Advanced Materials Research Vols. 243-249

Abstract: For small-scale RC structure model in earthquake simulation test, the material behavior of the model is hard to resemble the prototype well so that the model cannot simulate correctly the nonlinear performance of the prototype. On the basis of the dynamic similitude of mechanical behavior between common concrete and micro-concrete which derive from mechanical behavior tests, the simplified equivalent dynamic similitude relations, which are applicable to the nonlinear performance simulation with small-scale RC structure models in the earthquake simulation tests, have been proposed. By the numerical simulation of earthquake simulation tests and the deviation analysis, the dynamic simulation experimental method has been verified. In addition, for small-scaled RC model, to consider the similitude harmony between concrete and reinforcement used in the model, by adjusting the reinforcement and stirrup, or the effective section height (h0) and hoop spacing etc., simple element testing, shaking table test and numerical simulation were carried out to verify this model design method. Thus, it’s realizable that the small-scaled RC model can simulate correctly the nonlinear performance of the prototype.

Abstract: In high-rise concrete structures, the elevator or stairs which located in the middle of the building are always put into the RC core walls. It not only meets the requirements of the function of usage, but also makes the core walls bear most of the lateral force and becomes the main component in the whole structure that resists the lateral force. Therefore, the seismic performance of RC core walls is of great concern to engineering. At present, there is little experimental study on measures of improving the seismic performance of RC core walls. In this paper, firstly, a new type of construction measure is put forward to improve its seismic performance. Secondly, through the experimental study on one 1/6 scale core walls with concealed bracings and one 1/6 scale normal core walls under the low cyclic loading, the effect of concealed bracings on bearing capacity, stiffness, ductility, hysteresis, failure phenomena and energy dissipation of concealed bracings are discussed. The experiment shows that the seismic performance of RC core walls with concealed bracings is improved remarkably.

Abstract: In order to research the seismic behaviors of the eccentrically braced steel frames, used finite element software SAP2000 to build 20-storey single frame models with type D, K, and Y eccentrically braces, and did the seismic time history analyses to them. Comparisons were set between different kinds of braces in the distributions of moments, displacements, and accelerations for different layers produced by the EICENTRO seismic wave, TianJin seismic wave and NanJing seismic wave. Also, the analyses were set in the time history curves of displacements and accelerations. The results reveal that: type K is able to control the moments and displacements of the layers; while type Y is good at restricting the acceleration amplified effect, and the seismic behavior of type D is between the former two types.

Abstract: The research studied enhanced treatment of sewage from discharging points of rivers by biofilm process dosing with enzyme and the effect of mineral oil on removal rates of the main pollution indexes, and investigated promotion effect of enzyme (including the laboratory developed compounded enzyme and the foreign composite enzyme) on treatment of sewage by biofilm process. The research results indicated that when mineral oil with the concentration of 20mg/L was added to reactor A, B and C, respectively, the removal rates of mineral oil, COD_Cr and ammonia nitrogen all obviously decreased. Meanwhile, the removal rates of mineral oil, COD_Cr and ammonia nitrogen were higher in reactor B and C than in reactor A, and the removal rates of them in reactor B were similar to them in reactor C, which indicated that enzyme had good promotion effect on biofilm process during the sewage treatment process.

Abstract: The research studied enhanced treatment of sewage from discharging points of rivers by biofilm process dosing with enzyme and promotion effect of enzyme on treatment of sewage by biofilm process, and investigated the changes of removal rates of the main pollution indexes at different temperature to ensure the optimal temperature. The research results indicated that temperature was an important factor influencing the removal rates of the main pollution indexes. When temperature was in the range of 5°C-8°C, the promotion effects of enzyme on the removals of COD_Cr and ammonia nitrogen (NH₃-N) of sewage by biofilm process were not obvious. However when temperature were in the ranges of 15°C -18°C and 22°C -25°C, enzyme had the high promotion effects on the removals of the pollution indexes. Furthermore, within the certain temperature (5°C -25°C), the removal rates of COD_Cr and NH₃-N were on the rise with the increase of temperature. When temperature increased from 5°C -8°C to 15°C -18°C, the removal rate of COD_Cr obviously increased, but when temperature continued to increase to 25, the rise trend of the removal rate of COD_Cr became slow. On the other hand, when temperature increased from 5°C -8°C to 22°C -25°C, the increase of the removal rate of NH₃-N was always evident. Therefore, the optimal temperature was in the range of 22°C -25°C for the enhanced treatment of sewage from discharging points of rivers by biofilm process dosing with enzyme.

Abstract: The research studied enhanced treatment of sewage from discharging points of rivers by biofilm process dosing with enzyme and promotion effect of enzyme on treatment of sewage by biofilm process, and investigated the effect of the ratio of CODCr to total nitrogen (C/N) on removals of pollution indexes. The research results indicated that with the decrease of C/N, the removal rates of COD_Cr were stable and the removal rates of NH₃-N increased, but the removal rates of TN obviously decreased in the three reactors. When C/N=5, the average removal rate of TN was higher than 30% in reactor B and C. When C/N=3, it decreased and maintained about 30%. When C/N=2, it was low and approximately 20%. When C/N=5, 3 or 2，the removal rates of COD_Cr, NH₃-N and TN greatly increased in reactor B and C than in reactor A, which indicated that the promotion effects of the composite enzyme and the compounded enzyme on the removals of the target pollutants were favorable.

Abstract: Seismic behaviors of the nine coupling beam specimens that three-layer-closed-restraining stirrups arranged in the coupling beam section depth direction were investigated experimentally. Effects of span-to-depth, amount of stirrups and longitudinal bars of coupling beam on its failure mode are studied, as well as the hysteretic behavior, stiffness degradation, and deformation capacity. Coupling beams with span-to-depth ratio of 0.75－1.5 were observed to suffer shear failure or flexural-shear failure, no matter whether longitudinal reinforcements yield or not. The existing of three-layer-closed-restraining stirrups along the section depth of coupling beam effectively improved its deformation and energy dissipation capacity. According to the experimental results, the formulae for estimating shear strength of the coupling beams were suggested considering the effect of longitudinal reinforcements. Estimated shear strength of coupling beams agreed well with the experimental data.

Abstract: The research studied enhanced treatment of sewage from discharging points of rivers by biofilm process dosing with enzyme and the effect of phenol on removal rates of the main pollution indexes, and investigated promotion effect of enzyme (including the laboratory developed compounded enzyme and the foreign composite enzyme) on treatment of sewage by biofilm process. The research results indicated that when initial concentration of phenol was 5mg/L, the removal rates of phenol, COD_Cr and ammonia nitrogen obviously decreased compared to no phenol added to reactor A, B and C, and the negative effect of phenol was smaller on reactor B and C than on reactor A. Moreover, enzyme had good promotion effect on biofilm process during the sewage treatment process.

Abstract: This paper presents a dynamic reliability-based optimization technique for the seismic design of base-isolated structures. Firstly, the governing equation of multi-degree-of-freedom base-isolated structures is established. Then, the superstructure is unfolded by the first mode. Considering that the damping is non-classical and the total base-isolation system is un-symmetric, the complex modal analysis is adopted to uncouple the governing equation and the analytical solutions of stochastic seismic response under the Kanai-Tajimi spectrum loading are obtained. Taking the ratio between the first-order modal displacement standard deviation of the superstructure with base- isolated system and the fixed-base structure as the optimal objective function, the dynamic reliability of the isolated system displacement as the constraint, the optimal design parameters of the isolated system are obtained through the penalty function method. A 3-story building with isolated system illustrates the proposed dynamic reliability-based optimization method. It is believed that such an optimization technique provides an effective tool for the seismic design of base-isolated structures.

Abstract: This paper presents a dynamic reliability-based optimization technique for the seismic design of structures with tuned mass damper (TMD). Firstly, the governing equation of multi-degree-of-freedom structure with TMD is established. Then, the main structure is unfolded by the first mode. Considering that the damping is non-classical and the total main structure and TMD system is un-symmetric, the complex modal analysis is adopted to uncouple the governing equation and the analytical solutions of stochastic seismic response under the Kanai-Tajimi spectrum loading are obtained. Taking the ratio between the first-order modal displacement standard deviation of the structure with TMD and the one without TMD as the objective function, the dynamic reliability of the TMD system displacement as the constraint, the optimal design parameters of the TMD system are obtained through the penalty function method. A 10-story building with TMD system illustrates the proposed dynamic reliability-based optimization method. It is believed that such an optimization technique provides an effective tool for the seismic design of structures with TMD.