Key Engineering Materials Vols. 340-341

Abstract: This paper focuses on an experimental investigation and theoretical analysis of different types of RC shear wall with the profile steel braces in two side columns and diagonal profile steel braces of walls subjected to applied repeated cyclic loads. Fifteen RC shear walls with different shear span ratio are tested and their aseismic charactertics are studied. The effect of profile steel bracings on failure property, bearing capacity, ductility and hysteretical characteristic of shear wall is investigated based on experimental results. It is shown that adding the profile steel braces on the boundary column and inner of walls can obviously enhance the ultimate strength of specimens and improve their aseismic characteristics. Finally, the mechanical model of the shear wall is presented and the formulae for calculating the load-carrying capacity are developed. Numerical analyses indicate that the theoretical results agree well with those from experiments.

Abstract: The horizontal press performance of column is deteriorated because of special-shaped section. Moreover, because the antiseismic performance of columns is worse, it is only used in regions where seismic intensity is lower. So the main problem is to enhance the ductility. This test study on mechanical performance has been carried out through fourteen SRCTSSC and RCTSSC. The study focuses on the impact of test axial pressure ratio(nt), hooped reinforcement ratio(ρv), shear span ratio(λ) and steel ratio(ρss) to the shear strength and the antiseismic performance of SRCTSSC. It can be concluded that the shear strength of SRCTSSC is increasing with the increasing of nt and ρss , but the degree of increasing is small when nt is a certainty value, and that the shear strength of SRCTSSC is decreasing with increasing of λ; The shear resistance formula of T-shaped column is derived through tests, the calculated results are in correspondence with those of the tests. It also can be concluded that the hysteretic loops of the SRCTSSC are full and the hysteretic behaviors are improved and that the displacement ductility is increasing with increasing of ρv and ρss , but decreasing with the increasing of nt and the degree of variety in high axial pressure ratio is larger than in low axial pressure ratio. If steel bars are added, the shear strength and displacement ductility of SRCTSSC is increased in a large degree, and the capacity of energy dissipation is also enhanced. This test, for applying the special-shape column to higher intensity region, has the certain instructive significance.

Abstract: In this paper, a coupling constitutive model is proposed for anisotropic damage and permeability variation in brittle rocks before cracks fully coalesce. In this coupling model, an anisotropic damage model is employed to perform the mechanical analysis, and a statistical penetration model is set up to describe the effective porosity and permeability evolution in brittle rocks. For the coupling analysis, anisotropic damage model offers statistical penetration model the crack length in various directions, and statistical penetration model inversely provides anisotropic damage model with permeability of rock for coupling hydro-mechanical analysis. The proposed coupling model is applied to Lac du Bonnet granite, and generally a good agreement is obtained between numerical simulations and experimental data.

Abstract: It has been assumed that the use of lightweight aggregate concrete structures can largely reduce dead loads and thus reduces the earthquake effects without increasing the total cost. However, one of the primary concerns for these structures has been the plastic deformation capacity, ductility, and energy dissipation capacity. Tests were conducted for seismic performance of reinforced lightweight aggregate concrete (RLAC) frames that consisted of beams and columns of different cross-sections. Quasi-static reversed cyclic loads were performed on 1:2 scale RLAC model frames that had special cross-sections. It was demonstrated that the RLAC frames had inherent defects regarding seismic performance. This, however, did not have substantial influence on the integral seismic performance of the structures. It was concluded that the RLAC frames met normal service requirement with sufficient strength reservation. The RLAC frames may represent a viable alternative for ordinary reinforced concrete framed structures in low- to medium-rise buildings in frequent-occurring earthquake areas.

Abstract: A series of numerical experiments are conducted by the Elasto-Plastic CA model, which was successfully used to simulate the rock failure process under uniaxial compression in previous work by the authors, to obtain the failure processes of heterogeneous rocks as well as the stress-strain relation and strain-AE relation under tensile loading at meso level. The model can consider the heterogeneity of the materials conveniently, and has the advantages of localization, parallelization etc. By constructing some local simple rules, the model can perfectly simulate the self-organization process of rock failure process. In this paper, the domain is discretized into the system composed of cell elements which are assumed to conform to the constitutive laws of elasto-brittle-plasticity. The Weibull’s stochastic distribution is introduced to represent the heterogeneity of rock materials, and Mohr-Columb criterion with tension cut-off is considered as the yield criterion. The process of crack initiation, propagation and coalescence is well simulated and the results obtained reproduce the main features known of rock behavior, both at meso and overall stress-strain levels.

Abstract: The mechanical properties of rock under high temperature and high geostress are the basic and important information to assess the safety of underground engineering. Based on the environmental conditions of the west route of south-to-north water transfer project in western China, experiments are conducted for a sandstone. The experiments are conducted in stress path of hydrostate, pure shear, and conventional triaxial compression at the temperature of 25°C, 50°C and 70°C. The change of strength and average moduli of the rock with temperatures are studied. By cycle loading and unloading tests, elastic and plastic deformation of the rock are decomposed, it is shown that the plastic deformations of the rock are clearly changed with temperature, while the elastic deformation of the rock seems to be unaffected by the temperature. Moreover, based on the associated plastic flow rule, a constitutive law considering temperature is proposed for the sandstone.

Abstract: In this paper, a new concept, YAI (yielding approach index), is firstly proposed to estimate the safety differences of rock and rockmass whose stress states are close to yielding. Secondly, in order to describe the intrinsic heterogeneity of strength of the same rock, the safety parameter ω, which is the phase complementary parameter of YAI, is supposed to be a stochastic variable in this paper and conform to the Weibull’s distribution. By analyzing the triaxial test data of five types of rocks, it can be found that ω as a stochastic variable evidently conforms to the Weibull’s distribution. Results in this paper give an important and useful reference to the safety analysis for geotechnical engineering.

Abstract: This study is mainly in temperature-control and anti-cracking of plant concrete in hydroelectric station. By means of FEM of three-dimension thermal creep stress and imitating construction progress, an emulator calculation is performed from construction period to operation period and distribution regularity of thermal creep stress is brought to light in the theory. The text described the developing process of concrete’s temperature and thermal stress, and then combined concrete’s time-varied thermotics and mechanics performance to analyze the possibility of yielding crack in different period and position.

Abstract: In this paper, the experimental study on the mechanical property of limestone under triaxial compression with different hydrochemical environments is conducted and the non-linear characteristics of complete stress-strain process of limestone subjected to chemical corrosion, are analyzed. The behaviors of deformation and strength of limestone eroded by different chemical solutions are obtained. It is known from the experimental and analytical results that different chemical environments such as chemical composition, pH value etc can affect the mechanical property of rock differently. How to establish a multifactor characteristic constitutive model which can reflect different chemical environments is the key problem to study the coupling corrosion effect of stress and chemistry of rock. The constitutive model of evolutionary neural network for rock under chemical corrosive environments is put forward, and the neural network constitutive relationship under stress-chemistry coupling corrosion is established by applying the theory of evolutionary computation and neural network. The neural network constitutive model established in this presented paper mainly takes into account the following three aspects: chemical environments of rock specimens, content of main mineral compositions that are liable to being eroded by chemical solution, and mechanical environments. The results are in good agreement with the experimental data.