• Journal of the Korean Geosynthetics Society
• /
• v.8 no.3
• /
• pp.1-7
• /
• 2009

Earth reinforcement by using geogrids as reinforcing materials are widely applied to several earth structures. The bearing capacity of geogrid reinforced foundation soils is usually examined on based on the rigid plasticity theory or Limit Equilibrium Method. Method of analysis such Limit Equilibrium Method provide no detail information about failure behaviour or strain which develop in the reinforcement or foundation. In this paper the analysis of failure behaviour of strip footing on geogrid-reinforced sand over a soft caly was investigated by using a numerical method. A series of finite element analyses were performed on a geogrid-reinforced strip footing over a soft clay including number of geogrid layers, length, depth. We effectively investigated the failure behaviour and improvement of bearing capacity on the reinforced foundation soil by using FEM program.

• Steel and Composite Structures
• /
• v.21 no.2
• /
• pp.289-302
• /
• 2016

A new kind of partially precast or prefabricated castellated steel reinforced concrete beam, which is abbreviated here as CPSRC beam, was presented and introduced in this paper. This kind of CPSRC beam is composed of a precast outer-part and a cast-in-place inner-part. The precast outer-part is composed of an encased castellated steel shape, reinforcement bars and high performance concrete. The cast-in-place inner-part is made of common strength concrete, and is casted with the floor slabs simultaneously. In order to investigate the shear performance of the CPSRC beam, experiments of six CPSRC T-beam specimens, together with experiments of one cast-in-place SRC control T-beam specimen were conducted. All the specimens were subjected to sagging bending moment (or positive moment). In the tests, the influence of casting different strength of concrete in the cross section on the shear performance of the PPSRC beam was firstly emphasized, and the effect of the shear span-to-depth ratio on that were also especially taken into account too. During the tests, the shear force-deflection curves were recorded, while the strains of concrete, the steel shapes as well as the reinforcement stirrups at the shear zone of the specimens were also measured, and the crack propagation pattern together with the failure pattern was as well observed in detail. Based on the test results, the shear failure mechanism was clearly revealed, and the effect of the concrete strength and shear span-to-depth ratios were investigated. The shear capacity of such kind of CPSRC was furthermore discussed, and the influences of the holes on the steel shape on the shear performance were particularly analyzed.

• Journal of the Korea Concrete Institute
• /
• v.17 no.1 s.85
• /
• pp.51-58
• /
• 2005

Moment frames have been widely used in building construction. In current design codes, concrete moment frames are classified into ordinary, intermediate, and special moment resisting concrete frames (OMRCF, IMRCF, SMRCF)). The objective of this study is to investigate the seismic behavior of columns in ordinary moment resisting concrete frames (OMRCF) and intermediate moment resisting concrete frames (IMRCF). For this purpose 3 story OMRCF and IMRCF buildings were designed and detailed in compliance to ACI 318 (2002) and KCI (1999). In this study the buildings were assumed to be located in seismic zone 1 classified by UBC (1997). This study considered the columns in the 1st story since these columns shall resist the largest axial and lateral forces during an earthquake. Eight 2/3 scale column specimens were made for representing the upper part and lower part of exterior and interior columns of the OMRCF and the IMRCF Quasi-static reversed cyclic loading was applied to each specimen with a constant or varying axial load. Test results show that seismic behaviors of columns are influenced by existence of lap splices, axial force levels, and lateral reinforcement at possible plastic hinging region. However, the effect of such variables strongly co-related to each other.

• Journal of the Korean Geosynthetics Society
• /
• v.2 no.2
• /
• pp.13-24
• /
• 2003

This paper presents the results of investigation on the effects of foundation stiffness and surface loading on the performance of soil-reinforced segmental retaining walls using the finite element method of analysis. A parametric study was performed by varying the foundation stiffness and the location of surface loading. The results of the analyses indicate that the wall deformation and reinforcement tensile load tend to increase with decreasing foundation stiffness with little variation in the horizontal and vertical stress distributions at the back and the base of the reinforced soil zone. Also revealed is that the increment of reinforcement tensile load due to the presence of surface load may be significantly over-estimated when using the conventional approach. Furthermore, the external stability should be carefully examined when a surface loading is present just behind the reinforced soil zone. The implications of the findings from this study to current design approaches are discussed in detail.

• Journal of the Korean Geotechnical Society
• /
• v.21 no.10
• /
• pp.49-60
• /
• 2005

This paper presents the results of an investigation on the effects of design variables on the behavior of geosynthetic-reinforced modular block walls in a tiered arrangement using the finite-element method of numerical analysis. A parametric study was performed by varying the offset distance between the tiers and reinforcement length of the lower and upper tier using verified finite-element model. The finite-element analysis provided relevant information on the mechanical behavior of the tier wall and interaction mechanism between the upper and lower tier, which was otherwise difficult to obtain from the limit-equilibrium analysis based current design approaches. Practical implications of the findings obtained from this study in the current design approaches are discussed in great detail.

• Journal of the Korea Concrete Institute
• /
• v.13 no.4
• /
• pp.321-328
• /
• 2001

This paper presents the tensile behavior of stud connections installed between reinforced concrete and steel members. Eight specimens are tested to verify the factors influencing the tensile behavior of the connection. Major variables considered in the test are the reinforcement ratios of concrete member and connection details. Test results indicate that the reinforcing bars near stud bolts contribute to the increase of the tensile strength of the member as well as to the reduction of brittle failure. It is shown that C-type or U-type connection has relatively high ductility. From the evaluation on the tensile strength of test results including those of peformed by previous researchers, it was shown CCD (Concrete Capacity Design) method overestimated the strength. In this paper, the reduction factor of 0.75 ø instead of ø is suggested for design purpose of the stud connection.

• Nuclear Engineering and Technology
• /
• v.53 no.5
• /
• pp.1686-1704
• /
• 2021

This study addresses the numerical simulation of the shield building of an AP1000 nuclear power plant (NPP) subjected to a large commercial aircraft impact. First, a simplified finite element model (F.E. model) of the large commercial Boeing 737 MAX 8 aircraft is established. The F.E. model of the AP1000 shield building is constructed, which is a reasonably simplified reinforced concrete structure. The effectiveness of both F.E. models is verified by the classical Riera method and the impact test of a 1/7.5 scaled GE-J79 engine model. Then, based on the verified F.E. models, the entire impact process of the aircraft on the shield building is simulated by the missile-target interaction method (coupled method) and by the ANSYS/LS-DYNA software, which is at different initial impact velocities and impact heights. Finally, the laws and characteristics of the aircraft impact force, residual velocity, kinetic energy, concrete damage, axial reinforcement stress, and perforated size are analyzed in detail. The results show that all of them increase with the addition to the initial impact velocity. The first four are not very sensitive to the impact height. The engine impact mainly contributes to the peak impact force, and the peak impact force is six times higher than that in the first stage. With increasing initial impact velocity, the maximum aircraft impact force rises linearly. The range of the tension and pressure of the reinforcement axial stress changes with the impact height. The perforated size increases with increasing impact height. The radial perforation area is almost insensitive to the initial impact velocity and impact height. The research of this study can provide help for engineers in designing AP1000 shield buildings.

• Structural Engineering and Mechanics
• /
• v.84 no.5
• /
• pp.619-632
• /
• 2022

Reinforced concrete (RC) structures may be subjected to sudden dynamic impact loads such as explosions occurring for different reasons, the collision of masses driven by rockfall, flood, landslide, and avalanche effect structural members, the crash of vehicles to the highway and seaway structures. Many analytical, numerical, and experimental studies focused on the behavior of RC structural elements such as columns, beams, and slabs under sudden dynamic impact loads. However, there is no comprehensive study on the behavior of the RC column-beam connections under the effect of sudden dynamic impact loads. For this purpose, an experimental study was performed to investigate the behavior of RC column-beam connections under the effect of low-velocity impact loads. Sixteen RC beam-column connections with a scale of 1/3 were manufactured and tested under impact load using the drop-weight test setup. The concrete compressive strength, shear reinforcement spacing in the beam, and input impact energy applied to test specimens were taken as experimental variables. The time histories of impact load acting on test specimens, accelerations, and displacements measured from the test specimens were recorded in experiments. Besides, shear and bending crack widths were measured. The effect of experimental variables on the impact behavior of RC beam-column connections has been determined and interpreted in detail. Besides, a finite element model has been established for verification and comparison of the experimental results by using ABAQUS software. It has been demonstrated that concrete strength, shear reinforcement ratio, and impact energy significantly affect the impact behavior of RC column-beam connections.

• Structural Engineering and Mechanics
• /
• v.63 no.6
• /
• pp.725-734
• /
• 2017

This paper investigated the effects of rebar corrosion on bond performance between rebar and two different concrete mixes (compressive strengths of 20.7 MPa and 44.4 MPa). The specimen was designed as a rebar centrally embedded in a 200 mm concrete cube, with two stirrups around the rebar to supply confinement. An electrochemical accelerated corrosion technique was applied to corrode the rebar. 120 specimens of two different concrete mixes with various reinforcing steel corrosion levels were manufactured. The corrosion crack opening width and length were recorded in detail during and after the corrosion process. Three different loading schemes: monotonic pull-out load, 10 cycles of constant slip loading followed by pull-out and varied slip loading followed by pull-out, were carried out on the specimens. The effects of rebar corrosion with two different concrete mixes on corrosion crack opening, bond strength and corresponding slip value, initial slope of bond-slip curve, residual bond stress, mechanical interaction stress, and energy dissipation, were discussed in detail. The mean value and coefficient of variation of these parameters were also derived. It was found that the coefficient of variation of the parameters of the corroded specimens was larger than those with intact rebar. There is also obvious difference in the two different concrete mixes for the effects of rebar corrosion on bond-slip parameters.

• Journal of the Korea Concrete Institute
• /
• v.14 no.5
• /
• pp.774-781
• /
• 2002

Shear behaviors of eight dapped ends of four full-scale domestic single-tee slabs were evaluated. The dapped ends with 10cm topping concrete were designed based on live load requirements for the domestic parking lot of m 500kgf/㎡ and for the large market of 1,200 kgf/㎡. All specimens were designed by the ACI 318-99 design. The variations of the experiment were the shape of hanger reinforcements as followings: 1) general PCI design method(currently used in domestic), 2) 90 degree bent-up, 3) 60 degree bent-up. All experiments were conducted with 1.2 m shear span. The results obtained in this study were 1) all specimens fully complied with the shear strength requirements as specified by ACI 318-99 except for one strand bond slip specimen, 2)a specimen with the 60 degree bent up hanger reinforcing detail showed the best shear behaviors under full service and ultimate load, and 3)a specimen with the 90 degree bent up hanger reinforcing detail resulted in the worst shear behaviors.