• Computers and Concrete
• /
• v.13 no.3
• /
• pp.377-387
• /
• 2014

This paper presents an experimental study on socket base connections of precast reinforced concrete columns. The main purpose of this study is to determine socket base connection which has the closest behavior to monolithic casted column-base joints. For this purpose, six specimens having different column-socket base connection details were tested under cyclic loading. For each test, strength, stiffness, ductility and drift ratios of the specimens were determined. Test results indicated that a suggested connection type is 10%-30% stronger than the other type of connections under lateral loading. The welded connection (PC-5) had better lateral load carrying capacity and ductility. On the other hand, performance of standard connection (PC-1) which is commonly used in construction was weaker than other connections. Thus, decision of connection type should be referred not only performance but also applicability.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2001.04a
• /
• pp.453-460
• /
• 2001

The seismic capacity of columns usually has been tested in uniaxial loading condition. The seismic performance used to be evaluated under the same assumption. Since the real earthquake motion is multi-directional, the effects of multi-directional excitation on the seismic capacity of structures need to be carefully examined. In this paper, a frequency dependent alternate biaxial cyclic loading test is proposed as an evaluation method of seismic capacity under multi-directional excitation. Four test specimens were made and tested to study the degradation of strength, stiffness and ductility under biaxial loading condition. A multi- directional excitation. The capacity is obtained using frequency dependent alternate biaxial cyclic loading test. The orthogonal effect is taken into account by increasing the demand.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.05a
• /
• pp.214-217
• /
• 2006

It is well known that RC piers having 50% of lap-spliced longitudinal bars in plastic hinge region have a good ductility relatively. But the deformability under various loading condition is not confirmed. In this study scale models with different confinement were tested under different axial loads and loading cycles. It was confirmed that deformability was decreased with increase of axial force and number of loading cycles and that the models having 75% of confinement specified in present code satisfy the required seismic performance.

• ETRI Journal
• /
• v.29 no.4
• /
• pp.445-451
• /
• 2007

An adaptive modulation scheme is presented for multiuser orthogonal frequency-division multiplexing systems. The aim of the scheme is to minimize the total transmit power with a constraint on the transmission rate for users, assuming knowledge of the instantaneous channel gains for all users using a combined bit-loading and subcarrier allocation algorithm. The subcarrier allocation algorithm identifies the appropriate assignment of subcarriers to the users, while the bit-loading algorithm determines the number of bits given to each subcarrier. The proposed bit-loading algorithm is derived from the geometric progression of the additional transmission power required by the subcarriers and the arithmetic-geometric means inequality. This algorithm has a simple procedure and low computational complexity. A heuristic approach is also used for the subcarrier allocation algorithm, providing a trade-off between complexity and performance. Numerical results demonstrate that the proposed algorithms provide comparable performance with existing algorithms with low computational cost.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2014.11a
• /
• pp.141-142
• /
• 2014

Decrease of performance degradation of High Strength Concrete occurs more than that of normal strength concrete at elevated temperature. Therefore, when it comes to evaluating performance of structures, strain of concrete subjected to elevated temperature and loading are important items. In this study, creep strain of High Strength Concrete sunjected to various temperature conditions and 33% loading was evaluated. As a result, creep strain increased with increase of temperature and loading. Creep strain of concrete at high temperature is influenced by loading.

• Computers and Concrete
• /
• v.13 no.6
• /
• pp.749-764
• /
• 2014

Structural safety has always been a key preoccupation for engineers responsible for the design of civil engineering projects. One of the mechanisms of structural failure, which has gathered increasing attention over the past few decades, is referred to as 'progressive collapse' which happens when one or several structural members suddenly fail, whatever the cause (accident, attack, seismic loading(.Any weakness in design or construction of structural elements can induce the progressive collapse in structures, during seismic loading. Masonry infill panels have significant influence on structure response against the lateral load. Therefore in this paper, seismic performance and shear strength of R.C frames with brick infill panel under various lateral loading patterns are investigated. This evaluation is performed by nonlinear static analysis. The results provided important information for additional design guidance on seismic safety of RC frames with brick infill panel under progressive collapse.

• KCI Concrete Journal
• /
• v.12 no.1
• /
• pp.69-77
• /
• 2000

The reinforced concrete(RC) flexural members strengthened with steel plate/CFS at soffit have initial stresses and strains in reinforcements and concrete caused by the service loads at the time of retrofitting works. These initial residual stresses and strains of strengthened beams may affect the flexural performance of the rehabilitated beams. The objective of this study is to evaluate and verify the effectiveness of rehabilitation by external bonded steel plates and CFS to the tension face of the beams under three conditions of pre-loading. Thirteen beam specimens are tested and analyzed. Main test parameters are pre-loading conditions, strengthening materials and reinforcement ratio of specimens. The effect of test parameters on the strengthened beams is analyzed from the maximum load capacity, load-deflection relationship, state of stress of the materials. crack propagation phase, and failure modes. Both test results and design formulas of ACI Code provisions are compared and evaluated.

• Journal of Information Processing Systems
• /
• v.10 no.2
• /
• pp.163-175
• /
• 2014

This paper will focus on improving the performance of orthogonal frequency division multiplexing (OFDM) in Rayleigh fading environments. The proposed technique will use a previously published method that has been shown to improve OFDM performance in independent fading, based on ordered sub-carrier selection. Then, a simple non-iterative method for finding the optimal bit-loading allocation was proposed. It was also based on ordered sub-carrier selection. We compared both of these algorithms to an optimal bit-loading solution to determine their effectiveness in a correlated fading environment. The correlated fading was simulated using the JTC channel models. Our intent was not to create an optimal solution, but to create a low complexity solution that can be used in a wireless environment in which the channel conditions change rapidly and that require a simple algorithm for fast bit loading.

• Nuclear Engineering and Technology
• /
• v.49 no.4
• /
• pp.855-864
• /
• 2017

The control rod assembly controls reactor power by adjusting its position during normal operation and shuts down chain reactions by its free drop under scram conditions. Therefore, the drop performance of the control rod assembly is important for the safety of a nuclear reactor. In this study, the drop performance of the conceptually designed control rod assembly for the prototype generation IV sodium-cooled fast reactor that is being developed at the Korea Atomic Energy Research Institute as a next-generation nuclear reactor was experimentally investigated. For the performance test, the test facility and test procedure were established first, and several free drop performance tests of the control rod assembly under different flow rate conditions were then carried out. Moreover, performance tests under several types and magnitudes of seismic loading conditions were also conducted to investigate the effects of seismic loading on the drop performance of the control rod assembly. The drop time of the conceptually designed control rod assembly for 0% of the tentatively designed flow rate was measured to be 1.527 seconds, and this agrees well with the analytically calculated drop time. It was also observed that the effect of seismic loading on the drop time was not significant.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2001.11a
• /
• pp.707-712
• /
• 2001

This paper compares the moment-curvature relations of reinforced concrete columns subjected to various loading histories. A sectional analysis was proposed to predict the behavior of reinforced concrete columns. The proposed analysis predicted the real moment-curvature relations of reinforced concrete columns with good agreement. Four types of loading programs were adapted to the analysis. The analysed results indicated that the moment-curvature relations of reinforced concrete columns were strongly affected by the loading history.