Search

The vulnerability of buildings faces further scrutiny as gaps in design, construction, operation, and maintenance remain. Although there has been noticeable progress in the field, the frequency and magnitude of building damage during natural events highlight the fact that sustainable infrastructure has not yet reached all targets. In this study, sustainability aspects of vulnerable buildings are revisited to propose more robust measures to prevent damage and a lack of functionality. Those measured are underpinned by the merging of environmental and structural sustainability for one novel integrated approach. The method devises structural intervention scenarios based on damage levels and service period. It also aims at reducing resource use and embodied impacts through the discretization of standard life cycle analysis into customized stages. The integrated method to evaluate sustainability is tested on two vulnerable buildings in Turkey and Mexico, built with different codes of practice and having experienced low to medium damage during severe earthquake events. Research findings indicate that although embodied impacts form a minor part of the building life cycle environmental impacts, sustainable structural interventions can further reduce both embodied impacts and demands on natural resources. Hence strengthening vulnerable buildings can provide an advantage to help the sustainable transformation of cities.

Wind turbines are conceived, designed and operated to interact with the environment, including through extreme events. However, engineering malpractices combined with human or mechanical errors and defects of constituent members and materials, still result in hundreds of structural collapse cases annually. It seems, therefore, necessary to reflect on factual wind turbine performance against the target performance. The present paper summarises the most severe tubular wind tower collapse incidents recorded over the past four decades, provides an account of the damage and discusses the respective potential causes. The investigation indicates that, although accidental load induced by typhoons and storms is the most usual reason of failure, fatal events concentrate at either early or late stage of the designed service life. Unexpected load conditions seemed to derive from defective blade positioning or braking, which in turn over-stress areas of transition such as joints and openings. However, a critical examination of design standards suggests that, in general, wind turbine towers as designed and built nowadays are stable and reliable. Hence, the chain relationship determined by the design, manufacturing, construction, operation and maintenance, needs enhancement and further cohesion, at the time that our understanding of and adaptation to extreme events continues to develop.

A graduate profile benchmark developed by a higher education organisation is subject to scrutiny. This occurs through the numerical parameterisation of text collected through surveys and the use of basic concepts drawn from Information Technology. The process uses data processing, analysis and evaluation to show the degree to which established an academic practice at the host institution correlates to pre-conceived professional outputs. The paper discusses standard practices including traditional and innovative teaching methods, in the light of achieved results. To conclude that postgraduate students require further engagement with the industry and exposure to the public whilst showing that the scientific and technical components of the subject courses are highly rated by stakeholders. Mitigation measures for the identified gaps include further curriculum development and inter-disciplinary work, reinforced with industrial liaison plus engagement with learned organisations and the public, via educational enhancement activities.

Crosswind stability of rolling stocks running on an embankment has been a key focus for decades, stemmed from the high overturning risks under crosswind. The correct reproduction of the embankment layout in a wind tunnel is therefore of great significance for estimating the train's aerodynamics and running safety. In this study, four different 6-m-high embankment layouts are proposed to replicate realistic wind tunnel configurations with the improved detached eddy simulation (IDDES) method. These helped to estimate the aerodynamics of a leading vehicle when subjected to a block wind profile of 45 m/s at the typical yaw angle of 30°. Furthermore, a static wind tunnel test with a 1:20 scaled train/embankment model enabled the validation of the numerical algorithm. The overall results indicate that all the aerodynamic coefficients of the leading vehicle mounted on the leeward track of the embankment top, decrease rapidly with the extending length of the upstream embankment. Similar aerodynamic performance appears on scenarios such as wall-to-wall (W2W) and partially wall-to-wall (P–W2W), which highlight equivalences between W2W and P–W2W under yaw effects. However, those particular scenarios considerably underestimate the aerodynamic coefficients compared with a more realistic scenario based on open domain (OD) and motion boundaries. Therefore, the conservative assessment of the vehicle aerodynamic characteristics based on the finite-length-embankment in a wind tunnel test could be taken into consideration for determining the running safety.

Strength reduction factors (SRFs) are typically estimated for seismic events ignoring the influence of wind. However, considering that strong earthquakes are commonly followed by a number of moderate to strong aftershocks and that wind is constantly flowing, often with low to medium intensity but occasionally reaching high speeds, then the assumption of using only earthquake ground records to determine SRFs seems questionable. In this paper it is shown that the combined action of strong winds and earthquakes, however low its probability of occurrence, would considerably increase the ductility demand of buildings and cause a decrease in SRFs calculated by ignoring wind. The paper examines the non-linear performance of single-degree-of-freedom systems subject to various levels of winds and earthquake load and deals with the estimation of SRFs associated with those multi-hazard scenarios.

This research examines the effect of plan irregularities on the progressive collapse of four steel structures located in regions with different seismic activity. The plans of the first and second structure are irregular, whilst those of the third and fourth structures are regular. The collapse patterns of the four buildings are examined and compared under seven loading scenarios using non-linear dynamic and static analyses. In the non-linear dynamic analyses, node displacements above the removed columns and the additional force on the columns adjacent to them are discussed. Furthermore, the strength and capacities of the columns are compared to determine their susceptibility to collapse. In the non-linear static analyses, the pushdown curve and yield load factor of the structures are obtained after column removal. The results indicate that an irregular structure designed in site class C seismic zone, collapses in most of the column-removal scenarios. Moreover, when comparing regular and irregular ...

The frequency of disasters recorded around the globe, combined with inadequate enforcement of design codes, the natural deterioration of the existing built fabric and poor use of land due to rapid urbanisation make urban infrastructure vulnerable to experience damage. This eventually creates the need for building retrofitting, which triggers further environmental degradation. Furthermore, the lack of a well-defined approach to guarantee sustainable structural recovery derives on structural interventions focusing on strengthening elements to improve their performance only, hence ignoring the plethora of building deficiencies associated to post-disaster retrofit. The aim of this investigation is therefore to embed structural upgrading within the principles of sustainability while developing the metrics to enable structural damage reduction. This will contribute to optimising post-disaster building interventions. The proposed approach is applied to a pilot case to illustrate identified alternatives for improving the performance of otherwise vulnerable infrastructure from a life-cycle perspective.

This investigation deals with numerical solution of complex aerodynamic interactions induced by a high-speed train (HST) entering and passing through tunnels with a closely adjacent gap and without in between. We present evidences that included pressure transient on the train surface and tunnel wall and comparisons between slipstreams and aerodynamic loads. The results show that two closely adjacent tunnels with a gap does not induce pressure differences on the tunnel wall, in relation to pressures otherwise observed on the single long tunnel, but slightly affects the friction component of the initial pressure rise on the train surface. In addition, the peak values of the slipstreams on the side nearest to the train inside the second tunnel are larger than those recorded when the train passed the first tunnel, suggesting that the existence of a gap between tunnels affect the airflow within the second tunnel. Peak drag coefficients for the train travelling through the first and second tunnel match while being 9.8% lower than the corresponding value observed within a single yet longer tunnel. The study highlights the differences on train aerodynamics when in transit through closely adjacent tunnels and a long tunnel to conclude that improved aerodynamic performances should be considered as the train circulates through closely adjacent tunnels as opposed to through a single passage. The study provides an aerodynamic guideline and reference for the tunnel engineering.

Given the increasing demand for taller structures in wind energy applications and the accompanying need for a better understanding of their structural response, the present study performs aeroelastic analysis on a novel wind turbine structure and discusses the obtained results. The response of a hybrid onshore wind turbine tower consisting of a 60 m lattice structure and a 60 m tapered tubular structure, with a 5 MW class AII turbine, is investigated. From the Design Load Cases (DLC) established in IEC64100-1 standard, focus is set on DLC 1.1 and DLC 1.3 which correspond to power production conditions and embody the requirements for loads resulting from atmospheric turbulence during normal and extreme operating conditions respectively. DLC 6.1 which refers to standstill or idling conditions under extreme wind model is also studied. In order to account for the interaction between elastic, viscous and inertial forces of the structure and the external aerodynamic forces, ashes, an integrated analysis software, is used. After developing the wind turbine tower model and generating the turbulence models, 600 seconds simulations are performed. The wind flow is assumed to be parallel to the hub axis. For DLC 1.1 and DLC 1.3, parametric studies with the wind speed ranging from 3 to 25 m/s, with an incremental step of 1 m/s, are executed. In DLC 6.1, the blades are feathered and the wind speed is rapidly increased to 42.5 m/s. Time histories of the elemental forces and the nodal displacements are extracted in critical positions of both the lattice and the tubular part. The mean values of the output data are evaluated and plotted against the wind speed. Conclusions regarding the influence of the wind speed on the induced tower behaviour are drawn.

Wind and earthquake load have historically been conceived to act independently. However, if we reflect on the fact that major seismic events are usually followed by a number of aftershocks and that wind is constantly flowing at high intensities around wind farms, which induces additional demands of resistance to infrastructure, then the joint probability of middle-to strong earthquakes and low-to mild wind events becomes more relevant. In this paper a generalised approach is used to estimate the ratio between earthquake and wind forces and their effect on infrastructure. Following, a probabilistic analysis is carried out to show that under certain conditions the combination of these natural events can induce additional demands of strength and ductility to wind turbines which could lead to unforeseen damage.

This paper describes a novel application of a pattern recognition technique for predicting boundary shear stress distribution in open channels. In this approach, a synthetic database of images representing normalized shear stress distributions is formed from a training data set using recurrence plot (RP) analysis. The face recognition algorithm is then employed to synthesize the RPs and transform the original database into short-dimension vectors containing similarity weights proportional to the principal components of the distribution of images. These vectors capture the intrinsic properties of the boundary shear stress distribution of the cases in the training set, and are sensitive to variations of the corresponding hydraulic parameters. The process of transforming one-dimensional data series into vectors of weights is invertible, and therefore, shear stress distributions for unseen cases can be predicted. The developed method is applied to predict boundary shear stress distributions in smooth trapezoidal and circular channels and the results show a cross correlation coefficient above 92%, mean square errors within 0.04% and 4.48%, respectively, and average shear stress fluctuations within 2% and 5%, respectively, thus indicating that the proposed method is capable of providing accurate estimations of the boundary shear stress distribution in open channels.

A methodology to estimate wind and rain effects on the four main growth crops in the United Kingdom is presented. The method is based on simulated weather scenarios acting on synthetic plants over a period of thirty years. The environmental data is generated with the UKCP09 Weather Generator considering future climate scenarios whereas plants are modelled as simple oscillators characterised by their mass, stiffness and damping. The joint probability of occurrence of wind and rain are estimated together with the conditions in which lodging would occur. The paper shows that the dynamic response of plants varies with season being the first three months of the year the most critical whilst the plants’ performances define crop failure velocities ranging between 4 ms−1 and 23 ms−1 and associated failure rates of 50% and 5% per unitary velocity.

This paper discusses the estimation of wind dynamic response of two types of structures by following classical and novel approaches. A new method for structural analysis based on wind design spectra is introduced and tested against simulated and experimental data. Design spectra are derived from the dynamic response of a group of oscillators subject to wind, using similar techniques than those used to derive design spectra for seismic engineering applications. The method is used on three chimneys of different height as well as on a regular building which has been experimentally tested in the past. The chimneys and building are also submitted to simulated wind fields to provide additional sets of results. It is observed that the spectral approach is consistent with experimental and simulated results and therefore is concluded that design spectra can cover broad range of practical applications.

This paper puts forward a framework to investigate the structural performance of buildings subject to the combined action of earthquakes and wind. The study uses a pushover analysis to determine strength capacities of low- and medium-rise concrete structures to compare versus their strength, as inferred from the Chinese code for seismic design. The analysis addresses soil-structure interactions through the scrutiny of fixed-base and flexible-base conditions of three soil types ranging between dense and soft. The parametric study covers micro meteorological winds whose mean value spans between 0.5 m/s and 20 m/s. The simulated multi-load scenarios induce ductility levels going from 1 to 6 to totalise 288 case studies. The proposed framework reveals that consideration of earthquake and wind simultaneous effects could modify performance levels used for design through enhancing ductility demands. This evidences that, under current design recommendations, structures located in earthquake prone areas susceptible to unexpected levels of damage.

This paper presents average numerical results of 2128 nonlinear dynamic finite element (FE) analyses of lightweight acceleration-sensitive non-structural components (NSCs) attached to the floors of one-bay three-storey reinforced concrete (RC) primary structures (P-structures) with different eccentricity ratios. The investigated parameters include the NSC to P-structure vibration period ratio, peak ground acceleration, P-structure eccentricity ratio, and NSC damping ratio. Appropriate constitutive relationships were used to model the behaviour of the RC P-structures. The NSCs were modelled as vertical cantilevers fixed at their bases with masses on the free ends and varying lengths so as to match the vibration periods of the P-structures. Full dynamic interaction was considered between the NSCs and P-structures. A set of seven natural bi-directional ground motions were used to evaluate the seismic response of the NSCs. The numerical results show that the acceleration response of the NSCs depends on the investigated parameters. The accelerations of the NSCs attached to the flexible sides of the P-structures increased with the increase in peak ground acceleration and P-structure eccentricity ratio but decreased with the increase in NSC damping ratio. Comparison between the FE results and Eurocode 8 (EC8) predictions suggests that, under tuned conditions, EC8 provisions underestimate the seismic response of the NSCs mounted on the flexible sides of the plan-irregular RC P-structures.

Traditionally, a quasi steady response concerning the aerodynamic force and moment coefficients acting on a flat plate while \'flying\' through the air has been assumed. Such an assumption has enabled the flight paths of windborne debris to be predicted and an indication of its potential damage to be inferred. In order to investigate this assumption in detail, a series of physical and numerical simulations relating to flat plates subject to autorotation has been undertaken. The physical experiments have been carried out using a novel pressure acquisition technique which provides a description of the pressure distribution on a square plate which was allowed to auto-rotate at different speeds by modifying the velocity of the incoming flow. The current work has for the first time, enabled characteristic pressure signals on the surface of an auto-rotating flat plate to be attributed to vortex shedding.

This paper describes the use of coupled Computational Fluid Dynamics (CFD) and Rigid Body Dynamics (RBD) in modelling the aerodynamic behaviour of wind-borne plate type objects. Unsteady 2D and 3D Reynolds Averaged Navier-Stokes (RANS) CFD models are used to simulate the unsteady and non-uniform flow field surrounding static, forced rotating, auto-rotating and free-flying plates. The auto-rotation phenomenon itself is strongly influenced by vortex shedding, and the realisable k-epsilon turbulence modelling approach is used, with a second order implicit time advancement scheme and equal or higher order advection schemes for the flow variables. Sequentially coupling the CFD code with a RBD solver allows a more detailed modelling of the Fluid-Structure Interaction (FSI) behaviour of the plate and how this influences plate motion. The results are compared against wind tunnel experiments on auto-rotating plates and an existing 3D analytical model.

A procedure based on the use of artificial neural networks (ANNs) and conditional simulation (CS) is presented as a tool to simulate wind fields. The aim of this work is to show a complete methodology to reproduce partially correlated wind fields for a two-dimensional space, starting from the knowledge of the local mean velocity and the level of roughness on the soil. The use of a multilayer ANN to predict wind time series in four strategic points in the two-dimensional space, together with the implementation of image recognition techniques, are explained first; afterwards the CS algorithm is applied to obtain intermediate wind series in order to complete the simulation. The effectiveness of this procedure is evaluated by comparison of its results to those reported by theory, for a specific example.

In earthquake-prone areas, wind and earthquake loads are assumed to be statistically uncorrelated and therefore their interaction is ignored in existing design guidelines. However, the facts that strong earthquake events are commonly followed by aftershocks and that wind is constantly flowing at high speeds around wind farms increase the probability of their joint occurrence, thus making current design assumptions questionable. This investigation shows that multi-hazard scenarios magnify the strength demands of wind turbine towers designed against isolated load conditions, hence modifying their performance level. It is also shown that, under certain conditions, the probabilities associated with the joint occurrence of earthquake and low to strong wind events match or exceed those related to the original design, thus rendering wind energy infrastructure susceptible to unforeseen damage.

This paper presents the results of measurements relating to the aerodynamic forces on flat square plates which were allowed to rotate at different speeds about their horizontal axis, by modifying the velocity of the incoming flow. A 1 m square test-sheet and a 0.3 m square test-sheet were fitted with a number of pressure sensors in order to obtain information relating to the instantaneous pressure distribution acting on the test-sheet; a compact gyroscope to record the angular velocity during the rotational motion was also implemented. Previous work on autorotation has illustrated that the angular velocity varies with respect to the torque induced by the wind, the thickness and aspect ratio of the testsheet,any frictional effects present at the bearings, and the vorticity generated through the interaction between the plate and the wind flow. The current paper sets out a method based on the solution of the equation of motion of a rotating plate which enables the determination of angular velocities on autorotating elements to be predicted. This approach is then used in conjunction with the experimental data in order to evaluate the damping introduced by the frictional effects at the bearings during steady autorotation.