Measurements and Prediction of Pedestrian Walking Loads on an Aluminium Catwalk

During the last two decades the topic of human induced vibration has attracted a lot of attention among civil engineering practitioners and academics alike. Usually this type of problem may be encountered in pedestrian footbridges or floors of paperless offices. Slender designs are becoming increasingly popular, and as a consequence, the importance of paying attention to vibration serviceability also increases. This paper resumes the results obtained from measurements taken at different points of an aluminium catwalk which is 6 m in length by 0.6 m in width. Measurements were carried out when subjecting the structure to different actions:1)Static test: a steel cylinder of 35 kg was placed in the middle of the catwalk; 2)Dynamic test: this test consists of exciting the structure with singles impulses; 3)Dynamic test: people walking on the catwalk. Identification of the mechanical properties of the structure is an achievement of the paper. Indirect methods were used to estimate properties including the support stiffness, the beam bending stiffness, the mass of the structure (using Rayleigh method and iterative matrix method), the natural frequency (using the time domain and frequency domain analysis) and the damping ratio (by calculating the logarithmic decrement). Experimental results and numerical predictions for the response of an aluminium catwalk subjected to walking loads have been compared. The damping of this light weight structure depends on the amplitude of vibration which complicates the tuning of a structural model. In the light of the results obtained it seems that the used walking load model is not appropriate as the predicted transient vibration values (TTVs) are much higher than the measured ones.

Acciones humanas sobre estructuras

En esta tesis se propone un nuevo modelo de carga para caracterizar los saltos de personas sobre estructuras y se estudia la influencia de las personas en las propiedades dinámicas de la estructura. En el estudio del comportamiento estructural de construcciones como gimnasios, salas de baile, estadios, auditorios o pasarelas peatonales sometidas a cargas producidas por un gran número de personas, se deben tener en cuenta las fuerzas dinámicas, lo cual implica el uso de modelos de cálculo más complejos y criterios de dimensionamiento con nuevos parámetros. Por ello, es necesario determinar a qué cargas van a estar sometidas este tipo de estructuras y cómo van a cambiar cuando se encuentren ocupadas por personas. En la primera parte del trabajo se presenta el problema de considerar las fuerzas dinámicas en el análisis de estructuras. Se indican los factores que influyeron en el interés por este tipo de estudios. Se exponen los objetivos de la tesis y se propone la metodología para conseguirlos. También en esta primera parte se describe el estado del arte. Se explican los modelos existentes de carga generada por saltos de personas y se hace un repaso de los principales autores y estudios sobre este tema. Por último se exponen algunas ideas sobre las modificaciones dinámicas que provoca la presencia de las personas en las estructuras. En la segunda parte de la tesis se explica el modelo de carga de saltos propuesta en este trabajo, donde se incluye una campaña de ensayos con saltos sobre una placa de carga. Se describen las estructuras de ensayo, un gimnasio y una losa que cubre un aljibe. Se detalla la identificación de las propiedades dinámicas de las estructuras, describiendo los ensayos correspondientes y los resultados de un Análisis Operacional Modal. Por último se presenta el modelo de elementos finitos de la estructura elegida para los ensayos. En la tercera y última parte del trabajo se comprueba la validez de los modelos de carga estudiados mediante la realización de ensayos dinámicos con personas saltando y la posterior comparación de los resultados experimentales con las simulaciones numéricas. Como último resultado se estudia la influencia de las personas en las propiedades dinámicas de la estructura. Para ello se utilizan los datos obtenidos mediante un ensayo con personas pasivas. ABSTRACT In this thesis, a new load model is proposed to characterize people jumping on structures and the influence of people in the dynamic properties of the structure is studied. In the study of the structural behavior of buildings such as gymnasiums, dance halls, stadiums, auditoriums or footbridges subjected to loads generated by crowd, dynamic forces must take into account, which involves the use of more complex calculation models and dimensioning criteria with new parameters. Therefore, it is necessary to determine these dynamic loads and how structures will change when they are occupied by people. In the first part of the work the problem of considering the dynamic forces in the analysis of structures is presented. The factors that influence on the interest in this type of study are indicated. The objectives of the thesis are presented and also the proposed methodology in order to achieve them. In this first part the state of the art is described. Existing jumping load models are explained and a review of the main authors and studies on this subject is done. Finally some ideas about the dynamic changes caused by the presence of people in the structures are exposed. In the second part of the thesis the proposed jumping load model is explained, including jump tests on a force plate. Test structures, a gym and a concrete slab are described. Dynamic properties identification of the test structures is detailed with the corresponding tests and Operational Modal Analysis results. Finally, a finite element model of the structure chosen for the tests is presented. In the third part of the work, the studied jump load models are validated by performing dynamic testing with people jumping and the subsequent comparison of experimental results with numerical simulations. As a last result, the influence of people on the dynamic properties of the structure is checked. For this purpose, obtained data from a test with passive people are used.

Comparison of dynamic effects of high-speed traffic load on ballasted track using a simplified two-dimensional and full three-dimensional model.

The vertical dynamic actions transmitted by railway vehicles to the ballasted track infrastructure is evaluated taking into account models with different degree of detail. In particular, we have studied this matter from a two-dimensional (2D) finite element model to a fully coupled three-dimensional (3D) multi-body finite element model. The vehicle and track are coupled via a non-linear Hertz contact mechanism. The method of Lagrange multipliers is used for the contact constraint enforcement between wheel and rail. Distributed elevation irregularities are generated based on power spectral density (PSD) distributions which are taken into account for the interaction. The numerical simulations are performed in the time domain, using a direct integration method for solving the transient problem due to the contact nonlinearities. The results obtained include contact forces, forces transmitted to the infrastructure (sleeper) by railpads and envelopes of relevant results for several track irregularities and speed ranges. The main contribution of this work is to identify and discuss coincidences and differences between discrete 2D models and continuum 3D models, as wheel as assessing the validity of evaluating the dynamic loading on the track with simplified 2D models

Loss model for a high frequency and low load DC/DC synchronous buck converter

This work presents a behavioral-analytical hybrid loss model for a buck converter. The model has been designed for a wide operating frequency range up to 4MHz and a low power range (below 20W). It is focused on the switching losses obtained in the power MOSFETs. Main advantages of the model are the fast calculation time and a good accuracy. It has been validated by simulation and experimentally with one Ga, power transistor and two Si MOSFETs. Results show good agreement between measurements and the model.

Hybrid behavioral-analytical loss model for a high frequency and low load DC/DC buck converter

This work presents a behavioral-analytical hybrid loss model for a buck converter. The model has been designed for a wide operating frequency range up to 4MHz and a low power range (below 20W). It is focused on the switching losses obtained in the power MOSFETs. Main advantages of the model are the fast calculation time (below 8.5 seconds) and a good accuracy, which makes this model suitable for the optimization process of the losses in the design of a converter. It has been validated by simulation and experimentally with one GaN power transistor and three Si MOSFETs. Results show good agreement between measurements and the model

Fisuración y deformaciones en tabiquerías

A diferencia de otros parámetros, el efecto de la existencia de huecos en la aparición y desarrollo de los procesos de fisuración en los paños de fábrica no ha sido considerado por las distintas normativas existentes en la actualidad. En nuestros días se emplea una variada gama de tipologías de elementos de cerramiento para realizar las particiones en las obras de edificación, cada una de ellas con características mecánicas diferentes y distinta metodología de ejecución, siendo de aplicación la misma normativa relativa al cálculo y control de las deformaciones. Tal y como expresamos en el Capitulo 1, en el que se analiza el Estado del Conocimiento, los códigos actuales determinan de forma analítica la flecha probable que se alcanza en los elementos portantes estructurales bajo diferentes condiciones de servicio. Las distintas propuestas que existen respecto para la limitación de la flecha activa, una vez realizado el cálculo de las deformaciones, bien por el método de Branson ó mediante los métodos de integración de curvaturas, no contemplan como parámetro a considerar en la limitación de la flecha activa la existencia y tipología de huecos en un paño de fábrica soportado por la estructura. Sin embargo se intuye y podríamos afirmar que una discontinuidad en cualquier elemento sometido a esfuerzos tiene influencia en el estado tensional del mismo. Si consideramos que, de forma general, los procesos de fisuración se producen al superarse la resistencia a tracción de material constitutivo de la fábrica soportada, es claro que la variación tensional inducida por la existencia de huecos ha de tener cierta influencia en la aparición y desarrollo de los procesos de fisuración en los elementos de partición o de cerramiento de las obras de edificación. En los Capítulos 2 y 3 tras justificar la necesidad de realizar una investigación encaminada a confirmar la relación entre la existencia de huecos en un paño de fábrica y el desarrollo de procesos de fisuración en el mismo, se establece este aspecto como principal Objetivo y se expone la Metodología para su análisis. Hemos definido y justificado en el Capítulo 4 el modelo de cálculo que hemos utilizado para determinar las deformaciones y los procesos de fisuración que se producen en los casos a analizar, en los que se han considerado como variables: los valores de la luz del modelo, el estado de fisuración de los elementos portantes, los efectos de la fluencia y el porcentaje de transmisión de cargas desde el forjado superior al paño de fábrica en estudio. Además se adoptan dos valores de la resistencia a tracción de las fábricas, 0.75MPa y 1.00MPa. La capacidad de representar la fisuración, así como la robustez y fiabilidad ha condicionado y justificado la selección del programa de elementos finitos que se ha utilizado para realizar los cálculos. Aprovechando la posibilidad de reproducir de forma ajustada las características introducidas para cada parámetro, hemos planteado y realizado un análisis paramétricos que considera 360 cálculos iterativos, de cuya exposición es objeto el Capítulo 5, para obtener una serie representativa de resultados sobre los que se realizará el análisis posterior. En el Capítulo 6, de análisis de los resultados, hemos estudiado los valores de deformaciones y estados de fisuración obtenidos para los casos analizados. Hemos determinado la influencia que tiene la presencia de huecos en la aparición de los procesos de fisuración y en las deformaciones que se producen en las diferentes configuraciones estructurales. Las conclusiones que hemos obtenido tras analizar los resultados, incluidas en el Capítulo 7, no dejan lugar a dudas: la presencia, la posición y la tipología de los huecos en los elementos de fábricas soportadas sobre estructuras deformables son factores determinantes respecto de la fisuración y pueden tener influencia en las deformaciones que constituyen la flecha activa del elemento, lo que obliga a plantear una serie de recomendaciones frente al proyecto y frente a la reglamentación técnica. La investigación desarrollada para esta Tesis Doctoral y la metodología aplicada para su desarrollo abre nuevas líneas de estudio, que se esbozan en el Capítulo 8, para el análisis de otros aspectos que no han sido cubiertos por esta investigación a fin de mejorar las limitaciones que deberían establecerse para los Estados Límite de Servicio de Deformaciones correspondientes a las estructuras de edificación. SUMMARY. Unlike other parameters, the effect of the existence of voids in the arising and development of cracking processes in the masonry walls has not been considered by current Codes. Nowadays, a huge variety of enclosure elements types is used to execute partitions in buildings, each one with different mechanical characteristics and different execution methodology, being applied the same rules concerning deflection calculation and control. As indicated in Chapter 1, which analyzes the State of Art, current codes analytically determine the deflection likely to be achieved in structural supporting elements under different service conditions. The different proposals that exist related to live deflection limitation, once performed deformations calculation, either by Branson´s method or considering curvatures integration methods, do not consider in deflection limitation the existence and typology of voids in a masonry wall structured supported. But is sensed and it can be affirmed that a discontinuity in any element under stress influences the stress state of it. If we consider that, in general, cracking processes occur when masonry material tensile strength is exceeded, it is clear that tension variation induced by the existence of voids must have some influence on the emergence and development of cracking processes in enclosure elements of building works. In Chapters 2 and 3, after justifying the need for an investigation to confirm the relationship between the existence of voids in a masonry wall and the development of cracking process in it, is set as the main objective and it is shown the analysis Methodology. We have defined and justified in Chapter 4 the calculation model used to determine the deformation and cracking processes that occur in the cases analyzed, in which were considered as variables: model span values, bearing elements cracking state, creep effects and load transmission percentage from the upper floor to the studied masonry wall. In addition, two masonry tensile strength values 0.75MPa and 1.00MPa have been considered. The cracking consideration ability, robustness and reliability has determined and justified the selection of the finite element program that was used for the calculations. Taking advantage of the ability of accurately consider the characteristics introduced for each parameter, we have performed a parametric analyses that considers 360 iterative calculations, whose results are included in Chapter 5, in order to obtain a representative results set that will be analyzed later. In Chapter 6, results analysis, we studied the obtained values of deformation and cracking configurations for the cases analyzed. We determined the influence of the voids presence in the occurrence of cracking processes and deformations in different structural configurations. The conclusions we have obtained after analyzing the results, included in Chapter 7, leave no doubt: the presence, position and type of holes in masonry elements supported on deformable structures are determinative of cracking and can influence deformations which are the element live deflection, making necessary to raise a number of recommendations related to project and technical regulation. The research undertaken for this Doctoral Thesis and the applied methodology for its development opens up new lines of study, outlined in Chapter 8, for the analysis of other aspects that are not covered by this research, in order to improve the limitations that should be established for Deflections Serviceability Limit States related to building structures.

Prediction of bendig load capacity of timber beams by finite element method simulation of knots and grain deviation

A finite element model was used to simulate timberbeams with defects and predict their maximum load in bending. Taking into account the elastoplastic constitutive law of timber, the prediction of fracture load gives information about the mechanisms of timber failure, particularly with regard to the influence of knots, and their local graindeviation, on the fracture. A finite element model was constructed using the ANSYS element Plane42 in a plane stress 2D-analysis, which equates thickness to the width of the section to create a mesh which is as uniform as possible. Three sub-models reproduced the bending test according to UNE EN 408: i) timber with holes caused by knots; ii) timber with adherent knots which have structural continuity with the rest of the beam material; iii) timber with knots but with only partial contact between knot and beam which was artificially simulated by means of contact springs between the two materials. The model was validated using ten 45 × 145 × 3000 mm beams of Pinus sylvestris L. which presented knots and graindeviation. The fracture stress data obtained was compared with the results of numerical simulations, resulting in an adjustment error less of than 9.7%

Approximate Analytical Model for the Squeeze-Film Lubrication of the Human Ankle Joint with Synovial Fluid Filtrated by Articular Cartilage

The aim of this article is to propose an analytical approximate squeeze-film lubrication model of the human ankle joint for a quick assessment of the synovial pressure field and the load carrying due to the squeeze motion. The model starts from the theory of boosted lubrication for the human articular joints lubrication (Walker et al., Rheum Dis 27:512–520, 1968; Maroudas, Lubrication and wear in joints. Sector, London, 1969) and takes into account the fluid transport across the articular cartilage using Darcy’s equation to depict the synovial fluid motion through a porous cartilage matrix. The human ankle joint is assumed to be cylindrical enabling motion in the sagittal plane only. The proposed model is based on a modified Reynolds equation; its integration allows to obtain a quick assessment on the synovial pressure field showing a good agreement with those obtained numerically (Hlavacek, J Biomech 33:1415–1422, 2000). The analytical integration allows the closed form description of the synovial fluid film force and the calculation of the unsteady gap thickness.

Some past decision theory models for euro construction model codes and for road drainage in Spain, and modest hints with multi-criteria methods for agro and environmental assurance

The authors are from UPM and are relatively grouped, and all have intervened in different academic or real cases on the subject, at different times as being of different age. With precedent from E. Torroja and A. Páez in Madrid Spain Safety Probabilistic models for concrete about 1957, now in ICOSSAR conferences, author J.M. Antón involved since autumn 1967 for euro-steel construction in CECM produced a math model for independent load superposition reductions, and using it a load coefficient pattern for codes in Rome Feb. 1969, practically adopted for European constructions, giving in JCSS Lisbon Feb. 1974 suggestion of union for concrete-steel-al.. That model uses model for loads like Gumbel type I, for 50 years for one type of load, reduced to 1 year to be added to other independent loads, the sum set in Gumbel theories to 50 years return period, there are parallel models. A complete reliability system was produced, including non linear effects as from buckling, phenomena considered somehow in actual Construction Eurocodes produced from Model Codes. The system was considered by author in CEB in presence of Hydraulic effects from rivers, floods, sea, in reference with actual practice. When redacting a Road Drainage Norm in MOPU Spain an optimization model was realized by authors giving a way to determine the figure of Return Period, 10 to 50 years, for the cases of hydraulic flows to be considered in road drainage. Satisfactory examples were a stream in SE of Spain with Gumbel Type I model and a paper of Ven Te Chow with Mississippi in Keokuk using Gumbel type II, and the model can be modernized with more varied extreme laws. In fact in the MOPU drainage norm the redacting commission acted also as expert to set a table of return periods for elements of road drainage, in fact as a multi-criteria complex decision system. These precedent ideas were used e.g. in wide Codes, indicated in symposia or meetings, but not published in journals in English, and a condensate of contributions of authors is presented. The authors are somehow involved in optimization for hydraulic and agro planning, and give modest hints of intended applications in presence of agro and environment planning as a selection of the criteria and utility functions involved in bayesian, multi-criteria or mixed decision systems. Modest consideration is made of changing in climate, and on the production and commercial systems, and on others as social and financial.

Coupled model of initiation and propagation of corrosion in reinforced concrete

Corrosion of reinforcing steel in concrete due to chloride ingress is one of the main causes of the deterioration of reinforced concrete structures. Structures most affected by such a corrosion are marine zone buildings and structures exposed to de-icing salts like highways and bridges. Such process is accompanied by an increase in volume of the corrosión products on the rebarsconcrete interface. Depending on the level of oxidation, iron can expand as much as six times its original volume. This increase in volume exerts tensile stresses in the surrounding concrete which result in cracking and spalling of the concrete cover if the concrete tensile strength is exceeded. The mechanism by which steel embedded in concrete corrodes in presence of chloride is the local breakdown of the passive layer formed in the highly alkaline condition of the concrete. It is assumed that corrosion initiates when a critical chloride content reaches the rebar surface. The mathematical formulation idealized the corrosion sequence as a two-stage process: an initiation stage, during which chloride ions penetrate to the reinforcing steel surface and depassivate it, and a propagation stage, in which active corrosion takes place until cracking of the concrete cover has occurred. The aim of this research is to develop computer tools to evaluate the duration of the service life of reinforced concrete structures, considering both the initiation and propagation periods. Such tools must offer a friendly interface to facilitate its use by the researchers even though their background is not in numerical simulation. For the evaluation of the initiation period different tools have been developed: Program TavProbabilidade: provides means to carry out a probability analysis of a chloride ingress model. Such a tool is necessary due to the lack of data and general uncertainties associated with the phenomenon of the chloride diffusion. It differs from the deterministic approach because it computes not just a chloride profile at a certain age, but a range of chloride profiles for each probability or occurrence. Program TavProbabilidade_Fiabilidade: carries out reliability analyses of the initiation period. It takes into account the critical value of the chloride concentration on the steel that causes breakdown of the passive layer and the beginning of the propagation stage. It differs from the deterministic analysis in that it does not predict if the corrosion is going to begin or not, but to quantifies the probability of corrosion initiation. Program TavDif_1D: was created to do a one dimension deterministic analysis of the chloride diffusion process by the finite element method (FEM) which numerically solves Fick’second Law. Despite of the different FEM solver already developed in one dimension, the decision to create a new code (TavDif_1D) was taken because of the need to have a solver with friendly interface for pre- and post-process according to the need of IETCC. An innovative tool was also developed with a systematic method devised to compare the ability of the different 1D models to predict the actual evolution of chloride ingress based on experimental measurements, and also to quantify the degree of agreement of the models with each others. For the evaluation of the entire service life of the structure: a computer program has been developed using finite elements method to do the coupling of both service life periods: initiation and propagation. The program for 2D (TavDif_2D) allows the complementary use of two external programs in a unique friendly interface: • GMSH - an finite element mesh generator and post-processing viewer • OOFEM – a finite element solver. This program (TavDif_2D) is responsible to decide in each time step when and where to start applying the boundary conditions of fracture mechanics module in function of the amount of chloride concentration and corrosion parameters (Icorr, etc). This program is also responsible to verify the presence and the degree of fracture in each element to send the Information of diffusion coefficient variation with the crack width. • GMSH - an finite element mesh generator and post-processing viewer • OOFEM – a finite element solver. The advantages of the FEM with the interface provided by the tool are: • the flexibility to input the data such as material property and boundary conditions as time dependent function. • the flexibility to predict the chloride concentration profile for different geometries. • the possibility to couple chloride diffusion (initiation stage) with chemical and mechanical behavior (propagation stage). The OOFEM code had to be modified to accept temperature, humidity and the time dependent values for the material properties, which is necessary to adequately describe the environmental variations. A 3-D simulation has been performed to simulate the behavior of the beam on both, action of the external load and the internal load caused by the corrosion products, using elements of imbedded fracture in order to plot the curve of the deflection of the central region of the beam versus the external load to compare with the experimental data.

Dynamic response of hydro power plants to load variations for providing secondary regulation reserves considering elastic water column effects

In this paper, the dynamic response of a hydro power plant for providing secondary regulation reserve is studied in detail. S pecial emphasis is given to the elastic water column effects both in the penstock and the tailrace tunnel. For this purpose, a nonline ar model based on the analogy between mass and momentum conservation equations of a water conduit and those of wave propagation in transmission lines is used. The influence of the plant configuration and design parameters on the fulfilment of the Spanish Electrical System Operator requirem ents is analysed.

Business model with discount incentive in a P2P-cloud multimedia streaming system

Today P2P faces two important challenges: design of mechanisms to encourage users' collaboration in multimedia live streaming services; design of reliable algorithms with QoS provision, to encourage the multimedia providers employ the P2P topology in commercial live streaming systems. We believe that these two challenges are tightly-related and there is much to be done with respect. This paper analyzes the effect of user behavior in a multi-tree P2P overlay and describes a business model based on monetary discount as incentive in a P2P-Cloud multimedia streaming system. We believe a discount model can boost up users' cooperation and loyalty and enhance the overall system integrity and performance. Moreover the model bounds the constraints for a provider's revenue and cost if the P2P system is leveraged on a cloud infrastructure. Our case study shows that a streaming system provider can establish or adapt his business model by applying the described bounds to achieve a good discount-revenue trade-off and promote the system to the users.

A multi-resource load balancing algorithm for cloud cache systems

With the advent of cloud computing model, distributed caches have become the cornerstone for building scalable applications. Popular systems like Facebook [1] or Twitter use Memcached [5], a highly scalable distributed object cache, to speed up applications by avoiding database accesses. Distributed object caches assign objects to cache instances based on a hashing function, and objects are not moved from a cache instance to another unless more instances are added to the cache and objects are redistributed. This may lead to situations where some cache instances are overloaded when some of the objects they store are frequently accessed, while other cache instances are less frequently used. In this paper we propose a multi-resource load balancing algorithm for distributed cache systems. The algorithm aims at balancing both CPU and Memory resources among cache instances by redistributing stored data. Considering the possible conflict of balancing multiple resources at the same time, we give CPU and Memory resources weighted priorities based on the runtime load distributions. A scarcer resource is given a higher weight than a less scarce resource when load balancing. The system imbalance degree is evaluated based on monitoring information, and the utility load of a node, a unit for resource consumption. Besides, since continuous rebalance of the system may affect the QoS of applications utilizing the cache system, our data selection policy ensures that each data migration minimizes the system imbalance degree and hence, the total reconfiguration cost can be minimized. An extensive simulation is conducted to compare our policy with other policies. Our policy shows a significant improvement in time efficiency and decrease in reconfiguration cost.

Nationwide impact and vehicle to grid application of electric vehicles mobility using an activity based model

This paper describes the impact of electric mobility on the transmission grid in Flanders region (Belgium), using a micro-simulation activity based models. These models are used to provide temporal and spatial estimation of energy and power demanded by electric vehicles (EVs) in different mobility zones. The increment in the load demand due to electric mobility is added to the background load demand in these mobility areas and the effects over the transmission substations are analyzed. From this information, the total storage capacity per zone is evaluated and some strategies for EV aggregator are proposed, allowing the aggregator to fulfill bids on the electricity markets.

A review of load models for the prediction of footfall-induced vibration in structures

Crowd induced dynamic loading in large structures, such as gymnasiums or stadium, is usually modelled as a series of harmonic loads which are defined in terms of their Fourier coefficients. Different values of these coefficients that were obtained from full scale measurements can be found in codes. Recently, an alternative has been proposed, based on random generation of load time histories that take into account phase lag among individuals inside the crowd. This paper presents the testing done on a structure designed to be a gymnasium. Two series of dynamic test were performed on the gym slab. For the first test an electrodynamic shaker was placed at several locations and during the second one people located inside a marked area bounced and jumped guided by different metronome rates. A finite element model (FEM) is presented and a comparison of numerically predicted and experimentally observed vibration modes and frequencies has been used to assess its validity. The second group of measurements will be compared with predictions made using the FEM model and three alternatives for crowd induced load modelling.