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Journal articleZahra F, Málaga-Chuquitaype C, 2025,
Hazard-consistent performance comparison of ASCE and Eurocode-compliant steel moment frames
, Engineering Structures, Vol: 326, ISSN: 0141-0296Seismic design codes are fundamental to the provision of safe infrastructure in earthquake-prone regions. At the moment of writing this paper, the European standard for seismic design (Eurocode 8) is in its final voting phase after undergoing important changes. This paper evaluates the consequences of the changes introduced in the upcoming Eurocode 8 against its current version and its American counterpart using a fair and hazard-consistent comparative framework. To this end, 16 steel moment resisting frames of different geometries are designed in accordance with each code. The resulting 48 frames are subjected to a series of 596 strong ground-motions carefully selected to be consistent with their design hazard, and the outcomes of these extensive analyses are presented as structural demand hazard curves for peak drifts and residual deformations. Our results reveal that, when assessed from a hazard-consistent perspective, European designs remain over-conservative in comparison with the designs adhering to the American standards, which are also perceived to be clearer and simpler, despite the important changes introduced in the new version of Eurocode 8. Our results also stress in quantifiable terms the marked limitations of current prescriptive design codes to guarantee reasonably similar demands are experienced by structures designed to the same level of performance requirement.
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Journal articleKyvelou P, Hong W, Zhang R, et al., 2025,
Mechanical properties and microstructure of wire laser metal deposited austenitic stainless steel
, Materials and Design, Vol: 250, ISSN: 0264-1275Laser metal deposition (LMD) is a metal 3D printing method that enables the efficient and cost-effective production of large-scale components, rendering it increasingly attractive for civil engineering applications. However, the scarcity of data and lack of knowledge of the material response and geometric variability of LMD steels is inhibiting adoption of this manufacturing method in the construction industry. To address this, a comprehensive experimental investigation into the geometry, mechanical properties and microstructural characteristics of LMD plates made from ER 308LSi stainless steel has been carried out and is presented herein. Laser scanning, tensile testing and microstructural analyses were conducted on a series of coupons of different thicknesses (2 mm and 8 mm), printing strategies, surface conditions and orientations. The results indicated low geometric irregularity, with both as-built and machined coupons displaying nearly identical mechanical properties. The thinner specimens had lower strengths, mainly attributed to their larger grain sizes. Significant anisotropy was observed from the mechanical tests on the thinner specimens, explained by a strong crystallographic texture observed in the microstructure. Overall, the examined material exhibited good mechanical behaviour and geometric consistency. Finally, a constitutive modelling approach previously applied to wire arc additively manufactured (WAAM) stainless steel was successfully adapted to characterise the anisotropic behaviour of LMD stainless steel in both the elastic and inelastic material ranges. The findings highlight the potential for using LMD in construction, offering a viable means of fabricating large-scale metal components with sound mechanical performance.
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Book chapterZhang R, Liang Z, Gardner L, et al., 2025,
Material and hybrid connection behaviour of a new nickel-free stainless steel at elevated temperatures
, Engineering Materials Structures Systems and Methods for A More Sustainable Future, Pages: 541-546A new nickel-free austenitic stainless steel EN 1.4678 (Forta H500) with excellent corгоsion resistance and significant strain hardening has been recently developed, but its elevated temperature behaviour has yet to be investigated. This paper reports an experimental study into the material properties of EN 1.4678 stainless steel at elevated temperatures. 22 coupons were extracted from 6 mm EN 1.4678 stainless steel plates and tested to failure at temperatures up to 1000°C. Elevated temperature reduction factors for the key material properties were derived and compared to corresponding factors for stainless steel specified in existing standards. The average experimentally derived reduction factors and the Ramberg-Osgood material model for stainless steel were applied in the FE modelling of hybrid carbon steel-stainless steel end-plate connections in fire, with a view to exploiting the excellent elevated tempera-ture behaviour of stainless steel to improve the response of connections in steel framed structures in fire.
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Journal articleYang J, Wadee MA, Gardner L, 2025,
Strengthening of steel I-section beams by wire arc additive manufacturing – concept and experiments
, Engineering Structures, Vol: 332, ISSN: 0141-0296An experimental investigation to assess the major-axis flexural behaviour of 10 hot-rolled steel I-sectionbeams, strengthened by the addition of material through wire arc additive manufacturing (WAAM) and testedunder either four-point or three-point bending conditions, is presented in this study. The ability of WAAM topre-camber hot-rolled steel I-section beams, as well as to enhance their bending moment resistance and initialelastic stiffness, has been demonstrated. The geometry of the strengthened beam specimens, including theinitial imperfections and pre-camber, were obtained by means of 3D laser scanning. Complementary materialtesting was conducted to obtain the mechanical properties of both the hot-rolled and WAAM steel undermonotonic tensile loading. The experimental results showed that significant pre-cambers of approximately1/200 of the span of the beam could be achieved with only a 2.6% increase in mass. Moreover, increasesof between 11.5% and 33.2% in the ultimate bending moment resistance, and increases of between 8.7%and 35.9% in the initial stiffness, were achieved for increases in mass of between just 2.6% and 12.3%. Thepresented WAAM-strengthening approach can be employed for the strengthening, repair and retrofittingof steel beams in service, as well as for the fabrication of hybrid steel members with improved flexuralbehaviour in new structures.
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Conference paperNayel AG, Málaga-Chuquitaype C, Macorini L, 2025,
Mesoscale Simulation of Unreinforced Masonry Walls to Blast Loads
, Pages: 404-416, ISSN: 2366-2557Masonry is a composite anisotropic material characterised by a quasi-brittle response. A realistic representation of various complex local phenomena, such as brick sliding and separation, is needed to accurately model masonry structures, especially when subjected to extreme actions, like blast loads generated from malicious or accidental explosions. Since mortar layers and brick-mortar interfaces act as weak planes where cracks initiate and propagate, they control the ultimate response of unreinforced masonry (URM). For these reasons, a detailed mesoscale modelling approach that considers the characteristics of the brick-mortar interfaces is used in this study to investigate the response of URM walls under blast loads. The influence of various interface parameters, brick-unit characteristics, blast-load intensity, and boundary conditions is examined through parametric and sensitivity analyses. It was found that friction between brick units is the most critical characteristic for accurately modelling the interface between units. The outputs of this study will help better understand the behaviour of URM structures under blast loads, leading to improved design of appropriate protective measures.
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Book chapterCabrera M, Theofanous M, Zhang R, et al., 2025,
Behaviour and design of stainless steel lap joints under high loading rates
, Engineering Materials Structures Systems and Methods for A More Sustainable Future, Pages: 565-570Stainless steel is an attractive material for exposed structural elements due to its durability and aesthetic appeal. As part of a larger project investigating the enhancement of robustness of steel frames via the use of ductile stainless steel connection components, this study focuses on the structural behavior of stainless steel lap joints under loading rates likely to occur during the progressive collapse of a structure. A total of 21 experimental tests on lap joints, comprising 4 static and 17 at loading speeds ranging between 4 and 11mm/sec, have been conducted and are reported herein, complementing previously reported static tests on similar specimens. The investigated failure modes include net section fracture and bearing failure, whilst the materials considered include $355 carbon steel, EN 1.4307 stainless steel and the novel nickel-free high strength grade EN 1.4678. Auxiliary material coupon test results at various strain rates are also reported to facilitate the discussion of the experimental results. Contrary to carbon steel, where increasing strain rates lead to an enhancement of the ultimate tensile strength, for the stainless steels considered herein a small but consistent reduction in ultimate strength is observed at moderate strain rates (1/s 10/s) followed by an enhancement at high strain rates. This is observed for the experimental tests on the lap joints reported herein. In all cases the ductility of the stainless steel specimens, albeit reduced with increasing strain rates, is significantly higher than that of their carbon steel counterparts.
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Conference paperZhang Y, Lavan O, Malaga-Chuquitaype C, 2025,
Mixed Lagrangian Formalism and Optimization of Inerter-Based Energy Harvesting Devices
, 3rd International Workshop on Energy Based Seismic Engineering-IWEBSE, Publisher: SPRINGER INTERNATIONAL PUBLISHING AG, Pages: 385-399, ISSN: 2366-2557 -
Journal articleBicer M, Phillips ATM, Melis A, et al., 2024,
Generative adversarial networks to create synthetic motion capture datasets including subject and gait characteristics
, Journal of Biomechanics, Vol: 177, ISSN: 0021-9290Resource-intensive motion capture (mocap) systems challenge predictive deep learning applications, requiring large and diverse datasets. We tackled this by modifying generative adversarial networks (GANs) into conditional GANs (cGANs) that can generate diverse mocap data, including 15 marker trajectories, lower limb joint angles, and 3D ground reaction forces (GRFs), based on specified subject and gait characteristics. The cGAN comprised 1) an encoder compressing mocap data to a latent vector, 2) a decoder reconstructing the mocap data from the latent vector with specific conditions and 3) a discriminator distinguishing random vectors with conditions from encoded latent vectors with conditions. Single-conditional models were trained separately for age, sex, leg length, mass, and walking speed, while an additional model (Multi-cGAN) combined all conditions simultaneously to generate synthetic data. All models closely replicated the training dataset (<8.1 % of the gait cycle different between experimental and synthetic kinematics and GRFs), while a subset with narrow condition ranges was best replicated by the Multi-cGAN, producing similar kinematics (<1°) and GRFs (<0.02 body-weight) averaged by walking speeds. Multi-cGAN also generated synthetic datasets for three previous studies using reported mean and standard deviation of subject and gait characteristics. Additionally, unseen test data was best predicted by the walking speed-conditional, showcasing synthetic data diversity. The same model also matched the dynamical consistency of the experimental data (32 % average difference throughout the gait cycle), meaning that transforming the gait cycle data to the original time domain yielded accurate derivative calculations. Importantly, synthetic data poses no privacy concerns, potentially facilitating data sharing.
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Journal articleShehzad MK, Forth JP, Nikitas N, et al., 2024,
Predicting the influence of restraint on reinforced concrete panels using finite element models developed from experimental data
, MECHANICS OF ADVANCED MATERIALS AND STRUCTURES, Vol: 31, Pages: 7655-7669, ISSN: 1537-6494- Cite
- Citations: 1
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Journal articleAltai Z, Hayford CF, Phillips A, et al., 2024,
Lower limb joint loading during high-impact activities: implication for bone health
, JBMR Plus, Vol: 8, ISSN: 2473-4039Osteoporosis results in low-trauma fractures affecting millions globally, in particular elderly populations. Despite the inclusion of physical activity in fracture prevention strategies, the optimal bone-strengthening exercises remain uncertain, highlighting the need for a deeper understanding of lower limb joint loading dynamics across various exercise types and levels. This study examines lower limb joint loading during high-impact exercises across different intensities. A total of 40 healthy, active participants were recruited (mean ± SD: age of 40.3 ± 13.1 years; height 1.71 ± 0.08 m; and mass 68.44 ± 11.67 kg). Motion capture data and ground reaction forces of six different exercises: a self-selected level of walking, running, counter-movement jump, squat jump, unilateral hopping, and bilateral hopping were collected for each participant. Joint reaction forces were estimated using lower body musculoskeletal models developed in OpenSim. Running and hopping increased joint forces compared to walking, notably at the hip (83% and 21%), knee (134% and 94%), and ankle (94% and 77%), while jump exercises reduced hip and ankle loading compared to walking (36% and 19%). Joint loading varied with exercise type and intensity with running faster increasing forces on all joints, particularly at the hip. Sprinting increased forces at the hip but lowered knee and ankle forces. Higher jumps intensified forces on all joints, while faster hopping reduced forces. The wide variation of lower limb joint loading observed across the exercises tested in this study underscores the importance of implementing diverse exercise routines to optimize overall bone health and strengthen the musculoskeletal structure. Practitioners must therefore ensure that exercise programs include movements that are specifically suitable for their intended purpose.
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