Aplikasi Size Effect Law Pada Beton Marine dengan Pola Bukaan Tarik

AbstrakPengembangan infrastruktur di bidang maritim adalah salah satu strategi untuk mengembangkan perekonomian. Beton marine banyak digunakan sebagai material struktur pada pembangunan infrastruktur di bidang maritim tersebut. Beton marine harus menggunakan beton high performance concrete (HPC). Dengan berkembangnya teknologi beton HPC pengoptimalan efisiensi komponen struktur menjadi lebih signifikan.Pada perencanaan pelaksanaan pembangunan khususnya pada tahap analisa struktur, jarang sekali direncanakan kekuatan terhadap mekanika fraktur yang seharusnya juga didesain agar keruntuhan secara fraktur bisa diatasi. penelitian ini mengkaji aplikasi size effect law pada beton HPC pada balok dengan berbagai ukuran yang sudah ditentukan (small, medium dan high) untuk memperoleh nilai energy fraktur (Gf). Hasil penelitian ini dapat berkontribusi dalam penerapam metode untuk mendapatkan nilai parameter dari kinerja fraktur. selain itu, data parameter dapat digunakan dalam mengkalibrasi analisa numerik elemen struktur berbasis fraktur energi agar dapat dipastikan kinerja struktur yang sesungguhnya.Hasil pengujian menunjukkan energi fraktur pada benda uji set II (rasio takik terhadap tinggi sample = 1/6) lebih besar 8,4% dari benda uji set I (rasio takik terhadap tinggi sample = 1/3). Factor geometri dan kemiringan pada garis regresi (A) menurun selaras dengan menurunnya rasio takik. Dari angka keruntuhan nilai berada pada range 0,1 < < 10 yang menandakan material didesain harus dengan kriteria nonlinear fracture mechanic.Kata-kata Kunci: Beton marine, mekanika fraktur, size effect law, nonlinear fracture mechanics AbstractInfrastructure development in the maritime sector is one strategy for developing the economy. Marine concrete is widely used as a structural material in infrastructure development in the maritime sector. Marine concrete must use high performance concrete (HPC). With the development of HPC concrete technology, optimization of the efficiency of structural components has become more significant.In the construction implementation planning, especially at the structural analysis stage, it is rare to plan the strength of the fracture mechanics which should also be designed so that fracture collapse can be overcome. This study examines the application of size effect law on HPC concrete on beam of various predetermined sizes (small, medium and high) to obtain the fracture energy value (Gf). The results of this study can contribute to the application of the method to obtain parameter values of fracture performance. In addition, parameter data can be used in calibrating the numerical analysis of energy fracture based structural elements in order to ascertain the actual performance of the structure.The results showed that fracture energy in specimen set II (ratio of notches to depth = 1/6) was 8.4% greater than specimen set I (ratio of notches to sample height = 1/3). The geometric factor and slope of the regression line (A) decreased in line with the decreasing notch ratio. From the brittleness number, the value of β is in the range 0.1 <β <10 which indicates that the material should designed with nonlinear fracture mechanic criteria.Key words: marine concrete, fracture mechanics, size effect law, nonlinear fracture mechanics

Crack Propagation Modeling of Strengthening of RC Deep Beams With CFRP Plates

Fracture analysis of reinforced concrete deep beam strengthened with carbon fiber-reinforced polymer (CFRP) plates was carried out. The present research aims to find out whether the crack propagation in a strengthened deep beam follows linear elastic fracture mechanics (LEFM) theory or nonlinear fracture mechanics theory. To do so, a new energy release rate based on nonlinear fracture mechanics theory was formulated on the finite element method and the discrete cohesive zone model (DCZM) was developed in deep beams. To validate and compare with numerical models, three deep beams with rectangular cross-sections were tested. The code results based on nonlinear fracture mechanics models were compared with experimental results and ABAQUS results carried out based on LEFM. The predicted values of initial stiffness, yielding point and failure load, energy absorption, and compressive strain in the concrete obtained by the proposed model were very close to the experimental results. However, the ABAQUS software results have greater differences with the experimental results. For example, the predicted failure load for the shear-strengthened deep beam using the proposed model has only 6.3% differences compared to the experimental result. However, the predicted failure load using ABAQUS software based on LEFM has greater differences (25.1%) compared to the experimental result.

Kinetics of the multidirectionality of elastic-plastic fracture with allowance for anisotropy of the material properties

Survivability, service life and operational safety of the engineering structures are determined by their damage rate which is mainly regulated by the presence and development of the crack-like defects in the material. Kinetic dependences describing the development of multidirectional semi-elliptic surface cracks with allowance for the anisotropy of the material properties are proposed proceeding from experimental data and numerical solutions. The obtained results are required in studying kinematic problems in nonlinear mechanics of a continuous anisotropic medium. Refining parametric equations for elastoplastic deformation anisotropy are proposed. Functional dependences of the parameters of the kinetic diagrams of low-cycle fracture on the mechanical properties of the material are presented for a wide class of welded joints of austenite stainless cyclically stable steels (12Kh18N10T). The processes of developing inclined semi-elliptic surface cracks in the continuums of welded joints under non-linear boundary loading conditions are studied. We have carried out combined computational, experimental and numerical studies of the stress-strain state in the vicinity of the contour of stationary and growing surface semi-elliptic cracks randomly oriented in space under elastoplastic nominal cyclic loading taking into account the anisotropy of the material properties. The functional distribution of the inhomogeneity parameter of the mechanical properties of the material, which affects accumulation of the local plastic strains and direction of developing the elastoplastic fracture is obtained and presented in the form of the kinetic equation of nonlinear fracture mechanics. Comparison of the experimental results and numerical calculations of the stress-strain state along the contour of the cracks under study in nonlinear boundary loading conditions revealed a good agreement between the intensities of relative elastoplastic deformations at their surface points with allowance for the deformation anisotropy. Calculations of the elastoplastic fracture resistance of the critical elements of the equipment with allowance for considered factors of nonlinear fracture mechanics and heterogeneity of the properties can improve the accuracy of evaluation of their strength, service life and survivability.

CONNECTION BETWIN FRACTAL DIMENSION OF THE CONCRETE FRACTURE SURFACE AND MECHANICS OF DESTRUCTION CHARACTERISTICS

As it was found previously, the concrete fracture surface formed from tensile force is described by fractal geometry methods. It is shown thatthe fractal dimension value is related to the tensile stress gradient φ_i, to the aggregate size and, as shown earlier, does not depend on the strength of concrete. Moreover, the fractal dimension depends on the size of the sample only until its size reaches a value to which linear fracture mechanics is applicable. The stress intensity factor is related to the fractal dimension, and both characteristics are related to the aggregate size. A connection for the critical stress intensity factor K_Ic^f(l,φ_i) characterizing the crack resistance of the material in nonlinear fracture mechanics with the crack size l and the specimenis proposed. The stress intensity factor for a fractal crack K_Ic^f(l,φ_i) can be used to calculate structures using nonlinear fracture mechanics.

Beyond conventional nonlinear fracture mechanics in graphene nanoribbons

An atomic ERR concept considering atomic discreteness is proposed to describe fracture beyond the critical size for nonlinear fracture mechanics.

Nonlinear Fracture Mechanics Analysis Considering Material Inhomogeneity of Welded Joints

Professor Hiroshi Okada and his team from the Department of Mechanical Engineering, Faculty of Science and Technology, Tokyo University of Science, Japan, are engaged in the field of computational fracture mechanics. This is an area of computational engineering that refers to the creation of numerical methods to approximate the crack evolutions predicted by new classes of fracture mechanics models. For many years, it has been used to determine stress intensity factors and, more recently, has expanded into the simulation of crack nucleation and propagation. In their work, the researchers are proposing new methods for fracture mechanics analysis and solid mechanics analysis.