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Jing-Jing Huang,1,* Lin Jia,2,3,* Qiao-Jun Zhang,4 Hao-Hong Li,5 Da-Li Zheng,2 Ming Zheng3 1Second Department of Dental Implant, School and Hospital of Stomatology, Fujian Medical University, Fuzhou, 350001, People’s Republic of China; 2Fujian Key Laboratory of Oral Diseases, Fujian Biological Materials Engineering and Technology Center of Stomatology, School and Hospital of Stomatology, Fujian Medical University, Fuzhou, Fujian, 350004, People’s Republic of China; 3Department of Prosthodontics, School and Hospital of Stomatology, Fujian Medical University, Fuzhou, 350001, People’s Republic of China; 4Zhongshan Hospital Affiliated to Xiamen University, Xiamen, 361000, People’s Republic of China; 5College of Chemistry, Fuzhou University, Fuzhou, Fujian, 350116, People’s Republic of China*These authors contributed equally to this workCorrespondence: Ming Zheng, Department of Prosthodontics, School and Hospital of Stomatology, Fujian Medical University, 246 Yangqiao Middle Road, Fuzhou, 350001, People’s Republic of China, Tel +86-591-83736431, Email zmdentist@163.com Da-Li Zheng, Fujian Key Laboratory of Oral Diseases, School and Hospital of Stomatology, Fujian Medical University, 88 Jiaotong Road, Fuzhou, 350004, People’s Republic of China, Tel +86-591-83720599, Email dalizheng@fjmu.edu.cnPurpose: To investigate the inhibition of Streptococcus mutans (S.mutans) and its biofilm by AgBr-nanoparticles (NP) @CTMAB (cetyltrimethyl-ammonium bromide) and evaluate the changes in Polymethyl methacrylate (PMMA)’s surface roughness (Ra), microhardness, and flexural strength during prolonged immersion in AgBr-NP@CTMAB for application in the denture cleaning industry.Patients and Methods: The antibacterial activity of AgBr-NP@CTMAB against S.mutans was measured colony formation assay, OD600 and laser confocal microscopy. Changes in the specimens’ values for surface roughness, microhardness, and flexural strength (MPa) were measured after i

Inspired by sonic engineering, locally resonant metamaterials have attracted much attention from researchers in civil engineering for their unique characteristics of stress wave attenuation and vibration control capacities. This paper presents a comprehensive review of the latest progress of locally resonant metamaterials and their potential applications in civil engineering for structure protection against dynamic loads. The concepts of metamaterials for stress wave attenuation are introduced first, followed by a comprehensive overview of the historical origins and development of metamaterials. Existing analytical approaches for metamaterials, including theoretical solutions, numerical simulations, and experimental examinations, are summarised. Commonly used meta-structures with internal or external resonators and their applications are reviewed and discussed. Research gaps and future outlooks are also identified and briefed.

Bridge damage detection is crucial for ensuring the safety and integrity of the bridge structure. Traditional methods for damage detection often rely on manual inspections or sensor-based measurements, which can be time-consuming and costly. In recent years, computer vision techniques have shown promise in bridge displacement measurement and damage detection. The objective of this study is to extract reliable features from displacement measured with computer vision-based method that are sensitive to structural condition change while robust to the variation of operational condition. In particular, thisresearch paper presents a novel approach for bridge damage detection using an indicator defined based on the transverse influence ratio (DTIR) from computer vision-based displacement measurements. The proposed method utilizes computer vision algorithms to extract bridge girder displacement responses under moving load. The DTIR indicator, defined as the vehicle-induced bridge quasi-static displacement ratio between two adjacent girders, is extracted as the damage-sensitive feature. Theoretical derivation proves that DTIR indicator is only related to the structural condition and the transverse position of a vehicle over the deck, while independent of the variation of vehicle weight and speed. To validate the effectiveness of the proposed method, a series of drive-by experiments were performed on a multi-girder beam bridge with different structural conditions. The results demonstrated the capability of the proposed approach in accurately detecting the occurrence and possible location of structural damage. Furthermore, the paper discusses the advantages and limitations of the DTIR indicator for bridge damage detection, as well as how to generalize the proposed method to bridges with more than two traffic lanes. In conclusion, the proposed method offers a promising solution for low cost, easy deployable and scalable health monitoring solution for bridges under operating cond

Engineered microbial consortia often have enhanced system performance and robustness compared with single-strain biomanufacturing production platforms. However, few tools are available for generating co-cultures of the model and key industrial host Saccharomyces cerevisiae. Here we engineer auxotrophic and overexpression yeast strains that can be used to create co-cultures through exchange of essential metabolites. Using these strains as modules, we engineered two- and three-member consortia using different cross-feeding architectures. Through a combination of ensemble modelling and experimentation, we explored how cellular (for example, metabolite production strength) and environmental (for example, initial population ratio, population density and extracellular supplementation) factors govern population dynamics in these systems. We tested the use of the toolkit in a division of labour biomanufacturing case study and show that it enables enhanced and tuneable antioxidant resveratrol production. We expect this toolkit to become a useful resource for a variety of applications in synthetic ecology and biomanufacturing.

Interlocking brick masonry has gained much attention due to its high construction efficiency and low labour skill requirement. Most designs of interlocking bricks only use interlocking keys to provide alignment for easy construction, and most previous studies of interlocking masonry structures concentrate on their static loading capacities. This study examines the behaviour of reinforced mortarless interlocking brick walls under cyclic loading. Interlocking brick wall made of a specific type of interlocking bricks with large keys that provide not only alignment in construction but also shear resistance is constructed and tested under in-plane cyclic loading. A detailed numerical model is generated and validated with the testing data, which is then used to assist the analysis of wall responses. The damage mode, hysteresis response and energy dissipation characteristics are analysed. The test results are compared with conventional masonry wall from literature to demonstrate the superior performance of interlocking masonry wall in resisting seismic loading and dissipating seismic energy. The influences of axial precompression and shear span-to-length ratio are investigated via numerical modelling.

Hydrogen is one of the most promising renewable energies that has been observing rapid development over the past years. Recent accidental explosion incidents and the associated damages have demonstrated the importance of hydrogen safety against potential explosions. This article presents a systematic review on hydrogen explosions. Potential explosion scenarios including the existence of impurities and rich-oxygen environment in the production, storage with extreme-high pressure and ultra-low temperature, transportation, and consumption processes are reviewed. Different types of hydrogen-air cloud explosion include expansion and deflagration, detonation, and deflagration-to-detonation transition (DDT). Existing studies on hydrogen explosion covering laboratory and field blasting test, numerical simulation utilizing various computational approaches, and theoretical derivation are reviewed and summarized. CFD modeling is currently one of the main research methods because of its cost effectiveness, though challenges existing in simulation hydrogen-air cloud detonation comparing with testing results. Apart from the properties of hydrogen-air cloud such as concentration, size and heterogeneity, environmental factors such as ignition, ventilation and obstacle are found to strongly influence the loading characteristics of hydrogen-air cloud explosion. Existing prediction approaches for estimating blast loading from hydrogen-air cloud explosion including the TNT equivalent method (TNT-EM), TNO multi-energy method (TNO MEM), and Baker-Strehlow-Tang method (BST) are primarily empirical based. Because of the inherited difference of hydrogen-air cloud from solid explosives and conventional flammable gases, the accuracies of these approaches are still doubtable, which requires further study.

Geopolymer concrete (GPC) as a green construction material has the potential to substitute traditional concrete, but there is a lack of understanding of the performances of geopolymer concrete structures subjected to dynamic loadings. This study investigates the dynamic responses of reinforced concrete slabs made of ambient cured alkali-activated GPC under static and dynamic concentrated load. Laboratory tests are performed which revealed that GPC slabs exhibited typical punching shear failure model under both static and impact load. Current design codes including ACI, Eurocode 2 and CSCT model can well predict the static punching resistance capacity of GPC slab, but fail to predict the dynamic punching resistance. Numerical modelling is carried out to investigate the dynamic punching shear mechanism. The results indicate that the impact response of GPC slab is highly influenced by inertial effect. In the initial response stage the impact force is mainly resisted by the slab inertial resistance. The GPC dynamic material properties and structural dynamic amplification effect affect the dynamic response and damage of GPC slabs. Intensive numerical simulations are performed to quantify the influences of slab thickness, reinforcement ratio, impactor weight and impact velocity on impact responses of GPC slabs. Empirical formula is derived based on the test and numerical results to predict the dynamic punching resistance of reinforced GPC slabs.

In this study, an experimental program was performed to investigate the cyclic friction-slip behaviour of AS/NZS 3678-350 (G350) steel with different surface finishes. Fifteen bolted steel connections consisting of EN 1090-2 slip factor test assemblies with M16 bolts were prepared and tested with five commonly used surface finishes including inorganic zinc silicate (IZS), epoxy zinc primer (EZP), aliphatic acrylic polyurethane (PUR), abrasive blasted (SA2), and clean mill scale (CMS). The first initial force-slip stiffness and the first slip factor are reported for each surface finish and compared with the existing literature and design standards. An empirical model is proposed to predict the initial slip behaviour based on the first slip factor and initial stiffness, and its accuracy is demonstrated for the coated and uncoated steel. The effects of the cyclic load are then considered, and the cyclic slip factor and initial stiffness are evaluated and discussed. Finally, corresponding empirical models are proposed for the cyclic slip factor and friction-slip stiffness as a function of the cumulative displacement.

Liang-Wen Shi,1,* Quan-Quan Zhuang,2,* Tai-Qin Wang,1 Xian-Dong Jiang,3 Yue Liu,4 Jing-Wen Deng,1 Huan-Huan Sun,5 Yi Li,4 Hao-Hong Li,4 Ting-Bo Liu,6 Jian-Zhi Liu1 1Department of Otorhinolaryngology, Fujian Medical University Union Hospital, Fuzhou, Fujian, People’s Republic of China; 2Department of Pharmacy, Affiliated Quanzhou First Hospital of Fujian Medical University, Quanzhou, Fujian, People’s Republic of China; 3Department of laboratory medicine, the School of Medical Technology and Engineering, Fujian Medical University, Fuzhou, Fujian, People’s Republic of China; 4College of Chemistry, Fuzhou University, Fuzhou, Fujian, People’s Republic of China; 5Department of Otolaryngology, Changji Region Hospital of Traditional Chinese Medicine, Changji, Xinjiang, People’s Republic of China; 6Fujian Institute of Hematology, Fujian Provincial Key Laboratory of Hematology, Fujian Medical University Union Hospital, Fuzhou, Fujian, People’s Republic of China*These authors contributed equally to this workCorrespondence: Jian-Zhi Liu, Department of Otorhinolaryngology, Fujian Medical University Union Hospital, Fuzhou, Fujian, People’s Republic of China, Tel/Fax +86-591 83346181, Email liujianzhient@163.com Ting-Bo Liu, Fujian Institute of Hematology, Fujian Provincial Key Laboratory of Hematology, Fujian Medical University Union Hospital, Fuzhou, Fujian, People’s Republic of China, Tel/Fax +86-591 83357896, Email liutingboblood@163.comBackground: Drug-resistant microbes pose a global health concern, requiring the urgent development of effective antibacterial agents and strategies in clinical practice. Therefore, there is an urgent need to explore novel antibacterial materials to effectively eliminate bacteria. The synthesis of quaternary phosphonium salt in haloargentate systems, wherein the phosphorus atom is represented in a cationic form, is a possible strategy for the develo

The design philosophy and methodology of civil engineering structures have been constantly evolving, from the early strength-based to more recent performance-based design and the current intensively researched emerging resilience-based design. Because failure of civil engineering structures often leads to catastrophic consequences, the primary focus of all these design methods is the safety of structures while considering other aspects such as performance and resilience. With the economic growth, population increase and urbanization, as well as global warming and the depletion of natural resources, to meet the societal need for sustainable development, the construction of civil engineering structures also needs to consider sustainability, durability and smart lifecycle management besides safety, performance and resilience. This paper discusses the necessity, challenge and opportunity for the development of the next generation design of sustainable, durable, multi-hazard resistant, resilient and smart civil engineering structures, which are named as SDuMuRS. Five key aspects are identified for the construction of next generation structures including: (1) sustainability; (2) durability; (3) multi-hazard resistance; (4) resilience; and (5) smart lifecycle structural health monitoring and management. Critical reviews and discussions on each of these aspects are presented. Research directions are suggested accordingly for achieving these goals for the design of next generation civil engineering structures. While this paper tries to cover as much as possible in the review and discussion of these five aspects, it by no means is inclusive of the relevant studies, but sheds light on these important aspects and opens the discussions for the development of next generation design of civil engineering structures.

A novel design of Sandwich Structure inspired by Beetle Forewing (SSBF) is proposed in this study by mimicking the internal structure of beetle forewing. The viscoelastic material and the arch shape of hollow cavity structures found inside the forewing structure of the beetle are imitated by utilising the shear thickening fluid (STF) and semi-arch cores, respectively. The coupling interaction between fluid and structural components is analysed using a fluid-structure interaction (FSI) technique in LS-DYNA. It is found that the proposed SSBF by partially filling the core with STF generates a higher mean crushing force and stabilises the crushing force-displacement profile without a noticeably high initial peak crushing force as compared with the empty, polyurethane (PU) foam-filled, or Newtonian viscous fluid-filled counterparts. Furthermore, this stable crushing force of SSBF enhances with the increase of crushing speed, showing ideal behaviour for energy absorption and crushing resistance for the adaptation to the design of structures to resist impact loads.

Previous researches showed that the replaceable coupling beam damper (RCBD) can effectively enhance the seismic performance of shear wall structures. However, the extensively studied metallic-type RCBD has poor fatigue performance, while the viscoelastic-type RCBD is sensitive to the loading frequency. To overcome the drawbacks of the RCBD mentioned above, this paper proposes a novel RCBD, i.e., the lead-viscoelastic coupling beam damper (LVCBD), which is not only independent of the loading frequency, but also has better fatigue performance with good energy dissipation capacity. The proposed LVCBD mainly consists of three components, i.e., the lead rods, composite viscoelastic layers and steel plates. Taking advantages of the hyper-elasticity property of rubber and the dynamic recrystallization capability of lead, the combined effects from the rubber and lead make the LVCBD reusable after a severe earthquake, and facilitate the post-earthquake recovery with less or without replacement of the RCBD. To examine the performance of the proposed novel damper, three specimens were manufactured and cyclic loading tests were carried out. The influences of the loading amplitude, loading frequency and fatigue loading on the mechanical properties of the specimen were systematically investigated and discussed. Experimental results indicated that the LVCBD showed a favorable deformation capability, frequency-independent performance, fatigue resistance and stable energy dissipation capacity under cyclic loading.

Vibration displacement of civil structures are crucial information for structural health monitoring (SHM). However, the challenges and costs associated with traditional physical sensors make displacement measurement difficult. In recent years computer vision (CV) techniques have been employed for measuring vibration displacement in civil structures. There has been a growing interest in CV-based three-dimensional (3D) displacement measurement, as it provides comprehensive information for structural health assessment. Most existing methods use multi-view geometry, requiring multiple cameras for depth measurement. This paper proposes a new system for measuring the 3D vibration displacement utilising a single camera. Instead of using multi-view geometry, deep neural networks are utilised to learn the depth of scenes from monocular images. Compared with the multi-view methods, the proposed 3D measurement system with monocular vision is more cost-effective and much more convenient to set up and use in practice, avoiding the complicated calibration and object matching between multiple cameras. Experimental tests are conducted in the laboratory to investigate the feasibility of the proposed system. Physical displacement sensors are equipped with the testing structure to provide the ground truth data. The results demonstrate that the proposed monocular 3D displacement system is able to produce reasonable 3D full-field displacement measurement, which makes monocular image based CV system a promising approach to achieve 3D displacement measurement, with its obvious advantages in cost and convenience compared to the traditional sensor-based or multi view CV-based methods.

In the design of reinforced concrete (RC) structures subjected to impulsive loading, usually an equivalent Single-Degree-of-Freedom (SDOF) system is derived based on a constant deflection shape assumption corresponding to static-loading condition. It is commonly known that this idealized assumption may not necessarily lead to accurate predictions of structural responses. This paper presents an improved analytical approach to predict the dynamic response of RC beams with consideration of stress wave propagation effect in the beam in the initial stage upon impact load application, and time-dependent shape function for SDOF analysis. The response of a structural component is divided into two phases: local response phase which is calculated using governing equations of stress wave propagations; and global response phase analyzed using the equivalent SDOF systems with considerations of time-dependent deformation shapes. Laboratory drop-weight impact tests are performed on RC beams, which are used to validate the developed method. Further validation is carried out against existing testing results by other researchers, demonstrating the proposed approach offers more accurate predictions of RC beam responses under impact loading compared to the conventional SDOF method.

Precast concrete (PC) structures have been popularly used in construction practice and PC beam-column joints are critical for structural integrity and safety. In this study, dynamic responses of one monolithic reinforced concrete (RC) joint and three PC joints with different wet connection configurations were investigated by using a pendulum impact test system. The impact behaviours of monolithic RC and PC joints were examined and compared in terms of failure modes, dynamic responses, and energy dissipation. The effects of various wet connection configurations on the dynamic response of PC joints were discussed and analysed. It is found that the interface damage between PC beam and joint led to the reduced integrity of the PC joints. In addition, numerical models of beam-column joints were developed by using software LS-DYNA and calibrated by the test data. The calibrated numerical model was used to investigate the influences of various wet joint configurations on its performance subjected to impact at different locations. Numerical results showed that the shear key and interface rebar employed for wet connections were beneficial to resist shear-governed damage but less effective in resisting flexural-governed damage induced by impact loads. Therefore, the wet connections should be properly designed for PC joint to resist the designated impact loading scenarios.

This study proposes a new hybrid concrete joint using glass fibre reinforced polymer (GFRP) bolts and reinforcements to replace steel bolts and reinforcements for corrosion damage mitigation. The experimental results indicate that the proposed hybrid concrete joints satisfy the seismic-resistant requirements with respect to the ductility and energy dissipation. The energy dissipation of the hybrid concrete joint was approximately 57% higher than the reference monolithic joint. In addition, the application of GFRP bolts and reinforcements not only avoided brittle failure during the test but also showed excellent behaviours in terms of the drift ratio, ductility, and energy dissipation. Numerical simulation using ABAQUS software was also carried out, which successfully captured the failure modes, drift ratios, and peak loads of the dry, hybrid, and monolithic joints. The numerical results proved that the common assumptions which were adopted in the proposed models of the previous studies (Ngo et al., 2020; Ngo et al., 2020) [1,2] were reliable to predict the peak loads. The ratio of the thickness of the concrete-end-plate (CEP) over the height of the beam of 1.3 was the optimal value and it can be used in CEP design of the dry joint. Finally, the developed three-dimensional finite element (3D-FE) model verified with the testing data can be confidently applied in future studies to investigate the seismic performances of the dry, hybrid, and monolithic beam-column joints using GFRP reinforcements and bolts.

A new design is proposed for the meta-panel that consists of three components including two thin face-sheets bonded to meta-truss cores to enhance its blast resistance and energy absorption capacity. The meta-truss core comprising solid inclusions with coated soft layers exhibits exceptional wave-filtering properties by activating the local vibration of the inclusions, leading to the negative effective mass and stiffness of the meta-truss core in the corresponding frequency bandgaps, hence reducing the wave propagations. When frequencies of the applied loading fall within the bandgaps, the loading effects are not able to be transferred or significantly mitigated by the meta-truss core. In this study, the result from a previous theoretical derivation of wave propagation in an idealized meta-truss bar is used to validate the numerical model. Then, analyses of the meta-truss core configurations, e.g. the inclusion arrangement and inclusion shape on its bandgap regions and the transient responses of the meta-panel are carried out with the verified numerical model. It is revealed that a complete wave attenuation design can be achieved by utilizing properly tailored arrangements of inclusions, leading to a significantly improved protective effectiveness of the panel against blast loading. The results present a base for the optimal design of the meta-panel for structural protections against blast loading.

This paper presents a state-of-the-art review of the experimental methods for inter-module joints (IMJs) in modular buildings. For the structural response, three levels of study are defined: module (M), frame (F), and joint (J). The joint (J) tests are further classified based on three setups, namely the beam-column (BC) subassemblage with column loading (J/C), the BC subassemblage with beam loading (J/B), and the stub column assembly (J/S). The experimental setups and loading protocols are outlined with reference to the existing literature, and the inherent assumptions and the relative advantages and disadvantages are discussed with the aim of promoting consistency. A case study modular building frame is defined to illustrate the three levels of study (M, F, and J), and the unbraced and braced frames are subjected to lateral loads to demonstrate the effect of bracing on the structural response. The J/C test is shown to be best suited for application to unbraced frames, while the J/S test is more suited to braced frames. Unbraced frames are shown to be vulnerable to failure of the welded beam-to-column connection which can occur in the joint tests before the specimen displacement is large enough to reveal the IMJ behaviour. A summary is given of the existing beam-to-column joint (BCJ) enhancement methods which can strengthen the BCJ and enable measurement of the IMJ behaviour in the tests. The paper concludes with a summary of the experimental methods, recommendations for standardisation, and the key technical challenges and future research directions.

This study proposes using glass fiber-reinforced polymer (GFRP) as a stay-in-place structural formwork for casting bridge decks with ultrahigh-performance concrete (UHPC). The GFRP stay-in-place formworks completely replace the bottom layer of rebars, and the top steel reinforcement is also replaced by a GFRP mesh to mitigate the corrosion damage. The formworks were either a flat GFRP plate with square hollow section (SHS) stiffeners or a flat GFRP plate with new Y-shape stiffeners. Concentric static tests on five 1:2.75 scale decks were performed to investigate the effect of stiffener's configuration and the influence of the concrete strength on the performance of bridge decks. Rotational fixity support was used to simulate a real bridge deck connection of supporting girders. All specimens with the stay-in-place formwork exhibited punching shear failure. It was found that the use of Y-shape stiffeners significantly improved the load-carrying capacity of the proposed deck. Replacing normal concrete with UHPC further improved the loading capacity of the deck. The decks demonstrated excellent performance, with the load-carrying capacity 3.8-9.5 times higher than the established equivalent service load depending on the concrete strength and configuration of the GFRP stay-in-place formwork. Deflection at service load was less than span/1,600 for all the decks. Compared with normal-strength concrete (34 MPa), UHPC improved the maximum load-carrying capacity of the deck from 91.4 to 149 kN.

This study investigated dynamic performances of concrete beam-column joints under various impact loading scenarios including impact contact condition (i.e., impact directly or via an interlayer), impact location, and impact loading pattern (i.e., concentrated or distributed loads). The influence of impact contact conditions was experimentally studied by a pendulum impact testing system. The test results showed that the softer contact by using a rubber pad led to an impact force profile with a less prominent force peak but resulted in more flexural concrete cracks on the beam. Furthermore, the finite element models of beam-column joints under impact were developed and verified by the test results. Based on the calibrated numerical models, the effects of impact location and impact loading pattern on the dynamic performances of joints were investigated. It was found that the specimens exhibited more flexural-governed cracks as the impact location moved away from the joint area. In addition, the distributed impact loading pattern resulting from an impactor with a wider contact area caused higher impact force, larger displacement response of beam, and severer damage at joint area than those generated by the concentrated impact loading pattern of the same kinetic energy, indicating the distributed impact loading is a more dangerous impact scenario to the safety of beam-column joints.

The application of geopolymer concrete (GPC) in construction could reduce a large amount of carbon dioxide (CO2) emission, which is greatly beneficial to environmental sustainability. Structures made of GPC might be subjected to extreme loading such as impact and blast loads. Therefore, a good understanding of the dynamic properties of GPC is essential to provide reliable predictions of performance of GPC structures subjected to dynamic loading. This study presents an experimental investigation on the dynamic compressive and splitting tensile properties of ambient-cured GPC using split Hopkinson pressure bar (SHPB), with the strain rate up to 161.0 s-1 for dynamic compression and 10.3 s-1 for dynamic splitting tension. The failure mode and damage progress of GPC specimens, energy absorption, and dynamic increase factor (DIF) were studied. Test results showed that ambient-cured GPC exhibited strain rate sensitivity. The compressive and splitting tensile DIFs increased with the strain rate and the ambient-cured GPC with lower quasi-static compressive strength exhibited higher DIFs under both dynamic compression and splitting tension. Empirical formulas were proposed to predict the DIF of ambient-cured GPC. Furthermore, the specific energy absorption of ambient-cured GPC under dynamic compression increased approximately linearly with the strain rate.

During service life, road tunnels may face threats of accidental explosions, e.g., Boiling Liquid Expansion Vapour Explosions (BLEVEs) due to accidents of vehicles transporting hazardous goods inside the tunnels. However, very limited study has investigated the influence of BLEVEs inside a tunnel on its dynamic response. The present study numerically investigates the dynamic response of an arched tunnel subjected to an internal BLEVE by using the software LS-DYNA. The BLEVE load is directly simulated by using commercial code FLACS or approximated by the commonly used TNT equivalency method to investigate the influences of loading predictions on the tunnel responses. The results show that the corner and upper arc of arched lining are more prone to be damaged under the directly predicted BLEVE loads. Compared to the directly predicted BLEVE loads, explosion loads estimated by the TNT equivalency method induce more significant damage to the lining due to its higher peak pressure, but smaller peak displacements since the corresponding impulse is lower than that of the BLEVE load. In addition, parametric studies are conducted to investigate the effects of concrete grade, concrete thickness, steel reinforcement ratio, and stiffness of surrounding rock mass on dynamic response of the arched tunnel subjected to the internal BLEVE. It is found that increasing concrete grade and thickness and enhancing the stiffness of surrounding rock mass are more effective than increasing steel reinforcement ratio in improving the performance of the arched tunnel against internal BLEVE loadings.

This study experimentally examines the effect of rubber aggregate size on the static and dynamic behavior of rubberized concrete. Rubberized concrete specimens were prepared with different maximum rubber aggregate sizes ranging from 1 to 3 mm to 3 to 5 mm while the rubber content was kept constant at 15% by volume. The dynamic compressive behavior of rubberized concrete was investigated by using split Hopkinson pressure bar (SHPB) tests. The experimental results have shown that rubberized concrete with smaller rubber aggregates showed higher static compressive strength as compared to that with larger rubber aggregates. Meanwhile, the rubber aggregate size did not considerably affect the density of rubberized concrete. The use of smaller rubber aggregate size mitigated the slump reduction of rubberized concrete. Rubberized concrete exhibited obvious sensitivity to strain rate and those with larger rubber aggregates showed higher strain rate sensitivity. The progressive damage of rubberized concrete showed more ductile behavior with bulging failure, which was different from the typical concrete under compression. In general, the use of smaller rubber aggregate size was beneficial to the static compressive strength but less effective to the dynamic compressive strength of rubberized concrete as compared to those with larger rubber aggregates.

This paper proposes using neutral axis locations to monitor and quantify the prestress force in post-tensioned precast segmental beams. Strain measurements are used to obtain the neutral axis locations of specific cross-sections of the precast prestressed segmental beams, based on the plane–remains–plane and linear strain distribution assumption. A theoretical calculation method based on the static equilibrium of a specific cross-section is developed to calculate the prestress force in segmental beams based on the neutral axis location. To verify the accuracy of the proposed method, a post-tensioned prestressed segmental beam is built and tested in the laboratory. A corresponding high-fidelity finite element model is also developed based on the beam design and material properties. Experimental studies and numerical simulations are conducted to verify the feasibility and accuracy of the proposed method in quantifying the prestress force in precast segmental beams. Both experimental and numerical results demonstrate that the proposed method can reliably estimate the prestress force, which can be used to monitor the prestress force loss in post-tensioned structures.

Membrane actions commonly exist in reinforced concrete (RC) elements under flexural deformation, which could significantly increase the ultimate flexural load-bearing capacity and potentially influence the damage mode of the RC element. Most design codes only treat membrane actions as a “hidden” safety factor without considering its influence on the resistance functions and failure modes. In this paper, an experimental investigation is conducted to study the membrane actions on the resistance behaviors of restrained RC beams. It is found that compressive membrane effect occurred at early stage of a fully restrained RC beam, which leads to amplified flexural bending resistance capacity. Diagonal shear crack is developed since the designed shear resistance is lower than the amplified flexural bending capacity. Under membrane actions, the damaged beam with shear crack could still carry the imposed load and develop further tensile membrane action until eventual failure. The resistance function of the restrained beam under combined membrane and shear damage is significantly altered as compared to the un-restrained reference beam that failed in flexural bending. A modified theoretical resistance function is proposed to consider both the membrane effects and diagonal shear damage. Comparison with testing data shows that the proposed model could accurately describe the resistance of fully restrained RC beams under combined shear and membrane actions., Membrane actions commonly exist in reinforced concrete (RC) elements under flexural deformation, which could significantly increase the ultimate flexural load-bearing capacity and potentially influence the damage mode of the RC element. Most design codes only treat membrane actions as a “hidden” safety factor without considering its influence on the resistance functions and failure modes. In this paper, an experimental investigation is conducted to study the membrane actions on the resistance behaviors of restrained RC beams. It is found that compressive membrane effect occurred at early stage of a fully restrained RC beam, which leads to amplified flexural bending resistance capacity. Diagonal shear crack is developed since the designed shear resistance is lower than the amplified flexural bending capacity. Under membrane actions, the damaged beam with shear crack could still carry the imposed load and develop further tensile membrane action until eventual failure. The resistance function of the restrained beam under combined membrane and shear damage is significantly altered as compared to the un-restrained reference beam that failed in flexural bending. A modified theoretical resistance function is proposed to consider both the membrane effects and diagonal shear damage. Comparison with testing data shows that the proposed model could accurately describe the resistance of fully restrained RC beams under combined shear and membrane actions.

In this study, two new types of geopolymer composite lightweight sandwich panels are developed for prefabricated buildings. The first one has Fiber-reinforced Geopolymer (FRG) composite skin layers and polyurethane (PUR) foam core, and the second one is based on the first panel but strengthened with Basalt fiber reinforced polymer sheet (BFRP). Experimental studies are conducted to investigate the structural behavior and vibration characteristics of these panels. The failure mechanisms and capacity of the developed lightweight sandwich panels under flexural and compressive loads are studied by experimental quasi-static tests. Experimental results from flexural and compressive loading tests match well those from analytical calculations. The experimental studies show that the lightweight sandwich panel has a competitive capacity for prefabricated buildings. The vibration characteristics of the developed lightweight sandwich panels are obtained by hammer impact vibration tests. The finite element models are developed to predict the vibration characteristics of the tested sandwich panels. The obtained natural frequencies and mode shapes from numerical analysis and experimental tests show that the developed finite element models can be used to predict the vibration characteristics of geopolymer composite lightweight sandwich panels accurately. The addition of BFRP sheet does not significantly change the vibration characteristics of the panels, but changes the failure mode of the developed sandwich panel from skin tension failure to PUR foam core shear failure.

Mortar-less construction with interlocking bricks has many advantages, such as improved construction efficiency and relatively low requirements on labour skills. Nevertheless, the seismic performance of interlocking brick structures is not well understood yet. In this paper, laboratory tests and numerical modelling are carried out to investigate the seismic behaviour of interlocking brick walls. Laboratory shaking table tests are performed on a scaled reinforced mortar-less interlocking brick wall. The response and damage modes under in-plane seismic loading are investigated. A detailed numerical model is then generated and validated with the laboratory testing data. Unlike the conventional masonry wall that diagonal shear damage governs the failure, the interlocking brick wall exhibits rocking responses, whose damage is mainly at the two bottom corners of the wall. Full-scale interlocking brick walls are then modelled and compared with conventional concrete masonry unit (CMU) walls bonded by mortar. Comparisons are made between the seismic resistances and damage modes of the two walls. The influences of ground motion intensities, vertical components of seismic excitations and different seismic time histories on the seismic behaviour of the interlocking brick wall are examined. It is found that the interlocking brick wall has a higher seismic resistance capacity than the conventional CMU wall. Inter-brick friction is the main energy dissipation mechanism in the interlocking brick wall. Because of the rocking response, vertical component of the ground motion significantly influences the damage of interlocking brick wall. The interlocking brick wall is insensitive to velocity pulses of ground motions due to its relatively high natural frequency.

Compared to ordinary Portland cement-based concrete (OPC), geopolymer concrete (GPC) is an environmental-friendly construction material because it is mixed by replacing Portland cement with industry wastes such as fly ash. Despite intensive researches in the last two decades, application of geopolymer concrete in construction is still rather limited. One of the reasons is the quasi-static and dynamic material properties of geopolymer concrete, which are different from those of ordinary Portland-cement concrete, are not well defined yet, and the available design guides for geopolymer concrete structures are very limited. The existing design guides and dynamic constitutive models for OPC cannot be directly employed in design analysis and numerical modelling of GPC structures subjected to blast and impact loads. This paper first summaries the available dynamic material testing data on GPC, compares them with the widely used dynamic constitutive models for OPC, and discusses the suitability of those models for modelling GPC structures. Then, based on the available GPC material testing data, new material constants for strength model, equation of state and dynamic increase factors are derived for GPC. Finally numerical modellings are carried out using these material models with modifications for GPC material to examine their accuracies in simulating the dynamic responses and damages of structural components made of GPC subjected to blast and impact loads.

Membrane actions commonly present in reinforced concrete elements as a result of restrained boundary conditions and geometry of deformations, which could substantially improve the ultimate flexural load-resistance as compared to that using yield line theory. Nevertheless, most current design manuals do not consider membrane effect because of a short of proper analysis method. This paper proposed an improved resistance model for RC (reinforced concrete) elements which considers both compressive and tensile membrane actions. Firstly, the derivation of the proposed membrane model was presented in detail. It was then validated with available testing data, in which good agreement was found on the load-deflection relationship of RC element between the estimation using the proposed model and testing data. Combining with the equivalent SDOF (single-degree-of-freedom) analysis method, the dynamic responses of structural elements subjected to blast loads could be more accurately predicted as compared to the common elastic-perfectly-plastic resistance assumption in design guides. The proposed method was further verified with existing field blast testing results. Parametric studies were then carried out to examine the influences of critical design parameters for membrane behaviors including reinforcement ratio, span-to-depth ratio, and restraint stiffness. Last but not the least, based on the proposed analytical method a series of diagrams for modifying the design loading capacity estimated by UFC (Unified Facilities Criteria) design guides without considering the membrane effects were derived for more accurate and easy predictions of loading capacities in engineering applications.

A novel Kirigami modified corrugated core was proposed recently and its superior crushing performance under static loading was demonstrated. The proposed core is modified from the conventional corrugated core using Kirigami design, where a portion of the corrugated sheet is cut and then folded vertically. The vertical fold-ins of Kirigami modified corrugated core provide extra support and constraints to the adjacent un-folded cell walls, which increase the crushing resistance of a unit cell up to 10 times as previously studied. However, for a panel with multiple unit cells, its longitudinal flexural stiffness and impact resistance could be affected because of the fold-ins. This study investigates its performance and energy absorption under dynamic crushing through pendulum impact tests. Four configurations of panels, including laminated flat plate (FL), conventional corrugated (CC), Kirigami modified corrugated 1 (KC1) and Kirigami modified corrugated 2 (KC2) were tested. Different impact mass, velocities as well as impacting locations were considered. Impact force and rear face centre deflection were measured and compared to evaluate the impact performance of the panels. Superior impact resistance was demonstrated for proposed KC panel over CC panel under all impact scenarios.

A novel Kirigami (cut and fold) modified honeycomb structure is proposed in this study, aiming to reduce the initial peak force under out-of-plane crushing while maintaining the high energy absorption capacity, as well as increasing the in-plane crushing resistance. Three aluminium hexagonal honeycomb structures: standard honeycomb (HC), sheet reinforced honeycomb (RHC), and Kirigami modified honeycomb (KHC) structures are prepared and tested under quasi-static compression in three axial directions. The compressive properties of the proposed Kirigami modified honeycomb are compared with standard honeycomb and reinforced honeycomb in three axial directions. Numerical method is employed to adjust the wall thickness of HC so that its relative density is the same as RHC and KHC for fair comparisons on the crushing performances. Numerical model of standard honeycomb (HC) is calibrated and updated with the adjusted wall thickness to compare with the test results of reinforced and Kirigami modified honeycomb structures of the same relative density. The KHC demonstrated significant improvement on energy absorption capability as compared to the other two honeycombs in all three axial directions. Under out-of-plane crushing, KHC does not develop an initial peak force, while its average crushing resistance remains at a similar level as RHC, and is 17.6% higher than that of HC. Under the in-plane 1 compression, the average crushing resistance of KHC is around 5.2 and 7.5 times of that of HC and RHC, with an even lower uniformity ratio. The KHC shows a moderate improvement in crushing resistance in in-plane 2 direction, compared with the other two honeycombs. These results demonstrate the significant improvement of Kirigami modification on the crushing performance of honeycomb structures.

This study evaluates the performances of beam-column joints made of geopolymer concrete (GPC). A new dry joint type made of GPC and carbon fibre reinforced polymer (CFRP) bolts was proposed for moment-resisting concrete frames under earthquake loadings. Cyclic loading was applied to test the four specimens which were preparatorily cast by ordinary portland concrete (OPC) and GPC. Compared to monolithic joints, the proposed dry joints showed better performances in the maximum load-carrying and energy dissipation capacity. Additionally, new analytical models to design GPC monolithic and GPC precast joints are proposed. These models well predict the peak loads, main failure modes, failure positions, and horizontal shear strength with a minor variation of 1.3%. The application of GPC promises to effectively recycle a large amount of industrial wastes. Furthermore, the proper design made sure the CFRP bolts survive during the test without brittle failure and shear failure. Therefore, they could be potentially applied in the proposed dry joint to well resolve the corrosive issues in conventional precast joints, as well as satisfying the requirements for construction in sesmic regions.

An origami metamaterial with two-stage programmable compressive strength is proposed by combining the stacked Miura-origami and rhombic honeycomb structure. By adjusting the geometries of the structure, the compressive response of each stage including the compressive strength and the densification strain can be programmed within a certain range. Furthermore, the initial peak force, as an undesired energy-absorbing characteristic, can be programmed to maintain at a low level. The commonly seen fluctuation of crushing resistance on honeycomb structure is also minimized during the second stage deformation. The crushing behaviour of origami metamaterial is investigated under quasi-static loading condition. The programmability of compressive properties is demonstrated for the two stages of the deformation. The analytical model of the two-stage compressive response of the proposed origami metamaterial is firstly developed with friction contribution being taking into consideration during the first deformation stage. The analytical model is then verified with numerical analysis and quasi-static compressive testing data. The programmability of its compressive properties such as the initial peak crushing resistance, mean crushing force for both stages of deformation are then analysed based on the verified analytical model.

This study proposes an analytically unprecedented model of a meta-lattice truss with local resonators to generate a broader low-frequency bandgap. By leveraging the mass–spring model, a new equivalent meta-unit cell considering the elastic shear springs is developed to accurately predict the performance of the meta-lattice truss in suppressing stress wave propagations. Theoretical analyses and numerical simulations are conducted to examine the effectiveness of the proposed model. Sensitivity analyses are also performed to investigate the influences of masses and spring parameters on the bandgap characteristics of the meta-lattice truss. Based on the theoretical prediction, the system transmission coefficient is utilized to examine the transmissibility effect among the resonators. A three-dimensional finite element model of meta-lattice truss is also built and its accuracy in predicting the stress wave propagations is verified against the analytical predictions. The structural responses in the time domain and time–frequency domain demonstrate the superiority of meta-lattice truss in suppression of wave transmission as compared to that predicted by the conventional counterparts.

Designing protective reinforced concrete (RC) beams against impact loadings is a challenging task. It requires a comprehensive understanding of the structural response of RC beams subjected to impact loads. Significant research efforts have been spent to unveil the impact response of RC beams by using analytical models, experimental testing, or numerical investigations. However, these studies used various assumptions in the analytical derivations and different test setups in the impact testing, which led to significantly different responses and observations of similar structures and similar loading conditions. For example, a minor change in contact surface can triple the maximum impact force of identical RC beams. This study provides a review of the contemporary understandings of the RC beam responses to impact loads, and explains the different observations and conclusions. Some unsolved issues for protective structures, that is, RC beams to resist impulsive loads are also discussed. It is suggested that future studies should take into consideration the conditions of the test setup, simplifications and assumptions made in analytical derivations for better interpretations of the obtained results.

A dual-meta panel functioning as a sacrificial cladding is proposed and its blast mitigation capacity is investigated in this study. The proposed panel possesses the potential to generate bandgaps that target at a specific range of frequencies to stop stress wave propagating through the panel, leading to the favourable stress wave mitigation for structural protection. Aside from the unique stress wave manipulation capability, more energy can be absorbed by a combination of plastic deformation and local resonance. The effectiveness of the proposed panel is validated through numerical simulations. An analytical solution of wave propagation in an ideal meta truss bar is derived to validate the numerical model with good agreement. It is found that the proposed dual-meta panel exhibits an increase in energy absorption, a reduction in transmitted reaction force (up to 30%), and the back plate central displacements (up to 20%) compared to other conventional sandwich panels, e.g. sandwich panel with hollow trusses and solid trusses, in resisting blast loadings. In pursuit of optimizing the performance of the proposed panel, parametric investigations are also conducted to examine the influences of the plate thickness, boundary condition, and the blast load profiles including duration and intensity on the transient response of the proposed dual-meta panel.

Spalling is a typical tensile fracture phenomenon due to insufficient tensile strength of concrete. Concrete structure might experience severe spall damage at the rear surface of the structure owing to reflected tensile stress wave induced by impulsive load. In recent years, metaconcrete consisting of engineered aggregates has attracted attentions as metaconcrete exhibits extraordinary wave-filtering characteristics. Metaconcrete can be used to attenuate stress wave generated by impulsive load and hence possibly mitigate the spall damage. In this study, engineered aggregate is designed via the software COMSOL to have the frequency bandgap coincide with the dominant frequency band of stress wave propagating in the normal concrete (NC) specimen to reduce the stress wave propagation and hence spall damage. The wave propagation behaviors in metaconcrete specimen with periodically distributed engineered aggregates have been investigated in a previous study. This study establishes 3D meso-scale model of metaconcrete including mortar, randomly distributed natural aggregates and engineered aggregates to simulate spall behaviors of metaconcrete via the software LS-DYNA. The responses of metaconcrete composed of engineered aggregates with single bandgap and multiple bandgaps are studied. The results show that stress wave can be more effectively attenuated by using engineered aggregates with multiple bandgaps. It is found that although engineered aggregates mitigate stress wave propagation, the soft coating of the engineered aggregates reduces the concrete material strength, therefore spall damage of metaconcrete specimen is not necessarily less severe than the normal concrete, but has different damage mode. In addition, the influences of loading intensity and duration on stress wave, as well as the spall behaviors of metaconcrete specimen are also studied.

This is the first study in the literature which experimentally and numerically investigates the impact behavior of concrete columns reinforced with fiber-reinforced polymer (FRP) reinforcements. The effect of concrete strength (50 MPa vs 100 MPa) and longitudinal FRP ratio on the lateral impact response of the columns was investigated. The experimental results showed that the longitudinal reinforcement ratio strongly affected the failure modes and impact-resistant capacity while the use of high strength concrete (HSC) did not effectively improve the performance of the columns, which on the contrary, might have caused spalling failure due to its brittleness. The peak impact force and displacement of the columns increased linearly with the impact velocity up to their maximum capacity. The longitudinal reinforcement ratio slightly affected the peak impact forces while the concrete strength showed marginal variation. The use of HSC did not effectively reduce the maximum displacement of the columns. The energy absorption of the columns and the impact velocity exhibited an approximately linear relationship regardless of the reinforcement ratio and concrete strength. Different from the static case, the numerical results show three critical sections, i.e. at the impact location and column ends, which need to be carefully designed.

The impact response of reinforced concrete (RC) beams has been intensively investigated by impact tests with various setups. Given the same impact energy, different setups of drop-weight impact tests might lead to different measurements and observations of identical RC beams including the impact force, reaction force and displacement, implying the obtained impact test results depend on not only the impact energy and structure itself, but also the test setups. Therefore, it is essential to understand the measurement accuracy, reliability, and controllability of drop-weight impact tests for a successful impact test design and interpretation of test results on RC beams. This study examines the effects of various test setups and critical factors on the impact response of RC beams. Recommendations for the processing and interpretation of test results with respect to the configuration of the test setup, including the location of load cells, mass and shape of the impact head, interlayer, and boundary condition are made for drop-weight tests. The mechanism of the negative reaction force often observed in impact tests has been unveiled for a better understanding of the impact problem.

High Volume Fly Ash (HVFA) concrete enables the utilization of fly ash (FA) to diminish greenhouse gas emission by decreasing the demand of ordinary Portland cement. Structures made of HVFA concrete, such as roadside barriers, tunnel cushions and building walls could be subjected to impact and blast loads during service life. Thus, dynamic performance of HVFA concrete is worthy of investigating for better analysis and design of concrete structures. This paper presents the quasi-static and dynamic properties of HVFA concrete containing FA contents of 40 and 60% (by wt.) as partial replacement of cement. The effect of 2% (by wt.) nano silica (NS) on the quasi-static and dynamic properties of HVFA concrete is also studied. The dynamic compressive tests are carried out by using a split Hopkinson pressure bar (SHPB) with 100 mm diameter. The failure processes and patterns as well as stress–strain curves of plain and HVFA concretes under different strain rates are compared. The strain rate effects on the compressive strength, modulus of elasticity and energy absorption capacities are analysed. The experimental results show that quasi-static and dynamic performances of HVFA concrete are enhanced by the addition of NS. With the increase of FA content, the damage level becomes more severe, and modulus of elasticity and energy absorption capacities of HVFA concretes become lower at the similar strain rate. Dynamic increase factors (DIF) of compressive strength for HVFA concretes are quantified and compared with the empirical formulae recommended by Euro-International Committee for Concrete (CEB) for normal concrete. Adding NS leads to lower DIF for compressive strength of HVFA concrete. Empirical formulae for DIF of compressive strength, modulus of elasticity and energy absorption capacity of HVFA concretes with and without nano silica as a function of strain rate are proposed. It is worth noting that the NS modified HVFA C60F38N2 in this study has higher compressive strength

Impact force and structural response of reinforced concrete (RC) beams under drop weight impact have been intensively studied and reported in the literature. The prediction of the peak impact force has been well investigated while the study of the overall impact force profile governing the structural response is limited. The impact force parameters acting on a structure including the peak impact force, plateau force, and impact duration all affect the structural responses. This study investigates the impact force profiles from drop weight impact on RC beams. The effects of global stiffness (by changing the beam span and boundary condition) on the impact force profile are numerically studied by using LS-DYNA. A two-degree-of-freedom (2DOF) analytical model is developed for RC beams under drop weight impact by using fiber beam section analysis method to predict the impact force. The developed 2DOF analytical model is validated by drop weight impact test results. With the validated analytical model, a simplified model of impact force profile is then proposed by determining six characteristic points, which are expressed by empirical equations fitted by the analytical parametric study results. The simplified impact force profile predicted by the empirical equations shows a good agreement with the test data.

This study investigates the performance of monolithic and newly proposed dry beam-column joints using GFRP bolts, GFRP reinforcements, and different types of fibres subjected to pendulum impact. Six specimens were cast and tested with increasing impact velocity until failure. The experimental results have shown that the proposed concrete dry joint reinforced with fibres and GFRP bars showed better behaviour in terms of energy dissipation (up to 51%), reduced damage level, and reduced maximum and residual displacement as compared to the monolithic joint with GFRP reinforcements. The test results suggested that steel bolts and steel reinforcements could be effectively replaced by GFRP bolts and GFRP reinforcements to mitigate the corrosion problem while still satisfy the design requirements for beam-column joints in both strength and ductility. Furthermore, the use of steel fibres (StFs) demonstrated impressive performance in the critical indices such as damage level and displacement at high impact energies, compared to synthetic fibres (SyFs). Meanwhile, the application of SyFs led to greater energy dissipation than that of StFs (between 6 and 30%). The proposed dry joints could be potentially applied in practice to reduce the construction costs and the damaged/deteriorated components would be easily replaced.

The application of fiber-reinforced-polymer (FRP) bars to reinforce concrete structures could mitigate the corrosion-induced damage of steel reinforcements. No study has been reported in open literature on flexure-critical or shear-critical concrete beams reinforced with Basalt FRP (BFRP) bars under impact loads. In this study, six BFRP bars reinforced concrete beams were tested under quasi-static and impact loads. The test results showed the flexure-critical beams experienced the failure mode changing from flexure-governed under quasi-static loads to flexure-shear combined under impact loads. The shear-critical beams still failed in diagonal shear under impact loads, but experienced severer concrete spalling and more critical diagonal cracks on both sides of the beams. The impact performance of concrete beams with higher strength concrete may not be necessarily superior to that of beams with normal strength concrete due to the increased brittleness. Moreover, a numerical model of the tested beams under impact loads was developed and calibrated in LS-DYNA. Numerical results showed increasing tension reinforcement ratio could change the failure mode from flexure-governed to flexure-shear combined along with the reduced maximum midspan deflection. The BFRP bars reinforced concrete beams had comparable impact resistant performance with the conventional steel reinforced concrete beams

The use of fiber reinforced polymer (FRP) bars in GeoPolymer Concrete (GPC) structures has drawn increasing attention in recent years. The application of GPC with basalt fiber reinforced polymer (BFRP) reinforcements in replacing Ordinary Portland cement Concrete (OPC) and steel reinforcements leads to green and sustainable constructions. Currently, very limited studies have been conducted to investigate the performance of GPC beams reinforced with BFRP bars under static loads, but no study on their performance under impact loads has been reported yet in open literature. In this study, ambient-cured GPC beams reinforced with BFRP bars were designed, cast and tested under static and impact loads. The damage mode and quantitative results such as midspan deflection, reinforcement strain, and impact and reaction forces were recorded and analysed. Test results showed that spiral stirrups led to superior performance of the beams under both static and impact loads as compared to conventional rectangular stirrups. The commonly used concrete material model *Mat_072R3 in LS-DYNA was modified based on test data to model GPC material. With the modified GPC material model, numerical models were developed and calibrated against the impact test results. Parametric studies were carried out to investigate the influences of GPC material strength and longitudinal and stirrup reinforcement ratios on the performance of beams subjected to impact loads. It was also found that using steel bars as the compression reinforcements led to better performance because BFRP bars under shear and compression were vulnerable to splitting damage subjected to impact loads.

The applications of GeoPolymer Concrete (GPC) with basalt-fiber-reinforced-polymer (BFRP) reinforcements could be alternative for conventional structural designs with Portland Cement Concrete reinforced with steel bars for green and sustainable constructions. Very limited studies, however, have been carried out to investigate the performance of GPC beams reinforced with BFRP bars subjected to static loads, and no study of their performance under impact load is available in open literature yet. In this study, ambient-cured GPC beams reinforced with BFRP bars were tested under static and impact loads. Their damage modes, static and dynamic responses were recorded and analysed. The test results showed that the beams experienced flexural failure mode under static load while combined flexure-shear failure mode was observed under impact load. The impact-loading tested beams were further statically loaded to examine their residual capacities. Additionally, numerical models of the tested GPC beams were developed adopting the commonly used concrete material model *Mat_072R3 (KCC model) in LS-DYNA with modified parameters based on the GPC material testing data. The calibrated numerical model was used for parametric simulations. The results showed that with the increased impact velocity, failure mode of the beam shifted from the flexure-governed to punching-shear-governed along with the rupture of longitudinal BFRP bars.

In analysis and design of structures subjected to blast loading, equivalent Single-Degree-of-Freedom (SDOF) method is commonly recommended in design guides. In this paper, improved analysis method based on SDOF models is proposed. Both flexural and direct shear behaviors of structures subjected to blast load are studied using equivalent SDOF systems. Methods of deriving flexural and direct shear resistance functions are introduced, of which strain hardening and softening effects are considered. To collocate with the improved SDOF models, the improved design charts accounting for strain hardening and softening are developed through systematical analysis of SDOF systems. To demonstrate the effectiveness of the proposed analysis method, a model validation is made through comparing the predictions with laboratory shock tube testing results on reinforced concrete (RC) columns. It is found that compared to the conventional approach with elastic and elastic-perfectly-plastic model, the elastic-plastic-hardening model provides more accurate predictions. Additional non-dimensional design charts considering various levels of elastic-plastic-hardening/softening resistance functions are developed to supplement those available in the design guides with elastic-perfectly-plastic resistance function only, which provide engineers with options to choose more appropriate resistance functions in design analysis.

For the topological diversity, in-plane hexagonal honeycombs show some interesting mechanical properties which can be related to Poisson's ratios. This work trying to understand how Poisson's ratios affects the crashworthiness of in-plane honeycombs. Based on the standard beam theory, the analytical model that predicting Poisson's ratios is derived, from which the crushing strength in terms of Poisson's ratios is further proposed by using one-dimensional shock model. Combining the analytical and numerical method, Poisson's ratios on the critical crushing characteristics as plateau stress, densified strain, Specific Energy Absorption (SEA) has been investigated under crushing speeds range from 5 m/s to 150 m/s which is complied with previous study about in-plane honeycomb crashworthiness. Through observing the wave trapping behavior of honeycombs, some typical deformation modes have been identified and a deformation-mode map is generated by considering critical wave trapping speeds and Poisson's ratio.

Road tunnels are critical components in road transportation networks. In their service life they may subject to explosion loads from terrorist bombing attacks, engineering blasting for construction and accidental explosions from transported flammable goods. These extreme loading conditions might not only lead to catastrophic damages to tunnel structures, severe casualties and economic losses, but also have immeasurable social impacts. Therefore, it is imperative for engineers, researchers and policy regulators to understand the performance of road tunnels under explosion loads towards a reliable blast-resistant design of tunnel structures. This paper presents a state-of-the-art review of dynamic response, damage assessment and damage mitigation of tunnels under blast loads. The common road tunnels, various explosion scenarios, and the corresponding blast wave characteristics are reviewed first. Then the dynamic response and damage characteristics of tunnel structures under blast loads including the analysis methods of tunnel response, types of tunnel response and key factors influencing tunnel response are reviewed and discussed. The assessment criteria of tunnel damage and the damage mitigation measures for tunnels against blast loads are also reviewed. Finally, concluding remarks and several key research areas for future work are presented.

Metaconcrete is made by partially or fully replacing natural coarse aggregates (NA) in normal concrete (NC) with engineered aggregates (EA). Normal engineered aggregate (NEA) is made by wrapping elastic coating outside spherical heavy core. It was found that mixing NEA in concrete could effectively mitigate stress wave propagation in metaconcrete structure owing to the local resonance of the heavy core of NEA. However, it also reduced the concrete material stiffness and strength because of the low modulus of soft coating that led to relatively large deformation of mortar matrix under loading. To address the issue of low interface stiffness while maintain the local vibration ability of NEA, new enhanced engineered aggregate (EEA) is proposed by placing an additional enhanced coating layer outside the soft coating of NEA. In this study, three types of EEA aggregates composed of three enhanced coating layer materials (i.e., epoxy resin, steel, ultra-high performance concrete UHPC) are considered and their configurations are designed via the software COMSOL. The spall behaviors of enhanced metaconcrete (EMC) mixed with EEA aggregates are examined though numerical simulations. 3D mesoscale models of EMC composed of mortar, randomly distributed natural aggregates and EEA aggregates are built via the software LS-DYNA. The distinction between the bandgap characteristics of NEA and EEA is studied. The effects of enhanced coating layer material on the bandgap of EEA and the performance of EMC with respect to energy absorption capacity, wave attenuation characteristics, and spall strength are studied. The results show that the existence of enhanced coating layer slightly affects the bandgap characteristics of engineered aggregate. Applying an additional stiffer coating layer to make the EEA aggregates can improve the spall strength of metaconcrete mixed with EEA aggregates while its ability in mitigating stress wave propagation and energy absorption is only slightly affected.

Intermediate crack (IC) debonding is a common failure mode of externally bonded (EB) FRP-strengthened RC beams. This debonding failure initiates at an intermediate crack and propagates towards a plate end. New epoxy anchor was proposed recently by the authors and has shown its effectiveness in enhancing interfacial bonding behaviour and therefore it might be effective to delay or suppress IC debonding failure in RC beams. This study is to experimentally investigate the efficiency of using epoxy anchors for mitigating the IC debonding under three-point bending tests. The application of the new proposed epoxy anchors has advantage of simple installation procedure including pre-drilling holes and then bonding FRP. Totally, five RC beams including one control specimen and four anchored ones were tested. Damage modes and structural response of unanchored and anchored RC beams were evaluated and discussed. The effects of various configurations of epoxy anchors were analysed and discussed. The experimental results show that the load-carrying capacity and the ductility of anchored beams increased by up to 13.12% and 53.31%, respectively, and the strain utilization of FRP can be significantly improved by 43.48% as compared to the control specimen.