Abstract:Experimental studies of 29 pin-ended beam-columns, including 13 box-type and 16 L-type sections, extruded from 6082-T6 aluminum alloy, were performed in this paper to investigate the stability behavior and bearing capacity for high strength aluminum alloy. The buckling behavior, stability bearing capacity and deformation performance of all the specimens were obtained. A finite element (FE) model of aluminum alloy beam-column was conducted by analysis software ABAQUS and verified by experimental results of 29 beam-columns. Initial geometric imperfection which influenced simulation results was analyzed. A parametric study of beam-columns with different cross section dimension, regularized slenderness ratio, eccentric direction and eccentricity ratio, was performed using the FE model. Finally, Chinese code and Eurocode9 were verified and compared by the experimental data and the results of the parametric study. Meanwhile the design approach based on Chinese code for L-type cross section beam-columns was proposed. It can be concluded that the FE model proposed in this paper can well predict the stability bearing capacity and the deformation characteristic for aluminum alloy beam-columns; Chinese code and Eurocode9 can be applied to doubly symmetric box-type cross section and mono-symmetrical L-type cross section beam-columns, but they were both too conservative.

Abstract:To obtain the seismic performance of single-layer reticulated domes with friction pendulum bearings (FPB), finite element refined models of FPB were applied to 80 m K8 single-layer reticulated domes FE Model. The same earthquake waves were exerted to single-layer reticulated shells with hinge support or FPB. The isolation effect of FPBs was analyzed in two main aspects including the dynamic responses of bars and nodes of reticulated domes, and the impact of FPB parameters on the seismic response of single layer latticed shell were discussed. The results indicate that the optimal friction coefficient of FPB increases with the increase of the ground motion intensity. The bigger curvature radius of FPB, the smaller seismic responses of reticulated shell structure will be. On the basis of the above research, this paper gave some discussion how friction pendulum bearings were selected for single-layer reticulated domes.

Abstract:two-span continuous beams which are used HRB335, HRB400, HRB500 and HRB600 reinforcements are analyzed to investigate the bending moment amplitude modulation rule of concrete continuous beam with high-strength hot-rolled bar. The moment redistribution is investigated in two phases: One is the modulation amplitude β_b caused from loading to steel yielding in control section of support.The other is β_a caused from formation of a plastic hinge to the crushing of compressive extreme concrete fiber in control section of support.The results indicate that the plastic hinge appears delay and the rotation capacity of plastic hinge decreases, at the same time, the interval from the tensile extreme concrete fiber into the plastic to longitudinal reinforcement yielding ranges longer. The moment amplitude modulation coefficient equation using θ_p/h₀ as the key parameters with a certain intercept β_b has been obtained.Practical expression with ξ as independent variable has been proposed to facilitate the engineering applications.

Abstract:specimens of post-build concrete wing wall located two neighboring faces of corner columns were designed and conducted to study the seismic performance of the post-build concrete wing wall reinforce frame corner column. Three test axial compression ratio including 0.1,0.6,0.40 was designated for exiting frame corner columns. HRB400 was used as longitudinal steel bar. The ratio of longitudinal reinforcement was 1.23%, 1.05%, 0.82% and stirrup with HPB300 ratio 0.6%. The results of six specimens under cyclic reversing load show that damage degree of the parallel wing wall away from the corner column was significant, while the corner column and the perpendicular wing wall were damaged lighter. Existing column could resist vertical loads and horizontal seismic actions. The wing walls could bear horizontal seismic action and as an effective dissipation energy component.

Abstract:Graphene suspension was prepared by nitric acid oxidation and ultrasonic to improve the hydrophobicity. Graphene suspension was added to cement to produce cement-graphene composite. The effect of graphene on mechanical properties and microstructure of cement paste was studied. In addition, the toughing mechanism of grapheme was also discussed, which provide theoretical and practical foundation for the study of graphene cement-based composite materials. With the increase of graphene content, the compressive and flexural strength of cement-based composite increased firstly then decreased, and the optimal additive amount is 0.02 wt%. The results from structural analysis of set cement by SEM and FT-IR indicated that graphene can promote the growth of the hydration products, change the shape and size of hydration crystal, but did not change its type through reacting with cement and graphene.

Abstract:The eccentric compression performance of concrete filled circular steel tubular (CFCST) columns using high-strength recycled aggregate concrete (RAC) instead of normal concrete (NC) was studied through repeat load tests on four specimens in this paper. Four specimens were divided into two groups; the first set of two specimens included a CFCST column filled with RAC and a normal CFCST column, the eccentricity was 100 mm. The second group had the same specimens and the difference was that the eccentricity was 160 mm. Load-deformation and stress-strain curves as well as the strain distribution over the cross section were obtained through the experiment. The failure characteristic, load-bearing capacity, stiffness, ductility, energy dissipation and residual deformation of the specimens were analyzed. The obtained results are compared with the ultimate strengths of CFCST columns predicted by existing design codes. The test results indicate that damage development and failure mode of CFCST columns with RAC are similar to those of normal CFCST columns. The replacement of NC with RAC has beneficial effects on the load-carrying capacity and deformation properties. The strain distribution was found to accord well with the plane section assumption. With the incensement of eccentricity, the load-carrying capacity decreased, the stiffness degradation intensified, and the deformation ability improved.

Abstract:Capacity Matrix, Transfer Matrix and Chloride Passing Rate Vector are associated with variables in transient heat balance equation, and a numerical simulation method by ANSYS thermal analysis module for chloride transport in nonsaturated concrete is proposed to investigate the chloride transport model in nonsaturated concrete. The numerical results are validated by experimental data. A R.C beam is corroded with chloride from three different directions, respectively. The results indicate that the chloride concentration by numerical simulation is very close to the experimental results. Numerical simulation provide another way for modeling chloride transport of nonsaturated concrete. For corrosion of R.C beam from single direction, the decay of chloride concentration is the quickest. The decay speed for corrosion from three directions is the slowest, and corrosion from two directions is in the middle. Corrosion from multiple directions leads to that the chloride concentration on the surface of rebar and stirrup is higher than single direction. Corrosion from multiple adjacent sections cause more easily rebars corrosion. The closer section will induce corrosion more seriously. Chloride transport to the right from the left of beam section within ten years, and the results of corrosion from two directions is a slightly more than that from three directions. Therefore, chloride penetration from multiple directions will induce more serious corrosion to the rebar in a long time.

Abstract:Convex model was used to consider the uncertainty of earthquake in this paper to solve the problem that the selection of different ground motion records will result in great variability in structural seismic performance analysis. Taking the inter-story displacement angle as seismic performance index, non-probabilistic seismic performance of a reinforced concrete frame was assessed under the motivation of rare earthquake by the capability spectrum analysis method. Then the results were compared with probabilistic seismic performance based on the probabilistic random model. By comparison and analysis, it shows that the evaluation of structural seismic performance based on convex model not only reduces the variability, but also is reasonable and applicable to some extent.

Abstract:The train loading is simplified as equivalent rectangular cyclic loading in this paper to investigate the influence of train loading on long-term deformation of soft soil around a shield tunnel. Based on the empirical relation between permeability and compressibility, the governing equation of nonlinear consolidation is established. Then the analytical solutions are derived after the partially sealing lining as boundary condition is considered by introducing a dimensionless relative parameter of soil-lining permeability. The rationality of corresponding analytical solutions is confirmed by the comparison among predictions of ground settlement by presented solution and field data from Shanghai Metro Line No.1. The results show that the increment of ground settlement by train loading is positively correlated with partially sealing condition. The presented solutions provide a reasonable and effective tool for the prediction of long-term ground settlement by the operation of metro way.

Abstract:The accelerated carbonation tests and repeated loading tests on C20 and C30 concrete specimens were carried out to investigate the effect of carbonation on the mechanical properties of concrete under repeated loading. Test results show that with the increase of carbonation depth, the brittle failure of concrete became more significant, the elastic modulus and the compressive strength increased, the strain at peak compressive stress decreased, respectively. The common point curve deviated farther from the envelop curve, the shape of the descending branch of envelop curve became much steeper, the concave shape of the unload curve became more and more obviously, the shape of reload curve became more and more gentle, the hysteresis of strain recovery for carbonated concrete became more obviously. Based on regression analysis of test result, the analytical stress-strain response of carbonated concrete subjected to repeated loading were established.

Abstract:The accelerated corrosion tests of six squat shear walls with span ratio of 1.0 were conducted by artificial climate laboratory to understand the seismic performance of squat RC shear walls under offshore atmospheric environment. Their quasi-static experiments were implemented. The hysteresis loops regarding the relation between horizontal load and displacement of specimens with different axial compression ratio and various degrees of corrosion crack width were obtained. The skeleton curves of specimens were further achieved. Based on the test results, some performance aspects, such as the ultimate capacity, rigidity, ductility and energy dissipation capacity, were analyzed. The result shows that with the increase of axial compression ratio the bearing capacity and stiffness of corrosion specimens continued to improve, while their ductility and the deformation recovery capability are reduced. These manifest that the axial compression ratio must be strictly controlled during seismic design under offshore atmospheric environment. In addition, the crack load and the ultimate load, rigidity, ductility, energy dissipation capacity decrease with the increase of corrosion crack width of specimens. Moreover, when the specimen subjected to serious corrosion, the brittle failure is more obvious without any warning. Above findings demonstrate that with concrete ages growing over time, the internal rebar under this condition suffers increasingly severe corrosion and behaves worse in seismic performance.

Abstract:In cold region, it is of great significance to select suitable steel material in order to prevent the failure or collapse of transmission line tower, which results from the brittle fracture of construction member at low temperatures. A series of uniaxial tensile tests and Charpy impact tests were performed to investigate the mechanical properties and impact toughness of materials of steel tube(Q345B, Q420B, Q460C) and angle iron(Q345B, Q420B). The plastic indices of steel tube and angle iron materials were evaluated through comparison and analysis. The Boltzmann function was employed to conduct curve fitting for impact energy versus temperature, obtaining the ductile-brittle transition temperatures. Results indicate that the yield strength and ultimate tensile strength increase with the decrease of temperature, and all the plastic indices can meet the prescribed requirement. Charpy impact energy increases as the temperature reduces. Besides, the ductile-brittle transition temperatures of Q345B steel tube and Q345B angle iron are relatively high, indicating the poor resistance ability of cold brittleness failure. Based on the results of tensile tests and impact tests, it is suggested that priority should be given to the adoption of Q420B steel tube, and Q345B angle iron is inadvisable.

Abstract:This paper developed finite volume method program with Smagorinsky sub-grid scale model using 3-dimensional unstructured mesh to accurately determine the flow field characteristics behind a cylinder in sub critical region and the applicability of 3-dimensional large eddy simulation method of this kind of calculation based on C++ programming language. Numerical simulation was performed for the flow over a circular cylinder at a classical sub-critical Reynolds number (Re=3 900) using a new second order defer correction scheme for unstructured mesh. The results show that mean and fluctuating flow characteristics were compared well with the existing experimental results, 2-order discretization scheme large eddy method can be used in the simulation of sub-region Reynolds number outer flow simulation. The results also proved the reliability of high accuracy and stability discretization scheme.

Abstract:The equation for the shear capacity of UHPFRC beams with stirrups is deduced to study the shear capacity of UHPFRC beams with stirrups, based on the modified compression field theory, and considering the shear contribution of concrete in compression, shear stress transmitted across crack interface, shear carried by steel fibers and stirrups. The analysis results of nine tested UHPFRC beams in shear by the proposed equation agree well with the test values, and the variation coefficient is small. It is suitable for shear analysis and design for UHPFRC beams with stirrups.

Abstract:The repeated load tests of five recycled coarse aggregate concrete composite beams and two normal concrete composite beams were carried out to investigate the flexural behavior of recycled coarse aggregate concrete composite beams with closed-section steel deck. Based on the tests, the flexural behavior of recycled coarse aggregate concrete composite beams with different shear studs’ layout, slab thickness and steel shape was analyzed and compared with that of normal concrete composite beams. The analysis working was mainly focused on yield load, ultimate load, deformation, the slippage between the steel shape and composite slab and damage process of the composite beams during the test. The test results show that the failure modes of recycled coarse aggregate concrete composite beams and normal concrete composite beams are similar. Based on the experimental results, the calculating formulas of the bearing capacity and the deformation of recycled coarse aggregate concrete composite beams with closed-section steel deck were presented with reference to the normal concrete composite structure design code. The calculating results are in good agreement with that of the experimental results, so the calculating formulas can be used for designing recycled coarse aggregate concrete composite beams.

Abstract:Fire tests on four restrained columns fabricated with Q460 steel were carried out using furnace to obtain the fire resistance of high strength Q460 steel columns. The temperature of the furnace follows ISO-834 standard curve with the applied load keeping constant. Two restraint-stiffness ratios and two load ratios were considered, and the temperature distribution, axial displacement and deflection at the mid-section of steel columns were recorded in the tests. The buckling and failure temperatures of restrained Q460 steel columns were obtained. The failure temperature of specimens were calculated by employing the method of amplification factor of axial force in axially restrained steel columns and the results were compared with test results. The study shows that both the axial restraint and load ratio have great influence on fire resistance of Q460 steel columns. For certain load ratio, the failure temperature is lower for the steel column with the higher axial restraint, and for certain restraint stiffness, the failure temperature is lower with the higher load ratio. The method of amplification factor of axial force in axially restrained steel columns can be used to predict the critical temperature of restrained high strength Q460 steel columns.

Abstract:Mechanical parameters were obtained by mechanical test to obtain the mechanical properties of overlying strata in coal seam. Test results show that natural density, tensile strength, uniaxial compressive strength and the elastic modulus of the samples increase with the raise of the occurrence depth while water absorption rate and Poisson's ratio decrease with the increase of the occurrence depth, and the mechanical properties of the specimen are directly related to the lithology. Discreteness of test data increases with the increase of the occurrence depth. In addition to tectonic stress, coal mining and temperature effects, the main reason for discreteness is that the internal particles of the sandstone and other sedimentary rocks recouple with the stress relief.

Abstract:A survey of adjacent buildings pounding damage caused by the Lushan earthquake is presented in this paper. Used the acceleration records from Lushan earthquake, the seismic response of adjacent buildings considering collision is calculated, and the influence of seismic joint width and building mass to the collision process is analyzed. Conclusions are as follows: the wider the seismic joint between adjacent buildings, the less and slighter the pounding; there is little effect of ground motion direction on the collision damage between adjacent buildings; the influence of pounding to the building seismic response become slight with the increase of building mass, and the influence is larger to the lighter building; analysis results about adjacent buildings collision in this paper are in conformity with the typical pounding damage example.

Abstract:The novel grouting coupler was developed using seamless steel pipe through cold rolling press to reduce the cost of rebars splicing used in precast connection. Based on incremental tension test, the confinement mechanism and distribution of confining stress in the sleeve were studied. It is shown that the ultimate strength of this new splice can meet the regulation specified in JGJ107—2010. The initial confining stresses caused during the hardening process of the infilled grout are related to the mechanical properties of the spliced bars, grout and sleeve and dimensions of the splice. When these parameters are determined, the confining stress increased linearly with the increment of free expansion rate of the grout. The average confining stress in the deformed part is greater than it in the smooth part. For the deformed part, the confinement is mainly provided by the radial component of the interaction between the concentric ribs and the infilled grout. On the other hand, the confining stress in the smooth part is controlled by the dilation of the inner grout.

Abstract:The closure buckle steels was applied to improve the traditional steel grouted connecting precast wall to improve the mechanical properties of the steel grouted connecting precast wall. By the low cyclic loading experimental test of the improved steel grouted precast wall connector, that the closure buckle steels can efficiently improve the mechanical properties of the steel grouted connecting precast wall, was proved. After that, in order to determine the capacity calculation method for the improved steel grouted precast wall connector, this paper analyzed the typical shear failure mechanism of steel grouted connecting precast wall, especially the interface failure, and proposed the simplified capacity calculation model for the improved steel grouted precast wall connector. Afterward, by combining with the capacity calculation formulas of the cast-in-place shear wall provided by the current design code, the capacity calculation method for the improved steel grouted precast wall connector was determined. Finally, the joint capacity of the connector was calculated using the proposed calculation formulas and the section integral method. By comparing the calculated capacity using the method proposed above to the section stress integral calculation results and the experimental test results; it can be illustrated that the proposed simplified capacity calculation model and the calculation method for the improved steel grouted precast wall connector can be reasonable.

Abstract:The time-dependent behavior of a typical three-span prestressed concrete (PC) continuous box girder bridge was analyzed to investigate the effect of non-uniform shrinkage and creep due to thickness differences among webs and top and bottom flanges in box girders. Considering time-varying effects of compressive strength and elasticity modulus of concrete, finite element models which simulated cantilever-construction by solid and beam elements were developed, respectively. A comparative study on structural displacement, concrete stress and tendon stress caused by uniform and non-uniform creep and shrinkage after bridge completion was peformed. Meanwhile, long-term deflection and tendon stress were compared with relevant values which were calculated according to the standard. And the time when tensile stress and crack resulting from vehicle load and non-uniform creep and shrinkage in the bottom flange appeared was estimated. The results show that compared with uniform creep and shrinkage, non-uniform creep and shrinkage have smaller influence on the long-term deflection at midspan, and have greater effect on the concrete stress, which should be concerned in design of box girders.

Abstract:An optimization solution of Rayleigh damping coefficients is proposed to construct the damping matrix of structures with closely-spaced natural frequencies based on the seismic response spectrum theory and the complete quadratic combination (CQC) rule. A constrained optimization method is further developed to enforce the arbitrary order mode damping ratio equal to the precise value by Lagrange multiplier method. A curved girder skew through steel suspension arch bridge is analyzed to investigate the characteristics of the proposed method. Firstly, the solution stability of optimal Rayleigh damping coefficients is discussed, Secondly. the effects of the different combinations of optimal objective functions and constraint conditions on optimal reference frequencies and seismic response are compared, and the selection of constraints mode in constrained condition is also discussed. Numerical results show that the seismic response calculation error is smaller while the Rayleigh damping coefficients is obtained from CQC rather than the square root of sum square (SRSS) combination. The constrained mode should be specified as the first order significant mode corresponding to structural seismic responses.