Applicability of Modified University of Illinois at Urbana–Champaign Model for Unbound Aggregate Material with Different Water Content

This paper proposes a modified University of Illinois at Urbana–Champaign (UIUC) model to predict permanent deformation behavior of unbound aggregate materials. Most existing models relate permanent deformation to resilient properties, whereas the UIUC model treats shear strength as a critical factor in permanent deformation behavior. Three types of test, monotonic shearing test, cyclic axial loading test, and cyclic axial and shear loading test, were conducted by multi-ring shear apparatus on two kinds of parallel grading aggregate materials, natural crusher-run and recycled crusher-run obtained from demolished concrete structure. Test results demonstrate that shear strength is the core factor in permanent deformation behavior, compared with resilient properties, and principal stress axis rotation (PSAR) greatly increases the permanent deformation. By considering the effect of PSAR on permanent deformation, a new parameter, ( Rs)ave, is added to the conventional UIUC model to modify it. Regression analysis results verify that the modified UIUC model has good applicability for predicting permanent deformation of aggregates with different water contents and stress states, and with and without PSAR. The modified UIUC model builds a relation between test results with and without PSAR. A simple framework is also proposed for predicting permanent deformation in flexible pavement structures based on the modified UIUC model.

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A study on the bond behavior of different FRCM systems

MATEC Web of Conferences ◽

10.1051/matecconf/201819909003 ◽

2018 ◽

Vol 199 ◽

pp. 09003

Author(s):

Adel Younis ◽

Usama Ebead

Keyword(s):

Single Layer ◽

Concrete Surface ◽

Shear Loading ◽

Test Results ◽

Loading Test ◽

Brittle Behavior ◽

Shear Connection ◽

Double Shear ◽

Modes Of Failure ◽

Bond Tests

Fabric-reinforced cementitous matrix (FRCM) composites are usually applied on the concrete surface for the purpose of strengthening reinforced concrete structures. However, the efficiency of FRCM strengthening is notably affected by the bond between the FRCM system and concrete substrate. In view of that, the current paper presents the results of a preliminary experimental study carried out to investigate the bond characteristics between FRCM composites and concrete. Six number of specimens, each consisted of a 150-mm concrete cube with a double-shear connection to an FRCM system, were subjected to direct-shear loading test. The parameters investigated include (a) FRCM material (carbon, polyparaphenylene benzobisoxazole (PBO), and glass); and (b) Bond length (75 mm or 100 mm). The FRCM systems typically included a single layer of fabric with the associated mortar, and the bond width was uniformly taken as 100 mm. The test results revealed that the bond capacity is enhanced with an increase in the FRCM bonded length. The PBO-FRCM showed the highest bond capacity between FRCM composite and concrete substrate among the three systems. The modes of failure observed in carbon-, PBO-, and glass-FRCM bond tests are fabric delamination, FRCM mortar/concrete debonding, and fabric rapture, respectively. The PBOand glass-FRCM bond tests thus exhibited a more brittle behavior at failure than that of the carbon-FRCM counterpart.

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A Numerical Model of Lead Material and Its Applicability to Simulation of Isolation Devices

Seismic Engineering ◽

10.1115/pvp2003-2102 ◽

2003 ◽

Author(s):

Akihiro Matsuda

Keyword(s):

Mechanical Properties ◽

Numerical Model ◽

Large Strain ◽

Tensile Loading ◽

Cyclic Stress ◽

Shear Loading ◽

Test Results ◽

Loading Test ◽

Initial Yield Stress ◽

Damping Material

This paper proposes a new numerical model of lead material to predict mechanical properties of isolation and vibration control devices using lead as damping material. Shear and tensile loading tests of lead were carried out to make the numerical model. Shear loading test specimen were constructed from a circumferential lead part welded at the top and bottom to steel flanges. Cyclic stress-strain relations in large strain region were obtained from shear loading test results. The elastic constants and the initial yield stress were given from tensile loading test results. Therefore a numerical model was made using both shear loading and tensile loading test results. Mechanical properties of lead dampers and isolated rubber bearings were simulated using the proposed numerical model via finite element method to show applicability of the model.

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Aggregate Morphology Affecting Strength and Permanent Deformation Behavior of Unbound Aggregate Materials

Journal of Materials in Civil Engineering ◽

10.1061/(asce)0899-1561(2008)20:9(617) ◽

2008 ◽

Vol 20 (9) ◽

pp. 617-627 ◽

Cited By ~ 64

Author(s):

Erol Tutumluer ◽

Tongyan Pan

Keyword(s):

Deformation Behavior ◽

Permanent Deformation ◽

Aggregate Morphology ◽

Unbound Aggregate

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Shear Retrofitting Effect of RC Beams Damaged by Corrosion of Stirrup Strengthened with CFS

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.348-349.441 ◽

2007 ◽

Vol 348-349 ◽

pp. 441-444

Author(s):

Sung Ho Tae ◽

Han Seung Lee ◽

Tae Soo Kim

Keyword(s):

Shear Stress ◽

Shear Strength ◽

Reinforced Concrete ◽

Carbon Fiber ◽

Shear Loading ◽

Rc Beams ◽

Loading Test ◽

Shear Strengthening ◽

Anchorage Length

In this study, an Ohno's anti-symmetric shear loading test was conducted after strengthening reinforced concrete (RC) beams damaged by corrosion of stirrup, with carbon fiber sheets (CFS) with a view to reviewing the effect of CFS on shear strengthening. As a result, it was found that CFS like stirrups could take shear stress, and that shear strength could be increased by using more CFS for reinforcement. It was also revealed that shear strength could be calculated by an existing evaluation equation by properly evaluating the effect of CFS on shear strengthening, based on the quantity of reinforcing CFS, ways of fixing the sheets and anchorage length as the effect on shear strengthening varied depending on the fixing method while sheet anchorage increased deformability.

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Uplift Behavior of Belled Short Piles in Weathered Sandstone

Mathematical Problems in Engineering ◽

10.1155/2018/8614172 ◽

2018 ◽

Vol 2018 ◽

pp. 1-8

Author(s):

Bai Yang ◽

Jianlin Ma ◽

Wenlong Chen ◽

Yanxin Yang

Keyword(s):

Shear Strength ◽

Bearing Capacity ◽

Calculation Model ◽

Uplift Capacity ◽

Test Results ◽

Loading Test ◽

Pull Out ◽

Initial Stage ◽

Uplift Load ◽

Double Circuit Line

Field pull out test results of 500 kV double-circuit line of Luping-Fule are presented in this paper to investigate the uplift bearing behavior of rock-socketed belled short piles. A calculation model of rock-socketed belled short pile has been proposed. During the initial stage of loading test, uplift load is shared by even section and bell of the pile, and the bell continues to bear uplift load after the lateral resistance of even section pile reaches the limit. A different performance has been found on the case of long belled pile. At the ultimate state, the uplift resistance provided by bell accounts for about 54.9% and 34.7% of the total uplift capacity for the 6.0 m long and 7.0 m long piles, respectively. Increasing pile length has been found to noticeably increase the ultimate uplift bearing capacity, while it has less effect on the displacement of pile top. The uplift capacity of even section pile is associated with the shear strength of rock mass around the pile, and the test results demonstrate that the ultimate resistance can be equal to the shear strength. The calculation method proposed in this paper is proven to be able to accurately predict the ultimate uplift bearing capacity of the rock-socketed belled short piles.

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Influence of initial water content on unsaturated shear strength of compacted GaoMiaoZi (GMZ) bentonite

Canadian Geotechnical Journal ◽

10.1139/cgj-2019-0431 ◽

2021 ◽

Vol 58 (1) ◽

pp. 142-146

Author(s):

N.F. Zhao ◽

W.M. Ye ◽

Q. Wang ◽

B. Chen ◽

Y.-J. Cui

Keyword(s):

Shear Strength ◽

Water Content ◽

Critical State ◽

Initial Water Content ◽

Gmz Bentonite ◽

Test Results ◽

Loading Test ◽

Initial Water ◽

State Stress ◽

Water Contents

This paper presents an experimental study on the influence of initial water content on unsaturated shear strength of compacted bentonite. Isotropic loading and triaxial shear tests were conducted on compacted GaoMiaoZi (GMZ) bentonite specimens with different initial water contents. Isotropic loading test and triaxial shear test results show that the compression index increases and yield stress decreases with increasing water content, while the swelling index stays constant. For normally consolidated and lightly overconsolidated bentonite, unsaturated shear strength can be described by the critical state line. For highly overconsolidated bentonite, unsaturated shear strength can be described by the Hvorslev surface. The critical state line and Hvorslev surface are found to be linear for the specimens with different water contents. The critical state stress ratio and the Hvorslev surface parameters are found to decrease with an increase in water content of the bentonite studied.

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Validated Model for Predicting Field Performance of Aggregate Base Courses

Transportation Research Record Journal of the Transportation Research Board ◽

10.3141/1837-05 ◽

2003 ◽

Vol 1837 (1) ◽

pp. 41-49 ◽

Cited By ~ 36

Author(s):

Erol Tutumluer ◽

Dallas N. Little ◽

Sung-Hee Kim

Keyword(s):

Permanent Deformation ◽

Field Performance ◽

Stress Sensitivity ◽

Triaxial Tests ◽

Validation Data ◽

Finite Element Program ◽

University Of Illinois ◽

Aggregate Base ◽

The University ◽

Unbound Aggregate

The International Center for Aggregates Research Project 502 focused on pavement layers of unbound aggregate proper representation in mechanistic pavement models. The research team developed models for resilient and permanent deformation behavior from the results of triaxial tests conducted at the Texas Transportation Institute and the University of Illinois. The studies indicate that the unbound aggregate base (UAB) material should be modeled as nonlinear and cross-anisotropic to account for stress sensitivity and the significant differences between vertical and horizontal moduli and Poisson’s ratios. Field validation data were collected from a full-scale pavement test study conducted at Georgia Tech. The validation of the anisotropic modeling approach was accomplished by analyzing conventional flexible pavement test sections using the GT-PAVE finite element program to predict responses to load in the UAB layer and comparing these predicted responses to the measured values. Laboratory testing of the aggregate samples was conducted at the University of Illinois, and characterization models were developed for the stress-sensitive, cross-anisotropic aggregate behavior. With nonlinear anisotropic modeling of the UAB, the resilient behavior of pavement test sections was successfully predicted for a number of response variables. In addition, the stress-sensitive, cross-anisotropic representation of the base was shown to greatly reduce the horizontal tension computed in the granular base compared with a linear isotropic representation.

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Observation of secondary slip systems in tungsten bicrystals

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100112361 ◽

1984 ◽

Vol 42 ◽

pp. 478-479

Author(s):

J. R. Fekete ◽

R. Gibala

Keyword(s):

Stress Field ◽

Grain Boundaries ◽

Deformation Behavior ◽

Stress Axis ◽

Polycrystalline Materials ◽

Slip Systems ◽

Metallic Materials ◽

Twist Boundary ◽

Secondary Slip ◽

Plane Normal

The deformation behavior of metallic materials is modified by the presence of grain boundaries. When polycrystalline materials are deformed, additional stresses over and above those externally imposed on the material are induced. These stresses result from the constraint of the grain boundaries on the deformation of incompatible grains. This incompatibility can be elastic or plastic in nature. One of the mechanisms by which these stresses can be relieved is the activation of secondary slip systems. Secondary slip systems have been shown to relieve elastic and plastic compatibility stresses. The deformation of tungsten bicrystals is interesting, due to the elastic isotropy of the material, which implies that the entire compatibility stress field will exist due to plastic incompatibility. The work described here shows TEM observations of the activation of secondary slip in tungsten bicrystals with a [110] twist boundary oriented with the plane normal parallel to the stress axis.

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