• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.5 s.51
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• pp.49-61
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• 2006

The floor impact sound insulations are installed frequently for reducing the floor impact sound into the floor slab of the residential buildings in recent years. Therefore the analytical FE model considering the insulation is needed for the sound and vibration analysis of the floor and it is necessary to use a refined finite element model fer considering the large number of modes involved dynamic responses. So it is very difficult to use FE model because of the tiresome task for constructing the FE model, taking a lot of times for analysis and the impossibility of using the proportional damping. The efficient analysis and modeling method are proposed to the dynamic analysis for the floor with damping layer in this study. The floor slabs and finished layers are modeled individually and the spring elements that mean damping layers used to connect two parts. The dynamic analysis by the $Newmark-{\beta}$ method is performed to solve the non-proportional damping problem due to the damping coefficient of insulations.

• KCI Concrete Journal
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• v.13 no.2
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• pp.10-18
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• 2001

The spectral analysis of surface waves (SASW) method, which is an in-situ seismic technique, has mainly been developed and used for many years to determine the stiffness profile of layered media (such as asphalt concrete and layered soils) in an infinite half-space. This paper presents a modified experimental technique for nondestructive evaluation of in-place cement mortar compressive strength in single-layer concrete slabs of rather a finite thickness through a correlation to surface wave velocity. This correlation can be used in the quality control of early age cement mortar structures and in evaluating the integrity of structural members where the infinite half space condition is not met. In the proposed SASW field test, the surface of the structural members is subjected to an impact, using a 12 mm steel ball, to generate surface wave energy at various frequencies. Two accelerometer receivers detect the energy transmitted through the medium. By digitizing the analog receiver outputs, and recording the signals for spectral analysis, surface wave velocities can be identified. Modifications to the SASW method includes the reduction of boundary reflections as adopted on the surface waves before the point where the reflected compression waves reach the receivers. In this study, the correlation between the surface wave velocity and the compressive strength of cement mortar is developed using one 36"x36"x4"(91.44$\times$91.44$\times$91.44 cm) cement mortar slab of 2,000 psi (140 kgf/$\textrm{cm}^2$) and two 36"x36"x4"(91.44$\times$91.44$\times$91.44 cm) cement mortar slabs of 3,000 psi (210 kgf/$\textrm{cm}^2$).

• Korean Journal of Construction Engineering and Management
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• v.8 no.1 s.35
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• pp.124-131
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• 2007

Project management means usually managing the rate of construction progress. But it also contains preparing scheme of execution and establishing plan for equipment, material, labor force to finish project within expected duration. In this paper to establish effective project planning a road pavement operation is selected as a case and simulation method is used for analyzing it. Next probability distributions are created after analyzing collected data and these are reflected in simulation model. Simulated result is compared with real project planning using models of lean concrete pavement process and concrete slab pavement process to verify efficiency of this model. In the event we know that project planning using simulation is more effective than one of the field in the aspects of duration and cost. Meanwhile simulated result in this paper has a limitation in accuracy because various constraints of filed are not reflected in it. However if we reflect this constraints in model through examining field in future this limitation is expected to be improved.

• International Journal of Highway Engineering
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• v.12 no.1
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• pp.87-98
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• 2010

Surface of fine-size exposed aggregate Portland cement concrete pavements is consists of exposed coarse aggregate by removing upper 2~3mm mortar of concrete slab. Fine-size exposed aggregate PCC pavements have advantages of maintaining low-noise and adequate skid-resistance level during the performance period. In order to provide the successful exposed concrete aggregate pavement, uniform distribution of the coarse aggregate on pavement surface through adequate the mix design and exposing method. In this study, evaluated initial performance of fine-size exposed aggregate PCC pavement by experimental construction. And it was known that fine-size exposed aggregate concrete pavement which can reduce the noise and maintain the adequate level of skid resistance and strength.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.5
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• pp.27-33
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• 2010

In this study, a monotonic loading test to estimate structural capacity of 12 meter long full scale precast pre-stressed concrete beam specimen was performed with a 2,000 kN dynamic actuator. A couple of embedded steel plate was installed at the ends of the beam and specimens were connected to steel girder frame with high tension bolts. Nominal compressive strength of pre-stressed concrete beam and slab were 50 MPa and 24 MPa respectively. Two HD25 tensile steel reinforcements were welded on vertical plate of embedded steel plate. Pre-stressed concrete beam specimen was loaded by displacement control method with a certain loading pattern which was repeated loading and unloading with 10mm increment displacement. About 88.34%, 86.97% and 66.83% of displacement restoration ratios were evaluated at elastic, inelastic and plastic behavior region of specimen respectively.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.4
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• pp.25-33
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• 1999

Leaky wave radiation and surface wave launching problems in a dielectrically covered and periodically slitted parallel-plate waveguide(PPW) are considered for the TEM wave incidence case. Both the infinite and finite periodic geometries are analyzed by use of the method of moments. Some numerical results for the reflected and transmitted powers in the PPW, radiation efficiency into the free space, surface wave launching efficiency into the slab, antenna gain, and radiation patterns against dielectric thickness are presented to show the effect of the dielectric cover on the performances of the slitted leaky wave antenna. In addition, the method for improving surface wave launching efficiency using the proposed periodic geometry is described and maximum launching efficiency of 97.5% is obtained theoretically. So this structure is thought to be promising as an efficient feeder of dielectric grating antenna as well as image guide.

• Journal of Korean Tunnelling and Underground Space Association
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• v.13 no.1
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• pp.9-18
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• 2011

The spalling phenomenon occurs in high-strength concrete when several factors such as sharp temperature increase, high water content, low water/cement ratio and local stress concentration in material combine in the concrete material. On the basis of the factors, the preventing methods from the spalling are known as reduction of temperature increase, preventing of concrete fragmentation and fast drying of internal moisture. In this study, the reduction of temperature increase was proposed as the most effective spalling-preventing method among the spalling-preventing methods. Engineered cementitious composite for fireproof and repair materials was developed in order to protect the new and existing RC structures form exterior deterioration factors such as fire, cloride ion, etc. This study was carried out to estimate the fire-resisting performance of high strength concrete slab or tunnel lining by repaired engineered cementitious composite (ECC) or fiber reinforcement cemetitious composite (FRCC) under fire temperature curve. and them we will descrike the result of HIDA tunnel in Japan.

• Journal of the Korea Institute of Building Construction
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• v.9 no.6
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• pp.121-129
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• 2009

The construction sites of small and medium buildings have small scale groundwork and the depth of excavation is often shallow. In this case, if the groundwork, girders, and ground slabs are built simultaneously by embedded assisting form rather than the existing conventional method to place concrete twice using the general form, we can expect to reduce the frame duration of the basement, resulting in cost savings. The existing embedded assisting form is restricted from use because there are cost problems with materials, labor costs,and with quality depending on the form's type. Therefore, this study is to provide an improved suggestion of building the groundwork, girders, and ground slabs simultaneously with Polystyrene by using the embedded assisting form. It also will compare the technique with existing methods of construction, and will verify its usefulness by evaluating each method of construction.

• Korean Journal of Construction Engineering and Management
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• v.5 no.3 s.19
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• pp.106-113
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• 2004

Most construction project managers should focus on the reasonable cost-down with same quality and function-enhancement with same cost for the value-added construction project delivery in construction industry. Especially, a building structure construction is one of the most important processes to affect the total cost and schedule in building construction project. It means that the process has the possibility of project cost-down or quality-enhancement among the whole project life-cycle. This research focuses on the importance of underground structure of building project by increasing underground use ratio in the urban building construction projects nowadays. This research adopts VE method for the improvement of cost and time by process and analysis dimension modeling on the underground building structure construction, and verifies it throughout the case study, This research is the basic study on the improvement of underground building works through the value engineering method in construction industry.

• Computers and Concrete
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• v.3 no.4
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• pp.213-233
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• 2006

Over the past years techniques for non-linear analysis have been enhanced significantly via improved solution procedures, extended finite element techniques and increased robustness of constitutive models. Nevertheless, problems remain, especially for real world structures of softening materials like concrete. The softening gives negative stiffness and risk of bifurcations due to multiple cracks that compete to survive. Incremental-iterative techniques have difficulties in selecting and handling the local peaks and snap-backs. In this contribution, an alternative method is proposed. The softening diagram of negative slope is replaced by a saw-tooth diagram of positive slopes. The incremental-iterative Newton method is replaced by a series of linear analyses using a special scaling technique with subsequent stiffness/strength reduction per critical element. It is shown that this event-by-event strategy is robust and reliable. First, the model is shown to be objective with respect to mesh refinement. Next, the example of a large-scale dog-bone specimen in direct tension is analyzed using an isotropic version of the saw-tooth model. The model is capable of automatically providing the snap-back response. Subsequently, the saw-tooth model is extended to include anisotropy for fixed crack directions to accommodate both tensile cracking and compression strut action for reinforced concrete. Three different reinforced concrete structures are analyzed, a tension-pull specimen, a slender beam and a slab. In all cases, the model naturally provides the local peaks and snap-backs associated with the subsequent development of primary cracks starting from the rebar. The secant saw-tooth stiffness is always positive and the analysis always 'converges'. Bifurcations are prevented due to the scaling technique.