Monotonic and cyclic load behaviour of helical pile connectors in the vertical direction

2006 ◽  
Vol 33 (1) ◽  
pp. 10-18 ◽  
Author(s):  
M A Youssef ◽  
M H El Naggar ◽  
M Ahmed
Keyword(s):  
Seismic Performance ◽  
Cyclic Load ◽  
Vertical Direction ◽  
Experimental Program ◽  
Seismic Resistance ◽  
Element Analysis ◽  
Existing Structures ◽  
Attractive Option ◽  
Loading Modes ◽  
The University

The helical pile is a foundation system that is used to support new residential and commercial buildings and to stabilize repairs of existing structures. It represents an attractive option to upgrade the seismic resistance of foundations. This necessitates a good understanding of the seismic performance of the specialized connectors linking the pile shaft to the concrete foundation. An experimental program is initiated at The University of Western Ontario to investigate the seismic performance of these connectors, to develop models that can be used in finite element analysis to describe their behaviour, and to propose modifications to enhance their seismic performance, if necessary. In this program, eight specimens were tested to assess the behaviour of two types of these connectors under different loading modes. It was concluded that connectors with an uplift bracket are required for seismic applications to control uplift displacement due to rocking of the foundation.Key words: helical pile, connector, experimental, model, monotonic load, cyclic load, foundation, stiffness, strength.

Seismic Rehabilitation of Reinforced Concrete Beam-Column Connections

1996 ◽  
Vol 12 (4) ◽  
pp. 761-780 ◽  
Author(s):  
A. Ghobarah ◽  
Tarek S. Aziz ◽  
Ashraf Biddah
Keyword(s):  
Reinforced Concrete ◽  
Cyclic Load ◽  
Concrete Structures ◽  
Reinforced Concrete Beam ◽  
Shear Capacity ◽  
Experimental Program ◽  
Reinforced Concrete Structures ◽  
Test Results ◽  
Seismic Rehabilitation ◽  
Existing Structures

As building codes are updated, some of the existing important structures may fall short of complying with current standards even though they may have been properly designed and constructed according to earlier codes. Many existing structures may be inadequate and may pose severe risk during seismic events. Rehabilitation measures to upgrade the capacity of these structures can be performed at some point in their useful lives especially when located in seismically active zones. A new method for improving the seismic performance of existing reinforced concrete structures is by jacketing the deficient connections using corrugated steel jackets. An experimental program was conducted to evaluate this method of rehabilitation. Corrugated steel jacketing addresses the particular weakness that is often found in existing reinforced concrete structures, namely the lack of sufficient shear reinforcement and the required confining reinforcement within the joints and in adjoining beams and columns. The performance of four reinforced concrete connections was determined experimentally. The test specimens include one connection representing existing structures, one designed according to current seismic codes and two rehabilitated connections. The test results showed satisfactory performance at high cyclic load levels and significant increase in the shear capacity and ductility of connections rehabilitated with corrugated steel jackets.

scholarly journals Experimental Study on Seismic Behavior of Masonry Walls Strengthened by Reinforced Mortar Cross Strips

2019 ◽  
Vol 11 (18) ◽  
pp. 4866 ◽  
Author(s):  
Dong ◽  
Sui ◽  
Jiang ◽  
Zhou
Keyword(s):  
Seismic Performance ◽  
Cyclic Load ◽  
Failure Modes ◽  
Shear Failure ◽  
Constant Load ◽  
Shear Capacity ◽  
Experimental Program ◽  
Test Results ◽  
Reinforced Masonry ◽  
Key Factor

Due to the poor seismic performance, strengthening of masonry structures is always a significant problem worthy to study. It has been proven that the bearing capacity of existing masonry buildings can be enhanced greatly with efficient strengthening measures. An experimental program was conducted to investigate seismic performance of un-reinforced masonry (URM) walls strengthened b,y reinforced mortar (RM) cross strips. Eleven walls were tested under horizontal low-cyclic load, simultaneously with a vertical constant load on the top face. Three URM walls were tested as reference. The other eight walls were externally strengthened with 40 and 60 mm thick of RM cross strips on one or both faces. Test results showed that externally strengthening with RM cross strips was an efficient way to enhance the seismic performance of URM walls. The failure modes were divided into shear failure and shear-compression failure. All the tested walls did not collapse until the test ended, while many diagonal cracks and few vertical cracks appeared on mortar strips. After strengthening, the shear capacity of the strengthened walls increased by at least 38.2%, and the reinforcement ratio was noted to be the key factor to influence the shear capacity with positive correlation. Besides, RM cross strips did improve deformation capacity greatly.

The 1-MeV Electron Microscope Installation at the University of Colorado

1973 ◽  
Vol 31 ◽  
pp. 8-9 ◽  
Author(s):  
Mircea Fotino
Keyword(s):  
Electron Microscopy ◽  
Developmental Biology ◽  
Transmission Electron Microscopy ◽  
Electron Microscope ◽  
National Institutes Of Health ◽  
Experimental Program ◽  
University Of Colorado ◽  
Transmission Electron ◽  
The University ◽  
Research Resources

A new 1-MeV transmission electron microscope (Model JEM-1000) was installed at the Department of Molecular, Cellular and Developmental Biology of the University of Colorado in Boulder during the summer and fall of 1972 under the sponsorship of the Division of Research Resources of the National Institutes of Health. The installation was completed in October, 1972. It is installed primarily for the study of biological materials without many of the limitations hitherto unavoidable in standard transmission electron microscopy. Only the technical characteristics of the installation are briefly reviewed here. A more detailed discussion of the experimental program under way is being published elsewhere.

scholarly journals Comparison of one versus two maxillary molars distalization with iPanda: a finite element analysis

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Kamontip Sujaritwanid ◽  
Boonsiva Suzuki ◽  
Eduardo Yugo Suzuki
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Alveolar Bone ◽  
Vertical Direction ◽  
Minimal Amount ◽  
Element Analysis ◽  
Molar Distalization ◽  
Second Molar ◽  
Maxillary Molars ◽  
Displacement Patterns

Abstract Background The purpose of this study was to compare the stress distribution and displacement patterns of the one versus two maxillary molars distalization with iPanda and to evaluate the biomechanical effect of distalization on the iPanda using the finite element method. Methods The finite element models of a maxillary arch with complete dentition, periodontal ligament, palatal and alveolar bone, and an iPanda connected to a pair of midpalatal miniscrews were created. Two models were created to simulate maxillary molar distalization. In the first model, the iPanda was connected to the second molar to simulate a single molar distalization. In the second model, the iPanda was connected to the first molar to simulate “en-masse” first and second molar distalization. A varying force from 50 to 200 g was applied. The stress distribution and displacement patterns were analyzed. Results For one molar, the stress was concentrated at the furcation and along the distal surface in all roots with a large amount of distalization and distobuccal crown tipping. For two molars, the stress in the first molar was 10 times higher than in the second molar with a great tendency for buccal tipping and a minimal amount of distalization. Moreover, the stress concentration on the distal miniscrew was six times higher than in the mesial miniscrew with an extrusive and intrusive vector, respectively. Conclusions Individual molar distalization provides the most effective stress distribution and displacement patterns with reduced force levels. In contrast, the en-masse distalization of two molars results in increased force levels with undesirable effects in the transverse and vertical direction.

scholarly journals Experimental Study on the Behavior of Existing Reinforced Concrete Multi-Column Piers under Earthquake Loading

2021 ◽  
Vol 11 (6) ◽  
pp. 2652
Author(s):  
Jung Han Kim ◽  
Ick-Hyun Kim ◽  
Jin Ho Lee
Keyword(s):  
Seismic Performance ◽  
Seismic Design ◽  
Bridge Piers ◽  
Scale Model ◽  
Inertia Force ◽  
Small Scale ◽  
Lap Splice ◽  
Existing Structures ◽  
Seismic Design Code ◽  
Seismic Force

When a seismic force acts on bridges, the pier can be damaged by the horizontal inertia force of the superstructure. To prevent this failure, criteria for seismic reinforcement details have been developed in many design codes. However, in moderate seismicity regions, many existing bridges were constructed without considering seismic detail because the detailed seismic design code was only applied recently. These existing structures should be retrofitted by evaluating their seismic performance. Even if the seismic design criteria are not applied, it cannot be concluded that the structure does not have adequate seismic performance. In particular, the performance of a lap-spliced reinforcement bar at a construction joint applied by past practices cannot be easily evaluated analytically. Therefore, experimental tests on the bridge piers considering a non-seismic detail of existing structures need to be performed to evaluate the seismic performance. For this reason, six small scale specimens according to existing bridge piers were constructed and seismic performances were evaluated experimentally. The three types of reinforcement detail were adjusted, including a lap-splice for construction joints. Quasi-static loading tests were performed for three types of scale model with two-column piers in both the longitudinal and transverse directions. From the test results, the effect on the failure mechanism of the lap-splice and transverse reinforcement ratio were investigated. The difference in failure characteristics according to the loading direction was investigated by the location of plastic hinges. Finally, the seismic capacity related to the displacement ductility factor and the absorbed energy by hysteresis behavior for each test were obtained and discussed.

scholarly journals Effects of Loading and Boundary Conditions on the Performance of Ultrasound Compressional Viscoelastography: A Computational Simulation Study to Guide Experimental Design

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2590
Author(s):  
Che-Yu Lin ◽  
Ke-Vin Chang
Keyword(s):  
Boundary Conditions ◽  
Simulation Study ◽  
Viscoelastic Properties ◽  
Measurement Accuracy ◽  
Computational Simulation ◽  
Vertical Direction ◽  
Fixation Method ◽  
Element Analysis ◽  
Sample Container

Most biomaterials and tissues are viscoelastic; thus, evaluating viscoelastic properties is important for numerous biomedical applications. Compressional viscoelastography is an ultrasound imaging technique used for measuring the viscoelastic properties of biomaterials and tissues. It analyzes the creep behavior of a material under an external mechanical compression. The aim of this study is to use finite element analysis to investigate how loading conditions (the distribution of the applied compressional pressure on the surface of the sample) and boundary conditions (the fixation method used to stabilize the sample) can affect the measurement accuracy of compressional viscoelastography. The results show that loading and boundary conditions in computational simulations of compressional viscoelastography can severely affect the measurement accuracy of the viscoelastic properties of materials. The measurement can only be accurate if the compressional pressure is exerted on the entire top surface of the sample, as well as if the bottom of the sample is fixed only along the vertical direction. These findings imply that, in an experimental validation study, the phantom design should take into account that the surface area of the pressure plate must be equal to or larger than that of the top surface of the sample, and the sample should be placed directly on the testing platform without any fixation (such as a sample container). The findings indicate that when applying compressional viscoelastography to real tissues in vivo, consideration should be given to the representative loading and boundary conditions. The findings of the present simulation study will provide a reference for experimental phantom designs regarding loading and boundary conditions, as well as guidance towards validating the experimental results of compressional viscoelastography.

scholarly journals Support structure design for New Zealand Forest Products Ltd's No. 5 Recovery Boiler

1987 ◽  
Vol 20 (1) ◽  
pp. 2-6
Author(s):  
R. D. Sharpe
Keyword(s):  
New Zealand ◽  
Seismic Performance ◽  
Time History ◽  
Forest Products ◽  
Structure Design ◽  
Seismic Resistance ◽  
Simple Application ◽  
Major Earthquake ◽  
Lateral Forces ◽  
Industrial Boilers

Internationally, the seismic resistance of large industrial boilers appears to be addressed by the most simple application of relatively low equivalent static lateral forces which are resisted elastically. This paper describes measures taken to ensure a predictable
and controlled seismic performance of such a boiler
during a major earthquake. Inelastic time-history methods of analysis were used to confirm that the desired performance would be achieved. As a result the client was able to purchase a relatively standard boiler in the international marketplace and still achieve a level of seismic resistance consistent with the best NZ practices.

scholarly journals “TORINO 1911” PROJECT: A CONTRIBUTION OF A SLAM-BASED SURVEY TO EXTENSIVE 3D HERITAGE MODELING

2018 ◽  
Vol XLII-2 ◽  
pp. 225-234 ◽  
Author(s):  
F. Chiabrando ◽  
C. Della Coletta ◽  
G. Sammartano ◽  
A. Spanò ◽  
A. Spreafico
Keyword(s):  
3D Model ◽  
Handheld Devices ◽  
Complex Environments ◽  
Existing Structures ◽  
Multi Scale ◽  
Rapid Mapping ◽  
Digital Documentation ◽  
Immersive Visualization ◽  
Interactive Navigation ◽  
The University

In the framework of the digital documentation of complex environments the advanced Geomatics researches offers integrated solution and multi-sensor strategies for the 3D accurate reconstruction of stratified structures and articulated volumes in the heritage domain. The use of handheld devices for rapid mapping, both image- and range-based, can help the production of suitable easy-to use and easy-navigable 3D model for documentation projects. These types of reality-based modelling could support, with their tailored integrated geometric and radiometric aspects, valorisation and communication projects including virtual reconstructions, interactive navigation settings, immersive reality for dissemination purposes and evoking past places and atmospheres. The aim of this research is localized within the “Torino 1911” project, led by the University of San Diego (California) in cooperation with the PoliTo. The entire project is conceived for multi-scale reconstruction of the real and no longer existing structures in the whole park space of more than 400,000&amp;thinsp;m<sup>2</sup>, for a virtual and immersive visualization of the Turin 1911 International “Fabulous Exposition” event, settled in the Valentino Park. Particularly, in the presented research, a 3D metric documentation workflow is proposed and validated in order to integrate the potentialities of LiDAR mapping by handheld SLAM-based device, the ZEB REVO Real Time instrument by GeoSLAM (2017 release), instead of TLS consolidated systems. Starting from these kind of models, the crucial aspects of the trajectories performances in the 3D reconstruction and the radiometric content from imaging approaches are considered, specifically by means of compared use of common DSLR cameras and portable sensors.

scholarly journals Evaluation of the behavior system locator associated with a removable partial denture, finite element analysis

2018 ◽  
Vol 25 (2) ◽  
pp. 10
Author(s):  
Medardo Alexander Arenas-Chavarria ◽  
Samuel David Giraldo-Gómez ◽  
Federico Latorre-Correa ◽  
Junes Abdul Villarraga-Ossa
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Permanent Deformation ◽  
Vertical Direction ◽  
Cobalt Chromium ◽  
Removable Partial Denture ◽  
Element Analysis ◽  
Partial Denture ◽  
Solid Works ◽  
Von Mises

Aim: The purpose of this research was to evaluate the behavior of the system locator settings associated with distal extension removable partial denture lower (PPR) by finite element analysis (FEA). Materials and Methods: A Class II Kennedy 3D model using a CAD software Solid Works 2010 (SolidWorks Corp., Concord, MA, USA), and subsequently processed and analyzed by ANSYS Software version Model 14. One (1) was designed implant Tapered Screw -Vent® (ref TSVB10 Zimmer Dental-Carlsbad,CA,USA.) length x 10mm diameter 3.7mm with a 3.5mm platform, internal hexagon with its respective screw fixation; this was located at the tooth 37 as a rear pillar of a PPR, whose major connector was a lingual bar casting (alloy cobalt chromium), based combined (metal/ acrylic) with teeth to replace (37, 36 and 35). Efforts were evaluated von Mises in a 400N load. This analysis allowed assessing the performance of various prosthetic structures modeled and generated effects on bone-implant interface. Results: Differences between the values von Mises in all structures and loads were observed before there was no permanent deformation in any of them. Structures such as bone showed in normal values microstrain. Conclusions: The behavior of the PPRimplant connection, showed a favorable distribution efforts by using a PPR, subjecting it to load in the vertical direction.

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