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Life-cycle failure probability analysis of deteriorated RC bridges under multiple hazards of earthquakes and strong winds

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Earthquake engineering and engineering Vibration 2022年第3期21卷 811-823页

作者： Zheng Xiaowei Li Hongnan Jiangsu Key Laboratory of Environmental Impact and Structural Safety in Engineering School of Mechanics and Civil EngineeringChina University of Mining and TechnologyXuzhou 221116China State Lab.of Coastal and Offshore Engineering Faculty of Infrastructure EngineeringDalian University of TechnologyDalian 116024China

engineering structures may be exposed to one or more extreme hazards during their *** structural design specifications usually treat multiple hazards separately in designing structures and there is a limited probabilistic basis on extreme load ***,the performance of engineering structures will be deteriorated by the aggressive environments during their service periods,such as chloride attack,concrete carbonation,and wind-induced *** study presents a probabilistic methodology to assess the time-dependent failure probability of RC bridges with chloride-induced corrosion under the multiple hazards of earthquakes and strong *** loss of cross-section area of reinforcements and the reduction in strength of reinforcing steel and concrete cover induced by the chloride attack are ***,the Poisson model is employed to obtain the occurrence probabilities of the individual and concurrent earthquake and strong wind *** convolution integral is used to determine the joint probability distribution of combined load effects under simultaneous earthquakes and strong *** results indicate that the structural failure probability under multiple hazards increases significantly during the bridge′s life-cycle due to the chloride corrosion *** contribution of each hazard event on the total structural failure probability varies with ***,neglecting the combined influences of multiple hazards and chloride-induced corrosion may bring erroneous predictions in failure probability estimates of RC bridges.

关键词： life-cycle multihazard chloride occurrence model failure probability

Predicting torsional capacity of reinforced concrete members by data-driven machine learning models

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Frontiers of structural and Civil engineering 2024年第3期18卷 444-460页

作者： Shenggang CHEN Congcong CHEN Shengyuan LI Junying GUO Quanquan GUO Chaolai LI School of Mechanics and Civil Engineering China University of Mining and TechnologyXuzhou 211116China Jiangsu Key Laboratory Environmental Impact and Structural Safety in Engineering China University of Mining and TechnologyXuzhou 211116China China Nuclear Power Design Co.Ltd. Shenzhen 518031China School of transportation and science engineering Beihang UniversityBeijing 100191China China Construction First Group Corporation Limited Beijing 100161China

Due to the complicated three-dimensional behaviors and testing limitations of reinforced concrete(RC)members in torsion,torsional mechanism exploration and torsional performance prediction have always been *** the present paper,several machine learning models were applied to predict the torsional capacity of RC *** results of a total of 287 torsional specimens were collected through an overall literature *** of extreme gradient boosting machine(XGBM),random forest regression,back propagation artificial neural network and support vector machine,were trained and tested by 10-fold cross-validation *** performances of proposed machine learning models were evaluated and compared,both with each other and with the calculated results of existing design codes,i.e.,GB 50010,ACI 318-19,and Eurocode *** results demonstrated that better predictive performance was achieved by machine learning models,whereas GB 50010 slightly overestimated the torsional capacity,and ACI 318-19 and Eurocode 2 underestimated it,especially in the case of ACI *** XGBM model gave the most favorable predictions with R^(2)=0.999,RMSE=1.386,MAE=0.86,andλ=***,strength of concrete was the most sensitive input parameters affecting the reliability of the predictive model,followed by transverse-to-longitudinal reinforcement ratio and total reinforcement ratio.

关键词： RC members torsional capacity machine learning models design codes

Ai-Based Evaluation Method of Mechanical Performance of Shield Tunnel Structures after Fire

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SSRN 2023年

作者： Lu, Yaoliang Jiang, Jian Wang, Bo Chen, Wei Ye, Jihong Jiangsu Key Laboratory of Environmental Impact and Structural Safety in Engineering China University of Mining and Technology Xuzhou221116 China

An accurate and efficient evaluation of mechanical properties of tunnel structures after fire is crucial for ensuring the reliability and cost-effectiveness of emergency disposal and repair work. In this study, an evaluation model is established to assess the post-fire bearing capacity of shield tunnels based on AI technology. Numerical models of both tunnel segments and ring lining structures are first established and validated, where the effect of material constitutive behavior and contact are discussed. The key damage indices and their influence on post-fire behavior of shield tunnels are investigated based on the analytic hierarchy process and numerical simulation. The mechanical performance of tunnels after fire is classified using Q-type system clustering analysis method. The quantitative relationship between damage index systems and performance grades is determined by BP neural network. It is found that the main factors influencing the mechanical performance of shield tunnel structures after fire include the damage indices of spalling depth, concrete deterioration depth, concrete strength reduction, bolt strength reduction, spalling area, concrete deterioration area, and bolt deterioration number. The mechanical performance of tunnels after fire can be classified into five levels according to post-fire residual bearing capacity. The BP neural network can accurately and efficiently predict the performance grade of shield tunnels after fire, providing a useful tool for making wise and fast decision on post-disaster transportation and repair strategy. © 2023, The Authors. All rights reserved.

关键词： Spalling

Deterioration Mechanism of New Grouting Materials under Coupling Effect of Heat Damage and Sulfate Attack 4

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Deterioration Mechanism of New Grouting Materials under Coup...

4th International Symposium on Traffic Transportation and Civil Architecture, ISTTCA 2021

作者： Li, Pengxu Xia, Junwu Zhao, Wenting Jiangsu Key Laboratory of Environmental Impact and Structural Safety In Engineering China University of Mining and Technology Jiangsu Xuzhou221116 China

ISBN: (纸本)9781665425926

Aiming at the typical high temperature sulfate environment in underground engineering, the degradation mechanism of the new grouting material under the coupling action of heat damage and sulfate erosion was studied. Forty-four groups of specimens with different water-binder ratios were prepared. The changes of appearance, mass, compressive strength and sulfate ion content of the specimens under the action of different temperature (20°C, 30°C, 60°C, 90°C) and different sulfate concentration (0, 5%, 10%) were detected, the microstructure was observed by electron microscope (SEM), the content model of sulfate ion was established. The results show that: in the environment of sulfate erosion, high temperature has a significant effect on the deterioration of new grouting materials, the higher the temperature, the more obvious the deterioration. With the increase of water-binder ratio, the deterioration of new grouting materials becomes more and more serious. At the early stage of erosion, ettringite and other materials are gradually formed and continuously filled with pores and microcracks. At the later stage of erosion, the expansion stress of ettringite and the crystallization pressure of sulfate make the material gradually expand and destroy. The model of sulfate ion content established is in good agreement with the experimental results. © 2021 IEEE.

关键词： Deterioration

The hydration simulation and strength prediction of new grouting materials 2

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The hydration simulation and strength prediction of new grou...

2nd International Conference on Advanced Materials and Intelligent Manufacturing, ICAMIM 2021

作者： Xia, Jun-Wu Xu, En-Lai Yu, Lin-Li Han, You-Min Jiangsu Key Laboratory of Environmental Impact and Structural Safety in Engineering China University of Mining and Technology Jiangsu Xuzhou221116 China

The new grouting material is a kind of material which can realize rapid condensation at high w/c and has a broad development prospect in many engineering fields. In order to simulate the hydration process and predict the compressive strength, we establish the hydration model by using CEMHYD 3D program to simulate the hydration process. Based on the hydration simulation results, the strength prediction model was established by using the strength formula of "cement-air ratio". The results show that CEMHYD 3D program can be used to simulate the hydration reaction process of new grouting materials. The strength prediction model based on the hydration simulation results has high reliability with prediction error of less than 10%. © 2021 Institute of Physics Publishing. All rights reserved.

关键词： Hydration

Hybrid Bayesian-Copula-Based Damage Probability Estimation for Steel-Concrete Composite Tall Buildings Under Concurrent Seismic and Wind Loads

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SSRN 2024年

作者： Zheng, Xiao-Wei Cheng, Jie Zhang, Ling-Xin Xie, Xian-Xin Key Laboratory of Earthquake Engineering and Engineering Vibration Institute of Engineering Mechanics China Earthquake Administration Key Laboratory of Earthquake Disaster Mitigation Ministry of Emergency Management China Jiangsu Key Laboratory of Environmental Impact and Structural Safety in Engineering School of Mechanics and Civil Engineering China University of Mining and Technology Jiangsu Xuzhou221116 China

This study proposes a hybrid Bayesian-Copula-based methodology for damage risk evaluation of tall buildings under concurrent seismic and strong wind excitations incorporating various uncertainties. The main contributions of this study to the field of probabilistic multi-hazard risk assessment include: (1) The Bayes statistic method is employed to develop the posterior probability distributions of the unknown parameters in the marginal probability models of an individual earthquake and strong wind as well as parameters involved in the multi-hazard demand model for fragility calculations. (2) The Bayesian-based method is applied to update the existing joint probabilistic model of earthquakes and strong winds. (3) A method is presented to estimate the muti-hazard fragility bounds. Then, the damage risk assessment will quantify epistemic uncertainties of unknown demand model parameters by calculating the full probability. Finally, a representative 42-story composite building is applied to perform this multi-hazard damage risk estimate method. The application of this study indicates the considerable impact of epistemic uncertainties and loading directions on the damage risk. This presented Bayesian-Copula-based method provides great help for the decision-making of tall buildings subjected to multi-hazards. © 2024, The Authors. All rights reserved.

关键词： Tall buildings

Venturi Device for Stable Addition of Fire-Fighting Foaming Agent to Self-Priming Liquids at High Flow Rates

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SSRN 2024年

作者： Lu, Caiyuan Wu, Yuxin Chen, Mujun Liang, Yuntao Key Laboratory of Gas and Fire Control for Mines Ministry of Education Xuzhou221116 China School of Safety Engineering China University of Mining & Technology Xuzhou221116 China Jiangsu Key Laboratory of Environmental Impact and Structural Safety in Engineering China University of Mining and Technology Jiangsu Xuzhou221116 China

To achieve a stable addition of fire-fighting foaming agent under big flow rates, an independently designed Venturi structure with self-suction of liquid and foaming agent was numerically simulated. We simulated the effects of different suction structure diameters, contraction angles, throat length and position on the suction ratio, compared and analyzed the data, and determined the optimal suction structure parameters. The suction ratio stabilizes and then decreases as the outlet pressure increases. At an outlet pressure of 0.48 MPa, the suction ratio remains stable at 1.14%. However, as the outlet pressure increases, the ability of the Venturi structure to add foaming agent to the self-suction liquid decreases under high flow rates, causing the suction ratio to rapidly decrease to a minimum value of 0.55 MPa. The suction ratio shows a tendency to first stabilize and then decrease as the outlet pressure increases. When the outlet pressure reaches 0.48 MPa, the suction ratio can remain stable at 1.14%;as the outlet pressure increases, the addition ability of the Venturi structure with foaming agent added to the self-suction liquid under high flow rate decreases, and the suction ratio rapidly decreases to a minimum value of 0.55 MPa. We have conducted a detailed analysis of the process and flow field of liquid suction. As the pressure ratio increases, the high-speed area of the throat gradually shrinks, and the flow field in the diffusion section fluctuates. When the outlet pressure is 0.6 MPa and the velocity field shifts towards the upper part of the diffusion section, the cavitation area will gradually disappear and lose its liquid suction ability. © 2024, The Authors. All rights reserved.

关键词： Cavitation

Bidirectional Propagation Characteristics of Gas Explosion Disturbed by Accumulated Obstacles with Varied Blockage Ratios

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SSRN 2024年

作者： Lu, Yansen Zhong, Xiaoxing Liu, Zhenqi Zhong, Qiu Chen, Tengfei Key Laboratory of Gas and Fire Control for Coal Mines China University of Mining and Technology Ministry of Education Xuzhou221116 China School of Safety Engineering China University of Mining and Technology Xuzhou221116 China Jiangsu Key Laboratory of Environmental Impact and Structural Safety in Engineering China University of Mining and Technology Jiangsu Xuzhou221116 China

Coal mine gas explosions often occur in confined areas with accumulated obstacles. To investigate the effect of the blockage ratio (BR) of accumulated obstacles on the bidirectional propagation characteristics of gas explosions, this study conducted experiments using different BRs of accumulated obstacles in opposite flame propagation directions in a pipeline. Variations in the flame morphology, speed, and peak explosion overpressure in both directions were analyzed. Results indicate when the BR in either direction reaching 60 % or above, a reverse propagation flame formed in the direction with a larger BR. With one direction completely blocked (BR=100%) and the BR in the other direction lower than 60%, a Helmholtz cloud-like flame formed in the completely blocked direction. Effect of the accumulated obstacles on the flame speed in either direction shifted from suppression to acceleration as the BR in the other direction increased. The relationship between peak explosion overpressures in both directions depended on the BR in each direction. When the BRs in both directions do not exceed 60%, the higher peak overpressure appeared in the direction with a large BR. However, once the BR in either direction exceeds 60%, the peak overpressure was lower in the direction with a larger BR. © 2024, The Authors. All rights reserved.

关键词： Coal mines

Research on Tunnel Vehicle Fire Temperature Field Simulation Considering the Latent Heat of Vaporization Inside Concrete Linings

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SSRN 2023年

作者： Zhang, Yiheng Ye, Jihong Lin, Chunjin Jiangsu Key Laboratory Environmental Impact and Structural Safety in Engineering China University of Mining and Technology Xuzhou221116 China Xuzhou Key Laboratory for Fire Safety of Engineering Structures China University of Mining & Technology Xuzhou221116 China Geotechnical and Structural Engineering Research Center Shandong University Jinan250061 China

Concrete lining serves both as a load-bearing structure and envelop in tunnels. The high temperatures and non-uniform temperature fields caused by fires can lead to the rapid failure of concrete linings, severely affecting tunnel safety. To obtain the temperature distribution of the lining under different fire conditions, simulation research is conducted in this study by using CFD technology. First, the fire resistance test of concrete lining segments is simulated, and a furnace temperature simulation method based on a PID (Proportional-Integral-Derivative) control and a lining heat transfer model considering the latent heat of vaporization (LHV) are proposed. Second, the experimentally verified lining heat transfer simulation method is applied to a full-scale tunnel model to study the tunnel vehicle fire temperature field considering the LHV of the concrete lining. The results show that the method based on the PID control proposed in this paper can accurately simulate the full process of temperature rise and fall in the furnace, replacing the complicated, dangerous, and costly component fire resistance tests. By introducing a vaporization latent heat energy source term, the 100 °C temperature plateau within the concrete lining can be effectively simulated to prevent prematurely determining component failure. Compared to traditional methods, the lining-gas heat exchange boundary considering the LHV is more accurate. The temperature rise at the lining surface and rebar position is slower, with maximum temperature differences of 80 K and 125 K, respectively, after 15 minutes of fire exposure. The aim of this research is to provide a complete temperature rise and fall process, including the 100 °C temperature plateau, for the fire protection analysis and design of tunnel linings and to provide a reference for the safety work zone of fire rescue and post-disaster restoration scope. © 2023, The Authors. All rights reserved.

关键词： Temperature