Bridge Material Research Articles

Research of Optical Fiber Sensing Technology in Bridge Detection

Fiber optic sensing technology is a new type of detection technology that realizes information transmission through total reflection of light and photoelectric conversion. It has been used in the fields of medicine, military, communication, transportation, industrial control, scientific research, etc., especially in the field of bridges for decades.This paper summarizes the research status of optical fiber sensing technology and optical fiber in bridge detection, and reviews the application of optical fiber in bridge detection. First, this paper introduce the optical fiber technology, its working principle and application advantages. Secondly, the feasibility of optical fiber sensing technology in bridge detection is demonstrated through concrete application cases. It includes the detection of bridge structure and the detection of bridge material structure. Through the optical fiber sensing technology, this paper can detect the hidden dangers of the bridge in a timely and non-destructive manner Finally, this paper prospect the future development of optical fiber technology in the field of bridge detection.

Flexible SERS chips for rapid on-site detection of tricyclazole pesticide in agricultural products.

A flexible, ultrasensitive, and practical SERS chip is presented based on a paper/f-TiO2/Ag structure. The chip enhances the self-assembly of Ag nanoparticles on a cellulose fiber matrix, facilitated by smart functionalized TiO2 nanomaterials (f-TiO2). This design enables superior detection of the hazardous pesticide tricyclazole (TCZ) on crops using an advanced, simple, and efficient analytical method.Despite its straightforward fabrication process via a solvent immersion method, the intrinsic smart surface properties of the TiO2 bridging material -both hydrophilic and hydrophobic-enable the uniform and dense self-assembly of hydrophilic Ag nanoparticles (NPs) on the cellulose fiber paper substrate. This innovative design provides superior sensing efficiency for TCZ molecules with a detection limit reaching 2.1 × 10-9M, a remarkable improvement compared to Paper/Ag substrates lacking f-TiO2 nanomaterials, which register at 10-5M. This flexible SERS substrate also exhibits very high reliability as indicated by its excellent reproducibility and repeatability with relative standard deviations (RSD) of only 5.93% and 4.73%, respectively. Characterized by flexibility and a water-attractive yet non-soluble surface, the flexible Paper/f-TiO2/Ag chips offer the convenience of direct immersion into the analytical sample, facilitating seamless target molecule collection while circumventing interference signals. Termed the "dip and dry" technique, its advantages in field analysis are indisputable, boasting in situ deployment, simplicity, and high efficiency, while minimizing interference signals to negligible levels. Through the application of this advanced technique, we have successfully detected TCZ in two high-value crops, ST25 rice and dragon fruit, achieving excellent recovery values ranging from 90 to 128%. This underscores its immense potential in ensuring food quality and safety. As a proof of concept, flexible Paper/f-TiO2/Ag SERS chips, with a simple fabrication process, advanced analytical technique, and superior sensing efficiency, bring SERS one step closer to field applications beyond the laboratory.

Effectiveness of autologous interposition saphenous graft in the creation of proximal arteriovenous fistula: Our initial experience

Abstract: For the individuals with end-stage renal disease, maintenance hemodialysis is a common treatment. When we compare to dialysis catheters or prosthetic grafts, arteriovenous fistula (AVF) is associated with a greater maturation period but a smaller incidence of infections, central venous stenosis, hospitalizations, and mortality. Fistulas mature by a dynamic process which is known as venous arterialization, where the breakdown of elastin and release of nitric oxide promote the functional and structural remodeling of the venous wall, permitting the expansion of venous outflow. Veins made them exposed to the arterial environment at the time of venous grafts and AVFs creation. Successful adaptation of the vein to the arterial flow is the most demanding part for long-term success, identified by venous dilation followed by wall thickening. Arteriovenous fistulas (AVF) and grafts (AV graft) are the commonest form of vascular access used for maintenance of hemodialysis. In general AVF is superior than AV graft in terms of its durability, patency, complication rate and overall survival of patients. But when the calibre of the vein is not satisfactory or length is not adequate to make tension free anastomosis, interposition graft is used. Most commonly used bridging material is polytetrafluoroethylene (PTFE) polymer. In this case, we used an interposition graft of the saphenous vein for making dialysis access on a 38 year old male patient having renal insufficiency and evaluated its efficacy in maintaining flow.

Intense pulsed light-induced millisecond selective heat treatment for high-performance silicon anodes

Silicon, which is gaining prominence as a potential anode material, exhibits long-term cycle stability issues owing to volume changes during cycling. This study presents a meticulously designed Si anode that employs intense pulsed light (IPL) technology to simultaneously reduce carbon additives and construct an effective carbon quantum dot (CQD)-derived binder system. IPL, as a light-material interaction technique, offers a novel approach for selective heat treatment with remarkably short processing durations on the order of milliseconds. By comprehensively considering the geometric structure, optical characteristics, and thermal properties of each electrode component, heat transfer bridge (HTB) materials are introduced to ensure a homogeneous depth-directional heat treatment and to minimize binder decomposition in the IPL process. By employing HTB materials, the binder can reach a controlled target temperature for the condensation reaction between poly (acrylic acid) and the CQDs. Simultaneously, higher heat generation in the conductive carbon than in the binder leads to selective additional carbon reduction. This unique approach provides selective heat treatment, which cannot be achieved using conventional methods, resulting in a Si anode with excellent cyclic stability and rate capability. The versatility of the IPL technology is further demonstrated by applying it to relatively inexpensive Si microparticles.

Bamboo as a Building Material

Abstract: Bamboo is a versatile and remarkable plant; it is famous for its rapid growth, strength and sustainability, making it one of the most valuable and widely used natural resources. Bamboo has been utilized by humans for thousands of years. Its application ranges from construction to furniture and textile industries. In many Asian countries, bamboo is used as a primary building material for houses, bridges and scaffoldings. In recent years, bamboo has gained global recognition as a sustainable alternative to traditional materials. Its versatility, strength and eco-friendliness make it an ideal choice for a wide range of products. As the world becomes increasingly aware of the need for sustainable practices, bamboo stands out as a plant that can contribute to a more environmentally conscious future. The aim of the following study undertaken is to determine the physical and mechanical properties of bamboo for its use in construction industries. For this study, the bamboo samples were collected. Compression test, Water absorption test and Compressive Strength Test on Concrete Cube using stone aggregate and bamboo aggregate were performed. The material (Bamboo) used for these tests are neat, clean and free from any defects

Interfacial cohesion model of ultra‐high performance concrete wet joints under the influence of multiple factors

AbstractThe interfacial cohesion between precast normal concrete (NC) and cast‐in‐place ultra‐high performance concrete (UHPC) is an important index to evaluate their interfacial bond strength, which is of great importance for the application of UHPC as a connection material for precast structural bridges. Interfacial cohesion is related to several influencing factors. However, there needs to be more research on the interrelationship model between multiple influencing factors and interfacial cohesion. This study took the UHPC wet joint in a precast concrete structure as the object. First, the relationship between the interface cohesion of UHPC wet joint and substrate strength, UHPC age, interfacial roughness, interfacial moisture content, and curing method was studied; The result shows that the key factors affecting interfacial cohesion include UHPC age, interface roughness, and substrate strength, with interfacial moisture content potentially playing a secondary role. Second, the failure types of the interface zone surface by using digital image correlation (DIC) are divided into three categories. Finally, the quantitative mathematical model of interfacial cohesion under the coupling effect of multiple factors was established based on the above four factors. The model is in good agreement with the experimental data.

Study on the Vibration Effects of Cyclic Blasting on Bridge Structures under Construction

This study investigates the impact of cyclic tunnel blasting on adjacent bridge structures under construction. Monitoring vibration velocities of the bridge deck, piers, and middle column adjacent to the Zhanma Tian Tunnel, a three-dimensional numerical model was developed using FLAC3D software, utilizing blasting vibration test data from the Zhanma Tian Tunnel project in Guizhou. Results show that, as the distance between the bridge and tunnel increases, vibration velocity at the bridge deck decreases more rapidly compared to the base of the pier. Peak vibration velocities recorded were 0.235 cm/s for the bridge deck, 0.081 cm/s for the pier base, and a predicted 0.209 cm/s for the middle column. The impact order from blasting vibrations on the bridge structure is: pier base, middle column, bridge deck. Peak vibration velocity induced by blasting ranged between 0.05 and 0.25 cm/s, within safe limits of bridge material strength. Eight daily blasting cycles do not compromise the safety of bridge structures located 43 m away.

Fracture Pre-propping and Temporary Plugging for Formation Damage Control in Deep Naturally Fractured Tight Reservoirs

Summary To address the challenges of formation damage related to drill-in fluid loss into deep reservoir fractures during the drill-in process, we propose pre-propping and temporary plugging (PPTP) technology as an integrated solution in this paper. The PPTP approach combines high-strength bridging (HSB) materials with self-degrading filling (SDF) materials for efficient fracture plugging during lost circulation and effective fracture propping during oil and gas production from deep naturally fractured reservoirs. HSB material with good mechanical properties and SDF material with a controllable degradation cycle are developed and systematically evaluated. Fracture plugging tests and stress sensitivity experiments are conducted to evaluate the transformation effect of fracture plugging zones on fracture propping zones. Research results show that the developed HSB material exhibits a high compressive capacity and friction coefficient, which maintains a crushing rate below 3% under 60 MPa pressure and an average friction coefficient of 1.56. The degradation ratio of SDF material increases with temperature and pH value. The degradation cycle can reach up to 168 hours under the conditions of 120°C and pH = 13, which ensures continuous stable fracture plugging and lost-circulation control during the drill-in process. The PPTP technology, combining HSB and SDF components, efficiently plugs fractures with widths ranging from 1.0 mm to 3.0 mm, with a maximum plugging pressure of up to 10.16 MPa. HSB material props the fractures after SDF degrades, preventing fracture closure and converting the fracture plugging zone into a propping zone. The stress sensitivity damage of reservoir fractures can be effectively mitigated, preserving and enhancing fracture conductivity. Thus, the PPTP technology shows great potential for the integration solution of drill-in fluid loss and formation damage in deep naturally fractured reservoirs.

Experimental study on the design method of lost circulation materials for induced fractures

Owing to the influence of fluctuating wellbore pressure, the fracture width in formations with induced fractures changes dynamically. However, the traditional design method for fracture plugging materials is based on a static fracture width, which leads to the easy destruction of the plugging layer established underground and a high risk of secondary loss. Until now, the treatment of lost circulation in formations with induced fractures still faces significant challenges. Therefore, a dynamic fracture plugging experimental device was developed in this study to investigate the bridging–plugging process of lost circulation materials (LCMs) within induced fractures, as well as the design criteria for LCMs for induced fractures. Experimental results show that through adjusting the mass ratio and total concentration of the three-level bridging material, the plugging position of the bridging material can be changed, and the fracture reopen pressure can be increased. When the mass ratio of the three-level bridging material satisfies primary bridge particle: secondary bridge particle: tertiary bridge particle = 1:1:2 and the total concentration is greater than 5%, the plugging material compounded with the three-level bridging material is prone to retention in the induced fractures, exhibiting short bridging time, low permeability of the formed plugging layer, and high fracture initiation pressure. It can effectively prevent the opening of fractures or the generation of new induced fractures, thereby reducing the risk of secondary loss. The research results can provide a scientific theoretical basis for the loss control of induced fractures.

Dynamic leaching assessment of recycled polyurethane-coated tire rubber for sustainable engineering applications

Assessing the material ramifications of waste tire rubber stands as a pivotal endeavor for its practical utility. Dynamic leaching analysis emerges as indispensable in delineating its potentialities within sustainable engineering domains. Waste materials stemming from tire recycling industries, notably polyurethane-coated rubber (PUcR), may exhibit promising viability owing to attenuated leaching, thus fostering the circular economy paradigm. Towards this end, upflow column percolation leaching tests were conducted on recycled rubber-soil mixture (RSM) alongside PU-coated rubber-soil mixture (PUcRSM). Analysis through Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) unveiled the leaching dynamics of assorted metals in RSM and PUcRSM, notably showcasing markedly diminished cumulative zinc content (by 99.4%) in PUcRSM, coupled with mitigated electrical conductivity, redox potential, and eluate pH. Leveraging HYDRUS-1D for analytical modeling predicated on the advection-dispersion equation further underscored these insights. These findings suggest that waste PUcR presents itself as a viable option, distinguished by its diminished leachability, suitable for a wide array of applications. These applications include vibration damping in infrastructure, tunnel linings, asphalt roads, rubberized concrete, and lightweight backfill materials for bridges and retaining walls, among others. This initiative will contribute to recycling a substantial quantity of over 1 billion used tires produced annually, ultimately supporting the circular economy ethos through assured and adaptable repurposing of waste from tire rubber recycling industries.

Research on Quantification of Structural Natural Frequency Uncertainty and Finite Element Model Updating Based on Gaussian Processes

During bridge service, material degradation and aging occur, affecting bridge functionality. Bridge health monitoring, crucial for detecting structural damage, includes finite element model modification as a key aspect. Current finite element-based model updating techniques are computationally intensive and lack practicality. Additionally, changes in loading and material property deterioration lead to parameter uncertainty in engineering structures. To enhance computational efficiency and accommodate parameter uncertainty, this study proposes a Gaussian process model-based approach for predicting structural natural frequencies and correcting finite element models. Taking a simply supported beam structure as an example, the elastic modulus and mass density of the structure are sampled by the Sobol sequence. Then, we map the collected samples to the corresponding physical space, substitute them into the finite element model, and calculate the first three natural frequencies of the model. A Gaussian surrogate model was established for the natural frequency of the structure. By analyzing the first three natural frequencies of the simply supported beam, the elastic modulus and mass density of the structure are corrected. The error between the corrected values of elastic modulus and mass density and the calculated values of the finite element model is very small. This study demonstrates that Gaussian process models can improve calculation efficiency, fulfilling the dual objectives of predicting structural natural frequencies and adjusting model parameters.

Optimization of the One-Size-Fits-All Layout Problem Based on Preparing Material for Steel Bridges

Before the construction of a bridge begins, workers arrange the necessary parts and then cut and process them. The quality of the cutting layout directly affects the material utilization rate and the efficiency of the subsequent processes. During bridge construction, an intelligent part layout can improve work efficiency, save time, and reduce the labor intensity and production costs for the company. In this study, we studied a layout optimization algorithm, focusing on rectangular parts in the material preparation process. A mathematical model for the rectangular layout problem was constructed, and a hybrid genetic whale optimization algorithm is proposed that is a combination of the whale optimization algorithm and the genetic algorithm. Based on the “one size fits all” layout strategy, the materials are divided into strips, which are further divided into stacks, serving as the positioning strategy to determine the positional relationships of the parts. Test cases and actual engineering data were used to compare the layouts generated using different algorithms. The results show that the genetic whale algorithm proposed in this paper results in a high utilization rate and is highly effective.

An Experimental Study of Strength Properties of Galvanized Iron (GI) Fiber Reinforced Concrete

Abstract: Fiber Reinforced Concrete is one of the most quality construction techniques of modern times. The utilization of locally available galvanized iron or metallic fiber as a bridging material. The concrete with metallic or nonmetallic fiber is very useful and its enhanced concrete mechanical properties. Therefore, a research has been conducted to study the performance of locally available GI wire fiber reinforced concrete (GWRC). This paper presents the findings of the research that made an effort to explore several basic characteristics of GWRC primarily related to strength, ductility and durability. This research was, therefore, conducted to compare the concrete strength performance of GI fiber with different lengths and a control specimen. The objective of this study is to explore the effect of GI fiber in terms of compressive strength, splitting tensile strength, and flexural strength with ‘Galvanized Iron’ fiber using several cutting lengths of 25 mm and 35mm with various mix proportions including 1.0%, 1.5%, 2.0%, and 2.5% by weight of the concrete

Review on convective and radiation heat transfer between bridges and external environments

The heat exchange between bridges and external environments is the primary cause of the temperature effect on bridges. The complexity of the two-phase (gas–solid) heat transfer mechanism, the diversity of the surface characteristics of bridge materials, and the uncertainties of the environment in which bridges are located make the numerical calculation of the heat exchange between bridges and external environments difficult. Several studies have been conducted by scholars around the world. In this work, the research on convective and radiative heat exchange between bridges and external environments is surveyed, analyzed, and summarized. The influencing factors and calculation methods of bridge temperature are examined, and the convective heat transfer and radiation mechanisms, theoretical calculations, and experimental measurement methods used to investigate the relation between bridges and external environments are summarized and analyzed. The value determination methods for convective heat transfer and radiation absorption coefficients in the calculation of the bridge temperature field are summarized. In addition, the problems and shortcomings of current research are evaluated, and future research directions are identified and discussed.

Molecular and Cytological Identification of Wheat-Thinopyrum intermedium Partial Amphiploid Line 92048 with Resistance to Stripe Rust and Fusarium Head Blight.

Thinopyrum intermedium (2n = 6x = 42, EeEeEbEbStSt or JJJsJsStSt) contains a large number of genes that are highly adaptable to the environment and immune to a variety of wheat diseases, such as powdery mildew, rust, and yellow dwarf, making it an important gene source for the genetic improvement of common wheat. Currently, an important issue plaguing wheat production and breeding is the spread of pests and illnesses. Breeding disease-resistant wheat varieties using disease-resistant genes is currently the most effective measure to solve this problem. Moreover, alien resistance genes often have a stronger disease-resistant effect than the resistance genes found in common wheat. In this study, the wheat-Th. intermedium partial amphiploid line 92048 was developed through hybridization between Th. intermedium and common wheat. The chromosome structure and composition of 92048 were analyzed using ND-FISH and molecular marker analysis. The results showed that the chromosome composition of 92048 (Octoploid Trititrigia) was 56 = 42W + 6J + 4Js + 4St. In addition, we found that 92048 was highly resistant to a mixture of stripe rust races (CYR32, CYR33, and CYR34) during the seedling stage and fusarium head blight (FHB) in the field during the adult plant stage, suggesting that the alien or wheat chromosomes in 92048 had disease-resistant gene(s) to stripe rust and FHB. There is a high probability that the gene(s) for resistance to stripe rust and FHB are from the alien chromosomes. Therefore, 92048 shows promise as a bridge material for transferring superior genes from Th. intermedium to common wheat and improving disease resistance in common wheat.

Experimental and Numerical Analyses of Timber–Steel Footbridges

In addition to traditional building materials, such as steel and concrete, wood has been gaining increasing prominence in recent years. In the past, the use of wood was limited due to its susceptibility to damage by fungi, insects, and temperature. These shortcomings were gradually eliminated as the quality of wood processing increased and thanks to modern high-quality insulating and protective materials. The return to the utilisation of this natural building material was also supported by the development of new wood-based materials, such as glued laminated wood, and new types of mechanical fasteners, as well as by the introduction of new design methods provided in the Eurocodes. Within this context, this paper focuses on using wood in transport infrastructure, especially as the basic material for footbridges and small road bridges. Combined timber–steel bridges emerge as a very effective type of superstructure in contemporary road bridges and footbridges, especially in areas with natural exposure. Usually, wood is used for the main bridge girders, while steel is preferred for bridge deck elements—stringers and cross-girders. The results of this parametric study offer optimal structural solutions for footbridges with spans of 12.0–24.0 m, reflecting satisfactory static and dynamic footbridge behaviour. Particular attention is paid to a problematic structural detail—the connection between the steel cross-girder and the timber main girder. Firstly, this connection’s characteristics were measured experimentally using nine laboratory samples made of two glued laminated timber blocks, simulating main girders connected with a hot-rolled steel cross-girder. The connection was prepared in three variants, with different heights of the end plates and different numbers of bolts. Subsequently, these characteristics were computed using two numerical FEM models. The first model was created using SCIA Engineer software with a combination of shell and beam finite elements. The second, more sophisticated model was created in the ANSYS software environment using 3D finite elements, allowing us to better take into account the plasticity and orthotropic properties of wood and the points of contact between the individual members. Finally, the experimental results produced by sample testing in the laboratory were compared to the outputs of FEM numerical studies.

Manufacturing supported loose-nanofiltration polymeric membranes with eco-friendly solvents on an R2R System

In this study, loose nanofiltration membranes made of polysulfone dissolved in co-solvents PolarClean and gamma-Valerolactone were prepared via slot die coating (SDC) on a roll-to-roll (R2R) system by directly coating them onto a support layer or free standing. A solution flow rate of 20 mL/min, substrate speed of 17.1 mm/s, and coating gap of 0.1 mm resulted in the formation of membranes without structural defects. Pre-wetting the support layer with dope solution minimized shrinkage of membrane layer thickness and improved interfacial adhesion. Membrane samples produced using SDC exhibited properties and performance consistent with bench-scale doctor blade extruded samples; pre-wetted and uncompressed samples (SDC-3) exhibited the highest rejection of bovine serum albumin (99.20% ± 1.31%) and along with adequate mean permeability during filtration (70.5 ± 8.33 LMH/bar). This study shows that combining sustainable materials development with SDC provides a holistic approach to membrane separations to bridge materials discovery and membrane formation.

Dynamic Response of Bowstring-arch Highway Bridge Subjected to Above and Below Deck Close-range Large Explosion

Explosion incidents that are unforeseen can lead to the occurrence of extreme loads, resulting in the generation of remarkably high stress levels within the materials comprising various structures. This can cause significant damage to crucial elements and potentially trigger a disproportionate collapse or even initiate a progressive collapse. Bridge structures, which serve as vital lifelines for cosmopolitan areas and strategic bordering environments, hold immense economic and political significance. The failure of these structures can have severe consequences with far-reaching implications. The use of a steel bowstring-arch bridge is a practical choice for congested crossings and remote border areas where spans are short. However, the current design codes for bridges do not take into account high-strain loadings such as blasts or impacts, nor do they provide recommendations for preventing these occurrences during construction or throughout the lifespan of the bridge. Explosive incidents cause greater damage in terms of material damage and loss compared to earthquakes. There has been limited investigation into how steel-concrete bridges respond to explosions in the past. This study examines the numerical analysis of a bowstring-arch highway girder bridge made of steel and concrete. The bridge is supported at both ends and is subjected to close-range concentric explosions above and below the deck at the center and end of the bridge. To model the bridge and predict its behavior, the authors utilized the Abaqus software suite. For the analysis, a significant quantity of TNT weighing 1.63-tonne has been positioned at the midpoint of the bridge and is defined using the Eulerian-Lagrangian scheme. The transmission of the explosive shockwaves within the bridge material under the given loading circumstances is illustrated and elucidated. The behavior of the bridge is examined in relation to plastic deformations, primary stress, displacement, size of the crater, and overall energy of damage.

DFOS monitoring system of the longest Polish footbridge made of FRP composites

The high durability, low weight, and excellent mechanical properties of fibre-reinforced polymers are the main reasons for the increasing popularity of composites as a material for pedestrian and bicycle bridges. This was also the case with the widening of an existing Carpathian bridge in the centre of Rzeszów (Poland). The new footbridge located next to the bridge consists of five simply supported spans of 4.17 + 23.55 + 23.67 + 23.67 + 23.47 m, with the total length of the superstructure 104.95 m, and is believed to be the longest Polish footbridge made of FRP composites. The footbridge spans were created in the form of sandwich panels, which were manufactured in a single infusion process by the VARTM (vacuum-assisted resin transfer moulding) method. Since the footbridge spans are made of innovative but not fully recognised / proved construction material, a decision was made to equip the structure with a reliable structural health monitoring (SHM) system. The system based on distributed fibre optic sensors (DFOS) was selected and implemented for monitoring. One of the spans was equipped with sensors in the form of SM9 / 125 single-mode fibres in an acrylic coating. The optical fibres of the DFOS system were placed inside the composite structure between the fabrics of the selected laminates, before the infusion process. Because of that, the sensors are completely integrated into the material and are not exposed to damage or the influence of the environment. The paper presents the DFOS SHM system, its implementation in the FRP structure, and the measurement results obtained during the proof load tests performed on the new structure before it was open to the public.

Analysis on the Influencing Factors of Fatigue Damage in Truss Bridge

Truss bridges are susceptible to fatigue damage due to long-term exposure to external factors. This article mainly analyzes the influencing factors of fatigue damage in truss bridges, including load factors and joint factors. The analysis results indicate that load factors have a significant impact on the fatigue damage of truss bridges. Vehicle loads can cause deformation and stress concentration in bridge structures, leading to the generation of shear stress, which in turn triggers the expansion of stress concentration areas and accumulation of fatigue damage in bridge materials. Additionally, improper vehicle operation, such as overloading, can increase the dynamic strain on the bridge deck, causing deformation and fatigue damage to the main girders. As for joint factors, joints are one of the critical areas for fatigue damage in truss bridges. Stress concentration and deformation at joints increase the risk of fatigue crack formation and propagation. In this way, the life and safety of the bridge can be assessed, and appropriate maintenance and repair measures can be taken to improve the fatigue resistance of the bridge and ensure its safe operation.