• Computers and Concrete
• /
• v.26 no.6
• /
• pp.565-576
• /
• 2020

Experimental and discrete element methods were used to investigate the effects of angle of Y shape non-persistent joint on the tensile behaviour of joint's bridge area under brazilian test. concrete samples with diameter of 100 mm and thikness of 40 mm were prepared. Within the specimen, two Y shape non-persistent notches were provided. The large notch lengths were 6 cm, 4 cm and 2 cm. the small notch lengths were 3 cm, 2 cm and 1 cm. The angle of larger notch related to horizontal axis was 0°, 30°, 60°, 90°. Totally, 12 different configuration systems were prepared for Y shape non-persistent joints. Also, 18 models with different Y shape non-persistent notch angle and notch length were prepared in numerical model. The large notch lengths were 6 cm, 4 cm and 2 cm. the small notch lengths were 3 cm, 2 cm and 1 cm. The angle of larger notch related to horizontal axis was 0, 30, 60, 90, 120 and 150. Tensile strength of model materil was 1 MPa. The axial load was applied to the model by rate of 0.02 mm/sec. This testing showed that the failure process was mostly governed by the Y shape non-persistent joint angle and joint length. The tensile strengths of the specimens were related to the fracture pattern and failure mechanism of the discontinuities. It was shown that the tensile behaviour of discontinuities is related to the number of the induced tensile cracks which are increased by increasing the joint length and joint angle. The minimum tensile strength occurs when the angle of larger joint related to horizontal axis was 60°. Also, the maximum compressive strength occurs when the angle of larger joint related to horizontal axis was 90°. The tensile strength was decreased by increasing the notch length. The failure pattern and failure strength are similar in both methods i.e. the experimental testing and the numerical simulation methods.

• Computers and Concrete
• /
• v.27 no.2
• /
• pp.99-109
• /
• 2021

Experimental and discrete element methods were used to investigate the effects of echelon non-persistent joint on the failure behaviour of joint's bridge area under uniaxial compressive test. Concrete samples with dimension of 150 mm×100 mm×50 mm were prepared. Uniaxial compressive strength and tensile strength of concrete were 14 MPa and 1MPa, respectivly. Within the specimen, three echelon non-persistent notches were provided. These joints were distributed on the three diagonal plane. the angle of diagonal plane related to horizontal axis were 15°, 30° and 45°. The angle of joints related to diagonal plane were 30°, 45°, 60°. Totally, 9 different configuration systems were prepared for non-persistent joint. In these configurations, the length of joints were taken as 2 cm. Similar to those for joints configuration systems in the experimental tests, 9 models with different echelon non-persistent joint were prepared in numerical model. The axial load was applied to the model by rate of 0.05 mm/min. the results show that the failure process was mostly governed by both of the non-persistent joint angle and diagonal plane angle. The compressive strengths of the specimens were related to the fracture pattern and failure mechanism of the discontinuities. It was shown that the shear behaviour of discontinuities is related to the number of the induced tensile cracks which are increased by increasing the joint angle. The strength of samples increase by increasing both of the joint angle and diagonal plane angle. The failure pattern and failure strength are similar in both methods i.e. the experimental testing and the numerical simulation methods.

• Computers and Concrete
• /
• v.29 no.1
• /
• pp.31-45
• /
• 2022

Experimental and numerical simulation were used to investigate the effects of angle and number of T shape non-persistent crack on the shear behaviour of crack's bridge area under uniaxial compressive test. concrete samples with dimension of 150 mm×150 mm×40 mm were prepared. Within the specimen, T shape non-persistent notches were provided. 16 different configuration systems were prepared for T shape non-persistent crack based on two and three cracks. In these configurations, the length of cracks were taken as 4 cm and 2 cm based on the cracks configuration systems. The angle of larger crack related to horizontal axis was 0°, 30°, 60° and 90°. Similar to cracks configuration systems in the experimental tests, 28 models with different T shape non-persistent crack angle were prepared in numerical model. The length of cracks were taken as 4 cm and 2 cm based on the cracks configuration systems. The angle of larger crack related to horizontal axis was 0°, 15°, 30°, 45°, 60°, 75° and 90°. Tensile strength of concrete was 1 MPa. The axial load was applied to the model. Displacement loading rate was controlled to 0.005 mm/s. Results indicated that the failure process was significantly controled by the T shape non-persistent crack angle and crack number. The compressive strengths of the specimens were related to the fracture pattern and failure mechanism of the discontinuities. Furthermore, it was shown that the compressive behaviour of discontinuities is related to the number of the induced tensile cracks which are increased by increasing the crack number and crack angle. The strength of samples decreased by increasing the crack number. In addition, the failure pattern and failure strength are similar in both methods i.e. the experimental testing and the numerical simulation methods (PFC2D).

• Restorative Dentistry and Endodontics
• /
• v.32 no.2
• /
• pp.111-120
• /
• 2007

The purpose of this study is to evaluate the effects of surface treatment and composition of reinforcement material on fracture strength of fiber reinforced composite inlay bridges. The materials used for this study were I-beam, U-beam TESCERA ATL system and ONE STEP(Bisco, IL, USA). Two kinds of surface treatments were used; the silane and the sandblast. The specimens were divided into 11 groups through the composition of reinforcing materials and the surface treatments. On the dentiform, supposing the missing of Maxillary second pre-molar and indirect composite inlay bridge cavities on adjacent first pre-molar disto-occlusal cavity, first molar mesio-occlusal cavity was prepared with conventional high-speed inlay bur. The reinforcing materials were placed on the proximal box space and build up the composite inlay bridge consequently. After the curing, specimen was set on the testing die with ZPC. Flexural force was applied with universal testing machine (EZ-tester; Shimadzu, Japan). at a cross-head speed of 1 mm/min until initial crack occurred. The data was analyzed using one-way ANOVA/Scheffes post-hoc test at 95% significance level. Groups using I-beam showed the highest fracture strengths (p<0.05) and there were no significant differences between each surface treatment (p>0.05) Most of the specimens in groups that used reinforcing material showed delamination. 1. The use of I-beam represented highest fracture strengths (p<0.05) 2. In groups only using silane as a surface treatment showed highest fracture strength, but there were no significant differences between other surface treatments (p>0.05). 3. The reinforcing materials affect the fracture strength and pattern of composites inlay bridge. 4 The holes at the U-beam did not increase the fracture strength of composites inlay bridge.

• Journal of IKEEE
• /
• v.13 no.2
• /
• pp.101-107
• /
• 2009

Growth in the VLSI process and design technology is resulting into a continuous increase in the number of IPs on a chip to form a system. Because of many IPs on a single chip, efficient communication between IPs is essential. We propose a dynamically reconfigurable 3-layer bus structure which can adapt to the pattern of data transmission to achieve an efficient data communication between various IPs. The proposed 3-layer bus can be reconfigured to multi-single bus mode, and single-multi bus mode, thus providing the benefits of both single-bus and multi-bus modes. Experimental results show that the flexibility of the proposed bus structure can reduce data transmission time compared to the conventional fixed bus structure. We incorporated the proposed bus structure in a JPEG system and verified that the proposed structure achieved an average of 22% improvement in time over the conventional fixed bus structure.

• Steel and Composite Structures
• /
• v.18 no.4
• /
• pp.811-831
• /
• 2015

This paper focuses on the strengthening methods used for improving the compression behaviors of perforated box-section walls as provided in the anchorage zones of steel pylons. Rectangular plates containing double-row continuous elliptical holes are investigated by employing the boundary condition of simple supporting on four edges in the out-of-plane direction of plate. Two types of strengthening stiffeners, named flat stiffener (FS) and longitudinal stiffener (LS), are considered. Uniaxial compression tests are first conducted for 18 specimens, of which 5 are unstrengthened plates and 13 are strengthened plates. The mechanical behaviors such as stress concentration, out-of-plane deformation, failure pattern, and elasto-plastic ultimate strength are experimentally investigated. Finite element (FE) models are also developed to predict the ultimate strengths of plates with various dimensions. The results of FE analysis are validated by test data. The influences of non-dimensional parameters including plate aspect ratio, hole spacing, hole width, stiffener slenderness ratio, as well as stiffener thickness on the ultimate strengths are illustrated on the basis of numerous parametric studies. Comparison of strengthening efficiency shows that the continuous longitudinal stiffener is the best strengthening method for such perforated plates. The simplified formulas used for estimating the compression strengths of strengthened plates are finally proposed.

• Journal of Korean Society for Geospatial Information Science
• /
• v.5 no.2 s.10
• /
• pp.145-152
• /
• 1997

A coupling of two-dimensional model and GIS technique is applied to simulate sediment transport analysis. Accurate transformations are performed for the data which have various reduced scales. Basic maps are discretized the mesh of true scale for the finite element model by using the digital map and the Traverse Mercator coordinate. Under $200m^3/s$ flow rate condition, velocity vectors, depth contours, velocity contours and deposition contours are Presented for the 5km reach of midstream of Keum River from confluence of Ji-chun to Baekche Bridge. The simulation results of the study agree well with those of one-dimensional varied flow analysis and observed data. The flow and deposition pattern revealed a meandering characteristics of the river qualitatively.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.53 no.7
• /
• pp.452-461
• /
• 2004

A novel multilevel PWM inverter is presented for the use of stand-alone photovoltaic power generation system. In appearance, it consists of three full-bridge modules and three cascaded transformers; therefore, the configuration of the proposed multilevel PW inverter is equal to that of a prior 11-level PWM inverter. Only the turn-ratio of a transformer and its corresponding switching function are different from each other. Owing to these differences, the proposed 19-level PWM inverter has two promising advantages. First, output voltage levels increase almost twofold. Consequently, it can generate more sinusoidal output voltage waveform. Second, due to a revised switching pattern, it lightens power imposed on the transformer, which is used for compensating output voltages with chopped pulses between steps. The validity of the proposed inverter system is verified by computer-aided simulations and experimental results based on a 1 ［kW］ prototype. The performance of the proposed 19-level PWM inverter is compared with the Prior 11-level PWM inverter and other counterparts.

• Smart Structures and Systems
• /
• v.15 no.3
• /
• pp.699-715
• /
• 2015

A modal parameter based damage sensitive feature (DSF) is defined to mimic the relative change in any diagonal element of the stiffness matrix of a model of a structure. The damage assessment is performed in a statistical pattern recognition framework using empirical complementary cumulative distribution functions (ECCDFs) of the DSFs extracted from measured operational vibration response data. Methods are discussed to perform probabilistic structural health assessment with respect to the following questions: (a) "Is there a change in the current state of the structure compared to the baseline state?", (b) "Does the change indicate a localized stiffness reduction or increase?", with the latter representing a situation of retrofitting operations, and (c) "What is the severity of the change in a probabilistic sense?". To identify a range of normal structural variations due to environmental and operational conditions, lower and upper bound ECCDFs are used to define the baseline structural state. Such an approach attempts to decouple "non-damage" related variations from damage induced changes, and account for the unknown environmental/operational conditions of the current state. The damage assessment procedure is discussed using numerical simulations of ambient vibration testing of a bridge deck system, as well as shake table experimental data from a 4-story steel frame.

• Structural Engineering and Mechanics
• /
• v.41 no.1
• /
• pp.43-65
• /
• 2012

The primary objective of this study was to identify concrete contribution to the initial shear strength of reinforced concrete (RC) hollow columns under lateral loading. Seven large-scale RC rectangular hollow column specimens were tested under monotonic or cyclic lateral loads. The most important design parameter was column length-to-depth aspect ratio ranging between 1.5 and 3.0, and the other test variables included web area ratio, hollow section ratio, and loading history. The tests showed that the initial shear strength reduced in a linear pattern as the column aspect ratio increased, and one specimen tested under cyclic loading achieved approximately 83% of the shear strength of the companion specimen under monotonic loading. Also, several pioneering shear models proposed around the world, all of which were mainly based on tests for columns with solid sections, were reviewed and compared with the test results of this study, for their possible applications to columns with hollow sections. After all, an empirical equation was proposed for concrete contribution to the initial shear strength of RC hollow columns based on fundamental mechanics and the test results.