Daniel McCrum

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 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 95.3 g (Test-1), 253 g (Test-2), and 400 g (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/m 3) was 1.95 times that in FAE scenarios (7.43 GJ/m 3). 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.

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.

The experimental and analytical lateral load resisting behaviour of three cold-formed steel (CFS) momentresisting frames with zero-tolerance bolted joints were investigated to understand the potential application of such joints in medium-span CFS portal frames. Strain gauge data were used to measure total longitudinal stresses in the column sections and were compared with analytical models. It was found that the bi-moment stress component was the second largest component after major-axis bending and can be analytically and conservatively estimated. The validity of the design approaches of monosymmetric and doubly symmetric back-to-back channel columns were also investigated. For the first time, the potential application of zero-tolerance jointed frames in medium-span CFS portal frames is demonstrated and conservative analysis and design approaches (monosymmetric) are employed.

The experimental and analytical lateral load resisting behaviour of three cold-formed steel (CFS) momentresisting frames with zero-tolerance bolted joints were investigated to understand the potential application of such joints in medium-span CFS portal frames. Strain gauge data were used to measure total longitudinal stresses in the column sections and were compared with analytical models. It was found that the bi-moment stress component was the second largest component after major-axis bending and can be analytically and conservatively estimated. The validity of the design approaches of monosymmetric and doubly symmetric back-to-back channel columns were also investigated. For the first time, the potential application of zero-tolerance jointed frames in medium-span CFS portal frames is demonstrated and conservative analysis and design approaches (monosymmetric) are employed.

Railway Infrastructures have been globally emphasized due to their crucial role in supporting everyday life by providing the flow of supplies, and services across the world. Therefore, considerable efforts have been devoted widely to improve the aforesaid systems' efficiency, resilience, and long-term viability. Being increasingly at risk from cyber-physical threats and natural diesters, as well as the interrelationships between critical infrastructures especially in smart cities, have made the situation more complex and highly challenging for urban planners to manage the impacts of cascading effects, develop mitigation plans and rapid recovery. Previous studies indicate that a promising approach to resolve this issue is Serious Games. Not only this method, but also GIS techniques are commonly tasked with solving and tracking spatial problems because of their great capabilities to meet the Spatial-based requirements of serious games. This paper presents a new integrative framework using GIS-based serious game to address the challenging issue of railways resilience. The serious game concept presented in this paper is being developed as part of the H2020 funded PRECINCT project (www.precinct.info).

In this paper, 3D CFD models of a bridge section of the Queensferry Crossing Bridge including a bus and other secondary structures on the deck are developed in OpenFOAM using the k-ω-SST turbulence model to determine the aerodynamic coefficients. The aerodynamic performance of the bridge deck accounting for several angles of attack with the bus located in various traffic lanes are investigated. The models are then validated with wind tunnel test results and  good agreement is found between the 3D CFD models and the wind tunnel tests. The importance of the validated models is that they can be used in the future to study what wind speed should be set as a limit to prevent high-sided vehicles from overturning on the Queensferrry Crossing Bridge.

Critical transportation infrastructure is an appealing target for attackers due the level of impact and value that can be obtained from cyber-attacks. In recent years, more and more transportation infrastructure operates as a cyber-physical system. A cyber-physical system exists when the physical world is integrated with ICT and IoT devices. Recent cyber-attacks in the transportation domain (e.g., denial of services attack in Swedish Transport Agency), demonstrate that cyber attackers of different characteristics (e.g., motives) can exploit cyber vulnerabilities (e.g., authentication mechanisms) and damage the physical space (e.g., loss of services). The inherent vulnerabilities of IoT devices (e.g., sensors) increase the risk of a IoT enabled transportation infrastructure protection being jeopardized. The question arises as to how to protect such cyber-physical systems? Traditional risk assessment processes consider the cyber and physical space as isolated environments. Subsequently, the risk assessment process for stakeholders (i.e., operators, civil and security engineers) who act as assessors, becomes more complex due to cyberrelated security issues. This paper aims to present for the first time the characteristics, that should be considered by stakeholders in order to conduct an accurate and complete cyber-physical risk assessment of their critical transportation infrastructure. These characteristics include the threat source, vulnerability and physical impacts considering both cyber and physical space. Additionally, the paper informs stakeholders about the role of control barriers, that source from cyber and physical space and describes for the first time the steps of cyber-physical attacks against an IoT enabled transportation infrastructure in its physical area. The results should be of great interest of stakeholders, who attempt to incorporate the cyber domain in risk assessment of IoT enabled transportation infrastructure.

Risk assessment and risk management often has to deal with uncertainty, especially in the context of critical infrastructure networks with manifold interdependencies and cascading effects. This uncertainty is not only due to the unpredictability of incidents, e.g., due to zero-day exploits or stealthy attacks such as Advanced Persistent Threats, but also consequences of an incident are challenging to predict. The traditional one-dimensional risk assessment is therefore not always sufficient and should be extended, e.g., to multiple impact categories (such as effects on humans, economic impact, etc.) Uncertainty should be explicitly considered during the entire risk management process. This paper illustrates how to adapt the classical risk management process to such generalized risk assessments, i.e., how to deal with risks that are assessed in multiple categories, within the context of a Serious Game approach to critical infrastructure protection.

This article investigates a way to develop a cascading effects simulation tool for a network of interdependent critical infrastructures that explicitly incorporates resilience aspects. To that end, an existing simulation tool for cascading effects, that builds on a graph representation of the network of critical infrastructures, is extended based on a resilience methodological framework in such a way that the resilience indicators directly influence the local behaviour of the components of the network and therefore the reaction of the entire network to an incident. This refined simulation model provides feedback on the effectiveness of the resilience indicators and at the same time provides input for the design of serious games. These games let players interact with the system to better understand the consequences of their actions (i.e., can be used for training), but also provide valuable information on the user's reactions to threats. This can in turn be used to identify ways to protect an infrastructure system against considered threats.

A project to formalise and expand Academic Advising has been implemented at the UCD Civil Engineering School. The goals of this project were twofold: on the one hand, it aimed at training faculty members in Academic Advising roles and providing them with the necessary resources. On the other hand, the project sought to expand student interaction, in particular by engaging students informally in order to build a rapport between them and the academic advisors that we expect will bring long term benefits. The resulting model combines elements of both the prescriptive, e.g., formal training, informative talks on key topics, and developmental approaches, e.g., coffee mornings for students and faculty members. The evaluation of the project was carried out through questionnaires and focus groups. It highlighted very positive feedback from the students, who find these new lines of communication with the academic staff to be useful and productive.

Scour is a significant issue for bridges worldwide that influences the global stiffness of bridge structures and hence alters the dynamic behavior of these systems. For the first time, this paper presents a new approach to detect bridge scour at shallow pad foundations, using a decentralized modal analysis approach through redeployable accelerometers to extract modal information. A numerical model of a bridge with four simply supported spans on piers is created to test the approach. Scour is modelled as a reduction in foundation stiffness under a given pier. A passing half-car vehicle model is simulated to excite the bridge in phases of measurement to obtain segments of the mode shape using output-only modal analysis. Two points of the bridge are used to obtain modal amplitudes in each phase, which are combined to estimate the global mode shape. A damage indicator is postulated based on fitting curves to the mode shapes, using maximum likelihood, which can locate scour damage. The root mean square (RMS) difference between the healthy and scoured mode shape curves exhibits an almost linear increase with increasing foundation stiffness loss under scour. Experimental tests have been carried out on a scaled model bridge to validate the approach presented in this paper.

Scour erosion poses a significant risk to bridge safety worldwide and remains among the top causes of failure. Scour at bridge foundations changes the stiffness of the soil-foundation system, resulting in global changes in the dynamic behavior of the bridge. In this paper, a new approach to detect the loss in foundation stiffness resulting from scour at multiple foundation locations is proposed, using wavelet-based Operating Deflection Shape (ODS) amplitudes. A numerical model of a bridge with four simply supported spans resting on piers is used to introduce and test the approach. Scour erosion is modelled as a reduction in vertical foundation stiffness under one or multiple bridge piers. A fleet of passing trucks, modelled as half-car vehicles, are used to excite the bridge to enable structural accelerations be calculated at an 'accelerometer' (sensor node) located at each support. The proposed method is shown to be effective with only one accelerometer at each support location in a multi-span bridge. Using a statistical population of passing vehicles, the temporal accelerations measured at each support are averaged and transformed into the frequency-spatial domain, in order to estimate the wavelet-based ODS for a given scour case. A damage indicator is postulated based on differences between the ODS of healthy and scoured bridge cases. The damage indicator enables visual identification of the location of scoured piers considering a range of natural frequencies of the system.

This paper develops a novel method of bridge damage detection using statistical analysis of data from an acceleration-based bridge weigh-in-motion (BWIM) system. Bridge dynamic analysis using a vehicle-bridge interaction model is carried out to obtain bridge accelerations, and the BWIM concept is applied to infer the vehicle axle weights. A large volume of traffic data tends to remain consistent (e.g., most frequent gross vehicle weight (GVW) of 3-axle trucks); therefore, the statistical properties of inferred vehicle weights are used to develop a bridge damage detection technique. Global change of bridge stiffness due to a change in the elastic modulus of concrete is used as a proxy of bridge damage. This approach has the advantage of overcoming the variability in acceleration signals due to the wide variety of source excitations/vehicles-data from a large number of different vehicles can be easily combined in the form of inferred vehicle weight. One year of experimental data from a short-span reinforced concrete bridge in Slovenia is used to assess the effectiveness of the new approach. Although the acceleration-based BWIM system is inaccurate for finding vehicle axle-weights, it is found to be effective in detecting damage using statistical analysis. It is shown through simulation as well as by experimental analysis that a significant change in the statistical properties of the inferred BWIM data results from changes in the bridge condition.

This paper investigates the seismic performance of a single storey moment resisting cold-formed steel (CFS) portal frame through cyclic testing. Six monotonic and six cyclic tests were performed on three different section sizes of CFS. The portal frames were 3.2m long x 2.2m high and the CFS sections bolted with either perfect-fit tolerance bolt holes (PTBH) or normal tolerance bolt holes (NTBH) connections. Connections with NTBH are standard in CFS, but connections with PTBH are often only used for short-spanning frames. Results from the tests demonstrated that both PTBH and NTBH connections had stable hysteresis and good hysteretic energy dissipation capacity and ductility. On average, the NTBH connections performed better under cyclic loading in comparison to the PTBH connections (5.4% larger ductility and 22.3% increased energy dissipation). Strain gauge results show failure due to combined bending and bi-moment stresses, of which the bi-moment stress component accounted for 41% of the total longitudinal stresses at the section web. It should be noted that bi-moment stresses are often incorrectly ignored by practitioners; the experimental test results thus show that by doing so the sections would fail at 59% of the design moment. Initial failure was localised at the top of the column sections in the form of local buckling at the web-to-flange junction under compressive stresses. Several load cycles past the initial buckling stage led to a further reduction of steel ductility due to strain hardening and strain ageing leading to fracture of the steel in the section corners. The buckling/tearing failure in the columns would result in a reduced axial load carrying capacity.

Shape memory alloys (SMAs) have the ability to undergo large deformations with minimum residual strain and also the extraordinary ability to undergo reversible hysteretic shape change known as the shape memory effect. The shape memory effect of these alloys can be utilised to develop a convenient way of actively confining concrete sections to improve their shear strength, flexural ductility and ultimate strain capacity. Most of the previous work on active confinement of concrete using SMA has been carried out on circular sections. In this study retrofitting strategies for active confinement of non-circular sections have been proposed. The proposed schemes presented in this paper are conceived with an aim to seismically retrofit a beam-column joint in non-seismically detailed reinforced concrete buildings. The complex material behaviour of SMAs depends on number of parameters. Depending upon the alloying elements, SMAs exhibit different behaviour in different conditions and are highly sensitive to variation in temperature, phase in which it is used, loading pattern, strain rate and pre-strain conditions. Therefore, a detailed discussion on the behaviour of SMAs under different thermo-mechanical conditions is presented in this paper.

Shape memory alloys (SMAs) have the ability to undergo large deformations with minimum residual strain and also the extraordinary ability to undergo reversible hysteretic shape change known as the shape memory effect. The shape memory effect of these alloys can be utilised to develop a convenient way of actively confining concrete sections to improve their shear strength, flexural ductility and ultimate strain capacity. Most of the previous work on active confinement of concrete using SMA has been carried out on circular sections. In this study retrofitting strategies for active confinement of non-circular sections have been proposed. The proposed schemes presented in this paper are conceived with an aim to seismically retrofit a beam-column joint in non-seismically designed reinforced concrete buildings. The complex material behaviour of SMAs depends on number of parameters. Depending upon the alloying elements, SMAs exhibit different behaviour in different conditions and are highly sensitive to variation in temperature, phase in which it is used, loading pattern, strain rate and pre-strain conditions. Therefore, a detailed discussion on the behaviour of SMAs under different thermo-mechanical conditions is presented first in this paper.

This paper presents the results from the experimental investigation on heat activated prestressing of Shape Memory Alloy (SMA) wires for active confinement of concrete sections. Active confinement of concrete is found to be much more effective than passive confinement. Active confinement achieved using conventional prestressing techniques faces many obstacles due to practical limitations. A class of smart materials that has recently drawn attention in civil engineering is the shape memory alloy which has the ability to undergo reversibl e hystereti c shape change known as shape memory effect. The shape memory effect of SMAs can be utilized to develop a convenient prestressing technique for active confinement of concrete sections. In this study a series of experimental tests are conducted to study thermo-mechanical behaviour of Ni 48.46 Ti 36.03 Nb 15.42 (wt. %) SMA wires. Although, numerous studies on active confinement of concrete using NiTiNb SMA have been carried out in the past, no particular study on Ni48.46Ti36.03Nb15.42 exists in the literature. A series of tests were conducted in this study to characterize the material properties of Ni 48.46 Ti 36.03 Nb 15.42 for active confinement of concrete sections. Parameters such as heat activated prestress (HAP), residual strain and the range of strain that can be used for effective active confinement after HAP were investigated in detail. The influence of pre-strain and temperature on HAP was also investigated. It was found that a significant amount of HAP can be developed in pre-strained Ni48.46Ti36.03Nb15.42 upon heating, most of which is retained at room temperature. A substantial amount of strain recovery upon unloading and after heating was recorded in all tests. The range of strain available for effective active confinement was also found to be significant. The results from this study demonstrate that the chemical composition of NiTiNb along with level of pre-strain and the corresponding transformation temperature range significantly affects the HAP, which in turn can affect the efficacy of the retrofitting strategy in which NiTiNb is used as a means to apply active confinement.

Shape memory alloys (SMAs) have the ability to undergo large deformations with minimum residual strain and also the extraordinary ability to undergo reversible hysteretic shape change known as the shape memory effect. The shape memory effect of these alloys can be utilised to develop a convenient way of actively confine concrete sections to improve their shear strength, flexural ductility and ultimate strain. Most of the previous work on active confinement of concrete using SMA has been carried out on circular sections. In this study retrofitting strategies for active confinement of non-circular sections have been proposed. The proposed schemes presented in this paper are conceived with an aim to seismically retrofit beam-column joints in non-seismically designed reinforced concrete buildings.

SMAs are complex materials and their material behaviour depends on number of parameters. Depending upon the alloying elements, SMAs exhibit different behaviour in different conditions and are highly sensitive to variation in temperature, phase in which it is used, loading pattern, strain rate and pre-strain conditions. Therefore, a detailed discussion on the behaviour of SMAs under different thermo-mechanical conditions is presented first.

Progressive collapse in building structures is characterised by the sequential spread of structural failure upon an initial local failure,. The resistance of an entire building structure against this phenomenon is predominantly dependent on the material behaviour, strength and interaction of individual structural components. Cold-formed steel (CFS) sections are thin-walled and open cross-sections, and subsequently have certain characteristics such as instability, geometric imperfections, local distortional, global buckling and warping that make their response to disproportionate collapse loading different from traditional hot rolled steel building structures. Research on the progressive collapse resistance of CFS building structures considering individual structural component interaction is limited in literature and requires further investigation.   
Little prescriptive design guidance exists for the progressive collapse resistance of CFS structures, leading to their overly conservative sectional sizes. The aim of this research is to investigate experimentally and analytically, the performance and failure mechanism of CFS lipped channel stud sections under a progressive collapse scenario.
Commercially available, lipped channel sections of 1.2 m and 1.5 m heights, various depths (75, 100 and 125 mm) and thicknesses (1, 1.2, 1.3, 2 and 3 mm) were tested under concentric monotonic axial compressive loading. For the first time, realistic loading conditions for the stud sections that was applied through track sections connected with self-tapping screws. These conditions represent identical boundary and loading condition for the studs as that in a CFS building under a notional element removal scenario during progressive collapse. Two types of nonlinear analytical models of the stud sections were developed considering true material stress-strain data obtained from coupon tests, geometrical imperfections and semirigid connection strength: a) a finite element plate model using the Abaqus [1], and b) a simplified non-linear beam column model using the OpenSees [2]. The analytical models were validated using the test results.
The main findings included a detailed understanding of the failure mechanism and post buckling strength of the CFS stud sections in a progressive collapse scenario, leading to their optimum design using a simplified beam-column modelling approach.