• Geomechanics and Engineering
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• v.27 no.5
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• pp.481-495
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• 2021

This article assesses and estimates the progressive failure mechanism of complex pit-rest secondary toppling of slopes that are located within the vicinity of the Gas Flare Site of Refinery No. 4 in South Pars Special Zone (SPSZ), southwest Iran. The finite element numerical procedure based on the Shear Strength Reduction (SSR) technique has been employed for the stability analysis. In this regard, several step modelling stages that were conducted to evaluate the slope stability status revealed that the main instability was situated on the left-hand side (western) slope in the Flare Site. The toppling was related to the rock column-overburden system in relation to the overburden pressure on the rock columns which led to the progressive instability of the slope. This load transfer from the overburden has most probably led to the separation of the rock column and to its rotation downstream of the slope in the form of a complex pit-rest secondary toppling. According to the numerical modelling, it was determined that the Strength Reduction Factor (SRF) decreased substantially from 5.68 to less than 0.320 upon progressive failure. The estimated shear and normal stresses in the block columns ranged from 1.74 MPa to 8.46 MPa, and from 1.47 MPa to 16.8 MPa, respectively. In addition, the normal and shear displacements in the block columns ranged from 0.00609 m to 0.173 m and from 0.0109 m to 0.793 m, respectively.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.6 s.58
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• pp.176-182
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• 2009

Other damage can occur due to the preexisting dull structure and installation of nonenvironmental-friendly concrete structure, lack of function for preventing coastal erosion. Increase of personal income and fast spread of the concept of waterfront casued the initiation of many project to improve aging coastal ports. However, none of environment-friendly structure has been developed and pre-existing solid block, igloo block, tunnel block are used commonly. In piers and lighter's wharf where the ships are mooring, resonance by the generation of a reflected wave caused by penetration wave in the port and port wave increases wave heights in the port and makes difficult to maintain the temperature, causes problems in mooring ships and cargo-working, and eventually increase the occurance of damages of the small ships by the collision. Therefore, development of new types of blcok is necessary. To apply Coastal Environments block developed for this reason, it requires allowable bearing capacity evaluation of shear key. For this study, we made test specimen for connecting part of C.E. Block, and conducted friction test of boundary surface. Data obtained by the experiment was analyzed by finite element analysis and assessed the coefficient of friction between C.E. Block and boundary surface.

• The Journal of Advanced Prosthodontics
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• v.11 no.2
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• pp.95-104
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• 2019

PURPOSE. To evaluate the effect of surface treatments and repair materials on the shear bond strength and to measure the fracture toughness of CAD/CAM provisional restoration materials. MATERIALS AND METHODS. Four CAD/CAM (3D printing: Nextdent C&B and ZMD-1000B Temporary, CAD/CAM resin block: Yamahachi PMMA disk and Huge PMMA block) and four conventional (monometacrylate: Jet and Alike, dimetacrylate: Luxatemp and Protemp 4) materials were selected to fabricate disk-shaped specimens and divided into six groups according to surface treatment (n=10). CAD/CAM materials were repaired with Jet or Luxatemp, while conventional materials were repaired with their own materials. The shear bond strength was measured by using universal testing machine. Ten rectangular column-shaped specimens for each material were fabricated to measure the fracture toughness by single edge v notched beam technique. Statistical analysis was performed by one-way ANOVA. RESULTS. The highest shear bond strength of CAD/CAM materials was achieved by SiC paper + sandblasting. It was also accomplished when repairing 3D printing materials with Luxatemp, and repairing CAD/CAM resin blocks with Jet. Yamahachi PMMA disk showed the highest fracture toughness. Nextdent C&B showed the lowest fracture toughness value but no statistically significant difference from Alike and Luxatemp (P>.05). CONCLUSION. In order to successfully repair the CAD/CAM provisional restoration, mechanical surface treatment and appropriate repair material according to the CAD/CAM material type should be selected. The CAD/CAM provisional materials have proper mechanical properties for clinical use as compared to conventional materials.

• Computers and Concrete
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• v.17 no.6
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• pp.723-737
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• 2016

In this paper an approach was described for determination of direction of sliding block in rock slopes containing planar non-persistent open joints. For this study, several gypsum blocks containing planar non-persistent open joints with dimensions of $15{\times}15{\times}15cm$ were build. The rock bridges occupy 45, 90 and $135cm^2$ of total shear surface ($225cm^2$), and their configuration in shear plane were different. From each model, two similar blocks were prepared and were subjected to shearing under normal stresses of 3.33 and $7.77kg/cm^{-2}$. Based on the change in the configuration of rock-bridges, a factor called the Effective Joint Coefficient (EJC) was formulated, that is the ratio of the effective joint surface that is in front of the rock-bridge and the total shear surface. In general, the failure pattern is influenced by the EJC while shear strength is closely related to the failure pattern. It is observed that the propagation of wing tensile cracks or shear cracks depends on the EJC and the coalescence of wing cracks or shear cracks dominates the eventual failure pattern and determines the peak shear load of the rock specimens. So the EJC is a key factor to determine the sliding direction in rock slopes containing planar non-persistent open joints.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.639-646
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• 2000

It is important to estimate the mechanical properties of clay since it is directly related to the design and the construction of geotechnical structures. Site exploration, which is composed of boring, sampling, in-situ, or laboratory tests, is preformed to estimate the mechanical properties. However, mechanical properties of clay measured from laboratory test may be different from in-situ properties due to disturbances occurred during sampling, transportation, storage, and trimming. In this study, the degree of disturbance according to sampling method was estimated with the test results of CK/sub o/U triaxial compression test on Yangsan clay. The soil samples were obtained by three types of sampling method, j.e., 76mm-tube sampler, 76mm-piston sampler, and block sampler. In order to evaluate the quality of samples, volumetric strain, undrained shear strength, secant Young's modulus, and pore pressure coefficient at peak measured from each sample were compared with one another. From the test results, it was observed that mechanical properties of the block and piston samples were more reliable than those of tube samples. But it was observed that the water content of piston was similar to that of tube samples at given depths while the water content of block samples was 14.3∼15.8% smaller than that of piston and tube samples. In addition to the evaluation of the quality of samples, relationship between c/sub u// σ/sub vc/'and OCR was established from the results of the CK/sub o/U triaxial compression tests, which were carried out using SHANSEP method. And also undrained shear strength was analyzed using the in-situ test data such as Cone Penetration Test(CPT), Dilatometer Test(DMT), and Field Vane Test(FVT) and was compared with that evaluated from CK/sub o/U triaxial compression test.

• Advances in concrete construction
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• v.2 no.1
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• pp.57-75
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• 2014

This paper presents an analysis of the results of an experimental program on the performance of a novel configuration of a hybrid FRP-concrete beam. The beam section consists of a GFRP pultruded profile, a CFRP laminate, and a concrete block all wrapped up using filament winding. It was found that the thickness of the concrete block and the confinement by the filament-wound wrapping had a profound effect on the energy dissipation behaviour of the beam. Using a shear punching model, and comparing the predicted results with the experimental ones, it was found that beyond a given value of the concrete block thickness, the deformational behaviour of the beam shifts from brittle to ductile. It was also found that the filament-wound wrap had many benefits such as providing a composite action between the concrete block and the GFRP box, improving the stiffness of the beam, and most importantly, enhancing the load carrying ability through induced confinement of the concrete.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.325-332
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• 2003

In general, soil characteristics are estimated through the sample gathered by field boring without considering sample disturbance. However, soil characteristics must be changed by the degree of sample disturbance. Therefore it be need to estimate the soil characteristic considering sample disturbance which can be occurred by the change of stress condition, sampling technique and handling method. On this study, we analyzed the sample disturbance by using the methods of volume change, residual effective stress, elastic modulus and the curve of consolidation tests. In order to estimate the relationship between sample disturbance and soil characteristics, we used the piston sample and the block sample. As the results, it should be considered in design that the disturbance of the block sample, which affects the strength and compression properties of clay, is smaller than the disturbance of piston sample.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1991.04a
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• pp.84-90
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• 1991

Underground structures usually consist of rock masses or concretes which can be cracked or have cracks. This study aims to develop an analysis program which can deal with the effect of discontinuous behavior due to those cracks using the block theory. It is assumed that rock masses form blocks along the discontinuity lines, and deformation within the block is relatively small. The behavior of discontinuity plane of the structures is divided into sliding along the discontinuity plane. separation of discontinuity by tensile force, and degradation of asperity angle of discontinuity plane by external force with sliding of rock Basses. These behaviors are implemented using constitutive relation and relevent load-displacement relation defined through normal and shear stiffnesses. Time varying displacements and block velocities are calculated by explicit time stepping algorithm. The effect of rock supports including rockbolts is also considered, and the tending effects which occurs in relatively thin lining is also considered.

• Earthquakes and Structures
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• v.19 no.6
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• pp.411-425
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• 2020

Unreinforced masonry (URM) walls present low shear strength and are prone to brittle failure when subjected to inplane seismic overloads. This paper discusses the shear strengthening of URM walls with Textile Reinforced Mortar (TRM) jackets. The available literature is thoroughly reviewed and an extended database is developed including available brick, concrete and stone URM walls retrofitted and subjected to shear tests to assess their strength. Further, the experimental results of the database are compared against the available shear strength design models from ACI 549.4R-13, CNR DT 215 2018, CNR DT 200 R1/2013, Eurocode 6 and Eurocode 8 guidelines as well as Triantafillou and Antonopoulos 2000, Triantafillou 1998, Triantafillou 2016. The performance of the available models is investigated and the prediction average absolute error (AAE) is as high as 40%. A new model is proposed that takes into account the additional contribution of the reinforcing mortar layer of the TRM jacket that is usually neglected. Further, the approach identifies the plethora of different block materials, joint mortars and TRM mortars and grids and introduces rational calibration of their variable contributions on the shear strength. The proposed model provides more accurate shear strength predictions than the existing models for all different types of the URM substrates, with a low AAE equal to 22.95%.

• Applied Microscopy
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• v.45 no.2
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• pp.52-57
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• 2015

Bulk metallic glass (BMG) shows higth strength, high elastic limit, corrosion resistance and good wear resistance and soft magnetic properties and has been considering as a candidate for new structural materials. But they show limited macroscopic plasticity and lack of tensile ductility due to highly localized shear deformation, which should be solved for real structural application. In this paper researches on the enhancement of plasticity of BMG were reviewed briefly. Introducing heterogeneous structure in glass is effective to induce more shear transformation zones (STZs) active for multiple shear band initiation and also to block the propagating shear band. Several methods such as BMG alloy design for high Poisson's ratio, addition of alloying element having positive heat of mixing, pre-straining BMG and variety of BMG composites have been developed for homogenous distribution of locally weak region, where local strain can be initiated. Therefore enhancement of plasticity of BMG is normally accompanied with some penalty of strength loss.