Slab Width Research Articles

Effect of uneven solidification on the quality of continuous casting slab

Solidification during slab continuous casting is of importance to the quality of steel products. Non-uniform cooling often occurs during slab continuous casting, leading to uneven solidification rate at different locations, especially that along the slab width direction. Considering the realistic cooling intensity along all directions, the effect of uneven solidification on steel quality was discussed. Results indicated that, uneven solidification caused by non-uniform cooling would induce defects like shrinkage cavities, segregation and cracks. Due to the uneven solidification, long-narrow solidification ends would form. At the long-narrow solidification ends, high solid phase fraction inhibited the movement of liquid steel and the supplement of solidification shrinkage, leading to serious partial segregation and shrinkage cavities. The irregular solidification end went against the application of dynamic soft reduction technology as well. Furthermore, uneven solidification would lead to high temperature gradient and high thermal stress in the solidified shell, resulting in cracks in the slabs. Defects in the slab, especially the centre macro-segregation and centre shrinkage cavities, were reduced by optimising the spray nozzle arrangement of the continuous caster.

횡력을 받는 넓은 보-기둥 내부 접합부의 거동 평가

횡력을 받는 넓은 보와 기둥 내부접합부의 거동을 평가하기 위하여 넓은 보-기둥 접합부의 휨강성비와 유효폭 및 슬래브 유무를 변수로 6개의 1/2축소 모델 실험체를 제작하여 구조성능 평가를 수행하여 하중-변형, 연성, 강성 등을 평가하였다. 동 모델을 대상으로 비탄성해석을 수행하여 구조성능평가 결과와 비교하였다. 연구결과 도출된 결론은 다음과 같다. 넓은 보-기둥 내부 접합부는 중진지역인 국내에서 적용하고 있는 부분골조형 구조에 적용이 가능한 것으로 판단된다. 슬래브의 강성이 횡력을 받는 넓은 보-기둥 내부 접합부의 거동에 영향을 미치는 것으로 나타났다. 휨강성비가 2.0이상의 경우 T형보의 플랜지로서 슬래브 유효폭은 넓은 보 유효깊이의 2.0d로 평가되며, 휨강성비가 1.4~2.0일 경우, 슬래브 유효폭의 영향은 고려하지 않아도 되는 것으로 나타났다. An experimental investigation was conducted to study the behavior of RC wide beam-column joints with slab subjected to reversed cyclic loads under constant axial load. Six half scale interior wide beam-column assemblies representing a portion of a frame subjected to simulated seismic loading were tested, including three specimens without slab and three specimens with slab. The primary variables were the ratio of column-to-beam flexural capacity (<TEX>$M_r={\Sigma}M_c/{\Sigma}M_b$</TEX> ; 0.77~2.26), ratio of the column-to-beam width (b/H ; 1.54, 1.67). Test results are shown that (1) the current design code and practice for interior joints(type 2) are apply to the wide beam-high strength concrete column. (2) the presence of a slab have an effect on the performance of the wide beam-high strength concrete column interior joints(type 2). therefore in the design of the wide beam-high strength concrete column interior joints(type 2), the width of slab effective as a T beam flange should be considered. It was show that the case of the ratio of column-to-beam flexural capacity is more than 2.0, the effective width of slab are 2 times of an effective depth of wide beam, however if the ratio of column-to-beam flexural capacity is 1.4~2.0, the effective width of slab are not able to be considered.

Seismic analysis of CFST frames considering the effect of the floor slab

This paper describes the refined 3-D finite element (FE) modeling of composite frames composed of concrete-filled steel tubular (CFST) columns and steel-concrete composite beams based on the test to get a better understanding of the seismic behavior of the steel-concrete composite frames. A number of material nonlinearities and contact nonlinearities, as well as geometry nonlinearities, were taken into account. The elastoplastic behavior, as well as fracture and post-fracture behavior, of the FE models were in good agreement with those of the specimens. Besides, the beam and panel zone deformation of the analysis models fitted well with the corresponding deformation of the specimens. Parametric studies were conducted based on the refined finite elememt (FE) model. The analyzed parameters include slab width, slab thickness, shear connection degree and axial force ratio. The influences of these parameters, together with the presence of transverse beam, on the seismic behavior of the composite frame were studied. And some advices for the corresponding seismic design provisions of composite structures were proposed.

Study on the Effective Slab Width of Composite Cable-Stayed Bridge under Axial Force

There exist evident shear-lag phenomena in large-span composite cable-stayed bridges under the action of axial force, especially in the deck with double main girders. In order to discuss the distribution law of the effective flange width coefficient along the span, caused by axial force, finite element computations of five composite cable-stayed bridges and theoretical analysis have been performed. The transmission angle of axial force caused by the axial compression of stay cables was given, meanwhile the formulas for computation effective slab width coefficient under axial force were suggested.

Optimization of the Mach–Zehnder modulator using polymer asymmetric rib waveguide

In order to shorten the branch length of Mach–Zehnder modulator, the asymmetric rib waveguide was researched in Mach–Zehnder electro–optic polymer modulator. Full vector finite difference beam propagation method was applied to analyze systematically their transmission loss with different parameters. The structure was optimized by choosing optimal design solution such as the rib width w=4μm, the branch height g=11μm, the outer slab width of core layer in bending waveguide s=2μm and the length of the sine-bending waveguide L1=350μm. The results show that if symmetric rib waveguide is replaced by asymmetric rib waveguide, the length of branch waveguide could be reduced by 30% under the same conditions of transmission loss. The results will have a certain reference value to the design of polymer optical waveguide in M–Z modulator.

Determination of CC slab solidification using nail shooting technique

The technology of nail shooting was improved and used to study the transverse shape of the solidified shell during steel continuous casting. Three locations across the slab width (1/2, 1/4 and 1/8) were measured by nail shooting and which indicated a larger solidification coefficient and longer liquid core in the slab at higher casting speeds. The solidified shell across the slab width direction was non-uniform due to uneven secondary spray cooling. The point of final solidification at locations 1/8 and 1/4 was much longer than the position between the slab centre and location 1/4, leading to a long solidification end of >2 m, which is poor for the application of dynamic soft reduction. A mathematical model was developed to simulate the growth of the solidified shell and which was in good agreement with the measurements measured by nail shooting. Based on the measurements and simulations, the water spray pattern was improved, making the solidified shell more uniform. Dynamic soft reduction was then optimised resulting in reduced centreline segregation.

Research on the finite element simulation of and updating method for old riveted truss bridges

AbstractFinite element modelling to establish the actual mechanical performance of very old riveted truss bridges with complex configurations is essential for the sake of accurately assessing their remaining service life and their safety. This paper describes a study on finite element simulation and its updating for the 104‐year‐old Waibaidu Bridge in Shanghai. First of all, a solution is proposed for structural simulation problems as the shear deformation of built‐up members, gusset plate rigid field and relevant cracks as well as the concrete slab’s composite action. The area loss of the main truss members and the actual effective width of the concrete slab are identified as key factors after error analysis for actual performance modelling, considering several causes such as second‐order effects, shear deformation, corrosion and the composite action of the concrete slab. Afterwards, the dual‐stage model updating method is tailored to old riveted truss bridges, which modifies structural stiffness through static load testing in the first step and then calibrates mass distribution through vibration testing. The research shows that: 1) dual‐stage finite element simulation is effective; 2) the shear deformation effect should be taken into consideration for latticed members, and the influence of second‐order effects and shear deformation should be also taken into account when bridge lateral response is involved, while the errors of composite parameters of concrete slab can never be neglected; and 3) corrosion modelling for truss members and crack monitoring for gusset plates have little significance on the finite element simulation and updating of old riveted truss bridges.

Magnetic superlens-enhanced inductive coupling for wireless power transfer

We investigate numerically the use of a negative-permeability “perfect lens” for enhancing wireless power transfer between two current carrying coils. The negative permeability slab serves to focus the flux generated in the source coil to the receiver coil, thereby increasing the mutual inductive coupling between the coils. The numerical model is compared with an analytical theory that treats the coils as point dipoles separated by an infinite planar layer of magnetic material [Urzhumov et al., Phys. Rev. B 19, 8312 (2011)]. In the limit of vanishingly small radius of the coils, and large width of the metamaterial slab, the numerical simulations are in excellent agreement with the analytical model. Both the idealized analytical and realistic numerical models predict similar trends with respect to metamaterial loss and anisotropy. Applying the numerical models, we further analyze the impact of finite coil size and finite width of the slab. We find that, even for these less idealized geometries, the presence of the magnetic slab greatly enhances the coupling between the two coils, including cases where significant loss is present in the slab. We therefore conclude that the integration of a metamaterial slab into a wireless power transfer system holds promise for increasing the overall system performance.

차원 해석을 이용한 수직압연에 대한 도그본 형상 예측

Precision control of the width of slabs is vital for product quality and production economy in steel rolling mills. However, the formation of so called `dog-bone` at the edge of the slab would affect the final width during the horizontal rolling that follows. Therefore, it is essential to predict and control the dog-bone shape. In this paper, a model is derived by using a number of finite element simulations for edge rolling and a least square regression analysis. The prediction accuracy of the proposed model is examined by comparing the predictions from finite element simulation with experiment results in the literature.

MR perfusion imaging by alternate slab width inversion recovery arterial spin labeling (AIRASL): a technique with higher signal-to-noise ratio at 3.0 T

To propose a new arterial spin labeling (ASL) perfusion-imaging method (alternate slab width inversion recovery ASL: AIRASL) that takes advantage of the qualities of 3.0T. AIRASL utilizes alternate slab width IR pulses for labeling blood to obtain a higher signal-to-noise ratio (SNR). Numerical simulations were used to evaluate perfusion signals. In vivo studies were performed to show the feasibility of AIRASL on five healthy subjects. We performed a statistical analysis of the differences in perfusion SNR measurements between flow-sensitive alternating inversion recovery (FAIR) and AIRASL. In signal simulation, the signal obtained by AIRASL at 3.0 and 1.5T was 1.14 and 0.85%, respectively, whereas the signal obtained by FAIR at 3.0 and 1.5T was 0.57 and 0.47%, respectively. In an in vivo study, the SNR of FAIR (3.0T) and FAIR (1.5T) were 1.73±0.49 and 1.02±0.20, respectively, whereas the SNRs of AIRASL (3.0T) and AIRASL (1.5T) were 3.93±1.65 and 1.34±0.31, respectively. SNR in AIRASL at 3.0T was significantly greater than that in FAIR at 3.0T. The most significant potential advantage of AIRASL is its high SNR, which takes advantage of the qualities of 3.0T. This sequence can be easily applied in the clinical setting and will enable ASL to become more relevant for clinical application.

A Parametric Study of the Reinforced Concrete Slab Subjected to Dynamic Excitation

The width of effective slab to estimate the beam flexural strength at the beam ends in structures subjected to lateral loading, such as earthquake, is not explicitly addressed in design codes. As a result, designers often ignore the contribution of floor slabs to the lateral load resistance. There is a need for a simple model to assess the slab contribution to beam strength for analysis and design. General expressions for the yield loading and stiffness characteristic of the slab element have been developed which is more sensitively depend on yield line theory beside other parameters such as spacing, yield strength, area of reinforcement, and the span length. A model considering beam growth, bending effects and the slab effect is being considered in the present work. The results of the analytical investigation are compared with experimental results. The slab element model is then used to conduct a parametric study aiming to investigate the effect of the distribution and strength of the slab steel. It is shown that the performance of the unit is directly related to this steel.

Mechanical properties of precast reinforced concrete slab tracks on non-ballasted foundations

This article deals with the mechanical properties of steel-reinforced concrete precast slab tracks on non-ballasted elasto-plastic foundations. To work out the spanning behavior of slab tracks, a FEM analysis was executed for discrete and continuous systems. At first, full-size slabs without foundation including solid and hollow-core specimens (with 30% weight reduction) were tested under centric static (monotonic) line loads, and load–deflection curves were extracted. Then, FEM results for zero foundation stiffness were verified with those of experiments, which were in good agreement. Original results include the effects of several parameters on the cracking load, ultimate load, and energy absorption of slabs placed on elasto-plastic foundations including the slab width, concrete tensile strength and load factor. Analyses revealed that mechanical properties in hollow-core sections are not so different from those in solid ones, and thus hollow-core sections are more efficient because of significant weight reduction.

Optimal control of secondary cooling for medium thickness slab continuous casting

A software to simulate the solidification, heat transfer and water flowrate distribution in slab continuous casting was developed by establishing a mathematical model for the heat transfer and solidification in medium thickness slab casting. This model was validated by pin shooting and surface temperature measurement experiments. A reasonable target surface control temperature was found by testing the high temperature mechanical properties of Nb bearing ship plate steel, and then the water flowrate of each loop of the secondary cooling zone was determined by the software. The influence of uneven secondary cooling in the slab width direction on the quality of the slab was also investigated, which provided data for the optimisation of the secondary cooling of the slab caster. On the basis of the above research, an optimisation scheme for a secondary cooling system was proposed. Experimental results showed that the quality of the slab was significantly improved after optimisation. The centreline macrosegregation was reduced, and the ratio of equiaxed grains was increased by 3·18%. In addition, the transverse cracking of the slab was almost eliminated.

The Experimental Investigation of Slab Participation in Flexural Behavior of Beams under Two-Way Loading

The paper designed three joints namely beam-column joint of reinforced concrete frame without slab and two beam-column joints of reinforced concrete frame with slab, using different loading methods (one direction and two directions) to experiment. The paper studied failure behavior, load-carrying capacity, and slab participation in flexural behavior of beam under different loading modes. Experiment shows that for the joints with slab, flexural capacity at end of the beam under two direction loads than one direction loads lows by about 10%; under one direction load, effective flange width of slab should be taken 8 times thickness, under two direction loads, effective flange width of slab should be taken 10 times thickness.

Analysis of Distribution of Nonmetallic Inclusions in Aluminum DC-Cast Billets and Slabs

Inclusion distribution was studied in commercial aluminum DC-cast billets and slabs using a newly developed deep-etching method. Analyses revealed a nonuniform distribution of nonmetallic inclusions across billet diameters and lengths, and also across slab thicknesses and widths. In as-cast billets, more inclusions were found at the beginning and end of the billet length; more were present near the cross-section center than near the surface. In slabs, inclusions were located mostly within 13 mm of the surface and in a band between the centerline and the surface. Few inclusions were found 60 to 100 mm from the slab surface or at the centerline. In addition, comparing slab quality after casting using three types of ceramic foam filters (CFFs; i.e., 30 ppi, 50 ppi, and 50 ppi + HF) revealed significant differences in inclusion size, number, and distribution. Casting slabs using a finer pore-size filter (50 ppi) reduced the number of non-metallic inclusions greatly. The inclusion distribution patterns observed in the solidified slabs are discussed in terms of melt flow during casting.

Influence of Structural Parameters on Mechanical Properties of Double-Block Ballastless Track

A high degree of integrity is the most remarkable feature that makes double-block ballastless track different from other ballastless track structure. Based on the beam/plate theory on elastic foundation, influences of several structural parameters (such as size of track slab and support layer, support stiffness of the subgrade, etc) on stress of the ballastless track system under the axle load of 300kN were studied in order to obtain further understanding of the mechanic performance of double-block ballastless track under the train load. Results show that: structure of double-layer combined structure should be adopted to decrease the stress of each layer of ballastless track; the width of support layer should be less than 3.6m; because the ratio of track slab stress to support layer stress is larger than the ratio of their strength, the width of track slab in the double-layer separated structure should be 280mm or less.

Resonant transparency of a two-layer plasma structure in a magnetic field

Transparency of a two-layer plasma structure in an external steady-state magnetic field, perpendicular to the wave incidence plane, is studied. The case of the p-polarized electromagnetic wave is considered. The electromagnetic wave is obliquely incident on the two-layer structure and is evanescent in both layers. The conditions for total transparency of the two-layer structure are found. The parametric dependencies of the transparency coefficient on the plasma slab widths, the magnitude of the wave number component, as well on the magnetic field magnitude are obtained.

Crack Resistant Performance and Crack Width of one-Way Slabs Strengthened with FRP

Based on the tests of six reinforced concrete slabs strengthened with fibre reinforced plastic (FRP) sheets and one reference slab without the sheet, the influences of factors such as type of FRP sheets (CFRP and GFRP), amount of FRP sheets and strengthening scheme upon the crack resistant performance were presented and discussed in this paper. In the end, a calculation method was put forward, which can be used to calculate cracking moment and crack width in reinforced concrete slabs strengthened with FRP sheets.

Effective Flange Width for Composite Steel Beams

The effective flange width is a concept proposed by various codes to simplify the computation of stress distribution across the width of composite beams. Questions have been raised as to the validity of the effective slab width provisions, since they have a direct effect on the computed ultimate moment as well as serviceability limit states such as deflection, fatigue, and overloading. The objective of this paper is to present results from an experimental and analytical investigation to determine the effective slab width in steel composite beams. The Finite Element Method (FEM) was employed for the analysis of composite steel-concrete beams having variable concrete flange widths. Results were compared to those from tests performed on eight beams loaded to failure. Beam test specimens had variable flange width and various degrees of composite action (shear connectors). The comparison presented in terms of the applied load versus deflection, and strain in the concrete slab show that the AISC-LRFD code is conservative and underestimates the width active. Based on a detailed parametric study an equation for the calculation of the effective flange width is recommended.

Research on Deflection and Stress of CRCP under Concentrated Vehicle Load over Hollow Base

Based on the small deflection theory of elastic thin plate and the equivalence principle of deflection and stress, the concentrated vehicle load which acts on the CRCP is translated into the equivalent half-wave sine load by Fourier transform. On the basis of this transform, the deflection and stress formulas are put forward when CRCP is subjected to a concentrated vehicle load with hollow foundation. The following results are obtained from the analysis. The maximal deflection is proportional to the concentrated vehicle load and slab width, and inversely proportional to the lateral bending stiffness and slab thickness. The slab width and thickness have a significant influence on the maximal deflection. The maximal stress is proportional to the concentrated vehicle load and slab width as well as inversely proportional to the slab thickness. The influence of slab thickness is significant to the maximal stress. In conclusion, increasing the slab thickness is the preferential choice to reduce the maximal deflection and stress.