Jian Cai

Finite Element Analysis on Concrete Filled Steel Tubular Concrete Beam Joints under Cyclic Loading by OPENSEES

Concrete filled steel tubular (CFST) column-beam joint with the column tube discontinuous in joint zone is a new type of joint. Firstly, the results of the cyclic loading experiments on this joint were introduced briefly. Then numerical simulation of the experiment process was carried out by OPENSEES, and the load-displacement curves, strength degradation, stiffness degradation of the specimens were studied. The analysis results exhibit good agreement with the experimental ones. OPENSEES can simulate two types of failure, including joint failure and beam failure. Based on specimen S3, parametric analysis were conducted to research the strength degradation and stiffness degradation in models with different reinforcement ratios and reinforcement diameters. The results indicate that models with higher reinforcement ratio of the beams will result in joint failure under cyclic reverse loading, and their load-displacement curves are pinched and ultimate bearing capacity would not increase while strength degradation and stiffness degradation would appear obviously.

A New Method to Assess Ductility of CFT Box Columns with Binding Bars under Axial Compression

A new method based on material properties instead of experimental data was proposed to assess the ductility of concrete-filled steel box columns with binding bars and those without binding bars. Comparison between ductility coefficients based on experimental data and the calculated values by the proposed method shows good agreement.

Elasto-Plastic Analysis of Seismic Response of Valve-Hall Structure with Suspension Valves of Large-Scale Converter Station

Elasto-plastic analysis of seismic responses of valve hall structures were carried out by using finite element software, and the effect of seismic waves on the seismic responses of the valve hall structures and suspension equipments were studied. Results show that significant torsional responses of the structure can be found under longitudinal and 3D earthquake actions. Under 3D earthquake actions, the seismic responses of the suspension valves are much more significant than those under 1D earthquake actions, the maximum tensile force of the suspenders is about twice of that under 1D action. The seismic responses of the suspension valves under vertical earthquake actions are much stronger than those under horizontal earthquake actions, when suffering strong earthquake actions; the maximum vertical acceleration of the suspension valves is about 4 times of that under horizontal earthquake actions. It is recommended that the effects of 3D earthquake actions on the structure should be considered in seismic response analysis of the valve hall structure.

Probabilistic Evaluation of Effects of Column Moment Magnification Factor on Seismic Performance of Reinforced Concrete Frames

Enhancing column flexural capacity is the key measure in seismic capacity design to achieve strong column-weak beam failure mode and determinate the probabilistic relation between column moment magnification factor (CMMF). In the paper the effects of column moment magnification factor on seismic performance of reinforced concrete (RC) frames are evaluated to limit the occurrence probability of column-hinging failure modes within an acceptable tolerance. Monte Carlo simulation methodology is used to calculate the probability of drift demand exceeding drift capacity of two typical frame structures with consideration of major uncertainties. And fragility curves are constructed to obtain the relationship between CMMF and probability of structural damages and assess the seismic vulnerability of RC frame structures. Results show that the seismic performance of RC frame structures can be significantly enhanced by improving CMMF. The CMMF is required to be equal to or greater than 2.0 to achieve acceptable probability of exceedance of column-hinging failure mode.

Ductility of Concrete-Filled Steel Box Columns with Binding Bars Subjected to Axial Compression

Ductility of concrete-filled steel box columns with binding bars and those without binding bars were discussed based on the experimental study. Two current methods were used to assess the ductility of concrete-filled steel box columns with binding bars and those without binding bars. Results show that binding bars can increase ductility of concrete-filled steel box columns. Ductility of concrete-filled steel box columns with binding bars at closer spacing is considerably better than that of concrete-filled steel box columns without binding bars.

Experimental Research and Abaqus Analyses of Eccentric-Loaded L-Shape CFT Columns with Binding Bars

Investigations have been carried out to study the mechanical performances of L-shaped CFT columns such as high strength, stiffness, good ductility. In the paper, Nine L-shaped CFT columns stiffened by binding bars and one without stiffeners subjected to eccentric-load are reported. The experimental results are compared with the results calculated by the abaqus. The proposed method provide theoretical basis for relative design codes.

Evaluation of N-M Model on Simulating Seismic Response of High-Rise SRC Structure

The axial load-biaxial bending moment interaction model (N-M model) is developed based on the metal plasticity theory, and its reliability in structural analysis is evaluated. Employing CANNY program, linear and nonlinear dynamic time history analysis is conducted to a 32-story SRC structure. The dynamic responses are compared between N-M model and fiber model cases. The results show that N-M model can simulate well the dynamic response of the high-rise hybrid structures. Besides, N-M model has clear mechanical concept and is much simpler compared to fiber model, and the computational efficiency can be greatly improved by using N-M model.

Application of Modified Consistent Mode Imperfection Method in Stability Analysis of Single-Layer Reticulated Shells

Based on the probability reliability theory, this paper proposes a modified consistent mode imperfection method, which fits the integral stability analysis of single-layer reticulated shells with the initial geometric imperfections. Nearly 1000 elasto-plastic load-deflection overall processes of four different rise-to-span ratio for Kiewitt-8 single-layer reticulated shells are analyzed by using the random imperfection mode method, the consistent mode imperfection method and the modified consistent mode imperfection method respectively. The study shows that the random imperfection mode method can assess the influence of initial geometric imperfections on structure stability more scientifically, but the calculation is quite large. By using the consistent mode imperfection method, the buckling load is not sure to be the most unfavorable, and the degree of reliability couldnt be ensured effectively. The modified consistent mode imperfection method can gain the buckling load which meets the requirement of probability reliability with less calculation. It can also assess the stability performance of single-layer reticulated shell structure more reasonably and safely.

Mechanics Analyzing of Suspended Formwork Supporting System and Research of Decision System in Constructing Transfer Storey Structure of Steel Reinforced Concrete

This article introduced the research of suspended formwork in constructing transfer storey structure of steel reinforced concrete, and the co-working principle of beam and supporting system, and the design theory of suspended formwork method. The author farther founded construction decision system through analytic hierarchy process, and applied in construction site successfully.

A New Method to Estimate Ductility of L-Shaped CFT Columns with Binding Bars under Axial Compression

Ductility of six L-shaped concrete-filled steel columns with binding bars and one without binding bars were discussed based on the experimental study. A new method based on material properties instead of experimental data was proposed to estimate the ductility of six L-shaped concrete-filled steel columns with binding bars and one without binding bars. Comparison between ductility coefficients based on experimental data and the calculated values by the proposed method shows good agreement.