PSI - Issue 70

Available online at www.sciencedirect.com

ScienceDirect

Procedia Structural Integrity 70 (2025) 1–2

Structural Integrity and Interactions of Materials in Civil Engineering Structures (SIIMCES-2025) Preface – SIIMCES2025 R. Mohanraj a, *, Abhay Kumar Chaubey a , S. A. Krishnan b,c , Ubagaram Johnson Alengaram d a Civil Engineering, Faculty of Engineering and Technology, SRM University, Delhi-NCR, Sonepat, Haryana 131028, India b Metallurgy & Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamilnadu 603102, India c Homi Bhabha National Institute, Mumbai-400094, Maharashtra, India d Centre for Innovative Construction Technology (CICT), Department of Civil Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur, Malaysia The Department of Civil Engineering, Faculty of Engineering & Technology, SRM University, Delhi-NCR, Sonepat, successfully organized the international conference titled “Structural Integrity and Interactions of Materials in Civil Engineering Structures – S IIMCES2025” from 21st to 23rd May 2025, held on the university premises. The primary aim of SIIMCES2025 was to foster collaboration among researchers, academicians, practitioners, and industry experts, focusing on advancements in material performance, durability, and structural safety. The conference received an overwhelming response from the global research community, with a total of 294 submissions, including significant contributions from prestigious institutions such as IITs, NITs, Central Universities, and international universities from Brazil, Nigeria, China, Maldives, and Saudi Arabia. After a rigorous double peer-review process, 130 high-quality papers were shortlisted for presentation. We sincerely thank all the authors for submitting their original and significant research contributions to this special issue. A total of 90 papers have been accepted for publication, marking an acceptance rate of 30.6% for the first edition of SIIMCES. We are deeply grateful to the reviewers for their dedicated efforts in providing critical and constructive evaluations of the manuscripts. The conference commenced with an inaugural ceremony followed by a plenary talk delivered by Prof. U. Johnson Alengram from the University of Malaya, Malaysia. The keynote sessions during SIIMCES2025 were delivered by eminent experts from reputed national institutions, enriching the conference with cutting-edge insights and innovative research directions. Each technical session featured a keynote talk from distinguished professors who shared their expertise on various aspects of structural integrity and materials in civil engineering. The keynote speakers included Dr. S. A. Krishnan, (Scientist, Indira Gandhi Center for Atomic Research, Kalpakkam), Prof. (Dr.) K.V.L. Subramaniam, Professor at the Indian Institute of Technology, Hyderabad; Prof. (Dr.) Kranti Gyanchand Jain (Associate Professor at NIT Uttarakhand); Prof. (Dr.) Ajay Kumar (Associate Professor at NIT Delhi); Prof. (Dr.)

* Corresponding author. Tel.: +91-7358135699 E-mail address: rsrirammohan@srmuniversity.ac.in; rsrirammohan@gmail.com

2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under the responsibility of International Conference on Structural Integrity Organizers 10.1016/j.prostr.2025.07.018

R. Mohanraj et al. / Procedia Structural Integrity 70 (2025) 1–2

2

Surender Singh (Associate Professor, Indian Institute of Technology, Madras); Dr. L. Janani, (Assistant Professor, National Institute of Technology, Srinagar); Prof. (Dr.) B. P. Suneja, (Professor & Dean, Rajasthan Technical University, Kota); and Prof. (Dr.) M. K. Shrimali, (Professor (HAG), Malaviya National Institute of Technology, Jaipur). Their valuable contributions added immense value to the conference, fostering meaningful discussions and advancing collaborative research prospects. The technical sessions were conducted in two parallel tracks across nine sessions. Each session was led by distinguished session chairs and co-chairs, ensuring a diverse and high-caliber academic dialogue. The session chairs included Dr. S. A. Krishnan (IGCAR, Kalpakkam) for Session A1; Prof. (Dr.) U. Johnson (University of Malaya, Malaysia) for Session A2; Prof. (Dr.) Priyanka Singh (Amity University, Noida) for Session B1; Prof. (Dr.) Lavanya Prabha (SRM Easwari Engineering College, Tamil Nadu) for Session B2; Dr. Sadet Gokce Gok (Kirklareli University, Türkiye) for Session C1; Dr. Indu Sharma (SRMUH) for Session C2; Dr. Anand Gaurav (ITM(SLS) Baroda University, Gujarat) for Session D1; Prof. (Dr.) R. Krishnasamy (Erode Sengunthar Engineering College, Tamil Nadu) for Session D2; and Dr. Lavish Kumar Singh (Jawaharlal Nehru University, Delhi) for Session E1. The conference concluded with enthusiastic participation and valuable discussions, reinforcing its objective of promoting structural integrity research in civil engineering. The SIIMCES 2025 editorial board extends its heartfelt gratitude to Dr. T. R. Paarivendhar, Hon'ble Founder Chancellor of SRM University, and Dr. Ravi Pachamuthu, Hon'ble Chancellor of SRM University, Delhi-NCR, Sonepat, for their unwavering support in making this international conference a reality. We also sincerely thank Prof. (Dr.) Paramjit S. Jaswal, Vice Chancellor, and Prof. V. Samuel Raj, Registrar of SRM University, Delhi-NCR, Sonepat, for their constant encouragement and approval in hosting this prestigious technical event (Ref. No.: CE/Conf./24/01, dated 08.10.2024) . A special note of appreciation to our Organizing Secretary, Prof. (Dr.) Ranjit Roy, Dean (E & T), for his exceptional planning, commitment, and leadership that played a pivotal role in the success of SIIMCES 2025. We also extend our thanks to Mr. N. Mohan, Assistant Librarian, for his dedicated efforts in verifying the originality of submitted articles and Mr. Sachin Sharma, Web Designer, for consistently updating and maintaining the conference website (www.srmuniversity.ac.in/siimces-2025). Our sincere appreciation is also due to the organizing team members - Mr. Ravi Malik, Mrs. Priyanka Rani, Mr. Ritesh Kumar Roushan, and Mr. Parveen Kaushik- for their valuable contributions and teamwork, which significantly contributed to the grand success of the conference. Our heartfelt thanks to Prof. Francesco Iacoviello, Chief Editor of Procedia Structural Integrity , and Elsevier for their kind support in publishing the peer-reviewed papers as a special issue. We further extend our appreciation to the Elsevier production team for their committed work in ensuring the timely publication of this volume. We hope this special issue will support researchers in advancing their work toward developing safer and more reliable materials and structural systems. We look forward to welcoming you to the next edition of the conference on Structural Integrity and Interactions of Materials in Civil Engineering Structures. SIIMCES2025 Guest Editor

Dr. R. Mohanraj, SRM University, Delhi-NCR, Sonepat

Dr. Abhay kumar Chaubey, SRM University, Delhi-NCR, Sonepat

Dr. S. A. Krishnan, Indira Gandhi Center for Atomic Research, India

Prof. (Dr.) Ubagaram Johnson Alengaram, University of Malaya, Malaysia.

Available online at www.sciencedirect.com

ScienceDirect

Procedia Structural Integrity 70 (2025) 477–484

Structural Integrity and Interactions of Materials in Civil Engineering Structures (SIIMCES-2025) Advanced EMI-Based Evaluation of Structural Damage in Composite Fibre Concrete with Integrated Piezoelectric Sensors Maheshwari Sonker a* , Rama Shanker a a Department of Civil Engineering, MNNIT Allahabad, Prayagraj, India Abstract Composite fibre concrete offers enhanced strength, durability, and corrosion resistance, making it an attractive material for modern infrastructure. However, its performance can be compromised by damage such as micro-cracking, delamination, and fiber rupture. This research evaluates performance of the electromechanical impedance (EMI) technique using piezoelectric sensors to detect structural damage in composite fibre concrete. Standard cube specimens were prepared using ordinary Portland cement, Class F fly ash, and polypropylene fibers, and surface-mounted piezoelectric patches were employed for real-time monitoring. The EMI method, a non-destructive testing approach, measures changes in electrical impedance to identify damage. Systematic damage was introduced into the specimens, and impedance signatures were recorded over a frequency range of 30 – 400 kHz. Analysis indicated a strong relationship between the root mean square deviation (RMSD) index and the severity of cracks, with increased sensitivity observed at shorter sensor to the damage distances. Shifts in conductance signature curves provided additional insights, while a novel damage index scaled from 0 to 1 enabled quantitative assessment of damage evolution. Furthermore, evaluations of equivalent stiffness and damping parameters enhanced understanding of the structural response under degradation. Overall, the study demonstrates that the EMI technique, when integrated with piezoelectric sensors, is a reliable tool for real-time structural health monitoring, offering valuable information for maintenance planning and for extending the service life of composite fibre concrete structures. The results indicate that early detection of damage using the EMI method can improve maintenance planning and reduce risks of failure in composite concrete applications.

© 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under the responsibility of International Conference on Structural Integrity Organizers

Keywords: piezoelectric sensors; non-destructive testing; damage detection; crack propagation; polypropylene fiber; service life prediction

* Corresponding author. Tel.: +91-7052378920 E-mail address: maheshwarisonker12001@gmail.com

2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under the responsibility of International Conference on Structural Integrity Organizers 10.1016/j.prostr.2025.07.080

Maheshwari Sonker et al. / Procedia Structural Integrity 70 (2025) 477–484

478

1. Introduction Composite fibre concrete is widely used for its high strength, durability, and resistance to environmental degradation. However, mechanical and environmental stressors can still lead to micro-cracks and damage over time. Traditional inspection methods are invasive and limited, highlighting the need for real-time, non-destructive monitoring techniques. The Electromechanical Impedance (EMI) technique, leveraging piezoelectric sensors, offers a non-destructive, real-time alternative capable of detecting minute structural changes through impedance variations. Previous studies have shown the effectiveness of the electromechanical impedance (EMI) technique for damage detection in composite materials. For instance, Salahaldein (2016) assessed damage detection in glass fiber composite plates using various PZT attachment methods to identify defects such as delamination and cracks through experimental analysis and finite element verification. Additionally, Shakir et al. (2008), H. Im et al. (2019) introduced a novel inverse algorithm for damage localization in unidirectional composite samples using the EMI technique, significantly improving localization accuracy. However, these studies primarily focus on fiber-reinforced polymer composites and do not specifically address the experimental evaluation of damage detection in composite fiber concrete using the EMI technique. This study aims to enhance the application of the Electro-Mechanical Impedance (EMI) technique for damage detection in composite fibre concrete structures, contributing to the field of structural health monitoring (SHM). Rather than limiting the scope to conventional concrete, this work focuses on the performance of the EMI method in detecting various damage levels in composite fibre concrete. A summary of the damage scenarios investigated is presented in Table 1. It introduces a technique designed to improve sensitivity and address challenges in identifying damage through variations in impedance signatures Peng (2013), Wandowski (2021), K. Chandramouli (2010) and Enfedaque et al. (2017). This study aims to detect, identify, and quantify multiple types of damage in concrete using the EMI technique. By calculating Root Mean Square Deviation (RMSD), Correlation Coefficient (CC), and Mean Absolute Percentage Deviation (MAPD) values from conductance signatures of different grade of concrete mix, we can effectively locate damages, assess their severity, and experimentally validate any structural changes Sonker (2025).

Table 1. Summary of different damages monitoring. Author & Year Method

Application

Key Result

Narayanan & Subramaniam (2017)

PZT sensors, EMI

Damage monitoring in concrete

EM peaks indicate load damage

AE, convolutional neural network (CNN) model Acoustic emission (AE), K Nearest Neighbors (KNN)

Online structural health monitoring (SHM)

99.6% accuracy, 0.555 mJ energy KNN effective for damage estimation

Zhang et al. (2023)

Real-time reinforced concrete (RC) monitoring

Inderyas et al. (2024)

Piezo sensors, EMI

Corrosion in prestressed concrete (PSC)beams

EMI tracks corrosion accurately

Bansal et al. (2024)

2. EMI Measurement Setup An LCR- meter was employed to measure electrical impedance of PZT sensors across a 30–400 kHz frequency range. Initial baseline signatures were recorded for undamaged specimens in eq. 1. = + = 4ω 2 ℎ [ 3 3 − 2d 2 3 1 (1− ) + 2d 2 3 1 (1− ) ( , , + , ) ] (1) Where, 3 1 = electrical admittance; ω represents the excitation frequency, l and h denote the half-length and the thickness of PZT patch, respectively ; 3 3 = 3 3 (1−δ ) is the complex dielectric constant at constant stress; = complex tangent ratio; ν = Poisson’s ratio . The impedance of mechanical structure is sensitive to the changes in its properties, such as stiffness, mass, and damping, which may occur due to damage, or environmental effects. By monitoring shifts in the electrical impedance spectra, damage can be identified and characterized.

Maheshwari Sonker et al. / Procedia Structural Integrity 70 (2025) 477–484

479

% = √ ∑ ( 1 − 0 ) 2 = 1 ∑ ( = (∑ | 1 − 0 | 0 = 1 )/ 1 − 1 1 0 ∑ ( 1 − 0̅̅̅̅ ). ( 0 − 0̅̅̅̅ ) = 1 0 ) 2 = 1 100

(2)

(3)

(4) Where, 1 = damaged state conductance (GD) at frequency I, 0 = healthy state conductance (GH) at frequency i, and N = no. of data considered. The EMI technique operates primarily in high-frequency ranges (typically 30 – 400 kHz), ensuring sensitivity to local structural changes near the PZT sensor. Key parameters, such as resonant frequency shifts and statistical indices (e.g., RMSD, MAPD, CC), are employed to assess the severity of the damage (using equation (2), (3), (4). 3. Materials and Methods Composite fibre concrete specimens were developed using Ordinary-Portland-Cement (OPC), Class F flyash as a partial cement replacement, and crimped polypropylene fibres to enhance tensile performance shown in Fig. 1. The fibre content was maintained at 0.9% by volume of concrete. Concrete specimens of grades M60 and M65 were prepared using Ordinary Portland Cement, fine aggregates (IS: 383-2016 (Zone-II)), coarse aggregates, fly ash and polypropylene fibers at varying contents. A polycarboxylate-based superplasticizer, SIKAPLAST-HE2002, was incorporated to maintain desired workability at a constant water-binder ratio. The admixture had a solids content of 41%, pH of 5.8, and specific gravity (G) of 1.08 (Table 2).

Fig. 1. Snapshot of polypropylene fibre (a), (b) fly ash. After 28 days of curing under controlled conditions, artificial damage was introduced at different depths. Piezoelectric (PZT) patches were affixed using epoxy adhesive to surface as depicted in Fig. 2, and the Electro-Mechanical Impedance (EMI) technique was used to monitor structural changes. Conductance signatures were recorded within the 30 - 400 kHz frequency range utilizing an LCR meter. Damage quantification was performed by calculating RMSD, CC, MAPD between healthy and damaged states (see Fig. 4).

Table 2. Different proportions of concrete mixture variations. Mix Cement Kg/m 3 Fly ash Kg/m 3 Water Kg/m 3

Polypropy lene Fibre Kg/m 3

Sand Kg/m 3

20mm Kg/m 3

10mm Kg/m 3

Admixtur e Kg/m 3

Lab Target Strength at 28 days (N/mm 2 )

5.2710

68.25

M60 M65

438.30 456.22

116.1 122.6

29.29 30.41

158.14 157.14

716.39 703.88

98.99 98.05

890.89 882.49

5.4740

73.9

Maheshwari Sonker et al. / Procedia Structural Integrity 70 (2025) 477–484

480

Portable computer

Concrete Cube

PZT sensor bonded at surface

M65

Impedance analyser

M60

Cable-wire

Fig. 2. Setup for recording the admittance signature acquisition of concrete cubes. 3.1 Induced Structural Damage and EMI Characterization through Conductance Response Analysis A comparative examination of conductance (real) signatures reveals a progressive deviation from the baseline, correlating with an increase in damage of depth up to 12 mm. In the standard 150 × 150 × 150 mm concrete cube, cracking initiates near the surface-mounted PZT sensor, positioned at distances of 50 mm and 100 mm from specimen corner. Initially, 6 mm deep cracks are introduced at the 50 mm mark, followed by the acquisition of conductance versus frequency data. Subsequently, additional cracks are induced at the 100 mm interval, with crack depths extending to 8 mm and 12 mm, resulting in corresponding shifts in conductance signatures, which are continuously monitored. As damage severity increases (6 mm, 8 mm, and 12 mm depths), the conductance signature shifts leftward, indicating greater damage. The shifting extent varies with damage level, with further leftward shifts for damage exceeding 12 mm, as shown in Fig.3. Impedance signatures were separated into conductance (real) components. Observed shifts in peak positions and amplitude suggested changes in local mechanical properties.

1.99E-03

M60

1.79E-03

1.59E-03

baseline state CUT-1_6mm CUT-2-6mm CUT-1_8mm CUT-2-8mm CUT-1_12mm CUT-2-12mm

1.39E-03

1.19E-03

Conductance G

9.90E-04

7.90E-04

138000 148000 158000 168000 178000 188000 198000 208000 218000 228000

Frequency (Hz)

Maheshwari Sonker et al. / Procedia Structural Integrity 70 (2025) 477–484

481

3.11E-03

M65

2.71E-03

baselinestate CUT-1_6mm CUT-2-6mm CUT-1_8mm CUT-2-8mm CUT-1_12mm CUT-2-12mm

2.31E-03

Conductance G

1.91E-03

1.51E-03

180000

200000

220000

240000

260000

280000

Frequency (Hz)

Fig. 3. Variation of conductance with frequency for different damage depths in M60 and M65 concrete grades. The conductance versus frequency signatures were recorded to monitor shifts in the resonance peak, with leftward shift indicating increasing damage severity. In Fig. 3 displays curves representing different damage states: "baseline state," "CUT-1_6mm," "CUT-2_6mm," "CUT-1_8mm," "CUT-2_8mm," "CUT-1_12mm," and "CUT-2_12mm," corresponding to varying damage depths severity within the concrete.

4. Results And Discussion

The RMSD was calculated between baseline and damaged impedance signatures. An increase in RMSD correlated with crack propagation. Damage quantification were performed by calculating RMSD, CC, MAPD between healthy and progressively damaged states (see Fig. 4). As damage severity increases, the RMSD, MAPD, and CC values show an upward trend, indicating greater severity. This shows that deeper damage leads to more significant deviations from the baseline, confirming the link between damage depth and conductance signature shifts as shown in Fig. 4. thereby validating the sensitivity of the EMI technique to varying damage severities in composite fibre concrete.

10

M60

RMSD MAPD CC (Correlation Coefficient)

8

6

%

4

2

0

1_6 mm 2-6 mm 1_8 mm 2-8 mm 1_12 mm 2-12 mm

Depth of damages

Maheshwari Sonker et al. / Procedia Structural Integrity 70 (2025) 477–484

482

10

M65

8

RMSD MAPD CC (Correlation Coefficient)

6

%

4

2

0

1-6 mm 2_6 mm 1-8 mm 2_8 mm 1-12 mm 2_12 mm

Depth of damages

Fig. 4. RMSD, MAPD,CC value of damages identical dimensions at varying depths.

4.1 Evaluation of Mechanical Parameters As shown in Fig. 5 and 7, A decreasing trend in equivalent stiffness (K) with increasing damage depth (6 mm, 8 mm, 12 mm) in composite fibre concrete (M60, M65). Conversely, equivalent damping (c) increases with progressively increasing damage depths as shown in Fig. 6 and 8. The reduction in quivalent stiffness and quivalent damping reflects the growing severity of damage, confirming the EMI technique’s responsiveness to structural degradation .

1900 2000 2100 2200 2300 2400 2500 2600 2700

M60

K (10 4 N/m)

BS

1_6mm 2-6mm 1_8mm 2-8mm 1_12mm 2-12mm

Depth of damages

Fig. 5. Variation of the equivalent stiffness versus damage depth for M60 grade concrete.

5800

M60

5600

5400

5200 C (Ns/m)

5000

BS 1-6mm 2-6mm 1-8mm 2-8mm 1-12mm 2-12mm

Depth of Damage

Fig. 6. Variation of the equivalent damping versus damage depth for M60 grade composite concrete.

Maheshwari Sonker et al. / Procedia Structural Integrity 70 (2025) 477–484

483

800

M65

600

400

200 c (Ns/m)

0

HS 1_2mm 2-2mm1_6mm2-6mm1_8mm2-8mm

Depth of damages

Fig. 7. Variation of the equivalent damping versus damage depth for M65 grade concrete.

3.50E+08

M65

2.80E+08

2.10E+08

1.40E+08

k (N/m)

7.00E+07

1.00E-03

HS 1_2mm 2-2mm 1_6mm 2-6mm 1_8mm 2-8mm

Depth of damages

Fig. 8 . Variation of the equivalent stiffness versus damage depth for M60 grade composite concrete.

The study confirmed that proximity of the PZT sensor to the damage site significantly affects sensitivity and detection accuracy. EMI technique offers high-resolution insights into micro-level changes, supporting early diagnostics and preventive maintenance. 5. Conclusion The Electro-Mechanical Impedance technique, utilizing embedded the PZT sensors, demonstrates high efficacy as a robust and non-invasive methodology for structural health monitoring (SHM) of composite fibre-reinforced concrete. This approach enables early-stage damage detection and facilitates data-driven decisions for maintenance scheduling and service life optimization. Experimental observations reveal a strong correlation between severity of damages and the RMSD index, with sensors located at reduced patch to damage the distances exhibiting enhanced sensitivity to damage progression. RMSD trends consistently indicate elevated values corresponding to increased damage intensity at closer proximities, underscoring the spatial responsiveness of the PZT sensors. Furthermore, the analysis of mechanical impedance parameters indicates a progressive reduction in the equivalent stiffness (k) and a corresponding increase in equivalent damping (c) with increasing damage depth (damage scenarios 1 and 2). These parameter variations substantiate the degradation in local structural integrity and validate performance of the EMI technique for quantitative damage assessment. Future work will focus on extending the EMI-based approach to monitor real-time damage progression under varying environmental and loading conditions. Acknowledgments The author would like to gratefully thank the Department of Civil Engineering of the Motilal Nehru National Institute of Technology Allahabad, Prayagraj, India.

Maheshwari Sonker et al. / Procedia Structural Integrity 70 (2025) 477–484

484

References

Bansal, T., Talakokula, V., & Saravanan, T. J., 2024. EMI-based monitoring of prestressed concrete beam under chloride-induced corrosion using an embedded piezo sensor, Measurement: Sensors, 33, 101158. Enfedaque, A., Alberti, M., Gálvez, J., & Domingo, J. 2017. Numerical simulation of the fracture behaviour of glass fibre reinforced cement, Construction and Building Materials, 136, 108-117. H. Im, S. Hong, Y. Lee, H. Lee, and S. Kim, 2019. A colorimetric multifunctional sensing method for structural-durability-health monitoring systems,” Adv. Mater., vol. 31, no. 23, Art. no. 1807552, Inderyas, O., Tayfur, S., Alver, N., Catbas, F.N., 2025. A Machine Learning – Based Damage Estimation Model for Monitoring Reinforced Concrete Structures, In: Matarazzo, T., Hemez, F., Tronci, E.M., Downey, A. (eds) Data Science in Engineering Vol. 10. IMAC 2024. Conference Proceedings of the Society for Experimental Mechanics Series. Springer, Cham. Chandramouli, K. & Rao, P Srinivasa Rao & Narayanan, Pannirselvam & Sekhar tirumala, Seshadri & Sravana, P.. 2010. Strength properties of glass fiber concrete. ARPN J Eng Appl Sci. 5. 1-6. Narayanan, A., & Subramaniam, K. V. L., 2017. Damage assessment in concrete structures using piezoelectric based sensors. Revista ALCONPAT, 7(1), 25-35. Peng Zhang and Qingfu Li, 2013. Fracture Properties of Polypropylene Fiber Reinforced Concrete Containing Fly Ash and Silica Fume, Research Journal of Applied Sciences, Engineering and Technology vol. 5, no.2, pp. 665-670. Salahaldein Alsadey, 2016. Effect of Polypropylene Fiber Reinforced on Properties of Concrete, Journal of Advance Research in Mechanical and Civil Engineering. Shakir, A., and Maha, E., 2008. Effect of polypropylene fibers on properties of mortar containing crushed brick as aggregate, Eng. And Tech., Vol. 26, No. 12, PP. 1508-1513. Wandowski, T., Malinowski, P., & Ostachowicz, W., 2021. Improving the EMI-based damage detection in composites by calibration of AD5933 chip. Measurement, 171, 108806. https://doi.org/10.1016/j.measurement.2020.108806. Y. Zhang, V. Adin, S. Bader and B. Oelmann, 2023. Leveraging Acoustic Emission and Machine Learning for Concrete Materials Damage Classification on Embedded Devices," in IEEE Transactions on Instrumentation and Measurement, vol. 72, pp. 1-8, Art no. 2525108. Sonker, M., Shanker, R., 2025. Enhanced diagnostic approach for multiple damage detection and severity evaluation through EMI-based sensing and artificial neural network model. Asian J Civ Eng 26, 747 – 760.

Available online at www.sciencedirect.com

ScienceDirect

Procedia Structural Integrity 70 (2025) 11–18

Structural Integrity and Interactions of Materials in Civil Engineering Structures (SIIMCES-2025) Analyses of Shear Capacity Equations for UHPFRC Beams Abutu Simon JohnSmith a, *, Mustapha Jamaa Garba b , Hussaini Abdullahi Umar c,d , Shawon Msughter Caesar e a Department of Civil Engineering, Federal University of Technology, Babura, Nigeria

b School of Civil Engineering, Central South University, Changsha, China c Department of Civil Engineering, Ahmadu Bello University, Zaria, Nigeria d College of Civil Engineering, Hunan University, Changsha, China e Building Research Department, Nigerian Building and Road Research Institute, Ota, Nigeria

Abstract This research assesses the capability of existing shear capacity equations to adequately predict the shear strengths/ultimate loads of ultra-high performance fibre reinforced concrete (UHPFRC) beams in order to check their level of accuracy and to determine the equation that can be reliably used to predict/design UHPFRC beams against shear loading. Influential shear variables like shear span-depth ratio ( a /d), percentage volume of steel fibre ( V f ), longitudinal tensile reinforcement ratio ( ρ ), compressive strength, stirrup spacing (s), steel fibre topology and steel fibre-UHPFRC matrix bond stress were used to carefully select some shear capacity equations as well as some beams from existing literature for the analyses. Major findings from the analyses revealed that UHPFRC beams’ shear capacity is greatly underestimated by CECS2020 (2020), SIA 2052 (2016), JSCE (2006), Imam et al. (1997), Khuntia et al. (1999), Ashour et al. (1992), Al- Ta’an and Al-Feel (1990), and Narayanan and Darwish (1987). Also, Shear capacity equations developed by Hussein (2015), Aoude et al. (2012), Kwak et al. (2002) and NF P 18-710 (2016) seriously overestimate the shear capacity of UHPFRC beams. Further findings from the analyses showed that Smith and Xu ’s (2023) shear capacity equation is capable of perfectly predicting the shear capacity of both UHPFRC beams and UHPFRC beams containing coarse aggregate (UHPFRC-CA) with minimal deviations and over 92% consistent agreement with experimental values. Finally, it is advised that researchers should make use of experimental data to develop new equations for analysing the structural integrity of new materials like UHPFRC members instead of simply modifying existing equations for use in evaluating a new material with different properties. © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under the responsibility of International Conference on Structural Integrity Organizers

Keywords: Analyses; beam; equations; shear capacity; ultra-high performance fibre reinforced concrete

* Corresponding author. Tel.: +2348035394902 E-mail address: sasjohn.civil@futb.edu.ng

2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under the responsibility of International Conference on Structural Integrity Organizers 10.1016/j.prostr.2025.07.020

Abutu Simon John Smith et al. / Procedia Structural Integrity 70 (2025) 11–18

12

1. Introduction Researchers in recent times have intensified their efforts on investigating the structural behaviour of ultra-high performance fibre reinforced concrete (UHPFRC) due to its high strength, ductility, excellent durability (Azmee and Shafiq, 2018) and capability of improving the sustainability of buildings and other infrastructure components (Schmidt and Fehling, 2005). The structural behaviour of UHPFRC is different from ordinary concrete, and they cannot be designed using standards and codes for ordinary concrete because steel fibre’s presence in UHPFRC beam contributes immensely to its structural capacity. Considering shear capacity for instance, fibre topology and fibre UHPFRC matrix bond play vital roles in resisting applied shear load before crack appearance and after crack appearance. So using ordinary concrete beam ’s shear capacity equation to e valuate UHPFRC beam ’s shear capacity will lead to serious underestimation. This is why researchers, through series of studies have developed many techniques and provided a lot of data to help simplify the analysis and design of the structural integrity of UHPFRC members. One of such techniques is the development of equations for predicting the shear capacity of UHPFRC beams through the modification of either normal concrete beam’s shear capacity equation or steel fibre reinforced concrete (SFRC) beam’s shear capacity equation. Some of which include: The modification of ACI 318 -14 shear capacity equation for normal concrete by Ahmad et al. (2019) to develop UHPFRC’s shear capacity equation; which was reported to be reasonably accurate in predicting the shear capacity of UHPFRC beam. The development of UHPFRC’s shear capacity equation from ACI 318 -14 shear capacity equation, whose results after comparison with the shear capacity obtained from experiment showed reasonable correlation (Hussein, 2015). Jia-nan et al. (2020) through experimental and theoretical analysis of UHPFRC beams’ shear strength using research variables like concrete contribution, fibres and stirrups, proposed a model for estimating the shear strength of UHPFRC beams. The procedures for evaluating the shear capacity of UHPFRC beams have also been included in different standards like the Chinese technical specification for UHPFRC structures (CECS2020, 2020 ); Swiss standard for UHPFRC’s materials, design and execution (SIA 2052, 2016); Japanese recommendations for design and construction of UHPFRC structures (JSCE, 2006); French rules for UHPFRC design (NF P 18-710, 2016); and test and design methods for SFRC (RILEM TC 162-TDF, 2003). In recent times, beside the modification of existing normal concrete/SFRC beam’s shear capacity to develop UHPFRC beam’s shear capacity; and the release of technical guide and specification for UHPFRC structures, there have been serious advancements in the field of shear capacity prediction for UHPFRC beams as researchers are developing new shear capacity equations for UHPFRC beams and standards are being updated to include shear design of UHPFRC beams. For instance, Smith and Xu (2023) developed a new shear capacity equation that incorporates both direct and indirect shear influencing factors; and which is capable of correctly estimating the shear capacity of both UHPFRC and UHPFRC-CA beams. Also, AASHTO (2024) released the firstedition of the Guide Specifications for Structural Design with ultra-high performance concrete, which greatly improved the design procedures of UHPFRC beams against shear loading. Despite the advancements, there are still challenges in the field of shear capacity prediction of UHPFRC as there are still a lot of data needed in the area of expanding the different shear influencing parameters into many levels, so that the effects of changes in those levels can be ascertained. This challenge is a serious one because conducting experiment to cater for different levels of shear parameters for UHPFRC is highly expensive. However, this challenge may be overcome by conducting parametric study of the shear behaviour of UHPFRC beams using finite element numerical modelling and simulation. The structural failure of concrete beams in shear is a complex mechanism as explained by Smith and Xu (2023) in their study that UHPFRC beam’s shear resistance is provided by three different mechanisms: (1) UHPFRC -steel fiber bond (2) Stirrup strength (3) UHPFRC strength (i. e. UHPFRC compression zone, aggregate interlock and dowel action). These shear mechanisms occur in sequential stages starting with dowel action resistance, then aggregate interlock after dowel action reaches its optimum capacity. The next shear resistance is provided by the UHPFRC’s compression zone, after which stirrups in the UHPFRC beam contribute their resistance to the applied load when diagonal cracks appear in the beam. The stirrups continue to provide the shear resistance until they yield, leading to the widening of the diagonal crack. Once the crack widens, the steel fibre resisting pull out in the cracked UHPFRC is the last to provide shear resistance until the UHPFRC-steel fibre bond is broken. The loss of UHPFRC steel fibre bond leads to the attainment of its pull-out force capacity resulting in their pull out from the beam and eventual failure.

Abutu Simon John Smith et al. / Procedia Structural Integrity 70 (2025) 11–18

13

The various equations and standards developed for analyzing the shear capacity of UHPFRC beam have their shortcomings because no single equation has accurately captured all the direct and indirect factors that contribute to UHPFRC beam’s shear resistance. This is why researchers are still proposing new shear capacity equations that take their research parameters into consideration. The discrepancies in the different existing equations for evaluating the shear capacity of UHPFRC beams call for their assessment in order to determine the equation that can best predict UHPFRC beam’s shear capacity with the highest degree of accuracy. So, this study analyzes the different existing shear capacity equations to check their level of accuracy when compared with experimental shear capacities. In terms of novelty, the findings from this study can be practically applied to the structural design of UHPFRC/UHPFRC-CA beams subjected to shear loading at experimental design stage to ensure that the beam fails in shear instead of flexure (i.e. through the use of the most robust shear capacity equation as recommended by this study). The application of th is study’s findings can also be extended to the experimental testing of UHPFRC/UHPFRC-CA beams as the rightly predicted ultimate load/shear strength will be used to allocate the correct amount of load to be applied at each loading stage of the experiment; therby ensuring that the true first flexural cracking load, first shear cracking load, ultimate load and their corresponding crack widths and deflections are obtained. 2. Method of Analyses The method of analyses employed for this study involves the selection of different shear capacity equations that have been developed by researchers and in different standards as well as the selection of some beams from existing literatures, so that their experimental shear capacities/ultimate loads can be compared with those evaluated using the selected shear capacity equations. The selection of the different shear capacity equations used in this study was based on the equations that have at least 2 of the following shear design parameters or UHPFRC/UHPFRC-CA properties: volume of steel fibre ( V f ), shear span-depth ratio ( a /d), stirrups, longitudinal reinforcement ratio ( ρ ), fibre factor (an equation containing volume, length, diameter and bond factor of steel fibre as a single term), bond strength of steel fibre-UHPFRC/UHPFRC- CA matrix (τ), and compressive strength ( f cu ) of UHPFRC/UHPFRC-CA. These parameters and properties contain both direct and indirect shear influencing factors that affect the shear performance of any UHPFRC beam subjected to shear loading; and these are the variables considered before selecting all the shear capacity equations used for this study’s analyses. The selected experimental beams from literature were chosen based on the condition that the following variables can be established about the beam: compressive strength, tensile strength, volume of steel fibre ( V f ), length of steel fibre ( l f ), diameter of steel fibre ( d f ), longitudinal tensile reinforcement ratio ( ρ ), shear span-depth ratio ( a /d), depth of the beam (d), breadth of the beam (b), height of the beam (h), depth of the UHPFRC/UHPFRC-CA beam ’s compression zone (x 0 ), angle of the shear/diagonal crack to the longitudinal tensile reinforcement (θ), yield strength of the longitudinal tensile reinforcement ( f yl ), and area of the longitudinal tensile reinforcement ( A s ). The selected shear capacity equations include: Imam et al. (1997), Khuntia et al. (1999), Aoude et al. (2012), Ashour et al. (1992), Al- Ta’an and Al-Feel (1990), Kwak et al. (2002), Narayanan and Darwish (1987), Hussein (2015), Smith and Xu (2023), JSCE (2006), RILEM TC 162-TDF (2003), SIA 2052 (2016), NF P 18-710 (2016), CECS2020 (2020). The selected beams from existing literature include: beams US2-1.5-3.0 and US2-1-3.0 from Hussein (2015) taken as b1 and b2 respectively; beams SB1, SB2 and SB3 from Lim and Hong (2016) taken as b3, b4 and b5 respectively; beam M-6/015-1 from Gustafsson and Noghabai (1999) taken as b6; beam BS-100-2.0 from Son et al. (2011) taken as b7; beams B(1-6)a, B1b, B2b, B3b and B4b from Smith and Xu (2024) taken as b8, b9, b10, b11 and b12 respectively. The research variables inputted into the various equations considered in this study for the analyses of the different beams’ shear capacity/ultimate load are presented in Table 1 . Nomenclature UHPFRC Ultra-high performance fibre reinforced concrete UHPFRC-CA Ultra-high performance fibre reinforced concrete containing coarse aggregate SFRC Steel fibre reinforced concrete

Abutu Simon John Smith et al. / Procedia Structural Integrity 70 (2025) 11–18

14

Table 1. Research variables used for evaluating the selected beams’ shear capacity/ultimate load Research variables Beams from existing literature b1 b2 b3 b4 b5 b6 b7 b8 b9

b10

b11

b12

Compressive strength (N/mm 2 )

153.9 152.8 166.9 166.9 166.9 108.9 100

154.6 142.4 165.2 154.6 154.6

Tensile strength (N/mm 2 ) V f (%) l f (mm) d f (mm)

12.9 9.3

11.5 11.5 11.5 4.32

-

5.5

5.3

5.5

5.5

5.5

1.5 1

1.5 1.5 1.5 1

2 6

2

2

3

2

2

13

13

19

19

19

6

13

22

13

13

13

0.2 0.2

0.2 0.2 0.2 0.15 0.15

0.2

0.3

0.2

0.2

0.2

s(mm)

-

-

165 110 66

-

-

175

175

175

175

175

0.081 0.081 0.078 0.078 0.078 0.031 0.032 0.0373 0.0373 0.0373 0.0373 0.0373

ρ

a /d(mm)

3

3

3

3

3

2.9 2

2.8

2.8

2.8

2.8

2.08 350

a (mm)

642 642

660 660 660 1250 600

475

475

475

475

d ca (mm) d(mm) b(mm) h(mm) x 0 (mm)

0

0

0

0

0

16

0

10

10

10

10

10

254 254 150 150 300 300

220 220 220 410 300 150 150 150 200 200 290 290 290 500 350

168.5 168.5 168.5 168.5 168.5

100 200

100 200

100 200

100 200

100 200

15.5 0

49.9 0

88 30

117.3 0

58 42

30 53

55 57

30 53

7

θ ( o )

15

20

25

30

45

37

45

f yl (N/mm ′ (N/mm 2 ) - f ys (N/mm 2 ) - 2 )

468 468

600 600 600 590 400

653 414 414 628

653 414 414 628

653 414 414 628

653 414 414 628

653 414 414 628

- -

-

-

-

- -

- -

400 400 400

A s (mm

2 )

2800 2800

2642 2642 2642 2513 2454

′ (mm 2 ) 2 )

- -

- -

-

-

-

- -

- -

66.37 66.37 66.37 66.37 66.37 66.37 66.37 66.37 66.37 66.37

A ss (mm

157 157 157

3. Results of Analyses and Discussions The results obtained from analyzing all the beams considered in this study using the various selected shear capacity equations are presented in Table 2; and it revealed that CECS2020 (2020), SIA 2052 (2016) (with the exception of b1, b2, b3, b4 and b5), JSCE (2006) (with the exception of b1, b2, b3, b4 and b5), Imam et al. (1997), Khuntia et al. (1999), Ashour et al. (1992) (except for b9), Al- Ta’an and Al-Feel (1990) (except for b9), Narayanan and Darwish (1987) seriously underestimated the beams’ shear strength/ultimate load even though the equations were developed with the inclusion of shear design variables that directly affect UHPFRC shear capacity. The possible implications of the identified underestimations of the UHPFRC/UHPFRC- CA beams’ ultimate load/shear capacity in practice include: (1) designing UHPFRC/UHPFRC-CA beams with insufficient shear reinforcement to resist shear force which may lead to brittle failure. (2) reducing the safety margin of the structure and subjecting the beam to failure under normal or unexpected loads. The equations that seriously overestimated the beams’ shear strength/ultimate load as can be seen in Table 2 include: Hussein (2015) (with the exception of b1 and b2), Aoude et al. (2012), Kwak et al. (2002) and NF P 18-710 (2016). The main implication of overestimating UHPFRC/UHPFRC- CA beams’ shear capacity in practice is the fact that it leads to over -designing for shear, which in turn leads to uneconomical design. Comparative analysis of RILEM TC 162-TDF (2003) with the other equations (excluding Smith and Xu (2023)) showed that it gave a better estimate of all the beams’ shear strength/ultimate load. However, the deviations of RILEM TC 162-TDF (2003) from experimental results were inconsistent in terms of lower and higher values that reached a high value of -42.6% (see Table 3). The shear strength/ultimate load predicted using Smith and Xu (2023) equation as presented in Table 2 provided the best results that showed very high correlation (over 92% consistent correlation) with the experimental shear strength/ultimate load.

Abutu Simon John Smith et al. / Procedia Structural Integrity 70 (2025) 11–18

15

Table 2. Estimation of UHPFRC beams’ ultimate shear capacity using existing equations Equations from existing literatures

Shear capacity/ultimate load of UHPFRC beams from existing literatures (kN) b1 b2 b3 b4 b5 b6 b7 b8 b9

b10 b11 b12

Experiment

455 395 4.03 1.6 160 137 7782 3147 240 219 251 225 923 913 254 239 429 323 429 367 999 560 278 276 1106 591 1666 991 216 166

476 537 552 325 493

273 258 283 265 360

Imam et al. (1997) Khuntia et al. (1999) Aoude et al. (2012) Ashour et al. (1992) Al- Ta’an and Al -Feel (1990) Kwak et al. (2002) Narayanan and Darwish (1987)

91

133 216 0.03 0.2

53

53

53

0.4 53

262 304 388 195 216 2782 3353 1824 1023 2503 307 348 432 303 362 343 407 452 286 338 856 898 982 418 698 334 376 460 277 296 772 957 703 379 563 453 517 550 310 492

207 211 213 154 234 940 707 535 639 1101 250 253 254 197 320 239 263 231 201 304 1296 1234 1351 1243 1907 231 231 237 178 277 468 418 336 378 490 273 261 278 215 340 210 171 167 176 199 283 269 295 236 283

Hussein (2015)

Smith and Xu (2023)

JSCE (2006)

554 596 599 286

-

RILEM TC 162-TDF (2003) SIA 2052 (2016) NF P 18-710 (2016) CECS2020 (2020)

333 371 447 402 283

654 735 724 214

-

169 113 99

115 152

1012 1097 1061 676 1002

412 330 328 304 391 178 171 186 178 195

261 303 387 159

-

Table 3. Percentage deviation of existing equations from experiment Equations from existing literatures

Percentage deviation (%) of existing shear capacity equations’ results from experimental results b1 b2 b3 b4 b5 b6 b7 b8 b9

b10 b11 b12

Imam et al. (1997)

-99.1 -99.6 - 80.8

- 75.2 - 43.4 - 35.2 - 24.2

- 60.9 - 29.7 - 21.7 - 18.1

- 99.9

- 99.9 - 56.2 - 26.6 - 31.4

-80.6 -79.5 -81.3 -99.8 -85.3 -24.2 -18.2 -24.7 -41.9 -35 -8.4 -1.9 -10.2 -25.7 -11.1 -12.5 1.9 -18.4 -24.2 -15.6 374.7 378.3 377.4 369.1 429.7 -15.4 -10.5 -16.3 -32.8 -23.1 244.3 174 89 141.1 205.8 0 1.2 -1.8 -18.9 -5.6 -23.1 -33.7 -41 -33.6 -44.7 3.7 4.3 4.2 -10.9 -21.4 -38.1 -56 -65 -56.6 -57.8 50.9 27.9 15.9 14.7 8.6 -34.8 -33.7 -34.3 -32.8 -45.8 71.4 62 18.7 42.6 36.1

Khuntia et al. (1999) -64.8 -65.3 - 45

- 40

Aoude et al. (2012) Ashour et al. (1992) Al- Ta’an and Al Feel (1990) Kwak et al. (2002) Narayanan and Darwish (1987) Hussein (2015) JSCE (2006) RILEM TC 162 TDF (2003) SIA 2052 (2016) NF P 18-710 (2016) CECS2020 (2020)

1610 696.7

484.5 524.4 230.4 214.8 407.7

-47.3 -44.6 - 35.5 -44.8 -43 - 27.9

- 6.8 - 12

102.9 131.1

79.8 67.2 77.9 28.6 41.6

-44.2 -39.5 - 29.8

- 30

- 16.7

- 14.8

- 40

-5.7 -18.2

62.2 78.2 27.4 16.6 14.2

Smith and Xu (2023) -5.7 -7.1 - 4.6

- 3.7

- 0.4 8.5

- 4.6 - 12

- 0.2

219.6 41.8

16.4 11

-

-38.9 -30.1 - 30

- 30.9

- 19 23.7

- 42.6

243.1 49.6 266.2 150.9

37.4 36.9 31.2

- 34.2

-

112.6 104.3 92.2 108 103.2

-52.5 -58 - 45.2

- 43.6

- 29.9

- 51.1

-

The reason why Narayanan and Darwish (1987) seriously underestimated the beams’ shear strength/ultimate load is that, it was not developed for UHPFRC beams but for SFRC beams. This means that the data used for its development were those of SFRC beams; and this makes it to be an inappropriate equation for evaluating the shear capacity of UHPFRC. For CECS2020 (2020), the underestimation was as a result of the lack of a term to account for fibre pull out force in the equation, as fibre topology term considered in the equation was not enough to represent the total contribution of steel fibre to shear resistance. The lower shear strength/ultimate load predicted by SIA 2052 (2016) was due to the non-representation of both fibre-UHPFRC matrix bond stress and fibre topology in the equation. JSCE (2006) predicted lower shear strength/ultimate load for the beams because there was no inclusion of steel fibre term in the equation; and the indirect use of design average tensile strength and angle between member axis and diagonal crack to account for steel fibre factors have no reasonable effect on the beams’ shear strength/ultimate load. Al- Ta’an and Al - Feel’s (1990) lower prediction of the beams’ shear strength/ultimate load was because it indirectly used the product of the post cracking strength (σ pc ) and the area through which the steel fibres act to account for the steel fibre’s topology in the equation. Ashour et al. (1992) underestimated the beam’s shear strength/ultimate load because it used SFRC beams’ data to find the constants in the modified Zsutty and ACI