Surface Rupture Research Articles

The role of inherited structural anisotropies during co-seismic surface faulting: the Pescopagano fault case study (Irpinia seismogenic area, Southern Italy)

Co-seismic failure can occur on newly formed or on inherited structures. However, understanding their surface pattern is challenging when pre-existing structural anisotropies control rupture propagation. We focus here on the Pescopagano Fault (PF), considered part of the extensional fault system that ruptured during the 1980, Mw 6.9 earthquake in Southern Italy. Although the mainshock fault (Irpinia Fault) produced ∼ 40 km of NW-SE trending ground ruptures, these were not observed on a buried antithetic fault located to the northeast of the main fault and defined solely by seismological data. The PF studied here is part of an exposed fault array that spatially coincides with the trace of the antithetic fault. To better assess existing seismotectonic models for the Irpinia fault system, we investigated: i) whether ground ruptures occurred on the PF during past earthquakes, and ii) to what degree surface and deep faults are linked. Paleo-seismological trenches document that the PF has not released surface-rupturing earthquakes during the last ∼ 13-20 ka. Structural data suggest that the PF developed to accommodate the relaxation of a Pliocene thrust-fold system after the demise of thrusting. Results of this work highlight that the PF may be an inherited Pliocene or Early Pleistocene structure that does not reach the ∼ 10-15 km seismogenic depth typical of this region. In this scenario, the upward propagation of the antithetic fault from seismogenic depths towards the surface during a 1980-type earthquake may be impeded by a mélange layer developed during the growth of the Southern Apennines thrust belt and interposed between the deep antithetic fault and the upper crustal faults. We cannot exclude, however, that the PF may be activated during very large but infrequent and non-characteristic earthquakes on the Irpinia fault system.

The Postseismic Deformation of the 6 July 2019 Mw 7.1 Ridgecrest Earthquake from Burst Overlap Interferometry, InSAR, and GNSS

Abstract The July 2019 Ridgecrest earthquake sequence consists of an Mw 6.4 foreshock and an Mw 7.1 mainshock, which ruptured a complex set of orthogonal faults in the eastern California shear zone. We measure the co- and postseismic deformation associated with this sequence using the Burst Overlap Interferometry (BOI) technique in addition to the commonly used Interferometric Synthetic Aperture Radar (InSAR). The BOI technique, which provides displacement in the satellite’s along-track direction, offers important information on the postseismic deformation that cannot be measured by traditional InSAR and is only sparsely measured by the Global Navigation Satellite System networks. The BOI data reveal up to 4 cm displacement in the along-track direction, 10 km north of the northern tip of the seismic rupture, and up to 3 cm displacement along the coseismically active faults. These results rule out the possibility of significant shallow afterslip near the mainshock hypocenter, suggesting that the previously suggested poroelastic rebound is likely to be the cause for the significant postseismic line of sight deformation near the mainshock rupture. Based on the aftershocks’ moment tensor distribution, surface rupture, and simple forward modeling, we propose that the postseismic deformation north of the Ridgecrest rupture is caused by an aseismic slip along a north-trending normal fault of the Ridgecrest rupture that was induced by the Ridgecrest earthquake. Furthermore, we observed that both deformation and seismic activity decay slower over time as the distance from the Coso geothermal area increases. This decay is influenced by the mechanical properties of the crust, which are affected by the increased heat flow at Coso and thus suppress deformation and seismicity, ultimately controlling their temporal evolution.

Explicit Peck formula applied to ground displacement based on an elastic analytical solution for a shallow tunnel

Explicit Peck formula applied to ground displacement based on an elastic analytical solution for a shallow tunnel

Integrated proteome and pangenome analysis revealed the variation of microalga Isochrysis galbana and associated bacterial community to 2,6-Di-tert-butyl-p-cresol (BHT) stress.

The phenolic antioxidant 2,6-Di-tert-butyl-p-cresol (BHT) has been detected in various environments and is considered a potential threat to aquatic organisms. Algal-bacterial interactions are crucial for maintaining ecosystem balance and elemental cycling, but their response to BHT remains to be investigated. This study analyzed the physiological and biochemical responses of the microalga Isochrysis galbana and the changes of associated bacterial communities under different concentrations of BHT stress. Results showed that the biomass of I. galbana exhibited a decreasing trend with increasing BHT concentrations up to 40mg/L. The reduction in chlorophyll, carotenoid, and soluble protein content of microalgal cells was also observed under BHT stress. The production of malondialdehyde and the activities of superoxide dismutase, peroxidase, and catalase were further determined. Scanning electron microscopy analysis revealed that BHT caused surface rupture of the algal cells and loss of intracellular nutrients. Proteomic analysis demonstrated the upregulation of photosynthesis and citric acid cycle pathways as a response to BHT stress. Additionally, BHT significantly increased the relative abundance of specific bacteria in the phycosphere, including Marivita, Halomonas, Marinobacter, and Alteromonas. Further experiments confirmed that these bacteria had the ability to utilize BHT as the sole carbon resource for growth, and genes related to the degradation of phenolic compounds were detected through pangenome analysis.

Rupture process of the 2019 Mw 6.8 Davao Del Sur earthquake, Philippines from geodetic and seismic data

Because of its complex tectonic setting, the Philippines experiences vigorous seismic activity. On December 15, 2019, an Mw 6.8 earthquake struck Davao del Sur, the Philippines, severely damaging infrastructure and adversely affecting the population. In this study, we used Interferometry Synthetic Aperture Radar (InSAR) and teleseismic broadband data to explore the earthquake’s source parameters, rupture process, and tectonic characteristics through a Bayesian modeling approach and Coulomb stress analysis. An analysis of InSAR suggested that the mainshock occurred on an NW–SE oriented single plane within the Cotabato fault system, with the Makilala-Malungon fault being the causative fault. The Joint inversion revealed that the rupture initiated in the middle crust (depth: approximately 16.5 km), exhibiting a blind, left-lateral strike-slip fault rupture propagation with minimal reverse slip and no surface rupture. The slip was concentrated in a distinct asperity spanning a depth of 3–24 km, with the peak slip reaching approximately 1.8 m. The source time function of this event indicated a single pulse with a total source duration of approximately 17 s. The static stress drop value was low, which may be related to the brittle condition of the crust. Coulomb stress changes calculations suggested earthquake risk in the future.

The Influence of Fault Geometrical Complexity on Surface Rupture Length

AbstractPropagating earthquakes must overcome geometrical complexity on fault networks to grow into large, surface rupturing events. We map step‐overs, bends, gaps, splays, and strands of length scales ∼100–500 m from the surface ruptures of 31 strike‐slip earthquakes, recording whether ruptures propagated past the feature. We find that step‐overs and bends can arrest rupture and develop a statistical model for passing probability as a function of geometry for each group. Step‐overs wider than 1.2 km, single bends larger than 32°, and double bends larger than 38° are breached by rupture half of the time. ∼20% of the ruptures terminate on straight segments. We examine how the distribution of geometrical complexity influences surface rupture length, inferring an exponential relationship between rupture length and event probability. Our findings support that geometrical complexity helps limit the size of large events and provide insights into the competition between energy supply and dissipation during rupture propagation.

Influence of velocity pulse directivity on seismic response of cross-fault bridges

Pulse-type ground motions have special destructive effects on structures, and directivity is one of the fundamental characteristics of velocity pulses. In this paper, the impact of the velocity pulse directivity of seismic motions on both sides of the fault on the seismic response of fault-crossing bridges was quantified using the original records from the Chi-Chi earthquake in Taiwan. First, an automatic baseline correction method was applied to restore the permanent ground displacement, and the direction corresponding to the strongest pulse energy on both sides of the fault was identified based on continuous wavelet transformation. On this basis, the variability of the peak intensity of ground motions on the hanging wall and footwall in different directions, as well as the differences in pulse characteristics between the strongest pulse component and the two initial horizontal components, were analysed. Finally, a typical 5 × 30 m continuous girder bridge was considered as the research object to reveal the influence of the velocity pulse directivity on the seismic response of key parts on both sides of the fault. The results showed that the variability in the peak ground-motion intensity on the hanging wall of the fault was higher than that on the footwall. The displacement variability was up to 863 %, velocity was 262 %, and acceleration was 124 %. The pulse characteristics of the strongest pulse component were stronger than those of the parallel and vertical fault components, and its acceleration, velocity, and displacement response spectra were larger. The amplification effects of the velocity pulse directivity on the transverse bending moment, longitudinal bending moment, and torque of the pier bottom reached 1.3, 1.1, and 1.6, respectively. However, the amplification effect of the velocity pulse directivity on the relative displacement of the pier top, displacement of the main beam, and displacement of the bearing was more than 1.6 times, which was more significant than the internal force of the pier bottom.

Analytical solution of ground vibration of a half-space induced by sub- and super-critical harmonic moving loads: Theory and application

This paper presents an analytical solution to the ground vibration of a half-space subjected to sub- and super-critical moving loads oscillating with the frequency f0 and distributed in different forms. By applying the contour integral combined with the residue theorem, the approximate values of the integrals for the ground response are determined, with a rigorous rationale provided for the exclusive consideration of the Rayleigh waves on the ground. The validity of the present solutions is verified against existing solutions, including Auersch's. Through the parametric analysis, it is observed that the frequency f0 of dynamic loading of the vehicle exhibits significant influence on the critical speed, the magnitude of ground vibrations and their rate of attenuation. In addition, the effect of rail irregularity on the ground vibration was included in some applications of the present theory for high-speed trains under the sub-and super-critical speeds with respect to the Rayleigh waves speed. It was shown that track irregularity can largely amplify the velocity and acceleration responses of the ground, albeit exerting a comparably little effect on the ground displacement. Besides, resonant vibrations are likely to occur when the train is accelerated to the critical speed of the soil.

Constitutive Damage Model for Rubber Fiber-Reinforced Expansive Soil under Freeze-Thaw Cycles.

To elucidate the degradation mechanism of expansive soil-rubber fiber (ESR) under freeze-thaw cycles, freeze-thaw cycle tests and consolidated undrained tests were conducted on the saturated ESR. The study quantified the elastic modulus and damage variables of ESR under different numbers of freeze-thaw cycles and confining pressure, and proposed a damage constitutive model for ESR. The primary findings indicate that: (1) The effective stress paths of ESR exhibit similarity across different numbers of freeze-thaw cycles, the critical stress ratio slightly decreased by 8.8%, while the normalized elastic modulus experienced a significant reduction, dropping to 42.1%. (2) When considering the damage threshold, the shear process of ESR can be divided into three stages: weak damage, damage development, and failure. As strain increases, the microdefects of ESR gradually develop, penetrating macroscopic cracks and converging to form the main rupture surface. Eventually, the damage value reaches 1. (3) Due to the effect of freeze-thaw cycles, initial damage exists for ESR, which is positively correlated with the number of freeze-thaw cycles. The rubber fibers act as tensile elements, and the ESR damage evolution curves intersect one after another, showing obvious plastic characteristics in the late stage of shear. (4) Confining pressure plays a role in limiting the development of ESR microcracks. The damage deterioration of ESR decreases with an increase in confining pressure, leading to an increase in ESR strength. (5) Through a comparison of the test curve and the theoretical curve, this study validates the rationality of the damage constitutive model of ESR under established freeze-thaw cycles. Furthermore, it accurately describes the nonlinear impact of freeze-thaw cycles and confining pressure on the ESR total damage.

Sub‐Pixel Displacement Estimation With Deep Learning: Application to Optical Satellite Images Containing Sharp Displacements

AbstractOptical image correlation is a powerful method for remotely constraining ground movement from optical satellite imagery related to natural disasters (e.g., earthquakes, volcanoes, landslides). This approach enables the characterization, and identification of the causal factors and mechanisms underlying such processes. By employing sub‐pixel correlation algorithms, one can obtain highly accurate (m‐to‐cm level) displacement fields at high spatial resolution (dm‐to‐cm) by comparing satellite images acquired before and after a period of movement. However, this method generally assumes a homogeneous translation of all pixels within a given correlation window, which will lead to biased estimates of ground displacement if the real case is not well represented by such a simplification, especially when resolving ground displacements next to sharp gradients in displacement, such as those found in the near‐field of earthquake surface ruptures. In this paper, we present an innovative deep learning method estimating sub‐pixel displacement maps from optical satellite images for the retrieval of ground displacement. From the generation of a realistic simulated database, comprising Landsat‐8 satellite image pairs containing simulated sub‐pixel shifts and sharp discontinuities, we develop a Convolutional Neural Network able to retrieve sub‐pixel displacements. The comparison to state‐of‐the‐art correlation methods shows that our pipeline significantly reduces by 32% the estimation bias around fault ruptures, leading to more accurate characterization of the near‐field strain in surface rupturing earthquakes. Application of our model to the 2019 Ridgecrest earthquake demonstrates the ability of our model to accurately and quickly resolve ground displacement using real satellite images. Code is made available at https://gricad‐gitlab.univ‐grenoble‐alpes.fr/montagtr/cnn4l‐discontinuities.

Probabilistic back analysis of reservoir landslide considering hydro-mechanical coupled observations

Precisely assessing statistical parameters to characterize spatial soil variability presents a significant challenge in probabilistic slope stability analysis, primarily due to inherent soil uncertainties and limited field-specific data. Probabilistic back analysis, recognized as an effective and reliable technique, offers a rational method for utilizing observational data to invert parameters. Nevertheless, previous investigations into parameter inversion for slope stability analysis have seldom considered the coupling of hydro-mechanical characteristics in reservoir landslides. This study proposes a novel integrated Bayesian framework to perform back analysis of reservoir landslides, incorporating the spatial variability of hydro-mechanical parameters. Within this framework, a hypoplastic constitutive model is developed to characterize the step-like deformation of the reservoir slope. The posterior knowledge of the saturated permeability coefficient and shear strength parameters is obtained by collecting field monitoring data of the underground water level and ground displacement. The Maliulin landslide, located in the Three Gorges Reservoir area of China, is used as an illustrative example to validate the proposed framework through back analysis of spatially variable soil parameters and probabilistic stability analysis. The results demonstrate that the proposed Bayesian updating framework significantly reduces the uncertainties associated with statistical values of soil parameters, providing more accurate and reasonable updated soil parameters for probabilistic slope stability analysis.

Experimental study on mechanical behavior and countermeasures of mountain tunnels under strike-slip fault movement

In the seismic mountainous regions such as western China, it is usuallly inevitable to construct tunnels near active fault zones. Those fault-crossing tunnel structures can be extremely vulnerable during earthquakes. Extensive experimental studies have been conducted on the response of continuous mountain tunnels under reverse and normal fault movements, limited experimental investigations are available in the literatures on mountain tunnels with special structural measures crossing strike-slip faults. In this study, a new experimental facility for simulating the movement of strike-slip fault was developed, accounting for the spatial deformation characteristics of large active fault zones. Two groups of sandbox experiment were performed on the scaled tunnel models to investigate the evolution of ground deformation and surface rupture subjected to strike-slip fault motion and its impact on a water conveyance tunnel. The nonlinear response and damage mechanism of continuous tunnels and tunnels incorporated with specially designed articulated system were examined. The test results show that most of slip between stationary block and moving block occurred within the fault core, and significant surface ruptures are observed along the fault strike direction at the fault damage zone. The continuous tunnel undergoes significant shrinkage deformation and diagonal-shear failure near the slip surface and resulted in localized collapse of tunnel lining. The segments of articulated system tunnel suffer a significant horizontal deflection of about 5°, which results in opening and misalignment at the flexible joint. The width of the damaged zone of the articulated system tunnel is about 0.44 to 0.57 times that of the continuous tunnel. Compared to continuous tunnels, the articulated design significantly reduces the axial strain response of the tunnel lining, but increases the circumferential tensile strain at the tunnel crown and invert. It is concluded that articulated design provides an effective measure to reduce the extent of damage in mountain tunnel.

Integration of multiple observations for validation of mechanisms of earthquake-triggered groundwater level Anomalies: 2016 Taiwan Meinong earthquake

This study analyzes multi-depth groundwater level data and integrated observation data to validate the previously proposed mechanisms of hydrological anomalies triggered by the 2016 M6.4 Meinong earthquake in Taiwan. The main influence area was northwest of the epicenter, which may be due to the blind fault rupture, intensity distribution, and hydrogeological properties. The step changes in groundwater level do not fit the concept of epicentral distance, static stress–strain theory, or the focal mechanism. The distribution of step changes in groundwater level have a pattern similar to that of horizontal peak ground velocity. The results imply that these changes may be driven by dynamic stress–strain, instead of static stress–strain. The minimum horizontal peak ground velocity and acceleration of the Meinong earthquake, which induced obvious step changes in groundwater level and soil liquefaction, are provided. The pressure dissipation ability of an aquifer (e.g., transmissivity) may affect the persistence of groundwater responses. Four wells located near the surface rupture area, which has cemented or partial cemented geological material, showed an obvious step decrease in the groundwater level at a deep depth and all wells showed an increase in the groundwater level at a shallow depth. These decreases and increases of the groundwater level at different depths have different mechanisms, which are discussed in this study. The integrated observations made during the Meinong earthquake show that ground motion and the hydraulic properties might be important factors in hydrological anomalies. The results of this study are an important reference for further studies on earthquake hydrology.

Investigating the impact of urban development on the activation of a paleolandslide. A case study from Pissouri, Cyprus

The present study investigates the reactivation of a paleolandslide due to the expansion of a community in an area covered by plastic Pliocene marls in the southwestern part of Cyprus. The landslide, which takes place in an area with gently sloping ground and relatively shallow water table, affects more than 100 residential buildings. In the context of the study, building damages and ground surface ruptures were mapped through field work campaigns. Remote sensing data from InSAR (Interferometric Synthetic Aperture Radar) analysis were evaluated in conjunction with available geological, geotechnical and hydrogeological data. Subsequently, the landslide was backanalyzed using the finite element method to examine possible failure mechanism scenarios and shed light on the influence of potential triggering factors. The results indicate that the paleolandslide has been almost fully reactivated, with the main cause of the reactivation being the rising of the phreatic water table due to long-term discharges of wastewater through the absorption pits of the residential developments. The water table rise was further amplified by rainwater infiltration during rainy years. According to the backanalysis results, the slip surface follows the bedding planes of weak marl horizons with residual friction angle of the order of 10°.

Surface ruptures of the 2022 Guanshan-Chihshang earthquakes in central Longitudinal Valley area, eastern Taiwan

AbstractThe Mw 6.4 and 6.8 Guanshan-Chihshang earthquakes occurred on 17 and 18 September 2022 resulted in prominent surface ruptures within the Longitudinal Valley in eastern Taiwan, particularly along the Yuli fault. Approximately 18 h after the mainshock, we began to document the surface rupture near Yuli Town. Our result suggests the surface rupture formed a confined single left-lateral trace in the town of Yuli, characterized by a series of en échelon right-stepping left-lateral faulting geometry. The rupture of 2022 roughly matches the locations of 1951 surface ruptures inside Yuli Town, with a similar amount of left-lateral cross-fault displacement. North and South of the Yuli residential area, we identified several sections of the surface rupture distributed in the water-saturated paddy fields. The maximum left-lateral displacement recorded across the rupture can reach 1.4 m just south of Yuli, with the fault scarp resembling a high-angle west-dipping fault geometry. In addition to the co-seismic surface ruptures, our repeating cross-fault measurements show significant post-seismic shallow after-slip along the Yuli fault. The amount of post-seismic deformation within 3 months after the mainshock is close to, or even higher than the co-seismic cross-fault displacement, consistent with local witness accounts and post-event field photos which showed continuous damage and displacement of building floors and roads after the earthquake. Such shallow post-seismic slips were also observed along the main fault trace in the 2014 South Napa earthquake, and likely represent the shallow elastoplastic behavior of the sub-vertical fault in the young alluvial sediments.

Coseismic surface ruptures of 20 strike-slip earthquakes measured from geodetic imaging data

Observations of coseismic surface ruptures are widely used for examining faulting mechanics and kinematics, and in fault displacement hazard analysis. Here, first, we provide new remote sensing observations of 20 historic surface rupturing continental strike-slip earthquakes (6.1 ≤ Mw≤ 7.9). To measure the near-field surface deformation pattern, we have processed a range of raw radar and optical images from satellite and aerial platforms with pixel tracking techniques, and in two cases using standard interferometric synthetic aperture radar (InSAR). We provide a range of observations, including surface displacement maps that constrain at least the horizontal component of surface motion (2D), and for three events the full 3D components. Second, we provide strain invariants for each event, which includes the finite dilatational strain, strain magnitudes, the vorticity, and maximum shear strain. Third, we provide a total of 134 surface fault rupture traces that are mapped manually from the displacement maps. Finally, we provide 2648 measurements of coseismic horizontal fault-parallel surface fault slip that are measured objectively using swath profiles with a function fitting method that we have developed.

Multidisciplinary assessment of seasonal ground displacements at the Hatfield Moors gas storage site in a peat bog landscape

The study aims to analyse ground displacement conditions observed over an Underground Gas Storage (UGS) site located at Hatfield Moors (United Kingdom), with a focus on understanding its implications for decarbonization efforts. The location serves as an active onshore storage site and was used as an analogy to assess ground motion implications around Carbon Capture and Storage (CCS) by the British Geological Survey (BGS) as part of the SENSE (Assuring integrity of CO2 storage sites through ground surface monitoring) project. Given the value of continuous and real-time monitoring of ground movements induced by gas storage activities, the study leverages satellite Interferometric Synthetic Aperture Radar (InSAR) data to assess the environmental impact of UGS operations. Using free and open-source Sentinel-1 satellite data, ground motion patterns over Hatfield Moors are analysed, highlighting displacements ranging from − 5.0 to -10.0 mm/year within the peat bog. In addition, the Time Series (TS) of ground displacement from January 2018 to December 2022 reveals a seasonality in ground motion, with uplift observed in late winter and subsidence in late summer, showing a periodicity of approximately 1 year and a magnitude of +/-10.0 mm. Through in-depth analysis, the study highlights the need to understand the underlying causes of ground fluctuations at gas storage sites. This paper shows that InSAR has the versatility to integrate seamlessly with different monitoring tools and methodologies, opening avenues for comprehensive and holistic analyses. Cross-correlation analyses further elucidate temporal relationships between different datasets by evaluating InSAR time series, UGS injection/withdrawal data and piezometric data. This involves decomposing the TS into distinct components, including trend, seasonality and residuals. The case of Hatfield Moors shows a significant discrepancy between the UGS data and the InSAR TS, while also demonstrating a clear correlation between the groundwater data and the InSAR TS. By integrating insights from geology, hydrology and remote sensing technologies, the study navigates the complexities inherent in areas of overlapping phenomena. Accurate interpretation is essential for informed decision making, particularly at sites such as Hatfield Moors, where the convergence of natural peat motion and storage operations highlights the need for interdisciplinary analysis to understand the underlying causes of ground fluctuation.

Shallow crustal structure of the northern Longmen Shan fault zone revealed by a dense seismic array with ambient noise analysis

The Longmen Shan (LMS) fault zone located in the southwest of China is not only the boundary tectonic zone of the Tibetan Plateau and South China block, but also an important part of the north–south seismic belt of China. To investigate the detailed crustal structure of the LMS fault zone, we deployed a dense seismic array of 151 short-period temporary stations in its northern section from March 16 to April 6, 2023. Continuous vertical component ambient noise waveforms recorded by these stations were cross-correlated for all station pairs, enabling the extraction of Rayleigh wave phase velocity dispersion curves across periods ranging from 0.5 s to 6 s. We then inverted these data to derive the crustal shear wave velocity using direct surface wave tomography. Meanwhile, a linear sub-array consisting of 54 stations and crossing the surface rupture of the 2008 Wenchuan earthquake was used to image the fault structure by applying the Transmitted Surface Wave Reverse Time Migration method (TSW-RTM). The ambient noise tomography results show that strong lateral heterogeneity exists in the shallow crust in the study area, with a high shear velocity in the northwest and a low shear velocity in the southeast. The low shear velocity is generally distributed between the Yingxiu-Beichuan fault (YBF) and the Guanxian-Jiangyou fault (GJF). The results of TSW-RTM indicate that the Wenchuan-Maoxian fault (WMF) and the YBF are both characterized with a steep dip to the northwest. Our results could serve as the important basis for the study of segmentation characteristics of the LMS fault and seismic hazard preparation and mitigation.

Numerical investigation on a precast bridge using GPC and BFRP reinforcements subjected to cross-fault rupture and fling step excitation

This study investigates the seismic performances of a precast bridge made of geopolymer concrete (GPC) with fibre-reinforced polymer (FRP) reinforcements subjected to cross-fault ground motions. A numerical model was developed and verified against experimental results from a previous study and then used to evaluate the bridge's performances under earthquake excitations. The study found that a simplified model was able to reliably capture the failure pattern and displacement response of the bridge, reducing simulation time significantly. Additionally, the numerical results indicated the combination of torsional and flexural cracks was the primarily damage mode of the columns, which was not observed in the experimental test. This study also revealed that while the performances of the bridge using ordinary Portland cement (OPC) and GPC were similar under low ground excitations, GPC columns were more susceptible to brittle failure under higher ground excitations due to their brittleness. The use of FRP reinforcements led to similar displacement response as steel reinforcements under low ground displacement excitation, although severe flexural and shear damages on the column of Bent 2 were observed due to the lower elastic modulus and shear resistance of Basalt FRP material than steel. To address the disadvantages of brittle GPC and low-modulus of basalt FRP reinforcements, it is suggested to reinforce GPC with fibres and/or increase stirrup ratios if green GPC and corrosion-resistant basalt FRP reinforcements are used to construct bridges for seismic resistance.

Prediction of temperature and structural properties of fibre-reinforced polymer laminates under simulated fire exposure using artificial neural networks

Load-bearing fibre reinforced polymer laminates soften and decompose when exposed to high temperature fire which may cause significant deformation and weakening, ultimately leading to failure. A combined experimental and modelling study is presented to predict the fire structural survivability of laminates using artificial neural networks based on machine learning. Multiple experimental fire-under-tension load tests are performed under identical conditions to determine the average values and scatter to the surface temperatures, deformation rates and rupture times for an E-glass/vinyl ester laminate. A data-driven modelling strategy based on artificial neural networks is presented that can predict the temperatures and fire structural properties for the laminate when subject to combined fire exposure and tension loading. It is shown that the model gives excellent agreement to the measured surface temperatures, deformations, and time-to-failure of the laminate when exposed to one-sided heating at a constant heat flux. It is envisioned that the ANN based model could be used to assess the fire structural survivability of load-bearing composite structures exposed to fire.