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The active control of the first mode of vibration of two slender, wind-loaded buildings, one 200 m tall, the other 400 m, is studied. The control is applied to the buildings via an active tuned mass damper located at the top of the building. An algorithm using acceleration feedback from the top of each building is used, as is a range of empirical algorithms using some combination of feedback from the first mode of vibration of the buildings. For both buildings, it is the more critical cross-wind response which is studied, and the response is reduced to a level acceptable for human comfort. All the algorithms provide the required control using achievable control forces; however, the algorithms using pure acceleration feedback produce the best control performance for both buildings. This is because acceleration feedback combines in the most efficient way with the passive control inherent in a hybrid control system.

The effectiveness of a tuned liquid column damper (TLCD) in controlling structural vibration is studied. A numerical method is adopted to account for nonlinearity of the governing equation. Optimum parameters of the TLCD for maximum reduction of peak structural response to harmonic excitations in a wide frequency range are presented for a wide range of flexible structures. A variation of U-shaped TLCD with different cross-sectional areas in its vertical and horizontal sections is investigated. It is found that an increase in cross-sectional area ratio (vertical/horizontal) can greatly reduce the length requirement of a TLCD making it more attractive to flexible structures. A new type V-shaped TLCD is also investigated. This type of TLCD can suppress stronger vibrations such as those caused by strong wind. It is found that, like the tuned mass damper (TIVID), there is an optimum tuning ratio (damper frequency/structure frequency) for maximum reduction in response of a structure system which is independent of the excitation. The optimum coefficient of head loss will depend on the intensity of the excitation with smaller coefficient of head loss associated with stronger excitation.

An investigation is undertaken into the bidirectional configuration of the liquid column vibration absorber (LCVA), in which the horizontal and vertical columns may have different cross-sectional areas depending on performance requirements. The bidirectional LCVA appears as a rectangular annulus in plan and mitigates the vibrations of a structure free to move in the horizontal plane by the gravitational restoring force acting on displaced LCVA liquid, energy dissipation occurring through the viscous interaction between the rigid LCVA container and the LCVA liquid, as well as transition effects which occur as the liquid moves between the horizontal and vertical columns of the LCVA. The performance of various configurations of the bidirectional LCVA are studied experimentally when installed on a primary structure subjected to external sinusoidal loading. A theoretical model of the response of the primary structure is presented in which the LCVA is modelled as an equivalent solid mass vibration absorber (SIVIVA) and is found to agree with experimental data. The parameters which allow optimization of the performance of the bidirectional LCVA are investigated, and methods allowing their prediction and control are also presented.

Full-scale deflection measurements were performed on a 67 m steel frame tower and a 233 m steel truss tower under wind loading. Measurements were acquired by various means and compared with along-wind theoretical estimates. The latter were obtained using a simplified frequency domain prediction that incorporates some practical observations and remarks. The dynamic cross-wind response of lattice towers was also measured and discussed.

This paper details the development of an instrumentation system for the measurement of the wind-induced dynamic response of structures. It was installed on an 84 m high concrete control tower of circular cross-section. Twelve months of data measured at the tower are presented and it is demonstrated that the accelerations experienced exceed serviceability criteria for human comfort. The effects of differing incident turbulence regimes are investigated and are found to have no significant effect on the dynamic response of the tower. The first and second mode natural frequencies were measured as 0.39 and 2.62 Hz, respectively. The structural damping of the tower was estimated to be 0.8 %. The mode shape of the tower was closely approximated by a power law with an exponent of 1.6.

Full-scale damping measurements were performed upon three classes of civil engineering structures including free-standing lattice towers, reinforced concrete buildings and pedestrian footbridges. Most of these structures were subjected to forced vibration tests to obtain structural damping estimates. Autocorrelation and random decrement procedures were used to extract total damping from load-induced resonant response signals. Both these procedures were further scrutinised in light of the measured results. A simplified analytical expression for aerodynamic damping was derived. Some damping predictors were proposed based upon the findings of this paper.

This chapter examines the wind-induced vibrations of buildings and structures. In particular, the alongwind and the crosswind excitation mechanisms and response processes are discussed. Turbulence buffeting is the dominant excitation mechanism in the alongwind direction. In the crosswind direction, excitations associated with incident turbulence, vortex shedding and motion dependent excitations are the prominent mechanisms causing crosswind response. Many advanced wind codes and standards have adopted statistical and spectral analysis processes to predict wind loads and responses caused by these alongwind and crosswind excitations. The potential impact of interference excitations of tall buildings and beneficial effects of aerodynamic modifications of building shape are also reviewed in this chapter. Interference effects on the alongwind, crosswind and torsional responses of tall buildings from either an upstream or a downstream building are outlined. The beneficial effects and the economic perspectives of aerodynamic modifications of building shape in reducing the wind induced load and response of tall buildings are discussed.

The performance of both passive and active tuned mass damper (TMD) systems can be readily assessed by parametric studies which have been the subject of numerous research. The results of those parametric studies are invaluable in the selection of optimum TMD parameters. Few experimental verifications of TMD theory have been carried out, particularly those involving active control, but the results of those experiments generally compared well with those obtained by parametric studies. Despite some serious design constraints, a number of passive and active tuned mass damper systems have been successfully installed in tall buildings and other structures to reduce the dynamic response due to wind and earthquakes. The results of extensive full-scale measurement programs conducted on a significant number of these clearly show the effectiveness of the systems.

Viscoelastic (VE) dampers have been successfully incorporated in a number of tall buildings as a viable energy dissipating system to suppress wind- and earthquake-induced motion of building structures. This type of damper dissipates the building's mechanical energy by converting it into heat. Several factors such as ambient temperature and the loading frequency will affect the performance and hence the effectiveness of the damper system. VE dampers have been able to increase the overall damping of the structure significantly, hence improving the overall performance of dynamically sensitive structures. The effectiveness of VE dampers has been demonstrated both experimentally and analytically by many researchers over the past 25 years. The twin towers of the World Trade Center Buildings in New York City and the Columbia SeaFirst Building in Seattle, Washington, are among the first buildings which benefited from the installation of VE dampers. In seismic applications, the VE dampers can be incorporated either into new construction or as a viable candidate for the retrofit of existing buildings which adds to the versatility of VE dampers.

This study aims to expand the aeroelastic unstable range of a circular cylinder for improving the efficiency of a vortex-induced vibration (VIV)-based wind energy harvester. The kinetic energy of the harvester is provided by flow-induced vibration of a circular cylinder. Two small-diameter cylindrical rods were attached on two sides of the circular cylinder parallel to the cylinder axis and symmetrical to the stagnation line at a series of circumferential locations. This was inspired by rain-wind-induced vibrations of stay-cables of cable-stayed bridges. It was found that attaching two small-diameter cylindrical rods at the circumferential location θ = 60° significantly expands the aeroelastic unstable range for the circular cylinder. The wind energy harvester with this configuration harnesses the wind energy beyond the VIV onset wind speed and is sustained over the range of wind speed. Therefore, this configuration possesses a dramatic superiority over a plain circular cylinder as the kinetic source of a...

Wind tunnel model tests were performed to investigate interference effects on torsional response of a tall square cross-section building with structural asymmetry (eccentricity between mass and elastic centres). The asymmetric building model was an aeroelastic model capable of pure torsional motion. Two sizes of square cross-section rigid interfering building models were individually located at positions upstream and downstream of the asymmetric principal model to provide interference effects. It was found that the mean and standard deviation torsional responses of the asymmetric principal building could be significantly enhanced due to the presence of the interfering building. Critical locations of the interfering building and the corresponding torsional responses of the principal building were dependent on the size of the interfering building and the eccentricity position of the principal building relative to wind incidence.

An active tuned mass damper (ATMD) installed in the top of a rectangular model building was tested in a wind tunnel for its effectiveness in suppressing cross-wind building vibrations. The ATMD was controlled using a sub-optimal control algorithm. Certain parameters critical to the operation of the ATMD were varied to observe how the ATMD's effectiveness would be altered. The ATMD was found to be effective in reducing cross-wind vibrations. The vibration in design parameters of the ATMD resulted in different levels of reduction.

This paper presents the results of a field measurement program which was conducted on a steel frame tower. Dynamic characteristics of the tower were measured to determine its frequencies of vibration, mode shapes and damping values. A STRAND6 computer model was assembled and confirmed these findings. The dynamic response of the tower under wind loading wasinvestigated before and after the attachment of ancillaries.

This letter presents the effects that fitting fins to various corners of a square-prism galloping-based piezoelectric energy harvester (PEH) has on its performance, based on results from a series of wind tunnel model tests. The results show that attaching fins to the leading edge significantly improves the efficiency of the harvester, achieving a maximum power 2.5 times that attained by a plain square prism PEH. Furthermore, a length that is 1/6 of the prism's cross-sectional width is found to be optimal for fins that are attached to the harvester.

The operation, maintenance, and construction of buildings require a huge amount of energy and generate a significant amount of greenhouse gases (GHG’s) (Hendrickson 2000). The energy and GHG’s are generated from the process of extracting raw materials, producing and manufacturing new materials, transporting materials to sites, and installing materials (Junnila et al. 2006). Energy conservation and control of GHG’s are critical to ensure energy security for future generations and to alleviate the impact of climate change. This paper presents a new approach of Enterprise Carbon Accounting. The method is based on categorization depending on the size of the organization and its assets. Categorization of similar buildings and assets are averaged and analyzed as a unit. Outliers and averages of each type are then examined for causes, correlations, and future solutions. The proposed method will establish a carbon emission and energy use baseline for the large scale agency.

In this present work, the characteristics of hazardous gas dispersion and possible cross-unit contamination around a complex-shaped high-rise residential building due to wind effect are thoroughly studied using physical modeling method. Experiments were performed in a boundary layer wind tunnel for a 1:30 scale model that represented a 10-story residential building in prototype. Tracer gas, simulating exhausted room air, was continuously released from different floor levels, and its concentrations on the adjacent envelope surfaces were measured using fast flame ionization detectors. The mean concentration fields were reported and analyzed under different configurations during the experiment to consider the effects on pollutant dispersion behavior due to changes in source position and approaching wind condition, with the main emphasis on the differences between open-window and closed-window conditions. In particular, the measured concentration fields were further examined from a practical point of view, with respect to hazard assessment. Understanding these hazardous plume dispersion features is useful for employing effective intervention strategies in modern residential building environment in case of hazardous substance release. The study on this physical process is not only helpful to reduce the hazardous effect of routine release of harmful pollutant near the building, but also useful for the purpose of prevention and control of accidental infectious diseases outbreak.

This paper describes the simulation of turbulent boundary layer flow in a wind tunnel for the study of snowdrifting around Antarctic buildings. Profiles of mean wind speed and turbulence intensity, and the longitudinal turbulence spectrum, are presented. Similarity parameters proposed by other researchers are applied to the simulation. Snowdrifting around the workshop building of Australian Davis Station was investigated. Two attachments to the building were tested to find a way of alleviating a known snowdrifting problem.

This paper describes an experimental investigation in wind tunnel of torsional vibration and stability of a tall square cross-section building with eccentricity between building elastic and geometric centres. 1:400 scale wind models of natural wind flow over open country and city centre terrains were deve3oped in the wind tunnel. The eccentric building model was tested by using an aeroelastic test rig designed for pure torsional vibration. The probability distribution of torsional peak response, aerodynamic damping and excitation spectrum were examined to determine torsional excitation and response characteristics. It was found that with a 10% geometric eccentricity ratio the tall square building was susceptible to torsional vibration. There was also a significant increase in the maximum mean response. For the open country terrain unstable torsional vibration due to vortex shedding was observed in which lock-in type large amplitude twist angular displacement occurred. Increase in turbulence associated with the city terrain, however, effectively mitigated torsional lock-in excitation.

General mode shape correction factors are suggested to adjust aeroelastic model test results to prototype values of tall buildings for alongwind, crosswind and torsional vibrations. These factors were found to agree well with previous experimental and analytical results in the literature.

Load Factors or Safety Factors applicable to wind tunnel results of cladding pressures are presented. These incorporate the effect of method of analysis, the digitisation process and a number of sampling parameters. The sampling parameters investigated were the sample length, the sampling frequency and the low-pass filtering frequency. In the process of assessing the effect of these parameters, a number of methods of analysis were compared in terms of their sensitivity to the sampling parameters and the digitisation process.

Wind tunnel model tests and theoretical analyses were conducted to investigate the effectiveness of tuned mass dampers in suppressing wind-induced tall building motion. The tall building model was a 1:400 scale aeroelastic model of the CAARC Standard Tall Building. This model and the tuned mass damper models of different parameters were designed and tested in a wind tunnel with properly simulated atmospheric boundary layer flow. The aeroelastic test of the CAARC model demonstrated the effectiveness of the tuned mass damper system in suppressing the dynamic response of the building. The parametric study of passive tuned mass dampers, leading to theoretical analysis and design of an effective and efficient tuned mass damper system, was based on excitation spectra which were directly measured from the wind tunnel model tests. Semi-analytical results were in good agreement with the test results. The analytical results further indicated that the effectiveness of tuned mass dampers can be enhanced by the inclusion of an active control system.

An investigation is made of the possible application of tuned liquid column dampers (TLCD) and tuned liquid column/mass dampers (TLCMD) in reducing the cross-wind response of wind-sensitive structures. The structure is modelled as a lumped mass multi-degree-freedom system taking into account both bending and shear. The cross-wind wake excitation is modelled as a stochastic process which is stationary in time and non-homogeneous in space. A random vibration analysis utilising transfer matrix formulation is carried out to obtain response statistics. The nonlinear damping term in the fundamental equation of the tuned liquid damper is treated by an equivalent linearization technique. Numerical examples show that tuned liquid dampers, which have significant practical advantages, can achieve the same motion reduction level as the traditional tuned mass dampers if the parameters of the liquid dampers are properly selected. However, excessive liquid motion in a tuned liquid column/mass damper may reduce the effectiveness of this damper and therefore a careful selection of the frequency tuning ratios of the damper is necessary.

An investigation is made of the possible application of tuned liquid column dampers and tuned liquid column/mass dampers in reducing the along-wind response of wind-sensitive structures. The structure is modeled as a lumped mass multi-degree-of-freedom system taking into account both bending and shear. The wind turbulence is modeled as a stochastic process that is stationary in time and nonhomogeneous in space. A random vibration analysis utilizing transfer matrix formulation is carried out to obtain response statistics. The nonlinear damping term in the fundamental equation of the tuned liquid damper is treated by an equivalent linearization technique. Numerical examples show that tuned liquid dampers, which have significant practical advantages, are as effective as the traditional tuned mass dampers if the parameters of the liquid dampers are properly selected. However, excessive liquid motion in a tuned liquid column/mass damper may reduce the effectiveness of this damper. It is also shown that the wind-induced force- and acceleration-type responses of the structure with a damper, which is usually tuned to the fundamental frequency of the structure, should involve more than one vibration mode as higher-mode responses may become as large or even larger than the controlled-mode response.

A series of wind tunnel model tests and theoretical analyses were conducted to investigate torsion excitation, response and vibration suppression of wind-excited buildings. An aeroelastic model for pure torsion vibration was developed and the aeroelastic test results were compared with those obtained by other wind tunnel test techniques. The comparison and practice indicated that this type of modelling technique can be a convenient and efficient way to explore the mechanisms of torsional excitation and predict the torsional response of tall buildings to wind after considering mode shape correction. It is also shown that tuned mass dampers were effective in suppressing the torsional vibration of the building if the parameters of the tuned mass damper were properly selected.

The wind-induced motion of tall/slender structures equipped with tuned mass dampers was investigated, taking into account the effect of soil compliancy under the footing. A transfer matrix formulation was used to analyse the soil-structure-mass damper interaction in the frequency domain. Numerical examples show that soil compliancy will affect structural responses and the effectiveness of tuned mass dampers, depending on the properties of the soil, the properties of the structurem the nature of the excitation and the type of structural response.

Previous papers have described wind tunnel measurements on isolated and grouped storage bins, silos and tanks of circular cross-section. In this paper, distributions of fluctuating and peak pressures on the walls of both isolated and grouped silos are described. They were generated using the techniques of eigenvector analysis of the covariance matrix, and “coincident peak” sampling.

Following previous work in which point pressure measurements on isolated low aspect ratio circular structures such as storage bins, silos, and tanks were described, this report describes measurements of wind loads on silos arranged in an in-line group of five. As well as point pressures, area-averaged pressures on wall panels of finite area were carried out using the pneumatic averaging technique. At small spacing between silos, the region of positive pressure on the windward side spans a larger angular sector of the circumference than that for an isolated silo. For wind directions near normal to the line of the silos, high negative mean pressures and high r.m.s. pressures occur near the point of shortest distance to the adjacent silos.

selected for presentation 26.4 Slow linear physiologic displacements modulate skin sympathetic nerve activity in supine humans P.S. Bolton, E. Hammam, K. Kwok, V.G. Macefield School of Biomedical Sciences & Pharmacy, University of Newcastle School of Medicine, University of Western Sydney Institute for Infrastructure Engineering, University of Western Sydney

A series of wind tunnel sectional model dynamic tests were conducted to examine the effects of torsional-to-vertical natural frequency ratio on the aerodynamic and dynamic properties of bridge decks. The natural frequency ratios tested were around 2.2:1 and 1.2:1 respectively, with the fundamental vertical natural frequency held constant for all the tests. Two 2.9 m long sectional bridge models, one simulating the cross-section of a twin-deck bridge with a gap-width to total chord ratio of about 16% and the other with zero gap-width to approximate a thin plate, were tested to determine whether the effects of frequency ratio are similar for bridge decks with different cross-section shapes. The results of wind tunnel tests suggest that for the model with zero gap-width, the flutter derivatives are relatively independent of the torsional-to-vertical frequency ratio for a relatively large range of reduced wind velocities. However, for the model with a relative large gap-width (around 16%), the flutter derivatives are evidently dependent on the frequency ratio for most of the tested reduced velocities. A comparison of the modal damping ratios also suggests that the torsional damping ratio is much more sensitive to the frequency ratio, especially for the model with a 16% gap-width. The results of this investigation show that the torsional-to-vertical natural frequency ratio is an important structural parameter, which can significantly affect wind-structure interaction.

This paper presents an overview of the wind tunnel studies conducted at the boundary layer wind tunnel facility at the University of Sydney to determine across-wind forces acting on the 76-story 306 m high benchmark building. The paper briefly describes the boundary layer wind tunnel and its special features, and then presents the testing procedures and the methodology used to determine the wind loads acting on a 1:400 model of the building. © ASCE / APRIL 2004.

A study has been undertaken on the effectiveness of using liquid column vibration absorbers (LCVAs), in the suppression of wind-induced motion of the 76-story benchmark building. Much work has been undertaken on the behavior of the LCVA on an experimental level and its benefits have been demonstrated for wind-induced vibration control on a full-scale communications tower in Sydney, Australia, with a further installation being made on the "One Wall Center Building" Vancouver, Canada. The behavior of the LCVA has also been investigated numerically by use of computational fluid dynamics, and its potential has been illustrated in controlling a five-story building model. In this study, the LCVA adopted is composed of four identical columns of water. Initially, the performance of the LCVA is assessed without the inclusion of additional damping enhancing mechanisms. Subsequently, the same LCVA is considered with the inclusion of orifice plates, allowing a direct comparison of the two strategies. In order to address the issue of robustness, the sensitivity of the LCVA (with and without orifice) to mistuning is examined by perturbing the structural stiffness of the building by +15% and -15%, respectively. From this, an indication of the system performance under conditions of mistuning has been assessed. The performance of the adopted LCVA has also been compared to that of the sample tuned mass damper (TMD) control device. The overall response reductions of the LCVA are shown to be comparable to the TMD. Furthermore, it is shown that the LCVA has several inherent features that make it more attractive than the classical TMD. © ASCE / APRIL 2004.

The inability to satisfy Reynolds number similarity in wind tunnel modelling of low-rise structures with circular features, and the lack of full-scale results have left designers with inadequate information for the design of circular storage bins, silos and tanks against wind loading. In this paper, wind tunnel pressure measurements on scale models of low-rise cylindrical structures carried out at Reynolds numbers > 2 × 10 5 are described. Circumferential wall pressure distributions and roof pressures for a range of aspect ratios and roof configurations are presented.

Circular and square tower models were tested in a boundary layer wind tunnel. At close to the critical reduced velocity and particularly at low values of structural damping, displacement dependent lock-in excitation was found to cause large increases in cross-wind displacement response, especially for the circular tower, in a suburban type wind model. Critical cross-wind response amplitudes were determined from the response characteristics. These response amplitudes represent the level of cross-wind response of a structure above which the response can not be accounted for by the random wake excitation process and that lock-in excitation is significant. A prediction procedure, which consists of a random excitation model and a sinusoidal lock-in excitation model, is described. Cross-wind response predicted by these models agreed well with the measured response.

A design procedure was developed using random vibration theory and uses mode-generalized cross-wind force spectra and aerodynamic data to calculate the cross-wind displacement and acceleration responses of tall buildings. The force spectra of a number of building shapes and sizes in both suburban and city centre type wind flow are presented. The proposed design procedure gives reasonable estimates of the cross-wind response, compared with wind tunnel measurements, at reduced wind velocities and at structural damping values consistent with modern habitable tall building design. This allows assessment of the structural requirements of tall buildings to be made at an early design stage, and also allows the designers to assess the need for more detailed and expansive wind tunnel model tests.

Results of full scale measurements of the dynamic characteristics of a steel lighting tower at the Sydney Cricket Ground in New South Wales, Australia, are presented. The first three natural frequencies of vibration were found to be 0.50 Hz, 2.40 Hz and 4.84 Hz respectively; the corresponding mode shapes have also been determined. These results are compared with those obtained from a plane rigid frame dynamic analysis computer program and found to be in good agreement. Damping levels (in % of critical) were found to be approximately 0.3%, 0.8% and 1.0% for the first three modes.

Wind tunnel tests were conducted to investigate the effects of some aerodynamic devices on the wind‐induced responses of tall buildings and structures. It was found that the fitting of small fins or vented fins to a square tower caused an increase in the along‐wind response, while reduction in cross‐wind response occurred only for a limited range of reduced wind velocities. The use of slotted corners resulted in significant reductions in both the along‐wind and cross‐wind responses over an extended range of reduced wind velocities. The concept of slotted corners is practical and could be useful in the design of modern tall buildings and structurees.

Procedures for analysis of environmental wind conditions at the site of a proposed building, using mean annual maximum wind data and wind tunnel model testing are discussed. NEWMED I, the Clinical Sciences Building of the University of Newcastle, which is situated at the Royal Newcastle Hospital, is used as an exam pie. Wind data indicated the wind tunnel testing from the S and WNW directions would be adequate to describe the environmental wind conditions at NEWMED. Testing indicated unacceptably high annual maximum wind gusts under southerly flow at the exposed southern end of the building, the majority of ground level locations, and in Reids Park, despite a wind break in the latter area. Under WNW flow, strong winds occurred at both ends of the building and close to Reids Park. Suggestions are made to minimize the effect of the strong winds to maximise human comfort.

The enhanced dynamic response of a tall square building under interference excitation from neighbouring tall buildings has been studied in a series of wind-tunnel model tests. In a low-turbulence wind environment and under normal strong wind conditions, the dynamic loads on the upstream of an identical pair of tall buildings may increase by a factor of up to 4.4. The dynamic loads on the downstream building of the pair may increase by a factor of up to 3.2 due to “resonant buffeting”. Measurements of along-wind and cross-wind force spectra and a number of wake spectra provide an explanation for the observed behaviour. Possible excitation mechanisms are discussed and critical building arrangements presented. The large interference loads found in this study indicate that interference excitation should be carefully considered in the design of tall buildings.

Australian railway networks possess a large amount of aging timber components and need to replace them in excess of 280 thousands m3 per year. The relatively high turnover of timber sleepers (crossties in a plain track), bearers (skeleton ties in a turnout), and transoms (bridge cross beams) is responsible for producing greenhouse gas emissions 6 times greater than an equivalent reinforced concrete counterparts. This paper presents an innovative solution for the replacement of aging timber transoms installed on existing railway bridges along with the incorporation of a continuous walkway platform, which is proven to provide environmental, safety and financial benefits. Recent developments for alternative composite materials to replace timber components in railway infrastructure construction and maintenance demonstrate some compatibility issues with track stiffness as well as structural and geometrical track systems. Structural concrete are generally used for new railway bridges where the comparatively thicker and heavier fixed slab track systems can be accommodated. This study firstly demonstrates a novel and resilient alterative by incorporating steel-concrete composite slab theory and combines the capabilities of being precast and modulated, in order to reduce the depth, weight and required installation time relative to conventional concrete direct-fixation track slab systems. Clear benefits of the new steel-concrete composites are the maintainability and constructability, especially for existing railway bridges (or brown fields). Critical considerations in the design and finite element modelling for performance benchmarking of composite structures and their failure modes are highlighted in this paper, altogether with risks, compatibilities and compliances.