ORCID Profile
0000-0002-1974-7636
Current Organisation
Hebei University of Technology
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Publisher: Elsevier BV
Date: 2023
Publisher: SAGE Publications
Date: 13-06-2019
Abstract: Although marked advancements have been achieved to improve the computer power, progressive collapse analysis of large-scale reinforced concrete structures is still time-consuming or even impractical. In this study, a numerical model is proposed for efficient progressive collapse analysis of reinforced concrete structures. Recent advancements that can accurately and efficiently model the mechanical behavior of structural components are incorporated in the numerical model of reinforced concrete structure. The beams/columns, joint regions, and slabs are modeled by enhanced fiber beam element, macrojoint model, and layered shell element, respectively. In this way, the shear failure of beams/columns, failure of joints, and resistance contribution from floor slab can be taken into account for progressive collapse analysis of reinforced concrete structures. A six-story reinforced concrete frame structure is modeled using the approach proposed in this study. The progressive collapse of the structure is analyzed under column removal and direct blast loading scenarios. For comparison purpose, other popularly used finite element models are also adopted to carry out numerical simulations. The proposed model is proven to yield accurate simulation results with the least cost of time among all models. Based on the proposed model, parametric simulations are performed to investigate effective measures to improve the structural resistance to progressive collapse. It is found that increasing longitudinal reinforcement ratio in beams and columns can increase the catenary action capacity, but hardly increases the compressive arch action capacity. Moreover, the steel mesh reinforcement at top layer of slabs plays a significant role in resisting progressive collapse of reinforced concrete structures, which should be considered in design to resist progressive collapse.
Publisher: Elsevier BV
Date: 2011
Publisher: Springer Science and Business Media LLC
Date: 08-2021
Publisher: Elsevier BV
Date: 2012
Publisher: Elsevier BV
Date: 08-2020
Publisher: Elsevier BV
Date: 09-2022
Publisher: World Scientific Pub Co Pte Lt
Date: 2017
DOI: 10.1142/S0219455417500134
Abstract: Significant research efforts have been invested on studying the response and damage of structures subjected to blast loads for better life and property protections. The single-degree-of-freedom (SDOF) approach has been widely adopted to simplify the structural response analysis for engineering design purpose. However, such an approach under certain circumstances oversimplifies the structural behavior and might not give reliable predictions of structural responses to blast loads. On the other hand, although detailed high fidelity finite element (FE) approach is able to give relatively accurate predictions of structural response, it is unfortunately not straightforward for application and very time-consuming, which impedes its application among engineers. Therefore, a method that can assure not only reliability but also efficiency is highly needed for design practice. In the present study, mode approximation method with Pressure–Impulse (P-I) diagrams is applied to analyze response and damage of RC slab due to blast load. Slab under analysis is assumed rigid-plastic and simply supported. Shear failure, bending failure and combined failure modes are considered based on different failure modes. Critical equations for structural shear and bending failures are derived respectively with appropriate failure criteria. P–I diagrams are then developed for quick damage assessments. The analytical results are verified by comparing with high fidelity numerical simulations. The reliability and efficiency of using this approach for design and analyzing RC slab response under blast loads are demonstrated.
Publisher: Elsevier BV
Date: 10-2013
Publisher: Elsevier BV
Date: 11-2022
Publisher: SAGE Publications
Date: 06-2011
DOI: 10.1260/2041-4196.2.2.177
Abstract: The dynamic strength of concrete materials is usually obtained by conducting laboratory tests such as drop-weight test or split Hopkinson pressure bar (SHPB) test. It is widely accepted that the uniaxial compressive strength of concrete and concrete-like material increases with strain rate. Many empirical relations of concrete material dynamic increase factor (DIF), which are proposed for use in the design and analysis, are given in the literature. However, most of these empirical relations were obtained from testing data of concrete-like materials, i.e. the testing specimens were made of mortar matrix only without coarse aggregates owing to constraints in preparing the concrete specimens for high-speed impact tests. Because concrete is a composite material with mortar matrix, interfacial transition zone (ITZ) and aggregates, and these components have different material properties, using specimens made of mortar material alone in tests may not give accurate concrete dynamic material properties. It is also known that the lateral inertia confinement affects the dynamic strength of concrete specimens obtained in impact tests. A number of studies to investigate and quantify the lateral inertia confinement effect on dynamic strength of concrete materials obtained in impact tests have been published. Previous studies also indicate that including aggregates in concrete specimens affects the dynamic strength. However, no systematic study that devotes to investigating the influence of aggregates in concrete specimen on its dynamic strength has been reported yet. In the present study, a mesoscale concrete material model is used to simulate impact tests and to study the influences of aggregates on concrete material compressive strength increment at high strain rates. The commercial software AUTODYN is used to perform the numerical simulations. A method to remove the influence from lateral inertia confinement is proposed and verified. The influence of ITZ on compressive behavior of concrete specimen is discussed. Numerical simulations of concrete specimens with different volumetric percentages, e.g. 20% 30% and 40%, of aggregates under impact loads of different loading rates are carried out. The influence of the aggregates on DIF of concrete material is examined and quantified.
Publisher: Elsevier BV
Date: 08-2014
Publisher: SAGE Publications
Date: 04-04-2019
Publisher: SAGE Publications
Date: 06-07-2022
DOI: 10.1177/13694332221113045
Abstract: Discrete short steel fibres were proposed to be mixed with concrete for arresting cracks and enhancing the post-cracking resistance. It has been proven in previous tests that spiral steel fibres possessed markedly higher bonding to concrete matrix, leading to significantly improved performance of steel fibre reinforced concrete (SFRC) in terms of crack controllability, impact resistance, deformability and energy absorption capability. However, at the initial stage of cracking, SFRC reinforced with spiral fibres has relatively lower resistance to crack opening as compared to that reinforced with other types of steel fibres because of spiral shape stretching. To overcome this shortcoming, in the present study, short hooked-end steel fibres that exhibit high pull-out resistance at the crack initiation stage were mixed with spiral steel fibres in the normal-strength concrete matrix. A total volume fraction of 1% of hybrid steel fibres was mixed to cast SFRC specimens. With various mix ratios between spiral and hooked-end fibres considered, five batches of SFRC specimens were tested. Uniaxial compressive tests and four-point bending tests were carried out to compare the mechanical properties of SFRC materials with hybrid fibres while three-point bending tests on SFRC structural beams under static, drop-weight impact and post-impact static loading tests were conducted to investigate the structural performances. An equal dosage of hooked-end and spiral fibres was found to outperform other blend proportions to provide synergetic reinforcement to concrete matrix in terms of post-cracking resistance, energy absorption capacity and post-impact performance.
Publisher: CRC Press
Date: 17-08-2012
DOI: 10.1201/B12768-5
Publisher: Springer Science and Business Media LLC
Date: 06-06-2013
Publisher: Trans Tech Publications, Ltd.
Date: 08-2014
DOI: 10.4028/WWW.SCIENTIFIC.NET/KEM.626.311
Abstract: Concrete is a brittle material, especially under tension. Intensive researches have been reported to add various types of fibres into concrete mix to increase its ductility. Recently, the authors proposed a new type of steel fibre with spiral shape to reinforce concrete material. Laboratory tests on concrete cylinder specimens demonstrated that compared to other fibre types such as the hooked-end, deformed and corrugated fibres the new fibres have larger displacement capacity and provide better bonding with the concrete. This study performs drop-weight impact tests to investigate the behaviour of concrete beams reinforced by different types of steel fibres. The quasi-static compressive and split tensile tests were also conducted to obtain the static properties of plain concrete and steel fibre reinforced concrete (FRC) materials. The quasi-static tests were carried out using hydraulic testing machine and the impact tests were conducted using an instrumented drop-weight testing system. Plain concrete and concrete reinforced by the commonly used hooked-end steel fibres and the proposed spiral-shaped steel fibres were tested in this study. The volume dosage of 1% fibre was used to prepare all FRC specimens. Repeated drop-weight impacts were applied to the beam specimens until total collapse. A 15.2 kg hard steel was used as the drop-weight impactor. A drop height of 0.5 m was considered in performing the impact tests. The force-displacement relations and the energy absorption capabilities of plain concrete and FRC beams were obtained, compared and discussed. The advantage and effectiveness of the newly proposed spiral-shaped steel fibres in increasing the performance of FRC beam elements under impact loads were examined.
Publisher: SAGE Publications
Date: 03-2010
DOI: 10.1260/2041-4196.1.1.145
Abstract: Dynamic material properties, in particular the dynamic strength, of concrete material are usually obtained by conducting laboratory tests such as drop-weight test and Split Hopkinson Pressure Bar (SHPB) test. It is commonly agreed that a few parameters associated with stress wave propagation will affect the test results, including the lateral and axial inertial effect, end friction confinement and stress wave reflection and refraction. Many different measures have been proposed to eliminate or limit the influences of these effects in dynamic tests of material properties. However, owing to the nature of dynamic loadings, especially those with high loading rates, it is very unlikely to completely eliminate these influences in physical testing. Moreover, it is also very difficult to quantify these influences from the laboratory testing data. In the present study, a refined mesoscale concrete material model is developed to simulate impact tests and to study the influences of lateral inertial confinement on concrete compressive strength increment at high strain rate. The commercial software AUTODYN is used to perform the numerical simulations. Numerical simulations of concrete specimens of different dimensions and under impact loads of different loading rates are carried out. The results are compared with those obtained from laboratory tests, with those specified in the code and simulated with homogeneous concrete material model. The reliability of the numerical simulation of impact tests is verified. It is found that the influences of lateral inertial confinement effect on Dynamic Increase Factor (DIF) is strain rate and specimen size dependent. Neglecting aggregates in concrete specimen in laboratory tests and numerical simulations lead to underestimation of DIF of concrete material.
Publisher: SAGE Publications
Date: 03-03-2016
Abstract: Dynamic tensile strength is one of the key factors of concrete material that needs to be accurately defined in analysis of concrete structures subjected to high-rate loadings such as blast and impact. It is commonly agreed that dynamic testing results of concrete material are influenced by the inertia effect, which is very much dependent on the specimen size and loading rate. It is therefore very important to remove the inertia effect in testing data to derive the true dynamic concrete material properties. On the other hand, coarse aggregates in concrete material are usually neglected due to testing limitation or numerical simplification. It has been acknowledged that neglecting coarse aggregates might not necessarily give accurate concrete dynamic material properties. In this study, a three-dimensional mesoscale model of concrete specimen consisting of cement mortar and coarse aggregates is developed to simulate splitting tensile tests and investigate the behaviour of concrete material at high strain rate. The commercial software LS-DYNA is used to carry out the numerical simulations of dynamic splitting tensile tests. The reliability of the numerical model in simulating the dynamic splitting tensile tests is verified by comparing the numerical results with the laboratory test data from the literature. The influence of inertia effect in dynamic splitting tensile tests is investigated and removed. An empirical formula to represent the true dynamic increase factor relations obtained from dynamic splitting tensile test is proposed and verified.
Publisher: Elsevier BV
Date: 10-2021
Publisher: Elsevier BV
Date: 05-2017
Publisher: Elsevier BV
Date: 09-2023
Publisher: Springer Science and Business Media LLC
Date: 12-03-2015
Publisher: Springer Science and Business Media LLC
Date: 16-12-2016
Publisher: Elsevier BV
Date: 05-2023
Publisher: Thomas Telford Ltd.
Date: 11-2016
Abstract: Concrete exhibits excellent resistance to compressive forces, but is brittle and weak in tension. Various types of fibres have been investigated by many researchers to improve the ductility and energy absorption capability of concrete materials and structures under static and blast and impact loadings. Spiral-shaped steel fibres were recently proposed as reinforcement in a concrete matrix and it was found that spiral fibre reinforcement can significantly improve the ductility, crack control ability and energy absorption capacity of concrete material under static and impact compressive loads. This paper presents an experimental study of the static and dynamic properties of steel fibre reinforced concrete (SFRC) materials under splitting tension. SFRC materials mixed with spiral-shaped steel fibres of different volume fractions were prepared and tested. A high-speed camera was used to capture the deformation, failure and crack opening process of the tested specimens. The contribution of spiral fibres to the mechanical properties and behaviour of concrete at high strain rate under splitting tension was investigated. Analyses of the test results revealed the effectiveness of spiral fibres in improving the performance of SFRC (e.g. crack control, energy absorption capability and more pronounced rate sensitivity under dynamic splitting loading). Moreover, crack opening and closing (pull-back by spiral fibres) processes were observed, demonstrating the excellent bonding and outstanding performance of spiral steel fibres in maintaining the integrity of the concrete material, thus resulting in significant improvements in impact resistance and energy dissipation.
Publisher: Elsevier BV
Date: 10-2013
No related grants have been discovered for Yifei Hao.