Machine Foundations Research Articles

Analysis and dynamic behavior of portal structures due to reciprocating machine

reciprocating engine consists of two driving parts, piston and rotor, when the engine start these two parts move with a certain frequency, resulting in vibrations in the structure. dynamic analysis of the structure aim to find out how the structure behaves due to vibrations generated from the machine, whether the structure is safe for the machine and humans around the machine due to the amplitude of displacement, velocity, and displacement from structure. This dynamic analysis is carried out with the help of SAP 2000 v20.20 software with a dynamic load in the form of a reciprocating compressor operating with a frequency of 49.16 Hz. In this final project, the machine foundation uses a table top type with 1x1.7 m column dimensions and 1.3x1.6 m beams. From the free vibration analysis, the result is a natural frequency structure, from the first ten modes the structure is declared safe from resonance However, in this study the displacement and velocity of structures that occur in the zone B & C while the acceleration into the safe category based on applicable standards. This means that the structure is safe for humans who are around but are not safe for the product and the machine itself if it operates for a long time continuously.

Investigation of the behavior of shallow machine foundation resting on a saturated layered sandy soil subjected to a dynamic load

In liquefying soils, Shallow foundations may experience an increase in settlement and displacement due to dynamic loading. Therefore, the machine footing may settle and tilt excessively. In this paper, the settlement of shallow foundation and inner displacement on liquefiable of unreinforced and reinforced saturated multi-layered sandy soils (medium-dense sand MD) will be studied. The relative density of the first and second layers is 50% and 85% corresponding to medium sand soil and dense sand soil respectively. The tests have been carried out on 20 models. The amplitudes of the applied harmonic load are 0.25, 1 and 2 tons with frequencies of 0.5, 1 and 2 Hz. The used foundation was with dimension 200*200*20 mm and the geogrid was used as reinforcement material. For each amplitude and frequency of load, the sand models were tested without and with reinforcement in various configurations (0.5B, 1B using single reinforcement layer and 0.5B, 1B using double reinforcement layers) where B is the square footing width. The results showed the high susceptibility for liquefaction and its potential which increased with increasing amplitude load and amplitude frequency. Also, the surface settlement and displacement were increased in the first layer and reduced with increasing relative density. The results also showed the high effect of reinforcement material and its configuration and number of layers by maintaining the little settlement values when fixing other parameters.

Numerical Analysis of the Interference of Two Active Machine Foundations

This study examines the influence of the interference on the dynamic response of two active machine foundations using the finite element analysis. The finite element model has been built carefully to ensure that the finite element model extend, and the mesh size do not influence the obtained results. Furthermore, the methodology of the finite element analysis has been verified using well-known and robust analytical solutions of wave propagation and machine vibration. Loose sand, medium sand, and dense sand and a vibration frequency range of 0.5–20.0 Hz have been considered in the analyses. The results showed that the interference of two active machine foundations remarkably increases the dynamic settlement with a percentage increase range from 1 to 77%. This percentage increase declines as the frequency of vibration or the distance between the foundations increases and rises as the soil stiffness increases. It was also found that the critical distance after which the interference effect terminates depends on the frequency of vibration and the stiffness of the soil, where the critical distance increases as the frequency of vibration declines or as the stiffness of the soil increases. Finally, a methodology has been proposed based on the results of the analyses to implicate the effect of interference in the calculation of the dynamic settlement.

Response of Different Machine Foundation Shapes Resting on Dry Sand to Dynamic Loading

In this paper, the effect of footing shape resting on dry sand when subjected to machine dynamic loading is experimentally investigated. A laboratory set-up was prepared to simulate the case at different operating frequencies. Nine models were tested to examine the effects of the combinations of two parameters, including different frequencies of (0.5, 1, and 2 Hz) and different footing shapes (circular, square and rectangular). The tests were conducted under a load amplitude of (0.25 ton) using sand with medium and dense relative densities corresponding to (R.D. = 50% and 80%) having unit weights of (17.04 and 17.96 kN/m3) respectively. A shaft encoder and a vibration meter were used to measure the strain and amplitude displacement, while the stress in the soil at different depths was measured using flexible pressure sensors. It was found that the shape of footing has a considerable influence on the bearing capacity of the supporting soil under dynamic loading. For instance, the strain of dry sand under a circular footing was nearly (41%) higher, the amplitude displacement was nearly (17%) higher, and stress was nearly (12%) higher than square and rectangular footings, under the same conditions.

Chemical-Bonded Anchor Bolts versus Traditional J and T Anchor Bolts Used in Machine Foundations

AbstractHeavy machinery that undergoes significant impact in its lifetime requires support and a system that can resist dynamic forces and the resulting vibrations. In this context, this technical ...

Practical Design and Construction of Machine Foundations Subjected to Impact Loads

AbstractThis case study considers a construction site with weak soil (clayey and silty sands) that has a coefficient of elastic uniform compression Cu less than 3 kN/m3 (19.27 lb/ft3). Instead of...

Effect of mode of vibration on the response of machine foundation on sand

In this paper, the influence of the following parameters on different modes of vibration response of model footings on sand is studied: (vertical, rocking and pitching load amplitude and frequency). To achieve the objective of this study, the model footing was selected to be rectangular footing with an aspect ratio (L/B= 1.33) i.e (L= length and B= width). A physical model was manufactured to simulate a steady-state harmonic dynamic load applied at different operating frequencies with the same load amplitude (0.5 ton). A total of (9) cases was performed taking into account different parameters. The loading frequency ranged from (0.5) to (2) Hz and the footing was rectangular with an aspect ratio (L/B = 1.33). The soil type used was dry sand having a relative density of (50%). The behavior of the soil underneath the footing was examined by measuring the strain using a shaft encoder and the amplitude of displacement using a vibration meter. It was found that the change in vibration mode made little effect of the final strain values under the same frequency and the amplitude of displacement in (Z) direction, while the amplitude of displacement in (Y) is higher, occuring under rocking vibration and higher value amplitude of displacement in (X) direction under pitching vibration under the same frequency.

Dynamic response and design of a skirted strip foundation subjected to vertical vibration

Numerous studies have repeatedly demonstrated the efficiency of using skirts to increase the bearing capacity and to reduce settlement of shallow foundations subjected to static loads. However, no efforts have been made to study the efficiency of using these skirts to reduce settlement produced by machine vibration, although machines are very sensitive to settlement and the foundations of these machines should be designed properly to ensure that the settlement produced due to machine vibration is very small. This research has been conducted to investigate the efficiency of using skirts as a technique to reduce the settlement of a strip foundation subjected to machine vibration. A two-dimensional finite element model has been developed, validated, and employed to achieve the aim of the study. The results of the analyses showed that the use of skirts reduces the settlement produced due to machine vibration. However, the percentage decrease of the settlement is remarkably influenced by the density of the soil and the frequency of vibration, where it rises as the frequency of vibration increases and declines as the soil density rises. It was also found that increasing skirt length increases the percentage decrease of the settlement. Importantly, the results obtained from the analyses have been utilized to derive new dynamic impedance values that implicitly consider the presence of skirts. Finally, novel design equations of dynamic impedance that implicitly account to the effect of the skirts have been derived and validated utilizing a new intelligent data driven method. These new equations can be used in future designs of skirted strip foundations subjected to machine vibration.

Experimental Investigations on the Temperature Increase of Ultra-High Performance Concrete under Fatigue Loading

Leaner, more filigree, and resource-saving constructions are the development goal of the in the building industry. In reinforced concrete construction, a ultra-high strength concrete was developed to achieve these goals. Due to its use and requirements, this very pressure-resistant material is no longer only exposed to static loads. In applications such as wide-span bridges, machine foundations and wind turbines, the susceptibility to vibration is also significant. Research into the fatigue behavior of the new building material is therefore very important. In this article we will discuss the effect of heating up of high performance concretes under fatigue stress. The thesis is that warming up, which was already observed by several research groups, has an influence on the fatigue strength. Changes in the strength of the concrete or residual stresses generated by heating can lead to early failure. The aim is to find the reasons for the heating and the grade of influence on the fatigue strength. A systematic test program was developed to investigate the influencing parameters maximum stress level, frequency, and maximum grain size of the concrete. Thirty fatigue tests were carried out; the results will be presented here. The influence on the temperature increase as well as on the heating rate for the individual parameters will be discussed. The results show that all three discussed parameters have a significant influence on the temperature rise. Whereas the maximum temperature reached depends strongly on the frequency, the other two parameters mainly influence the heating rate.

Experimental Results Of A Self-Learning Compensation System For High Precision Manufacturing

This paper presents the experimental results obtained by applying the results of some recently concluded European projects, whose objective was the development and validation of hardware and control systems for production, based on understanding, evaluating and controlling the performance of a machine tool. It is based on a self-learning controller capable of managing a large quantity of data acquired by sensor systems, as well as on-board artifacts and finished work piece measurements that, associated to operating conditions, permit the accumulation of knowledge regarding the behaviour of machines. Relying on this experience-based approach, the controller can predict the errors that a machining process will present under different conditions and can thus adapt compensation tables. The approach set out has been implemented in a demonstrator consisting of a 5-axis high-precision boring machine, fully functional in an industrial shop floor but used under controlled environmental conditions (thermostatic chamber and special machine foundations). Its software system supports measurement procedures and is able to integrate data acquisition from different sensor systems, to calculate the volumetric error with 3D representations, to provide models for calculation of error functions and to integrate communication processes with the CNC. It can therefore operate in actual production sites, introducing relevant improvements in the machine tools manufacturing field. This paper presents the experimental results obtained during the project validation, including a comparison between on field measurements and compensation tables calculated on the basis of the predictions of the self-learning system. The analysis of the data gathered highlights the system's capability to deal with both simple linear dependencies (e.g. between error and mass variation) and complex, non-linear but repeatable trends. Results discussion, relating to two different and independent axis, demonstrates the applicability of the system under real operating conditions.

Radiation damping for rigid foundations. Approximate expressions

The dynamic response of machine foundations was one of the first problems studied in soil dynamics with results going back to the 1930s. A number of approximations and graphical results were proposed in the 60s. In this paper we present a series of approximate expressions for the natural frequencies and effective damping of rigid masses on the surface of an elastic half space subjected to both vertical and coupled horizontal-rocking harmonic excitations. The formulas are obtained using the approximate expressions for the dynamic stiffness of circular foundations suggested by Veletsos et al [1, 2] for two different values of Poisson’s ratio of the soil. For the vertical case the expressions are only a function of the mass ratio (ratio of the mass of the foundation to an effective mass of soil) and of Poisson’s ratio. For the horizontal-rocking case they depend also on the ratio of the height of the foundation to its equivalent radius (a slenderness ratio).

Assessment of Failure Occurrence Rate for Concrete Machine Foundations Used in Gas and Oil Industry by Machine Learning

Concrete machine foundations are structures that transfer loads from machines in operation to the ground. The design of such foundations requires a careful analysis of the static and dynamic effects caused by machine exploitation. There are also other substantial differences between ordinary concrete foundations and machine foundations, of which the main one is that machine foundations are separated from the building structure. Appropriate quality and the preservation of operational parameters of machine foundations are essential, especially in the gas and oil industry, where every disruption in the technological process is costly. First and foremost, there are direct repair costs from damage to foundations, but there are also indirect costs associated with blockages of the production process. Foundation repairs can temporarily shut down a given part of the refining process from operation. Thanks to cooperation from our partner, we obtained data from 510 concrete machine foundations from a refinery. Our database included many parameters, such as concrete cover thickness, machine gravity center distortion, the angular frequency of vertical self-excited vibrations, the angular frequency of horizontal self-excited vibrations, amplitudes of oscillation, foundation area, foundation volume, and information on occurring failures. Concrete machine foundation failure is not yet fully understood. In our study, we assessed what affects the failure occurrence rate of concrete machine foundations and to what extent. We wanted to find out whether there are correlations between the foundation failure occurrence rate and the mentioned parameters. To achieve this goal, we utilized state-of-the-art machine learning techniques.

New findings in the research of concrete fatigue

An increasing use of high-performance concretes—accompanied by an increasing slenderness of structures—will require a specific fatigue design more often. This holds true especially for structures having to resist very high numbers of load cycles throughout their operating service life. Generally, these are long spanning, slender bridge structures, structures for wind energy turbines or machine foundations. For standard structures—and most common bridges—the fatigue resistance of concrete does not become decisive in design. Before the introduction of Eurocode 2 and CEB/FIP Model Code 1990—with design concepts based on Wöhler-curves—research regarding concrete fatigue was rare and often focused on counting the bearable number of cycles until failure. However, knowledge at time on the gradual deterioration phenomena, which finally results in a fatigue failure, was hardly available. In the time since, design rules were cautiously corrected, for example, in fib Model Code 2010, but, knowledge on the mechanisms of fatigue deterioration is still very limited. With the development of concretes with higher compressive strengths, more slender structures have become possible, in which the ratio of the dead load to the variable loads, relevant for fatigue, has substantially decreased. These concretes often show compressive strengths exceeding 100 MPa, outstanding workability, small maximum grain sizes and additionally contain fiber reinforcement. These concretes are hardly comparable to conventional concrete mixtures. For this reason, research about the phenomena of deterioration of high-performance concrete was intensified over the last decade. Currently, a large joint research project is the Priority Programme 2020 “Cyclic Deterioration of High-Performance Concrete in an Experimental-Virtual Lab” which is funded by the German Research Foundation (DFG). Within various tandem-projects experts in material science, building materials technology and numerical modeling are working together to identify and characterize the damage mechanisms under fatigue loading and to develop quantitative prediction models. On the occasion of the 65th birthday of Professor Ludger Lohaus, Institute of Building Materials Science at Leibniz University of Hannover, Germany, who is the initiator and coordinator of the aforementioned DFG Priority Programme 2020, this issue of “Structural Concrete” is partly dedicated to fatigue and cyclic behavior of concrete and concrete structures. Professor Lohaus has been very active in the research on concrete fatigue and has driven it forward in many regards. It has been his continuing effort to transfer fundamental research results into practice (especially in structures for offshore wind-energy) and standardization, whether for Eurocode 2, fib Model Code 2010 or for the current preparations for fib Model Code 2020. The undersigned congratulate him very warmly on his birthday—also on behalf of the involved researchers of the DFG Priority Programme 2020—and we wish him all the best for the future, especially good health. We hope you enjoy reading this issue and wish you new insights and inspirations. The authors are members of the Programme Committee of the DFG Priority Programme 2020 “Cyclic Deterioration of High-Performance Concrete in an Experimental-Virtual Lab,” funded by the German Research Foundation (DFG).

Lumbar spondylolisthesis: modern registries and the development of artificial intelligence.

OBJECTIVEThere are a wide variety of comparative treatment options in neurosurgery that do not lend themselves to traditional randomized controlled trials. The object of this article was to examine how clinical registries might be used to generate new evidence to support a particular treatment option when comparable options exist. Lumbar spondylolisthesis is used as an example.METHODSThe authors reviewed the literature examining the comparative effectiveness of decompression alone versus decompression with fusion for lumbar stenosis with degenerative spondylolisthesis. Modern data acquisition for the creation of registries was also reviewed with an eye toward how artificial intelligence for the treatment of lumbar spondylolisthesis might be explored.RESULTSCurrent randomized controlled trials differ on the importance of adding fusion when performing decompression for lumbar spondylolisthesis. Standardized approaches to extracting data from the electronic medical record as well as the ability to capture radiographic imaging and incorporate patient-reported outcomes (PROs) will ultimately lead to the development of modern, structured, data-filled registries that will lay the foundation for machine learning.CONCLUSIONSThere is a growing realization that patient experience, satisfaction, and outcomes are essential to improving the overall quality of spine care. There is a need to use practical, validated PRO tools in the quest to optimize outcomes within spine care. Registries will be designed to contain robust clinical data in which predictive analytics can be generated to develop and guide data-driven personalized spine care.

Application of Machine Learning Techniques for Predicting the Dynamic Response of Geogrid Reinforced Foundation Beds

This paper describes the application of artificial neural network (ANN) and genetic programming (GP) methods in predicting the dynamic response of geogrid reinforced machine foundation bed. The dataset used in both models was determined through field bock resonance tests. A series of field tests were conducted over the unreinforced and geogrid reinforced foundation beds. The dynamic response was studied in terms of displacement—frequency variation. The response of both unreinforced and reinforced conditions was studied under six different dynamic force levels. From the experimental results, the significant improvement in the machine foundation performance was observed in the presence of geogrid reinforcement. The formulations for predicting displacement amplitude were developed using ANN and GP. In the formulation, depth of placement of geogrid, eccentric angle, the natural frequency of foundation soil system, damping ratio, shear strain, shear modulus and the operating frequency of a machine were considered as input variables. Primarily, the statistical performance of the models was compared through different performance indices. In addition, different algorithms were described to identify the ranking of influencing parameters, which affect the dynamic response of a geogrid reinforced bed. From the analysis, the resonant parameters predicted from the models have shown good agreement with the field test results. The operating frequency was found to be the most influencing parameter for determining the displacement amplitude of the machine foundation bed. Further, the performance of the GP model was found more accurate for predicting the response of a system than the ANN model.

Undrained dynamic behaviour of peaty organic soil under long-term cyclic loading, Part II: Constitutive model and simulation

Based on the experimental evidences presented in Part I, an empirical equation for the peaty organic soil is derived for calculating the accumulated plastic strain, in which the influencing factors such as the amplitude and number of cyclic loading, the cyclic static deviator stress and the static strength are considered. By regarding the accumulated plastic deformation under long-term cyclic loading as static creep, a constitutive model is presented. The modified Cam Clay model is incorporated in the proposed model to determine the initial stress condition which is necessary for subsequent calculation of accumulated plastic strain. Then, the proposed model is implemented in a finite-element formulation by using an implicit stress integration algorithm. Finally, this model is evaluated and validated through the applications to specific boundary value problems including element tests presented in Part I, a flexible shallow foundation subjected to long-term cyclic load and a road with a low embankment subjected to traffic load. The proposed methodology can be used to calibrate the design of dynamic machine foundation, road and others that involve long-term repetitive loading.

A new principles for implementation and operation of foundations for machines: A review of recent advances

The aim of this paper is to present the most important issues on the implementation, operation and maintenance of foundation for machines. The article presents the newest solutions both in terms of technology implementation as well as materials used in construction of such structures. Foundations for machines are special building structures used to transfer loads from an operating machine to the subsoil. The purpose of these foundations is not just to transfer loads, but also to reduce vibrations occurring during operation of the machine, i.e. their damping and preventing redistribution to other elements of the building. It should be noted that foundations for machines (particularly foundations for hammers) are the most dynamically loaded building structures. For these reasons, they require precise static and dynamic calculations, accuracy in their implementation and care for them after they have been made. Therefore, the paper in detail present the guidelines regarding: design, construction and maintenance of structures of this type. Furthermore, the most important parameters and characteristics of materials used for the construction of these foundations are described. As a result of the conducted analyzes, it was found that the concrete mix, in foundations for machines, should have a low water/binder ratio. For its execution, it is necessary to use broken aggregates from igneous rocks and binders modified with mineral additives and chemical admixtures. On the other hand, the reinforcement of composites should contain a large amount of structural reinforcement to prevent shrinkage cracks.

Stress path dependent small strain stiffness of Shanghai clay

The soil small strain stiffness plays an important role in many geotechnical applications such as machine foundations, deep excavations and earthquake ground response analysis. In this study, the small strain stiffness of saturated intact Shanghai clay specimen is measured in a hollow cylinder apparatus. The lateral earth pressure coefficient at rest is measured first during the one-dimensional consolidation. After consolidation, the very small strain stiffness is obtained by shear wave measurement using bender elements, while the degradation of small strain stiffness with strain is investigated by quasi-static loading with high resolution linear variable displacement transducers (LVDT). The effect of stress path on the small strain stiffness is also investigated. The results show that the small strain stiffness is nonlinear and significantly depends on the stress path.

Damping Ratio of Foundation Bed with Multi-layered Rubber-Soil Mixtures

In this paper, a series of plate load tests on a sandy soil bed containing multiple layers of granulated rubber-soil mixture (RSM) under incremental cyclic loading was performed. To evaluate the settlement response and damping ratio of foundation bed, incremental cyclic loading in five steps with amplitudes of 140, 280, 420, 560 and 700 kPa were applied to the loading plate. The results show that both the total and residual settlements of the loading plate decrease with increase in the number of RSM layers, regardless of the level of applied cyclic load, but the rate of reduction in both settlements reduces with increase in the number of RSM layers. There is also an appreciable improvement in the value of the damping capacity with increase in the number of RSM layers as the damping ratio increases by 4-5% beyond the value of 12-15% obtained on untreated sand. On the basis of the study, the concept of using multiple RSM layers not only is a very attractive material to achieve less settlement and vibration attenuation for machine foundation and railway track beds, but also, the environmental impacts of waste tires are attenuated by using as composite materials in geotechnical applications.

Load Effect Impact on the Exploitation of Concrete Machine Foundations Used in the Gas and Oil Industry

Load Effect Impact on the Exploitation of Concrete Machine Foundations Used in the Gas and Oil Industry