U-shaped Ribs Research Articles

Damage mechanism of U-shaped ribs stiffened steel flat plates subjected to close-in explosion

The U-shaped ribs stiffened plates are widely used in civil and marine engineering structures for their high bending resistance performance. Moreover, these structures may be exposed to blast scenario especially terrorist and accidental explosions. Based on this background, this investigation carried out a study on the damage modes and the damage mechanisms of the U-shaped ribs stiffened plates subjected to close-in blast loads. The work used both field experimental and numerical methodologies. In this investigation, field blast tests were conducted on two flat plates and a stiffened plate. Furthermore, a fine numerical model was developed on the LS-DYNA platform and validated by the experimental results. Numerical analysis was conducted follow the validated model, and three typical damage modes (five detailed damage modes) of the single U-shaped stiffener stiffened plates subjected to blast loads were revealed through the numerical calculation of 40 specimens. Furthermore, a new damage number (Φ) was proposed for the classification of the damage modes. Meanwhile, maximum incident angle (α) and relative stiffness (κ) were put forward for further identification of the damage modes. It is proven that the damage modes of the single U-shaped stiffener can be well identified by the combination of damage number, maximum incident angle, and relative stiffness. Damage mode I occurred when Φ is less than Φ1 (0.042). And while the Φ is more than Φ2 (0.071), the stiffened plates exhibited mode IIIb damage. For Φ is between Φ1 and Φ2, the damage modes can be classified as mode IIa (κ < 0.0032) and IIb (κ≥ 0.0032) when α is less than 45°. While α is greater than 45°, the damage modes can be classified as mode IIa (κ < 0.001), IIIa (0.001 ≤κ < 0.0032) and IIIb (κ≥ 0.0032).

Mechanical characteristics analysis of the orthotropic steel deck in heavy-haul railway bridges

This paper aims to assess the mechanical characteristics of the orthotropic steel deck (OSD) in heavy-haul railway bridges. Taking the Dongting Lake Bridge as an example, to simulate the transfer effect of the track structure and get mechanical characteristics of the OSD under the service load, the refined segmental finite element model (FEM) of the OSD in a heavy-haul railway bridge was established. Moreover, the Chinese C80 heavy-haul train (the C80) was selected as the applied load to make the analysis results close to the actual situation. And then, the stress influence lines of critical components in OSD were analyzed. Notches at diaphragms of the OSD are more likely to produce stress concentration. Due to the dense distribution and high stiffness of the longitudinal ribs of OSD, the final load influence range of OSD is limited. Since the T-shaped longitudinal ribs (T-Ribs) are located under the position of each rail, and its stiffness is greater than the adjacent U-shaped longitudinal ribs (U-Ribs), so that the T-Ribs are important load-bearing components of the OSD in heavy-haul railway bridges. Furthermore, the influences of the stiffness ratio of T-Rib to U-Rib on the mechanical characteristics of the OSD were analyzed.

Simulation study on fatigue behavior of wrap-around weld at rib-to-floorbeam joint in a steel-UHPC composite orthotropic bridge deck

As an innovative cement-based material, the ultra-high performance concrete (UHPC) has been recently utilized to reinforce the orthotropic steel bridges. Based on an in-situ steel-UHPC composite orthotropic deck bridge, both the field testing and multi-scale finite element analysis modelling were conducted to investigate the fatigue behavior of wrap-around weld at rib-to-floorbeam (RF) joint, and factors influencing stress were further studied to achieve an infinite fatigue life. It is found that a primary tensile stress cycle is jointly produced by the axle group of truck, while a small reversal compressive cycle will be generated when the axle is directly located on the floorbeam. The stress behavior of fatigue detail is extremely sensitive to the localized effect of axle loading instead of entire truck configuration. Since significant stress concentration and high stress gradient exist in the wrap-around weld, it is essential to utilize the hot-spot stress approach rather than nominal stress approach. The wrap-around weld presents an obvious out-of-plane bending deformation, which results from the torsion effect and Poisson’s effect. The Dong’s structural stress reveals that the surface stress is dominated by bending stress. The application of bulkhead can greatly improve the fatigue performance of wrap-around weld. Both the large-scale rib and U-shaped rib are preferable, which are available to achieve an infinite fatigue life without extra fabrication procedure.

Effect of combined U-shaped and semi-circular rib on heat transfer augmentation of solar air heater-A CFD study

This paper presents the numerical analysis on the impact of combined U-shaped rib and semi-circular rib on heat transfer augmentation of flat plate solar air heater system.The analysis is done using the ANSYS Fluent software for various flow Reynolds number ranging from 8000 to 17000. The ribs are placed alternately on the underside of heated plate for a fixed stream-wise pitch of 35mm. The rib height is so chosen that the diameter of semi-circular rib equals the rib height of U-shaped rib. The rib height (e) is varied as 2mm, 3mm and 4mm. The analysis reveals that the combined ribs augment the heat transfer to a maximum extent of about 1.67 times as compared to the smooth duct. Ribs of greater height are found to produce greater enhancement in heat transfer due to increased flow mixing effect. The friction factor is found to increase with rib height and the highest increase is found to be about 1.73 times as compared to smooth duct for Re=8000.

Numerical Simulation and Measurement of Welding Residual Stresses in Orthotropic Steel Decks Stiffened with U-Shaped Ribs

This study aims to investigate the magnitude and distribution of welding residual stresses in orthotropic steel decks stiffened with U-shaped ribs. Numerical simulation of the welding residual stresses is performed using the thermal elastic–plastic finite element method. The residual stresses are subsequently measured using the hole-drilling strain-gage method. Based on the results of this study, it can be determined that: (1) The longitudinal welding residual stresses (σz) in the weld zones are tensile stresses, where the peak value exceeds the minimum yield strength (fyl); however, relatively low compressive stresses exist in the areas located far away from the welds; (2) The stress gradient in the weld zone is steep, and the widths of the areas experiencing tensile stress are narrow; (3) In the case of the upper surface of the deck, the weld that is first deposited has the highest peak stress, while similar stresses are determined for the remaining welds. In the case of the lower surface of the deck, the peak stress in the weld zones is greater than that on the upper surface; (4) In the case of the weld zone of the U-shaped ribs, the tensile stresses reach up to 1.15fyl; however, at locations a short distance away from the welds, the σz varies from tensile to compressive, and finally transforms into a small tensile stress at the base of the U-shaped ribs. In addition, the simulated and measured σz are compared, and the deviation between them is analyzed.

Jet Impingement Heat Transfer Enhancement by U-Shaped Crossflow Diverters

AbstractArray-jet impingement is typically used in gas turbine blade near-wall cooling, where high rates of heat dissipation is required. The accumulated crossflow mass flux results in significant reduction in jet effectiveness in the downstream rows, leading to reduced cooling performance. In this paper, a jet impingement system equipped with U-shaped ribs (hereafter referred as “diverter”) was used for diverting the crossflow away from the jets emanating from the nozzle plate. To this end, a baseline configuration of array-jet impingement onto smooth target surface is considered, where the normalized jet-to-jet spacing (x/dj = y/dj) was 6 and the normalized jet-to-target spacing (z/dj) was 2. Crossflow diverters with thickness t of 1.5875 mm and height h of 2dj (= z) were installed at a distance of 2dj from the respective jet centers. Detailed heat transfer coefficients have been calculated through transient liquid crystal experiments carried out over Reynolds numbers ranging from 3500 to 12,000. It has been observed that crossflow diverters protect the downstream jets from upstream jet deflection, thereby maximizing their stagnation cooling potential. An average of 15–30% enhancement in Nusselt number is obtained over the flow range tested. This benefit in heat transfer came at a cost of increased pumping power to maintain similar flow rate in the system. At a given pumping power, crossflow diverters yielded an enhancement of 9–15% in heat transfer compared with the baseline case.

Thermal performance enhancement of flat plate solar air heater using transverse U-shaped turbulator - A numerical study

The aim of this study is to determine the effect of U-shaped rib turbulator on the flow and heat transfer characteristics of flat plate solar air heater using two dimensional CFD analysis. The analysis is carried out using the CFD software tool ANSYS Fluent for the flow Reynolds number ranging from 9000 to 21,000.The relative pitch(P/e) of the U-shaped rib is varied as 5, 10, 25 and 40 for a fixed relative rib height of 0.0421. It is shown that the U-shaped rib augments the Nusselt number by about 1.76 times while the friction factor increased by about 1.95 times with reference to smooth duct for a relative pitch of 10 and 5 respectively. The maximum thermal enhancement factor is obtained as 1.5 for the configuration of P/e=25. A comparative analysis of U-shaped rib with circular rib reveals that the U-shaped rib turbulator is found to be more effective in providing heat transfer enhancement and has about 15% higher thermal enhancement factor as compared to circular turbulator.

Innovative accelerated construction method for Yushan Bridge, China

To overcome poor construction conditions, shorten construction time and improve project quality, the construction of Yushan Bridge in China is a fully industrialised, based on prefabrication of key components, site installation. The navigation span of the Yushan Bridge has a main span of 260 m and is the world's first segmented precast steel–concrete composite continuous-beam bridge. A new type of steel–concrete composite segment (a girder that connects the concrete box girders and the steel box girders) is used to ensure the bearing capacity and precision of closure. Thickened-edge U-shaped ribs and ultra-high-toughness concrete pavings are employed together to improve the durability of the orthotropic deck. A single-pile and single-column foundation is fully employed, with a maximum diameter of the steel composite pile (a pile that is outside is steel pipe, and the interior is filled with concrete) of 5 m. It is found that the construction time is reduced by 40%, the wave flow force is decreased by 80%, the scouring depth is decreased by 20% and the cost is reduced by 30% compared with group pilings. In addition, this method avoids durability problems of the pile cap due to group pilings. The use of a prefabricated exterior shell with cast-on-site concrete for the interior pier-top blocks of the 50 m non-navigation span solves the problems associated with the bearing force, durability, construction availability and quality control of the pier-top block.

Extraction Method of Crack Signal for Inspection of Complicated Steel Structures Using A Dual-Channel Magnetic Sensor.

Conventional eddy current testing (ECT) using a pickup coil probe is widely employed for the detection of structural cracks. However, the inspection of conventional ECT for steel structures is difficult because of the magnetic noise caused by the nonuniform permeability of steel. To combat this challenge, we have developed a small magnetic sensor probe with a dual-channel tunneling magnetoresistance sensor that is capable of reducing magnetic noise. Applying this probe to a complicated component of steel structures—such as the welds joining a U-shaped rib and deck plate together—requires the reduction of signal fluctuation caused by the distance (liftoff) variations between the sensor probe and the subject. In this study, the fundamental crack signal and the liftoff signal were investigated with the dual-channel sensor. The results showed that the liftoff signals could be reduced and differentiated from the crack signals by the differential parameters of the dual-channel sensor. In addition, we proposed an extraction technique for the crack signal using the Lissajous curve of the differential parameters. The extraction technique could be applied to the inspections not only for flat plates but also for welded angles to detect cracks without the influence of the liftoff signal.

Evaluation Method for Fatigue Life of Bead-Through Crack Initiated from Weld Joint between Deck Plates and U-Shaped Ribs in Orthotropic Steel Deck

Evaluation Method for Fatigue Life of Bead-Through Crack Initiated from Weld Joint between Deck Plates and U-Shaped Ribs in Orthotropic Steel Deck

Fatigue performance of orthotropic steel-concrete composite deck with large-size longitudinal U-shaped ribs

Fatigue damages in orthotropic steel deck have been a thorny problem that perplexed bridge engineers worldwide for decades. Two approaches have been applied to improve the fatigue performance of orthotropic steel decks: (1) to reduce the maximum stress range of structural components by enhancing the local stiffness through use of composite structural systems; (2) to reduce the quantity of fillet welded joints by enlarging the size of longitudinal U-shaped ribs. In this study, a full-scale model test and finite element analysis were conducted to investigate the fatigue performance of an innovative orthotropic steel-concrete composite deck (OSCD) with large longitudinal U-shaped ribs, which represents a combination of the two aforementioned strategies. Orthotropic steel deck and concrete layer are integrated through shear studs that are welded on the steel deck and embedded in concrete. The fatigue failure process of the OSCD structure was investigated, and the effects of damages in concrete and shear studs on the fatigue performance of OSCD were evaluated for the first time. The initiation and development of fatigue cracks were experimentally investigated. The interaction between the mechanical performance of OSCD and the damages caused by cyclic loadings was revealed. Concrete cracks and fracture of shear studs greatly accelerated the degradation of mechanical properties and the development of fatigue failure, and deteriorations of the mechanical properties accelerated the development of damages in concrete and shear studs.

폐단면리브로 보강된 일축압축을 받는 복합적층판의 국부좌굴강도 증가효과

This study is aimed to examine the influence of the rotational stiffness of U-shaped ribs on the local buckling behaviors of laminated composite plates. Applying the orthotropic plates with eight layers of the layup <TEX>$[(0^{\circ})4]s$</TEX> and <TEX>$[(0^{\circ}/90^{\circ})2]s$</TEX>, 3-dimensional finite element models for the U-rib stiffened plates were setup by using ABAQUS and then a series of eigenvalue analyses were conducted. There is a need to develope a simple design equation to establish the rotational stiffness effect, which could be easily quantified by comparing the theoretical critical stress equation for laminated composite plates with elastic restraints based on the Classical laminated plate theory. Through the parametric numerical studies, it is confirmed that there should clearly exist an increasing effect of local plate buckling strength due to the rotational stiffness by closed-section ribs. An applicable coefficient for practical design should be verified and proposed for future study. This study will contribute to the future study for establishing an increasing coefficient for the design strength and optimum design of U-rib stiffened plates.

Development of fatigue test method and improvement of fatigue life by new functional steel plates for welding of trough rib and deck plate of orthotropic decks

Under heavy traffic conditions, some fatigue cracks have been found at welding joints between U-shaped ribs “trough ribs” and deck plates. Fatigue cracks along thickness direction of deck plate from root tip are important because visual crack detection from outside is limited. In this paper, new functional steel plates with initiation resistance of fatigue crack at weldment and propagation resistance at base material are applied to deck plate to evaluate improvement of fatigue life. We conducted fixed-point fatigue tests with real scale partial models consisted with one trough rib and a transverse girder, and the elastic FEM (Finite Element Method) analysis corresponding to the fatigue test specimen. Based on these results, we studied the fatigue properties which focused on the difference between conventional steel plates and newly developed steel plates, FCA (Fatigue Crack Arrester). Fatigue cracks were initiated from root tip of welded joints between a trough rib and a deck plate. It is clarified that FCA steel plates instead of conventional steel plates can improve the fatigue life under the same welding conditions. This improvement effect becomes much clearer in the high cycle region, which is noticeable at the operation and management stage of bridges.

폐단면리브 강성에 따른 일축압축을 받는 보강판의 국부좌굴강도 평가

Generally, structural plates under axial compression should be stiffened by longitudinal stiffeners in order to enhance the buckling strength. Though U-shaped ribs would be more efficient for the stiffened plate system, there is in the absence of a proper design guides or relevant research results. Thus this study is aimed to examine the local buckling behavior of stiffened plates with U-section ribs. 3-dimensional analysis models which include 3 types of U-shaped longitudinal stiffeners were simulated by using the finite element code ABAQUS. The bifurcation analysis were conducted and then the buckling analysis results are compared with the theoretical equation values. It is found that the rotational constraint effect provided by the U-ribs should increase the local buckling strength. Some features drawn from a series of parametric study results are summarized.

Influence of Press Reforming in Fabrication Process on Stress Properties of Welded Joint between Deck Plate and U-shaped Rib in Orthotropic Steel Decks

Influence of Press Reforming in Fabrication Process on Stress Properties of Welded Joint between Deck Plate and U-shaped Rib in Orthotropic Steel Decks

In-plane ultimate compressive strengths of HPS deck panel system stiffened with U-shaped ribs

AbstractThe ultimate compressive strengths of deck plates stiffened longitudinally by U-shaped stiffeners have been investigated by the nonlinear finite element analysis (FEA). A total of 112 hypothetical models with various combinations of slenderness parameters for the deck plates and column slenderness parameters for the stiffeners were modeled and analyzed. Both conventional and high performance steels were considered in models following elasto-plastic strain hardening constitutive relationships. Initial geometric imperfections and residual stresses were also incorporated in the FEA. Numerical results from FEA have been compared to compressive strengths from Eurocode 3 EN 1993-1-5, FHWA-TS-80–205, and other available formulas. Based on analysis results, new unified strength predictor equations have been developed for the stiffened plate systems with conventional steel and/or high performance steel (HPS). It has been found that use of Eurocode 3 EN 1993-1-5 and FHWA-TS-80–205 may lead to highly conservative design when large column slenderness parameters are encountered. The proposed equations have simple forms yet provide accurate strength predictions resulting in more economic design.

축방향 압축을 받는 폐단면리브로 보강된 복합적층판의 좌굴 해석연구

압축을 받는 복합적층판의 보강을 위해 폐단면리브를 적용하는 것이 효과적이나, 적정 크기나 최적 두께에 대한 충분한 연구자료가 제시되지 못하고 있다. 이에 따라 폐단면리브 단면 제원에 따른 복합적층판의 압축좌굴 거동에 대한 영향이 우선 검토되어야 할 필요성이 있다. 본 논문에서는 직교이방성 <TEX>$[(0^{\circ})_4]_s$</TEX>와 Cross-ply <TEX>$[(0^{\circ}/90^{\circ})_2]_s$</TEX> 적층단면을 각각 고려하여 U리브 단면강성에 따른 복합적층 보강판의 탄성좌굴강도 및 좌굴모드의 변화를 수치해석적으로 검토하였다. 구조부재로써 적용성을 고려하여 U리브 단면 모델을 선정하였고 유한요소해석 프로그램인 ABAQUS를 이용하여 U리브 적층두께에 따른 고유치 해석을 실시하였다. U리브와 같은 폐단면 보강재를 적용한 복합적층판에서는 단순지지 조건의 판좌굴 강도에 비해 상승효과가 있음이 본 연구의 수치해석 결과로부터 입증되었으며 본 해석연구 대상 모델에 대해 U리브 최적 적층두께를 분석하였다. 본 논문의 연구 결과는 향후 U리브의 최적 단면 선정방안을 제시하는데 기여할 수 있을 것으로 기대된다. Even though the longitudinally stiffened laminated composite plates with closed section ribs should be an effective system for axially compressed members, the existing researches on the applications of closed-section ribs, especially for the laminated composite plates, are not sufficient. This study is aimed to examine the influence of the sectional stiffness of U-shaped ribs on the buckling modes and strengths of laminated composite plates. Applying the orthotropic plates with eight layers of the layup <TEX>$[(0^{\circ})_4]_s$</TEX> and <TEX>$[(0^{\circ}/90^{\circ})_2]_s$</TEX>, 3-dimensional finite element models for the U-rib stiffened plates were setup by using ABAQUS and then a series of eigenvalue analyses were conducted. From the parametric studies, the minimum required ply thicknesses as well as the buckling strengths were presented for the analysis models. The buckling strengths were compared with the theoretical critical stress equation for simply supported plates based on the Classical laminated plate theory. This study will contribute to the future study for evaluating the minimum required stiffness and optimum design of U-rib stiffened plates.

축방향 압축을 받는 폐단면리브 보강판의 좌굴거동에 관한 해석적 연구

Even though the longitudinally stiffened plates with closed section ribs should be an effective system for axially compressed members, the current design speculations on closed-section rib, especially for the minimum required stiffness, are not sufficient. This study is aimed to examine the influence of the sectional stiffness of U-shaped ribs on the buckling modes and strengths of stiffened plates. Applying three kinds of U-ribs, 3-dimensional finite element models for the U-rib stiffened plates were setup by using ABAQUS and then a series of eigenvalue analyses were conducted. From the parametric studies, it was found that the minimum required stiffness as well as the buckling strengths are varied along with the U-rib types. The buckling strengths were compared with the theoretical critical stress equation for simply supported plates. This study will contribute to the future study for evaluating the minimum required stiffness and optimum design of U-rib stiffened plates.

Mechanical Analysis for the Deck Pavement of Long-Span Steel Bridge

The mechanical analysis is applied for the steel box girder bridge with orthotropic plate and pavement by means of Finite Element Method. The interaction between steel bridge and pavement on the long-span steel bridge is evaluated in three calculation stages. The emphasis of the analysis includes the mechanical characteristics and the influential factors of large components(cross diaphragm)and local components (U-shaped ribs). Considering the mechanical changes by the load of heavy-duty vehicles and heavy load with braking, the interfacial shear failure is studied for the main form of damage. In view of this major form of damage, this paper puts forward the corresponding mechanical analysis of the indicators.

Local Stress Analysis of Orthotropic Steel Bridge Decks in High-Speed Railway

Orthotropic decks are commonly used in high-speed railway bridges. Finite-element model is established by ANSYS for orthotropic steel bridge deck in this paper. Taking the standard PDL ZK live load as the train load, the local stress of the rib-to-deck joint, the rib-to-crossbeam joint, and the cut-outs of the crossbeam are analyzed respectively. Analysis results show that the stress concentration of bridge deck mainly appears at the intersecting part of the U-shaped rib, crossbeam, and bridge deck. In the whole bridge deck, the local stress level of the cut-outs in crossbeam is almost the highest, and the cut-outs is distorted seriously; the maximum stress of crossbeam cut-outs is mainly concentrated at the lower arc of the cut-outs, which is one of the positions prone to fatigue failure.