Results
- Showing results for:
- Reset all filters
Search results
-
Book chapterZhang Z, Wu C, Nie X, et al., 2023,
Connections of Fibre Reinforced Polymer to Steel Members: Numerical Modelling
, Springer Tracts in Civil Engineering, Pages: 211-229This chapter numerically investigates the proposed bonded sleeve connection for joining tubular glass fibre reinforced polymer (GFRP) composites and steel members. Experimental results focused on mechanical responses of such specimens using bonded sleeve connections and conventional steel angle connections were introduced in previous chapter. These results are used to set the benchmark for detailed finite element (FE) modelling in this chapter. In the detailed FE analysis, bolt geometry including head, shank and washer were accurately modelled. Paired contact elements were used for simulating the contact and slip behaviour between bolt shanks and holes, washers and steel or GFRP. The pretension force in the bolts was also taken into account by implementing pretension elements. The FE models developed were first validated against the experimental results in terms of failure mode, moment-rotation curves and strain responses. Parametric studies were then undertaken to investigate the structural behaviour of the bonded sleeve connections considering the effects of major design parameters such as endplate thickness, bonding length, number of bolts, etc. It was found that the endplate thickness dominates the initial stiffness and the elastic moment capacity of the bonded sleeve connection and the presence of central one-sided bolts may improve the elastic moment capacity of the bonded sleeve connection.
-
Book chapterWu C, Zhang Z, Bai Y, 2023,
Connections of Fibre Reinforced Polymer to Steel Members: Experiments
, Springer Tracts in Civil Engineering, Pages: 187-210Timber and steel studs or posts are commonly used in wall constructions for buildings. In this context and with the results from previous chapters, pultruded glass fibre reinforced polymer (GFRP) studs may provide an alternative solution considering their light weight and improved durability. However, integrating the GFRP wall studs to a steel frame structure is challenging, as proper connection methods are required. A sleeve connection was proposed and examined in this chapter for wall studs to steel beams. Pultruded GFRP stud was fastened to the sleeve connector by one of three methods: ordinary bolt, one-sided bolt and adhesive bond. The connector was then fastened to the steel beam through ordinary bolts. Connections with conventional steel angles were also prepared for comparison purpose. A series of moment-rotation experiments were conducted on these stud-to-beam connections. In addition, two stud lengths were designed in order to study the connection behaviour under shear force dominant loading and moment dominant loading conditions. Experimental results were obtained including failure mode, moment-rotation response, shear-rotation response, joint rotational stiffness and capacity. It was found that the bonded sleeve connection outperformed all the other connections and was classified as a rigid and partial strength connection.
-
Book chapterMa H, Wu C, 2023,
Feasibility and performance evaluation of cementitious material mixed with coal gangue solid waste
, Managing Mining and Minerals Processing Wastes: Concepts, Design, and Applications, Pages: 99-130Coal gangue has become one of the largest solid waste in coal-producing countries. Seeking safe disposal and industrial utilization of coal gangue is an important research direction in the academic community. In this chapter, based on the alkali-activated method, preparation of coal gangue geopolymers and alkali-activated coal gangue-slag cementitious material with calcined coal gangue and slag as raw materials is discussed, and the feasibility of coal gangue as cementitious material instead of cement is comprehensively evaluated. The research results showed that coal gangue geopolymers can obtain high early strength, and the hydration products were N–A–S–H gel and other silico-aluminate zeolite phase crystals. The addition of slag can significantly improve the compressive strength of coal gangue geopolymers and produce flocculent C–(A)–S–H gels with high Ca/Si, Ca/Al, and Si/Al ratios, thus increasing the compactness of alkali-activated coal gangue-slag cementitious material. By adding a certain amount of slag as a calcium source, coal gangue can completely replace cement as cementitious material, and the 28-day compressive strength is higher than that of P.O 42.5 cement paste. This chapter provides a research basis for the use of recycled aggregates, reclaimed micropowders, tailing slag, and red mud as cementitious material.
-
Journal articleMa H, Wu C, 2023,
Early Hydration Kinetics and Microstructure Development of MgO-Activated Slag at Room Temperature
, JOURNAL OF MATERIALS IN CIVIL ENGINEERING, Vol: 35, ISSN: 0899-1561 -
Journal articleWu C, Liu S, Guo J, et al., 2023,
Relationship between thermal conductivity and compressive strength of insulation concrete: a review
, Journal of Research Updates in Polymer Science, Vol: 12, Pages: 80-96, ISSN: 1929-5995Developing insulation concrete with high strength is essential for the construction of energy saving buildings. This is important to achieve carbon neutrality in the modern building industry. This paper reviews the existing studies in the literature on insulation concrete. This paper aims to reveal the correlation between the thermal conductivity and strength of concrete and identify the most effective method to make insulation concrete with lower thermal conductivity but higher strength. The review is carried out from two perspectives, including the effects of different foaming methods and various lightweight aggregates. As for the foaming methods, the chemical and mechanical foaming methods are discussed. As for the lightweight aggregates, cenospheres, porous aggregates, aerogels, and phase change materials are assessed. It is clearly observed that the thermal conductivity and compressive strength of concrete can be fitted by a linear function. As for the foaming methods, chemical foaming using hydrogen peroxide is the most effective to produce concrete with relatively lower thermal conductivity and higher compressive strength. For concrete with lightweight aggregates, cenospheres are the best option. Finally, recommendations are made to develop concrete with lower thermal conductivity and higher strength.
-
Journal articleFame CM, Wu C, Feng P, et al., 2022,
Numerical investigations on the damage tolerance of adhesively bonded pultruded GFRP joints with adhesion defects
, Composite Structures, Vol: 301, ISSN: 0263-8223Adhesive bonding has gained increasing acceptance in joining pultruded glass fiber reinforced polymer (GFRP) sections. However, one of the major issues hindering the widespread application of adhesive bonding in building and construction industries is the difficulty in predicting the mechanical behavior of the joints in the presence of adhesion defects. This paper investigates the damage tolerance of the adhesively bonded pultruded GFRP double-strap joints under quasi-static tensile loading using finite element analysis. Defects of various locations (along the bond length), sizes, and numbers were embedded within the bondline. A two-dimensional (2D) stress analysis was conducted to assess the effects of the bondline defects on the out-of-plane displacement, stress distribution, and peak stresses of the joints. Three-dimensional (3D) progressive damage models were further developed to predict residual joint capacity and provide insights into the effects of the adhesion defects on the damage mechanism of the joints. The progressive damage model uses the cohesive zone model (CZM) to simulate progressive interlaminar damage within the adherends as well as adhesive-FRP interface debonding. The proposed FE model was validated with published experimental data, and an excellent correlation was found between experimental and numerical results. The validated model was then used in a parametric study to assess the effects of design parameters such as adhesive types (from highly brittle to highly ductile) and joint geometry (adhesive chamfering, adherend chamfering, and recessing) on the damage tolerance of adhesively bonded joints. This paper also reports a comparative study on the damage tolerance between GFRP double-strap, single-strap, and single-step joints. The stress analysis results revealed that the presence of the bondline defects could increase the out-of-plane displacement of the adherends and the peak shear and peel stresses at the overlap ends. High-stress concent
-
Journal articleWu C, Yu Y, Lei X, et al., 2022,
Experimental study on the effect of steel yielding on the bond behavior between CFRP and steel plate
, Fuhe Cailiao Xuebao/Acta Materiae Compositae Sinica, Vol: 39, Pages: 5062-5073, ISSN: 1000-3851To study the effect of steel yielding on the bond behavior between carbon fiber reinforced polymer (CFRP) and steel plate, a series of tensile tests and finite element analysis were conducted with CFRP-steel double strap bonded joints. With the steel plate thickness and bond length as the variables, the load-displacement curves, effect bond length and failure mode of the bonded joints were obtained through static tensile testing. The results show that the joints with 15 mm thick steel plate maintains elastic until failure. On the other hand, joints with 8 mm thick steel plate with bond length longer than effective bond length exhibit steel yielding when fail. The load-displacement curve becomes nonlinear and ductile with the yielding of the steel plate and the displacement at failure is extensively increased. The failure mode of the bonded joints is CFRP delamination when steel is not yield and is a combination of CFRP delamination and steel-adhesive interface debonding when steel is yield. And the area of steel-adhesive debonding is increasing with a larger area of steel yielding. According to the joint and material properties adopted in this work, when the joint with 8 mm steel plate yields, its maximum failure displacement is about 4.2 times of the joint with 15 mm thick steel plate, but the capacity of the 8 mm joint is only 69.92% of the 15 mm joint. In other words, the ductility of the joint due to steel yielding is achieved at the cost of reduction in capacity. From the results of finite element analysis, it can be found that the failure position would move to bonded end with a larger area of steel yielding and the effective bond length would be shorter.
-
Journal articleMa H, Wu C, 2022,
Mechanical and microstructural properties of alkali-activated fly ash-slag material under sustained moderate temperature effect
, Cement and Concrete Composites, Vol: 134, ISSN: 0958-9465Alkali-activated materials are difficult to maintain strength under very high temperatures in the fire. But results are not available for those materials when subjected to sustained moderate temperature range (i.e. 60 °C–250 °C) which is a more common thermal condition in many engineering applications. In this paper, the mechanical and microscopic properties of alkali-activated fly ash-slag (AAFS) materials under sustained moderate temperature effects are studied. The microscopic properties are characterized by XRD, FT-IR, 29Si NMR-MAS, MIP and SEM-EDS. The results show that AAFS is able to maintain the compressive strength even being treated under 250 °C for 28d. The microscopic characterizations indicate that N-A-S-H gel exhibits greater thermal stability than C-A-S-H and C-S-H gels. However, after the gel loses water under sustained temperature effect, N-A-S-H is hard to reorganize. In other words, when more N-A-S-H is produced due to the addition of more slag, the AAFS becomes more porous with looser microscopic morphology leading to lower compressive strength. It is also found that, after sustained moderate temperature treatment, the gel reorganizes and agglomerates into cluster-like particles, while the matrix becomes more uniform and compact. The sustained temperature helps refine the pore size and improve the volume of connected pores and super-macropores which is helpful to maintain the compressive strength of AASF. This study provides experimental and theoretical basis for the application of alkali-activated materials subjected to sustained moderate temperature effects.
-
Journal articleWu C, Fang W, Cheng Q, et al., 2022,
MXene-regulated perovskite vertical growth for high-performance solar cells
, Angewandte Chemie International Edition, Vol: 61, ISSN: 1433-7851Defects at the interfaces of perovskite (PVK) thin films are the main factors responsible for instability and low photoelectric conversion efficiency (PCE) of PVK solar cells (PSCs). Here, a SnO2-MXene composite electron transport layer (ETL) is used in PSCs to improve interfacial contact and passivate defects at the SnO2/perovskite interface. The introduced MXene regulates SnO2 dispersion and induces a vertical growth of PVK. The lattice matching of MXene and perovskite suppresses the concentration of interfacial stress, thereby obtaining a perovskite film with low defects. Compared with SnO2-based device, the PCE of SnO2-MXene-based device is improved by 15 % and its short-circuit current is up to 25.07 mA cm−2. Furthermore, unencapsulated device maintained about 90 % of its initial efficiency even after 500 h of storage at 30–40 % relative humidity in ambient air. The composite ETL strategy provides a route to engineer interfacial passivation between metal halide perovskites and ETLs.
-
Journal articleWu C, Meng BC, Tam L-H, et al., 2022,
Yellowing mechanisms of epoxy and vinyl ester resins under thermal, UV and natural aging conditions and protection methods
, Polymer Testing, Vol: 114, ISSN: 0142-9418Polymer resins have yellowing issue when subjected to elevated temperatures or UV exposure, which limit their applications in color-sensitive fields. This paper presents an experimental study on the yellowing mechanisms of epoxy and vinyl ester resins under thermal, UV and natural aging conditions. Anti-yellowing methods including air isolation, antioxidant, UV absorber are selected and their effectiveness is assessed. The resins before/and after aging are characterized to analyze their yellowing index, surface morphology, weight loss, mechanical properties (i.e. modulus and Vickers hardness), glass transition temperature and FT-IR spectra. The yellowing mechanisms and the influencing factors are discussed. It is found that the resin yellowing is a result of radical oxidation reaction due to aging, which forms chromophores such as carbonyl groups, double bonds and conjugated structures. Vinyl ester has better yellowing resistance than epoxy. Antioxidant and UV absorber are not effective in terms of anti-yellowing effect, but air isolation has the best performance to slow down the yellowing process. Yellowing in natural environment can be more complicated due to other factors like moisture, wet-dry cycles etc. This study provides an experimental evidence for the study of yellowing mechanisms of polymer resins.
-
Journal articleLiu S-Q, Wu C, Wang D-M, et al., 2022,
Effect of Seawater on Hydration and Sulfate Resistance of Noncement Mortars
, JOURNAL OF MATERIALS IN CIVIL ENGINEERING, Vol: 34, ISSN: 0899-1561 -
Journal articleWu C, Mahmoud MM, Hou C-C, et al., 2022,
Study on the impact performance of RC fences strengthened with high strength strain-hardening cementitious composites
, Structures, Vol: 41, Pages: 349-364, ISSN: 2352-0124This paper presents a numerical study on the impact performance of reinforced concrete (RC) fences strengthened with high-strength strain-hardening cementitious composite (HS-SHCC) through finite element (FE) modeling. To accurately simulate the peculiar material characteristics of HS-SHCC, the MAT_72R3 material model was calibrated and verified against experimental data. A comparison study for RC and HS-SHCC panels subjected to drop hammer impact was conducted to observe the impact performance of HS-SHCC. Results showed that the impact resistance and energy dissipation capacity of HS-SHCC are significantly higher due to its high strength and high ductility. A full-scale study of pick-up truck collisions was then conducted to investigate the response, failure, and best strengthening configuration of conventional RC fences strengthened with HS-SHCC layers. Results showed that both strengthened configurations under moderate impact energy could significantly improve the impact resistance and reduce the residual deflection. While in the case of large impact energy, the back-strengthened RC fence gave notably better performance and higher impact resistance due to the composite effects between RC and HS-SHCC layers. Based on the analysis of the failure modes and energy dissipation, the mechanism of such composite effects was summarized.
-
Journal articleWu C, Tian J, Ding Y, et al., 2022,
Axial compression behavior of pultruded GFRP channel sections
, Composite Structures, Vol: 289, ISSN: 0263-8223Pultruded glass fiber reinforced polymer (GFRP) sections are increasingly used as load bearing elements in civil construction. Their low elastic modulus and thin-walled nature make these sections prone to buckling phenomena when loaded in compression. This paper presents a study on the axial compression behavior of the pultruded GFRP channel sections. Two variables were considered including column slenderness ratio and wall width-to-thickness ratio. Therefore, four channel sections with different dimensions were selected. Seven column lengths ranging from 100 mm to 1400 mm were used for each channel section under axial compression. Three failure modes were observed including section crushing, local buckling and global buckling which were highly related to the column slenderness. Load-displacement curves and compression capacities were reported and compared. Finally, existing analytical design equations in the literature were validated using experimental results. Recommendations on compression design of pultruded GFRP channel sections were made based on the results in the current study.
-
Journal articleMa H, Zhang S, Feng J, 2022,
Early hydration properties and microstructure evolutions of MgO-activated slag materials at different curing temperatures
, Ceramics International, Vol: 48, Pages: 17104-17115, ISSN: 0272-8842 -
Journal articleTam L-H, Wu C, Yan L, et al., 2022,
Editorial: Multi-Scale Investigation on Fiber-Reinforced Composite Materials: From Structural Design, Property Characterization to Engineering Applications
, FRONTIERS IN MATERIALS, Vol: 9, ISSN: 2296-8016
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.
