Method for measuring shear stress-strain relationship of thin adhesive layer

This paper uses the combined bonding disc specimen, with a round end surfaces at both ends of the longitudinal adhesive joint and chamfered steel substrates hither, forms a shear stress distribution of uniform coefficient more than 0.97 and controls the normal tension stress along the bonding surfaces to a very low level. By means of the built-in high accuracy displacement measuring system of uniaxial INSTRON servo equipment, it eliminates the measuring system deformation from the measured total deformation, and then obtains the shear deformation of the joint, and eventually converts into the shear strain of the adhesive joint. The results of experiments using adhesive samples show that the bonding disc specimens are characterized by shear failure of the adhesive joint layers, so it can be thought that the method of combined bonding disc specimens can reveal the right shear properties of adhesives. The measured shear strength can be used as material strength criterion and the measured shear stress-strain relationship can be used in the load capacity analysis of bonded structural members. Because of the simplicity, the combined bonding disc specimen test method is suitable to be adopted in laboratories having displacement-controlled servo systems.     

Design Method of Reinforced Concrete Sandwich Beam column Joints

The experimental results of reinforced concrete sandwich beam column joints were studied intensively and finite element method simulation of such joints were performed for the sake of design method.Basic design criterion and computation contents were provided according to failure mode of specimens and other experimental results.And the limits of parameters were proposed based on the analysis of seismic behavior influence factors and comparison of traditional joints and sandwich joints.Hence, formulas of load resistant capacity were acquired by the results of load resistant capacity of specimens and nonlinear finite element method simulation.It is found that three measures should be taken for sandwich joints in order to reach demanded ductility and load resistant capability.Firstly, several parameters should be limited, including shear compression ratio, axial load ratio, ratio of beam concrete strength to column concrete strength, and minimal amount of transverse reinforcement of joint.Secondly, shear load resistant capacity and axial compressive load resistant capacity should be computed to ensure load resistant capability of joint, and essential strengthen measures could be applied if necessary.Thirdly, appropriate construction details should be taken to avoid reducing of beam bar anchorage capacity.     

冻融环境下钢筋与粉煤灰混凝土的粘结性能

通过对内贴应变片钢筋的直接拔出试验,分析冻融作用下粉煤灰掺量对钢筋与粉煤灰混凝土间粘结性能的影响,得出冻融循环作用对钢筋与粉煤灰混凝土之间粘结性能的影响规律。试验结果表明：钢筋与粉煤灰混凝土的粘结强度随粉煤灰掺量的增加而降低;当粉煤灰掺量一定时,随着冻融循环次数的增加,混凝土强度有所下降,钢筋与粉煤灰混凝土间极限粘结强度降低;当粉煤灰掺量较大,达到40%时,随冻融次数的增加,钢筋粉煤灰混凝土试件极限粘结强度的下降幅度明显减缓,极限粘结强度对应的滑移量增大。表明掺入较多粉煤灰可使试件的冻融损伤现象得到缓解,冻融环境下钢筋混凝土的粘结性能得到提高。     

Phase Transformation Diffusion Bonding of Titanium Alloy to Stainless Steel

Jointing of titanium alloy and stainless steel is very often in the fields like aviation, chemical plants etc. The combination of materials has the advantages of both titanium alloy and stainless steel and will reduce the consumption of titanium resource. The phase transformation diffusion bonding of TA17 titanium alloy to 0CriSNigTi stainless steel are carried out on Gleeble - 1500D. The effcet of maximum thermal cycle temperature, the tensile strength, the fracture surface and microstruture of the joints are investigated. The results show that TiFe and TiFe2 intermetallics and some solid solutions are formed along the interface, when maximum thermal cycle temperature increase, the area proportion of intermetallics in the fracture surface increase, which are detrimental to the mechanical properties of the transition joints.     

Experimental Analysis on Shear Strengthening Capacity of Secondary Dapped end Beams

Because section steel can only be extended to the edge of the support, when a simple support RC beam is reinforced by bonded section steel, a notch comes into being at the end of the beam which is called a secondary dapped end beam, making the stress state of the beam more complex. Through experimental analysis on 21 dapped end beam specimens shear reinforced by steel plate bonded, the deformation process, performing characteristics and failure mechanism of the specimens were investigated. The result shows that two steel bonded forms, including horizontal steel plate and oblique steel plate with angle 45° bonded, delay the appearance of cracks significantly and improve the maximum bearing capacity by 102% and 93%. Due to the impact of stress concentration at the notch, the main modes of damage include concrete tensile or shear failure with the result of bonding failure of a steel plate. By changing the width of steel plates and analyzing different reinforcement effects, formula of bearing capacity of shear reinforcement was proposed based on the method of truss analogue, which provides a reference for engineering application.     

Dry mixed Superfine Sand Mortar for Bonding Ceramic Tile

By modification with water retentive agents and organic bonding admixtures, one dry mixed superfine sand mortar used as ceramic tile bonding was prepared with good workability, adhesive capacity and climate resistance. The test results indicate that this mortar has excellent anti sagging characteristics, with slippage of less than 2mm, sufficient open time and bonding strength over 1 MPa after being open for 20 minutes. These traits provide the needed qualities for thin construction of ceramic tile bonding. By adding polypropylene fiber, a flexible mortar was prepared with superior crack resistance for use as a ceramic tile bonding agent. The preparation mechanism, method and performance are introduced in detail.     

Shear Performance of Steel Plate with Trilateral Constrained

The load carrying test for four steel plate shear walls specimens with various ratio of width thickness are carried out so as to test the failure mode and the shear strength of steel plate with trilateral constrained, and the lateral stiffness and the buckling mode are investigated in the test. The result indicates that the ratio of width thickness of steel plate exerts effects on the shear carrying capacity and failure mode; the buckling of steel plate does not have lateral stiffness. Based on the failure mode of steel plate, the computation model of lateral performance is presented by theoretical analysis. The restraining stiffness of double angle and the buckling restrained stiffness of steel plate are the important design conditions. Formulae to determine the elastic lateral stiffness and the angle type is proposed, which can be used in the preliminary design of steel plate with trilateral constrained.     

页岩烧结保温砌块砌体基本力学性能试验研究

通过对页岩烧结保温砌块砌体轴心抗压、沿通缝抗剪、剪压复合抗剪性能试验研究,分析其破坏特征和破坏机理。试验结果表明:页岩烧结保温砌块砌体受压破坏时,在竖向灰缝附近形成主裂缝,接近极限荷载时砌体出现表皮剥落现象;沿通缝抗剪破坏模式主要为单剪破坏,脆性明显;剪压破坏有剪磨、剪压和斜压3种类型;实测轴心抗压强度平均值高于规范值,沿通缝抗剪强度、复合抗剪强度平均值低于计算值,并分别给出砌体轴心抗压强度平均值、抗剪、剪压复合受力抗剪强度平均值建议公式;剪压复合抗剪强度随着压应力的增大而增大;建立了页岩烧结保温砌块砌体受压应力应变关系表达式;给出该类砌块的弹性模量和泊松比的建议值。     

Numerical Method for Load Bearing Capacity of High Strength Steel Columns at Elevated Temperature

In order to make fire resistance design of high strength steel columns in building structures, the numerical calculation method on load bearing capacity of high strength steel columns at elevated temperature was investigated. By taking the mechanical property of high strength steel at elevated temperature into consideration, extension was made on the inverse calculation segment length method and the program to compute the load bearing capacity of high strength steel columns at elevated temperature was performed. The program was adopted to compute the load bearing capacity. The results obtained by the program and the finite element analysis were compared and good agreement had been found. The influence of magnitude, distribution mode of residual stress and initial geometry imperfection on ultimate load bearing capacity was analyzed by employing the program. It is shown that the extended method can be is shown used to calculate the load bearing capacity of high strength steel columns at elevated temperature; the magnitude and distribution mode of residual stress had little influence but the geometry imperfection have significant influence on ultimate load bearing capacity.     

Design Approach on Flexural Load-carrying Capacity of Steel Beam to CFST Column Joints with External Stiffening Ring

A 3-D finite element model is established by ABAQUS to simulate the behavior of the joints with concrete-filled steel tubular (CFST) column to steel beam using external stiffening ring.The load versus deformation curves of this type of joints are compared between theoretical and experimental results,and in good agreement.Parametric analysis is performed to study the flexural load-carrying capacity of the joint.The width of external stiffening ring,the steel ratio of CFST column,the ultimate strength of steel beam,the strength of steel tube and beam,the concrete strength,the axial load ratio,and the beam to column linear stiffness ratio are considered as parameters.The simplified practical design approach is proposed based on parameter analysis of the flexural load-carrying capacity of these joints.The practical calculated values are in good agreement with the FEM results.     

Experimental Research on the Behavior of Direct Anchoring Beam-wider-than-wall Joint

Based on the elastic finite element analysis of the RC beam-wider-than-wall joint, two large-scale specimens of the direct anchoring beam-wider-than-wall joint are designed to test the joint behavior. The stresses and slips of longitudinal bars in the beam, load-bearing capacity and destruction form are observed and analyzed. The analysis and test results show that: The wide beam should be extended through into the wall for some length to make the flexural stress uniform along beam section width, thus the beam's bearing capacity can be achieved. The anchorage condition of the upper longitudinal bar in the beam outside the wall's width is poor, thus the anchorage length prescribed in the current CODE is not enough to ensure the bearing capacity and ductility of joints. The beam stirrups are very important to the anchorage of the upper longitudinal bar in the beam outside the wall's width. If the quantity of the beam stirrups is not enough, the wide beam in the joint area would have more cracks which decrease the bearing capacity and ductility of joints. Finally, a novel spatial truss mechanism model for the beam-wider-than-wall joint is put forward.     

Seismic Tests and Pushover Analysis of Spatial RC Frame-Shear Wall Structures

Pseudo-static tests of three one-storey spatial RC frame-shear wall structures with floor slabs were conducted to investigate their failure modes and hysteretic behaviors. The test results were compared with those of pushover analysis. It is shown that: 1) damage of the frame beams occurs later and is less than that of the shear wall and the frame columns; 2) damage of the floor slabs under lateral loading is significant in regions close to the shear wall, and tensile stresses of slabs' steel bars in these regions are much larger; 3) in comparison with the case that the floor slabs are neglected, the maximum lateral load that a frame-shear wall structure can bear is larger in the case that the floor slabs are taken into account, and the contribution ratio of the shear wall also increases; 4) shear forces carried by the frame columns with identical cross sections and reinforcement details but located at different positions are close to each other on the whole.     

高温下钢管约束型钢混凝土柱的受力性能

火灾下无防火保护的结构构件温度会迅速上升,从而造成钢材和混凝土的强度明显下降。为了研究火灾下钢管约束型钢混凝土柱的受力性能,考虑火灾下钢管约束型钢混凝土柱的不均匀温度分布及温度对材料力学性能的影响,提出了火灾下受轴心荷载作用的钢管约束型钢混凝土柱承载力的计算方法。利用有限元软件ABAQUS对提出的计算方法进行了验证,结果吻合较好。进而采用该计算方法对影响高温下承载力的参数进行了分析,研究表明：随着构件截面尺寸的增加以及混凝土强度和钢材强度的提高,构件的承载力逐渐增加,而钢管壁厚的改变对承载力并无太大影响。利用有限元软件ABAQUS分析了荷载比、构件尺寸、钢管壁厚等因素对构件耐火极限的影响,发现耐火极限随着荷载比和钢管壁厚的增加而减小,随着构件尺寸的增加而增大。     

Finite Element Analysis of Shear Behavior of Super High Strength Reinforced Concrete Beam

On the basis of testing results of shear behavior from 18 super high strength reinforced concrete restrained beams with web reinforcement, with the cube compressive strength ranging from over 100Mpa, in this paper, the nonlinear finite element analysis procedure was formulated and the analysis of the specimen tests was carried out with the parameters obtained from the experiments and improved constitutive model and failure criteria of materials. Based on the simulated shear resistance test results and practical measured data of eighteen super high strength concrete restrained beams under point load, the equation to compute the shear resistance capacity of such beams was thus obtained by regression. The analytical results agree well with those of experiments.     

FEM Dynamical Analysis of the Reinforced Concrete Beam with Bonding Steel Plate

In order to researchmechanical capability of the reinforced concrete beam with bonding steel plate, adopting separatemethod to establish finite element model of the reinforced concrete beam with bonding steel plate, using FEM to study dynamical characteristics of the model, have got good results which can not be easily got using traditional resolution method, which can give referenceto study dynamical characteristics of the reinforced concrete beam with bonding steel plate.     

钢结构仿古建筑双梁柱中节点的受力机理

为研究钢结构仿古建筑双梁柱中节点的抗震性能,对4个全焊双梁柱中节点进行了水平低周反复加载试验。通过观测试件在侧向力作用下的受力过程和破坏形态,分析双梁柱中节点的受力机理。根据梁截面形式的不同,将其分为箱型截面梁与工字型截面梁2类,依据仿古建筑独特的构造特点,将各试件节点核心区划分为上、中、下3个区域。通过量测各区域内的应变大小,分析该类结构节点核心区在侧向力作用下的受理机理及破坏模式,并建立双梁柱节点的斜压杆受力模型。试验结果表明：仿古建筑双梁柱节点的破坏形式主要为沿下核心区对角线的剪切破坏,并通过理论计算分析提出一种考虑轴压比与梁截面形式的双梁柱中节点抗剪承载力修正公式。     

Impact of Temperature in Air-conditioned Room on Blood Rheological Characteristics

Based on the reversed cyclic loading tests of 21 nearly full-size interior joints in completed reinforced concrete frames,the law of bond deterioration of beam bars crossing the joint is tested and analyzed,which is influenced by the axial load ratio,shear-compression ratio,reinforced bar strength,concrete strength and the relative length of beam bars crossing the joint. By the nonlinear fitting method, the formula of the bond stress r between steel crossing interior joints and concrete under different loading step is obtained. According to the loading approach, the propositional formula of the relative length of beam bars crossing the joint hc/d is presented, which is influenced by axial load ratio, shear-compression ratio ,reinforced bar strength and concrete strength.     

Experimental Analysis of the Behavior of Steel Plate-masonry Composite Wall-beams

When steel plate-masonry composite structure used in the existing masonry structure with load bearing walls is removed for a large space, composite action should be considered between the beam and the supported masonry wall due to the arch effect formed in the supported wall. In order to investigate the working mechanism, failure mode, and load-carrying capacity, strain distribution in critical sections and mid-span defcection of this type of composite wall-beam, five steel plate-masonry wall-beams were tested under concentrated loads and analyzed, which considered variables of height-span-ratio of supported masonry wall, height-span-ratio of composite beam and thickness of steel plate. The results show that steel plate-masonry composite wall-beam starts failure from the masonry located at the line between loading point and supporting point; strain distribution of steel plate along section height meets the plane section assumption; the height-span-ratio of supported wall can directly influence the failure mode of masonry wall, buckling load corresponding to steel plate experiencing local buckling and ultimate load of tested specimens; the reasonable height of supported masonry wall is beneficial to the formation of composite action between supported masonry wall and composite beam, and the excessive high masonry wall will reduce the ultimate load of the tested specimen. Finally, the reasonable range for height-span-ratio of supported masonry wall was presented, and the proposed value representing the flexural stiffness of the steel plate-composite beam relative to the in-plane stiffness of the supported masonry wall was at least more than 79.     

Theoretical Analysis and Experimental Test of Full-scale Bamboo Scrimber Flexural Components

The bending tests and theoretical analysis of five full-scale bamboo scrimber components were conducted and the flexural behavior of bamboo scrimber was researched in detail. Results show that the typical failure modes of bamboo scrimber flexural components are the bamboo fiber fracture at the bottom and interlaminar shear failure near the neutral axis. The sectional stiffness control the design for the bamboo scrimber flexural components, the ratio of PL/250 of the load corresponding to the deflection limit value of L/250 and ultimate load Pmax has good stability. The relationship model of bending tensile strength fm and elastic modulus E was established by regression, which shows that the sectional stiffness expressed by the elastic modulus could predict the bearing capacity well. The plane-section assumption is still valid. The bamboo calculation methods of scrimber flexural components were proposed considering the materials properties of bamboo scrimber based on wood structure design methods. The design value of bamboo bending strength, shear strength parallel to grain and the elastic modulus E were presented preliminarily.     

Analysis on Mechanical Behavior of Welding-Overlap Splices for Mid-Diameter Steel Bars

An improved splice method for mid-diameter steel bars (10-16mm) used in RC structures was developed, which can make the installation more easily and economic through the hybrid connection of welding and overlapping. In order to study the mechanical behavior of welding-overlap splices, a total of 138 steel bar splice tests were conducted, including both the steel-concrete interaction group and the lonely-steel group. Through the splice tensile experiment, the failure model and ultimate strength of the improved splice was summarized. Meanwhile, the failure mechanism was analyzed by the FEM analysis. The test results show that: hybrid connection of welding and overlapping is a simpler splice method which can realized the reliable splice in the RC structures, the ultimate load of the improved splice is sufficient for the application and the failure model is reasonable. Base on the test results, some suggestions for application were given. The economic analysis of a real application case is conducted, which shows a good prospect of proposed connection.