Advanced Materials Research Vols. 243-249

Abstract: Rock and soil aggregate (RSA) is a special geo-material and composed of hard matrix like gravel, cobble, pebble and soft matrix of soil. Discontinuity and heterogeneity are the main characteristics of RSA and its mechanical response is mainly controlled by its complex internal structure. The rock fragments play very important role in the mechanical performances under the condition of uniaxial compression and the rock content (the volume percent of rock fragments in RSA) of RSA is the focus of this study. RSA models with different rock content based on the structural characteristics were built for the numerical uniaxial test. The strength of RSA decreases instead with the increment of rock contents, stress-strain curves attained in the test reflect five different phases according to the deformation and failure process of samples.

Abstract: A structural damage alarming method is proposed using empirical mode decomposition. The basic idea of this method is that with respect to the intact model and damaged models, the energy redistribution of the intrinsic mode functions decomposed from the structural response can represent the variation of the structural dynamic characteristics caused by the structural damage. By taking the Benchmark test model as the research object, the structural dynamic responses from the hammer-impact tests are collected then the damage alarming parameters and the damage alarming indices are evaluated. The experimental results reveal that the structural damage alarming indices based on empirical mode decomposition is able to effectively detect the structural initial damage with preferable damage alarming capacity.

Abstract: A novel building structure system, namely core-tube vibration-reduction suspended structure (CVRSS), is put forward in this paper. The basic composition and calculation model for the structure system are described. The El Centro and Taft seismic waves are used to calculate the dynamic characteristics of the structure in the time domain, of which dynamic responses are proved satisfactory. Taking the top floor displacement of the primary structure and the relative displacement between bottom layer of suspended segments and top floor of core-tube as objective function, the finite element model is established, and comparative analysis with common core-tube suspended structures (CCSS) is performed. The results show that the top floor displacement of CVRSS is about 70% of that of CCSS, and the vibration-reduction performance of CVRSS is excellent.

Abstract: Ningxia Helan Mountain stadium the bottom grandstand of which is steel reinforced concrete frame shear wall structure, the top canopy of which is space steel truss structure system. Using SAP2000 (V9.1.6 version) and MIDAS (V7.1.2 version) software, to have an elasticity check analysis to the overrall structure. Discussion the vibration characteristics and seismic performance of the stadium steel canopy; According to computing and analysising the model, taking normative inspect, the consequence show that the structure can meet the bearing capacity, the stress ratio of the majority position are not more than 0.7, and the stress ratio of force greater position are about 0.95. This wave-shaped canopy structure is excellent, is good to the applicability of architectural form, and can be as a reference for the similar stadium.

Abstract: The force-deformation curve of a reinforced concrete structure in push-over analysis is used to compute the corresponding damage index. A simplified and practical method is established for seismic damage assessment in combination with capacity spectrum method. The two-dimensional capacity spectrum method and the combination of the damage in two directions are discussed. A numerical example using single and double horizontal capacity method and time history analysis demonstrate that the response and damage of structure can be computed accurately in the two-dimensional capacity method. The common trend of structural torsional response can also be reflected. The results show the two-dimensional capacity method is valid and simple.

Abstract: The Artificial Ground Freezing (AGF) Method play an important role in the geotechnical engineering and the back analysis of thermal conductivity of frozen soil is the main inverse heat conduction problem of temperature field. In this paper the physical modelling test of AGF is carried out with double-row-pipe freezing in the lab. According to the measured temperature, the back analysis of thermal conductivity of frozen soil is solved based on the two-dimensional finite element simulation and the least square principle. It is helpful to investigate the freezing process and determine the frozen wall thickness.

Abstract: In this paper, the successive computation formulas of ice response spectrum are derived and deduced based on the assumption of nonlinear interpolation method. And with the new way, the ice response spectrum of two true different ice temporal curves are analysized. The results indicate that the ice spectra value obtained by the new method is a litter greater than the values of the called precision method. And the error of the acceleration response spectra amplification coefficient is only 0.53%. therefore, this ice response spectra method presented by this paper can meet the request of precision. As this method is more preciser than linear interpolation method, it can be used in the design of ice resistance.

Abstract: The structural morphogenesis methods are numerical methods for seeking various‘good structure shape’ based on mathematical and mechanical principles. The methods are to realize the coordination between structural shape and mechanical properties. In this paper, the height adjusting method and Extended-ESO (extended evolutionary structural optimism) method are successfully applied in practical engineering design schemes, which could be a meaningful reference and a powerful tool to the present design in structural shape and mechanical performance.

Abstract: Nonlinear 3D finite element models (FEM) of the two kinds of joints, namely steel bars headed through the pipe joint and steel bars welded with the upper strengthened ring joint, are established by using the ANSYS program. By choosing the suitable element type, boundary condition and loading regime, the author made intensive study on the stress distribution of the steel tubular, the concrete, the strengthened ring and the bar. The result shows that the finite element model accords with the actual stress situation of the joint. Holes on the steel tubular have little effect on the bearing capacity of the axial load of the joint, but the greater impact on the shear transfer.

Abstract: Durability of concrete structure due to carbonation problem has attracted worldwide attention. By studying on the performance of steel fiber reinforced concrete carbonation, simulations CO₂ corrosion environment was simulated. The impacts of the change law of carbonation depth of steel fiber reinforced concrete with water cement ratio (0.35,0.45,0.55), as well as steel fiber content (0%, 0.5%, 1.0%, 1.5% , 2.0%), pouring surface and age, on concrete carbonation depth were studied. Steel fiber reinforced concrete carbonation performance improvement role was analyzed. Thus, providing a experimental basis that can be used in the design and analysis of the durability of steel fiber reinforced concrete structure.