Tube Section Research Articles

Experimental analysis of BFRP strengthened short steel tube with built-in FBG sensors under axial compression

This paper presents the results of an experimental investigation of the behavior and strain-sensing characteristics of short tubes strengthened by basalt fiber-reinforced polymer (BFRP) with built-in fiber Bragg grating (FBG) sensors. This study introduces a corrugated steel with punched-in patterns to improve the buckling failure mechanism of thin-walled circular hollow section (CHS) tubes. Thirty-five specimens are tested under axial compression to investigate the effects of the BFRP strengthening and the punched-in. The self-sensing properties of the built-in FBG sensors are analyzed using wavelength shift data gathered from nine additional specimens. The results demonstrate that the punched-in patterns and the BFRP can significantly enhance the strength of CHS tubes by 98% for 0.7 mm and 36% for 1.2 mm using 2 layers of BFRP. The built-in FBG sensors fulfill the demand for intelligent monitoring of FRP strengthened steel tubes. Analysis on design rules revealed that the interaction between the punched-in patterns and the BFRP must be further considered to accurately predict the compressive capacity of the proposed tubes. Finally, the innovative tubes display potential benefits in terms of cost and weight performance to replace traditional steel tubes.

Effect of Flow Direction on a Double‐Duty Microreactor for Coproduction of Aniline and Hydrogen

AbstractA new thermally coupled microreactor, which simultaneously produces hydrogen and aniline, is simulated. It is suggested that the nitrobenzene hydrogenation process, the heat source, occurs in the tube section, thereby providing the requisite energy for the reactor system. Conversely, the shell section contains the steam reforming of glycerol coolant for the exothermic reaction. The results are evaluated in the two flow directions, namely, cocurrent and countercurrent. The furnace and cooling system, vital for the conventional steam reforming and aniline production processes, are eliminated, respectively, having accurately implemented the sensitivity analysis. Optimization of the most effective parameters is performed via genetic algorithm.

Behaviour of buckling-restrained steel plate shear wall with concrete-filled L-shaped built-up section tube composite frame

To improve the space utilisation rate and seismic performance of high-rise buildings, a new seismic structural system, this paper proposes a buckling-restrained steel plate shear wall (SPSW) with a concrete-filled L-shaped built-up section tube composite frame. In this composite shear wall system, the columns in the frame are composed of hot-rolled carbon steel H-section members and carbon steel square hollow section tubes, which are connected by steel plates and filled with concrete, and the SPSW is comprised of an embedded steel plate and several pairs of cold-formed steel hat-section buckling-restraining strips. To study the seismic performance of this new type of shear wall system, two specimens were prepared and tested under a horizontal cyclic load. The test results showed that the two specimens had a high bearing capacity, good ductility, and good energy dissipation capacity. This indicated that the new shear wall system was reliable and effective at resisting lateral forces. Finite element models were established and validated against experimental results. Based on the results of a parametric analysis, a value of 0.85 was proposed for coefficient η to modify the method based on the plate–frame interaction theory, which could be used to calculate the bearing capacity of the buckling-restrained SPSW with the concrete-filled L-shaped built-up section tube composite frame.

Seismic Performance Evaluation According to HSS and CFST Columns of 3D Frame Buildings with Rubber Friction Bearing (RFB).

This study has been conducted to observe nonlinear time history analysis of a 3D-office building frame where performance has been examined in the presence of base isolation and a bracing system. This steel structure has an underground story surrounded by stiff well-graded sand and is assumed to be located in an intense seismic area. The static and dynamic experimental performance of a Rubber Friction Bearing (RFB) has been considered, and an equivalent numerical model has been used in finite element software, which provides a satisfactory relationship between experimental and numerical prediction. The results show that the story drift and post-earthquake damage of the frame reduced significantly due to the presence of RFB devices. These isolators are most effective in moderate earthquakes. The presence of a minimum number of Steel Buckling Restrained Braces (BRBs) systems improve structural performance under moderate and strong ground motions by reducing story drift and residual damage. Hollow Steel Section (HSS) and Concrete-Filled Steel Tube (CFST) sections have been used in the simulation process, and it was found that the HSS system is susceptible to damage even if both seismic protection systems have been considered. The findings provide important conclusions to select suitable seismic protection for this type of structure, which is limited by simulation study due to the absence of experimental observation.

Entropy generation and thermal analysis of nanofluid flow inside the evacuated tube solar collector

In the current investigation, the thermal and thermodynamic behavior of a buoyancy-driven evacuated tube solar collector (ETSC) has undergone precise evaluation, and the efficacy of nanoparticle dispersion in the testing fluid was scrutinized. The natural convection process was analyzed in different vertical sections of the absorber tube. The outputs for water and the utilized nanofluid were compared at various cutting planes along the tube during the simulation time. In this problem, CuO nanoparticles with optimum thermal properties were distributed in the base fluid. According to the surveyed results, the temperature distribution analysis illustrates that the mean wall temperature experiences more enhancement when the nanofluid is used. The comparison of the heat transfer coefficient between the two simulated cases show the competency of utilizing CuO-{mathrm{H}}_{2}mathrm{O} nanofluid and highlight its crucial character in improving the thermal treatment of the operate fluid through the collector pipe. Based on irreversibility assessment, the irreversibility due to fluid friction rises when the nanofluid is applied during the flow time. In contrast, the entropy generation of pure water owing to heat transfer surpasses the case with nanofluid. More specifically, the heat transfer entropy generation experience a reduction of about 6.3% (0.143–0.134 W/K) by utilization of CuO with a volume fraction of 5% after 1 h of flow time, whereas the entropy generation by fluid viscosity enhances up to 23% when the nanofluid is applied in the system. The irreversibility originated from heating and fluid viscosity has significant difference in value, owing to the fluid’s low-velocity range in the natural convection process.

Three-Dimensional Finite Element Modelling of Sheet Metal Forming for the Manufacture of Pipe Components: Symmetry Considerations

The manufacture of parts by metal forming is a widespread technique in sectors such as oil and gas and automotives. It is therefore important to make a research effort to know the correct set of parameters that allow the manufacture of correct parts. This paper presents a process analysis by means of the finite element model. The use case presented in this paper is that of a 3-m diameter pipe component with a thickness of 22 mm. In this type of application, poor selection of process conditions can result in parts that are out of tolerance, both in dimensions and shape. A 3D finite element model is made, and the symmetry of the tube section generated in 2D is analysed. As a novelty, an analysis of the process correction as a function of the symmetrical deformation of the material in this case in the form of a pipe is carried out. The results show a correct fitting of the model and give guidelines for manufacturing.

Research on Influence Factors of Bearing Capacity of Concrete-Filled Steel Tubular Arch for Traffic Tunnel

When a traffic tunnel passes through special strata such as soft rock with high geo-stress, expansive rock, and fault fracture zones, the traditional supporting structure is often destroyed due to complicated loads, which threatens the construction and operation safety of tunnel engineering. Concrete-filled steel tubular (CFST) structure gives full play to the respective advantages of steel and concrete and has better bearing capacity and economic benefits than traditional support structure, which has achieved good results in some underground engineering applications. In order to promote the application of CFST in the construction of traffic tunnels with complex geological conditions and improve the bearing capacity of the initial supporting structure of tunnels, the influencing factors of the bearing capacity of CFST arch were studied by numerical simulation. The main achievements are as follows: (1) The load-displacement curves of CFST members under different material parameters are basically consistent. CFST members have significant restrictions on displacement in the elastic stage and have high ultimate bearing capacity. Although the bearing capacity decreases obviously after reaching the peak, it shows good extension performance. (2) The height of the steel tube section, the thickness of the steel tube wall and the grade of the core concrete have an approximately linear positive correlation with the bearing capacity of CFST arch, but the influence of these three factors on the bearing capacity of CFST arch decreases in turn, and when the grade of core concrete increases above C50, it has no significant effect on the bearing capacity of members.

Tensile and flexural behaviors of connections between steel beam and concrete-encased-and-filled steel tube column

Concrete-encased-and-filled steel tube (CEFT) columns with a circular tube section can be potentially used for hollow precast concrete (PC) constructions, in which thin PC encasement is used to reduce the lifting weight of a large PC column. In the present study, connection methods were studied for steel beam-CEFT column joints with the thin concrete encasement. Two sets of testing were performed focusing on the local behavior of the connection: 1) monotonic tension test for beam flange-column connections, and 2) cyclic loading test for beam-column joints. In the first test, the local out-of-plane behavior of the flange plate-tube connections and the associated damage mode of the concrete encasement were identified. The load-deformation relationships of the test specimens were evaluated by nonlinear finite element analysis. Based on the results, exterior beam-column joint specimens were designed, and the flexural behavior of the connections was verified under cyclic loading. The joint specimens were strengthened with connection methods such as tension bars, thick steel tube, and vertical continuity plate, inducing the beam failure. In particular, the thick tube and vertical continuity plate were effective in restraining the concrete damage. The tensile and flexural strengths of the test specimens were evaluated using design equations.

Heat transfer and exergy destruction analyses with ferrofluid in LS-3 solar collector under dipole magnetic field

The parabolic trough solar collector is one of the most advanced technologies for employing solar energy. In these collectors, parabolic mirrors concentrate the sun rays on the absorber tube. In this article, performance improvement of parabolic trough solar collector (LS-3 solar collector) is studied by means of multiple line dipoles magnetic field. The non-uniform magnetic field created is perpendicular to the direction of motion of the fluid. Ferrofluid is used as a working fluid as well as to improve heat transfer properties. Monte Carlo Ray Tracing (MCRT) is used to ascertain the heat flux on the receiver’s absorber tube. The exergy destruction and entropy generation are calculated using the second law of thermodynamics, and convective heat transfer coefficient is obtained for evaluating the performance of solar collector. In case of using multiple line dipoles, heat transfer and exergy destruction will increase and decrease, respectively. By applying external force, a secondary flow is created in the cross section of the absorber tube. Moreover, if the Fe3O4 nanoparticles are added to Therminol® VP-1, it will result in reducing the exergy destruction and improving the heat transfer. Also, with increasing ferrofluid velocity, frictional entropy and thermal entropy increase and decrease, respectively.

Experimental and Numerical studies on the Heat transfer characteristics of Small Shell and Tube Heat Exchanger

This work presents the experimental and numerical investigations on the effectiveness of a small shell and tube heat exchanger for different coolant combinations. A numerical investigation is done using commercial computational tool, Fluent, to analyze heat transfer characteristics for the selected coolant combinations. The coolant combinations used consists of ethylene glycol (EG) and deionized water (DW) with varied percentages of the former. Accordingly, combination of ethylene glycol (EG) and deionized water viz, 60EG:40DW, 30EG:70DW and 20EG:80DW were used. The base fluids of EG and DW were used for the comparison of heat transfer characteristics, respectively with the selected coolant combination. For the numerical investigations, the CAD model of counter flow heat exchanger with 0 degree inclined baffles; with cold liquid flowing through the shell at the rate of 0.3 kg/s while hot liquid flows through the copper tubes at a flow rate of 0.3 kg/s was considered. Different combinations of shell-tube liquid are analyzed for identical initial and boundary conditions, keeping all other Fluent parameters the same. The temperature contours are generated for all the five cases. The temperature distribution for different shell-tube liquid combinations are compared for evaluating the effectiveness of heat exchange.Improved heat exchange is ensured with higher temperature difference between inlet and outlet of shell/tube, and respective combination of shell and tube fluid is selected for industrial cooling applications. Results of CFD approach are validated with the experimental results and results are acceptable. From the results it is found that 60EG:40DW combination showed improved heat transfer characteristics compared to other combinations used. Among the different coolant combinations, 60EG:40DW showed higher heat transfer as indicated by higher temperature difference across both shell and tube sections followed by other combinations when compared to pure ethylene glycol. Shell outlet and Tube outlet temperature with 60EG:40DW increased by 227% and 105% respectively when compared with pure EG, due to improved heat exchange. Heat transfer rate, heat transfer coefficient with 60EG:40DW increased when compared to pure EG.

Hydrodynamic Characteristics of Concave Front Pile-Supported Breakwaters with a Tubular Wave Screen

Concave front pile-supported breakwaters, namely, Galveston wall-shaped pile-supported breakwater (GS-PSB) and circular cum parabola-shaped pile-supported breakwater (CPS-PSB), have proven to be more effective in dissipating incident wave energy compared with vertical front pile-supported breakwaters. However, the run-up and the dynamic pressures on the concave front are reported to be high. In the present experimental study, an attempt is made to improve the hydrodynamic performance of the GS-PSB and CPS-PSB by mounting tubular wave screens on their seaside as an additional energy dissipator. The tubular wave screen is comprised of horizontally aligned circular tube sections with diameter and spacing leading to a porosity of 25%. The models were subjected to the action of regular and random waves in a wave flume covering intermediate to deepwater conditions. It is found that the impact of tubular wave screen on the hydrodynamic performance of the both the models differs. While, the tubular wave screen marginally affects the transmission, the reduction in reflection is more for GS-PSB due to its steeper slope. The energy dissipation offered by GS-PSB in deepwater conditions is found to significantly improve due to the presence of the wave screen, which is not the case with the CPS-PSB model. The run-up and dynamic pressures over the concave profiles are found to reduce for both models. A qualitative assessment of overtopping for both the models is also reported herein.

Low-velocity impact damages of filament-wound composite overwrapped pressure vessel (COPV)

Low-velocity impact tests were carried out on filament-wound composite overwrapped pressure vessel (COPV) specimens at different impact energies and impact points to determine the low-velocity impact damages of wound composite structures. The anti-impact performance of the filament-wound COPV was compared with that of composite laminated and filament-wound composite plates. Different impact damage modes and damage mechanisms inside the wound COPV were investigated through ultrasound scanning, X-ray, and scanning electron microscopy. Results showed that the impact force–time response curve of the wound COPV can be divided into an ascending area, a plateau area, and a descending area. The duration of the plateau area increased with the increase in impact energies. The impact resistance of the filament-wound COPV was the best, followed by that of the composite laminated plate, and the filament-wound composite plate was the worst. The major damage modes of the filament-wound COPV under low-velocity impact included matrix breakage, delamination, and fiber breakage. Delamination in the COPV tube section mainly occurred between the spiral wound and hoop layers. Delamination at the head of the COPV occurred between different winding layers. Fiber breakage inside the COPV mainly developed in the fiber overlapping zone inside the spiral layer. Results indicated that the fiber overlapping zone was the weak part in the filament-wound composite structure.

Flow instability in a volute-free centrifugal fan subjected to non-axisymmetric pre-swirl flow from upstream bended inflow tube

The characteristics of internal flow and performance of a centrifugal fan is greatly dependent on the inflow pattern. As the fan is subjected to incoming flow from an upstream tube, the size and geometry of the tube affect the three-dimensional motion of local flow and possibly degrades the aerodynamic performance of the fan. In this work, we performed a numerical investigation on the internal flow in a centrifugal fan subjected to incoming flow from an upstream bended inflow tube of various radii using the steady and unsteady Reynolds-averaged Navier-Stokes (RANS and URANS) simulation approaches. The effects of the non-axisymmetric pre-swirl flow generated due to the curvature of the bended inflow tube are demonstrated by analyzing the internal flow characteristics of the fan, including the spatial distributions and temporal variations of pressure field and streamlines, pressure fluctuations in the upstream tube, the inflow and outflow sections of the impeller, and the circumferential distributions of velocity and pressure in the impeller. The numerical results reveal that as the inflow tube is curved with larger curvature (smaller radius of the bended section), the pre-swirl inflow is strong and deteriorates the static pressure rise and static pressure efficiency of the centrifugal fan more remarkably, and the circumferential non-uniformity of pressure and velocity distributions appears inside of the channels of the fan. As the radius of the bended section increases, the instability of the internal flow gets more pronounced, as represented by the stronger pressure fluctuations at the inflow and outflow sections. The prediction capabilities of RANS and URANS approaches are also analyzed based on the numerical data and we found that the latter is more reliable in predicting the performance of the fan.

Large-range and high-sensitivity fiber optic temperature sensor based on Fabry–Pérot interferometer combined with FBG

A compact fiber optic temperature sensor based on the Fabry–Pérot interferometer (FPI) combined with FBG is analyzed and demonstrated experimentally in this paper. The FPI is fabricated by splicing a single mode fiber (SMF) with a section of silicon tube filled with ultraviolet (UV) glue to form an air microcavity. Owing to the high thermo-expansion coefficient of UV glue, the sensor can achieve a high sensitivity. Besides, the cascaded FBG can be used to locate different temperature intervals, and therefore the detectable temperature range is largely extended. Experimental results indicate that the sensor has a temperature sensitivity of −4.665 nm/°C in a wide temperature range of −30 to 15 °C. In addition, our fiber temperature sensor also exhibited excellent consistency, good repeatability, and stability during the thermal cycle tests. Therefore, it has a good practical prospect.

A Simple Formula for Prediction of Compressive Strength of Square CFT Columns

Concrete filled steel tube structures are becoming very popular in the modern civil engineering projects. Studying composite structures is useful, since it is an innovative and contemporary way to build structures. This type of structure has the ability to use respective strength of both steel and concrete due to confinement. Prefabrication of steel tube section is beneficial, and allows rapid installation into main structure. It also reduces the assembly cost and construction time. This paper will present the simple equation to predict the compressive strength of square concrete filled steel tube by using Finite Element Analysis (FEA)based software ABAQUs. In this study, 3D non-linear finite element models of short square composite columns were prepared using ABAQUS. The results were compared with published experimental tests of a concrete filled steel tube short columns. After getting the good agreement with the experimental results, a simple equation for the prediction of compressive strength is presented by considering the width to thickness ratio of steel tube. Results are validated with experimental results. The equation can predict the compressive strength only for the given material strengths and in future, the simple equation can be improved by considering different parameters e.g. material strength, slenderness ratio and end conditions.

Research on prediction method of section convergence and deformation of shield tunnel in operation period based on deep learning

Presently, the tunnel construction of China is changing from “mainly construction” to “equal emphasis on construction and maintenance”. In this context, tunnel structure inspection, monitoring, and maintenance technologies have developed rapidly. However, the effective use and in-depth mining of massive data has always been the most difficult point in this field. Based on deep learning technology, this paper carries out in-depth mining of the multi-source data of the tunnel structure, so that the convergence and deformation of the section during the operation of the shield tunnel is predicted in a short time. Taking the Nanjing Yangtze River shield tunnel project as an example, the indicators are screened based on the fluctuations of the pair wise correlation coefficients of all monitoring indicators. And based on the Keras (a high-level neural network API) framework, a short-term prediction model of the convergent deformation of the shield tube section at this location is established. The results show that the model successfully predicts the convergence of the tunnel section in the next 10 days, and the prediction accuracy reaches 93.6 %. The short-term prediction of key sections and the near warning sections is realized, so as to prevent it in advance.

Post-buckling analysis of two-layer contact concentric tubular strings in pipe

Buckling of concentric tubular strings in pipe is an essential problem in the fields of medical, biological, and nanomaterials, especially in petroleum engineering. Completely different from the buckling of the classic Euler compression columns, the buckling of concentric tubular strings involves geometric nonlinearity and contact nonlinearity, and has more complicated geometric deformations and buckling configurations. In this paper, a finite element method combining the spatial beam element and the two-layer contact gap element is proposed, and a virtual transient dynamic method is introduced to solve the static buckling of concentric tubular strings. The internal concentric tubular strings are discretized into spatial beam elements, and the contact relationships between tubular strings are described by two-layer contact gap element. Meanwhile, the larger damping is used to attenuate the dynamic response of the system, so as to find the static part of the transient dynamic solution. Appropriate damping and element length are determined by numerical simulation. The structural characteristics and contact states of eight post-buckling configurations are studied. The helix pitch values of specific configurations are in good agreement with the theoretical solutions. In addition, the distribution of bending moment, shear force and contact force in various post-buckling configurations is studied. For the full helical buckling, it is found that there is only one non-contact section in the transition section of inner tube and two non-contact sections in the transition section of middle tube. The research results of this paper provide a theoretical basis and reference for further study on the buckling of multi-layer concentric tubular strings.

Drive-Induced Backward-Wave Oscillations in Helix Traveling-Wave Tubes—A Case Study

The output section of helix traveling-wave tubes (TWTs) usually features a tapered delay line to enhance the amplifier performance. This alters the phase velocity of the circuit waves, which, in particular, disturbs the narrowband synchronism between the backward wave (BW) and the electron beam. As a result, the excitation threshold of BW oscillations (BWOs) increases. Large-signal operation significantly alters beam-wave synchronism, as the electrons loose kinetic energy during the amplification process, i.e., toward the TWT output. As a result, beam and BW may interact over a larger distance, thus lowering the threshold for the onset of BWOs. These would thus be drive-induced in contrast to the zero-drive BWOs mentioned above. The following investigates the occurrence of such drive-induced BWOs as a case study of several different TWT models and proposes a theory for the large-signal instability. As the simulation process is quite involved and time-consuming, a heuristic approach for the fast prediction of the oscillation is presented as well.

Experimental Investigation on Concrete Filled Steel Tube Columns under Concentric and Eccentric Loading

Modern construction projects such as skyscrapers, bridge with a large span, residential structures, towers for transmission, warehouses and other industrial structures have all incorporated concrete-filled steel tube (CFST) columns. Fire resistance, excellent ductility and high bearing capacity are all the advantages of CFST columns. Among the different shapes of CFST columns, uses of rectangular and square CFST columns are becoming more favored in modern construction projects for their simple beam-to-column connections design. This study tested 10 concentrically loaded CFST columns and 8 eccentrically loaded CFST columns. One of the most effective techniques to delay local buckling and enhance the ultimate strength of the CFST columns is to use longitudinal inner stiffeners on these steel tubes. Cold-formed steel tube sections are vulnerable due to local buckling; however, a concrete core is able to restrict such early local buckling in the cold-formed steel tube. The test specimens consisted of unstiffened sections and longitudinal inner-stiffened sections. In total, the experimental program tested 18 CFST stub columns with both compact and slender sections, without longitudinal stiffener, with 2 longitudinal inner stiffeners and with 4 longitudinal stiffeners. The test strengths have been as compared with predictions based on the existing design code AISC 360-16 for calculating the ultimate capacities of the CFST stub columns subjected to both concentric and eccentric loading. The focus was mainly on the effect of vertical stiffener square concrete-filled steel tubes on the overall concentric and eccentric compression capacity. The results identified that the longitudinal inner stiffeners had a significant impact on the ultimate strength, deformability and mode of failure in the CFST stub columns. To prevent local buckling of such steel tube, a longitudinal inner stiffener could be applied. In addition, the compression capacity was increased by 12–13.5%.

Assessment of surface crack growth of composite girders with concrete-filled tubular flanges and corrugated webs through substructure-based numerical modelling

This paper presents an analytical assessment of surface crack growth behaviour of composite girders with concrete filled tubular flanges and corrugated webs (CGCTFCWs) with the aid of substructure-based numerical modelling. Distinctive features of crack propagation on the tubular flanges with considerable stress gradient from lower to upper cracked tube surface interacted with the weld toes along the corrugated webs are replicated in the substructure modelling and discussed in details. Based on a favourable verification of stress intensity factors (SIFs) with reported model with semi-elliptical surface crack in plates and rectangular hollow section tube, an analytically derived substructure model of critical corrugated web-flange welded details coupled to the rest of the structure is developed. Such a model is distinguished itself from that based on original Newman and Raju equation by an amendatory of the stress gradient induced by the shifting of the neutral axis and the geometry as crack penetrated through the tube wall. Based on a parametric analysis, the SIFs significantly influenced by the corrugation depth ratio, the tube thickness-to-width ratio and the tube thickness-to-depth ratio in relation with the dimensionless crack length are demonstrated and taken into account in the derivation of a new geometry amendatory coefficient. An experimental investigation was also implemented to further examine and validate the modelling crack propagation response. The resultant fatigue fracture manner and the stress concentration of the hot spot are virtually in good correlation with the modelling results. Moreover, the relations between the crack growth increment and fatigue endurances from experimental measurement match well with these predicted by the NASGRO equation using amended SIFs, indicating that the proposed model is able to trace the distinct geometry effects of the corrugated web and the tubular flange on the crack propagation response of CGCTFCWs.