Steel Support Research Articles

Health status evaluation of highway tunnel inverted arch based on variable weight and extension cloud model

Accurate assessment of the inverted arch's health status in tunnels is pivotal for preventing floor heave and ensuring traffic safety. This study investigated the condition of inverted arches in 237 highway tunnels in Gansu Province, China. An evaluation system was developed to assess the health of inverted arches, focusing on the disease characteristics and occurrence frequencies of tunnel pavements. Additionally, a new variable weight calculation method was established, incorporating the extension cloud and variable weight theory based on cloud correlation degrees. Established grading standards were used to assign scores for determining the health status of the inverted arches. The completed health status evaluation model was applied to a case study of the Taiyangshan tunnel, demonstrating its effectiveness and applicability. The results show that the evaluation method, applying variable weights based on health levels of indicators, effectively uncovers potential risks to deteriorating inverted arches. In the Taiyangshan tunnel, three inverted arches were classified as sub-healthy, relatively dangerous, and dangerous. Intensified inspection is required for sub-healthy sections. For areas categorized as relatively dangerous, employing 'miniature steel pipe piles + H-shaped steel support' has proven effective. This methodology yields essential insights for developing effective treatment strategies for inverted arches in similar tunnel engineering projects.

Neutron irradiation effects on the low cycle thermal fatigue performance of first wall mock-ups

For the first wall (FW) of ITER, beryllium will be the plasma facing material and has to sustain high thermal, particle and neutron loads. In order to assess the synergistic effects of thermal and neutron loads in total ten Be-armored FW normal heat flux (NHF) mock-ups were produced consisting of two Be flat tiles each joined via hot isostatic pressing (HIP) to a CuCrZr heat sink and a steel support structure by different manufacturing routes to assess the most promising ones. Five of them were neutron irradiated, two at Centrum Výzkumu Řež in Czech Republic and three in the High Flux Reactor at NRG in the Netherlands. The remaining mock-ups were kept as reference. All flat-tile mock-ups had two Be-tiles and were exposed to cyclic steady state heat loads in the electron beam facilities JUDITH 1 and 2 up to a maximum power density of 3.75 MW/m2, in order to find the damaging threshold. A screening step using 1 MW/m2 was performed after finishing each loading step and after failure for direct comparison and detection of any deterioration caused by the cycling. Despite being still in the early development phase of Be joining, all mock-ups sustained the cycling up to at least 2.75 MW/m2 and clear differences in the performance of irradiated vs. non-irradiated mock-ups were observed.

Case study of performance assessment of overlapping shield tunnels with a small curve radius

AbstractDue to the network planning of subways and their surrounding structures, increasingly more overlapping shields with a small curve radius have been constructed. A newly constructed upper tunnel partly overlaps a lower one, leading to the extremely complex uplift of the lower tunnel caused by the construction of a new tunnel. Based on the shield‐driven project that runs from the Qinghe Xiaoyingqiao Station to the Qinghe Station in Beijing, which adopts the reinforcement measures of interlayer soil grouting and steel supports on site, in this study, the uplift pattern of the lower tunnel and the stress characteristics of steel supports were investigated through numerical simulations and on‐site monitoring. The study results show that among all tunnel segments, the first segment of the shield witnesses a maximum uplift displacement that increases with the horizontal space between tunnels. On using either interlayer soil grouting or steel‐ring bracing reinforcement, the uplift of the tunnel lining exceeds the control value; by contrast, when these two measures are jointly applied, the uplift of the tunnel lining does not exceed a maximum value of 4.87 mm, which can satisfy the requirements of deformation control. Under these two joint measures, the soil strength between two stacked shield tunnels can be enhanced and the uplift deformation can be restricted with the interlayer soil grouting. Also, the segmental deformation and overall stability of the existing tunnel can be controlled with the temporary steel supports. The deformation of circumferential supports and segments is closely related to each other, and the segmental uplift is controlled by H‐shaped steel supports. With the increase in the horizontal space between twin shields, the effect of the construction would gradually weaken, accompanied by a gradual reduction of the stresses of steel supports. These findings provide a valuable reference for the engineering design and safe construction of overlapping shield tunnels with a small curve radius.

Rehabilitation of RC Structure by Using Ferrocement Jacketing

Many structures fail or deteriorate before completion of its intended life span due to poor quality of material used, lack of mix design, poor workmanship, attacked by environmental agencies, etc. Sometimes due to slenderness of column or less reinforcement provided than actual requirements, less depth/thickness provided in flexural members, etc. feels excessive vibration during walking on floor ultimately develops cracks. Strength of such structural elements can be found by using non-destructive tests like Rebound hammer test, ultrasonic pulse velocity test, etc. If strength of existing structural elements is less than desired strength then structural consultant suggested strengthening of structural elements. There are various methods used in strengthening of existing structural elements like pressure grouting, fibre wrapping, chemical treatment, structural steel support, jacketing, etc. But these techniques are very costly and need precise quality control activity. In the present of investigation, strengthening of beam and column elements of a building by ferrocement techniques and steel jacketing were carried out and cost and cost comparison and strength results before and after strengthening are presented. It is observed that the strength og structural by ferrocement technique is cost effective than steel jacketing technique. And also has increase in the strength of RCC elements

TIME DEPENDENT DEFORMATIONS OF A COUPLED BRIDGE: A CASE STUDY

<p>The bridge's span structure comprises a connected beam designed to support a concrete slab poured over parallel steel supports. Simultaneously, segmental construction, shrinkage, and the flow of concrete play a significant role in stress redistribution over time. The span construction is statically indeterminate due to its connections with the abutments, and temporal deformations occur under additional complex conditions. In this analysis, we employed a calculation model based on the layered finite elements method developed by the authors. This model can be utilized to analyse both statically indeterminate supports and the predicted phased construction method. It accounts for changes in the static system and loading, as well as variations in the layers within the coupled section and the viscous properties of the concrete over time. The calculation analysis results reveal that viscous concrete deformations, combined with different moments of activation of individual segments, have a significant impact on stress redistribution over time. Such intricate analyses are indispensable for ensuring the required safety and cost-effectiveness of the bridge span construction.</p>

Study on mechanical properties of corrugated steel support tunnel under fault sliding

PurposeThere have been limited investigations on the mechanical characteristics of tunnels supported by corrugated plate structures during fault dislocation. The authors obtained circumferential and axial deformations of the spiral corrugated pipe at various fault displacements. Lastly, the authors examined the impact of reinforced spiral stiffness and soil constraints on the support performance of corrugated plate tunnels under fault displacement.Design/methodology/approachBy employing the theory of similarity ratios, the authors conducted model tests on spiral corrugated plate support using loose sand and PVC (polyvinyl chloride) spiral corrugated PE pipes for cross-fault tunnels. Subsequently, the soil spring coefficient for tunnel–soil interaction was determined in accordance with ASCE (American Society of Civil Engineers) specifications. Numerical simulations were performed on spiral corrugated pipes with fault dislocation, and the results were compared with the experimental data, enabling the determination of the variation pattern of the soil spring coefficient.FindingsThe findings indicate that the maximum axial tensile and compressive strains occur on both sides of the fault. As the reinforced spiral stiffness reaches a certain threshold, the deformation of the corrugated plate tunnel and the maximum fault displacement stabilize. Furthermore, a stronger soil constraint leads to a lower maximum fault displacement that the tunnel can withstand.Research limitations/implicationsIn this study, the calculation formula for density similarity ratio cannot be taken into account due to the limitations of the helical corrugated tube process and the focus on the deformation pattern of helical corrugated tubes under fault action.Originality/valueThis study provides a basis for the mechanical properties of helical corrugated tube tunnels under fault misalignment and offers optimization solutions.

Effect of Undercrossing Shield Tunnels Excavation on Existing Rectangular Pipe-Jacking Tunnels

Shield tunneling underneath existing rectangular pipe jacking can often lead to uneven settling. To solve the problem of excessive deformation of the existing underground pedestrian passages, excavated via the rectangular pipe-jacking method due to the adjacent shield tunnels construction beneath, a safety control plan has been proposed based on the shield tunnels constructed beneath a well-type underground pedestrian passage in Hohhot Subway. This plan involves the use of both numerical simulations and on-site monitoring to investigate the deformation patterns of the rectangular pipe jacking. The results suggest that the combined approach of interlayer soil grouting and steel support reinforcement is not only appropriate but also feasible for on-site implementation. It can be concluded that interlayer soil grouting for reinforcement was applied successfully to improve the strength of surrounding soils. Steel support reinforcement is advantageous for controlling the relative deformation between pipe segments. The maximum settlement induced by the shield tunneling for Passage A and Passage B was measured at 17.67 mm and 10.08 mm, respectively, with the final settlement distribution of the rectangular pipe jacking taking on a “W” shape. This study could provide a reference for the design and construction of shield tunnels that undercross existing rectangular pipe-jacking tunnels.

Deformation rule of bored pile & steel support for deep foundation pit in sandy pebble geology

Regarding the whole excavation process of the support system of the Southwest Jiaotong University Station of Chengdu Metro Line 6 (the deep foundation pit bored pile + steel support and support system) as the engineering background, this paper studies the deformation rule of the deep foundation pit bored pile + steel support of the sandy pebble foundation. The deformation rule of this support system, the settlement rule of the ground surface outside the pit, and the rule of the uplift of the loose at the bottom of the pit are studied. A key analysis of the positive corner of the foundation pit is conducted, and the rationality of the optimization of the support scheme is evaluated. This paper provides effective guidance for the subsequent deep foundation pit construction and provides a reference for deep foundation pit construction.

Complex TiC-Ni-based composites joined to steel support by thermal explosion under load: synthesis, microstructure and tribological behavior

ABSTRACT The combustion in thermal explosion mode of reactive mixtures of Ti–Ni–graphite(carbides, borides, oxides), under load, was used to produce complex composite materials, densified and joined to a C55 carbon steel support. The ignition of the exothermic reaction, carried out thanks to the rapid high-frequency heating of a green compact up to 1573 K, was followed by an isothermal holding at 1373 K for 360 s. This procedure ensured a perfect mechanical assembly between the composite material and the steel substrate. SEM analysis and concentration profiles carried out at the interface testified to the interdiffusion of iron and titanium atoms between the two materials. The maximum combustion temperature (Tmax.) exceeding 2200 K induced the appearance of a liquid phase that assisted densification and joining, and in which a part of the additions was dissolved before cooling. The starting chemical composition of reactive mixtures largely determined the microstructure, hardness and tribological behavior of the composites after the process. Thereby, the maximum hardness (1235 HV0.15) and the lowest wear rate (1.824 × 10−6 mm3.N−1.m−1) were obtained in the sample containing TiC, Al2O3 and TiB2 hard phases. The manufactured samples exhibit no deterioration of the composite by spalling, regardless of the starting composition.

An empirical assessment of selection excavation methods and support system in Budong-Budong Dam diversion tunnel, Central Mamuju, West Sulawesi Province

Budong-Budong Dam is located on Salulebo River, West Sulawesi Province, and has a diversion tunnel to divert river flow so as not to interfere with construction at the main dam. This diversion tunnel has a D shape which is dimensions 5 m. The Method used in empirically assessing rock mass quality is Rock Mass Rating (RMR) and Japan Society of Civil Engineers (JSCE). The data used are RMR values and rock-type categories. The results show that the diversion tunnel is in lithology tuffaceous sandstone intercalation tuffaceous siltstone and tuffaceous breccias. Weathering degree from slightly-weathered to highly-weathered. The dominance RMR value is 27-53 and rock-category is CII with L massif rock type. The excavation method based on RMR is top-heading and bench and the excavation method based on JSCE is a full-face method with an auxiliary bench cut. Support systems proposed by RMR and JSCE are rock-bolts, shotcrete, and steel sets (steel support). Even though it has been done empirically, it needs to be considered for modeling to be effective and efficient.

Detection of a Rotating Conveyor Roller Casing Vibrations on a Laboratory Machine

The article describes the basic parts and the overall design of the laboratory machine, which can be used to measure vibrations generated by a rotating conveyor roller attached to the flattened parts of its axis in the cut-outs of the conveyor idler support. On the structurally modified support of the conveyor idler consisting of the insertion of a plastic element placed between the roller axis and the support cut-out, the vibration acceleration values of the rotating roller from symmetric analysis were measured and compared with the values from asymmetric analysis of the traditional roller axis placement in the steel support. The size of the peripheral speed of the roller was determined, during the experimental measurements, by controlling the speed of the electric motor using a frequency converter. The obtained results of the measured values of vibration velocities in three mutually perpendicular planes showed a reduction in vibration values of about 15% when using plastic holders. The paper aims to present one of the possible technical solutions that can limit the vibration values transmitted to the supporting structure of the conveyor belt, generated by the rotating casing of the conveyor roller.

A modified support pillar design for a flat vacuum-based solar thermal collectors

Improving the efficiency of low-temperature solar collectors can be attained by decreasing the heat loss from the collectors. The current work proposes an efficient vacuum-based solar thermal collector design with a new support pillar design to reduce the thermal bridge through the support pillars. In addition, the absorber of this collector is isolated from the front and the rear side by a vacuum layer with transparent glazing. The absorption of front and backside ground reflected radiation, possibly achieving the concept of bifacial flat solar thermal collector. The results of the new support pillar are compared with those of stainless steel and glass support pillars under the same conditions. The results showed that using the new support pillar design decreases heat loss from the absorber. At the 6 mm support pillar diameter, replacing the stainless-steel support pillar with the new modified pillar reduces the heat flux through the front glazing from 59.7 W/m2 to 21.9 W/m2 at ASTM boundary conditions.

Determination of steel arch support distance for roadways under the open-pit mine: a case study at the Mong Duong Coal Mine (Vietnam)

Purpose. Nowadays, in Quang Ninh coalfield, the mining activity in quarries is increasing. For this purpose, mine roadways are dug and supported. After the mine roadways are dug, they are mainly supported by steel arches. Statistics in fact show that about 85 % of the roadway support structure at the underground coal mines in Quang Ninh are supported by the steel arch support made of SVP profile. The purpose of the study is to calculate and determine a reasonable steel support distance for the roadways located under the open-pit mine to ensure their stability and the safety of exploitation. Methodology. In this study, the numerical simulation method was used. On the basis of Phase2 software and geological conditions of the mine, the authors established a simulation model to determine the pressure acting on the roadway and select a reasonable support distance. Findings. The study considered different steel arch support structure distance following the structure of the rock mass under the 790 open-pit area at the Mong Duong Coal Mine, the internal forces in SVP steel arch support structure distance were also studied for one-lane railway and two-lane railways roadway. From the results of internal forces in the steel support structure, a reasonable SVP-22 steel arch distance was selected, which is 0.7 m for the one-lane railway roadway, as well as SVP-27, which is 0.7 m for the two-lane railway roadway. Originality. Using Phase2 software, the authors created a simulation model of the roadways in Seam L7 located on the West side of Mong Duong Coal Mine, which allowed analyzing and describing the condition of the surrounding rock mass. This study utilized a numerical modeling approach to simulate and establish the bending moment and axial force of both single and double lane railway roadways, across a range of support distances. Based on the results of pressure calculation for the roadways, the authors have selected a reasonable support distance for each corresponding roadway. Practical value. The findings of the study serve as the foundation for the practical application of production methods at the Mong Duong Coal Mine. On the basis of calculating the pressure acting on the roadways at the Seam L7 in the West Side under the 790 open-pit area, the distance of steel arch support was determined, from which the roadway support plan has been developed. This research result will also serve as a basis for other mines with similar geological conditions in Quang Ninh coalfield to consider and apply.

Lessons learned from in situ corrosion experiments in the HADES URL

Abstract A wide range of metals have been studied as a candidate container material to be considered in the geological disposal concept of high-level radioactive waste and spent fuel in Belgium. More than 40 years ago, SCK CEN started studies on the corrosion of these metals. The HADES underground research laboratory (URL) played an important role in the corrosion research as it enabled in situ corrosion experiments to be carried out that simulate realistic disposal conditions as closely as possible. These experiments consisted of placing metallic coupons on a steel support tube, heated from the inside, that was installed in Boom Clay, thereby exposing the coupons to various conditions representative of the disposal concept that was considered at that time. Test durations lasted from 6 months to approximately 7.5 years. This paper summarizes the results from the various corrosion studies and discusses their implications in the choice of disposal concept. One of the main outcomes of these experiments was a change of rationale regarding the choice of the container material from carbon steel (corrosion-allowance) to stainless steel (corrosion-resistant). The main arguments for this change were the need to avoid severe pitting corrosion during the aerobic period and to minimize the generation of hydrogen gas during the subsequent anaerobic period.

Safety and Stability Analysis of Demolition and Reconstruction of Existing Railway Bridge Piers and Caps

The process of bridge reconstruction often involves the demolition and reconstruction of bridge piers and caps, while most of the construction methods used in the previous bridge reconstruction projects changed the bridge-bearing positions. In this paper, an in situ replacement scheme of bridge piers and caps is proposed, which can maintain the existing stress state of the bridge without changing the bearing position. In order to figure out the safety and stability of the in situ replacement scheme of existing railway bridges, a steel support system model for the removal and reconstruction of the bridge piers and caps is established by ABAQUS, according to a domestic railway bridge reconstruction project, and verified by field measurement test. Based on the model, the stress and deformation of the steel support system under a trainload are analyzed, as well as those of the bearing foundation and the superstructure. The results show that the steel support system and steel pipe piles located directly below the line carrying the trainload are subjected to the greatest stress and deformation. While under various load conditions, the stress and deformation of the main components in the steel support system of the in situ replacement scheme meet the design requirements, and the structure is safe under a trainload. In addition, guided by the numerical calculation results, the implementation scheme, existing problems, and solutions of the project are introduced in detail, which can provide a reference for similar projects.

Adhesive and Rheological Features of Ecofriendly Coatings with Antifouling Properties.

In this work, formulations of "environmentally compatible" silicone-based antifouling, synthesized in the laboratory and based on copper and silver on silica/titania oxides, have been characterized. These formulations are capable of replacing the non-ecological antifouling paints currently available on the market. The texture properties and the morphological analysis of these powders with an antifouling action indicate that their activity is linked to the nanometric size of the particles and to the homogeneous dispersion of the metal on the substrate. The presence of two metal species on the same support limits the formation of nanometric species and, therefore, the formation of homogeneous compounds. The presence of the antifouling filler, specifically the one based on titania (TiO2) and silver (Ag), facilitates the achievement of a higher degree of cross-linking of the resin, and therefore, a better compactness and completeness of the coating than that attained with the pure resin. Thus, a high degree of adhesion to the tie-coat and, consequently, to the steel support used for the construction of the boats was achieved in the presence of the silver-titania antifouling.

Metal-Supported Solid Oxide Cells for Energy Conversion, Electrolysis, and Chemical Synthesis

The LBNL metal-supported solid oxide cell architecture contains zirconia electrolyte and porous backbones co-sintered between porous stainless steel supports. Advantages of this design include low-cost structural materials, mechanical ruggedness, excellent tolerance to redox cycling, and extremely fast start-up capability. These features enable a wide variety of applications including electrolysis for intermittent renewables, distributed power generation, and synthesis of valuable chemicals. Highlights from efforts in these areas are presented.

Proposal of a methodology for mass optimization of realistic steel structural systems composed of columns and galleries for support of solid bulk conveyors

Unlike most works in the literature that propose the optimization of benchmark problems or very simple real structures, with idealized loads and restrictions, this work proposes a complete methodology to optimize real support structures of belt conveyor lines, considering realistic loads and restrictions imposed by international technical codes. Thus, the present work proposes a comprehensive methodology to minimize the mass of realistic steel structural systems composed of columns and galleries to support solid bulk conveyors. The objective is to obtain the minimum mass for different interactions between gallery spans and column heights for conveyors, taking into account the optimization of size, shape, and topology of each structural subsystem (columns and galleries) and thus obtaining the mass per unit of length of the conveyor line. For this, recurrent steel support structures are identified, analyzed, and selected according to their performance and, structurally resisting the applied load inputs, they are designed to minimize the structural system mass. The Enhanced Particle Swarm Optimization (EPSO) algorithm is used considering multiple constraints involving stress, displacement, buckling, frequency, and acceleration limits according to various international codes. An example of a realistic conveyor line is presented, in which 42 different interactions among the dimensions of the subsystems are simulated and the minimum mass of the system is obtained for each one of them. Thus, the results obtained allow, from the knowledge of the geometrical characteristics of the span and height of the system, to identify the optimized linear mass for any situation within the study boundary, resulting in an important practical contribution. Additionally, the graphs presented allow the designer to choose optimized solutions in terms of cost and raw material consumption for real-field applications. It was possible to determine that appropriate choices represent up to 35% mass reduction of structural systems.

Analysis of cracking evolution mode of the monobloc sleeper

PurposeMonobloc sleepers have several problems related to bending cracking, especially longitudinal cracking and cracking at rail seat under preload release. Therefore, the purpose of this study is to describe the behavior and cracking mode of prestressed concrete railroad sleepers under static loads using the positive test. Experimental tests followed by 3-D numerical models were performed of the same test.Design/methodology/approachTwo steel supports were placed on the rail seat. During a progressive loading, the initiated cracks had approximately the same amplitude as those obtained from the numerical model. The type of cracking depends on the intensity of the applied static load and the loading rate. A validated three-dimensional digital model was established. The obtained results showed a perfect resemblance to the experimental tests. The final design was optimized and verified using a validated numerical simulation.FindingsAt low static loading levels, the first flexural shear cracks appeared at a vertical position located between the two steel supports. At higher static loading levels, bending shear cracks have occurred. The latter are inclined at the steel supports. It was proven that for higher loading levels, shear cracks were the primary mode of failure.Research limitations/implicationsOwing to the sensitivity of monobloc sleepers to technology production, the results are limited by the maximal loading and press used.Practical implicationsNumerical modeling greatly reduces uncertainties in laboratory testing and is an important tool for visualizing and quantifying rail seat cracks to understand behavior and predict collapse.Social implicationsEnsuring human life during rail operations is one of our the long-term priorities. This cannot be done unless the authors manage to master the manufacturing tool for sleepers while controlling the limitation of crack propagation.Originality/valueThe three-dimensional numerical established model has been checked and validated against the experimental results using the positive test to understand the behavior and the cracking mode of prestressed concrete railroad sleepers under static loads. The proposed numerical model has been more refined for a later more complex application by reducing the computation time.

Deformation Characteristics Analysis of Temporary Support in Unsymmetrical Loading Tunnel Excavation under Composite Support

Based on practical engineering, considering the characteristics of unsymmetrical loading, shallow burying, and weak surrounding rock of the tunnel, MIDAS finite element software is adopted to analyze the influence effect and deformation characteristics of a temporary steel support when the tunnel is excavated by a two-step center diaphragm method (CDM). The simulation results are compared with the field monitoring results. It can be seen that: (1) Affected by the unsymmetrical loading, the settlement of the right spandrel of the tunnel is obvious. The existence of a temporary steel support reduces the settlement of the surrounding rock at the spandrel greatly, making the distribution of principal stress at the spandrel more reasonable. (2) The deformation of the temporary steel support at the upper bench undergoes four stages: convergence, expansion, convergence, and stabilization; and the deformation at the lower bench undergoes five stages: convergence, expansion, convergence, expansion, and stabilization. (3) There is an obvious “bench-type” phenomenon in the principal stress change of the temporary steel support. The analysis results provide a scientific basis and technical guidance for the construction optimization of unsymmetrical loading tunnels using the same support technology.