• Proceedings of the Korea Concrete Institute Conference
• /
• 2000.04a
• /
• pp.533-538
• /
• 2000

In R.C. flat slab system, a brittle punching failure is a very fatal problem. But there is no generally well-defined answer to the problem and there are wide differences in current practical design codes. therefore, in this study, the factors affecting to punching failure mechanism have been studied to find out the punching shear behavior in R.C. flat slabs by comparing other investigations and practical design codes. Therefore, In this study, the factors affecting to punching failure mechanism have been studied to find out the punching shear behavior in R.C. flat slabs by comparing other investigations and practical design codes. The conclusions in this study are summarized as follows; 1) The factors affecting to punching shear are concrete strength ($f_\alpha$), ratio of column side length to slab depth (c/d), ratio of distance from column center to radial contraflexure (l/d), yield strength of steel ($f_y$), flexural reinforcement ratio ($\rho$) and size effects. 2) It is shown that th use of $\surd{f_{ck}}$in applying($f_\alpha$ to punching shear strength estimation may be more sensitive in high concrete strength. 3) The effects of l/d, ($f_y$, size are no clear in the punching failure mechanism, so in the future, it should be investigated with the effects of various composed load.

• Structural Engineering and Mechanics
• /
• v.38 no.6
• /
• pp.803-823
• /
• 2011

In this paper, the three dimensional Parallel Realistic Failure Process Analysis ($RFPA^{3D}$-Parallel) code based on micromechanical model is employed to investigate the bonding behavior in FRP sheet bonded to concrete in single shear test. In the model, the heterogeneity of brittle disordered material at a meso-scale was taken into consideration in order to realistically demonstrate the mechanical characteristics of FRP-to-concrete. Modified Mohr-coulomb strength criterion with tension cut-off, where a stressed element can damage in shear or in tension, was adopted and a stiffness degradation approach was used to simulate the initiation, propagation and growth of microcracks in the model. In addition, a Master-Slave parallel operation control technique was adopted to implement the parallel computation of a large numerical model. Parallel computational results of debonding of FRP-concrete visually reproduce the spatial and temporal debonding failure progression of microcracks in FRP sheet bonded to concrete, which agrees well with the existing testing results in laboratory. The numerical approach in this study provides a useful tool for enhancing our understanding of cracking and debonding failure process and mechanism of FRP-concrete and our ability to predict mechanical performance and reliability of these FRP sheet bonded to concrete structures.

• Journal of the Korean Society of Safety
• /
• v.25 no.6
• /
• pp.128-136
• /
• 2010

In according with concrete structural design standard, it is common designing flexure reinforcement concrete to induce tension failure. So reinforcing ratio is limited to inducing tension failure. And maximum reinforcing ratio is regulated to protecting concrete compression strength caused by over reinforced building. Minimum reinforcing ratio is also limited in designing standard to protecting brittle failure as extremely using less reinforcing bar. But in minimum reinforcing ratio it is extremely conservative or it is sometimes impossible to induce stable tension-failure because they are depending on yield failure and experienced method and concrete designing standard strength. Therefore the purpose of the present paper is to evaluate the flexural behavior of minimum steel ratio of reinforced concrete of beams and to propose the guide-line of equation of minimum steel ratio by performing static flexural test of 16 beams according to size effect, number of steel, yielding stress of steel, and concrete compressive strength which are presumed effective variables. From experimental results, the equation of minimum steel ratio was newly proposed considered size effect.

• Journal of the Korea Concrete Institute
• /
• v.19 no.5
• /
• pp.529-537
• /
• 2007

The purpose of this study is to discuss how strength and ductility of each system in low-rise reinforced concrete buildings composed of extremely brittle, shear and flexural failure lateral-load resisting systems have influence on seismic capacities of the overall system, which is based on nonlinear seismic response analyses of single-degree-of-freedom structural systems. In order to simulate the triple lateral-load resisting system, structures are idealized as a parallel combination of two modified origin-oriented hysteretic models and a degrading trilinear hysteretic model that fail primarily in extremely brittle, shear and flexure, respectively. Stiffness properties of three models are varied in terms of story shear coefficients, and structures are subjected to various ground motion components. By analyzing these systems, interaction curves of demand strengths of the triple system for various levels of ductility factors are finally derived for practical purposes. The result indicates that demand strength levels derived can be used as a basic information for seismic evaluation and design criteria of low-rise reinforced concrete buildings having the triple lateral-load resisting system.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2002.10a
• /
• pp.117-122
• /
• 2002

Flat Plate structures subjected to lateral load are susceptible to the brittle failure, therefore deformability of plate-column connections should be ensured to resist against earthquake. However, according to previous study, existing experiments overestimate the deformability of connections and current design provision do not accurately explains them. In the present study, parametric study using nonlinear finite element analysis was performed. Based on the numerical results, seismic design method considering the deformability of connections was developed.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1999.10a
• /
• pp.445-448
• /
• 1999

The minimum shear and torsional reinforcement provisions in ACI 318-95 are still empirical. This paper describes the derivation of a rational approach for minimum shear and torsional reinforcement in beams so as to preclude brittle failure in shear and torsion. This is ensured by specifying that the beam's ultimate capacity of shear and torsion should be greater than its cracking shear and torsion. The formula presented herein for computing minimum shear and torsional reinforcement shows the need for modification of current provision for the minimum shear and torsion reinforcement.

• Magazine of the Korea Concrete Institute
• /
• v.14 no.2
• /
• pp.37-44
• /
• 2002

콘크리트의 내화성능에 대한 다각적인 연구가 1970년대부터 원자로의 안정성 확보차원에서 진행되어 왔으며 특히 콘크리트의 취성파괴(brittle failure)등에 대한 연구가 많다. 콘크리트의 내화성이란 화재로부터 보호되고 고열환경에 견디는 재료적 특성 즉 화재온도 1,00$0^{\circ}C$ 정도의 고온을 30분에서 3시간 정도를 받은 경우 콘크리트 중에 매립된 철근 등 철강을 소정의 온도 이하고 유지하기 위한 피복 역할을 유지하면서 구조물의 큰 변형이나 붕괴 등을 막기 위한 소요 압축강도 및 영계수 등의 성능을 가지고 있는 성질을 말한다.(중략)

• Proceedings of the Korea Concrete Institute Conference
• /
• 1995.04a
• /
• pp.366-371
• /
• 1995

This paper is designed to bring to the attention of the reader the situation that may constitute a threat to the safety of RC structures designed and constructed in Korea. This threat stems from the inadequate rules of the acceptance strength control of concrete. As a result in some cases probability of brittle failure can be very high and reliability becomes very low. The paper substantiates the above statements. Further investigations aimed at finding the measures to remedy the situatuion are recommended.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.05a
• /
• pp.973-978
• /
• 2003

This paper describes the experimental study on seismic strengthening effect of circular bridge columns with poor lap-splice details using FRP(Fiber Reinforced Plastic) wrapping, The as-built column suffered brittle failure due to the deterioration of lap-spliced longitudinal reinforcement without developing its flexural capacity or any ductility, The strengthening columns using FRP wrapping showed significant improvement in seismic performance due to FRP's confinement effect.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1996.10a
• /
• pp.453-458
• /
• 1996

In reinforced concrete structure, it is very important to secure ductile performance of column because the columns become brittle failure and cause the collapse of an entire structure and the damage of human life. This study is intending to seek the quantity of transverse steels in square reinforced concrete columns which is derived from moment-curvature analysis of cross section about various arrangements of transverse steel and the ratio of axial force and to propose the design method to secure the sufficient ductile behavior subjected to complex loading.