The Influence of Steel Fiber Tensile Strengths and Aspect Ratios on the Fracture Properties of High-Strength Concrete

Steel fiber embedded in concrete serves to reduce crack development and prevent crack growth at the macroscopic level of the concrete matrix. Steel fiber-reinforced concrete (SFRC) with high compressive concrete strength is affected primarily by the dimensions, shape, content, aspect ratio, and tensile strength of the embedded steel fiber. In this study, double-ended hook steel fiber was used in SFRC with a concrete compressive strength of 80 MPa. This fiber was used for the study variables with two aspect ratios (64, 80) and tensile strength values up to 1600 MPa. The flexural performance of the SFRC specimens was evaluated using crack mouth open displacement tests, and the test results were compared with code provisions. A modified reinforcement index was also used to quantify the flexural performance based on comparisons with fracture energy.

WILCOXON ANALYSIS TO COMPARE OPEN DISPLACEMENT LEVEL IN INDONESIA BEFORE AND AFTER IMPLEMENTED IN ASEAN ECONOMIC SOCIETY

The ASEAN Economic Society (Indonesian: Masyarakat Ekonomi ASEAN (MEA)) is beginning to be implemented by 2015. This means that by 2015 a single market is formed and a production-based entity is supported by a free flow of goods, services, investments, capital and skilled labor. Free flow of skilled labor can be interpreted that all ASEAN citizens can go in and out to find work without any obstacle from the intended country. One of the preparations of the Indonesian government in facing the MEA is to improve the quality of human resources through the Masterplan of Acceleration and Expansion of Indonesian Economic Development (Indonesian: Masterplan Percepatan dan Perluasan Pembangunan Ekonomi Indonesia (MP3EI)) 2011-2025. Application of MEA should be viewed as a positive thing that is opening opportunity for job seekers in Indonesia for career abroad. Given the widespread employment opportunities, the Unemployment Rate (Indonesian: Tingkat Pengangguran Terbuka (TPT)) in Indonesia is declining.Wilcoxon analysis is a non parametric statistical analysis used to compare two nominal data groups correlated. In this study, wilcoxon analysis was used to compare TPT in Indonesia before and after the MEA was applied. TPT data used is TPT data before applied by MEA and TPT data after applied by MEA. The results showed that there was no significant difference between mean TPT in Indonesia before MEA was applied with average TPT in Indonesia after MEA was applied.

Displacement Correlation Technique for Interface Crack by FEM

Interface crack is evaluated using modified quarter point crack tip displacement method. Quarter point elements around the crack tip were employed in the Finite Element (ABAQUS) analysis to determine the near crack tip grid point displacements. In this study, a technique is adopted in which the crack opening displacement of the near crack tip grid point is forced to satisfy a known constraint. The linear term in the distance around the crack tip is reduced to zero. The complex stress intensity factor for interface crack is determined using the quarter point and the displacement correlation technique. It is well observed that FEM produce a less reliable displacement approximation around interface crack tip. However, this report will show that the use of near crack tip open displacement as determined by the standard finite element method can be utilised to give satisfactory result for the interface stress intensity factors K1 and K2.

A Prediction of the Leakage Through Cracks for Leak Before Break

A code was developed in this study to predict the leakage of the leak before break (LBB). Various stagnation conditions were considered, including the subcooled water, the two-phase fluid and the overheated steam. Moreover, both the critical and noncritical flow was studied. The Henry-Fauske critical flow model was revised by a new phase transition point and the pressure drop due to friction and turns were modified. The code was verified by the comparison with the experimental data on the leakage of conventional pipes, artificial cracks and naturally occurring cracks, which shows a good agreement and this code has a higher precision than the existing codes. The influence of crack morphologies on LBB leakage was discussed, including the local roughness, the global roughness, the crack open displacement (COD) and the number of the corners. Besides, the dependence of the LBB leakage on stagnation enthalpy and back pressure was also investigated.

The Study of CTOD Test and Allowable Value

In order to determine the heavy plate structure have sufficient fracture toughness, based on BS7448 fracture toughness test experiment standard,the study of the typical bridge steel material were extended to CTOD( crack tip open displacement) fracture toughness test at 20 °C, The average CTOD value of base metal which was more than the allowable value of CTOD were obtained,so the structure can satisfy the design need .

Specimen's Short Fatigue Crack Fabrication Test for Q420qE

According to the BS7448 fracture toughness test standard, this paper conducted a CTOD(crack tip open displacement) fatigue crack precast test with the bridge steel and analysis the tests results, thus obtained the related conclusions. With the increase of thickness and strength of the steel plate, the security of fatigue performance and toughness of the plate is becoming more important for the structure. So the evaluation of fatigue performance is a very significant work for engineer. This dissertation through the text study the CTOD Specimens Fatigue Crack Prefabricated process of bridge steel and its characteristics, and its results will provide the important experimental basis and computation basis.

The Debond Fracture of Sandwich Plate with Corrugated Core Using Cohesive Zone Element

In this paper, flatwise tensile test (FWT) and modified double cantilever beam (DCB) experiment were conducted to investigated the debond fracture of sandwich plate with corrugated core. In the experiment, the crack always stays at the face/core interfacial. Tensile bond strength of face core can be given from the flatwise tensile test and we can get the mode I fracture toughness GIC from DCB tests. It is found that the trends of curves change greatly at the beginning, with the propagation of crack, load against open displacement curves change smoothly. In order to simulate the face/core failure of sandwich plate with corrugated core, the cohesive element model is used. Tensile strength and strain energy release rate measured by the experiments presented in this paper are used in as parameters for simulation of the debond fracture. By comparing with the experiment results, the model can express the face/core failure of sandwich plate with corrugated core validly.

Fracture Toughness Evaluation for Welded Joints of High Strength Steel Through CTOD Test

This paper presents the method and procedure of CTOD test which are used for the toughness evaluation for welded joints. Two types of high strength steel (E38 and E43) are chosen as the object of fracture toughness evaluation. The contents of CTOD test include three-point crack tip open displacement (CTOD) bending tests for base metal (BM) specimens, weld position (WP) specimens and heat-affected zone (HAZ) specimens of the high strength steel, considering different thickness of steel plate and different test temperature (−20°C and 20°C). The CTOD test can achieve the P-V curves of samples, and the CTOD values are calculated. On the basis of the above work, the results of toughness evaluation are obtained. Meanwhile, some factors which affect the toughness of high strength steel are discussed in this paper, such as thickness of steel plate and test temperature, and many valuable conclusions are achieved.

Exploration of Constants Independent of Material and Layup in Transverse Matrix Cracking of Cross-ply Laminate

Stiffness reduction caused by matrix crack in cross–ply laminates of CFRP, GFRP, KFRP can be predicted well by a shear–lag model assuming a constant of the crack open displacement index. Due to the existence of the saturation crack state (CDS), stiffness reduction has a low boundary, the minimum normalized longitudinal stiffness of the cracked plies is 0.3 instead of 0 used in current lamination theory on the behaviour prediction after FPF.