Vertical Load Tests Research Articles

Análisis por elementos finitos del desempeño estructural de jaula de seguridad para vehículo Renault Logan bajo normatividad FIA

Este artículo presenta el análisis estructural de una jaula de seguridad para Renault Logan 2005 bajo la normatividad de la Federación Internacional de Automovilismo para vehículos de turismo; particularmente, se considera el ensayo de carga vertical sobre el arco principal. Se llevaron a cabo simulaciones por medio de un software de elementos finitos, en las cuales se definieron la geometría y material usado, además de establecer las condiciones de frontera, carga y contactos. Se analizó el comportamiento mecánico bajo la carga exigida por FIA de 90 KN teniendo en cuenta el criterio de falla de la energía de distorsión y la deformación total. Posteriormente, se encontró que deformaciones permanentes pueden originarse por encima de 32.2 KN, mientras que fallas localizadas pueden presentarse por encima de 44 KN. Hay que mencionar además que los resultados demuestran que la implementación de las exigencias mínimas geométricas, de material y de manufactura de FIA no garantizan necesariamente la seguridad de la estructura.

Design of a Novel Carbon-Fiber Ankle-Foot Prosthetic using Finite Element Modeling

Recently, researchers worldwide have made considerable efforts to enhance amputees’ quality of life by designing improved prosthetic feet. The ideal prosthetic for this job is that one which seamlessly mimics the functions of the human foot. To achieve this objective, accurate design is thus required. In this paper, a novel design for a carbon-fibre ankle-foot prosthetic is considered. The geometry of the designed ankle-foot prosthetic was created to satisfy a wide range of anthropometric parameters, taking into consideration the available previous designs in the published literature. AutoCAD version 15 was used in this work for modeling and creating the geometry, and ANSYS Workbench software version 16.1 was used for the finite element modelling based on geometry retrieved from the AutoCAD software. The complexity of the suggested design was simplified by partitioning the design into parts according to function. The roll-over shape concept was considered in the current design, which acts as an important tool in the design, evaluation, and alignment of lower limb prostheses and orthoses. Carbon fibre-epoxy composite material was utilised to manufacture a light and high strength prosthetic foot. The current study revealed that the proposed design offered a smooth roll-over shape and good response to energy return requirements in ankle-foot prosthetics, with the keel and heel design behaving as a non-prismatic cantilever beam. The keel and heel thickness require optimisation based on the specific materials used. FE analysis showed successful heel and keel deflections, although inadequate deflection was demonstrated in the vertical loading test. The heel deflected by 29.18 mm under a load of 300 N, while the keel deflected more than 25 mm under 1,230 N, and the deflection under a vertical load of 1,230 N was about 8.1 mm. The strain and stress seen in the three tests were within safe limits, while most of the energy was absorbed in the ankle component of the prosthesis.

Implant-to-bone force transmission: a pilot study for in vivo strain gauge measurement technique

The experimental determination of local bone deformations due to implant loading would allow for a better understanding of the biomechanical behavior of the bone-implant-prosthesis system as well as the influence of uneven force distribution on the onset of implant complications. The present study aimed at describing an innovative in vivo strain gauge measurement technique to evaluate implant-to-bone force transmission, assessing whether and how oral implants can transfer occlusal forces through maxillary bones.In vivo force measurements were performed in the maxillary premolar region of a male patient who had previously received a successful osseointegrated titanium implant. Three linear mini-strain gauges were bonded onto three different buccal cortical bone locations (i.e. coronal, middle, apical) and connected to strain measuring hardware and software. A customized screw-retained abutment was manufactured to allow for vertical and horizontal loading tests.As to the vertical load test, the patient was instructed to bite on a load cell applying his maximum occlusal force for 20 s and then recovering for 10 s to restore the bone unstrained state; the test was repeated 20 times consecutively. As regards the horizontal load test, the implant was subjected to a total of 20 load applications with force intensities of 5 and 10 kg. During the tests, the recorded signals were plotted in real time on a graph as a function of time by means of a strain analysis software.The described strain gauge measurement technique proved to be effective in recording the forces transmitted from osseointegrated implants to the cortical bone. Horizontal loads caused higher deformations of cortical bone than vertical biting forces; in both situations, the deformation induced by the force transferred from the implant to the bone progressively decreased from the coronal to the apical third of the alveolar ridge. At approximately 9 mm from the implant neck, the effect of occlusal force transmission through osseointegrated titanium implants was negligible if compared to the apical region.

Response of suction caissons for tidal current turbine applications in soft clay to monotonic and cyclic vertical loading

In soft marine clays, suction caissons provide a foundation system for tidal current turbines that further promote the sustainable nature of the system by allowing for their removal at the end of the structure’s design life. When configured as a multipod, the moment loads resulting from the horizontal flow of water will be transferred to the suction caissons as compression–uplift loads on opposing foundation legs. The behavior of a suction caisson in soft clay was investigated at aspect ratios of 1 and 2 under monotonic and cyclic vertical loading applicable to multipod-supported tidal current turbine design. Installation and solely monotonic vertical load tests indicated lower back-calculated adhesion factor, α, values and higher back-calculated bearing capacity factor, Nc, values than design standards recommend. The capacity and stiffness response of the foundation after undergoing cyclic loading was found to be largely dependent on the magnitude of displacement the foundation underwent during cyclic loading. Additionally, a threshold of elastic foundation response was observed during cyclic loading defined by a cyclic displacement amplitude. These results indicate serviceability constraints will be critical in the design of suction caisson foundations for tidal current turbine applications.

Experimental study of geotextile as plinth beam in a pile group-supported modeled building frame

This paper presents the experimental results of static vertical load tests on a model building frame with geotextile as plinth beam supported by pile groups embedded in cohesionless soil (sand). The experimental results have been compared with those obtained from the nonlinear FEA and conventional method of analysis. The results revealed that the conventional method of analysis gives a shear force of about 53%, bending moment at the top of the column about 17% and at the base of the column about 50–98% higher than that by the nonlinear FEA for the frame with geotextile as plinth beam.

Bonding characteristics of grouting layer in Prefabricated Cement Concrete Pavement

In order to select an optimum grouting layer to apply to Prefabricated Cement Concrete Pavement, small rectangular-section beam specimens have been used to simulate the airport pavement surface, and the test sections of stabilized soils have been paved indoor as the base layer. An orthogonal test program consisting of four factors (i.e. grouting type, slab bottom roughness, grouting thickness and base structure) at three levels has been designed, in which the vertical static loading, vertical fatigue loading and lateral loading tests have been carried out. The results show that the ordinary cement mortar (PTC) is the most fluid, and the fast setting and hardening cement mortar (SKC) has the highest strength on Day 1 of curing, but its strength increases slowly thereafter. On the other hand, the strength of PTC is the highest on Day 28 of curing. The effect of slab bottom roughness on the bonding performance between the grouting layer and the surface layer is the most significant, while the grouting type has the greatest effect on the bonding performance between the grouting layer and the base layer, and on the bearing capacity of the pavement structure. After the fatigue loading, the neutral surface of the pavement surface layer has shifted upwards. The results show that there are three phases in the relationship between the deflection, pressure and number of fatigue loading times. The first phase is the large change, the second phase is the linear change and the third phase is the constant phase. Under the lateral loading, the bonding performance between the non-shrink grouting material with high strength (CGM) and the base layer is the best, and there is a quadratic polynomial relationship between the lateral load and the superstructure’s displacement. When the grouting material is 2.0cm thick CGM, the bottom of the slab is smooth, and when the basic structure is 12% cement stabilized soil, the pavement structure has the best properties to carry the fatigue load and the lateral load.

Experimental and Numerical Investigations of Composite Frames with Innovative Composite Transfer Beams

Experimental and numerical studies were conducted to investigate the vertical load-carrying behavior and seismic performance of a composite frame structure with an innovative composite transfer beam, which was proposed to overcome the disadvantages of traditional reinforced concrete or steel reinforced concrete transfer beams. In the experimental study, a vertical monotonic loading test and a lateral cyclic loading test were conducted. The test observations, load–displacement curves, and strain measurements were discussed to investigate the structural performance and failure mechanism. The experimental results demonstrated the excellent vertical load-carrying behavior and seismic performance of the composite transfer frame. The characteristics of the plastic hinge distribution were investigated based on extensive data of the steel strains measured to reveal the typical failure mechanism of the composite transfer frame. In the numerical simulation analysis, a multiscale modeling scheme was developed to make full use of the fiber beam–column elements and multilayer shell elements. Comparisons with the experimental results showed that the developed model predicted the overall structural behavior, the individual story and component behavior, and the failure mechanism with a reasonable level of accuracy. In addition, both the experimental tests and numerical analyses indicated that the shear deformation mode and the energy dissipation in the composite joint core were also significant mechanical characteristics of the composite transfer frame.

Study on Ultimate State and Mechanical Characteristics of Connection Joint of Damaged H-Shaped Bracing Structure

In Japan, various kinds of failure modes in steel structures have been reported in severe past earthquake disasters. Also, the various type of repair method for damaged building structure is suggested, and it has been published as restoration manual and guideline. However, it is guessed that these repair methods have some difficulties related to construction technique and estimation of recovery of seismic resistant performance after repair. This study focuses on the seismic ultimate state of steel brace connection of original state and repaired state after damaged, and the effective restoration method is suggested herein. In our past researches, new repairing method for damaged steel bracing joint which has angle-section brace member has been suggested already, and its applicability and feasibility were investigated experimentally. Herein, H- shaped section brace members are focused which are adopted on middle-rise or high-rise steel building structures, and also, various kinds of failure modes of these bracing structure has been reported after past terrible seismic disasters in Japan. So, the effective restoration method is proposed here. First, to reproduce the seismic ultimate state, the vertical loading test on H-shaped bracing test specimen are performed as parameters with bolt layout, thickness of gusset plate, that is, out-of-plane rigidity of joint. Next, the damaged bracing joints are repaired. Finally, the loading test is done on repaired specimen again. From test results, the restoring force characteristics after repair can be recovered, and any type of failure modes are observed. So, 3D model of damaged bracing joint is constructed by using 3D scanner, and it helps to identify the failure mode and yield lines on gusset plate. Furthermore, the plastic limit analysis is performed by reference of 3D model, and it can predict the ultimate state of test results well.

高速炉に適用する厚肉積層ゴムの研究開発（準実大厚肉積層ゴムを用いた経年特性試験）

A seismic isolation system composed of a thick rubber bearing and an oil damper has been developed for Sodium-Cooled Fast Reactor. One of the advantages of the isolation system is the use of thick rubber bearings to ensure the longer vertical natural period of a plant, thereby mitigating seismic loads to mechanical components. Characteristics of thick rubber bearings have been confirmed through a series of tests. This paper focused on the aging properties of thick rubber bearings, such as basic mechanical properties and ultimate strength. An aging test of thick rubber bearings was conducted using 1/2-scale (800 mm diameter) and 1/8-scale (200 mm diameter) rubber bearings. Aging of the rubber bearings was reproduced using thermal degradation based on Arrhenius law, in which the target of aging periods was 60 years, plant life time. The hysteresis loops of the thick rubber bearings after aging were obtained through horizontal and vertical static loading tests, and the effects of aging were evaluated by comparison with the initial mechanical properties. In addition, for the purpose of further research, the effect of scale by aging was clarified to compare the mechanical properties between the 1/2-scale and 1/8-scale rubber bearings.

Static and Dynamic Load Tests of Shaft and Base Grouted Concrete Piles

This paper examines shaft and base grouted concrete piles by conducting vertical static load tests (SLTs) and dynamic load tests. Three concrete piles with shaft and base grouting, with base grouting only, and without grouting techniques were selected, and compressive SLTs were conducted. Two piles with grouting were also assessed with dynamic load tests. Another two uplift SLTs were conducted to one shaft and base grouted pile and one pile without grouting. Traditional presentations were provided to check whether the bored piles reached the design requirement. Interpretations of test results were also provided to determine the ultimate pile capacity. Results from these 5 SLT programs indicated that double-tangent and DeBeer's methods are close to each other, and Chin's method overestimates the pile capacity. Comparison of the results from the SLTs and dynamic load tests shows that the results from Chin's method are close to dynamic results, and Mazurkiewicz's method overestimates for friction resistance. The results also demonstrate that base and shaft grouted pile and base grouted pile increase by 9.82% and 2.89% in compressive capacity, respectively, and compared to the uplift SLTs; there is a 15.7% increment in pile capacity after using base and shaft grouting technology.

踏面磨耗对高速列车转向架构架垂向载荷特性影响研究

本文提出了一种高速列车垂向载荷测试方法，通过运行线路测试，获得了踏面磨耗前后的垂向载荷时间历程。从时域和频域分别分析了高速列车通过直线、道岔、进出车站等典型运用工况下的垂向载荷特性，进而编制了高速列车转向架构架垂向谱。 A vertical load test method for high-speed trains was presented in this paper, the loads, under the new state and worn state of the profile, were achieved through experiments. The test data of typical working conditions of high speed trains through straight lines, turnouts, passing in and out stations were analyzed both in the time domain and in the frequency domain in order to evaluate the effect of profile wear on load characteristics of bogie frame and the load spectrum of vertical load was established.

Sands subjected to repetitive vertical loading under zero lateral strain: accumulation models, terminal densities, and settlement

Geosystems often experience numerous loading cycles. Plastic strain accumulation during repetitive mechanical loads can lead to shear shakedown or continued shear ratcheting; in all cases, volumetric strains diminish as the specimen evolves towards terminal density. Previously suggested models and new functions are identified to fit plastic strain accumulation data. All accumulation models are formulated to capture terminal density (volumetric strain) and either shakedown or ratcheting (shear strain). Repetitive vertical loading tests under zero lateral strain conditions are conducted using three different sands packed at initially low and high densities. Test results show that plastic strain accumulation for all sands and density conditions can be captured in the same dimensionless plot defined in terms of the initial relative density, terminal density, and ratio between the amplitude of the repetitive load and the initial static load. This observation allows us to advance a simple but robust procedure to estimate the maximum one-dimensional settlement that a foundation could experience if subjected to repetitive loads.

Investigation of the seismic response of high‐rise buildings supported on tension‐resistant elastomeric isolation bearings

SummaryIn many applications of seismic isolation, such as in high‐rise construction, lightweight construction, and structures with large height‐to‐width aspect ratios, significant tension forces can develop in bearings, raising concerns about the possible rupture of elastomeric bearings and the uplift of sliding bearings. In this paper, a novel tension‐resistant lead plug rubber bearing (TLRB) with improved tension‐resisting capabilities is developed and experimentally and numerically assessed. This TLRB consists of a common lead plug rubber bearing (LRB) and several helical springs. After describing the theory underlying the behavior of the TLRB, the mechanical properties of reduced‐scale prototype bearings are investigated through extensive horizontal and vertical loading tests. The test results indicate that TLRBs can improve the shear stiffness and tension resistance capacity even under significant tensile loads. A series of shaking table tests on scaled models of high‐rise buildings with different aspect ratios were conducted to investigate the dynamic performance of the TLRB and the seismic responses of base‐isolated high‐rise buildings. Three different cases were considered in the shaking table tests: a fixed base condition and the use of TLRB and LRB isolation systems. The results of the shaking table test show that (a) base‐isolated systems are effective in reducing the structural responses of high‐rise buildings; (b) an isolated structure's aspect ratio is an important factor influencing its dynamic response; (c) TLRBs can endure large tensile stresses and avoid rupture on rubber bearings under strong earthquakes; and (d) the experimental and numerical results of the responses of the models show good agreement. Copyright © 2016 John Wiley & Sons, Ltd.

SIDE FRICTION OF DRILLED PILES IN COBBLE LAYERS

Full scale vertical load tests have been carried out on drilled piles in cobble layers to evaluate side friction capacity. In the finite element analysis, firstly the property of pile is assumed linear elastic and the elastic-plastic Mohr-Coulomb model is used for the cobble layer. Interface elements are introduced to model interface interaction between pile and cobble layer. The measured data obtained from the field tests are compared with the finite element simulation results using PLAXIS 2D. It shows reasonable agreement between field test data and simulation results. A preliminary evaluation of side friction of drilled piles in cobble layers based on Rollins et al. design equation is also made after assembling the available load test data and numerical analyses. A modified equation is proposed to estimate the ultimate unit side friction of drilled piles in cobble layers for design purpose.

Behaviour of Piled Raft in Pyroclastic Soil

A piled raft is a composed foundation in which the raft is in contact with soil. The applied vertical load is transferred from the raft to the soil and to the pile heads. The load sharing between the piles and the soil is a function of the complex interaction among the raft, the soil and the pile. Considering the complexity of the problem, the best way to investigate about this interaction is to perform physical model tests at field scale. Vertical load tests on different types of foundations (single pile, unpiled raft, pile group with a free-standing cap and a piled raft composed by 5 piles) in pyroclastic soil have been performed. The raft settlement and the axial load distribution along the pile shaft were monitored during all the tests.

Ground Improvement with Jet Grouting Solutions at the New Cruise Terminal in Lisbon, Portugal

The “Terreiro do Trigo” dockyard, at the “Jardim do Tabaco”, was filled in order to allow the construction of the new “Santa Apolónia” Cruise Terminal in Lisbon, at the Tagus River right bank. A load transfer platform (LTP), founded over jet grouting columns, allowed the construction of a 4,2m height embankment, placed over a soft muddy alluvium layer (undrained shear stress lesser than 20kPa) with about 20m of average thickness. Vertical full scale load tests were performed in order to assess the possibility to incorporate the jet grouting columns, reinforced with steel micropiles, as foundation solution for the new Cruise Terminal building. The design criteria of the jet grouting columns, including the quality control and quality assurance, are presented, as well as the main results of the adopted monitoring and survey plan. The main results of the full scale load tests are pointed out. Finally, the technical and economic advantages of the adopted solutions, comparing with some more conventional ones, are presented.

In Vitro Mechanical Analysis of Different Techniques of Internal Fixation of Combined Mandibular Angle and Body Fractures

To evaluate in vitro resistance of 5 techniques of internal fixation of bilateral fractures involving the mandibular angle and body. Twenty-five polyurethane mandibles were used as substrates, fixed with a 2-mm fixation system, and divided into 5 groups: I, 1 4-hole plate, without intermediate space, in the neutral zone of the mandibular body and another similar plate in the external oblique ridge of the contralateral mandibular angle; II, 1 6-hole plate, with intermediate space, in the neutral zone of the mandibular body and a similar plate in the external oblique ridge of the left mandibular angle; III, 1 4-hole locking plate, with intermediate space, in the right neutral zone and another similar plate in the left external oblique ridge; IV, 2 4-hole plates, with intermediate space, one in the tension zone and the other in the compression zone of the mandibular body, and 1 4-hole plate, with intermediate space, in the external oblique ridge of the contralateral mandibular angle; V, 2 4-hole plates with intermediate space, one in the tension zone and the other in the compression zone of the mandibular body and similarly in the buccal side of the left mandibular angle. Mandibles were subjected to vertical linear load tests by a mechanical testing machine (Instron 4411, Instron Corp, Norwood, MA) to record peak load and load for displacements of 3, 5, and 7 mm. Group I had the least mechanical resistance of all groups, regardless of displacement, and group IV had the greatest mechanical resistance. Among groups II, III, and V, there was no statistically meaningful difference. Fixation of bilateral mandibular fractures involving the mandibular angle and body using 2 plates in the region of the body and 1 plate in the tension zone in the region of the mandibular angle was the technique that presented the best mechanical resistance.

Flexural load tests of full-scale recycled aggregates concrete structures

In order to study the behaviour of concrete structures made with coarse crushed concrete aggregates recycled from discarded elements from the precasting industry, extensive testing was performed in four full-scale structures with varying recycled aggregate (RA) ratios. This paper describes and analyses the results of vertical load tests on each slab of these double-floor structures. The Young’s modulus (E) of the concrete mixes was estimated by finite element model calibration using deflection data from the tests. The response pattern of the various structures was the same and the aggregates used had a small influence on E, even smaller than the execution conditions. One of the concrete mixes included a superplasticizer (SP) and this product more than offset the loss of stiffness due to RA use. To the authors’ best knowledge this is the first study ever concerning the behaviour of full-scale recycled aggregate concrete (RAC) structures subjected to vertical loading and the behaviour of slabs with significant replacement of conventional aggregates by RA.

Investigation of ultra high performance concrete piles for integral abutment bridges

The American Association of State Highway Transportation Officials (AASHTO) recently calls for increasing service life of bridges and optimizing structural systems. To extend its service life, this paper focuses on using an advanced Ultra High Performance Concrete (UHPC) as an alternative material for integral abutment bridge pile foundations. A parametric analysis was performed to understand the effects of key parameters in the performance of the UHPC piles. Results from this study provided the necessary technical background for selecting a test site and designing a field test for the UHPC pile as well as for future field monitoring of UHPC pile. A series of field testing was conducted to evaluate the behaviors of two 230-mm, H-shaped, UHPC test piles (i.e., P3 and P4), driven in clayey silt to silty clay, as well as a structural splice on P4 during pile installation, vertical, and lateral load tests. The field test results confirm that UHPC piles have exceeded the target axial and lateral capacities, sufficient driving resistance, and adequate performance of the splice. The analytical and experimental results provided the technical background knowledge of using UHPC and established the basis for more future research that would consider other influential factors.

Installation Effects of Controlled Modulus Column Ground Improvement Piles on Surrounding Soil

AbstractThe installation of foundations and ground improvement systems alters soil stresses affecting their soil-structure interaction and behavior under vertical loading. The installation effects have been investigated for several foundation types, especially for driven piles; however, experimental full-scale investigations of drilled displacement piles are very limited. This paper focuses on investigating the short-term installation effects of controlled modulus columns (CMCs) using an instrumented full-scale field test unit. The soil was instrumented using push-in pressure sensors (PS) and shape acceleration arrays (SAAs) to monitor the evolution of soil horizontal stresses, pore water pressures, and lateral displacements during installation and vertical load test. These sensors were installed at approximately 1D, 2D, 3D, and 4D from the outside surface of the CMC shaft, where D is the diameter of the CMC. The measurements presented in this paper clearly show that the soil experienced an increase of ho...