Steel Arch Research Articles

Experimental Behaviour of Tensioner for Rigid Hangers of Arch Bridges

In steel tied arch bridges where the hangers are made of rigid bars, the replacement of damaged hangers is rather complex. In fact, while generally the cable hangers are already prepared with anchors at the ends and their replacement traces the initial stages of construction with their prestressing, on the contrary, the rigid bars are welded to the arch and the deck, so their replacement must include the design of a new suspension system that allows the insertion of a pretension where this had never been considered. To check the reliability of this new system, a prototype of tensioner was studied for the case of a steel arch bridge in which the high level of corrosion made it necessary to replace all the original hangers with new ones. This entailed the need to test the tensioner performance with the aim of ensuring the axial force transmission between the two hanger segments without slippage in the threads, as well as to test the correct tension setting before construction and putting into service the hangers to be replaced. For this reason, a predictive experimental campaign was carried out on a prototype by means of tests for the mechanical characterization of the materials used, tensile tests of the system, and tensioning tests under load, measuring the displacements and strains of the system elements. The results of the tests, with slippage in the threads limited to the 2% of total elongation, and the turnaround-stressing curves were useful for the definition of the pieces to be assembled during on-site work and for addressing the operating procedures of the tensioning phases on-site during hanger replacement. Validation with the on-site monitoring of stressing operation was conducted at the end; the monitoring of tension through dynamic tests confirmed the agreement of on-site results with the predictive loading tests of the experimental campaign on the tensioner prototype.

Evaluation and Comparison of Rock Bolting Versus Steel Arch Support Systems in Thick Coal Seam Underground Galleries: A Case Study

This study investigates the feasibility of rock bolting support in an underground coal mine gallery with a thick coal seam. The Ömerler underground coal mine working area, owned by the West Lignite Enterprise (GLI) of the Turkish Coal Enterprises (TKI), was selected for this purpose. Longwall top coal caving (LTCC) is implemented as the production method in the Ömerler underground coal mine. Field and laboratory studies were conducted to determine rock mass and rock material properties, followed by experimental, empirical, and numerical analyses based on the acquired data. The obtained design results were evaluated using a resin-grouted rebar (RBR) rock bolting system and steel arch support (SAS) pilot application areas. The numerical modeling results conducted using the Fast Lagrangian Analysis of Continua 3D (FLAC 3D) (v6.0) program indicated less displacement and secondary stress change in the RBR-supported zone compared to the SAS-supported zone. In situ measurements also demonstrated that RBR provided more successful support to the roof during coal production activities. The findings suggest that RBR is a more effective solution when evaluating the feasibility of rock bolting support systems in underground galleries with thick coal seams at the Ömerler underground coal mine. This study emphasizes the importance of more sustainable and safe support systems to enhance operational efficiency in the coal mining industry.

Physical model test and application of 3D printing rock-like specimens to laminated rock tunnels

Weak structural plane deformation is responsible for the non-uniform large deformation disasters in layered rock tunnels, resulting in steel arch distortion and secondary lining cracking. In this study, a servo biaxial testing system was employed to conduct physical modeling tests on layered rock tunnels with bedding planes of varying dip angles. The influence of structural anisotropy in layered rocks on the micro displacement and strain field of surrounding rocks was analyzed using digital image correlation (DIC) technology. The spatiotemporal evolution of non-uniform deformation of surrounding rocks was investigated, and numerical simulation was performed to verify the experimental results. The findings indicate that the displacement and strain field of the surrounding layered rocks are all maximized at the horizontal bedding planes and decrease linearly with the increasing dip angle. The failure of the layered surrounding rock with different dip angles occurs and extends along the bedding planes. Compressive strain failure occurs after excavation under high horizontal stress. This study provides significant theoretical support for the analysis, prediction, and control of non-uniform deformation of tunnel surrounding rocks.

Optimization of Hanger Spacing of Steel Arch Bridges Using Dynamic Loads

Bridges are basic infrastructure that must be met to create regional connectivity in Indonesia. One type of bridge that is often used is a curved bridge, which has the advantages of high strength, attractiveness, aesthetics and economy. In order to accelerate the development of bridge infrastructure, an efficient innovation in curved bridge design is needed. The development of curved bridge structures to achieve efficient designs has received much attention in several decades. However, researchers have only focused on optimising the geometry variation of the arch height. Therefore, the aim of this research is to innovate the optimisation of the hanger spacing on the arch bridge structure. In order to obtain optimal results, a bridge model is carried out by varying the hanger spacing of the centre model with a hanger spacing ratio of (1.3 - 1.1 - 0.9 - 0.7), a flat model with a hanger spacing ratio of (1 - 1 - 1 - 1) and an edge model with a hanger spacing ratio of (0.7 - 0.9 - 1.1 - 1.3), so that from the three models, the effect of hanger location on three conditions is obtained. Each model is modelled in the SAP2000 software and given a bridge service load to obtain the internal forces and deflections that occur. The output of the internal force and deflection is then analysed to determine the effect of the location of the bridge service hanger. The serviceability of the bridge is also analysed by calculating the ratio between the weight of the bridge and the deflection that occurs. The results of the analysis show that the location of the hanger affects the performance of the arch bridge structure. The centre model bridge design produces the most efficient structural performance in resisting the compressive axial forces and moments that occur, and produces the least deflection. Meanwhile, the edge model will provide the most efficient structural performance in resisting tensile axial forces. By referring to the results of the bridge weight to deflection ratio analysis, it can be concluded that the centre model produces the most efficient structural design when compared to other curved bridge models.

Development of a novel muck removal hydraulic manipulator for automated steel arch assembly of tunnel boring machine

Development of a novel muck removal hydraulic manipulator for automated steel arch assembly of tunnel boring machine

Tree-type hybrid mechanism configuration synthesis based on modular decomposition and power-concentrated joint closed-loop design

Mechanisms with multiple end-effectors are widely used in engineering due to their ability to synchronize and collaborate on multiple processes. However, this kind of mechanism is difficult to design due to its high topological complexity and complex applied loads. In order to solve this problem, this article proposes a configuration synthesis method for tree-type hybrid mechanisms from two aspects: modular decomposition of open-loop mechanisms and closed-loop design of power-concentrated joints. According to the correlation of the space of degrees of freedom between the end-effector, the mechanism is decomposed into different modules for hierarchical design to simplify the mechanism structure. The unit power concentration index is utilized to find the joints where the power output is relatively concentrated and replace them with low-complexity single-degree-of-freedom closed-loop structures to improve the structural stiffness and dynamic performance of the mechanism. Finally, the feasibility of the proposed method is verified by taking a steel arch looping mechanism with four end-effectors as an example. The aim of this article is to design a simple and reliable multi-branch mechanism with high load carrying capacity to make it more adaptable to the complex and harsh operating environment, which can provide a reference for the design of similar engineering equipment.

Mechanical Properties of Folding Arch Frame Joints for Unmanned Arch Erection

The application of folding arch frames is deemed crucial for unmanned arch frame erection, with the selection of the joint form being a determining factor in the overall mechanical performance of the folding arch frame, particularly in influencing the primary support safety. In light of the geological conditions of the New Wushaoling Tunnel project, three feasible joint forms for folding arch frames were proposed: buckle, adhesive, and interference-fit joints. Numerical simulations were conducted to analyze the arch’s overall mechanical and the joints’ local mechanical performances, aiming to identify the optimal joint form. On-site construction data were collected, and the effectiveness of unmanned arch frame erection was evaluated. The design requirements for the vertical displacement results of the steel arches with different joints were met. The maximum shear stress of the buckled arch frame was found to be the lowest, whereas that of the interference-fitted arch frame was the highest. The local shear stress of the adhesive joints was the lowest, while that of the interference-fit joint was the highest. Considering the material application limitations and calculation results, buckle joints are recommended. Unmanned arch frame erection, compared with manual arch frame erection, can save 66.6% of human resources and reduce the construction time by 33.3% to 50%. Statistical analysis has confirmed that the quality of automated arch construction can be guaranteed.

Mechanical Properties of Super-large and Shallow-buried Loess Tunnel with the Prefabricated Temporary Support

Background: At present, there are few studies on the mechanical properties of tunnels with prefabricated temporary support. Based on the project of the Xichengshan Tunnel on the highway from Zhuanglang to Tianshui, this paper studies the mechanical properties of tunnels with prefabricated temporary support The utility model patent for this article is a temporary steel support device for loess tunnel excavation. The patent number is ZL 2022 2 0141276. 1. Objective: The study aims to show the mechanical properties of a super large section of prefabricated temporary support shallow tunnel. Methods: The mechanical properties of the tunnel surrounding rock, lining, steel arch, anchor, and temporary support during construction were analyzed by combining numerical simulation and theoretical analysis. The maximum and minimum stresses of the tunnel surrounding rock, lining, steel arch, and anchor, and the maximum and minimum displacements of prefabricated temporary support were found through the analysis results. Results: The stress and displacement fields of surrounding rock, lining, steel arch, bolt, and temporary support of loess tunnel were analyzed. Results showed that the maximum principal stress of the surrounding rock is 0.293MPa, and the maximum horizontal displacement is 0.359cm. The maximum horizontal displacement of the lining is 0.413cm, the maximum vertical displacement of the steel arch is 1.538 cm, and the maximum displacement of the temporary support structure is 1.459 cm. The above data verify the safety of the proposed combined temporary support structure. Conclusion: Through the analysis results, the maximum and minimum stresses of the tunnel surrounding rock, lining, steel arch, and anchor, and the maximum and minimum displacements of assembled temporary support are found, which can guide subsequent construction.

Experimental and numerical studies on the behavior of corrugated steel-sprayed ECC composite arches with full-shear-connection

This paper proposes a novel corrugated steel-sprayed ECC (CSSECC) composite arch, which possesses high load-bearing capacity and fast construction speed. To investigate the ultimate load-bearing capacity, composite effect, and key mechanical indices, five 6 m-span arch specimens were tested. A finite element model was developed, and parametric analysis was conducted. The results indicate that the ultimate load-bearing capacity and damping ratio of the CSSECC composite arch specimens can reach 3.4 and 6.5 times that of the corrugated steel (CS) arch, respectively, and increasing the ECC thickness significantly enhances the damping ratio. Both studs and epoxy resin contribute to the composite effect, but studs are more reliable than epoxy resin even though their design shear connection degree is the same at 1.2. Finally, a design method for the stability bearing capacity under axial compressive was proposed.

Drying Shrinkage Properties of Arched Steel Fiber Reinforced Concrete by Volume Fraction of Steel Fiber

Drying Shrinkage Properties of Arched Steel Fiber Reinforced Concrete by Volume Fraction of Steel Fiber

Steel Arch and Rock Bolt Support in Terms of the Gateroad Stability Maintaining behind the Longwall Face

The longwall system is an extraction system commonly used in coal mining in many countries, including Poland. One of the methods for reducing extraction costs is the dual use of the gateroad. In the first instance, the gateroad serves as the tailgate, and during the exploitation of the second coal panel, it functions as the headgate. Such a situation requires maintenance of the roadway behind the longwall face, which is typically challenging, due to significant stress-related loads on the support and its substantial deformation. The support design for this kind of roadway should take into consideration the dual impact of exploitation pressure and the caved zone influence behind the longwall face. This article presents the results of in-situ research conducted on two roadways behind the longwall face. In both roadways, the effectiveness of specially designed steel arch frames and rock bolt patterns were examined to minimize roadway deformations and maintain their functionality. The research project was comprised of several stages. Initially, mining and laboratory studies were conducted to determine the geomechanical parameters of the rocks. Subsequently, excavation stability and functionality forecasts were performed based on the authors’ empirical indicators. Then, numerical analyses were carried out to design support schemes (steel arches and rock bolt) in both roadways. A fully automated monitoring system with programmed data loggers was designed to check the behaviour of a specific rock mass and the support elements. The load on the steel arch support was measured with the help of load cells, while the load on the rock bolt support was carried out with the help of measurement bolts. Behind the longwall face, the loads on the wooden cribs set from the goaf side were also monitored. Additionally, the measurement station was equipped with extensometers to monitor the movement of roof layers and stress meters to determine changes in rock mass stress. Laser scanning or traditional surveying methods were also used to verify the support schemes through roadway convergence measurements. The obtained results allowed us to draw conclusions regarding the optimization of support schemes and to give recommendations for the practical application of specific reinforcements in excavations maintained behind the longwall face.

An integrated determination method of optimal supporting time against TBM jamming

TBM (Tunnel Boring Machine) jamming and support failure occur frequently with inappropriate supporting time, particularly when TBM crosses adverse geology. Given this, an integrated determination method of optimal supporting time against TBM jamming was proposed. In this paper, the causes and failure mechanism of large deformation in the tunnel were revealed through X-ray diffraction (XRD) measurement of the rocks. The frictional resistance of TBM shield and the stress of support under different supporting time and measures were investigated by numerical simulation. It was shown that early installation of the support will lead to excessive load on the support, resulting in support failure. Contrarily, delayed installation of the support will lead to excessive tunnel deformation, inducing TBM shield jamming. The optimal supporting time was determined by comprehensively analyzing the critical deformation of TBM jamming and ultimate stress of support. The deformation of surrounding rock in the range of 31.6 mm ∼ 39.9 mm was the optimal support time in this study. Installation support with an optimal supporting time can ensure the safety of TBM and support simultaneously. The range of optimal supporting time decreases continuously with the weakening of support parameters. Specifically, the support measures (bolt + steel arch, shotcrete + bolt) cannot simultaneously ensure the safety of the TBM and support. The research results can effectively guide the prevention of jamming and support design in TBM tunnels.

Experimental and numerical investigation on out-of-plane ultimate strength of high-strength steel arches

This study presents an experimental investigation on the out-of-plane ultimate strength of high-strength-steel (HSS) I-section arches, which has not been reported previously. Fourteen I-section HSS arches having different yield strengths, cross-sectional dimensions, slendernesses, and rise to span ratios were tested under three-point symmetrical vertical loading. The corresponding out-of-plane deformation modes and strengths are identified. Subsequently, in order to predict the out-of-plane capacities of HSS arches, a finite element analyses is carried out, which takes into consideration residual stresses and initial geometrical imperfections. This analysis demonstrates a strong alignment with the experimental results, confirming the accuracy of finite element model and experimental results. Furthermore, the study comprehensively analyzes the influence of yield strength of steel, rise-span ratio, and slenderness on the ultimate bearing capacity of HSS arches. Through a parametric analysis, design formulas for the out-of-plane bearing capacity of HSS arches subjected to arbitrary compression forces combined with arbitrary bending moments are formulated. It is found that the out-of-plane ultimate strength of HSS arches is significantly influenced by the yield strength of the steel. Compared to a low strength steel (LSS) arch, the out-of-plane ultimate bearing capacity of the HSS arch increases with an increase in yield strength in the plastic stage, and the ultimate lateral displacement of the HSS arch decreases with an increase in yield steel strength due to the lower ductility of HSS. In addition, after reaching the out-of-plane ultimate bearing load of arch, the load-displacement curve of the HSS arch drops faster than the LSS arch. It is also found that the proposed design formulas can effectively predict the out-of-plane bearing capacity of HSS arches.

Study on Sunlight Temperature Field of Steel Box Arch Ribs in Irregular Arch Bridges

Due to their excellent thermal conductivity and sensitivity to temperature changes, special attention should be paid to the influence of temperature on steel-structure bridges. The temperature effect is complex, especially for unstable steel arch bridges with complex structural forms. This paper proposes an approximate method that measures the three-dimensional temperature field of the symmetrical arch rib with the two-dimensional temperature field of multiple sections. In addition, it converts the complex radiant intensity calculation of the special-shaped steel box arch rib into the calculation of numerous planar radiant intensities. It uses the ANSYS Workbench to establish the three-dimensional transient thermal analysis finite element model of the No. 2 steel box arch rib. The influence of seasons and arch rib direction on the temperature field of steel box arch ribs and the stress and deformation of steel box arch ribs under non-linear temperature effects were analyzed. The results show that the temperature changes in different seasons significantly impact the temperature changes in the arch ribs. The change in the azimuth angle of the arch rib has a significant impact on the temperature difference between the web plates on both sides of the arch rib; under the influence of the temperature field at the most unfavorable time in summer and winter, symmetrical stress concentration occurs in the arch foot area. Furthermore, the maximum vertical displacement is 13.9 mm and 10.8 mm, respectively. Finally, when the angle is 40°, the maximum temperature difference between the web plates on both sides is 6.9 °C.

Construction monitoring and analysis of low mountain ridge tunnel

In order to obtain the change rule of surrounding rock structure displacement and supporting structure internal force with time during the construction of the low mountain ridge tunnel, this paper relies on the Xishan Tunnel Project as the background. During tunneling, the displacement around the tunnel, the subsidence of the surface, the internal force of the steel arch and the pressure between the two layers of support are monitored dynamically. According to the above monitoring and measurement data, and the monitoring data analysis and nonlinear regression fitting, the predicted trend curve is obtained, the displacement change rules and characteristics of various surrounding rocks of the tunnel are obtained, to ensure the construction safety and stability requirements of supporting structure, and to provide a reasonable opportunity for the construction of secondary lining.

Research on mechanical response and time-space distribution of supporting structure of deep-buried tunnel in naturally water-rich loess

When the water content is small, the strength and stiffness of loess is considerably high. But with the increasing of water content, the shear strength of loess decreases since the matric suction of unsaturated loess decrease. If loess is soaked in water for long time after reaching the saturated state and the linking intensity weakened, the loess would be prone to softening deformation, so as to the stress of the tunnel supporting structure, which will cause the decreasing of the stability and durability of the tunnel. Therefore, the in-situ monitoring of surrounding rock deformation and stress characteristics of supporting structure is very important and was carried out in the deep-buried tunnel in naturally water-rich loess in this paper. The time–space effect of tunnel surrounding rock deformation, mechanical response of primary support, and secondary lining were monitored and analyzed. The results indicated that the deformation of surrounding rock was quite large, and the reserved settlement was insufficient. The analysis and calculation of the surrounding rock pressure and the stress of the steel arch indicated that the primary supporting structure of the upper bench was unsafe, the arch-foot had a trend of bending deformation to the side of the tunnel′s inner contour, and the inverted arch had a trend of uplift. Through the analysis of the contact pressure and the stress of the secondary lining reinforced concrete, the sidewall had a trend to deform to a side of the tunnel′s inner contour due to squeezing of the surrounding rock. The inverted arch had a trend to uplift, indicating the significant change and redistribution of the groundwater and surrounding rock stress field. The stress and deformation of supporting structure were highly complex both in space distribution and time development. The research results could provide specific reference and guidance for the design and construction of deep-buried tunnels in naturally water-rich loess.

Study on the Synergistic Effect of Primary Support and Surrounding Rock of Large Buried Depth Tunnel in Soft and Fractured Strata

The soft and fractured strata can cause significant deformation of surrounding rock during tunnel excavation. This study analyzes field monitoring test results and compares numerical simulations from the third bid project of the Dali I section construction within the water diversion project in central Yunnan to address the issue of significant deformation following tunnel excavation in soft and fractured strata. It proposes an optimized support scheme consisting of a densified steel arch and enhanced initial support strength and stiffness. In addition, the research investigates support effectiveness considering varying support strengths and steel arch ring spacing. The study findings indicated the following: (1) The tunnel traverses soft and fractured strata, causing unevenly distributed vertical convergence deformation around the cavern. The maximum settlement occurs at the crown, showing pronounced nonlinearity. (2) The maximum stress in the steel arch is concentrated at the arch crown, measuring −19.02 MPa. The arch remains compressed, with stress decreasing from the crown to the waist. (3) The axial force in the anchor bolt reduces from the crown to the arch’s waist on both sides. As the depth of the rock mass increases, the axial force in each anchor bolt decreases and the tension state is maintained. The maximum axial force reaches 46.57 kN. (4) The maximum displacement decreases from 4.21 to 0.15 cm after the optimized support structure is implemented, demonstrating the optimization scheme’s effectiveness. Future constructions can refer to this scheme and make necessary adjustments based on various terrain conditions to ensure safety.

A Case Study of Tunnel Reinforcement Measure during Traffic Upgrading in Chongqing City, China

Because the urban tunnel is an essential knot of urban traffic and an easy blocking point in busy hours, upgrading the urban tunnel was necessary for the city after the tunnel being in service for a long time. However, to demolish the existing tunnel, some problems may be encountered, and these problems include occurrence of longitudinal cracks at the tunnel vault, increase of load due to infrastructure construction over the tunnel, unloading due to excavation of the rock over the tunnel, and uneven load due to asymmetric excavation or construction. To reinforce a cracked tunnel in Chongqing City, China, steel arches were installed to improve its bearing capacity, but some steel arches failed during the excavation of ground over the tunnel. Therefore, the scheme of “steel arch + shotcrete + tube column + transversal horizontal bracing” (hereinafter referred to as SASTCT) was proposed to ensure tunnel safety due to unloading and uneven load during the subsequent construction procedures. Numerical analysis indicated that the SASTCT measure can ensure the safety of the traffic and subsequent construction, which can provide some suggestions for similar tunnel upgrades in the future.

Backstepping Based Trajectory Tracking Control of a TBM Steel Arch Splicing Manipulator

Backstepping Based Trajectory Tracking Control of a TBM Steel Arch Splicing Manipulator

Fracture characteristic and support effect around deep lined tunnels using CGP-FDEM simulation and field investigation analysis

The lining is one of the main methods of support and is chosen as the primary support for composite and reinforced roadways during mining excavation. Systematic investigations into the supportive effect of lined roadways in deep weak rock masses are highly desirable to improve support design and enhance roadway stability. The fracture characteristics and deformation are more prominent in the lining failure and damage to the surrounding rock. For investigations into the fracture mode and failure characteristics of the lining support, this study proposed a lining element support model in the graphics processing units (GPU) parallel combined finite-discrete element method (FDEM) program using compute unified device architecture (CUDA), referred to as CGP-FDEM. The lining element model and excavation simulation method are implemented in the CGP-FDEM aim of simulation large-scale rock fractures in underground excavations. On this basis, the simulation of deep roadway excavation is performed under various support conditions, including low-strength and high-strength shotcrete, steel arch, and U-profile yieldable steel. Further, a comparative analysis is conducted between the field investigation and simulation results, focusing on fracture-fragmentation and large deformation of the surrounding rock, as well as the failure and fracture mode of the lining elements. Results of individual support effects indicate that the reinforcement conditions mainly affect the excavation damaged zone (EDZ) and the deformation of the surrounding rock. Rock fragmentation and buckling intensify the large deformation and instability of the roadway. Fracture evolution and instability of the surrounding rock can easily occur in weak areas due to severe stress concentration and the accumulation and release of energy. Based on the analysis, the principle of "uniform reinforcement of reactive force throughout the entire section" is proposed to alleviate stress concentrations and maintain the overall stability of the excavation space.