摘要:
The existing calculation process of the cantilever cast arch-cable force has a poor fit with the actual process, leading to the lack of good parameter corrections. To improve the overall control quality of the linearity and stress of the arch ring, there is an urgent need for a solution method with higher flexibility and better practicability. Combined with the existing research results, this study proposes a multi-loop nesting algorithm. The algorithm decomposes the whole construction process into individual subsystem control modules, and sets the control indexes of stress and displacement in individual control modules. Subsequently, the analysis and calculation of other modules are completed according to the construction sequence until structure closure. Finally, we determine whether the overall construction control indexes meet the requirements. According to the findings, the results obtained by this algorithm meet the design requirements, and its applicability is verified. Compared with other algorithms, the algorithm is more effective in controlling the stress and deformation of the arch ring during the construction process. This algorithm solves the dispersion between structural systems in previous calculations and has more flexible parameter and control index settings. Additionally, the calculation control idea of this algorithm can be further extended to the construction control of the "cable-beam" cantilever structure.
摘要:
Cracking behaviour of silty mudstone with existing flaws can trigger slope instability. However, the mechanics of multi-fractured silty mudstone have not been adequately examined. To handle this issue, the study employs a comprehensive approach to investigate the mechanical characteristics and cracking mechanism of fractured silty mudstone combing uniaxial compression test conducted by similar material specimens, cracking strength model, macro damage model, and PFC2D. Similar material specimens containing prefabricated fractures are prepared using steel sheet insertion during curing. Results show that peak strength initially decreases and subsequently increases as the facture dip angle (beta) increases, minimizing at 45 degrees under uniaxial compressive load. The more fracture there exists, the greater reduction in peak strength. The failure morphology of fractured silty mudstone can be categorized into tensile failure, shear failure, and tensile-shear combined failure. Theoretical models confirm that the crack strength depends on beta and fracture length (a), aligning with experimental results while crack strength exhibit inversely proportional to a. The simulation results are in good correlation with test results, verifying the reliability of the simulated approach combined with theoretical analysis. Overall, the novel contribution of this paper lies in the multilateral elucidation of the failure mechanism in silty mudstone containing multiple fractures.
摘要:
Long-span suspension bridges experience complex dynamic interactions with stochastic traffic, which has a critical impact on the design and safety assessment of bridges. In this study, a traffic-bridge interaction (TBI) framework is proposed for suspension bridge dynamics analysis by considering realistic traffic behavior and real vehicle characteristics. A stochastic traffic simulation model aiming to faithfully reproduce realistic traffic flow is developed by integrating the Monte Carlo approach and an intelligent driving model. The key parameters of the stochastic traffic model are input into the refined vehicle model established and the bridge model is built. The vehicle and bridge models are coupled by an interface contact method to obtain a complete TBI framework. The TBI framework is applied to a prototype long-span suspension bridge to fully investigate the effect of stochastic traffic flow loads on the vertical vibration of the bridge. Furthermore, the effect of stochastic traffic flow loads on the vertical displacement of a bridge is evaluated by varying key parameters in the TBI framework, such as traffic density and road roughness. The study provides a novel perspective on the refined dynamic analysis of sus-pension bridges under complex traffic conditions, which can further serve as a reference for the safety assessment of suspension bridges.
摘要:
To date, many numerical studies on rock fractures are based on complete models with simple geometric parameters, ignoring the effects of microstructures on the strength and fracture properties of rocks. It is difficult to incorporate the influences of microstructures in simulations of crack initiation, propagation and coalescence by these numerical models. Thus, to explore the fracture and failure processes of rocks under the accumulation of stress, the influences of microstructures should be considered in establishing a numerical model. Spatial data about the internal microstructures and mechanical parameters of porous sandstone are obtained by computed tomography (CT) and triaxial compression experiments. Due to the limitations of the observation range of CT, a novel continuous reconstruction method is proposed to study the failure mechanisms of rocks on the microscale. The main difference between this continuous reconstruction method and our previous reconstruction method is the continuity of the microstructures in the reconstruction process. In addition, the definitions of the probability functions are completely different. The rock model is reconstructed based on the spatial information about microstructures. With the reconstruction model and mechanical parameters, the fracture processes of rocks in the triaxial test are analysed while considering microstructures. In the generation of the rock model, the meshes and elements are optimized regarding skewness, aspect ratio, and tetrahedral collapse value, which improves the calculation efficiency. The fracture properties of the reconstructed model are investigated by a coupled finite element-smoothed particle hydrodynamics (FE-SPH) method. Based on the numerical results, the failure mechanisms of sandstone are analysed through their microstructures. The numerical and experimental results are compared to validate the proposed reconstruction method.
摘要:
In this study, we investigated the effects of concentration and modulus of alkaline activator, liquid–solid (L/S) ratio, and sand volume fraction on rheological properties and flowability of metakaolin (MK)–ground granulated blast furnace slag (GGBFS) geopolymer slurry (pastes and mortars). The rheological property of geopolymer slurry was consistent with the Bingham model. A decrease in the modulus and the L/S ratio, or an increase in the concentration increased the plastic viscosity of geopolymer paste. The geopolymer pastes with higher plastic viscosity exhibited a lower fluidity. The yield stress of geopolymer paste was negatively correlated with concentration, modulus, and L/S ratio. An increase in the sand volume fraction increased the plastic viscosity and yield stress of geopolymer mortar, and decreased the consistency and fluidity of that. Moreover, the correlation between rheological parameters of the geopolymer mortar and paste, and the relationship between the flowability parameters and rheological parameters of geopolymer slurry were constructed.
作者机构:
[吴肖波] State Key Laboratory for Health and Safety of Bridge Structures, Wuhan;430034, China;China Railway Bridge Science Research InstituteLtd., Wuhan;[张迅; 韩艳] School of Civil Engineering, Changsha University of Science and Technology, Changsha;410114, China
通讯机构:
[Zhang, X.] S;School of Civil Engineering, China
摘要:
The ceramic waste powder (CWP) is generated in the ceramic industry during the cutting and polishing stages. It is harmful to the environment and needs a massive area for disposal. Therefore, an alternative way is required to reduce the environmental pollution and landfill caused by CWP. The aim of the study is to establish an Artificial Intelligence (AI) model for CWP concrete from the experimental results to save time and cost. Advancements in AI have made the estimation of concrete mechanical characteristics possible by employing Machine Learning (ML) approaches. In the current study, 60 concrete mixes with waste CWP are made as a partial replacement of cement by 10% and 20%. The plain concrete's ultrasonic pulse velocity (UPV) is taken as a reference. Furthermore, supervised ML techniques (i.e., Bagging, XG Boost, AdaBoost) and standalone (Decision tree) are employed to foresee the UPV of CWP concrete (CWPC). The prediction model's performance is evaluated using R2, Root Mean Square Error (RMSE) values, and Mean Absolute Error (MAE). The k-fold cross-validation is used to validate the performance of the prediction model. The XG Boost model, with an R2 value of 0.95, performed better compared to Bagging, AdaBoost, and DT models. Among all ensemble and individual models, the XG Boost model performs better with higher R2 and lower RMSE (0.081 km/s) and MAE (0.063 km/s) values. Therefore, the CWPC, as a construction material, would reduce land degradation and water pollution. In addition, applying ML techniques for estimating concrete characteristics would have reduced the consumption of efforts, resources, and time of researchers in the construction sector. (c) 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
摘要:
Efflorescence is a concerning issue in geopolymer formulations. By accelerating efflorescence, the efflorescence behavior and compressive strength evolution were analyzed for metakaolin (MK)-based geopolymers cured at various temperatures and times. Mercury Intrusion Porosimetry (MIP) was the primary characterization method utilized in this study. Based on the pore structure, we identified the influence of pore structure on efflorescence behavior and compressive strength evolution. Those results showed that long-term and initial high-temperature curing played a negative role in mitigating efflorescence. Long-term curing refined the pore size, facilitating alkali salt migration to the surface. Initial high-temperature curing enhanced pore connectivity, which facilitated alkali salt movement. The number of pores below 20 nm governs the effect of efflorescence on compressive strength. Crystallization degrades geopolymer with a large number of pores below 20 nm. This study provides a new understanding of the effect of pore structure on efflorescence and the evolution of compressive strength during efflorescence and facilitates optimization of geopolymer formulations to relieve efflorescence.