Mohammad Noori

Fatigue Reliability Assessment of Welded Steel Bridge Decks under Stochastic Truck Loads via Machine Learning

AbstractWelded joints in steel bridge decks are vulnerable to the fatigue damage caused by heavy-loaded trucks. A realistic probabilistic model of truck loads provides a basis for simulating the fatigue stress spectrum of these welded joints, where the fatigue reliability assessment can subsequently be carried out. In this paper, a stochastic fatigue truck load model was developed for probabilistic modeling of fatigue stress ranges to investigate the fatigue reliability of welded steel girder bridges. To deal with the uncertainty-induced computational complexity, a framework including deterministic finite-element-based hot-spot analysis and probabilistic modeling approaches is presented. In addition, a learning machine integrating uniform design and support vector regression is used to substitute the time-consuming finite-element model. The development of both the framework and the learning machine provides a reasonable, efficient, and accurate probabilistic fatigue damage model. Finally, a limit-state fu...

State-of-the-art review of FRP composites for major construction with high performance and longevity

This paper first identifies the need for high performance and longevity of major engineering structures focusing on the problems in current civil infrastructure. Subsequently, it reviews the state-of-the-art research of FRP in structural retrofitting and strengthening and identifies the challenges facing further development of FRP in civil engineering. In order to address the above background, several key scientific issues and corresponding research directions are introduced according to the newly granted National Key Basic Research Program in China, which comprises of: 1) fracture/failure control and probabilistic design of FRP composites and large FRP-reinforced concrete structures; 2) long life-cycle fatigue and creep characteristics as well as service life controllability design of FRP-reinforced structures subjected to multi-field coupled actions; 3) performance of FRP-reinforced structures subjected to extreme environments and extreme loadings as well as methods for performance control; 4) key technologies and their integration for the application of FRP composites in major engineering structures.

A review of the mechanical properties of beetle elytra and development of the biomimetic honeycomb plates

This paper reviews the mechanical properties of beetle elytra. (1) The elytra has a lightweight border frame structure and has an optimal design, which includes variable cross-sections suitable for different positions and enables the required moment of inertia needed for flight. (2) Due to the non-equiangular, laminated structure of the elytra, there are two types of tensile fracture morphologies: fiber breakage and residual bridging. This study demonstrates the anisotropy and the effectiveness of the elytra’s tensile strength by analyzing the orientations of the fibers. (3) The trabecular structure can be used to efficiently improve the peel resistance of the laminated composites, and its three-dimensional strengthening mechanisms have been clarified. (4) A mystery contained in the beetle elytron structures and its biological meanings are revealed, and a biomimetic application example is given. Based on the above points, possible directions for future work are also indicated in this paper.

System reliability-based optimisation for truss structures using genetic algorithm and neural network

Optimum structures must have adequate resistance against external random loads. Since most truss structures involve a series of failure processes, it is necessary to develop system reliability analyses for the optimum design of truss structures. In this paper, a hybrid method of system reliability-based design optimisation (SRBDO) is proposed by combining genetic algorithms (GAs) and radial basis functions (RBFs) neural networks. The proposed method is applied to truss structures, and then the validity is demonstrated through two specific examples. Detailed discussions for the failure sequences such as buckling failure and bending failure are presented. It is concluded that the structural weight increases significantly with the increase of the target system reliability index or the coefficient of variation of design parameters. Results of two optimisation schemes of the steel truss girder show that the cross-sectional areas of the beams are decreased and those of web members are increased.

Reliability analysis of intermediate crack-induced debonding failure in FRP-strengthened concrete members

This paper presents a study on the reliability analysis of intermediate crack-induced (IC) debonding failure, which is a dominant failure mode in concrete members strengthened with externally bonded fibre-reinforced polymer composites. First, the probabilistic characteristics of the model uncertainties for several typical IC debonding models are evaluated and presented, based on a comprehensive test database that contained 217 specimens that experienced IC debonding failure. Second, a Monte Carlo simulation analysis is performed to examine the variability in the IC debonding resistance considering the scatterness of different design variables. Subsequently, the reliability index is estimated by utilising the reliability analysis method, first-order reliability method, for each design case. The effect of each design variable on the average reliability index is examined. Finally, reduction factors for the investigated IC debonding models are calibrated based on the reliability analysis with the aim of meeting a target reliability index of 3.5.

An adaptive support vector regression method for structural system reliability assessment and its application to a cable-stayed bridge

Engineering structures are most statically indeterminate structures consisting of various types of components and their failure modes exhibit randomness under random loads. A new adaptive support vector regression method is proposed for structural system reliability assessment. Compared with traditional support vector regression, the proposed adaptive support vector regression method involves two updating procedures to estimate structural limit state functions. Three verification examples involving a nonlinear limit state function, a truss bridge structure, and a geometrically nonlinear suspended structure are provided to illustrate the accuracy and the efficiency of the adaptive support vector regression method. A pre-stressed concrete cable-stayed bridge is utilized to demonstrate the applicability of the proposed method. The verification studies show that the proposed adaptive support vector regression method is an efficient method with reasonable accuracy for problems where closed-form failure functions are not available and the failure sequences exist in the structural system. The main failure sequences of the cable-stayed bridge are identified. The application studies of the cable-stayed bridge indicate that (a) the foremost failure sequence is the strength failure of side-span cables followed by the bending failure of towers and (b) the secondary failure sequence is the strength failure of mid-span cables followed by bending failure of mid-span girders.

A new ecological control method for Pisha sandstone based on hydrophilic polyurethane

The Pisha sandstone-coverd area is among the regions that suffer from the most severe water loss and soil erosion in China and is the main source of coarse sand for the Yellow River. This study demonstrated a new erosion control method using W-OH solution, a type of hydrophilic polyurethane, to prevent the Pisha sandstone from water erosion. We evaluated the comprehensive effects of W-OH on water erosion resistance and vegetation-growth promotion through simulated scouring tests and field demonstrations on the Ordos Plateau of China. The results of simulated scouring tests show that the water erosion resistance of W-OH treated area was excellent and the cumulative sediment yield reduction reached more than 99%. In the field demonstrations, the vegetation coverage reached approximately 95% in the consolidation-green area, and there was almost no shallow trenches on the entire slope in the treated area. In comparison, the control area experienced severe erosion with deep erosion gullies appeared on the slope and the vegetation coverage was less than 30%. This study illustrated that W-OH treatment can protect the Pisha sandstone from erosion and provide the vegetation seeds a chance to grow. Once the vegetation matured, the effects of consolidation-growth mutual promotion can efficiently and effectively improve the water erosion resistance and ecological restoration.

First-passage Probability of the Deflection of a Cable-stayed Bridge Under Long-term Site-specific Traffic Loading

Long-span bridges suffer from higher traffic loads and the simultaneous presence of multiple vehicles, which in conjunction with the steady traffic growth may pose a threat to the bridge safety. This study presents a methodology for first-passage probability evaluation of long-span bridges subject to stochastic heavy traffic loading. Initially, the stochastic heavy traffic loading was simulated based on long-term weigh-in-motion measurements of a highway bridge in China. A computational framework was presented integrating Rice’s level-crossing theory and the first-passage criterion. The effectiveness of the computational framework was demonstrated through a case study of a cable-stayed bridge. Numerical results show that the upper tail fitting of the up-crossing rate is an appropriate description of probability characteristics of the extreme traffic load effects of long-span bridges. The average daily truck traffic growth increases the probability of exceedance due to an intensive heavy traffic flow and results in a higher first-passage probability, but this increased trend is weakening as the continuous increase of the traffic volume. Since the sustained growth of gross vehicle weight has a constant impact on the probability of failure, setting a reasonable threshold overload ratio is an effective scheme as a traffic management to ensure the bridge serviceability.

Lifetime Deflections of Long-Span Bridges under Dynamic and Growing Traffic Loads

Steady traffic growth may pose a safety hazard to in-service bridges, especially long-span bridges subjected to the simultaneous presence of multiple heavy-duty trucks. This study presents a methodology for evaluating the statistical extrapolation of traffic-load effects on long-span bridges. As part of the contributions advancing the state of the art, this study addresses several challenging issues, including traffic growth, and the resulting dynamic impact, and actual traffic patterns. The nonstationarity of the traffic-load effects due to traffic growth is considered in a series system compounded by several interval traffic models. The dynamic impacts of traffic loads were simulated by a traffic-bridge-coupled vibration system, and the statistical characteristics were captured using a level-crossing model. The actual traffic pattern was simulated by stochastic traffic flows on the basis of the statistics of the weigh-in-motion measurements of a highway bridge. Two numerical examples show the ability of the interval-traffic-growth model to capture the nonstationarity of the growing traffic loads. In addition, a case study of a long-span suspension bridge shows the effectiveness of implementing the proposed methodology for the statistical extrapolation of the maximum deflection. The numerical results of the case study also reveal that the degradation of road-roughness conditions leads to more level crossings but also results in a slight increase in the extrapolation of the deflection. However, traffic growth results in rapid increases in both the extrapolated deflection and the probability of exceedance of the deflection limit.

Erratum to: A new ecological control method for Pisha sandstone based on hydrophilic polyurethane

In this Erratum, we correct the family name of the first author that was spelled as “LINAG” in Journal of Arid Land and the correction is “LIANG”.