• Journal of the Korean Society of Safety
• /
• v.23 no.5
• /
• pp.84-90
• /
• 2008

The occurrence of longitudinal cracking in concrete deck of box girder bridge is affected by many factors, but the most important factors are the shrinkage and thermal gradient of deck slabs. In this study, therefore, the tensile stresses at the bottom of deck were calculated from the experimental data(autogeneous shrinkage, drying shrinkage, and thermal gradient of deck slab). Also, the possibility of longitudinal cracks at bottom of deck was estimated. For this purpose, full-scale box girder segments have been fabricated and tested. The thermal gradients and shrinkage strains of deck slabs were measured after placement of concrete. Also, analytic program was conducted for the evaluation of longitudinal cracking in bridge deck considering differential shrinkage induced from non-uniform moisture distributions in concrete.

• Journal of the Society of Naval Architects of Korea
• /
• v.44 no.5
• /
• pp.504-508
• /
• 2007

In the case of thin plate blocks, buckling deformation due to longitudinal shrinkage is the most important weld-induced deformation. This paper is concerned with developing the formula to predict the longitudinal shrinkage due to welding, in which mechanical tension effect in welding direction is accounted for. For this purpose, bead on plate welding test has been carried out for the 27 thin plate specimens with varying welding conditions and magnitude of tensile load. Empirical formula of predicting the longitudinal shrinkage has been derived based on the results of welding test, in which effect of mechanical tension is included. The derived formula can be usefully used in predicting the level of tensile load to reduce the longitudinal shrinkage.

• Journal of Welding and Joining
• /
• v.34 no.6
• /
• pp.20-27
• /
• 2016

This study deals with the proper conditions of the trail rolling method (TRM) for the prevention of the buckling welding distortion at the AA5083 GMA butt weldment. For it, the effect of the working conditions of TRM including the rolling depth and the rolling distance between the welding torch and the roller on the longitudinal welding shrinkage force of the weldment was evaluated by using 3 dimensional thermo-mechanical FE analyses. The longitudinal welding shrinkage force inducing the buckling welding distortion at the GMA butt weldment was mitigated with an increase in the rolling depth and the rolling distance between the welding torch and the roller. Based on the results, the proper conditions of trail rolling method were established to reduce the longitudinal welding shrinkage force of the GMA butt weldment to below the critical value corresponding to the bucking distortion.

• Computers and Concrete
• /
• v.23 no.5
• /
• pp.329-334
• /
• 2019

Traffic flow capacity of some old road bridges is insufficient due to limited deck width. In such cases bridge deck widening is a common solution. For multi-girder reinforced concrete (RC) bridges it is possible to add steel-concrete composite girders as the new outermost girders. The deck widening may be combined with bridge strengthening thanks to thickening of the existing deck slab. Joint action of the existing and the added parts of such bridge span must be ensured. It refers especially to the horizontal plane at the interface of the existing slab and the added concrete layer as well as to the vertical planes at the external surfaces of the initially outermost girders where the added girders are connected to the existing bridge span. Since the distribution of the added concrete is non-uniform in the span cross-section the structure is particularly sensitive to the added concrete shrinkage. The shrinkage induces shear forces in the aforementioned planes. Widening of a 12 m long RC multi-girder bridge span is numerically analysed to assess the influence of the added concrete shrinkage. The analysis results show that: a) in the vertical plane of the connection of the added and the existing deck slab the longitudinal shear due to the shrinkage of the added concrete is comparable with the effect of live load, b) it is necessary to provide appropriate longitudinal reinforcement in the deck slab over the added girders due to tension induced by the shrinkage of the added concrete.

• Restorative Dentistry and Endodontics
• /
• v.34 no.4
• /
• pp.364-370
• /
• 2009

The aim of this study was to evaluate the effect of fiber direction on the polymerization shrinkage of fiber-reinforced composite. The disc-shaped flowable composite specimens (d = 10 mm, h = 2 mm, Aeliteflo A2, Bisco, Inc., IL, USA) with or without glass fiber bundle (X-80821P Glass Fiber, Bisco, Inc., IL, USA) inside were prepared, and the longitudinal and transversal polymerization shrinkage of the specimens on radial plane were measured with strain gages (Linear S-series 350${\Omega}$, CAS, Seoul, Korea). In order to measure the free polymerization shrinkage of the flowable composite itself, the disc-shaped specimens (d = 7 mm, h = 1 mm) without fiber were prepared, and the axial shrinkage was measured with an LVDT (linear variable differential transformer) displacement sensor. The cross-section of the polymerized specimens was observed with a scanning electron microscope to examine the arrangement of the fiber bundle in composite. The mean polymerization shrinkage value of each specimen group was analyzed with ANOVA and Scheffe post-hoc test (${\alpha}$=0.05). The radial polymerization shrinkage of fiber-reinforced composite was decreased in the longitudinal direction of fiber, but increased in the transversal direction of fiber (p<0.05). We can conclude that the polymerization shrinkage of fiber-reinforced composite splint or restoratives is dependent on the direction of fiber.

• Journal of the Korean Wood Science and Technology
• /
• v.33 no.2 s.130
• /
• pp.17-23
• /
• 2005

Juvenile and transitional-juvenile wood samples from loblolly pine (Pinus taeda) were immersed in water to investigate longitudinal and tangential swelling properties. Increment cores from twenty-six loblolly pine trees were sampled at breast height (1.37 m). Earlywood rings 5 and 9 were separated from the core, extracted, oven-dried and immersed in water at room temperature. The variance in longitudinal swell was significant for ring 5 compared to ring 9 (p = 0.001). It was found that tangential swell might predict longitudinal swelling of juvenile wood at ring 9 but not at ring 5. Poor correlation in ring 5 suggests that swelling response in younger juvenile wood may differ. The swell response at ring 5 did not follow the shrinkage models discussed in the literature while ring 9 adhered to the expected curve.

• Journal of Welding and Joining
• /
• v.28 no.4
• /
• pp.41-48
• /
• 2010

The purpose of this study is to establish the control method of the global bending distortion caused by fabrication process of hatch-cover in a container ship. In order to do it, the transitional behavior of global bending distortion in the deck of hatch-cover during fabrication process was measured by 3-dimensional measuring instrument. From the results, the principal factor controlling the global bending distortion was identified as the bending moment associated with the longitudinal shrinkage force and transverse shrinkage caused by welding and flame heating and the change of the centroid axis of hatch-cover in each fabrication process. Therefore, in this study, with the predictive equations of the longitudinal shrinkage force and transverse shrinkage caused by welding and flame heating and the simplified thermo elastic method, the predictive method for the global bending distortion was established and verified by comparing with the measured result. Based on the results, the amount of reverse bending distortion of main stiffeners was determined to prevent the global bending distortion of hatch-cover.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.16 no.5
• /
• pp.19-28
• /
• 2012

In this study, cause of longitudinal crack which is found on duct slab of road tunnel is studied. In-depth investigation, such as visual inspection, non-destructive testing and geometrical surveying of duct slab, is carried out. In order to perform cause analysis, the investigated results are compared to the results of numerical analysis. Many factors, which cause longitudinal crack, are classified as constrained condition of the duct slab, location of the rebar, temperature, shrinkage and so on. According to the classified causes of longitudinal crack, numerical analysis is performed considering construction stage of the tunnel lining. Especially, in order to predict shrinkage stain due to discrepancy of curing date, ACI-209 model, KCI structural design code and other researcher's shrinkage test results are compared. The results show that shrinkage strain is one of the main factors causing longitudinal crack. Other investigated tunnels are classified along with the construction method of duct slab and patterns of cracks. As a result, improving ways to construct duct slab are suggested.

• Journal of Welding and Joining
• /
• v.26 no.3
• /
• pp.23-29
• /
• 2008

The purpose of this study is to propose the proper fillet welding process for preventing the buckling distortion in thin panel welded structure. In order to do it, a heat input model for laser hybrid welding process was developed using FEA and experiment. The principal factors controlling the angular distortion and longitudinal shrinkage force caused by FCA and laser hybrid welding were identified as the welding heat input and weld rigidity using FEA. The predictive equations of angular distortion and longitudinal shrinkage force for each welding process were formulated as a function of the principal factors proposed. With the predictive equations, the buckling distortion at the thin panel welded structure with welding process was evaluated and compared using nonlinear buckling analysis and STEM(simplified thermo elastic method). Based on the results, the best way to prevent the buckling distortion at the given welded panel structures was identified as an intermittent FCA welding.

• Journal of Welding and Joining
• /
• v.25 no.6
• /
• pp.59-63
• /
• 2007

The weld-induced deformation is more serious in thin plates than in thick plates because heat affect zone of thin plates is wider than that of thick plates and in addition internal and external constraints have much more influence upon weld-induced deformation of thin plates. This paper deals with the application of the mechanical tensioning method to butt weld of thin plates to reduce the transverse and longitudinal deformation. In order to investigate the quantitative effect of tensioning method upon the reduction of angular deformation and shrinkage in longitudinal and transverse direction of weld line, butt welding test has been carried out for several thin plate specimens with varying plate thickness and magnitude of tensile load. From the present experimental study, it has been found that the tensioning method is very effective in reducing the weld-induced residual stress as well as the weld-induced deformation.