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Material constitutive relationship is one of the basic problems for analysis and application of aluminum alloy structures. This paper systematically studied the material constitutive model of the domestic high-strength new grade aluminum alloy 6082-T6. Tensile testing was conducted for a total of 90 coupons that were cut from three cross-section shapes of the aluminum alloy 6082-T6. The measurement and statistical analysis of mechanical parameters were carried out, including non-proportional extension strengths, tensile strength, elastic modulus, breaking elongation, Poisson's ratio, etc. Various methods for calculating hardening exponent n in the Ramberg-Osgood law were discussed. The fast simulated annealing (FSA) method for calculating n was proposed and the FSA code was written to obtain the confidence interval of n. Comparison of results between FSA and other methods indicates that the FSA can provide more stable results than the traditional two-point method. On this basis, the material constitutive model of the 6082-T6 aluminum alloy was obtained. The comparison of this model and the tested stress-strain curve demonstrates that the constitutive model has good accuracy and can be applied to the engineering applications of aluminum structures. [ABSTRACT FROM AUTHOR]

To investigate the influence of initial curvature of members on the elasto-plastic stability of single-layer reticulated shell structures, the multi-beam method was adopted to model the initial curvature of members, and based on the FEA package ANSYS, two methods were proposed to introduce the initial curvature of members of reticulated shells. According to the randomness of initial curvature of members, the random imperfection mode method was presented. Taking a Kiewitt-8 dome as an example explained the simulation process of the random imperfection mode method, and investigate the influence of direction angle and amplitude random variables of initial curvature of members on the stability of the reticulated shell structure. From the result of the random imperfection mode method, the modified consistent imperfection mode method was established. Then, based on this method, the stability of the Kiewitt-6, Kiewitt-8 and geodesic single-layer reticulated shells considering the influence of initial curvature of members were analyzed. For the structure without and with nodes deviation, the influences of initial curvature of members on the bearing capacity of the structures were obtained quantitatively. The results show that, for the structure without and with nodes deviation, the initial curvature of members can decrease the bearing capacity of the structure obviously, and change the degree of plasticity development of the structure. The influence of initial curvature of members on the elasto-plastic stability of single-layer reticulated shells cannot be neglected, and the modified consistent imperfection mode method is effective to estimate the lower bearing capacity of the reticulated shell structures considering the influence of initial curvature of members. [ABSTRACT FROM AUTHOR]

Selection of an appropriate ground motion intensity measure to be used in scaling or standardizing the ground motion records is of importance as it can be used to reduce the scatter of the obtained peak responses for different ground motion records. To identify such an adequate ground motion intensity measure for Kiewitt-8 single-layer reticulated domes, it was noted that the ground motion intensity measure could be grouped as absolute intensity and relative intensity, by considering whether the dynamic characteristics of structures were taken into account. Based on the statistics of peak displacements obtained from the time history analyses that were carried out for Kiewitt-8 single-layer reticulated dome under horizontal or vertical ground motion components of selected records, the correlation coefficients between the peak displacements of the structure and a group of selected ground motion intensity measures, including the spectral acceleration response at the fundamental vibration period, Sa(T1) , were evaluated. The results show that Sa(T1) is an adequate ground motion intensity measure for the horizontal excitations for the considered dome. However, its use for vertical response is questionable as expected. Furthermore, the vibration period mode that controls the peak vertical displacements is usually unknown. A simple practical approach to remediate this drawback is suggested. It requires the use of harmonic analysis for horizontal and vertical excitations to identify the vibration periods at which the structure reaches its peak responses. The spectral acceleration values at the identified periods can then be used as ground motion intensity measure. [ABSTRACT FROM AUTHOR]

Based on the mechanical behavior of the Tensairity, a spindle Tensairity structure model of 2.5m span was designed and manufactured. Under two concentrated forces loading on the mid-span of the model, the deflection and the laws of internal force distribution of the model were investigated, and the influence of the internal air pressure on the static performance of the structure was studied. Through the analysis of the limit states for the structure, the fracture morphology and the failure mechanism were studied. Second, the refined spindle Tensairity finite element model was established by ANSYS. From initial state to inflated state and loaded state of the structure, the whole course numerical simulation was carried out, and the responses of the structure were compared with the results of the experiment. The results show that the results from numerical simulation and the experiment agree well. The displacements and the internal forces obtained from the two methods coincide basically. The test model reaches the limit state at the time of the concentrated force is added to 1.98 kN, and the corresponding failure mode is the local buckling damage of the upper chord member and the folding of the membrane at the end of the airbag. [ABSTRACT FROM AUTHOR]

For accurately simulated temperature field of concrete raft foundation of the Taishan Nuclear Power Plant, finite element analysis (FEA) was used to consider effects of age, temperature and construction process. Based on concepts of equivalent age and hydration degree of concrete, equivalent age-hydration degree curve (EAHDC ) was obtained based on adiabatic temperature curve. With subroutine HETVAL of the software ABAQUS to specify hydration exothermic rate according to equivalent age-hydration degree curve, the effects of age and temperature on the hydration exothermic process of cement were considered. According to construction process and geometry of the raft foundation, half model of the raft foundation was adopted, and the model change interaction function (MCIF) of ABAQUS was used to simulate the construction process. Analysis results show; effects of temperature and age on the hydration exothermic process of cement can be simulated by using EAHDC; characteristics of temperature field, such as symmetric distribution and effect by construction process, can be captured by using half model of the raft foundation and MCIF of ABAQUS; simulated values, such as time of initial temperature rise, maximum temperature and its corresponding time, agree well with tested values by considering construction process. [ABSTRACT FROM AUTHOR]

To control concrete quality of outer containment of the Taishan Nuclear Power Plant, thermal field out of concrete hydration was simulated, and appropriate curing measures were proposed. Based on hydration degree concept and equivalent age concept, equivalent age-hydration degree curve (EAHDC) of C55 concrete, used in outer containment, was developed. To consider effects of age and temperature on heat releasing process of hydration, EAHDC was employed in simulation of thermal field using subroutine HETVAL provided by ABAQUS software. Effects of height and thickness of the construction layer, shape and size of the hole, the efficiency of insulation and the curing period on temperature field were separately studied. Comparisons and analysis show; EAHDC can be used in thermal field simulation to take effects of age and temperature on heat releasing process of hydration into account; effect from height of construction layer is negligible while the height is in the range of 2.35-3. 60 m; the increment of thickness results in higher peak temperature, and insulation layer with a convection transfer rate of 1.8-5.4 W/(m² x °C) and curing period of 10 days with formwork are recommended. [ABSTRACT FROM AUTHOR]

Seismic ground motions are spatially varying when reaching the site of structures after long distance transmission. It is more realistic to consider the coherency effects by multi-support excitations than uniform excitations. The supporting structure of the five-hundred-meter aperture spherical telescope (FAST) is a new kind of cable net structure, thus it is necessary to investigate the seismic responses considering the spatial variations under multi-support excitations. Based on available excellent model of seismic ground motion, was used to simulate the seismic ground motions of 338 points within the area covered by FAST. The seismic ground motions at the 2 395 beamings of FAST were obtained via linear interpolation between the 338 points. The time-history responses of supporting structure of FAST under multiple-support excitations and uniform excitations were analyzed with ANSYS. The results show that the seismic coherency effects poses different influence on the supporting structure of FAST in three component directions. It is thus necessary to consider the seismic coherency of all three component directions in the analysis. Affected by the seismic coherency effect under three-dimensional seismic excitations, the stress in 94.08% of the main cables is increased by an average of 87.04%, the stress in 43.51% of the tie-down cables is increased by an average of 21.88%. Under three-dimensional multiple-support seismic excitations and three-dimensional uniform excitations, the maximum tensile stresses of the cable are 835.43 MPa and 671. 10 MPa, respectively, and both are smaller than the characteristic tensile strength of the cables of FAST. The supporting structure of FAST can withstand the expected seismic ground motions. [ABSTRACT FROM AUTHOR]

A kind of bolted height adjustable steel beam-to-column connection was developed based on traditional connections, which is applicable when the beam height changes only in a small range. The influence of L-shaped connector stiffening methods and beam-to-column connection centering schemes on the failure modes, hysteretic properties and L-shaped connector slippages of the connections were studied on the basis of the experimental and numerical results of four full-scale assemblies under low cycle reversed loading. The results show that; the stiffness of L-shaped connectors can change the mechanical behavior of the connections, and the presence of ellipse-shaped bolt holes on L-shaped connectors leaded to the slippage of the connections, which had negligible effect on hysteretic behaviors; the design desirable failure mode and better hysteretic properties of the connections can be achieved by improving the stiffness of L-shaped connectors; no significant effect of the beam-to-column connection centering patterns was detected; the modeling method illustrated in this paper can simulate the cyclic behavior of the connections properly. This kind of newly developed connections can be applied to the fabricated light-weight moment frames. [ABSTRACT FROM AUTHOR]