• Journal of the Society of Naval Architects of Korea
• /
• v.29 no.1
• /
• pp.158-172
• /
• 1992

In ships and offshore structures, there are many local structures formed of thick plates and/or having the form of double wall panels. For the vibration analysis of such a kind of structures, Mindlin plate theory which includes the effects of shear deformation and rotary inertia is usually adopted. In this paper, the vibration and dynamic sensitivity analysis of Mindlin plates having the boundary conditions elastically restrained against rotation have been accomplished using the Rayleigh-Ritz method. Polynomials having the property of the Timoshenko beam functions are introduced and used as trial functions in the spatial representation of the deflection and rotations of cross sections in two directions of the plates. The results obtained by the introduced polynomials gave nearly the same numerical results as those by the Timoshenko beam functions with the remarkable reduction of computational efforts especially in the dynamic sensitivity analysis.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.3A
• /
• pp.447-455
• /
• 2006

A general purpose of 4-node co-rotational resultant shell element is developed for the solution of nonlinear problems of reinforced concrete, steel and fiber-reinforced composite structures. The formulation of the geometrical stiffness presented here is defined on the mid-surface by using the second order kinematic relations and is efficient for analyzing thick plates and shells by incorporating bending moment and transverse shear resultant forces. The present element is free of shear locking behavior by using the ANS (Assumed Natural Strain) method such that the element performs very well as thin shells. Inelastic behaviour of concrete material is based on the plasticity with strain hardening and elasto-plastic fracture model. The plasticity of steel is based on Von-Mises Yield and Ivanov Yield criteria with strain hardening. The transverse shear stiffness of laminate composite is defined by an equilibrium approach instead of using the shear correction factor. The proposed formulation is computationally efficient and versitile for most civil engineering application and the test results showed good agreement.

• Journal of the Society of Naval Architects of Korea
• /
• v.37 no.3
• /
• pp.99-109
• /
• 2000

Elastic dynamic responses analysis program for ship hulls considering slamming impact loads due to the voyage in large amplitude waves is developed. Ship hull structures are modeled by a thin-walled beam model in order to consider effects of shear deformation. The momentum slamming theory is used to derive nonlinear hydrodynamic forces considering intersection between wave particles and ship section. For the validation of the developed computer program, motions of a V-shaped simple section model and S-175 standard container model are calculated and analyzed. In each numerical example, time histories of relative displacement, velocity and vertical bending moment of a ship section are derived, considering the effect of slamming impacts in various wave conditions.ures near the free surface as well as the wake of the hydrofoil.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1995.10a
• /
• pp.208-216
• /
• 1995

대형선박, 항공기, 초고층 건축물 등은 얇은 박판 형태의 보로 이상화하여 구조 및 진동해석을 수행할 수 있다. 이러한 형태로 이상화한 구조물은 비틀림 강도면에서 매우 취약함을 보이고, 굽힘-비틀림 진동은 단면형상에 따라 연성도가 심화된다. 상하 굽힘 진동은 탄성거동 영역에서 도심과 전단중심이 일치하는 대칭 진동(Symmetric vibration) 현상을 보인다. 그러나, 수평 굽힘 진동은 도심과 전단중심의 차이가 커질수록 즉, 연성도가 높아질수록 비틀림 진동과 복합되어 복잡한 비대칭 진동(Antisymmetric vibration) 현상을 나타낸다. 본 논문에서는 연성효과에 의한 수평 굽힘 진동과 비틀림 진동 현상에 대한 연구를 수행하였고, 진동계산을 위해서 전달행렬법(Transfer Matrix Method)을 사용하였다. 수치계산은 첫번째로, 도심과 전단중심의 차이가 매우 작아 연성도를 무시할 수 있을 정도의 구조물에 대해서 일반적인 수평 굽힘 진동 현상과 비틀림 진동 현상을 연구하였다. 두번째로, 연성도가 매우 심할 경우에 굽힘-비틀림 연성 진동 현상을 Timoshenko 보의 이론과 Vlasov 보의이로네 따라 각각 계산을 수행하였다. 마지막으로, 첫번째와 두번째 구조를 결합한 경우에 대해서 굽힘-비틀림 연성 진동 현상을 연구하였다. 이 경우에 두 구조물의 결합부에서 비틀림 강성과 Warping 강성의 심한 변화로 인한 불연속 경계면이 발생하게 되고 이때의 진동해석을 위해서 보 이론에 기초를 두고 상당히 높은 정확도를 제공하는 Haslum[2] 등과 Pedersen[3]이 제시한 이론을 이용하였다.

• Journal of Korean Society of Steel Construction
• /
• v.25 no.5
• /
• pp.519-530
• /
• 2013

Cyclic tests on modular building units for low-rise buildings composed of stud panels and a light-weight steel perimeter frame, were performed to evaluate the earthquake resistance such as stiffness, load-carrying capacity, ductility, and energy dissipation per load cycle. The strap-braced and sheeted stud panels were used as the primary lateral load-resistant element of the modular building units. Test results showed that the modular building units using the strap-braced and sheeted stud panels exhibited excellent post-yield ductile behaviors. The maximum drift ratios were greater than 5.37% and the displacement ductility ratios were greater than 5.76. However, the energy dissipation per load cycle was poor due to severe pinching during cyclic loading. Nominal strength, stiffness, and yield displacement of the modular building units were predicted based on plastic mechanisms. The predictions reasonably and conservatively correlated with the test results. However, the elastic stiffness of the strap-braced stud panel was significantly overestimated. For conservative design, the elastic stiffness of the strap-braced stud panel needs be decreased to 50% of the nominal value.

• Journal of Korean Society of Steel Construction
• /
• v.28 no.6
• /
• pp.415-425
• /
• 2016

Load-bearing steel stud wall system is widely used for the middle-to-high rise modular buildings worldwide. Seismic performance is a key issue to apply load-bearing steel stud wall system to modular buildings in Korea. This study proposes a new strap braced steel stud wall system with enhanced seismic performance and design equations considering the flexural behaviour of the vertical outer studs. For the verification, two specimens with different strap braces and vertical outer stud were designed and tested. The test results showed that the total strengths were evaluated to be 1.11 to 1.18 times higher than the predicted values. Usually strap braced walls are considered to have low energy dissipation capacities. The proposed system showed enhanced seismic performance with equivalent damping of 9.42% due to the reduced pinching effects.

• Journal of Korean Society of Steel Construction
• /
• v.28 no.6
• /
• pp.427-438
• /
• 2016

This study is experimental research for the effect of gap at the end plate on the performance of extended end-plate type splice. For this research, simple beam type specimens by using extended end-plate type splice are planned. Main variables are the initial gap between end-plates, the installation of finger shim plate before the installation of high tension bolts, the final gap between end-plates, and the installation of finger shim plate after the installation of high tension bolts. The static loading tests results show that the maximum bending strength of splice is not dependent on the gap, but the vertical displacement, initial stiffness and elastic stiffness are affected by the gap. In addition to that, the possibility of brittle fracture is increased when the torque of high tension bolt is used to control the gap. Thus, careful consideration is needed in this case.

• Composites Research
• /
• v.12 no.6
• /
• pp.53-64
• /
• 1999

Microstructural morphology and bending strengths of moulded composites of thermotropic liquid crystalline polymer(LCP) and polyamide 6 (PA6) have been studied as a function of epoxy fraction. Injection-moulding of a composite plaque at a temperature below the melting point of the LCP fibrils generated a multi-layered structure: the surface skin layer with thickness of $65\;-\;120{\mu\textrm{m}}$ exhibiting a transverse orientation; the sub-skin layer with an orientation in the flow direction; the core layer with arc-curved flow patterns. The plaques containing epoxy 4.8vol% exhibited superior bending strength and large fracture strain. With an increase of epoxy fraction equal to and beyond 4.8vol%, geometry of LCP domains was changed from fibrillar shape to lamella-like one, which caused a shear-mode fracture. An analysis of the bending strength of the composite plaques by using a symmetric layered model beam suggested that addition of epoxy component altered not only the microstructural geometry but also the elastic moduli and strengths of the respective layers.

• Composites Research
• /
• v.30 no.1
• /
• pp.15-20
• /
• 2017

In this study, LIPCA-S2 actuator with a piezoelectric single crystal layer and a carbon/epoxy layer was designed and evaluated to increase actuation performance of piezo-composite unimorph actuator. A curvature change model generated by the induced strain of a piezoelectric layer was used to predict the tip displacement of the piezo-composite unimorph cantilever. However, we found that there was big difference between the predicted and the measured tip displacement of LIPCA-S2 cantilever actuator when we used the previous linear prediction model. A new prediction model considering the change of piezoelectric strain coefficient and elastic modulus for the compression stress variation of the PMN-29PT single crystal layer was used and it was found that the difference between the predicted and the measured tip displacement reduced considerably.

• The Journal of the Acoustical Society of Korea
• /
• v.22 no.1
• /
• pp.61-68
• /
• 2003

The guided wave has been widely employed to characterize thin plates and layered media. The dispersion curves of phase and group velocities are essential for the quantitative application of guided waves. In the present work, a fully automated system for the measurement of backward radiation of LLW has been developed. The specimen moves in two dimensional plane as well as in angular rotation. The signals of backward radiation of LLW were measured from an elastic plate in which specific modes of Lamb wave were strongly generated. Phase velocity of the corresponding modes was determined from the incident angle. The generated Lamb waves propagated forward and backward with the leakage of energy into water. Backward radiated LLW was detected by the same transducer and its frequency components were analyzed to extract the related information to the dispersion curves. The dispersion curves of phase velocity were measured by varying the incident angle. Moving the specimen in the linear direction of LLW propagation, group velocity was determined by measuring the transit time shift in the ultrasonic waveform.