المؤلفون: Liang Li, Zichen Wang, Jun Wu, Xiuli Du, Hongwei Wang, Wenli Liu

المصدر: Case Studies in Construction Materials, Vol 20, Iss , Pp e02778- (2024)

مصطلحات موضوعية: Steel Fiber Reinforced Concrete (SRFC), Dynamic compressive performance, Split Hopkinson Pressure Bar (SHPB), Natural cooling after high temperatures, Dynamic Increase Factor (DIF), Materials of engineering and construction. Mechanics of materials, TA401-492

الوصف: The dynamic properties of concrete structures after being exposed to high temperatures play a crucial role in post-disaster repair and accident prevention measures. This study examined three different mixture ratios of Steel Fiber Reinforced Concrete (SFRC) with matrix strength of C60 and steel fiber contents of 0%, 1%, and 2%. A Split Hopkinson Pressure Bar (SHPB) with a diameter of 75 mm, along with a heating furnace, was employed to comprehensively investigate the dynamic compression behavior of materials. The specimens were exposed to temperatures ranging from 200 °C to 600 °C. In addition to evaluating the extent of mechanical degradation in SFRC after cooling, auxiliary impact experiments were also carried out at ambient temperature. The experimental data revealed that the dynamic peak stress and peak strain initially increased but eventually decreased as the loading rates continued to rise. The degree of strengthening, toughening, and energy absorption capacity of concrete materials progressively decreased as the escalation of strain rate after the cooling process. Moreover, the inclusion of steel fibers proved effective in preventing cracking and damage to the concrete, preserving the integrity of specimens even at higher temperatures. Simultaneously, the residual stress and deformation capacity of SFRC showed considerable enhancement after exposure to elevated temperatures.

وصف الملف: electronic resource

العلاقة: http://www.sciencedirect.com/science/article/pii/S2214509523009592Test; https://doaj.org/toc/2214-5095Test

الوصول الحر: https://doaj.org/article/0be758eb8ac34563bebd2306e0496f9bTest

المؤلفون: Jianbo Guo, Hongfa Yu, Haiyan Ma, Sangchu Quan, Ting Liu, Xiaodi Dai

المصدر: Buildings, Vol 14, Iss 6, p 1605 (2024)

مصطلحات موضوعية: coral aggregate seawater concrete, Split Hopkinson Pressure Bar, toughness index, dynamic increase factor (DIF), three-dimensional mesoscale model, aggregate volume ratio, Building construction, TH1-9745

الوصف: This paper comprehensively investigates the dynamic mechanical properties of concrete by employing a 75 mm diameter Split Hopkinson Pressure Bar (SHPB). To be detailed further, dynamic compression experiments are conducted on coral aggregate seawater concrete (CASC) to unveil the relationship between the toughness ratio, strain rate, and different strength grades. A three-dimensional random convex polyhedral aggregate mesoscopic model is also utilized to simulate the damage modes of concrete and its components under varying strain rates. Additionally, the impact of different aggregate volume rates on the damage modes of CASC is also studied. The results show that strain rate has a significant effect on CASC, and the strength grade influences both the damage mode and toughness index of the concrete. The growth rate of the toughness index exhibits a distinct change when the 28-day compressive strength of CASC ranges between 60 and 80 MPa, with three times an increment in the toughness index of high-strength CASC comparing to low-strength CASC undergoing high strain. The introduction of pre-peak and post-peak toughness highlights the lowest pre-to-post-peak toughness ratio at a strain rate of approximately 80 s−1, which indicates a shift in the concrete’s damage mode. Various damage modes of CASC are under dynamic impact and are consequently defined based on these findings. The LS-DYNA finite element software is employed to analyze the damage morphology of CASC at different strain rates, and the numerical simulation results align with the experimental observations. By comparing the numerical simulation results of different models with varying aggregate volume rates, it is reported that CASC’s failure mode is minimized at an aggregate volume rate of 20%.

وصف الملف: electronic resource

العلاقة: https://www.mdpi.com/2075-5309/14/6/1605Test; https://doaj.org/toc/2075-5309Test

الوصول الحر: https://doaj.org/article/cd32a052967349d09d2575247c59648eTest

المؤلفون: Weina Guo, Yupeng Tian, Jiuwen Bao, Bing Wang, Dongyi Lei, Peng Zhang, Yifei Cui

المصدر: Journal of Materials Research and Technology, Vol 24, Iss , Pp 8357-8372 (2023)

مصطلحات موضوعية: Freeze-thaw cycles, Dynamic increase factor (DIF), High-speed digital image correlation (DIC), X-ray CT imaging technique, Full-field strain distribution, Mining engineering. Metallurgy, TN1-997

الوصف: In this paper, the split Hopkinson pressure bar (SHPB) test was used to investigate the variation of dynamic compressive properties of SHCC with various freeze-thaw (FT) cycles and strain rates. The full-field strain distribution and cracking characteristics of FT-damaged SHCC after the SHPB test were quantitatively and characterized by the high-speed digital image correlation (DIC) technique. The internal damage was analyzed using an X-ray CT imaging technique and SEM (Scanning electron microscope). Results show that dynamic compressive strength, energy absorption ability and dynamic increase factor (DIF) increase as the increase of strain rate, and these increase trends are weakened by the FT damage. The DIF model is established considering the number of FT cycles and strain rates. Variation of crack width in SHCC obtained through the high-speed DIC technique can be divided into three stages: linear increase stage, plateau stage and slow increase stage.

وصف الملف: electronic resource

العلاقة: http://www.sciencedirect.com/science/article/pii/S2238785423010712Test; https://doaj.org/toc/2238-7854Test

الوصول الحر: https://doaj.org/article/7738845f6bb74fc08e0fd53bd02696c2Test

المؤلفون: Tao Yang, Zhongqing Han, Nianchun Deng, Wanqing Chen

المصدر: Applied Sciences; Volume 9; Issue 20; Pages: 4436

مصطلحات موضوعية: Progressive collapse, basalt fiber reinforced polymer (BFRP), dynamic increase factor (DIF), prestressed concrete

جغرافية الموضوع: agris

الوصف: Six concrete beam-column frame sub-assemblages reinforced with basalt fiber-reinforced polymer (BFRP) bars in the frame beams were designed to investigate the collapse resistance after a middle column removal. Effect of parameters, including span to depth ratio of frame beams, prestressing, as well as material types of stirrups in the beams, on the collapse resistance of the sub-assemblages, was investigated. Experimental results showed that the initial stiffness of the frame beams was apparently lower due to low elastic modulus of BFRP bars. The collapse resistance of the sub-assemblages presented wave-like increasing tendency with the vertical displacement of the failed middle column, and it mainly attributed to the cracking or crushing of concrete and rupture of BFRP bars in the frame beams. Top longitudinal BFRP bars at the beam ends near to the side column (BESCs) and bottom longitudinal BFRP bars at the beam ends near to the middle column (BEMCs) kept tensile during the loading process, which played an important role in resisting structural collapse. Adjacent structural members such as frame beams and columns could provide horizontal reaction forces to constrain the free deformation of the residual sub-assemblages after the middle column failed, and it was beneficial to mitigate the structural collapse risk. The vertical deformation of the frame beams was nearly linear and proportional to the vertical displacement of the failed middle column. Finally, the dynamic increase factor (DIF) of collapse load was discussed using energy conservation method, and a calculation method of DIF for prestressed concrete frame structures was developed. It was suggested that the DIF values for the non-prestressed frame structures reinforced with BFRP bars in the beams should be taken as 2.0, while those for the prestressed sub-assemblages can be taken between 1.44 and 2.0.

وصف الملف: application/pdf

العلاقة: Materials Science and Engineering; https://dx.doi.org/10.3390/app9204436Test

الإتاحة: https://doi.org/10.3390/app9204436Test

المؤلفون: Brkić, Doris

المساهمون: Draganić, Hrvoje, Kraus, Ivan, Miličević, Ivana

مصطلحات موضوعية: displacement, macro model, exsplosion, dynamic increase factor (DIF), columns, overpasses

الوصف: Opterećenje konstrukcije eksplozijom može dovesti do katastrofalnih posljedica. Potencijalne mete napada eksplozivom upravo su mostovi, čije uništenje dovodi do odsijecanja određenih područja neke države. Način na koji se takve štete pokušavaju ublažiti je da se pri proračunu mostova uzme u obzir izvanrednog opterećenja uzrokovanog eksplozijom. Na temelju odabranog nadvožnjaka izrađen je štapni model pomoću kojega su određeni pomaci pod utjecajem izvanrednog opterećenja.
Explosions of structures can lead to catastrophic consequences. The most common targets of explosive attacks are bridges, the destruction of which leads to the cutting off of certain points of a country. Such damages can be avoided by trying to mitigate them by taking into account the original load caused by the explosion in the calculation. A beam model was created according to the selected overpass, which determined the displacements under the influence of the extream load.

وصف الملف: application/pdf

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=od______3759::c9bd0526ca08505ff7aefb69a424683cTest
https://urn.nsk.hr/urn:nbn:hr:133:824975Test

المؤلفون: Cheng, Xinyi

مصطلحات موضوعية: Laminated veneer lumber (LVL), Mass timber building, Dynamic increase factor (DIF)

الوصف: Mass timber mid-rise to tall buildings are gaining international popularity owing to their lower global carbon emissions, fast erection and more aesthetically pleasing than traditional concrete and steel structures. Given the increasing height of mass timber buildings, up to 85.4 m currently, the consequences of a progressive collapse event of such building can be catastrophic. In Australia, mass timber buildings must be designed to resist progressive collapse according to National Construction Code (NCC). Moreover, a progressive collapse event is essentially dynamic and nonlinear. Dynamic effects therefore need to be taken into considerations. Since the actual dynamic analysis of a structure can be complicated, it can be also achieved by applying a dynamic increase factor (DIF) to a quasi-static response, which is a theoretical upper value of 2.0 obtained from elastic system, instead of the well-developed values in concrete and steel structures. Therefore, in this study, scaled-down dynamic experimental studies on 2-bay post-and-beam mass timber frames were carried out to fill the gap in this knowledge and gain a preliminary understanding of the dynamic behaviour of such structural system. It was found that experimental DIF values were dependent on the types of connections and their failure modes. Ductile connections tended to exhibit lower DIF values. Such DIF values are critical to progressive collapse prevention designs. Based on the previous experimental study on the structural behaviour of a mass timber frame in a global scale, it can be concluded that connections are the key, which therefore is the next focus in this study. Timber connections are often manufactured from a combination of multiple materials including timber, steel and aluminium, which experience different degree of sensitivities under the same level of strain rate. Such differences may further result in different failure modes and load carrying capacities in strain rates encountered during dynamic events when compared to quasi-static strain rates. While strain rate effects on the materials properties of steel and common aluminium alloys have been well researched, for timber, it was mainly focused on the different between quasi-static (low strain rates, e.g., 10-5) and blast loadings (high to extremely high strain rates, e.g., 101) which are not applicable to earthquake events (medium strain rates). Therefore, in this study, in total 400 material tests on softwood LVL were conducted on critical timber mechanical properties, including embedding, tension perpendicular-to-grain, fracture model I and fracture mode II, to gain a better understanding of these material properties under the strain rate range equivalent to quasi-static and earthquake events. It was found that significant increase in stiffness and strengths in timber embedding, while no clear tendency in tension perpendicular-to-grain and fracture energies under low to medium strain rate range. To further investigate the timber connections, finite element model was chosen as an economical option. This study selected a commonly used commercial timber beam-to-column connection that contains most of the features in timber connections including steel bolts and dowels, and aluminium slotted in concealed bracket. In this study, static FE models were established first to ensure the reliability of the models, which were calibrated step by step against timber half-hole embedding, full hole push-down, full-scale connection shear and bending static tests. Then the material properties under medium strain rates were incorporated into the static FE model to study the influence of those material properties alone to structural behaviours of such timber connection. Based on the findings of this study, further 3D mass timber frame with CLT panels is recommended to further study the DIF values in complete mass timber systems. Furthermore, while the FE models developed in this study represents a first step towards understanding the behaviour of timber connection under dynamic loading, it needs to be applied to other connection types and validated against corresponding experimental results.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::bb2a9d9f3e7bce0381a874341454a33eTest

المؤلفون: Chen, Xing, Wang, Changzhong, Chen, Suwen, Yi, S., Lu, Yong

المصدر: Chen, X, Wang, C, Chen, S, Yi, S & Lu, Y 2023, ' Characterization of the dynamic mechanical properties of low-iron float glass through Split-Hopkinson-Pressure-Bar tests ', Construction and Building Materials, vol. 365, 130083, pp. 1-18 . https://doi.org/10.1016/j.conbuildmat.2022.130083Test

مصطلحات موضوعية: Dynamic mechanical property, Split-Hopkinson-Pressure-Bar (SHPB), Strain rate, Low-iron float glass (LIFG), General Materials Science, Building and Construction, Dynamic increase factor (DIF), Civil and Structural Engineering

الوصف: Low-iron ultra-clear float glass (LIFG) has been widely used in landmark and large-scale buildings in recent years due to its aesthetic characteristics. A better understanding of the dynamic mechanical properties of LIFG is essential for the blast resistance analysis and design of glass facades. This paper presents a series of quasi-static tests and dynamic tests (using Split-Hopkinson-Pressure-Bar) to study the dynamic compressive and tensile behavior of LIFG. Strain rate effect has been investigated on compressive strength in the range of 10 -5 s −1 to 10 3 s −1 and splitting tensile strength in the range of 10 -5 s −1 to 40 s −1. During the tests, an ultra-high-speed camera was employed to capture the crack initiation and propagation. The test results show that both the dynamic compressive and tensile strengths of LIFG are strain-rate dependent, nevertheless the dynamic tensile strength is more sensitive to strain rate than the compressive strength. The strain rate effect is insignificant on the Young's modulus of LIFG. In addition, the upper limits of strain rate are identified for dynamic compression and splitting tension of glass through SHPB facilities based on a conceptual analysis. For LIFG specimens with the length of 8 mm (for compression) or the diameter of 20 mm (for splitting tension), the upper limit of strain rate is about 2500 s −1 for compression and about 40 s −1 for splitting tension. Increasing or reducing the specimen dimension will correspondingly decrease or increase the upper strain rate limits.

وصف الملف: application/pdf

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::4fab5320f0bf9cee9e06d0815d939005Test
https://doi.org/10.1016/j.conbuildmat.2022.130083Test

المؤلفون: Pereira, João Miguel, Lourenço, Paulo B.

مصطلحات موضوعية: Masonry, Compression, Impact, Drop-weight, Strain rate, DIF, Dynamic increase factor (DIF), Engenharia e Tecnologia::Engenharia Civil, Science & Technology

الوصف: The strain rate effect influences the mechanical properties on most construction materials and its investigation is critical for structural engineering. Current materials such as steel or concrete have been intensively investigated. However, similar studies on the dynamic properties of masonry or masonry components such as clay brick or mortar are scares. This work intends to study the behavior of masonry and its usual components (clay brick and mortar) when subjected to high strain rates. A Drop Weight Impact Machine is used at different heights and weights introducing different levels of strain rate. Empirical relations of Dynamic Increase Factors (DIF) are derived from the experimental results and the strain rate effect on compressive strength, compressive fracture energy, strain at peak strength and Young’s modulus are determined and presented. ; This work was performed under Project CH-SECURE funded by the Portuguese Foundation of Science and Technology – FCT. The authors acknowledge the support. The first author also acknowledges the support from his PhD FCT grant with the reference SFRH/BD/45436/2008.

وصف الملف: application/pdf

العلاقة: info:eu-repo/grantAgreement/FCT/5876-PPCDTI/120118/PT; info:eu-repo/grantAgreement/FCT/COMPETE/120118/PT; info:eu-repo/grantAgreement/FCT/SFRH/SFRH%2FBD%2F45436%2F2008/PT; Pereira, J.M. & Lourenço, P.B. Journal of Materials in Civil Engineering (2017). doi:10.1061/(ASCE)MT.1943-5533.0001755; http://hdl.handle.net/1822/43623Test

الإتاحة: https://doi.org/10.1061Test/(ASCE)MT.1943-5533.0001755
http://hdl.handle.net/1822/43623Test

المؤلفون: Xiaoxin Zhang, Gonzalo Ruiz, Manuel Tarifa, David Cendón, Francisco Gálvez, Waleed Alhazmi

المصدر: Materials; Volume 10; Issue 11; Pages: 1270

مصطلحات موضوعية: steel fiber reinforced self-compacting concrete (SFRSCC), fiber content, drop-weight impact test, flexure, dynamic increase factor (DIF)

الوصف: Three-point bending tests on notched beams of three types of steel fiber-reinforced self-compacting concrete (SFRSCC) have been performed by using both a servo-hydraulic machine and a drop-weight impact instrument. The lo ading rates had a range of six orders of magnitude from 2.20 × 10−3 mm/s (quasi-static) to 2.66 × 103 mm/s. These SFRSCCs had the same matrix, but various types of steel fiber (straight and hooked-end) and contents (volume ratios), 0.51%, 0.77% and 1.23%, respectively. The results demonstrate that the fracture energy and the flexural strength increase as the loading rate increases. Moreover, such tendency is relatively moderate at low rates. However, at high rates it is accentuated. For the 0.51% fiber content, the dynamic increase factors of the flexural strength and the fracture energy are approximately 6 and 3, while for the 1.23% fiber content, they are around 4 and 2, respectively. Thus, the higher the fiber content the less rate sensitivity there is.

وصف الملف: application/pdf

العلاقة: https://dx.doi.org/10.3390/ma10111270Test

الإتاحة: https://doi.org/10.3390/ma10111270Test

المؤلفون: Huang, Z., Chen, Wensu, Hao, Hong, Aurelio, R., Li, Z., Pham, Thong

مصطلحات موضوعية: Science & Technology, Technology, Construction & Building Technology, Engineering, Civil, Materials Science, Multidisciplinary, Geopolymer concrete, Split Hopkinson pressure bar (SHPB), Compression, Splitting tension, Energy absorption, Dynamic increase factor (DIF), COMPRESSIVE STRENGTH ENHANCEMENT, FIBER-REINFORCED CONCRETE, ASH-BASED GEOPOLYMER, FLY-ASH, STRAIN-RATE, NUMERICAL-ANALYSIS, BEHAVIOR, WORKABILITY, PLAIN

الوصف: 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.

وصف الملف: fulltext

العلاقة: http://purl.org/au-research/grants/arc/FL180100196Test; http://hdl.handle.net/20.500.11937/91647Test

الإتاحة: https://doi.org/20.500.11937/91647Test
https://doi.org/10.1061Test/(ASCE)MT.1943-5533.0004074
https://hdl.handle.net/20.500.11937/91647Test