Search Results (28)

Prefabricated assembly structures play a pivotal role in modern building construction and underground transit developments, offering benefits such as ease of installation, rapid construction, and environmental sustainability. These prefabricated assembly structures are always symmetric and particularly prevalent in projects like subway station construction, where symmetry prefabricated blocks are commonly used. The hoisting and overturning of these blocks are crucial stages in the construction sequence. Given the substantial weight (tens of tons) and size (several meters) of these prefabricated elements, the materials and structural integrity of the metal components, including bolts and steel rods, must meet strict standards during these phases. To ensure stability during overturning and safety throughout hoisting, this paper utilizes a finite element model to analyze the hoisting and overturning of three prefabricated blocks used in subway station assembly. This paper investigates the mechanical behavior of embedded components, such as lifting lugs, steel liners, and hoisting steel rods, during these processes, analyzing their stress and strain. The selection methods of different steel bars (diameter, hollow, solid, etc.) in the hoisting process were obtained, and the operation speed in the hoisting and overturning process was determined, which guided the selection of the hoisting position when the common overturning action was known. The results offer valuable guidelines for the placement and spacing of lifting lugs, as well as the optimal hoisting speed, thereby informing the selection of embedded lifting lugs and the design of operational protocols in actual assembly construction. Full article

Single-sided formwork supporting systems (SFSSs) play a crucial role in the urban construction of retaining walls using cast-in-place concrete. By supporting the formwork from one side, an SFSS can minimize its spatial footprint, enabling its closer placement to boundary lines without compromising structural integrity. However, existing SFSS designs struggle to achieve a balance between mechanical performance and lightweight construction. To address these limitations, an innovative instrumented SFSS was proposed. It is composed of a panel structure made of a panel, vertical braces, and cross braces and a supporting structure comprising an L-shaped frame, steel tubes, and anchor bolts. These components are conducive to modular manufacturing, lightweight installation, and convenient connections. To facilitate the optimal design of this instrumented SFSS, a physics-constrained generative adversarial network (PC-GAN) approach was proposed. This approach incorporates three objective functions: minimizing material usage, adhering to deformation criteria, and ensuring structural safety. An example application is presented to demonstrate the superiority of the instrumented SFSS and validate the proposed PC-GAN approach. The instrumented SFSS enables individual components to be easily and rapidly prefabricated, assembled, and disassembled, requiring only two workers for installation or removal without the need for additional hoisting equipment. The optimized instrumented SFSS, designed using the PC-GAN approach, achieves comparable deformation performance (from 2.49 mm to 2.48 mm in maxima) and slightly improved component stress levels (from 97 MPa to 115 MPa in maxima) while reducing the total weight by 20.85%, through optimizing panel thickness, the dimensions and spacings of vertical and lateral braces, and the spacings of steel tubes. This optimized design of the instrumented SFSS using PC-GAN shows better performance than the current scheme, combining significant weight reduction with enhanced mechanical efficiency. Full article

In the domain of bridge I-beam joint construction, conventional approaches such as cast-in-place concrete with suspended formwork and ordinary reinforced concrete precast slabs entail numerous limitations. The former features complex procedures, elevated costs, and significant safety risks, while the latter is hindered by the heavy weight of precast slabs, which causes difficulties in transportation and hoisting, inconvenient installation, and high costs. Reactive powder concrete ultra-thin precast slab (RPCUPS) is regarded as a potential solution due to its superior properties. Nevertheless, at present, there is an acute paucity of experience and research regarding the application of RPCUPS in bridge I-beam joints, particularly on a large scale. In a certain actual engineering project, a scheme was proposed to employ RPCUPS with a mere thickness of 20 mm in the bridge I-beam joints. In this scheme, the quantity of slabs is substantial, amounting to over 600,000. This constitutes the research gap and impetus of this study, with the aim of filling the existing knowledge void and providing technical support for engineering endeavors. This research carried out an extensive experimental test to systematically investigate the mechanical properties and safety of RPCUPS. Firstly, the material performance experiments were conducted to determine the manufacturing process of RPCUPS that meets the performance requirements. Subsequently, loading experiments on specimens under multiple working conditions were performed to disclose the cracking load and ultimate load of the two main types of RPCUPS and to analyze the influences of fiber type, mixing type, steel mesh, and slab thickness on the mechanical properties of RPCUPS (keeps the same volume rate of steel in a slab). Key findings encompass the outstanding mechanical properties and high safety factors of RPCUPS under diverse working conditions. Finally, in light of the actual construction environment, safety verification of temporary loading during actual construction was executed to furnish solid technical support for the practical engineering application of RPCUPS. The experimental results indicate that RPCUPS has been successfully applied on a large scale in actual engineering projects, not only without augmenting the cost but also significantly reducing the construction period by approximately five months, conspicuously enhancing the construction efficiency. These discoveries not only validate the feasibility of RPCUPS in bridge I-beam joint construction but also offer valuable references and guidance for similar future projects. Full article

At present, the selection criteria and configuration methods for fireproof clapboards in cable tunnels are not yet perfect, making it difficult to achieve effective fire protection. Therefore, an equivalent fire condition testing method is proposed to analyze the fire-resistant property of fireproof clapboards of different materials. Firstly, a tunnel fire experiment platform was built to carry out the combustion experiment of the high-voltage cable intermediate joint. The cable combustion equivalent fire source device is developed based on the temperature rise characteristics under different combustion conditions. However, the temperature rise characteristics of the equivalent fire source and the actual cable combustion error are within 10%. Then, four typical fireproof clapboards were tested under equivalent fire sources. The results indicate that the organic molded board has the best performance. In addition, factors such as the thickness, side panel height, and installation method of the fireproof clapboards were tested and analyzed. The results indicate that a minimum thickness of 5 mm for the fireproof clapboard and a height of 200 mm for the side panel of the clapboard are necessary to ensure effective protection. The installation method of hoisting fireproof clapboards can effectively extend the protection time by about 30% compared to the flat method. Full article

The floating hoisting of floating production storage and offloading (FPSO) production modules introduces substantial challenges due to the propensity for excessive deformation within the typical tubular truss structures during operations. This research proposes a temporary reinforcement scheme, leveraging finite element method simulations under wind, wave, and current loads, to mitigate deformation concerns. Utilizing DNV GeniE software, this study establishes a finite element model, simulating the floating lifting process and conducting a comparative analysis between pre- and post-reinforcement scenarios. The results demonstrate a significant reduction in maximum stress and deformation, substantiating the efficacy of the reinforcement strategy and underscoring the safety and reliability of such operations. The successful execution of this methodology heralds a promising avenue for marine engineering practices, advocating for the optimization of large-scale offshore module installation. Full article

Investigating the influence of varying shaft steelwork stiffness on the stability of horizontal mass displacements, which are crucial elements of a conveyance-shaft steelwork system, is a significant step in evaluating the risk of parametric vibrations in steel constructions. While the Rayleigh method is limited to the first approximation in the solution to this analysis, it still provides valuable insights. Our examination indicates that the impact of a varying shaft steelwork system may not be noticeable in practical applications. This is a significant finding, as it suggests that the impact of varying stiffness in real working objects may be ignored, because the increase in the parametric resonance effects is negligible. This underscores the importance of our research in understanding the stability of steel constructions. This research, which involves theoretical analysis, simplifies the dynamic analysis of the conveyance-shaft steelwork system’s behavior. The result of the performed analysis is a valuable equation for predicting stable work in real hoist installations. Full article

The work analyzes the performance assurance of mine hoisting machines, including the problem of the quality of performance of the functions. The quality of functioning allows evaluation of a set of properties of the process of lifting loads, designed to meet the given requirements in accordance with the purpose and evaluated performance indicators. In this case, the quality of the function depends not only on the elements that worked properly or failed during system functioning but also on the moments involving certain changes in the states of the system. The considered system of power supply of mine hoisting installations is rather complex with respect to reliability. The proposed approach allows this rather complex system to lead in terms of the form of a serial connection of elements, allowing for determining the influence of the functioning of its subsystems and electrical equipment on the technological process of cargo lifting in a coal mine. The presented mathematical concept of increasing the reliability and failure-free operation of mine hoisting plants with the help of the developed mathematical model of the mine hoisting plant allowed studying the reliability indicators of the hoisting plant operation and reserving the equipment most effectively to increase reliability. The determination of coupling coefficients in this study made it possible to analyze the impact of the reliability of electrical equipment and power supply systems on the operation of technological machines to improve the reliability of mining equipment and the efficiency of technical systems of mining equipment. Full article

With the development of steel-structure construction technology in high-rise buildings, the design and construction of high-rise steel structures tend to be complicated. Based on the Zhuhai Tiejian Square project, the fluid-structure coupling calculation analysis and on-site monitoring are carried out in view of the wind load of the high-altitude steel-structure connecting bridge in the hoisting stage of the Zhuhai Tiejian Square project. The main structure of the project is four towers and five high-altitude, small-spacing steel structures connecting the four towers. The lifting process of the third zone is taken as the analysis object, and the hoisting idea of “low-altitude hoisting, overall lifting” is adopted. Because the span of the high-altitude steel-structure connecting bridge is small and the installation height is high, the influence of wind load on the hoisting process cannot be ignored. Therefore, the unidirectional fluid-structure coupling model of the high-altitude small-space steel-structure connecting bridge in the third zone was established by using CFD calculation software ANSYS Fluent 2022 R1, and the corresponding flow field and solid calculation results were obtained and analyzed. The analysis results show that the lifting structure still produces a certain deformation when the wind speed is 5 m/s or 10 m/s, and the calculation results show that the stress calculation results are still within the safe range of steel strength for the sensitivity of the lifting structure under wind load. With the increase of wind speed, the local maximum stress of the structure increases greatly, but the overall deformation remains stable, which indicates that the greatest challenge of hoisting steel structures under wind load may be the stability direction rather than the strength, so it is necessary to strictly monitor the displacement deformation of the structure during construction. Then, through the monitoring of the overall lifting process of the high-altitude, large-span, steel-connected structure of Zhuhai Tiejian Square from pre-lifting to formal lifting, real-time monitoring and data analysis show that the lifting process of the high-altitude steel bridge of Zhuhai Tiejian Square is safe and reliable, the force transformation of each component is reasonable, the lifting process is relatively stable, the external environment has little impact, and the expected monitoring effect has been achieved. The calculation simulation and on-site monitoring in this paper can provide theoretical and practical guidance for the construction safety under the influence of wind load in the construction process of high-altitude steel-structure hoisting, and provide an important reference value for similar projects. Full article

Over 50% of nuclear power plants (NPPs) worldwide have operated for over three decades, leading to a surge in decommissioning projects. This study addresses the gap in current guidelines by analyzing risks in nuclear decommissioning. Using the fuzzy-AHP technique, tasks within dismantling radioactive concrete structures are prioritized. Findings reveal structural and human-related risks across five main cutting tasks. Collision emerges as a significant concern, particularly during wire saw installation and concrete block hoisting hole creation. Subcategory risk priorities highlight variations in risk across tasks, with jamming, falling, and falling objects identified as top concerns during wire saw transportation. This study emphasizes the importance of comprehensive risk assessment in enhancing safety during decommissioning. It underscores the need to consider both physical risks and risks to personnel throughout the process. By prioritizing safety, stakeholders can ensure worker safety and operational efficiency while minimizing hazards. This research contributes to standardized safety protocols for nuclear decommissioning worldwide, aligning with sustainable energy practices. The outcomes offer practical insights for safety manual development and decision-making processes. This study represents progress in ensuring safety during nuclear decommissioning, paving the way for further refinement of safety protocols and guidelines tailored to decommissioning sites. Full article

Most commercial elevators for buildings exceeding four stories use a cable-driven traction system. Typically, a single traction machine operates by hoisting the main cable on a traction sheave, thus vertically transporting the elevator car through rotational motion of the sheave. This research introduces a groundbreaking advancement aimed at elevating loading capacity to an unprecedented 50 tons—the highest known in the world. The innovation involves the development of a twin traction system, wherein two traction machines collaborate to lift the elevator. This novel elevator system has demonstrated remarkable capabilities, showcasing the ability to transport up to 300 passengers in a single trip. The installation of this high-capacity elevator system has yielded substantial improvements in construction work efficiency and safety protocols, particularly in scenarios where cranes are traditionally used. The newly developed elevator could lift 50 tons of equipment 60 times a day, whereas the crane was limited to 8 times. The positive impact on labor is also noteworthy, with increased safety and health considerations, especially in adverse weather conditions. By eliminating the need for manual stair climbing, the well-being of the workforce is prioritized. Furthermore, the heightened productivity resulting from a significant reduction in wait times for conventional elevators is a key outcome of this transformative technology. This research not only unveils a groundbreaking twin traction system but also highlights its multifaceted features in enhancing efficiency, safety, and overall productivity in various industries. Full article

To effectively control the stress state and spatial alignment of arch ribs in the cable hoisting construction of a long-span, concrete-filled, steel tube arch bridge and ensure the safety of the structure, it is necessary to calculate and determine the appropriate cable force. Based on the actual project of a double-span, concrete-filled, steel tubular arch bridge, the construction stage of the left span of the bridge from the beginning of construction to the closure is taken as an example. The linear control method of “quiet do not move” is adopted. Based on the principle that the vertical displacement of the front end of the installed segment caused by the self-weight of the new hoisting segment is equal to the vertical displacement of the front end of the previous segment caused by the tension of the new hoisting segment, the tension cable force is calculated by forward iteration. Finally, based on the theory of the stress-free state method, the ideal linear design of the structure was achieved. The results show that after the closure of the bridge, the error range of the cable tension force is −13.33–15.40% on the left bank and −8.37–11.00% on the right bank. The elevation error of the arch rib is −0.003–0.043 m on the left bank and −0.007–0.032 m on the right bank. The overall stress error of the bridge arch is ±7.0 MPa. The error between the theoretical value and the actual value is within the scope of the specification requirements, which meets the specification requirements. After the closure, the arch shape of the bridge meets the smooth requirements. Full article

The large-segment hoisting construction technology for bridges is increasingly widely used due to its flexibility and efficiency, although it also poses challenges to construction monitoring. Traditional monitoring technology is unitary with low data processing efficiency, making it difficult to meet the accuracy requirements of large-segment hoisting. The application of digital technology has brought about an opportunity for innovation in bridge construction monitoring technology. To address existing challenges and explore digital applications, this paper takes the integral hoisting construction control of the large-segment steel box girder in a large cross-sea bridge as an example, developing an alignment, stress, and temperature monitoring scheme by taking the key points of hoisting construction control into consideration. A monitoring platform was developed, and the workflow of large-segment hoisting construction monitoring is systematically summarized from the viewpoint of practical engineering, which provides a valuable reference for achieving precise and efficient construction monitoring and control in similar projects. Full article

Steel structures have been widely used in large public venues and super-high-rise buildings due to their strong spatial flexibility, good seismic performance, and beautiful appearance. For buildings with high lighting requirements, such as shopping malls, stadiums, and exhibition halls, a super-large day-lighting roof with light-transmitting steel structures is to be designed on top. However, it is impossible to directly hoist large steel structures with cranes in buildings, and the installation of steel structures at uneven roof elevations usually requires full hall scaffolding, which is inefficient and time-consuming. Based on the existing construction methods, this paper proposes a construction technology for column replacement integral accumulation sliding at uneven elevations for steel structures. This technology can improve the construction efficiency and reduce the construction cost of steel structures at uneven elevations. Full article

As sustainable structures like steel structures become more widely used, so do their construction issues. Improper lifting measures of long-span spatial steel structures may delay the construction period and even cause safety accidents. These problems have hindered the realization of sustainable buildings. Few studies on long-span spatial steel structures considered time-varying mechanical characteristics during the construction process. During the construction process, it will be found that the installed structure does not meet the required accuracy, and the installed content needs to be removed and re-constructed. This will cause idle work and rework, which will result in a waste of resources and is not conducive to sustainable development. Therefore, it is necessary to study the lifting construction process of long-span spatial steel structures and form a refined construction method. Based on the lifting construction process of the maintenance hangar roof of Chengdu Tianfu International Airport, this study proposes a time-varying mechanical analysis method for synchronous and asynchronous integral lifting of long-span space steel structures basing the Building Information Model (BIM). The force on the lifting point is analyzed during the hoisting construction process when the single-point asynchronous integral lifting and the interlaced point asynchronous integral lifting are carried out. The adverse effect of the displacement difference between lifting points during asynchronous integral lifting is proved. It provides a reference for the safe construction of long-span spatial steel structure lifting and also helps to improve the sustainability of construction projects. Full article

The cold box is a crucial component for cryogenic distillation in air separation units. With the increasing focus on energy conservation and emissions reduction, the integral hoisting of the cold box has emerged as a viable alternative to traditional cold box installation due to its highly efficient performance, short cycle time, and superior integration capabilities. Nonetheless, there are concerns surrounding the large size and weight of these boxes, as well as their eccentric structure, which can cause significant challenges during the integral hoisting process and pose safety hazards. To address these issues, this paper proposes a method for optimizing the lifting point of an extra-large cold box through dynamic simulation under actual working conditions. Firstly, a transient structure FEM simulation was carried out using multi-type mesh coupling based on the operating conditions of an extra-large cold box. Secondly, the posture and strength of the box during the hoisting process were analyzed to determine the most dangerous working conditions. Finally, the maximum equivalent stress of the trusses was employed as the fitness function of the particle swarm algorithm to optimize the lifting point position in the whole parameter range. The findings indicated that the most dangerous situation during the hoisting process occurred near the 0° working condition in the flip-up process and that optimizing the lifting point position based on this working condition significantly reduced the stress levels on the trusses. Full article