Cold-formed steel (CFS) bolted joints formed with back-to-back channel sections are widely used in portal frame construction due to their efficiency and ease of fabrication. However, the discrete force transfer between individual channels produces non-uniform stress distributions within the joint region, leading to localised stress concentrations, shear lag effects, bimoment-induced stresses due to restrained warping, and premature web buckling. These effects can reduce the moment capacity of typical joints by up to 40% compared with the nominal capacity of the connected members; however, this reduction is not explicitly addressed in current CFS design standards, including AISI S100, AS/NZS 4600, and EN 1993–1–3, which treat member and joint capacities independently. To address this gap, this paper presents a comprehensive experimental and parametric investigation to quantify the capacity reduction in CFS bolted joints and provide a reliable design method for practical applications. A detailed finite element (FE) model was first developed and validated against experimental results from CFS portal frame joint tests. Subsequently, an extensive parametric study comprising over 3400 FE simulations was performed to capture the influence of cross-sectional non-dimensional slenderness, as well as a wide range of geometric, material, and joint parameters. Based on these findings, a simplified design equation is proposed to enable reliable prediction of the reduced moment capacity of back-to-back channel bolted joints. The application of the proposed design equation is then verified against both numerical and experimental results of CFS frames, demonstrating excellent accuracy, with predictions within 1–3% of the actual capacities on average and coefficients of variation ranging from 0.06 to 0.09.

Existing structural design guidance for built-offsite cold-formed steel (CFS) panelised structures remains insufficient, particularly regarding robustness against disproportionate collapse following the accidental loss of vertical support. A significant knowledge gap exists regarding the specific resistance mechanisms of panelised CFS and the complex interactions between structural components. This paper presents the preliminary results from a full-scale test on CFS floor joist-to-wall stud subassembly subjected to simulated support removal. Based on the experimental results, the tie force developed in the specimen is found to adhere to the design guidelines available for CFS panelised structures. This research represents a critical step in a wider initiative to develop validated modelling idealisations and robust design guidelines, ultimately addressing the current lack of standardisation and facilitating the safe, widespread adoption of CFS panelised systems.

It is challenging to predict the precise location and severity of flood events, which can cause major disturbance to different public services, such as disruption to and the closure of critical transportation infrastructure. Therefore, approaches to enhance the resilience of these infrastructures are required. Serious games are new computing tools that have been applied in various fields with a combination of gameplay, learning and training. However, the application of serious games in intelligent transportation systems remains underutilized. As a result, the concept of a serious game is developed in this study to significantly improve transportation infrastructure resilience in an example of a flooding event. The serious game concept presented in this paper is being developed as part of the H2020-funded PRECINCT project (www.precinct.info).

Cold-formed steel (CFS) unlipped channel sections are the most commonly used bearers in panelised buildings, supporting gravity loads from the floor panels. The bearers are typically laterally retrained at floor joist locations and vertically supported on CFS-lipped channel studs. Existing web-crippling and combined web-crippling-bending tests of bearers employ laterally and torsionally stable test setups formed by two identical channel sections connected either toe to toe in a box-beam arrangement or back-to-back and three-point bending static loading applied through the section's shear center (i.e., the loading induces no torsional moment to the sample), without employing any lateral restraint to the sample. No research has been conducted thus far to investigate CFS unlipped channel bearer sections' combined web-crippling and bending behaviour in stud(s) or single panel vertical support removal static loading scenarios. This research experimentally and analytically investigated the combined web-crippling and bending behaviour of CFS unlipped channel bearers with structural arrangements similar to CFS panelised buildings i.e., intermediate lateral restraints (representing floor-joists) and simply supported boundary conditions under stud vertical support removal static loading scenarios. The static loading circumstances consist of one stud (Case I), two studs (Case II), and three studs/single panel (Case III) vertical support removal. Twenty-four industry-standard bearers were tested with lateral restraint under Case I. Ninety-six parametric studies were conducted with finite element analysis models validated by testing under Cases I, II, and III. Results showed the bearers failed predominantly due to web-crippling with the interior one flange (IOF) and end one flange (EOF) mechanism being the most critical under Case I and III, respectively. Five different web-crippling equations in literature and web-crippling-bending interaction equations in Eurocode 3 (EC3) and AISI S100 were evaluated considering the above five different web-crippling capacities (developed based on static loading) and torsional moments (which the design codes do not mention). It was revealed that the EC3 and AISI interaction equations are unconservative when the torsional moment is excluded and over-conservative when the torsional moment is included. New characteristic nominal web-crippling-bending interaction ratios at IOF and modification factors to nominal EOF web-crippling capacities are proposed for the bearers' efficient design under stud(s) or single-panel vertical support removal static loading scenarios.

Reinforced concrete shear wall (RCSW) structures can provide significant confinement for TNT explosions occurring within them, ultimately resulting in significant structural damage. However, research remains limited regarding the influence of internal explosion (IE) TNT locations and quantities (masses) on blast wave propagation and the dynamic structural response of RCSWs. To address this research gap, a detailed numerical model was developed using LS-DYNA, calibrated and validated using experimental data from previous IE tests on a RCSW substructure. These new numerical methods were employed to systematically investigate the effects of varying TNT locations and masses on the propagation mechanisms and distribution patterns of blast waves, as well as on the peak displacements and damage levels of the RCSWs, with particular focus on the influence of the TNT movement perpendicular or parallel to the two opposing RCSWs on the IE loads. It was found that when the TNT was shifted perpendicular to the two opposing RCSWs, the IE loads on the RCSW farther from the TNT increased significantly, thereby amplifying its peak displacement. A new procedure was proposed for calculating a simplified uniformly distributed overpressure (UDOP) from IE loads, by which the simplified UDOP model of the RCSW substructure was subsequently developed to improve the computational efficiency. The simulated results indicated that the mean absolute errors of the peak displacements of the RCSWs for TNT masses of 253 g, 400 g, and 550 g predicted by the simplified UDOP model were 9.0 %, 14.9 %, and 8.8 %, respectively, whilst being 113 % more computationally efficient.

This paper presents experimental and numerical studies on the local stability and compression resistances of laser-welded stainless-steel T-section stub columns. A testing program was first conducted, including material coupon tests, residual stress measurements, and 20 stub column tests. The testing program was supplemented by a numerical modeling program, in which finite-element models were developed and validated against the test results. The finite-element models were afterward used to perform parametric studies to obtain additional numerical data. The test and numerical data were adopted to evaluate the main design rules in the American and European standards and the continuous strength method. The evaluation results indicate that the American and European standards yield conservative resistance predictions, especially for nonslender T-sections, owing to no consideration of material strain hardening, while the continuous strength method is shown to provide greatly improved design accuracy and consistency over the American and European standards.

This paper investigates the robustness of a single 3D volumetric corner-supported module made of square hollow-section (SHS) columns. Typically, the moment–rotation (M-θ) behaviour of connections within the module (intra-module) is assumed to be fully rigid rather than semi-rigid, resulting in inaccurate assessment (i.e., overestimated vertical stiffness) during extreme loading events, such as progressive collapse. The intra-module connections are not capable of rigidly transferring the moment from the beams to the SHS columns. In this paper, a computationally intensive shell element model (SEM) of the module frame is created. The M-θ relationship of the intra-module connections in the SEM is firstly validated against test results by others and then replicated in a new simplified phenomenological beam element model (BEM), using nonlinear spring elements to capture the M-θ relationship. Comparing the structural behaviour of the SEM and BEM, under notional support removal, shows that the proposed BEM with semi-rigid connections (SR-BEM) agrees well with the validated SEM and requires substantially lower modelling time (98.7% lower) and computational effort (97.4% less RAM). When compared to a BEM with the typically modelled fully rigid intra-module connections (FR-BEM), the vertical displacement in the SR-BEM is at least 16% higher. The results demonstrate the importance of an accurate assessment of framing rotational stiffness and the benefits of a computationally efficient model.

A novel investigation into the impact of the tower road-sign gantry and the tower shielding on double-decker buses and trucks passing by the bridge tower based on a previously validated full-scale CFD model. Two sets of simulations were conducted for comparison of aerodynamic force conditions of vehicles as they pass by the bridge tower: first group of simulations were performed including and excluding the road-sign gantry; and the second group include and exclude the tower shielding. Conditions in different traffic lanes (one on leeward side and two on windward side) considered. The effect of changes in wind yaw angle are also considered. Mechanism exploration on the variation of vehicle aerodynamic force conditions was made based on the numerical visualization of wind velocity field and pressure field. Novel results suggest that the road-sign gantry provides a sheltering effect in some circumstances, but a destabilizing effect in others. In addition, the tower shielding shows significant impact on reducing aerodynamic forces and sudden force changes of the high-sided vehicles while they are passing by the bridge tower.

Hazardous wind conditions can lead to critical safety problems for long-span bridges, either through dynamic oscillations or overturning of high sided vehicles. Engineers need to understand the local wind effects to ensure the safety and acceptable performance of bridge infrastructure. Traditionally, aerodynamic studies were carried out in wind tunnel facilities, however the opportunities of using computational fluid dynamics (CFD) modelling for wind assessments in place of wind tunnel tests are significant. To date, most of the existing studies are aimed at validation of wind tunnel tests and do not investigate full-scale effects. In this study, a validated full-scale 3D CFD model is developed in OpenFOAM using the k-omega-SST turbulence model for the world's longest three-tower cable-stayed bridge: the Queensferry Crossing Bridge, which located at Edinburgh in the United Kingdom. The 3D CFD model contains details such as wind shields and wind conditions were created based on field monitoring data which was provided by Transport Scotland. The aerodynamic force conditions of the high sided vehicle on the bridge are subsequently determined and analysed. Results suggested that the truck would be more vulnerable to variations in the lift force coefficient and rolling moment coefficient than the double-decker bus.

When an explosion occurs within reinforced concrete shear wall (RCSW) structures, the overpressures and duration of blast loads will be amplified by the confining effects of enclosed walls, which can cause a more severe damage to the structure than a free air explosion (FAE). However, research on RCSW structures subjected to internal explosions (IEs) are still limited and no benchmark tests exist. To provide a benchmark for studying the blast resistance of RCSW structures subjected to IEs, three Trinitrotoluene (TNT) IE field tests were conducted in this study on a 2-story, 3×3-bay, 1/3 scaled RCSW substructure, in which the overpressures, displacements, and crack patterns of RCSWs were recorded. The three tests were performed consecutively after each other on the same structure at TNT loads of 95.3g (Test-1), 253g (Test-2), and 400g (Test-3). The test results showed that the floor slab directly above the explosion and one of the RCSW confining the explosion failed in flexure (i.e., the support rotation angle exceeds 2°) in Test-2 with the scaled distance of 1.53, whilst the other three neighboring RCSWs failed in flexure in Test-3 with the scaled distance of 1.31. In addition, a detailed finite element model was established using LS-DYNA and was validated against the test results. The numerical simulation results showed that the energy released from TNT in IE scenarios (14.5 GJ/m3) was 1.95 times that in FAE scenarios (7.43 GJ/m3). The total blast loads applied to the RCSWs increased with the decrease of the area of opening. The average impulse applied to the four RCSWs were similar in IE scenarios, and the average impulse could be represented by the impulse at the center of each of the RCSWs (excluding the RCSW with window opening, as the opening is at the center). The shock and gas overpressure impulses at the center of RCSWs accounted for approximately 19.4% and 80.6% of the total impulse, respectively. Furthermore, the peak overpressures at the wall centers and the total blast loads experienced by the RCSWs under IE scenarios were 1.79 times and 11.13 times higher than those under FAE scenarios, respectively. This was due to the confinement of enclosed walls under IE scenarios. Consequently, the displacements and damage levels of the RCSW substructure under IE scenarios were much larger than those under FAE scenarios.

Bridge aerodynamic studies are essential in ensuring the safety and acceptable performance of long-span bridges vulnerable to the effects of cross-winds. Aerodynamic studies were traditionally carried out in wind tunnel facilities, but there are now greater opportunities for using computational fluid dynamics (CFD) modelling. Few three-dimensional (3D) aerodynamic simulations of lightweight vehicles on bridges exist, but limited validation and verification work has been carried out. In the study reported in this paper, 3D CFD models were developed for Queensferry Crossing – a cable-stayed bridge in Scotland – containing wind shields and sample vehicles. The models considered the wind effects from a range of yaw wind angles and subsequently determined the aerodynamic coefficients of vehicles. The models were verified by means of a mesh sensitivity study, a domain sensitivity study and comparisons with wind tunnel tests. The models were then validated using the same modelling process but with a different type of wind shield and again comparing the results with wind tunnel test data for the same configuration. The results showed that CFD modelling can determine aerodynamic coefficients to a level of accuracy similar to that of wind tunnel tests.

This paper presents a new and accurate finite element contact-modeling approach, to predict the axial compressive behaviour of bare cold-formed steel (CFS) lipped-channel sections (studs) set in tracks under concentric, static axial compressive loading. Detailed finite element analysis (FEA) models of the stud-track assemblies are developed using the ABAQUS software. The new modeling approach is validated against test results and captures stud-to-track gap and contact normal behaviour, which significantly influences studs' axial compressive performance. Hard contact (HC) has been used widely in literature for its simplicity, although it overestimates axial structural stiffness. Two softened pressure-overclosure relationships, with linear (LSC) and piecewise linear (PLSC) functions, were investigated for the first time in axially loaded bare CFS studs. PLSC bestreplicated studs' axial-compressive behaviour, post-peak response, and failure mechanism under track boundary conditions. PLSC slightly overestimated the axial stiffness by 1 %, underestimating axial shortening and ultimate capacity by 3 % and 6 %, respectively. HC significantly overestimated the axial stiffness by a factor of 3, with a 5 % overestimation of ultimate capacity. LSC failed to predict the accurate failure mechanism for studs having gauge thicknesses less than 3 mm. PLSC scale factors were established and were found to be closely correlated with studs' non-dimensional slenderness (2), following bilinear relationships. New predictive equations were developed to determine the PLSC scale factors for 2 ranging between 0.49 and 1.2 to enable designers to use accurately calibrated models to capture bare studs' complex axial compressive behaviour in the elastic and inelastic range.

This paper describes a novel method for detecting bridge damage that uses a partially instrumented vehicle fleet, each vehicle being instrumented with just one accelerometer. Importantly, no prior knowledge of the bridge or individual vehicle properties is required. Firstly, a model simplification concept is proposed to calculate the displacement under the vehicle wheel from single acceleration measurements on a half-car model. Then, optimisation is used to find individual vehicle properties using simulated noisy measurements from a fleet of vehicles. Finally, accelerations from the fleet are used to find the ‘apparent profile difference’, which contains bridge deflection data. The difference is found to be independent of surface profile but dependent on vehicle axle weight differences and a moving reference influence function (MRIF). When the axle spacings and the relative axle weights are reasonably consistent in a subset of the fleet, the MRIF can be simplified into a compound MRIF. Even when the MRIF and individual axle weights are not available on-site, the shape of the compound MRIF can be determined through an iterative process and used to monitor bridge health condition. Bearing damage is represented in this paper as an increase of rotational resistance of the bearings. The numerical results show that the damage severity and location can be identified.

Studs are the primary load-bearing components in cold-formed steel (CFS) wall panels, connected to tracks at both ends with self-tapping screws, forming a semirigid boundary condition (BCT). Most existing tests on the axial compressive behaviour of bare CFS studs are based on either theoretically-hinged (BCH) or fully-fixed boundary conditions. Previous researchers have employed BCT only on sheathed stud-wall panels. However, practicing engineers and current design codes, e.g., Eurocode 3, follow an all-steel design. Therefore, this research experimentally investigated bare-CFS-studs' axial compressive behaviour with BCT, considering, for the first time, the combined effect of the tracks' warping rigidity, stud-to-track gap, non-linear connection stiffness, and bare studs' various cross-sectional slenderness. Forty-two industry-standard lipped channel sections (studs) of five thicknesses (1.2-3 mm), three depths (75-125 mm), and two heights (1.2 & 1.5 m) were tested under static-concentric axial compressive loading with BCT. Another fourteen studs were tested with BCH, a comparator to BCT. Results demonstrated that the studs' global failure mechanisms were flexural-torsional in BCT instead of flexural in BCH. Studs' axial stiffness was two-phased in BCT due to the stud-to-track gap, compared to single-phased stiffness in BCH. >1.8 mm stud-to-track gap caused stud-to-track connections' failure and studs' sudden capacity reduction during gap closure. Studs achieved 1.22 times higher axial-compressive strength, 2.3 times more axial-shortening, 0.7 times lower axial stiffness, and 58% lower axial-compressive strain at the web-midheight under BCT-PhaseII than BCH. Tested strengths were compared with EC3 design strength, and an effective-length-factor of 0.65 was suggested for efficient design of studs with BCT.

Critical Infrastructures (CIs), which serve as the foundation of our modern society, are facing increasing risks from cyber threats, physical attacks, and natural disasters. Additionally, the interdependencies between CIs throughout their operational lifespan can also significantly impact their integrity and safety. As a result, enhancing the resilience of CIs has emerged as a top priority for many countries, including the European Union. This involves not only understanding the threats/attacks themselves but also gaining knowledge about the areas and infrastructures that could potentially be affected. A European Union-funded project named PRECINCT (Preparedness and Resilience Enforcement for Critical INfrastructure Cascading Cyber-Physical Threats), under the Horizon 2020 program, tries to connect private and public stakeholders of CIs in a specific geographical area. The key objective of this project is to establish a common cyber-physical security management approach that will ensure the protection of both citizens and infrastructures, creating a secure territory. This paper presents the components of PRECINCT, including a directory of PRECINCT Critical Infrastructure Protection (CIP) blueprints. These blueprints support CI communities in designing integrated ecosystems, operating and replicating PRECINCT components (or toolkits). The integration enables coordinated security and resilience management, incorporating improved 'installation-specific' security solutions. Additionally, Serious Games (SG), and Digital Twins (DT) are a significant part of this project, serving as a novel vulnerability evaluation method for analysing complicated multi-system cascading effects in the PRECINCT Living Labs (LLs). The use of SG supports the concentrated advancement of innovative resilience enhancement services.

To date, the majority of numerical modelling [computational fluid dynamics (CFD)] studies on long-span bridges have been carried out on scaled physical models, and without field-data for validation. For the first time, a full-scale bridge aerodynamic CFD study was conducted in this paper. A full-scale three-dimensional CFD model of the middle span and central tower of the Queensferry Crossing, United Kingdom, was created. The aim of this work was accurately simulating the wind field around the bridge. The CFD simulations were developed in OpenFOAM with the k − ω SST turbulence model. Atmospheric boundary layer inflows were configured based on wind profiles provided by a full-scale Weather Research and Forecasting (WRF) model. CFD predictions were validated with field data which were collected from an on-site Structural Health Monitoring System. The simulated fluctuating wind field closely satisfied the characteristic of field data and demonstrated that the modelling approach had good potential to be used in practical bridge aerodynamic studies. Meanwhile, comparisons and sensitivity analyses on mesh density provided a reference modelling approach for any future works on full-scale bridge aerodynamic models. Additionally, a cylindrical-like domain was applied in bridge aerodynamics for the first time and verified as being a convenient and reliable way to be used in bridge studies that involve changes in yaw angle.

This paper proposes a new indirect bridge structural health monitoring concept that uses acceleration data from a fleet of different vehicles with unknown weights. When a vehicle passes the bridge, the vertical displacement under its axles can be inferred from its vertical accelerations. This displacement, termed the “apparent profile”, contains two components: bridge profile elevations and bridge deflections under the axle. The two deflection component can be used to find the moving reference influence function (MRIF), defined as the deflection at a (moving) reference point due to a unit load at another point, moving at the same speed. The MRIF can be found when all axle weights are known. In this paper, a new method is proposed to obtain road profile and bridge health condition from the vehicle acceleration, without knowing individual axle weights. Numerical simulation results show that the inferred bridge profile changes when the bridge health condition changes. The difference can be used as an indicator of bridge damage and is illustrated here through an example of bearing damage.

This paper investigates the robustness of a 6‐storey corner‐supported Modular Steel Building (MSB) under notional ground floor corner column removal (i.e. alternate path method). The robustness assessment investigates the following structural effects that were frequently ignored for the sake of simplicity in existing numerical modelling approaches: (1) semi‐rigidity in the beam‐to‐column connections, and (2) initial out‐of‐straightness (geometric imperfection) in the compression members. Commonly, the welded connections between the beams and square hollow section columns are modelled as fully rigid, however, this may overestimate the actual robustness of MSBs as fully rigid connections often have a higher energy absorption capacity. Similarly, modelling a perfectly straight column could overestimate the actual robustness of MSBs. Comparing the model with semi‐rigid connections to that with fully rigid connections, an additional 30% vertical displacement was observed at the point of removal. However, geometric imperfections in the columns and diagonal braces did not cause any increase in building displacement/drift after removal. This highlights the importance of modelling the semi‐rigidity in the connections especially when the connections involve joining hollow sections.

This paper proposes the concept of structural health monitoring of bridges using measured accelerations on the bridge and equivalent fixed-point deflections.Moving Force Identification is used to infer applied forces from measured accelerations.Given the statistical repeatability in the weights of heavy vehicles at a given site, any inferred change in mean weight can be used as a damage indicator.Equivalent fixed-point deflection (or force) was found to be computationally stable.In effect, this focuses on the static part of the signal -the measured acceleration is being transformed into what is essentially a static parameter.Using the equivalent deflection from a group of trains without knowing their bogie weights, the normalised influence line is calculated and used as an indicator of structural condition.Simulations show that the equivalent deflection contains only a small dynamic component.As the deflection is the result of multiple applied loads, an influence line is found from the deflection, i.e., the component corresponding to a single point load.Using acceleration data from a simply supported railway bridge, the shapes of equivalent deflection influence lines are obtained from different groups of trains and show very good repeatability.Subsequently, this highly repeatable influence line is proposed as an indicator of certain types of bridge damage.