Full-scale Field Measurements Research Articles

Thunderstorm impact on the built environment: A full-scale measurement and post-event damage survey case study

This paper investigates the impact of an intense thunderstorm on the urban area of Sânnicolau Mare, Romania, based on the meteorological data collected by full-scale field measurement and the damage data of low-rise buildings obtained by post-event survey. The meteorological data throughout the entire thunderstorm process were collected from two sources, namely, a wind and structural monitoring system of a 50 m-tall lattice tower and a state-operated meteorological station, both located at the outskirts of the city. The damage data were collected by post-event in-situ survey with crowdsourcing techniques, providing information of both wind- and hail-induced damage to over 200 low-rise buildings. Based on the meteorological and damage data, the damage mechanisms were revealed by conducting forensic engineering analysis for two representative buildings which respectively sustained severe wind- and hail-induced damage. Moreover, the widely used estimation scales for wind intensities, such as the Fujita scale, were validated by anemometric records and damage observations. Finally, the feasibility of utilizing the hail-induced damage to building facades as a new indicator for the estimation of wind speed and direction was discussed. This study aims to further understand the impact of thunderstorms on low-rise buildings, so as to deliver essential information for their storm-resistant designs.

Unsteady loads on circular cylinder in cross-flow: An observation in natural wind and comparison with wind tunnel experiments

We present the synchronized unsteady wall pressure measurements performed at the circumference of a full scale 35 m circular chimney submitted to natural wind. The atmospheric turbulent boundary layer generates a turbulence intensity of 15 % at the altitude of the measurements and the corresponding Reynolds number is 1.13 106. For the first time, the steady and unsteady pressure distributions around the circumference are presented, despite large difficulties in the measuring process. The analysis of the pressure distribution using the bi-orthogonal decomposition (BOD) is a key factor in the success of the processing. By comparison with wind tunnel similar measurements, with 2D cylinders, the time-averaged pressure distribution is found between the one of a subcritical regime and a supercritical regime, slightly closer to the subcritical regime notably because the base pressure coefficients are similar. The atmospheric turbulence is an essential ingredient for the unsteady pressure response on the chimney, which generates high levels of RMS pressure, much higher than all those measured in wind tunnel, even under the turbulent flow generated by a grid. The analysis by BOD allowed the extraction of a term which is mainly generated by alternate vortex shedding. Despite a very noisy signal, the Strouhal number is determined to be 0.20–0.24. The corresponding shape of the pressure distribution is compared with those found in wind tunnel: it is shown that the full scale field measurements are close, but not identical, to the small scale measurements in wind tunnel on a rough cylinder submitted to a grid generated turbulent flow.

An approach to thermal modeling of power cables installed in ducts

The power cables laying in the urban areas require utilization of the protective ducts, mainly to facilitate the faulty section replacement. However, the use of cable ducts results in reduced capacity to dissipate generated heat to the surroundings. Thus, the thermal analysis of cables placed in ducts is very important for proper power cable operation. The thermal response of cables laid in mutual and in separate ducts, respectively, is considered at two values of current load. The full-scale field measurement setup is utilized to carry out the analysis of both steady-state and dynamic power cable heating under actual field conditions for the two backfill configurations. The measurement results provide the insight into the power cable heating dynamics related to the situations of a short-term over-loads and fault drive-through responses and also the opportunity to verify the proposed numerical approach based on the use of finite element method and the boundary conditions on the interior duct surface. The approach could be considered as a compromise between the standardized procedure and the tedious procedure involving the computational fluid dynamics simulations due to straightforward implementation and very good accuracy. The results obtained suggest that cables laid in mutual duct lead to a less favorable thermal situation when compared to cables laid in separate ducts. Also, the numerical results suggest that the use of non-uniform heat flux around the inner duct surface results in a significantly better agreement with measurements, compared to the purely numerical approach utilizing the concept of the effective thermal conductivity to model heat transfer in the air gap between cable and duct. Finally, the sensitivity analysis has been carried out to assess the effects of various backfill thermal conductivities and the ground surface temperature on the resulting thermal field. • Full scale field measurements. • Simplified approach for thermal field estimation when cabled are placed in ducts. • Nonuniform heat flux distribution along the cable duct is implemented. • Better agreement with measurements when non-uniform heat flux distribution is used. • Use of effective thermal conductivity results in notable temperature underestimation.

Геометрия контуров капельного увлажнения почв

Purpose: to determine dependencies and develop a methodology for calculating the geometric dimensions and constructing the outline of local moisture contours formed in the soil space during drip irrigation. Materials and methods. The factual basis of the development was the data of full-scale (field) measurements of the contours of the drip-moistened soil space and their office processing. The studies were carried out on experimental sites with different soil cover, represented by steppe, dry steppe and steppe-desert soil types: chernozems (ordinary and southern) and chestnut soils with a wide range of granulometric texture, water-physical properties and with different levels of pre-irrigation moisture, when ir-rigated with emitters productivity from 1,0 to 6,0 l/h. Results and discussion. During the study, the following things were considered as determining the process of contour formation and the contour geometry: soil conditions characterized by the physical clay content, the min-imum water capacity, bulk density and the level of pre-irrigation moisture; technological pa-rameters determined by the level of post-irrigation moisture, the given depth of soil moisture, the flow rate of drip micro-water outlets and the volume of water supply. Empirical depend-ences that allow determination of the linear dimensions, the wetted area dimensions and the volumes of moisture contours are obtained according to the given values: the physical clay content in soil within 18.0–77.0 % of the dry soil mass (DSM), the lowest moisture capacity in the range 16.5–32 % DSM, wetting depth from 0.5 to 1.2 m, additional irrigation moisture from 60 to 80 % of the level of the minimum water capacity, emitter flow from 1.0 to 6.0 l/h. Conclusion. A system of empirical dependencies has been obtained, and methods for predict-ing the external shape, linear, areal and volumetric dimensions of local moisture contours formed in the soil space during drip irrigation have been developed.

Simplified Model for Heat Transport for Cables in Pipes

This paper addresses challenges with modeling of heat transfer phenomenon for cables in duct or pipes when applying a numerical solution. Heat transport mechanisms between the cable and pipe surfaces are conduction, convection and radiation. Numerical calculation of convection when applying a finite element analysis (FEA), or other numerical tools requires heavy computation power and great skills of the program operator. In general, this is the most difficult part when modeling the heat transfer between the cable and the pipe surfaces and practitioners are often forced to use simplifications or approximate models. This paper introduces a simplified model where the contribution from convection is replaced by a heat source at the pipe wall and a corresponding heat sink at the cable. The phenomenon of air rising vertically in the tube resulting in the upper half of the pipe being heated more by convection than the lower half is also modelled. The simplified model is compared to both known models from thermodynamics, FEA including convection and laboratory as well as the full-scale field measurements. The simplified model shows good correspondence to both simulations and measurements, with the temperatures deviating by less than 1 °C.

A data-driven approach for fatigue life of water intake risers

Water intake risers are novel concept for cooling water transport from the sea to the floating facilities. The fatigue performance is key to design of the water intake risers. In this paper, the fatigue performance of a bundle of water intake risers is investigated for the first time using full-scale field measurements in combination with a finite element model. Through this approach, a data-driven model is developed to assess the fatigue damage of water intake risers. A fatigue analysis framework is proposed to calculate the bending stress along the risers based on the measured rotations at two locations of the risers. Compared to the conventional finite element analysis, this framework provides a more accurate and time-efficient solution for fatigue estimation, which helps the structural integrity of the water intake risers over their life cycle.

Design guidelines for reinforced concrete three-sided culverts

A comprehensive parametric study is conducted to investigate the structural performance of reinforced concrete (RC) three-sided culverts (TSCs) and the applied earth pressures. Nonlinear finite element models were established for a range of TSCs configurations and were validated using full-scale field measurements of three TSCs with spans of 7.3, 10.4, and 13.5 m. The parametric study covered a wide range of main design factors, including backfill height, installation method, backfill soil type and compaction level, and concrete compressive strength. The results demonstrated that embankment installation method resulted in slightly higher earth loads on the culvert top slab and sidewalls compared to trench installation method. The results revealed that vertical arching factors (VAFs) stipulated in the CHBDC (CSA, 2019) for B1 and B2 standard installations consistently overestimated the vertical earth pressure on the top slab. Therefore, the equation proposed by AASHTO (AASHTO LRFD, 2014) for evaluating VAFs was modified and proposed to evaluate vertical earth pressures for TSCs. It was found that culvert installation involving dumped soil or moderately compacted sidefill along with compacted backfill on the top slab significantly increased the vertical earth loads on the top slab, and adversely affected the structural performance of TSCs and their ultimate capacity. Therefore, these compaction scenarios should not be used in the construction of TSCs. The results also demonstrated that the predicted maximum backfill height at failure could increase by up to 50% when concrete with higher compressive strength (i.e., 60 MPa instead of 40 MPa) is used in manufacturing the RC TSCs. Finally, midspan vertical deflection limits are proposed to ensure that the crack width of the RC culvert satisfies the allowable limits considering soil-structure interaction effects.

Study on Full-scale Measurements of Wind Field Characteristics of Coastal Complex Mountainous Terrains

Based on full-scale wind field measurements of coastal complex mountainous terrains, data of fluctuating wind velocities at the height of 30m for four sites, including mountaintop and hillsides, are obtained. The wind load characteristics of mean wind velocities, wind directions, turbulence intensities and speed-up ratios of wind velocities are comprehensively examined. Results show that the maximum mean wind velocity at the mountaintop site is 12.4 m/s. The probability density distributions of mean wind velocities for the four measurement sites can be well represented by the Weibull probability model. The predominant wind directions are around the northeast and southwest. The longitudinal, lateral and vertical turbulence intensities decrease with the increase of mean wind velocities. The turbulence intensities for the mountaintop site are as many as 0.13,0.12 and 0.089 under maximum wind velocities, respectively for the previously mentioned three directions. The speed-up ratios of wind velocities between mountaintop and hillside sites are reduced, as the wind velocities increase. However, in cases of intensive wind with mean wind velocities larger than 8 m/s, the speed-up effects of wind velocities can also appear. The maximum speed-up ratio can reach 1.17.

Experimental Investigation on Coupled Vibration Features of Suspended Monorail Train–Bridge System under Constant Speed and Braking Conditions

Suspended monorail transportation (SMT) plays an important role in alleviating the urban traffic pressure, and its vehicle–bridge dynamic features are significantly different from those of the traditional railway. To grasp the coupled vibration features of suspended monorail train–bridge system (SMTBS), this paper presents a comprehensive experimental investigation on the vehicle–bridge vibrational responses under different operating conditions. First, based on the Chengdu SMT test line in China, a full-scale field measurement of the coupled vibration responses of the SMTBS is elaborately conducted under constant speed conditions. Then, the vibrational responses of the SMTBS are analyzed in the time and frequency domains to reveal its coupled vibration features and vibration transmission characteristics. Further, considering an extreme train operating condition, the vibrational responses of the SMTBS are tested and analyzed under train emergency braking; and the vibration features of the vehicle and bridge are examined for emergency braking, along with several key indexes evaluated for the train braking performance. Results show that the vibrational accelerations transmitted from the frame to the center pin and then to the carbody will be significantly decreased in turn, and the vibrational dominant frequencies of the bogie, center pin, and carbody mainly fall with 0–100[Formula: see text]Hz, 0–50[Formula: see text]Hz, and 0–20[Formula: see text]Hz, respectively. Under moving train loads, the box beam produces plentiful high-frequency vibrations and the vibrations transmitted from the driving track to the top plate are drastically reduced. The train braking significantly intensifies the car-body longitudinal vibration; however, it has small influences on the car-body vertical and lateral vibrations.

A deep learning augmented vision-based method for measuring dynamic displacements of structures in harsh environments

In this paper, a deep learning augmented vision-based method (DAVIM) is proposed for measuring structural displacement in harsh environments. DAVIM incorporates deep learning-based algorithms that include a Convolutional Neural Network (CNN) and a Generative Adversarial Network (GAN) for more accurate and robust sensing of the dynamics of structural models in wind tunnel tests or full-scale field measurements. The proposed method is first validated through numerical test including a discussion on the efficiency of CNN and GAN in really harsh environments. This is followed by three different kinds of experiments involving periodic vibration tests, motion of an aeroelastic model in a wind tunnel test and field measurements to effectively validate the proposed method from practical applications perspective. The proposed DAVIM exhibits a robust and superior performance compared to the traditional sensors (e.g., a laser displacement sensor and an accelerometer) and the Vision based vibration measurement (VVM) method. This is particularly the case when measuring large displacements with rigid-body rotational components and in long-term field measurements.

A Theoretical Model for Ship–Wave Impact Generated Sea Spray

AbstractSpray generated by ships traveling in cold oceans often leads to topside icing, which can be dangerous to vessels. Estimation of the spray flux is a first step in predicting icing accumulation. The amount of spray water, the duration of exposure to the spray, and the frequency at which the spray is generated are all important parameters in estimating the spray flux. Most existing spray flux formulae are based on field observations from small fishing vessels. They consider meteorological and oceanographic parameters but neglect the vessel behavior. Ship heave and pitch motions, together with ship speed, determine the frequency of spray events. Thus, the existing formulae are not generally applicable to different sizes and types of vessels. This paper develops simple methods to quantify spray properties in terms that can be applied to vessels of any size or type. Formulae to estimate water content and spray duration are derived based on principles of energy conservation and dimensional analysis. To estimate spray frequency considering ship motions, a theoretical model is proposed. The model inputs are restricted to ship’s principal particulars, operating conditions, and environmental conditions. Wave-induced motions are estimated using semi-empirical analytical expressions. A novel spray threshold is developed to separate deck wetness frequency from spray frequency. Spray flux estimates are validated against full-scale field measurements available in the open literature with reasonable agreement.

Full-scale deformation measurements of a wind turbine rotor in comparison with aeroelastic simulations

Abstract. The measurement of deformation and vibration of wind turbine rotor blades in field tests is a substantial part of the validation of aeroelastic codes. This becomes highly important for modern rotors as the rotor size increases, which comes along with structural changes, resulting in very high flexibility and coupling between different vibration modes. However, performing full-scale field measurements for rotor blade deformation is not trivial and requires high temporal and spatial resolution. A promising deformation measurement technique is based on an optical method called digital image correlation (DIC). Recently, DIC measurements on a Siemens Gamesa SWT-4.0-130 test turbine were performed on the tip of all blades in combination with marker tracking at the hub for the first time with synchronised measurement of the inflow conditions by a ground-based lidar. As the turbine was additionally equipped with strain gauges in the blade root of all blades, the DIC results can be directly compared to the actual prevailing loads to validate the measurement method. In the end, an example for a comparison of the measured deformations and torsion with aeroelastic simulations is shown in the time and frequency domain. All in all, DIC shows very good agreement with comparative measurements and simulations, which shows that it is a suitable method for measurement of deformation and torsion of multi-megawatt wind turbine rotor blades.

Drift-Off Study in Drilling Vessels Comparing Numerical Model and Full-Scale Field Measurements

Abstract In drilling vessels, the dynamic positioning (DP) system has a great importance for the operation, since it ensures the station-keeping ability for the drilling operation. However, an emergency situation involves ungoverned drift due to problems associated with the DP system failures, such as thrusters, generators, powerbus, or control system. During this situation, the vessel drift is subjected to the influence of environmental conditions and the drift can lead to collisions with floating obstacles or submerged systems, wellhead emergency disconnection, damage to equipment and potentially causing major environmental disasters. It is then necessary to define a safety region for the drilling ship operation and to determine the limiting operation offset that the drilling vessel can disconnect from the wellhead without damage to any equipment. This offset limit is obtained through a riser analysis and drift-off study, important inputs for the Well Specific Operating Guidelines (WSOG). A validated time-domain simulator is required and able to predict the vessel drift trajectory after the DP failure under several environmental conditions. The aim of this work is to present a large set of model and full-scale drift tests and the validation of a time-domain numerical simulator (Dynasim), based on the main parameters of the drift tests: drift distance, heading variation, and trajectory. The comparisons between the numerical simulation results with full- and model-scale data demonstrated the accuracy of the numerical model, confirming that the simulator is a reliable tool to predict the motion of a drilling vessel after a blackout.

Impacts of fish farm structures with biomass on water currents: A case study from Frøya

Impacts of aquaculture fish cages and their biomass on the local water current field is investigated with extensive, full scale field measurements. This is important for the fish welfare as well as for waste transport from open fish cages. The relationships between the current flow rate at various locations close to fish cages are examined at an aquaculture marine site close to Frøya, Norway. This is an area with a complex current pattern due to the bathymetry, rocks and islands, coast current and strong wind conditions. An array of ADCPs (Acoustic Doppler Current Profilers) measured currents. Moreover, CTD and separate temperature profiler instruments were made in order to analyze flow stratification. Two different measurement periods are analysed with 1) small fish size (0,2–0,4 kg) and 2) large fish size (1 kg–5 kg). The field measurements indicate some impact from the biomass on the measured current flow at distances from 90 to 320 m around it. The results are supported by results from the numerical ocean model SINMOD (SINtef MODel).

3D response analysis of a shield tunnel segmental lining during construction and a parametric study using the ground-spring model

In this research, an analysis method aiming as a tool to investigate the behavior of a tunnel lining during construction is developed based on a nonlinear ground-spring model in conjunction with a finite element method. A nonlinear ground-spring model that considers yield pressures is proposed and implemented into the numerical analysis. All relevant components of the shield tunnel construction process including the TBM, jack thrust force, shield tail wire brush, segmental lining, key-segment and ring and segment joints and proper interactions are considered in the analysis model. The reliability of the developed method is verified by comparing the analysis results with the full-scale test and field measurements of a previous study. The developed analysis method could reasonably reproduce the responses of a segmental lining at various stages with special attention during construction. A series of parametric analyses are conducted to highlight the robustness of the developed method to capture the effect of the key factors on the structural behavior of the segmental lining during construction. The effects of the tunnel depth, forces from eccentric jack thrust together with shield tail wire brush and position of key segment on the induced lining stresses can be well captured.

Calibration of the Swedish studded tyre abrasion wear prediction model with implication for the NORTRIP road dust emission model

ABSTRACT An experimentally based prediction model of road abrasion wear due to studded tyres is available in Sweden and has been found to work well. However, it has not been validated since 2007, and since then road surfaces and tyre design have developed, and the question has arisen regarding the model’s current validity. The abrasion wear model is used in the NORTRIP emission model (NOn-exhaust Road Traffic Induced Particle emission modelling), and the effect of a recalibrated abrasion wear model on the emission model is shown. In this paper, the abrasion wear model is compared to full-scale field measurements at several recently constructed roads in Sweden to investigate its validity, while also proposing changes to allow for continued use. It is concluded that the model overestimates the wear and an update is suggested. In addition, the impact on NORTRIP emission predictions is briefly investigated. There were also indications that NORTRIP is affected by the abrasion model overestimating the contribution of pavement wear to the particle emissions.

Effect of turbulence modeling schemes on wind-driven rain deposition on a mid-rise building: CFD modeling and validation

Quantification of wind-driven rain (WDR) is important for designing building envelope to minimize moisture-related issues. With advancements in Computational Fluid Dynamics (CFD) modeling, it is becoming a more readily accepted tool for WDR studies. The current study focuses on validation of CFD modeling of WDR on a mid-rise building. The accuracy of WDR modeling is dependent upon the accurate wind flow modeling. The influence of turbulence modeling on wind flow around and WDR deposition on a six-story building is investigated. Three turbulence models, Realizable k-ε, Standard k-ω, and k-ω SST along with log-law and power-law inlet velocity profiles, are studied. Wind-tunnel measurements were carried out to validate wind flow simulations. WDR simulation results are compared to full-scale field measurements. It is shown that stand-alone building solution to such simulations is possible and, in some cases, recommended. Wind around the surrounded building is altered on a 5% margin by the choice of turbulence scheme. Standard k-ω with log-law inlet velocity profile, having wind and WDR at 20% and 25% average error range, performs the best on a stand-alone building. However, the influence of turbulence model and inlet velocity profile on WDR simulation is negligible for the surrounded building.

Buoyant flows in street canyons: Comparison of RANS and LES at reduced and full scales

Reduced-scale experiments and full-scale field measurements show contradictory buoyancy effects from heated windward walls. Reduced-scale experiments exhibit significant thermal effects, but full-scale field measurements show a negligible thermal effect on the overall flow fields. This paper investigates this discrepancy by using at both scales Computational Fluid Dynamics simulations with Reynolds-Averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES). Compared to experimental and field measurements, RANS models perform well at reduced scale but over-predict the thermal effects of heated windward walls at full scale. On the other hand, LES results agree well with measurements at both scales. Therefore, LES should be used for full-scale simulations of street canyon flows with heated windward walls. To date, there has been no explanation for the discrepancy of opposing thermal effects between reduced-scale experiments and full-scale field measurements although Richardson number similarity is satisfied. We provide an explanation by showing that in reduced-scale experiments with heated windward walls, the assumption of Reynolds number independence is invalid. In canyon flows with thermally induced buoyancy, unless the flow is proven independent of both Reynolds number and Grashof number, we should not generalize results from reduced-scale experiments to full-scale street canyons.

Numerical Investigations on District Heating Pipelines Under Combined Axial And Lateral Loading

Within the design process of district heating networks, the soil resistances in axial and lateral pipeline direction are commonly treated independently as friction resistance and bedding pressure. However, at curved segments or near ellbows, these resistances occur simultaneously and affect each other. The state of knowledge regarding this topic is summarized, and it is shown that only limited information exists for this case of loading.Therefore, a three-dimensional finite element model was developed, using the sophisticated concept of hypoplasticity as an advanced constitutive model for the bedding material. This soil model is able to account for dilatancy, barotropy and pycnotropy of granular soils. Subsequently, variations of the loading direction were performed for a reference system. The investigations give a good insight into the behaviour of district heating pipelines under combined loading, showing the interdependency of skin friction resistance and bedding pressure. We present a design approach which incorporates interaction terms, derived from the presented investigations. Results gained from these investigation are then transferred to the academic district heating network design tool IGtH-Heat, to evaluate in which manner the incorporation of coupling terms between bedding and friction resistance influences the pipe-soil interaction. Additionally, a temperature dependent formulation of maximum friction resistance is adopted to incorporate the effects of radial pipe displacement. Thereby we demonstrate that the predicted pipeline’s displacement significantly change when these effects are taken into account. Using this new formulation, model predictions are compared to data from full scale field measurements.

Flows across high aspect ratio street canyons: Reynolds number independence revisited

The Reynolds number for flow in a street canyon, Re = UrefH/ν (where Uref is a reference velocity, H the street canyon height, and ν the kinematic viscosity), cannot be matched between reduced-scale experiments and full-scale field measurements. This mismatch is often circumvented by satisfying the Re independence criterion, which states that above a critical Re (Rec), the flow field remains invariant with Re. Rec = 11,000 is often adopted in reduced-scale experiments. In deep street canyons with height-to-width aspect ratio ≥ 1.5, reduced-scale experiments have shown two recirculation vortices induced by the mean flows, but full-scale field measurements have observed only one vortex. We investigated this discrepancy by conducting water channel experiments with Re between 104 and 105 at three aspect ratios. The canyons with aspect ratio 1.0 have Rec = 11,000, the canyons with aspect ratio 1.5 have Rec between 31,000 and 58,000, while the canyons with aspect ratio 2.0 have Rec between 57,000 and 87,000. Therefore, the widely adopted Rec = 11,000 is not applicable for canyons with aspect ratio greater than 1.5. Our results also confirm that there is only one vortex in deep canyons at high Re. This single-vortex flow regime could change our fundamental understanding of deep canyons, which are often assumed to exhibit multiple-vortex flow regimes. Applications such as numerical model validation based on the multiple-vortex regime should be revisited. Our experimental data with Re up to 105 could be used to validate numerical models at high Re.