Aug 2022, Volume 16 Issue 4
    

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  • RESEARCH ARTICLE
    Zaobao LIU, Yongchen WANG, Long LI, Xingli FANG, Junze WANG

    Real-time dynamic adjustment of the tunnel bore machine (TBM) advance rate according to the rock-machine interaction parameters is of great significance to the adaptability of TBM and its efficiency in construction. This paper proposes a real-time predictive model of TBM advance rate using the temporal convolutional network (TCN), based on TBM construction big data. The prediction model was built using an experimental database, containing 235 data sets, established from the construction data from the Jilin Water-Diversion Tunnel Project in China. The TBM operating parameters, including total thrust, cutterhead rotation, cutterhead torque and penetration rate, are selected as the input parameters of the model. The TCN model is found outperforming the recurrent neural network (RNN) and long short-term memory (LSTM) model in predicting the TBM advance rate with much smaller values of mean absolute percentage error than the latter two. The penetration rate and cutterhead torque of the current moment have significant influence on the TBM advance rate of the next moment. On the contrary, the influence of the cutterhead rotation and total thrust is moderate. The work provides a new concept of real-time prediction of the TBM performance for highly efficient tunnel construction.

  • RESEARCH ARTICLE
    Mansheng LIN, Shuai TENG, Gongfa CHEN, Jianbing LV, Zhongyu HAO

    This paper utilizes three popular semantic segmentation networks, specifically DeepLab v3+, fully convolutional network (FCN), and U-Net to qualitively analyze and identify the key components of cutting slope images in complex scenes and achieve rapid image-based slope detection. The elements of cutting slope images are divided into 7 categories. In order to determine the best algorithm for pixel level classification of cutting slope images, the networks are compared from three aspects: a) different neural networks, b) different feature extractors, and c) 2 different optimization algorithms. It is found that DeepLab v3+ with Resnet18 and Sgdm performs best, FCN 32s with Sgdm takes the second, and U-Net with Adam ranks third. This paper also analyzes the segmentation strategies of the three networks in terms of feature map visualization. Results show that the contour generated by DeepLab v3+ (combined with Resnet18 and Sgdm) is closest to the ground truth, while the resulting contour of U-Net (combined with Adam) is closest to the input images.

  • RESEARCH ARTICLE
    Abbas YAZDANI

    This paper uses the spectral stochastic finite element method (SSFEM) for analyzing reinforced concrete (RC) beam/slab problems. In doing so, it presents a new framework to study how the correlation length of a random field (RF) with uncertain parameters will affect modeling uncertainties and reliability evaluations. It considers: 1) different correlation lengths for uncertainty parameters, and 2) dead and live loads as well as the elasticity moduli of concrete and steel as a multi-dimensional RF in concrete structures. To show the SSFEM’s efficiency in the study of concrete structures and to evaluate the sensitivity of the correlation length effects in evaluating the reliability, two examples of RC beams and slabs have been investigated. According to the results, the RF correlation length is effective in modeling uncertainties and evaluating reliabilities; the longer the correlation length, the greater the dispersion range of the structure response and the higher the failure probability.

  • RESEARCH ARTICLE
    Yixian LI, Limin SUN, Wang ZHU, Wei ZHANG

    In structural health monitoring (SHM), the measurement is point-wise but structures are continuous. Thus, input estimation has become a hot research subject with which the full-field structural response can be calculated with a finite element model (FEM). This paper proposes a framework based on the dynamic stiffness theory, to estimate harmonic input, reconstruct responses, and to localize damages from seriously deficient measurements. To begin, Fourier transform converts the dynamic equilibrium equation to an equivalent static one in the frequency domain, which is under-determined since the dimension of measurement vector is far less than the FEM-node number. The principal component analysis has been adopted to “compress” the under-determined equation, and formed an over-determined equation to estimate the unknown input. Then, inverse Fourier transform converts the estimated input in the frequency domain to the time domain. Applying this to the FEM can reconstruct the target responses. If a structure is damaged, the estimated nodal force can localize the damage. To improve the damage-detection accuracy, a multi-measurement-based indicator has been proposed. Numerical simulations have validated that the proposed framework can capably estimate input and reconstruct multi-types of full-field responses, and the damage indicator can localize minor damages even with the existence of noise.

  • RESEARCH ARTICLE
    Rui ZHAO, Yongjian LIU, Lei JIANG, Yisheng FU, Yadong ZHAO, Xindong ZHAO

    It has been found that the fatigue life of tubular joints is not only determined by the hot spot stress, but also by the stress distribution through the tube thickness represented as the degree of bending (DoB). Consequently, the DoB value should be determined to improve the accuracy of fatigue assessment for both stress-life curve and fracture mechanics methods. Currently, no DoB parametric formula is available for concrete-filled rectangular hollow section (CFRHS) K-joints, despite their wide use in bridge engineering. Therefore, a robust finite element (FE) analysis was carried out to calculate the DoB of CFRHS K-joints under balanced-axial loading. The FE model was developed and verified against a test result to ensure accuracy. A comprehensive parametric study including 190 models, was conducted to establish the relationships between the DoBs and four specific variables. Based on the numerical results, design equations to predict DoBs for CFRHS K-joints were proposed through multiple regression analysis. A reduction of 37.17% was discovered in the DoB, resulting in a decrease of 66.85% in the fatigue life. Inclusively, the CFRHS K-joints with same hot spot stresses, may have completely different fatigue lives due to the different DoBs.

  • RESEARCH ARTICLE
    Pravin Kumar Venkat Rao PADALU, Yogendra SINGH

    The paper presents a seismic safety assessment of unreinforced masonry (URM) building using two approaches. The first approach uses the ‘Pier Analysis’ method, based on the concept of equivalent lateral stiffness, where in-plane and out-of-plane actions are considered independently. The second approach is developed with the program SAP2000, where the linear response is evaluated using continuum ‘finite element modelling’ (FEM). Both methods are compared to evaluate the safety of wall piers and the differences in the outcomes under combined gravitational and lateral seismic forces. The analysis results showed that few wall elements are unsafe in in-plane and out-of-plane tension. It is also observed that the pier analysis method is conservative compared to FEM, but can be used as a simplified and quick tool in design offices for safety assessment, with reasonable accuracy. To safeguard the URM wall piers under lateral loads, a retrofitting technique is adopted by providing vertical and horizontal belts called splints and bandages, respectively, using welded wire mesh (WWM) reinforcement. The study using the ‘Pier Analysis’ shows that the lateral load capacity of unsafe URM piers can be enhanced up to 3.67 times and made safe using the applied retrofitting technique. Further, the retrofitting design methodology and recommendations for application procedures to on-site URM buildings are discussed in detail.

  • RESEARCH ARTICLE
    Jinyoung YOON, Byoung Il CHOI, Jae Hong KIM

    The cement dispersion performance of a polycarboxylate (PCE)-based superplasticizer is highly related to their adsorption behaviors as a function of time. This study evaluated effects of PCEs on rheological properties of cementitious materials. First, characteristics of PCEs were characterized via permeation chromatography (GPC) and Fourier-transform infrared spectrometry (FT-IR). The adsorption behavior of single and blended PCEs on cementitious composites was identified using total organic carbon analyzer (TOC). Based on the measurement of PCE adsorption, the changes of rheological properties of cementitious materials as well as the number of dispersed cement particles were characterized using a rheometer and laser spectroscopy, respectively. The experimental results support the systematic mechanism of PCE adsorption, cement dispersion, and the decrease in viscosity of cementitious materials.

  • RESEARCH ARTICLE
    Meltem SAPLIOGLU, Ayse UNAL, Melek BOCEK

    Pavement roughness (IRI—International Roughness Index values) influence the stability of traffic movements both on intercity roads and urban roads. This study is to determine the exact locations of critical pavement roughness values that affect traffic motion stability and comfort in city centre highway arteries. Roughness data with 10 m intervals were collected on a 3140 m divided road containing three consecutive signalized intersections in the city centre arterial. These data were analysed using the distance-dependent Mann-Kendall trend analysis method and checkerboard model. The sections where roughness is important were determined at a 95% confidence interval. The results will show where future pavement improvements should be prioritized for municipalities and road maintenance engineers and will form a basis for the urban road management system.

  • RESEARCH ARTICLE
    Pooya ZAKIAN, Hossein ASADI HAYEH

    The present study uses the finite element method for simulating the crustal deformation due to the dislocation of a segment of the North-Tehran fault located in the Karaj metropolis region. In this regard, a geological map of Karaj that includes the fault segment is utilized in order to create the geometry of finite element model. First, finite element analysis of homogeneous counterpart of the fault’s domain with two different sections was performed, and the results were compared to those of Okada’s analytical solutions. The fault was modeled with the existing heterogeneity of the domain having been considered. The influences of both uniform and non-uniform slip distributions were investigated. Furthermore, three levels of simplification for geometric creation of geological layers’ boundaries were defined in order to evaluate the effects of the geometric complexity of the geological layering on the displacement responses obtained with the finite element simulations. In addition to the assessment of slip distribution, layering complexity and heterogeneity, the results demonstrate both the capability and usefulness of the proposed models in the dislocation analysis for the Karaj segment of North-Tehran fault.