• Structural Engineering and Mechanics
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• v.5 no.5
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• pp.507-521
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• 1997

The ultimate behavior of a reinforced concrete hyperbolic paraboloid saddle shell under uniformly distributed vertical load is investigated using an inelastic, large displacement finite-element program originally developed at North Carolina State University. Unlike with the author's previous study which shows that the saddle shell possesses a tremendous capacity to redistribute the stresses, introducing tension stiffening in the model the cracks developed are no longer through cracks and formed as primarily bending cracks. Even though with small tension stiffening effect, the behavior of the shell is changed markedly from the one without tension stiffening effect. The load-deflection curves are straight and the slope of the curves is quite steep and remains unchanged with varying the tension stiffening parameters. The failure of the shell took place quite suddenly in a cantilever mode initiated by a formation of yield lines in a direction parallel to the support-to-support diagonal. The higher the tension stiffening parameters the higher is the ultimate load. The present study shows that the ultimate behavior of the shell primarily depends on the concrete tensile characteristics, such as tensile strength (before cracking) and the effective tension stiffening (after cracking). As the concrete characteristics would vary over the life of the shell, a degree of uncertainty is involved in deciding a specified ultimate strength of the saddle shell studied. By the present study, however, the overload factors based on ACI 318-95 are larger than unity for all the cases studied except that the tension stiffening parameter is weak by 3 with and without the large displacement effect, which shows that the Lin-Scordelis saddle shell studied here is at least safe.

• The Journal of Korean Academy of Prosthodontics
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• v.37 no.5
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• pp.607-619
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• 1999

Cortical support is an important factor, as the engagement of the fixture in strong compact bone offers an increased load-carrying capacity and initial stability. Because of the poor bone quality in the posterior mandible and other anatomic considerations, it has been suggested that implant fixtures be placed in these locations with apical engagement of the lingual cortical plate for so-called bicortication. The purpose of this investigation was to determine the effect of cortical engagements and in addition polyoxymethylene(POM) intramobile connector(IMC) of IMZ implant on implant load transfer in edentulous posterior segment of mandible, using three-dimensional (3D) finite element analysis models composed of cortical and trabecular bone involving single implant. Variables such as (1) the crestal peri-implant defect, (2) the apical engagement of lingual cortical plate, (3) the occlusal contact position (a vertical load at central fossa or buccal cusp tip), and (4) POM IMC were investigated. Stress patterns were compared and interfacial stresses along the bone-implant interface were monitored specially. Within the scope of this study, the following observations were made. 1) Offset load and angulation of fixture led to increase the local interfacial stresses. 2) Stresses were concentrated toward the cortical bones, but the crestal peri-implant defect increased the interfacial stresses in trabecular bone. 3) For the model with bicortication, it was noticed that the crestal cortical bone provided more resistance to the bending moment and the lingual cortical plate provided more support for the vertical load. But Angulation problem of the fixture from the lingual cortical engagement caused the local interfacial stress concentrations. 4) It was not clear that POM IMC had the effect on stress distribution under the present experimental conditions, especially for the cases of crestal peri-implant defect.

• Journal of the Korea Concrete Institute
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• v.15 no.6
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• pp.856-865
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• 2003

Current design provisions and guide for performance-based design do not accurately evaluate seismic performance of flat plate system. In the previous companion studies, parametric studies using nonlinear finite element analyses were performed to investigate behavior of the flat plate, and based on the numerical results, design methods that can predict the bending moment-carrying capacity and the corresponding deformability of the flat plate was developed. In the present study, a generalized moment-rotation relation of the flat plate was developed based on the previous studies and the numerical analyses. The proposed method was verified by the comparisons with existing experiments. In addition, the effective stiffness of the flat plate corresponding to 0.2 percent of lateral drift that is generally regarded as the serviceability limit was proposed, so as to evaluate conveniently deflection of the structure subject to wind load.

• Journal of Industrial Technology
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• v.3
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• pp.103-116
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• 1983

Recent developments in multi-storey buildings for residential purpose have led to the extensive use of shear walls for the basic structural system. When the coupled shear wall system is used, joined together with cast-in-place concrete or mortar (or grout), the function of the continuous joints is a crucial factor in determining the safety of L.P. Precast concrete shear wall structures, because the function of the continuous joints(Vertical wall to wall joints) is to transfer froces from one element(shear wall panel) to another, and if sufficient strength and ductility is not developed in the continuous joints, the available strength in the adjoining elements may not be fully utilized. In this paper, the influence of the stiffness of vertical joints(wet vertical keyed shear joints) on the behaviour of precast shear walls is theoretically investigated. To define how the stiffness of the vertical joints affect the load carrying capacity of L.P.Precast concrete shear wall structure, the L.P.Precast concrete shear wall structure is analyzed, with the stiffness of the vertical joints varying from $K=0.07kg/mm^3$(50MN/m/m) to $K=1.43kg/mm^3$(1000MN/m/m), by using the continuous connection method. The results of the analysis shows that at the low values of the vertical stiffness, i.e. from $K=0.07kg/mm^3$(50MN/m/m) to $K=0.57kg/mm^3$(400MN/m/m), the resisting bending moment and shearing force of precast shear walls, the resisting shearing force of vertical joints and connecting beams are significantly affected. The detailed results of analysis are represented in the following figures and Tables.

• Steel and Composite Structures
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• v.22 no.4
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• pp.753-775
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• 2016

This paper aims to investigate the demountability of steel column-baseplate connections subjected to monotonic and cyclic loading. This paper presents the finite element analysis of steel column-baseplate connections under monotonic and cyclic loading. The finite element model takes into account the effects of material and geometric nonlinearities. Bauschinger and pinching effects were also included in the developed model, through which degradation of steel yield strength in cyclic loading can be well simulated. The results obtained from the finite element model are compared with the existing experimental results. It is demonstrated that the finite element model accurately predicts the initial stiffness, ultimate bending moment strength of steel column-baseplate connections. The finite element model is utilised to examine the effects of axial load, baseplate thickness, anchor bolt diameter and position on the behaviour of steel column-baseplate connections. The effects of various parameters on the demountability of steel column-baseplate connections are investigated. To achieve a demountable and reusable structure, various design parameters need to be considered. Initial stiffness and moment capacity of steel columnbaseplate connections are compared with design strengths from Eurocode 3. The comparison between finite element analysis and Eurocode 3 indicates that predictions of initial stiffness for semi-rigid connections should be developed and improved design of the connections needs to be used in engineering practice.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.2
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• pp.250-263
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• 2001

The up and down speed of heddle frames that produce woven cloth by insertion of weft yarns between warp yarns has been increased recently much for productivity improvement, which induces higher inertial stresses and vibrations in the heddle frame. the heddle frame is required to reduce its mass because the heddle frame contributes the major portion of the stresses in the heddle frames during accelerating and decelerating. Conventional aluminum heddle frames have fatigue life of around 5 months at 550rpm due to their low fatigue flexural strength as well as low bending stiffness. In this work, since carbon/epoxy composite materials have high specific fatigue strength(S/p), high specific modulus(E/p), high damping capacity and sandwich construction results in lower deflections and higher buckling resistance, the sandwich structure composed of carbon/epoxy composite skins and polyurethane foam were employed for the high-speed heddle frame. The design map for the sandwich beams was accomplished to determine the optimum thickness and the stacking sequences for the heddle frames. Also the effects of the number of ribs on the stress of the heddle frame were investigated by FEM analyses. Finally, the high-speed heddle frames were manufactured with sandwich structures and the static and dynamic properties of the aluminum and the composite heddle frames were tested and compared with each other.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.9
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• pp.1293-1298
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• 2010

In most power plants, wall thinning in carbon-steel pipes due to flow-accelerated corrosion is one of the major aging phenomena, and it reduces the load-carrying capacity of the piping system. Various types of wall-thinning defects were manufactured in real-scale elbows, and monotonic in-plane bending tests were performed under internal pressure to evaluate the failure behavior of the elbows. In this paper, the behavior of elastic and plastic limit leads of locally thinned elbows in a real-scale failure test is presented. The loads determined on the basis of TES (twice elastic slope) were considered to be the limit loads of locally thinned elbows so that the integrity of the thinned elbows could be maintained, even when a small amount of plastic deformation might have occurred.

• Land and Housing Review
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• v.2 no.3
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• pp.277-285
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• 2011

To reinforce bearing capacity-changed section or different foundation in the same building, empirical or simple tools have been used. To solve this problem, an analytical solution which can evaluate and reinforce the stability of foundation is introduced. To suggest a clue for the problems, current foundation reinforcing method is studied through recent literature studies and the structural analyses of foundation slab are performed on the pile foundation of 49$m^2$, 59$m^2$ and 84$m^2$ I type apartments in 15 story building. The analyses are conducted with SAP 2000, a computer program for ordinary structural analysis. To predict the moments of slab by ground non-uniformity, the structural analysis results for the foundation slab of 3 types 15 story apartment buildings in 49$m^2$, 59$m^2$ and 84$m^2$ I type on non-uniformity ground are shown in the diagrams.

• Journal of Korean Society of Steel Construction
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• v.9 no.4 s.33
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• pp.589-600
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• 1997

Cold-formed deck sections are used in many composite floor slab applications wherein the steel deck serves not only as the form for the concrete during construction but also as the principal tensile reinforcement for the bottom fiber of the composite slab. This paper provides the results of an experimental study performed for the composite slabs with the new shaped deck plates with the locking ribs, the dove tails, and the powerful embossment, which are the mechanical means to improve positive interlocking effect between the deck and the concrete. A total of 28 specimens are tested to investigate the composite effects between the concrete and metal deck plate. Important parameters in this are the span length, the thickness of the deck plate, support condition, and whether shear studs are placed at each support or not. The test results are summarized for the maximum load and failure behavior for the specimens.

• Journal of Korean Society of Steel Construction
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• v.19 no.3
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• pp.247-258
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• 2007

This paper describes the results of an experimental study on the new type of encased composite beams that use deep deck plates, which could reduce the story height of buildings by controlling the bottom flange of steel beams. The profiled steel beam was thus developed. It was advantageous to the long span of the buildings. Seven full-scale specimens were constructed, and simply supported bending tests were conducted on the encased composite beams with different steel plate thicknesses, with and without shear studs, reinforcing bars, and web openings. The test results showed that the encased composite beams that were developed in this study had sufficient composite action without additional shear connectors due to their inherent shear-bond effects between the steel beams and concrete.