Abstract
This study conducted experimental and analytical research to establish fatigue performance criteria for CFRP
reinforcements under flexural-tensile cyclic loading conditions. To investigate the influence of fiber-volume fraction on fatigue
behavior, additional fatigue tests were performed using specimens with a 60% fiber-volume fraction. The results were
incorporated into and calibrated within the fatigue limit curve proposed in previous studies, enhancing its reliability. The fatigue
test results indicated that higher fiber content reduced fatigue resistance under high load conditions, while it improved fatigue
resistance under low load conditions. This suggests that, under high load levels, the resin matrix primarily governs the response,
and early interfacial debonding between fibers and resin significantly affects fatigue resistance. In contrast, under low load
levels, the response remains within the elastic range of the resin, and the stiffness of the fibers becomes dominant. Based on
these findings, it is recommended to select an appropriate fiber-volume fraction depending on the applied load conditions during
the design phase. If selecting the optimal fiber-volume fraction is not feasible, adjusting it to approximately 50% is considered
suitable to ensure the required fatigue performance. In the analytical part of this study, D'Amore's fatigue life prediction model
was applied. However, the parameters proposed in the original study (α= 0.184, β= 0.200) resulted in an RMSE of
approximately 3.14, indicating that they did not adequately reflect the experimental results obtained in this study. Therefore,
following the parameter estimation procedure suggested in previous research, new parameters α= 08843, β = 0.2019 were
derived. These proposed parameters resulted in a 75.48% reduction in prediction error compared to the original parameters,
thereby improving the reliability of the constructed fatigue limit curve and enhancing its applicability in practical intends to
address them through continued research in the future.
Key Words
carbon fiber reinforced polymer; composite; fatigue; long-term performance
Address
Youngjun Bae: Department of Civil and Environmental Engineering, Gangneung Wonju National University,
7, Jukheon-gil, Gangneung-si, Gangwon-do, Republic of Korea
Sangmoon Lee: Institute of Smart Infrastructure, Gangneung Wonju National University,
7, Jukheon-gil, Gangneung-si, Gangwon-do, Republic of Korea
Namkyeong Lee: Department of Civil and Environmental Engineering, Gangneung Wonju National University,
7, Jukheon-gil, Gangneung-si, Gangwon-do, Republic of Korea
Wooyoung Jung: Department of Civil and Environmental Engineering, Gangneung Wonju National University,
7, Jukheon-gil, Gangneung-si, Gangwon-do, Republic of Korea
Abstract
The introduction of web openings in reinforced concrete (RC) beams to accommodate modern building utilities
often compromises their structural performance due to stress discontinuities and reduced stiffness. This study investigates a
novel hybrid strengthening approach combining strain-hardening cementitious composites (SHCC) with glass fiber-reinforced
polymer (GFRP) strips to enhance the capacity and ductility of beams with web openings. Nine beams were tested under various
configurations, including anchored and non-anchored systems with single and double strengthening layers. Results indicate
significant improvements in load-bearing capacity, crack control, and ductility for strengthened specimens, particularly in
configurations utilizing double-layer anchored strips. Beams strengthened with double-layer anchored configurations exhibited
the highest improvement in load-bearing capacity and crack control, achieving up to 82% enhancement in ultimate load. Finite
element modeling validated the experimental findings, enabling detailed parametric studies. The hybrid system demonstrates a
cost-effective and practical solution for retrofitting RC beams, paving the way for advanced rehabilitation practices in structural
engineering.
Key Words
crack control; finite element analysis; glass fiber-reinforced polymer; load bearing capacity; strain
hardening cementitious composite; web openings
Jong Wan Hu: 1)Department of Civil and Environmental Engineering, Incheon National University, Incheon 22012, South Korea 2) Incheon Disaster Prevention Research Center, Incheon National University, Incheon 22012, South Korea
Abstract
In order to improve the assembly rate of cold-formed steel (CFS) housing structural systems, this paper proposes
two novel dry assembly forms for flange and web connections. Cyclic loading tests were conducted to investigate the effects of
the flanges and different connection methods on the failure mode, bearing capacity, stiffness, energy consumption and ductility
of the prefabricated CFS foamed concrete shear walls (PCFS-FCSWs). The findings indicated that the damage to the PCFS
FCSWs was predominantly concentrated in the web region between the vertical joints. The shear forces in the webs were
successfully transferred to the flanges via the connectors and bolts. The presence of flanges increased the compressive and
deformation capacity of the specimens, and delayed the degradation of stiffness. The bearing capacity of PCFS-FCSWs was
inferior to that of the cast-in-place wall, although their deformability and energy consumption were superior. Compared with the
web spliced specimen, the load-bearing capacity and total energy consumption of the specimen assembled with L-shaped
connectors increased by 22.8% and 50.4%, respectively. The finite element modelling (FEM) results demonstrated that the
minimum principal stress trace in the webs of PCFS-FCSWs was distributed along the diagonal. The stresses at the bottom of
the flanges were distributed parabolically and there was a shear lag effect. Finally, a simplified model for predicting the shear
bearing capacity of PCFS-FCSWs was proposed, considering the effects of cladding panels, flanges and assembly joints. The
findings provide valuable insights for the promotion and application of dry-assembled CFS composite walls in seismic zones.
Key Words
cold-formed steel; cyclic performance; dry assembled shear wall; finite element modelling; high-strength
foam concrete
Address
Zhiming Peng: 1)China-Pakistan Belt and Road Joint Laboratory on Smart Disaster Prevention of Major Infrastructures,
Southeast University, Nanjing 211189, China
2) School of Civil Engineering, Southeast University, No.2 Southeast University Avenue, Nanjing 211189, China
Xiaomeng Ding: 1)China-Pakistan Belt and Road Joint Laboratory on Smart Disaster Prevention of Major Infrastructures,
Southeast University, Nanjing 211189, China
2) School of Civil Engineering, Southeast University, No.2 Southeast University Avenue, Nanjing 211189, China
Zhifeng Xu: School of Civil Engineering and Architecture, Shandong University of Science and Technology, Qingdao 266590, China
Zhongfan Chen: 1)China-Pakistan Belt and Road Joint Laboratory on Smart Disaster Prevention of Major Infrastructures,
Southeast University, Nanjing 211189, China
2) School of Civil Engineering, Southeast University, No.2 Southeast University Avenue, Nanjing 211189, China
Jiankang Lin: 1)China-Pakistan Belt and Road Joint Laboratory on Smart Disaster Prevention of Major Infrastructures,
Southeast University, Nanjing 211189, China
2) School of Civil Engineering, Southeast University, No.2 Southeast University Avenue, Nanjing 211189, China
Abstract
The UOE manufacturing process is a widely utilized method for producing large-diameter steel pipes to meet the
growing global energy demands. In the final stage of UOE pipe forming, the multi-steps process of the expansion creates
overlap areas, leading to nonuniform distributions of residual stress, ovality, and plastic deformation along the pipe's
longitudinal direction. This study aims to analyze the effects of two critical expansion parameters—overlap length and
expansion ratio—on the structural performance of UOE pipes. A 3D finite element model of the UOE process was developed to
simulate the nonuniformities caused by overlap areas. The model was validated using equivalent plastic strain (PEEQ)
distributions from reference studies and employed to conduct collapse analyses using the Riks method. The findings suggest
that, although the overlap length has a relatively smaller effect on collapse performance compared to the expansion ratio, the
overlap areas exhibit significantly higher stress levels under external pressure. This highlights the importance of precise
parameter control to enhance pipeline reliability.
Key Words
collapse pressure; expansion ratio; ovality; overlap area length; pipe forming; UOE
Address
Dong-Won Kim: Department of Civil Engineering, Seoul National University of Science and Technology,
232 Gongneung-ro, Nowon-gu, Seoul 01811, Republic of Korea
Soo-chang Kang: Steel Structure Research Group, POSCO, 100 Songdogwahak-ro, Yeonsu-gu, Incheon, 21985, South Korea
Jiwoon Yi: Steel Structure Research Group, POSCO, 100 Songdogwahak-ro, Yeonsu-gu, Incheon, 21985, South Korea
Jin-Kook Kim: Department of Civil Engineering, Seoul National University of Science and Technology,
232 Gongneung-ro, Nowon-gu, Seoul 01811, Republic of Korea
Abstract
It is well-understood that various machine learning algorithms can present different performances in solving
complicated problems, and there are uncertainties in the machine learning-based predictions. This study proposes a stacking
based seismic-induced damage detection method to reduce the uncertainties related to training individual machine learning
models. To do so, three different machine learning models (i.e., support vector machine, K- nearest neighbor, and convolutional
neural networks) are employed as the first-level learners. Then, the results of these predictors are combined using a decision tree
algorithm as the meta-model. A series of 111 earthquake records, which were originally simulated/modified by the SAC project,
is used to generate the dataset. These records are uniformly scaled from 0.05 g to 1.60 g to provide a wide range of earthquake
intensities. The proposed framework uses a combination of feature extraction-based machine learning and deep learning models
to implement the damage detection procedure. Combining the capabilities of feature-based and deep learning algorithms
minimizes the errors related to relying on only one of these learning methods. Bayesian optimization algorithm was used in this
study to tune the hyperparameters of all classification learners. A one-story chevron-braced frame and a five-story concentric
braced frame structure are served to validate the proposed approach. Results show that the proposed technique increases the
accuracy and reliability of predicting the extent of damage compared to individual models.
Address
Ehsan Madani: Department of Civil Engineering, Kish International Branch, Islamic Azad University, Kish, Iran
Alireza Fiouz: 1)Department of Civil Engineering, Kish International Branch, Islamic Azad University, Kish, Iran
2)Department of Civil Engineering, Persian Gulf University, Bushehr, Iran
Davood Abdollahzadeh: 1)Department of Civil Engineering, Kish International Branch, Islamic Azad University, Kish, Iran 2)Department of Civil Engineering, Islamic Azad University, Pardis Branch, Tehran, Iran
Babak Aminnejad: 1)Department of Civil Engineering, Kish International Branch, Islamic Azad University, Kish, Iran
2) Department of Civil Engineering, Roudehen Branch, Islamic Azad University, Roudehen, Iran
Abstract
This study investigates the seismic performance of ConXL moment connections, focusing on the role of T-Stub
fragments configurations in enhancing structural behavior under cyclic loading. The original ConXL design prioritizes moment
transfer through bolts and collar components but lacks a protected area for plastic hinge formation, which is essential for energy
dissipation without damaging the Complete Joint Penetration (CJP) weld. This limitation can compromise the connection's
performance under seismic conditions. The revised system introduces T-Stub fragments, which modify the stress distribution
and moment-resisting behavior by adding stiffness and deformation capacity to the connection. This modification improves the
connection's resistance to seismic forces and enhances its endurance under cyclic loading. The T-Stub fragments serve two
primary functions: first, they guide the plastic hinge to a safer location, preventing plasticity in critical zones such as the beam
to-collar flanges welds, reducing the risk of brittle failure, and improving ductility. Second, they help the collar flanges transmit
stress caused by cyclic loading to the collar corners, optimizing stress distribution and increasing the connection's energy
dissipation capacity. The optimal model, TXL300-15, shows an 18% improvement in energy dissipation and a 24% increase in
ultimate moment capacity compared to the conventional ConXL connection with an RBS. These findings highlight the enhanced
seismic resilience, energy absorption, and structural stability of the modified ConXL connection, making it more effective at
resisting seismic forces.
Key Words
capacity; ConXL; energy dissipation; rotation; seismic; SMRF
Address
Waleed khaleel Nayel: 1)Department of Civil Engineering, College of Engineering, Karbala University, Karbala, Iraq
2)Civil Engineering Department, College of Engineering, University of Warith Al-Anbiyaa, Karbala, Iraq
Israa Hasan Nayel:1)Department of Civil Engineering, College of Engineering, Karbala University, Karbala, Iraq
2)Civil Engineering Department, College of Engineering, University of Warith Al-Anbiyaa, Karbala, Iraq
Ali Zohdi: Department of Civil Engineering, Tabriz Branch, Islamic Azad University, Tabriz, Iran
Ali Ghamari: Department of Civil Engineering, Il.C., Islamic Azad University, Ilam, Iran
