Strain Patterns Across the Root-Stem Transition Zone in Urban Trees

2020 ◽  
Vol 46 (5) ◽  
pp. 321-332
Author(s):  
Kenneth Beezley ◽  
Gregory Dahle ◽  
Jason Miesbauer ◽  
David DeVallance
Keyword(s):  
Transition Zone ◽  
Static Load ◽  
Root Zone ◽  
Compressive Strain ◽  
Premature Mortality ◽  
Well Being ◽  
Urban Trees ◽  
Image Correlation ◽  
Load Tests ◽  
Tangential Orientation

Trees are subjected to mechanical loading during their life span or face premature mortality. The strain resulting from loads intercepted by the canopy and transferred throughout the tree is of significant importance, not only for the survival of the tree, but for the safety and well-being of the human population found in close proximity. To test the function of tree orientation to an applied load, static load tests were conducted on 15 mature pin oak trees (Quercus palustris Muenchh.). We applied the static load tests to tilt the trees 0.1° from natural position. We used a digital image correlation system to map strain in the leeward, windward, and tangential roots in the root-stem transition zone. Results indicate that mean maximum strain magnitudes are similar in the leeward and windward orientations and lower on the tangential orientation. The leeward orientation experienced compressive strain, the windward orientation experienced tensile strain, and the tangential orientation had both tensile and compressive strain. This information provides the arboricultural and plant science sectors with a better understanding of how loading force moves through trees and will further enhance tree risk assessment and root zone management protocols.

Research on Static Load Tests of Damaged Bridge Strengthened with Pre-Stressed HFRP

2014 ◽  
Vol 1079-1080 ◽  
pp. 258-265
Author(s):  
Chen Ning Cai ◽  
Shan He ◽  
Li Na Liu ◽  
Shi Kun Ou
Keyword(s):  
Static Load ◽  
Flexural Rigidity ◽  
Fiber Reinforced Polymer ◽  
Test Results ◽  
Structural Members ◽  
Fiber Reinforced ◽  
Hybrid Fiber ◽  
Reinforced Polymer ◽  
Glass Fiber Reinforced ◽  
Load Tests

Thispaper presents an experimental study to strengthen an existing bridge usingpre-stressed carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer(GFRP) materials. The method using pre-stressed hybrid fiber reinforced polymer(HFRP) to strengthened structural members is an emerging pre-stressed strengtheningtechnology. In this study, experimental data selected from result of staticloading test conducted to hollow slabs with CFRP/GFRP has been compared with specimenswithout strengthening. Test results showed that the strengthening methoddeveloped in this study could effectively reduce the stress in hollow slab,improving the flexural rigidity and inhibiting the concrete from fracture.

scholarly journals Pressure Orientation-Dependent Recovery of 3D-Printed PLA Objects with Varying Infill Degree

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1275 ◽  
Author(s):  
Guido Ehrmann ◽  
Andrea Ehrmann
Keyword(s):  
Shape Memory ◽  
Fused Deposition Modeling ◽  
Static Load ◽  
Shape Memory Polymer ◽  
Applied Pressure ◽  
Poly Lactic Acid ◽  
Fused Deposition ◽  
Deposition Modeling ◽  
Load Tests ◽  
3D Printed

Poly(lactic acid) is not only one of the most often used materials for 3D printing via fused deposition modeling (FDM), but also a shape-memory polymer. This means that objects printed from PLA can, to a certain extent, be deformed and regenerate their original shape automatically when they are heated to a moderate temperature of about 60–100 °C. It is important to note that pure PLA cannot restore broken bonds, so that it is necessary to find structures which can take up large forces by deformation without full breaks. Here we report on the continuation of previous tests on 3D-printed cubes with different infill patterns and degrees, now investigating the influence of the orientation of the applied pressure on the recovery properties. We find that for the applied gyroid pattern, indentation on the front parallel to the layers gives the worst recovery due to nearly full layer separation, while indentation on the front perpendicular to the layers or diagonal gives significantly better results. Pressing from the top, either diagonal or parallel to an edge, interestingly leads to a different residual strain than pressing from front, with indentation on top always firstly leading to an expansion towards the indenter after the first few quasi-static load tests. To quantitatively evaluate these results, new measures are suggested which could be adopted by other groups working on shape-memory polymers.

Investigation of Grouted Coupler Connection Details for Accelerated Bridge Construction

2021 ◽  
pp. 036119812199939
Author(s):  
Brent Phares ◽  
Yoon-Si Lee ◽  
Travis K. Hosteng ◽  
Jim Nelson
Keyword(s):  
Crack Width ◽  
High Performance ◽  
Static Load ◽  
High Performance Concrete ◽  
Precast Concrete ◽  
Chloride Penetration ◽  
Load Testing ◽  
Test And Evaluation ◽  
Load Tests ◽  
Precast Elements

This paper presents a laboratory investigation on the performance of grouted rebar couplers with the connection details similar to those utilized on the precast concrete elements of the Keg Creek Bridge on US 6 in Iowa. The testing program consisted of a series of static load tests, a fatigue test, and evaluation of the chloride penetration resistance of laboratory specimens. The goal of this testing was to evaluate the ability of the grouted rebar couplers to develop flexural capacity at the joint between the precast elements as well as the durability of the connection. For structural load testing, seven full-scale specimens, each with #14 epoxy-coated rebars spliced by epoxy-coated grouted couplers, were fabricated and tested in three different loading cases: four-point bending, axial tension plus bending, and a cyclic test of the system in bending. The static load testing demonstrated that the applied axial load had a minimal effect on the formation of cracks and overall performance of the connection. When ultra-high performance concrete was used as a bedding grout, the initiation of crack was slightly delayed but no considerable improvement was observed in the magnitude of the crack width during loading or the crack closure on unloading. The results of the seventh specimen, tested in fatigue to 1 million cycles, showed little global displacement and crack width throughout the test, neither of which expanded measurably. No evidence of moisture or chloride penetration was detected at the grouted joint during the 6-month monitoring.

The healing power of well-being

2011 ◽  
Vol 23 (4) ◽  
pp. 145-155 ◽  
Author(s):  
Jobin Mathew ◽  
Cheramadathikudyl Scariya Paulose
Keyword(s):  
Brain Function ◽  
Premature Mortality ◽  
Well Being ◽  
Neuroendocrine System ◽  
Affective States ◽  
Functional Correlation ◽  
Enhanced Resistance ◽  
Healing Power ◽  
Negative Affective States ◽  
Physiological Benefits

Neuroendocrine system plays an important role in modulating our body functions and emotions. At the same time, emotions implicate a pivotal role in the regulation of brain function and neuroendocrine system. Negative affective states such as depression and stress are associated with premature mortality and increase the risk of various fatal diseases. It has been suggested that positive affective states are protective and improve our health and productiveness. Several potential mechanisms have been posited to account for these associations including improved health behaviour, direct physiological benefits, enhanced resistance and recovery from stress among individuals with high versus low positive emotional resources. This review summarises information concerning the neuronal and hormonal systems in mood, impact of negative and positive affective states on the level of cortisol, epinephrine, serotonin, dopamine and endorphins. The functional correlation of neuronal and hormonal systems in the development of diseases and their ability to enhance health-relevant biological processes are also evaluated.

Employing Visual Image Correlation for the Measurement of Compressive Strains for Arctic Onshore Pipelines

2013 ◽  
Author(s):  
Istemi F. Ozkan ◽  
Daryl J. Bandstra ◽  
Chris M. J. Timms ◽  
Arthur T. Zielinski
Keyword(s):  
Strain Gauge ◽  
Strain Distribution ◽  
Compressive Strain ◽  
Geometrical Nonlinearity ◽  
Large Diameter ◽  
Measurement Techniques ◽  
Visual Image ◽  
Image Correlation ◽  
The Arctic ◽  
Discontinuous Permafrost

The Arctic onshore environment contains regions of discontinuous permafrost, where pipes may be subject to displacement-controlled bending in addition to high hoop stresses due to the pressurized fluids being transported. Considering the displacement-controlled nature of the deformations, strain-based design methodologies have been developed for permafrost pipelines when they are subject to bending and tension, which limit the longitudinal compressive and tensile strains. The widely accepted methodology in the industry to obtain the compressive strain capacity of line pipes subject to bending is to conduct Finite Element Analysis, incorporating material and geometrical nonlinearity calibrated against benchmark full-scale tests (bend tests) [1,2]. During these tests, compressive strains can be measured by various methods. The seemingly obvious choice is to apply strain gauges along the compression face of the specimen with respect to bending (intrados). This method will provide reasonable results until the compressive strain pattern begins to vary due to the initiation of buckle formation, which typically occurs shortly after yield. In order to measure average compressive strain beyond yield and up to buckling, the method used by C-FER Technologies (C-FER) involves using rotation measurement devices (inclinometers) to calculate the strain change between the most compressive and tensile fibres of the specimen (intrados and extrados, respectively) with respect to the bending direction. This value is then subtracted from the tensile strain gauge readings as measured by the strain gauge(s) located on the extrados of the specimen. The average compressive strain values derived from the inclinometer and extrados strain gauge measurements are based on the assumption that the plane sections remain plane. Recently, five large diameter pipes were bend-tested at C-FER’s testing facility in Edmonton, Alberta. In addition to the compressive strain measurement method used by C-FER described above (C-FER method), a visual image correlation (VIC) camera system was used to survey the strain distribution on the compressive face of the specimens. This paper gives a brief description of the test setup and instrumentation of this test program. The VIC camera setup and measurement technique are described and the overall strain distribution on the bending intrados as measured by the VIC cameras is presented. Strain measured by the VIC system is compared with gauge measurements at local points as well as the average compressive strain behaviour of the specimens obtained through the C-FER method described above. The results show that the VIC system can be a candidate to replace the conventional measurement techniques employed for compressive strain limit testing in support of strain-based design of arctic pipelines.

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