• Computers and Concrete
• /
• v.17 no.1
• /
• pp.87-106
• /
• 2016

This paper deals with the reliability analysis of design formulations derived for predicting the punching shear capacity of FRP-reinforced two-way slabs. Firstly, a new design code formulation was derived by means of gene expression programming. This formulation differs from the existing ones as the slab length (L) was introduced in the equation. Next, the proposed formulation was tested for its generalization capability by a parametric study. Then, the stochastic analyses of derived and existing formulations were performed by Monte Carlo simulation. Finally, the reliability analyses of these equations were carried out based on the results of stochastic analysis and the ultimate state function of ASCE-7 and ACI-318 (2011). The results indicate that the prediction performance of new formulation is significantly higher as compared to available design equations and its reliability index is within acceptable limits.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2000.04a
• /
• pp.357-362
• /
• 2000

This Paper presents dynamic analysis of underground R/C Subway Structure, subjected to seismic actions. Earthquakes brought serious damage to RC subway Structure. Foe studying the collapse mechanism of underground RC Subway, seismic of a subway station is simulated in using FEM program ASP2000 of two-dimension based on the path dependent RC elastic model, soil foundation and interfacial models. The shear failure of intermediate vertical columns is founds to be the major cause of the structural collapse. According to FEM simulation of the failure mechanism, it is considered that the RC column would lose axial load carrying capacity after the occurrence of the localized diagonal shear cracks , and sudden failure of the outer frame would be followed. Specially, the shear stress in the middle slab reaches maximum shear capacity. So, the Structure would fail in the middle slab as a result of erasing the vertical ground motion computation.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2000.04a
• /
• pp.605-610
• /
• 2000

The concrete slab on the foundation may have curling and warping deformations due to temperature gradient of its section. These deformations may change the support conditions of concrete slabs, and cause higher level of stresses tan expected. In this study, partial support conditions de to several temperature gradients are evaluated using FE analysis. Expecially, 3D FE model is adopted to evaluate the partial contact between the slab and the base which is hard to be simulated in 2D FE models. The discrepancies of analysis results increase at high temperature gradients. And it is concluded that 3D FE model can be used to simulate real support and temperature conditions.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2000.11a
• /
• pp.220-223
• /
• 2000

A method of calculating the natural frequency corresponding to the modes of vibration of beams and tower structures, with irregular cross sections and with arbitrary boundary conditions was developed and reported by Kim, D. H. in 1974. In this paper, the result of application of this method to the three span continuous reinforced concrete bridge with elastic intermediate supports is presented. Such bridge represents either concrete or sandwich type three span bridge on polymeric supports for passive control or on actuators for active control The concrete slab is considered as a special orthotropic plate. The influence of the modulus of the foundation and $D_{22}$, $D_{12}$, $D_{66}$ stiffnesses on the natural frequency is thoroughly studied.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1990.10a
• /
• pp.1-6
• /
• 1990

Joints are provided in cement concrete pavements to control transverse and longitudinal cracking that occur due to restrained deformations caused by moisture and temperature variations in the slab. But the construction of joints reduces the load-carrying capacity of the pavement at the joints, and pavements have beem deteriorated by cracks at the slab edges along the joints due to traffic loads. Therefore, it is important to analyze the behavior of joints accurately in the design of cement concrete pavements. In this study, the mechanical behavior of cement concrete pavement slabs is analyzed by the plate-finite element model, and Winkler foundation model is adopted to analyze the subgrades. The load transfer mechanism of joints are composed of dowel action, aggregate interlocking, and tied-key action, and the analytical program is developed using these joint models.

• Journal of the Korean Geotechnical Society
• /
• v.22 no.4
• /
• pp.105-111
• /
• 2006

Earthquake strong motion recordings from two deeply embedded sites with instrumented structures and free-field accelerographs are used to evaluate variations between foundation-level and free-field ground motions. The foundation free-field ground motion variations are quantified in terms of frequency-dependent transmissibility function amplitude, ${\mid}H\mid$. Comparisons are then performed with an analytical model for the assumed conditions of a rigid base slab and a vertically propagating, coherent incident wave. The limiting assumptions of the model are not strictly satisfactory for actual structures, and the results of the analysis reflect not only incoherence effects, but also possible foundation flexibility and wave inclination effects. Nonetheless, the simple analytical model is in an acceptable agreement with the empirical analysis and appears to be applicable in practice.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 1995.04a
• /
• pp.53-56
• /
• 1995

Despite the recent development of structural analysis programs for the CRCP pavements over Westergaard's equations and finite element techniques, the Winkler foundations which are modelled by series of vertical springs at the nodes are generally used for the computer modelling of subbases under the concrete slab. Herewith, two parameter of soil foundation model is adopted as the most convenient mathematical model to enable deflections outside the loaded area to be effected and to upgrade the Winkler foundations. This paper highlights the derivations of finite element method for the two-parameter soil foundation model in the concrete pavements.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2000.10b
• /
• pp.1181-1186
• /
• 2000

The crack of concrete induced by the heat of hydration is a serious problem, particularly in concrete structures such as biers, thick walls, box type walls, mat-slab of nuclear reactor buildings, dams or foundations of high rise buildings, etc.. As a result of the temperature rise and restriction condition of foundation, the thermal stress which may induce the cracks can occur. Therefore the various techniques of the thermal stress control in massive concrete have been widely used. One of them is prediction of the thermal stress, besides low-heat cement which mitigates the temperature rise, design change which considers steel bar reinforcement, operation control and so on. In this study, firstly it introduce the thermal cracks control technique by employing low-heat cement concrete, thermal stress analysis considering season. Secondly it shows the application of the cracks control technique like block placement.

• Geomechanics and Engineering
• /
• v.37 no.5
• /
• pp.527-538
• /
• 2024

This study proposes a two-dimensional hyperbolic soil spring model for mat foundations in clays subjected to vertically uniform loads to simplify the complexity of three-dimensional finite element analysis on mat foundations. The solutions from three-dimensional finite element analysis were examined to determine the hyperbolic model parameters of the soil springs underneath the slab. Utilizing these model parameters, normalized functions across the middle section of the mat were obtained. The solutions from the proposed model, along with the approximate finite difference analysis of the mat in clays under vertical load, were found to be consistent with those from the three-dimensional finite element analysis. The authors conclude that the proposed method can serve as an alternative for the preliminary design of mat foundations.

• Composites Research
• /
• v.12 no.4
• /
• pp.25-32
• /
• 1999

A method of calculating the natural frequency corresponding to the first mode of vibration of beams and tower structures, with irregular cross sections and with arbitrary boundary conditions was developed and reported by Kim, D. H. in 1974. In this paper, the result of application of this method to the special orthotropic plates on elastic foundation with free boundaries is presented. Such plates represent the concrete highway slab and hybrid composite pavement on bridges. Any method may be used to obtain the deflection influence surfaces needed for this vibration analysis. Finite difference method is used for this purpose, in this paper. The influence of the modulus of the foundation and the aspect ratio of the plate on the natural frequency is thoroughly studied. The effect of neglecting the mass of the plates on the natural frequency, as the ratio of the point mass/masses to the plate mass increases, is also studied, in deep.