystem for second-order effect in columns of reinforced concrete frames proposedby scholars at home and abroad,and the systems adopted by codes of manycountries.The focus is on explaining the conceptual error and deficiency in somemethods.After expounding the basic law of the second-order effect in framecolumns with different restraints,this paper suggests an improvement of thecalculating system for second-order effect in frame columns for China's DesignCode of Concrete Structures.     

RESEARCH ON THE SHEAR RESISTANT BEHAVIORS OF STEEL REINFORCED CONCRETE RESTRAINED BEAMS

In order to probe into the shear resistant behaviors ofsteel reinforced concrete(SRC)restrained beams,three test beams underconcentrated loads have been tested.A full range analysis of the testbeams is conducted by using nonlinear finite element(NLFE)techique,and a good agreement with the experimental results is achieved.Theshear resistant mechanism of SRC restrained beam and the main factorsaffecting its shear strength are analysed.It is found that when theavailable shear strength formula for simply supported SRC beams is usedto calculate the shear strength of SRC restrained beams,the result turnsout to be conservative,so it is suggested that the shear strength of SRCrestrained beam could be calculated by the corresponding formula ofsimply supported SRC beam,adopting calculation shear span ratio.Thepractical formula is proposed in the paper.     

MODIFIED BURGERS MODEL AND ITS APPLICATON TO HARDENED CONCRETE

In this paper, an exponential function is introduced to modify the viscous element of Burgers model. The result shows modified Burgers model is advantageous to describe the creep behavior of hardened concrete and the creep test results are in good agreement with the theoretical predictions of creep equations derived from modified Burgers model.     

TENTATIVE INVESTIGATION OF THE BEHAVIOR OF REINFORCED CONCRETE FRAME CORNER JOINTS UNDER LOW CYCLE LOADING

In this pager, four full-scale corner joint assemblies of reinforced concrete frame beam and column with different detail structure are tested under low cycle loading, The process of damage development and the characteristics of break of the assemblies in the course of alternately increasing positive and negative bending deformation are learned Strength, stiffness and ductility of assemblies and the various regulations of energy consumption are also studied. Compared with these properties, the anti-seismic behavior is tentatively commented. Besides, the test results of the strain distribution of beam and column longitudinal bars and stress state of joint stirrups are analyzed.