THE EVALUATION OF SHEAR STRENGTH TAKING ACCOUNT OF SPAN-TO-HEIGHT RATIO OF SIMPLE BEAMS UNDER UNIFORM LOADS

By introducing the span-to-height ratio,this paper deduces wo evaluating equations of shear strength of simple reinforced concrete beamwith stirrups and under uniform loads.This makes the shear stressing concept consistent with the evaluating equations,thus improves the evaluating equationsof shear strength of the New Code.Two equations are provided with auto-regulating function on shear strength for a cross section of beam.They aresimple and convenient in evaluation.The working time used for design is not increased and 10% of stirrups is economized in frequent conditions of span-to-height ratio.     

Experiments on influence of slurry kinds on mechanicalbehavior of interface between gravel and concrete

The mechanical behavior and mechanism of the interface between structure and coarse grained soil are investigated through simple shear tests on the conditions of bentonite slurry, clay slurry and without slurry, respectively. The results indicate that different kinds of slurry have important influence on shear strength. Compared with the interface without slurry, the shear strength with bentonite slurry reduces by 45% approximately, significantly more than clay slurry which reduces by 10%. The value of the friction angle with bentonite slurry is about 60% of that with clay slurry. Shear displacement increases as upright stress increases when reaches its failure states at the same height, and shear displacement with bentonite slurry is smaller than that with clay slurry when with the same upright stress and height. The upright displacement with bentonite slurry is greater than that with clay slurry under the same upright stress. In addition, shear dilatation is apparent under the low normal stress when without slurry. Otherwise, it appears as shear contraction.     

Simulation and analysis of mechanics of coal and gas delay outburst

The buried box girders in the mountain city sewage pipeline system would be turned into simple-supported girders because of the removal of the foundation caused by landslide.This change of supporting would result in the failure risk of pipeline structure.The static properties of the buried box girders with small depth-to-span ratio in simple-supported condition are experimentally analyzed.The failure pattern,shear behavior and shear lag effect of the buried box girders in simple-supported condition are studied.The shortages in the present design codes for the calculation of shear capacities of the box girders are also discussed.It is shown that under the vertical uniformly distributed load,the crack distribution of the box girders is uniform,and no major critical diagonal crack is formed,and the box girders lose the bearing capacity in the form of concrete diagonal rod crushing.As the main shear-bearing components,the stirrups devote much to shear capacity of the box girder after concrete cracking.The strains of the longitudinal rebars are affected by those factors such as the redistribution of internal force and cracks,so only few areas of the box girders show the shear lag effect.The change of supporting form leads to the premature cracking of concrete and affects the serviceability of the sewage pipeline.     

A Study on the Response of Brick Masonry Structure under Dynamic and Static Shear-Compression Loading and Suggested Shearing Equation

Based on the studies and experiments of the responses of brick model under dynamic and static shear-compression loading, this paper brought forward an equation as a transition one for standard of masonry structure design in revision and the standard of aseismic building design. With its simple form, definite concept and similar calculation results in comparison with those obtained by equations from two standards, this equation has realized the correlation of the old and new ones. Besides it is rather save, so it has given a new advice for the revision of the standards.     

The Seismic Shear Capacity of I-Shaped and T-Shaped Reinforced Concrete Structural Walls

There are numerous shear walls with flanges in the high-rise buildings in P.R.China.The shear strength formula for shear walls in Chinese design codes lacks experimental data,while test results in other nations lack aseismatic shear strength test results for shear walls with flanges under axial force.In this paper,we report low-cyclic reverse load test results of shear wall models with large dimensions,one shear wall having an I-shaped cross-section and two with a T-shaped cross-section.We discuss why the aseismatic shear walls of high-rise buildings with large height-to-length ratios have small shear span ratios.We assess the reliability of the shear strength formulary in the Chinese codes for design of shear wall using the international shear wall test results.     

A DYNAMIC ANALYSIS OF UNSYMMETRICAL FRAMEWALL STRUCTURE

The frame-wall structure is good both in operational performance and mechanical property. In this paper, the shear-wall is considered as a cantilever thin-wall member, and the frame as a multistoreyed shear model. The theory of structural matrix is used to get a series of stiffness matrix formulas of theunsymmetrical framewall structure. The Largrange equation is used to get dynamic equation of the structure in the form of matrix. At last a 43 storeyed model of unsymmetrical frame-wall structure is calculated, the result is close to the test.     

河道淤泥气泡混合轻质土剪切流变特性及模型

利用剪切流变试验对以水泥为固化剂的河道淤泥气泡混合轻质土的流变特性进行了试验研究。试验结果表明,经固化处理的河道淤泥气泡混合轻质土在荷载作用下具有类似于硬粘性土的流变特征。剪切流变可以分为3个阶段：在剪应力水平较低时,剪切流变曲线呈衰减稳定型;随着剪应力水平的提高,剪切流变曲线呈非稳定的等速型;当剪应力水平增大到一定程度时,剪切流变曲线呈加速型。河道淤泥气泡混合轻质土的流变性随着混合轻质土强度的提高而降低。根据试验所呈现的剪切流变规律,可以发现河道淤泥气泡混合轻质土的剪切流变符合七元件黏弹塑性剪切流变模型,模型能够比较好地描述河道淤泥混合轻质土在各种剪应力水平下的衰减、等速以及加速流变过程。     

Experiment Study on Soil Properties of Shennv Stream Landslide in Wu Gorge

Accurate obtainting soil parameters of landslide is the key links for landslide stability evaluation and project management . This article takes Shennv Stream landslide in Chongqing Wushan County as an example, implementing unconsolidated and undrained shear test and mineral composition analysis by X ray diffraction for soil in different elevations of landslide ,conducting sensitivity test for various soil parameters of reservoir landslide change with different water level.Study shows that : Mineral composition of soil mainly contains Calcite, Quartz and clay mineral. Hydrophilic minerals in clay mineral have great effect on stability of landslide. Shear strength decreases by influence of water content on cohesion. Cohesion decreases sharply in a quadratic function relation with water content increasing .When water content comes to 18.21% ,change of cohesion tends to be stable.But the internal friction angle of landslide soil decreases linearly in small amplitude with an increase of water content. Research results may provide some important references for rationally choosing strength parameters of soil in similar landslide.     

钢筋混凝土无腹筋细长梁剪切破坏机理模型研究综述

根据现有关于钢筋混凝土无腹筋细长梁剪切破坏机理问题的研究成果,介绍了基于修正压力场理论的抗剪模型、临界剪切裂缝理论、塑性理论、压力路径理论、劈裂破坏理论和基于截面应变分析的抗剪模型的基本假设、核心观点及受剪承载力计算方法,并给出总结、归纳及评析;另一方面,利用相关试验数据和ACI-DAfStb无腹筋细长梁剪切破坏数据库,分别对不同理论模型的受剪承载力计算公式进行了设计参数的影响评估和统计评估;并展望了无腹筋细长梁剪切破坏机理研究的发展方向。研究结果表明：不同理论模型的部分假设缺少直接的试验依据支持,梁腹混凝土的受拉（劈裂）或受剪（骨料咬合）以及受压区混凝土对抵抗剪力的贡献成为抗剪机制的主要分歧;不同受剪承载力计算公式对不同影响因素的考虑方式的合理性和计算结果的准确度均有待进一步提高。后续深入研究应综合考虑剪切破坏问题的随机性和物理属性,利用先进测试技术、应力演化分析方法,进一步揭示剪切破坏机理。     

A New Method of Separating the Shear Waves Splitting in Anisotropic Media

For azimuthal anisotropy seismic exploration, it is very important to separate the fast and slow shear waves splitting in this type of anisotropic media. Many researchers have worked on this problem, but their methods are not realistic in exploration. In this paper, a new method of separating the shear waves splitting in EDA media is presented, that can be directly applied to actual use. Through numerical examples, it can be found that the method is highly efficient and accurate.     

Effects of Vibration History on Modulus and Damping of Clay

Aiming at evaluating the effects of vibration history on dynamic characteristics of normally consolidated clay, a series of multi-cycled cyclic shear tests were conducted on 16 soil samples under consolidation pressure of 50 kPa, 100 kPa, 300 kPa and 500 kPa respectively. The experimental results reveal that, on the stage of drainage and consolidation, with the development of duration shear modulus curve ascends while damping curve descends; this trend became significant as consolidation pressure increased. The variation tends to be stable in 25 hours. When subjected to cyclic loading controlled by constant strain amplitude, both the modulus and damping of soil samples change significantly during the first 50 cycles, and then the differences become moderate afterwards, in which the damping curve acts in hyperbolical type. It is also found that there exists a clear sign of pre-straining that affects damping more significantly than modulus.     

ANALYSIS OF THE BEHAVIOUR OF HIGH STRENGTH BOLTED SHEAR CONNECTIONS

On the basis of experimental tests,a formula is proposedfor the computation of the load-deformation curves of the single highstrength bolted connections in axial shear forces,which is a piecewisefunction describing three stages of friction,slipping and bearing of theconnections,and is also suitable for the non-slip connections.The limitstate method is used to compute the behaviour of high strength boltedconnections subject to eccentric shear,in which each bolt obeys thenon-linear relationship aforementioned.In this paper,the computer pro-gram is worked out to solve the non-linear problems.Analytical resultsare shown to be in general good agreement with experimental data.     

考虑滑移和剪切变形的单箱双室组合箱梁剪力滞效应

为准确分析单箱双室组合箱梁的剪力滞效应,考虑钢混凝土的界面滑移效应和钢腹板的剪切变形,针对顶底板和翼板定义不同的剪力滞翘曲位移函数,基于能量变分法推导出单箱双室组合箱梁剪滞效应的控制微分方程及其闭合解。以单箱双室组合箱梁算例为基础,利用该方法分析其剪力滞效应的规律,结果表明：在同时考虑滑移和剪切变形时,组合箱梁的挠度比初等梁理论解大,且其挠度随界面滑移刚度的增大而减小;组合箱梁在均布荷载作用下,滑移量与荷载值近似成正比关系;在相同条件下,钢箱梁底板的剪力滞效应较混凝土顶板显著。     

Study on mechanical behaviors of interface with cemented soil slurry between gravel and concrete by simple shear tests

The mechanical behaviors of the interface between coarse-grained soil and concrete are investigated by simple shear tests under conditions of cemented soil slurry (clay mixed with cement grout). The results show that the relation curve between shear stress and shear strain appears stress-strain softening and shear dilatation is significant. The point of peak strength and the position when the shear dilatation occurs are related to normal stress. In addition, shear dilatation occurs before the shear stress reaches peak value. In shear failure state, with the same height, the shear displacement increases as the normal stress increases. While with the same normal stress and at the same height, the shear displacement increases as the concrete content increases. A particle flow model of simple shear test between interface between coarse-grained soil and concrete is constructed by PFC (particle flow code). The disturbed height of the sample and the main influence factors are determined by analyzing the laws of particle motion at different heights inside the sample. The PFC results show disturbed height of the sample is related to maximum particle diameter of the soil, normal stress and roughness of the interface (with or without slurry) etc. In terms of the coarse-grained soil, the shear displacement is significant in the area which is close to the interface and about 3-4 times of the maximum particle diameter, and informed the obvious shear band. Further, the thickness of the interface can be regarded as the value.     

剪切盒形状对粮食内摩擦角的影响探究

为了探究在保持其他变量相同的情况下,剪切盒形状对粮食内摩擦角的影响,笔者通过利用自行设计的方圆形剪切盒与圆形剪切盒进行对比直剪实验,测定出不同剪切盒形状下粮食物料的内摩擦角。经过试验结果分析对比,得出方圆形剪切盒所测的粮食内摩擦角较大。剪切盒形状对粮食内摩擦角的测试具有一定的影响。     

Experimental Research on Municipal Solid Waste Landfill''s Strength Character in a Refuse Dump of Chongqing

With the development of economic and society,more and more waste landfill gradually threaten to the development of the city.Some special tests are done to study the relationship of the Municipal solid waste(MSW) strength and the stability of MSW landfill structure.A geo-technical test with the soil samples collected at the scene is done in the laboratory through direct sheared device and the thri-axial sheared device,the disciplinarian and factors are analyzed.The results are referenced to the design and construction of new-built MSW and finished rubbish field.It is shown that some parameters such as composition,particle magnitude,water content,compressing method,intensity and time,will greatly affect the strength character of MSW.     

Experimental Study on Shear Strength of High Strength Concrete Columns

On basis of the experiment on sixteen high strength concrete columns, their shear behaviors are analysed. The effects of shear-span ratio and axial compression ratio on failure behavior, cracking shear and shear strength are analysed. The authors have discussed the suitability of the design equations for shear strength in the code. This experimental study on shear strength of high strength concrete frame columns is the first one in this field at home and the results can be served as reference for the code of high strength concrete design.     

固结煤矸石抗剪强度特征试验

依据现场大型剪切试验和室内直剪试验,研究了固结煤矸石的抗剪强度特性。试验剪应力-剪位移过程曲线表明,一定含水率条件下的固结煤矸石呈现明显的粘塑性体力学特性。以现场大型剪切试验煤矸石作为试样配料进行了室内直剪试验,分析了含水率和密实度对良好固结煤矸石试样剪应力-剪位移试验曲线以及抗剪强度参数的影响,在此基础上探讨了试样内煤及其它细颗粒的状态变化对固结煤矸石抗剪强度的弱化作用机理,最后对比分析了现场大型剪切试验抗剪强度参数值和室内直剪试验抗剪强度参数值的差异及其产生的主要原因。