Wind-induced dynamic excitation is becoming a governing design action determin-ing size and shape of modern Tall Timber Buildings (TTBs). The wind actions generate dynamic loading, causing discomfort or annoyance for occupants due to the perceived horizontal sway – i.e. vibration serviceability failure. Although some TTBs have been instrumented and meas-ured to estimate their key dynamic properties (natural frequencies and damping), no systematic evaluation of dynamic performance pertinent to wind loading has been performed for the new and evolving construction technology used in TTBs. The DynaTTB project, funded by the Forest Value research program, mixes on site measurements on existing buildings excited by heavy shakers, for identification of the structural system, with laboratory identification of building elements mechanical features coupled with numerical modelling of timber structures. The goal is to identify and quantify the causes of vibration energy dissipation in modern TTBs and pro-vide key elements to FE modelers.

The first building, from a list of 8, was modelled and tested at full scale in December 2019. Some results are presented in this paper. Four other buildings will be modelled and tested in spring 2020.

Wind-induced dynamic excitation is a governing design action determining size and shape of modern Tall Timber Buildings (TTBs). The wind actions generate dynamic loading, causing discomfort or annoyance for occupants due to the perceived horizontal sway, i.e. vibration serviceability problem. Although some TTBs have been instrumented and measured to estimate their key dynamic properties (eigenfrequencies, mode shapes and damping), no systematic evaluation of dynamic performance pertinent to wind loading had been performed for the new and evolving construction technologies used in TTBs. The DynaTTB project, funded by the ForestValue research program, mixed on site measurements on existing buildings excited by mass inertia shakers (forced vibration) and/or the wind loads (ambient vibration), for identification of the structural system, with laboratory identification of building elements mechanical features, coupled with numerical modelling of timber structures. The goal is to identify and quantify the causes of vibration energy dissipation in modern TTBs and provide key elements to finite element models. This paper presents an overview of the results of the project and the proposed Guidelines for design of TTBs in relation to their dynamic properties.

In timber buildings, elastomers are commonly used to decrease the sound transmission between apartments. Detailed properties of the elastomers are needed in order to model them in a correct yet computational efficient manner. In earlier studies, dynamic experiments have been made on elastomer strips half embedded. However, the sidewise effects need to be further evaluated. In this study, the elastomers are evaluated quasi-statically in different directions, having continuous as well as intermittent distributions, being plane supported or half embedded. An FE-model has been developed using data stemming from the quasi-static tests together with damping estimates stemming from vibrational tests.

Elastomers are commonly used to decrease the sound transmission between apartments in timber framed houses. Inprevious studies, different types of connections have been evaluated. However, the frequency dependent dynamic propertiesin different directions of a connection including elastomers are not fully investigated yet. Previous studies have actuallyshown that elastomers cause the vibrations to increase in the direction perpendicular to the applied load within the lowfrequency span. The properties of the elastomers are needed in order to model the dynamic behaviour and thereby be ableto predict sound and vibration transmissions in wooden houses in the future. With known properties, the elastomerconnections can be modelled using springs and dashpots. In this study, dynamic experiments have been made on elastomerstrips half embedded. The test setup has been subjected to various loads using an electromagnetic shaker. The responseshave been measured and evaluated using modal analysis. With different loads, non-linear characteristics of the elastomers’behaviour have been obtained. The elastomers have also been tested quasi-statically, to obtain a load-deflection curve.Finally, the estimated properties of the elastomers have been included in an FE model using springs and the analyticalresults are compared with the experimental results.

A finite element (FE) analysis of a model representing a mock-up structure previously investigated experimentally is investigated in this study. The aim is to make a correlation and calibration between test and analysis of the full scale wooden structure; both eigenmodes and acceleration levels are compared. Large scatter is found in material properties used for light weight wooden structures in literature. In this study, a parameter evaluation is therefore made to show how different properties influence the dynamic behaviour of the structure. It is shown that the wood beam material properties influence the behaviour of the light weight wooden structure FE model most.

Two types of junctions are modelled and evaluated; a tied connection is used to simulate screwed junctions and spring/dashpot elements are used to represent elastomer junctions between the floor and the walls. The springs and dashpots used to model the elastomer in the junction work well in the bearing direction but need to be improved to obtain correct rotational stiffness, shear motion and friction. There are still many unknown parameters in a complex wooden structure that remain to be investigated. However, the results presented in this paper add data to be used for FE modelling of a complex wooden structure.

In lightweight structures it is common to use damping material in junctions to decrease sound transmission. In field measurements, the damping properties of the structure are easily overestimated due to the omnipresent energy losses to the surroundings. Thus, reliable estimates of structural properties cannot be guaranteed.

Vibrational tests were done on a full scale wooden construction, consisting of a floor and supporting beams, representing walls, to investigate the effect of different junctions. Totally seven different setups were made using the same building components. In one setup the floor and the walls were screwed together, in five setups different elastomers was positioned between the floor and the walls and in the last setup the floor was resting free on top of the walls. A shaker, with pseudorandom excitation, was used for the excitation of the structure and accelerometers were used for response measurements. The effect of the junction was investigated by studying the acceleration levels in the edge part of the floor-wall junction in different directions.

Modal data, extracted from test data using experimental modal analysis, form input and validation data for the following finite element (FE) analysis. Two FE models; modeling one elastomer and the screwed setup, are used for the studies.

The aim was to study if the eigenmodes rendering the acceleration levels are similar in test and in analysis, using common material properties.

The results from correlation between test and analytical results show that the material properties of the wood need to be known better; more sophisticated models are needed to fully simulate the dynamic behavior of the structure. Anyhow, with the used properties the mode shapes are captured fairly well in the lower frequencies. Furthermore, the experiment shows that the damping properties of the junction material have a major influence on the behavior of the structure.

To predict and possibly, when needed to fulfil regularizations or other requirements, change the design to lower the impact sound transmission in light weight buildings prior to building, dynamically representative calculation models of assemblies are out most important. The quality of such models depends on the descriptions of the components themselves but also of the representation of the junction connecting the building components together. The material properties of commonly used components have a documented spread in literature. Therefore, to validate junction models, the dynamics of the assembly components at hand have to be known. Here, the dynamic properties of a number of component candidates are measured using hammer excited vibrational tests. Some of the components are selected to build up wooden assemblies which are evaluated both when they are screwed together and when they are screwed and glued together. The focus is here on achieving representative finite element models of the junctions between the building parts composing the assemblies.

Elastomers are commonly used to decrease the sound transmission between apartments in timber framed houses. In previous studies, different types of elastomers have been evaluated experimentally. The wooden assemblies, in which elastomers were used in the connections, showed that elastomers cause the vibrations to increase in the direction perpendicular to the applied load within the low frequency span.

In this study, the effects on acceleration, depending on how the elastomers are placed are studied. The cases having the elastomer continuous, placed as intermittent pieces or positioned half embedded in the junctions are evaluated.

The frequency dependent properties of the elastomers are needed in order to model the dynamic behaviour and thereby be able to predict sound- and vibration transmission in wooden houses. Here, the properties of a wooden construction having different elastomers connections are studied to enable simulations of the behaviour of the elastomers in a FE model in the future.

In many cases where operational modal analysis is of interest, harmonic components are disturbing the estimation of modal parameters. Sometimes the harmonics can be included in the parameter estimation process and subsequently removed (because the damping values become unrealistically low). However, this is difficult if a natural frequency is very close to, or coincides with, a harmonic. In this paper we investigate a recently proposed method for removing harmonics when estimating spectral densities for operational modal analysis. The method is essentially based on removing the harmonics in a periodogram, prior to estimating the spectral density by smoothing the same periodogram. This makes it a very time efficient method, as the harmonic removal is integrated into the spectral analysis process. To produce data for testing the method, a finite element dynamic model representing a wind turbine was created. The MATLAB-based finite element code CALFEM was used to achieve a flexible description of the tower. An aerodynamic force representation excited the rotating structure. An unbalance in one of the blades was introduced to produce a harmonic at the rotation speed of the turbine. To validate the efficiency of the harmonic removal, modal parameters were estimated using simulated data prior to, and after, removing the harmonics. The results show that the harmonic removal with the proposed method is efficient.

Responses of mechanical systems are often studied using numerical time-domain methods. Discrete excitation forces require a transformation of the dynamic system from continuous time into discrete time. Such a transformation introduces an aliasing error. To reduce the aliasing error, different discretization techniques are used. The bias errors introduced by some discretization techniques are studied in this paper.

Algebraic expressions of the bias error obtained for some discretization methods are presented. The bias error depends on the assumption of the characteristics of the load between two subsequent time steps; here the zero-order, first-order and Lagrange second-order assumptions are studied. Different simulation methods are also studied for numerical evaluation of the derived theoretical bias errors. The discretization techniques are implemented for Runge-Kutta, the Digital Filter method and for the Pseudo Force in State Space method.

The study is carried out for both a linear and a nonlinear system; two numerical examples assist in evaluating the theory. Perfect matches between the numerically estimated bias errors and the theoretical ones are shown. The results also show that, for the nonlinear example, the fourth order Runge-Kutta method is less accurate than the Digital Filter and the used single step Pseudo Force in State Space method.

In practice, most mechanical systems show nonlinear characteristics within the operational envelope. However, the nonlinearities are often caused by local phenomena and many mechanical systems can be well represented by a linear model enriched with local nonlinearities. Conventional nonlinear response simulations are often computationally intensive; the problem which becomes more severe when large-scale nonlinear systems are concerned. Thus, there is a need to further develop efficient simulation techniques. In this work, an efficient simulation method for large-scale systems with local nonlinearities is proposed. The method is formulated in a state-space form and the simulations are done in the Matlab environment. The nonlinear system is divided into a linearized system and a nonlinear part represented as external nonlinear forces acting on the linear system; thus taking advantage in the computationally superiority in the locally nonlinear system description compared to a generally nonlinear counterpart. The triangular-order hold exponential integrator is used to obtain a discrete state-space form. To shorten the simulation time additionally, auxiliary matrices, similarity transformation and compiled C-codes (mex) to be used for the time integration are studied. Comparisons of the efficiency and accuracy of the proposed method in relation to simulations using the ODE45 solver in Matlab and MSC Nastran are demonstrated on numerical examples of different model sizes.

Correlation and calibration using test data are natural ingredients in the process of validating computational models. Model calibration for the important subclass of nonlinear systems which consists of structures dominated by linear behavior with the presence of local nonlinear effects is studied in this work. The experimental validation of a nonlinear model calibration method is conducted using a replica of the École Centrale de Lyon (ECL) nonlinear benchmark test setup. The calibration method is based on the selection of uncertain model parameters and the data that form the calibration metric together with an efficient optimization routine. The parameterization is chosen so that the expected covariances of the parameter estimates are made small. To obtain informative data, the excitation force is designed to be multisinusoidal and the resulting steady-state multiharmonic frequency response data are measured. To shorten the optimization time, plausible starting seed candidates are selected using the Latin hypercube sampling method. The candidate parameter set giving the smallest deviation to the test data is used as a starting point for an iterative search for a calibration solution. The model calibration is conducted by minimizing the deviations between the measured steady-state multiharmonic frequency response data and the analytical counterparts that are calculated using the multiharmonic balance method. The resulting calibrated model's output corresponds well with the measured responses.

Mechanical systems having presence of nonlinearities are often represented by nonlinear ordinary differential 5 equations. For most of such equations, exact analytic solutions are not found; thus numerical techniques have to be used. 6 In many applications, among which model calibration can be one, steady-state frequency response functions are the desired 7 quantities to calculate. 8 The objective of this paper is to compare the performance of computations of nonlinear frequency response functions 9 (FRFs) calculated directly within the frequency domain, using the Multi-Harmonic Balance method, with the time-domain 10 methods Runge–Kutta, Newmark and Pseudo Force in State Space (PFSS). The PFSS method is a recently developed state- 11 space based force feedback method that is shown to give efficient solutions. 12 The accuracy and efficiency of the methods are studied and compared using a model of a cantilever beam connected to a 13 non-linear spring at its free end.

With increasing demands on more flexible and lighter engineering structures, it has been more common to take nonlinearity into account. Model calibration is an important procedure for nonlinear analysis in structural dynamics with many industrial applications. Pretest planning plays a key role in the previously proposed calibration method for nonlinear systems, which is based on multi-harmonic excitation and an effective optimization routine. This paper aims to improve the pretest planning strategy for the proposed calibration method. In this study, the Fisher information matrix (FIM), which is calculated from the gradients with respect to the chosen parameters with unknown values, is used for determining the locations, frequency range, and the amplitudes of the excitations as well as the sensor placements. This pretest planning based model calibration method is validated by a structure with clearance nonlinearity. Synthetic test data is used to simulate the test procedure. Model calibration and K-fold cross validation are conducted for the optimum configurations selected from the pretest planning as well as three other configurations. The calibration and cross validation results show that a more accurate estimation of parameters can be obtained by using test data from the optimum configuration.

Nonlinear finite element models are often validated using experimental data. A previously proposed calibration method, which concerns pre-test planning, multi-sinusoidal excitation and an effective optimization routine, is improved with an extended version of the pre-test planning. The improved method is validated using a test structure with a clearance type nonlinearity. From the pretest planning, an optimal configuration for the data acquisition is determined. The multi-harmonic nonlinear frequency response functions (FRFs) of the structure under test are then generated by a multi-sinusoidal excitation. Model calibration is conducted by minimizing the difference between the experimental multi-harmonic nonlinear FRFs and their analytical counterparts. The uncertainties of the estimated parameters are assessed by a k-fold cross validation, which confirm that the uncertainties of the estimated parameters are small when the optimal configuration is applied.

In industry, linear FE-models commonly serve as baseline models to represent the global structural dynamics behavior. However, available test data may show evidence of significant nonlinear dynamic characteristics. In such a case, the baseline linear model may be insufficient to represent the dynamics of the structure. The causes of the nonlinear characteristics may be local in nature and the remaining parts of the structure may be satisfactorily represented by linear descriptions. Although the baseline model can then serve as a good foundation, the physical phenomena needed to substantially increase the model's capability of representing the real structure are most likely not modelled in it. Therefore, a set of candidate nonlinear property parameters to control the nonlinear effects have to be added and subjected to calibration to form a credible model. The selection of the calibration parameters and the choice of data for a calibration metric form a coupled problem. An over-parameterized model for calibration may result in parameter value estimates that do not survive a validation test. The parameterization is coupled to the test data and should be chosen so that the expected co-variances of the chosen parameter's estimates are made small. Accurate test data, suitable for calibration, is often obtained from sinusoidal testing. Because a pure mono-sinusoidal excitation is difficult to achieve during a test of a nonlinear structure, the excitation is here designed to contain sub and super harmonics besides the fundamental harmonic. The steady-state responses at the side frequencies are shown to contain valuable information for the calibration process that can improve the accuracy of the parameter estimates. The nonlinear steady-state solutions can be found efficiently using the multi-harmonic balance method. In this paper, synthetic test data from a model of a nonlinear benchmark structure are used for illustration. The model calibration and an associated K-fold cross-validation are based on the Levenberg-Marquardt and the undamped Gauss-Newton algorithm, respectively. Starting seed candidates for calibration are found by the Latin hypercube sampling method. The realization that gives the smallest deviation to test data is selected as a starting point for the iterative search for a calibration solution. The calibration result shows good agreement with the true parameter setting, and the K-fold cross validation result shows that the variance of the estimated parameters shrinks when adding sub and super harmonics to the nonlinear frequency response functions.

Large linear finite element models are commonly used in industry to represent global structural behavior and such models are often validated by use of data from vibrational tests. The validated models serve to predict the structural responses due to dynamic loads. Hence, it is important to have models that are able to represent the structural dynamics within the given operating envelope. When test data show proof of non linear behavior, a linear model may not be able to represent the dynamics well enough and thus a modification of the model is required. The main part of the structure may have a linear characteristic whereas localized physical processes can be sources of the observed nonlinearities. Model calibration of such locally nonlinear structures is studied in this paper. Specifically, the calibration process including the selection of appropriate data to be used for calibration of the model parameters chosen is treated. Here, synthetic test data stemming from a model of the Ecole Centrale de Lyon (ECL) nonlinear benchmark are used.

Model correlation and model calibration using test data are natural ingredients in the process of validating computational models. Here, model calibration for the important sub-class of non-linear systems consisting of structures dominated by linear behavior having presence of local non-linear effects is studied. The focus is on the selection of uncertain model parameters together with the forming of the objective function to be used for calibration. To give precise estimation of parameters in the presence of measurement noise, the objective function data have to be informative with respect to the parameters chosen. Also, to get useful data the excitation force is here designed to be multi-harmonic since steady-state responses at the side frequencies are shown to contain valuable information for the calibration process. In this paper, test data from a replica of the Ecole Centrale de Lyon (ECL) nonlinear benchmark together with steady-state solutions stemming from calculations using the Multi-Harmonic Balancing method are used for illustration of the proposed model calibration procedure.

Ground Vibration Tests have been performed on a replica of the Group for Aeronautical Research and Technology in Europe (GARTEUR) testbed structure SM-AG19. The aim of the Ground Vibration Tests was to study the impact on modal data stemming from the test data, from the boundary conditions used to mimic a free-free condition. For the tests an air-spring support system was designed with the aim to give a behaviour that is in resemblance with the behaviour of real aircraft test conditions.

To eliminate a potential, unwanted, impact on the test results generated by the wing to fuselage interface as it was designed for the original structure (SM-AG19), a deviation from the original interface has been made on the structure for this particular study.

The most popular single-number quantities (SNQs) of impact sound insulation in Europe are L'n, w and L'nT, w. They are based on measurements within 100-3150 Hz. Recently, it was proposed that the measurements should be extended down to 25 Hz for wooden floors, and L'nT, w+CI, 25 should replace L'nT, w. The purpose of this study is to analyze which of the two SNQs, Ln, w or LnT, w+CI, 25, predicts the annoyance of natural impact sounds better for wooden floors. We conducted a psychoacoustic experiment, where 52 participants rated the annoyance of 75 impact sounds. As stimuli, five types of natural impact sounds were used. They were recorded for 15 different wooden floors built in an impact sound insulation laboratory, where also their SNQs were measured. Based on correlation analysis, Ln, w explained annoyance of natural impact sounds equally well or better than Ln, w+CI, 25, depending on impact sound type Therefore, based on perception, it seems to be sufficient to conduct measurements within 100-3150 Hz for wooden floors and assess their sound insulation using L'nT, w or L'n, w © 2023 First author et al. This is an open-access article distributed under the terms of the Creative Commons Attribution 3.0 Unported License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

In a Finnish-Swedish consortium project, a large amount of sound insulation tests wasconducted for several intermediate floors in laboratory conditions to serve variousscientific research questions. The dataset contains 30 wooden and 8 concreteconstructions which are commonly used between apartments in multistorey buildings.Impact sound insulation was determined according to ISO 10140-3 standard usingboth tapping machine and rubber ball as standard sound sources. Airborne soundinsulation was determined according to the ISO 10140-2 standard. The data arespecial since they have a broad frequency range: 20-5000 Hz. Data are reported in1/3-octave frequency bands and the single-number values of ISO 717-1 and ISO 717-2are also reported. Detailed construction drawings are available for all reportedconstructions. The data are highly valuable for research, education, and developmentpurposes since all data were obtained in the same laboratory (Turku University ofApplied Sciences, Turku, Finland), and all the constructions were built by the same installation team.

Wooden floors usually have worse impact sound insulation (ISI) at low frequencies than concrete floors having the same rating level. Rating level is usually expressed by single-number quantities (SNQs), such as weighted impact sound pressure level Ln,w. Psychoacoustic research among wooden floors is very limited although a controlled laboratory experiment is the strongest method to point out the most adequate SNQs to be declared for the floors. The purpose of our study was to determine how four standardized SNQs of ISO 717-2, Ln,w, Ln,w +CI, Ln,w +CI,50, and LiA,Fmax,V,T, and a recently proposed SNQ, Ln,w +CI,25, are associated with the annoyance of natural impact sounds transmitted through wooden floors. Fifteen floors were built in the laboratory based either on cross laminated timber (heavy) or open box wood (light) slabs. Different coverings and suspended ceilings were applied on these slabs. The ISI was tested within 25-3150 Hz using both tapping machine and rubber ball. Thereafter, five natural impact sounds were recorded for each floor: rubber ball drops, steel ball drops, walking, jumping, and chair pushing. Fifty-two people rated the annoyance of these 75 recorded natural impact sounds in psychophysics laboratory. Annoyance was best associated with Ln,w for all the five impact sound types. That is, measurement of ISI within 100-3150 Hz is sufficient from subjective point of view. All four SNQs based on tapping machine explained annoyance better than the SNQ based on rubber ball. Our results can significantly guide the future research, development, and regulations of wooden floors.

Recently, a lot of work has been made on modeling, testing and calibrating Ampair 600W wind turbine blades, owing to the use of that turbine as a test bed structure for the Dynamic Substructuring Focus Group within the Society of Experimental Mechanics. In Sweden alone, more than 20 blades have been tested for dynamical properties, geometrical differences and material properties as was presented in several papers at IMAC XXXI. The quantity of blades, originating from different manufacturing batches, makes them ideal for investigations of component variability.

In this paper, measurement variability predominantly stemming from the difference between individual blades is propagated backwards to model parameters, using model calibration techniques, in an effort to quantify their uncertainties. The coupling between spread in structural properties such as mass, center of gravity together with blade twist angles and spread in the resulting blade dynamics is shown.

During the last years the interest in multi-storey timber buildings has increased and several medium-to-high-rise buildings with light-weight timber structures have been designed and built. Examples of such are the 8-storey building “Limnologen” in Växjö, Sweden, the 9-storey “Stadthouse” in London, UK and the 14-storey building “Treet” in Bergen, Norway. The structures are all light-weight and flexible timber structures which raise questions regarding wind induced vibrations. This paper will present a finite element-model of a 22 storey building with a glulam-CLT structure. The model will be used to study the effect of different structural properties such as damping, mass and stiffness on the peak acceleration and will be compared to the ISO 10137 vibration criteria for human comfort. The results show that it is crucial to take wind-induced vibrations into account in the design of tall timber buildings.

There is an increasing need for an effective monitoring strategy for the performance and condition of Down The Hole drilling. To achieve that, it is important to gain knowledge in the physics involved in Down The Hole drilling processes.A logical way to gain such understanding is to develop simulation models that are capable to represent the process. That requires physical understanding and thus, it is an iterative process. To capture the physics, it is essential to couple the axial impact, and the subsequent axial motion, with the rotation of the drill. The indentation into the rock due to impact and the subsequent resistance against rotation will couple the rotation to the axial motion and vice versa. The scenario is complicated due to the non-linear nature in the contacts and the varying stiffness of the rock.This paper presents a methodology that can be used to couple the axial and rotational motions of the DTH drills and explores the pros and cons of such a 3D simulation model.Keywords: DTH, 3D simulation, Condition monitoring

Reliable simulations of the DTH drilling cycle are important in understanding the physics related todrilling, which in turn enables development of robust performance and condition monitoring methodologies. The DTH models available today model different aspects of the system like impact, hydraulics etc. separately. There are models available that incorporates hydraulics/pneumatics with onedimensional structural dynamics of the system. A common drawback of such models is that the effectof rotation is neglected. In reality rotation is an integral part of the DTH system and is interconnectedwith other parameters of drilling. This paper focuses on a simple model that combines rotation of thedrill string with the impact and hydraulic mechanics. The aim is to build upon this basic model tofacilitate the development of a more robust and accurate model that represents the condition andperformance monitoring problem.

Automation of the drilling process is a widely spread goal in the rock excavator industry. An intermediate step can be to assist a manual drilling process by informing the operator of the quality of the drilling. To reach the goals, it is thus imperative to have a high performance monitoring system based on physics involved in the drilling process. A necessity to develop such an information system, is insight into the physics involved in the drilling process. This can be gained by using combinations of simulations, lab tests and in-situ tests.

Here, a 1D model representing Down The Hole (DTH) drilling is used. Such a model can be further developed to simulate good and bad performance of drilling. The resulting vibration responses, hydraulic pressure responses, etc. of the system can be analyzed with the purpose to identify possible sources of informative data which can be measured and recorded during a real world rock drilling operation.

Here, a simplified 3D model of the DTH drilling system involving the bit, hammer and the drill string is also made and used together with boundary conditions constituting a simplified model of the rock. The aim here is to find a computationally efficient 3D modeling methodology to simulate the drilling for various conditions, due to various drilling parameter settings. The aim is to develop a 3D model that can be refined further and can be used extensively to understand the DTH drilling process in order to facilitate performance monitoring and in the end automized DTH drilling.

Optimizing the performance for down the hole (DTH) drills is becoming increasingly important. This is due to that the industry is becoming highly competitive and therefore there is an ever-increasing demand for improving the efficiency of the drilling process. To do this, it is important to have a robust monitoring system in place that should be based on in-depth knowledge of the underlying physics of the drilling system and process. Such a system will assist drillers in improving the perfor-mance e.g. by providing recommendations concerning the settings of the drilling. To understand the performance of the system, it is very important to understand the information that can be extracted from different drilling related quantities. In this work, information obtained from the pressure signals from the feed/holdback line, impact pressure line and rotation line together with vibration signals measured with the aid of accelerometers mounted at specific locations on the drill rig are discussed. For instance, spectral properties of these quantities for good and bad drilling cases are investigated. The results indicate correlations, to some extent, between the spectral properties and the quality of the drilling.

The drilling industry is steadily moving towards automation. To have a better control over the drilling operation and to optimize the drilling performance, it is necessary to have a good understanding of the physics involved in the process. A good simulation model of the drilling process/system would be of great value in assisting this and in enabling the development of strategies to optimize it. A representative simulation model can provide insights into various phenomena that appear during drilling for different drilling conditions. Such a model is also likely to be of assistance in preparing various measurements. Issues such as choosing the type of sensors, their positions and which quantities to measure are supported by a model. A well calibrated model in combination with information extracted from measured data are hence likely to assist in selecting control strategies for optimized drilling performance. In this paper we present a MATLAB based 1D simulation model of a Down The Hole (DTH) drill and compare it with an existing 1D model in terms of computational speed and accuracy. The emphasis is to make a 3D model of a DTH system that is computationally efficient and accurate.

The height and the market share of multi-story timber buildings are both rising. During the last two decades, the Architectural and Engineering Construction industry has developed new reliable solutions to provide strength, structural integrity, fire safety and robustness for timber structures used in the mid- and high-rise sectors.According to long-time survey and lab experiments, motion sickness and sopite syndrome are the main adverse effects on the occupants of a wind sensitive building. For tall timber buildings, wind-induced vibrations seem to be a new critical design aspect at much lower heights than for traditional steel-concrete buildings. To guarantee good comfort, the horizontal accelerations at the top of tall timber buildings must be limited. Two methods in the Eurocode for wind actions (EN1991-1-4), procedure 1 in Annex B (EC-B) and procedure 2 in Annex C (EC-C), provide formulas to estimate the along-wind accelerations. The Swedish code advises to follow a method specified in the National Annex to the Eurocode (EKS) and the American ASCE 7-2016 recommend another method.

This study gives an overview on the background of the different methods for the evaluation of along-wind accelerations for buildings. Estimated accelerations of several tall timber buildings evaluated according to the different methods are compared and discussed. The scatter of the accelerations estimated with different codes is big and increases the design uncertainty of wind induced response at the top of tall timber buildings.

The rise of wood buildings in the skylines of cities forces structural dynamic and timber experts to team up to solve one of the new civil-engineering challenges, namely comfort at the higher levels, in light weight buildings, with respect to wind-induced vibrations. Large laminated timber structures with mechanical joints are exposed to turbulent horizontal excitation with most of the wind energy blowing around the lowest resonance frequencies of 50 to 150 m tall buildings. Good knowledge of the spatial distribution of mass, stiffness and damping is needed to predict and mitigate the sway in lighter, flexible buildings. This paper presents vibration tests and reductions of a detailed FE-model of a truss with dowel-type connections leading to models that will be useful for structural engineers. The models also enable further investigations about the parameters of the slotted-in steel plates and dowels connections governing the dynamical response of timber trusses.

The dynamic response to time varying loads, e.g. wind loads or earthquakes, is inmany cases decisive when designing a tall timber building. The structural parameters governingthe dynamic behaviour are the mass, the damping and the stiffness. The last two parametersare not well-known at serviceability levels for timber structures in general and fortimber connections specifically. Results from forced vibration tests on single components andon a full-scale truss for an eight-storey residential building have been analyzed. In parallel,a detailed Finite Element (FE) model of a large Glulam truss with slotted-in steel plates anddowels connections has been developed and simulations have been made. The damping causedby the structural components, the embedment of fasteners and friction of mating surfaces ofcomponents in the selected connection types is quantified experimentally. The materials’ stiffnessvalues in the model were evaluated. The results from this study bring knowledge on thestructural dynamic properties of large timber structures with mechanical connections and willfacilitate the performance prediction of new tall timber buildings for better comfort at higherlevels in environmentally friendly expansions of our cities.

When designing a tall timber building, the accelerations due to wind loads are in many cases decisive. The parameters governing the dynamic behaviour of the building are the structure’s stiffness, damping and mass together with the loads. The first two parameters are not well-known during the serviceability limit state of timber structures generally and of timber connections specifically.

In this study, dynamical properties of a large glulam truss, a part of the vertical and horizontal structural system in a residential six-storey timber building, are estimated from measurements made in the manufacturing plant. The timber members of the truss are joined with slotted-in steel plates and dowels. Forced vibrational test data are used to extract the dynamical properties. Finite element (FE) models, supported by the experimental results, were developed and simulations, to study the influence of the connection stiffnesses on the total behaviour, were performed. The vibration test results of measurements made on separate structural parts give valuable input to model timber structures and better possibilities to simulate the dynamic behaviour of tall timber buildings as well as the load distribution in wooden structures in the serviceability limit state.

The aim of this study is to compare a new and some existing finite element model error localization methods. The methods are applied to two problems. First, fundamental properties of the error localization methods are studied on a simple sprung mass  system.  In  the second  problem  a  three-bay  frame structure is studied. Here the analytical results of a finite element analysis is taken as substitute for measured data. The model differences between this model and a perturbed model are then found by use of error localization methods.

When data from a known finite element model take place as substitute for test data, the cause of the differences between the data sets are known. A so-called consistent para- meterization, i.e. a parameterization of the quantities known to be in error, is then possible. The error localization method are  compared for both consistent and inconsistent parameterization.

A pre-error localization is made. It is based on the finite element model’s properties. Candidate model parameters, possibly in error, for which the experimental data are not informative,  are  rejected.  Non-identifiable  parameters  are also rejected. Quantification of data information richness and identifiability with newly developed index numbers support the pre-error localization.

Four error localization methods are compared. Two of these are developed by Lallement and Piranda. These are the so- called Balancing of Eigenvalue Equation and Best Subspace Methods. The third is developed by Link and Santiago and is the Substructure Energy Function Method. A new localization method, using gradient and Hessian information of the error criterion function, constitute the fourth method.

Two fundamental questions that arise in finite ele- ment model updating and error localization prob- lems are addressed. These are whether available test data are informative enough with respect to the quantification of possible model errors and whether sufficient identifiability of such errors is at hand for a given test data set. We advocate the use of informativeness and identifiability based indices in a preparatory process to increase the likelihood of a successful error localization. Based on model properties, such informativeness and identifiability indices may be used in the pre-test planning for the determination of frequency, time and spatial resolution to be used in a vibratory test.

First, the test data informativeness with respect to model parameters which might be in error is quan- tified. Here a dual assumption is made such that if model parameter perturbations could be detected by data from the planned test, then the test data could be used to detect such perturbations, i.e. the test is informative. A Data Information Richness (DIR) index has been developed to assess the level od Data Informativeness with respect to model parameters. Secondly, the identifiability of the model parame- ters are studied. The dynamic properties of a struc- ture, as recorded by a measurement system, may under certain conditions change similarly by changing one parameter or a set of other parame

ters. Should that be the case, there is no identifi- ability and before a meaningful error localization may take place, either complementary test data have to be added or a re-parameterization of the model has to be made. To assess the identifiability, identifiability based criteria are further developed, based on earlier work by the authors. A newly developed orthogonality/co-linearity index ocI assist in the re-parameterization of systems with low identifiability.

The methods of preparatory error localisation are applied to a six-degree-of-freedom system in a numerical example in which the analytical results of a finite element analysis are taken as substitute for measured data.

Some years ago, the Society of Experimental Mechanics’ (SEM’s) Technical Division (TD) on Dynamic Substructuring recognized a need for a simpler yet challenging benchmark structure for experimental-numerical substructuring exercises. That structure should replace the modified version of an Ampair 600 wind turbine as the common test object within the TD. Representatives from several research institutes formed a group that defined several desirable properties for the new benchmark structure. The outcome is a frame structure together with a differnt plates. Together, they can represent various structures such as automotive frames, wing-fuselage structures and building floors. The frame is made as a one-piece structure with many 10/32 tapped holes that can be used to attach other components, sensors or excitation devices.Sandia National Labs has manufactured the benchmark structure’s components, an aluminum frame together with two aluminum rectangular wings. An exercise/challenge has been formulated. The components have been shipped to the ones that have shown interest in participating in the exercise. The idea of the exercise is to compare different strategies to tackle an experimental substructuring task, containing both decoupling and coupling, thereby learning from each other.In the exercise, the participants start with an assembly built up by the frame and the thinner of the rectangular wings. That wing should then be numerically decoupled from the fuselage. To that numerical representation of the fuselage, the thicker wing should be coupled numerically. These decoupling and coupling operations render in a numerical representation of the thicker wing attached to the fuselage; a representation which output is compared with test data stemming from the real structure counterpart.Here, virtual points are used in the decoupling and coupling operations. Four attachment points, e.g., four screws, are used. In addition, washers between the fuselage and the wings are used in the connections. The purpose is to avoid too challenging non-linearities to start with. The Component Mode Synthesis (CMS), technique is used.

Substructuring is the topic of the Society of Experimental Mechanics’ Technical Division on Dynamic Substructures. During a number of the most recent IMAC conferences, a lot of studies of coupling and de-coupling of substructures have been presented. In addition, frequency response-, modal- and state-space based techniques for coupling of components represented by numerical or experimental models have been developed. In many such studies, the dynamics of the numerically coupled structures are compared with test data stemming from measurements of the physically assembled counterparts.

An embedded issue when assembling components is the interfacing between the substructures, introducing dry friction in the form of micro slip and varying contact areas. These introduced sources of deviation between the numerically formed assembly and its real world counterpart blend with sources, of deviation, such that test data being incomplete, biased or having random errors.

Here, the initial test object is manufactured as a one piece solid structure. After that, the structure will be cut to form two substructures. Finally, the substructures will be assembled again. Vibrational tests will be made on the solid structure, the substructures as well as on the assembly. The aim is to compare vibrational data and differences in dynamical properties; especially damping, eigenfrequencies and linearity between the solid structures, the numerically formed assembled and the physical re-assembled structure are studied. The purpose of the study is to isolate the causes of possibly deviations by removing the issues stemming from unknown interfaces. Here, the structure together with synthetic modes are presented.

It is important to predict structural phenomena, such as noise and fatigue, stemming from vibra- tions. To do this, reliable structural dynamic models are needed. To be useful the models have to compare well with reality in the validation against test data; if not, the models should be mod- ified. The thesis research is in the field of computational model updating, which is, more often than not, the updating of uncertain parameters of a finite element model to better correlate to test data. This is a specialization that started to grow in the 1970s, and since then much research has been done. The work presented here concerns the design of tests for model updating, which is one of several model updating sub-tasks.

 For a test to be useful for model updating, the test data set must be such that the model param- eters are sufficiently well identifiable. The dynamic properties of a structure to be compared with test data may under certain conditions change similarly when one parameter or a set of other parameters is changed. When this happens, there is lack of identifiability and, before a meaningful model updating can take place, either complementary test data have to be added or a re-parameterization of the model must be made. An index was developed, the Orthogonality- Co-linearity Index (OCI), that helps to find the best way to reduce the number of parameters when there is low identifiability. For the model updating, test data also need to be informative with respect to the parameters to be tuned. The data informativeness depends on the test design, i.e. the choice of stimuli and the placement of the actuators and sensors. A data informativeness index that supports the design of an informative test is proposed. Procedures were also worked out to make the test design robust with respect to parameter uncertainties. The study is limited to linear and time-invariant systems.

During the last years, a lot of research focusing on appropriate interfaces between substructures has been made; the transmission simulator method has become a tool in that strive. In this paper, possible sensitivity, related to ill-conditioning, of the end effects on assembled structures consisting of finite element substructure models representing experimental setups with different levels of transmission simulator mass loadings at their interfaces are studied. Here, components of the Society of Experimental Mechanics, SEM, substructuring focus group's benchmark; the Ampair A600 wind turbine, constitute the structure studied. Models of an A600 blade and bracket system attached to dummy masses of different sizes are coupled to models representing an A600 hub together with two blades attached to dummy masses of different sizes after numerical subtraction of the dummy masses on each of the substructures. The results are compared to data stemming from a model of the assembled system.

The Society of Experimental Mechanics’ (SEM’s) Technical Division (TD) on Dynamic Substructuring recognized a need for a simpler yet challenging benchmark structure for experimental-numerical substructuring exercises. Some years ago, representatives from several research institutes formed a group that defined several desirable properties for the new benchmark structure. The outcome is a frame structure together with different plates. Together, they can represent various structures such as automotive frames, wing-fuselage structures and building floors. The frame is made as a one-piece structure with many 10/32 tapped holes that can be used to attach other components, sensors, or excitation devices.

Sandia National Labs has manufactured the benchmark structure’s components, an aluminum frame together with two rectangular aluminum wings. An exercise/challenge has been formulated. The components have been shipped to the ones that have shown interest in participating in the exercise. The idea of the exercise is to compare different strategies to tackle an experimental substructuring task, containing both decoupling and coupling, thereby learning from each other.

In the exercise, the participants start with an assembly built up by the frame and the thinner of the rectangular wings. That wing should then be numerically decoupled from the fuselage. To that numerical representation of the fuselage, the thicker wing should be coupled numerically. These decoupling and coupling operations render in a numerical representation of the thicker wing attached to the fuselage; a representation which output should be compared with test data stemming from the real structure counterpart.

 The success of the decoupling and coupling exercises are dependent on the quality of the models of the components that are subtracted and added. Here, models of finite element models representing components building up the Technical Division’s Substructuring Benchmark structure are developed. Their convergences are studied, and they are validated by test data stemming from vibration tests of the models’ hardware counterparts.

The aim of this study is to compare a new and some existing finite elementmodel error localization methods. The methods are applied to two problems. First,fundamental properties of the error localization methodsare studied on asimple sprung mass system. Inthe second problem a three-bay frame structure is studied.Here the analytical results of a finite element analysisis taken as substitute for measured  data. The model differences between  thismodel and a perturbed model are then found by use of error localization methods. When data from a known finite element model take place as substitute for test data, the cause of the differences between the data sets are known. A so-calledconsistent para­ meterization, i.e. a parameterization of the quantities known to be in error, is then possible. The error localization methods are compared for both consistent and inconsistent parameterization. A pre-error  localization  is  made. It is based  on  the  finiteelement model's properties. Candidatemodel parameters, possibly in error, for which the experimental data are not informative, are rejected. Non-identifiable parameters are also rejected. Quantification of data information richness and identifiability with newly  developed index numbers support the pre-error localization.

Four error localization methods are compared. Two of these are developed by Lallement and Piranda. These are the so­ called Balancing of Eigenvalue Equation and Best Subspace Methods. The third is developed by Link and Santiago and is the Substructure Energy Function Method. A new localization method, using gradient and Hessian information of the error criterion function, constitute the fourth method.

Within the aerospace industry, linear finite element models are traditionally used to describe the global structural dynamics of an aircraft. Ground vibration test data serve to facilitate the validation of models which are then used to characterize the aeroelastic behavior of the aircraft and to predict the responses due to dynamic loads. Thus, it is vital that the models contain the essential dynamics of the aircraft. Observed nonlinearities are judged to be local in nature whereas the main part of the structure behaves linearly under normal loading. In this work we focus on the identification of nonlinear effects and do that based on model updating theory. That includes methods for error localization with proper selection of candidate error parameters. The nonlinearities are treated as local modeling errors not considered in the linear system model. The error localization behavior is studied using synthetic test data from a simple system, known as the ECL Benchmark, with known nonlinear properties.