Papers by Author: Feng Liu

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Authors: Gen Quan Zhong, Yong Chang Guo, Li Juan Li, Feng Liu
Abstract: From micro perspective, crumb rubber concrete (CRC) is viewed as a composite consisting of mortar matrix, aggregates and rubber particle. In this paper, based on random aggregate model with different aggregate shape in planar, the mechanical properties of CRC using linear Mohr-coulomb constitutive relation are studied by nonlinear finite element method under uniaxial compression on mesoscopic. The number of random aggregates is calculated in two-dimension by Walraven formula. Circular random aggregate model, elliptic random aggregate model and polygonal random aggregate model are established. Stress-strain curves under varieties of conditions are derived and compared with the test results. The results show that the simulative stress-strain curve fit the reality very much. In the numerical analysis, the aggregate shape has little effect on the mechanical properties of CRC.
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Authors: Li Juan Li, Min Lin, Feng Liu
Abstract: For a quantitative analysis and better understanding of the stress-strain response and their effects on interface debonding and crack initiation and propagation of alternative hard and soft multi-layers under circumscription loading, to explore methodologies of optimum design of surface multi-layers, large strain elasto-plastic finite element method is used to evaluate the mechanical behaviors of TiN/Ti multi-layer films on rigid substrate under hard asperity indentation. The results show that with the same total thickness of the film, the alternate hard and soft multi-layers with larger ratio could endure larger circumscription loading, and the different total thickness of multi-layers could affect the circumscription loading greatly. So there must be a circumscription loading in this multi-layer film structures. Generally speaking, the circumscription loading has something to do with the material modulus, the radius of the press-head, the thickness ratio of soft and hard layers, and the total thickness of alternate hard and soft multi-layers. For a quantitative analysis of this problem, finite element method is utilized to analyze the phenomena of the plastic indentation. According to analysis of the film deformation, the maximum bending stress, and the surface bending stress, and those parameters that have influence on different alternative films are studied. The study of this paper is expected to provide some theoretical basis for the optimum design of multi-layer film structures.
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Authors: Feng Liu, Li Juan Li, Bing Yuan
Abstract: Multi-objective optimal design of frame structures was carried out by group search optimizer with Pareto solutions theory in this paper. A one bay frame structure was employed to evaluate the performance of group search optimizer. Calculation results show the stochastic algorithm has excellent performance in terms of convergence rate, feasibility, practicality and superiority in structure optimal design.
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Authors: Xu Xiang Wang, Feng Liu, Wen Xian Feng, Lan Zeng
Abstract: Horizontal bearing capacity and seismic resistance of Recycled aggregate Concrete Filled Steel Tube (RCFST) columns under low cyclic loads have been analyzed by nonlinear finite element software in this paper. A three-dimensional nonlinear finite element (FE) model was developed, and some parameters that affect the restoring force model of RCFST columns were studied, including axial compression ratio, steel ratio, steel yield strength, strength of core recycled aggregate concrete and recycled aggregate substitution rate. Analysis results show that, along with steel ratio, steel yield strength and recycled aggregate substitution rate increasing, seismic resistance of RCFST becomes better. However, the increase of core recycled aggregate concrete and axial compression ratio will weaken seismic resistance of RCFST columns.
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Authors: Xin Jian Xu, Li Juan Li, Wen Chao Zhou, Ming Min, Feng Liu
Abstract: This paper presented the on-site test results on two-way RC slabs with and without FRP-strengthening. Two slabs strengthened with BFRP, one slab strengthened with CFRP and one slab without strengthening were tested on a practical engineering structure being repaired. The effects of different load cases on mid-span deflection, distribution of stresses around the steel bars at the top and bottom of slabs were analyzed.
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Authors: Gen Quan Zhong, Li Juan Li, Feng Liu
Abstract: The size optimization of truss-plate composite structure is presented in this paper. Two improved random optimization algorithms, heuristic particle swarm optimizer (HPOS) and quick search optimizer (QGSO), are combined with finite element method to achieve the optimal design of truss-plate structure. The discrete variables are converted by the mapping function method. An example of the composite structure is given to test this two improved random optimization algorithms. The results show that the QGSO have a better convergence rate than the HPSO in the early time. They are all converged at the same fitness value and feasible on composite structure optimization.
2361
Authors: Feng Liu, Jiang Zhu, Zhou Li Wen, Li Juan Li
Abstract: Based on high strength concrete (HSC), the improved HSC concrete was produced by adding different contents of fine grain rubber particles and polypropylene fibers. The grain size of the rubber particle is 420 m and the rubber content is 1%, 2%, and 3% of the mass of cementitious material respectively. The volume fraction of polypropylene fiber is 0.1%.The performance of HSC, rubber particle improved high strength concrete (RHSC), polypropylene fiber improved high strength concrete (PHSC) and polypropylene fiber hybrid rubber particle improved high strength concrete (PRHSC) before and after high temperature are studied. The investigation methods used are the external surface inspection, weight loss and residual strength testing. The experimental results show that rubber particles can improve the workability of HSC and PHSC under normal temperature. Polypropylene fiber can significantly improve the spalling failure resistance property of HSC and RHSC.
403
Authors: Feng Liu, Gui Xuan Chen, Li Juan Li
Abstract: The effects of recycled rubber powder on working abilities, density and compressive strength of high strength concrete (HSC) at room temperature were studied in this paper. The characteristics of rubberized high strength concrete (RHSC) after fire was investigated by surface observation, weight loss and retained strength testing. The sieve number of rubber powder used in test is No.40 (420μm), No.60 (250µm) and No.80 (178µm), and the content of rubber powder filled in RHSC is 1%, 2%, 3% and 4% with respect to cementation material respectively. Test results show that the increase in rubber powder content reduces the concrete strength, while the decrease in compressive strength of RHSC is less than 10% when the content of rubber powder is within 2%. RHSC with small content of rubber (1%) can restrain the spalling failure of concrete under high temperature.
1403
Authors: Jian He Xie, Pei Yan Huang, Feng Liu, Yong Chang Guo
Abstract: Debonding failure mode usually occurs in the concrete structure flexural strengthened with fiber reinforced polymer (FRP) under cyclic loading. This paper presents an experimental investigation into the fatigue behavior of the FRP-concrete interface of reinforced concrete (RC) beams strengthened with prestressed FRP. 8 small-scale beams were tested under three-point bending cyclic loading. The propagation behavior of the fatigue interface cracks is addressed, and curves showing the growth law of interface cracks are presented. Results from these tests show that the propagation process of interface cracks had three stages, including rapid, stable and unstable growth. The stable propagation phase experienced the most part of the whole test, and the failure mode of all failed beams was debonding following the fatigue fracture of the tensile steel bars. In addition, the influence of FRP prestressing level on the fatigue lives of strengthened beams is discussed, and an empirical formula is developed to predict the fatigue lives of such members. The results show that the fatigue life increases with the prestressed level of FRP. This study provides an insight on the potential long-term performance of FRP-strengthened beams submitted to fatigue loading conditions.
177
Authors: Wan Hu Zheng, Li Juan Li, Feng Liu
Abstract: The deformation of rubberized concrete under uniaxial compression and three-point flexure is studied in this paper by test, and the load-deflection curves and load-strain curves under three-point flexure are obtained. Three rubberized concrete, with 5%, 10% and 15% rubber contents, were tested. The test results show that rubber powder influences the compressive strength and flexural strength of concrete. The greater of the rubber dosage, the greater of the strength decreasing of concrete. The decline of compressive strength is greater than flexural strength, the ratio of flexural strength to compressive strength of rubberized concrete is 1.08, 1.16, 1.26 times of the normal concrete for three different rubber contents respectively. And the ultimate tensile strain of rubberized concrete is 1.62, 2.25, 2.80 times of the normal concrete respectively. The addition of rubber improved the toughness and deformation ability of the normal concrete.
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