Abstract
With the aim to provide better predication about fracture behavior, a numerical simulating strategy based on the rigid
spring model is proposed for reinforced concrete (RC) structures in this study. According to the proposed strategy, concrete is partitioned into a series of irregular rigid blocks based on the Voronoi diagram, which are connected by interface springs. Steel bars are simulated by bar elements, and the bond slip element is defined at bar element nodes to describe the interaction between reinforcement and concrete. A concrete damage evolution model based on the separation criterion is adopted to describe the weakening process of interface spring between adjacent blocks, while a nonlinear bond slip model is introduced to simulate the synergy behaviour of reinforced steel bars and concrete. In the damage evolution model of concrete, the influence of compressive stress perpendicular to the interface on the shear strength is considered. To check the effectiveness and applicability of the proposed modelling, experimental and numerical studies about a simply-supported RC beam and the two-notched concrete plates in Nooru-Mohamed's experiment are conducted, and the grid sensitivity are investigated.
Key Words
cracks; fracture behavior; reinforced concrete; rigid body spring model; Voronoi diagram
Address
Binbin Gong: College of Civil Engineering, Hunan City University, Yiyang 413000, China; Hunan Engineering Research Center of Structural Safety and Disaster Prevention for Urban Underground Infrastructure, Yiyang 413000, China
Hao Li: CCCC Third Highway Engineering Co., Ltd, Beijing 100102, China
Abstract
Numerical modeling using the finite element method (FEM) offers crucial insights into the mechanical behavior of
prostheses, including stress and strain distribution, load transfer, and stress intensity factors. Analyzing cracking in PMMA surgical cement (polymethylmethacrylate) for total hip prostheses (THP) is essential for understanding the loosening phenomenon, as the rupture of orthopedic cement is a primary cause. By understanding various failure mechanisms, significant advancements in cemented total prostheses can be achieved. This study performed a numerical analysis using a 3D FEM model to evaluate stress levels in different THP models, aiming to model damage in the orthopedic cement used in total hip arthroplasty. Utilizing ABAQUS software, FEM, and XFEM, the damage in three types of THPs-Charnley (CMK3), Osteal (BM3), and THOMPSON was modeled under stumbling loading conditions. XFEM allowed for the consideration of crack propagation between the cement and bone, while the GEARING criterion employed a user-defined field subroutine to model damage parameters. The study's findings can contribute to improving implant fixation techniques and preventing postoperative complications in orthopedic surgery.
Key Words
cement; damage; finite element method; GEARING; total hip prosthesis; X-FEM
Address
Cherfi Mohamed, Ait Kaci Djafar, Sahli Abderahmen: Department of Mechanical Engineering, University of Sidi Bel Abbes, BP 89, City Ben Mhidi, Sidi Bel Abbes 22000, Algeria; Department of Mechanical Engineering, Laboratory Mechanics Physics of Materials (LMPM), University of Sidi Bel Abbes, Algeria
Zagane Mohammed El Sallah, Moulgada Abdelmadjid: Department of Mechanical Engineering, University of Ibn Khaldoun, Tiaret, BP 78 Zaaroura Street, Tiaret 14000, Algeria; Department of Mechanical Engineering, Laboratory Mechanics Physics of Materials (LMPM), University of Sidi Bel Abbes, Algeria
Benouis Ali: Department of Mechanical Engineering, Laboratory Mechanics Physics of Materials (LMPM), University of Sidi Bel Abbes, Algeria; Faculty of Technology, University of Moulay Tahar, Saida BP138 Saida 20000, Algeria
Zahi Rachid: Department of Mechanical Engineering, University of Relizane.BP48000, Algeria
Abstract
The primary aim of this study is to introduce an innovative configuration for stirrup hooks in reinforced concrete beams and analyze the impact of factors such as stirrup spacing, placement, and hook lengths on the structural performance of reinforced concrete beam elements. A total of 18 specimens were produced and subjected to reversed cyclic loading, with two specimens serving as reference specimens and the remaining 16 specimens utilizing a specifically developed stirrup hook configuration. The experiment used reinforced concrete beams scaled down to half their original size. These beams were built with a shear span-to-depth ratio of 3 (a/d=3). The experimental samples were divided into two distinct groups. The first group comprises nine test specimens that consider the contribution of concrete to shear strength, while the second group consists of
nine test specimens that do not consider this contribution. The preparation of reference beam specimens for both groups involved the utilization of standard hooks. The stirrup hooks in the test specimens are configured with a 90-degree angle positioned at the midpoint of the bottom section of the beam. The criteria considered in this study included the distance between hooks, hook angle, stirrup spacing, hook orientation, and hook length. In the experimental group examining the contribution of concrete on shear strength, it was noted that the stirrup hooks of both the R1 reference specimen and specific test specimens displayed indications of opening. However, when the contribution of concrete on shear strength was not considered, it was observed that none of the stirrup hooks proposed in the R0 reference specimen and test specimens showed any indications of opening. Neglecting the contribution of concrete in the assessment of shear strength yielded more favorable outcomes regarding structural robustness. The study found that the strength values obtained using the suggested alternative stirrup hook were similar to those of the reference specimens. Furthermore, all the test specimens successfully achieved the desired strengths.
Abstract
The purpose of this study is to represent a useful alternative for the preliminary seismic vulnerability assessment of existing reinforced concrete buildings by introducing a statistical approach employing the binary logistic regression technique. Two different predictive statistical models, namely full and reduced models, were generated utilizing building characteristics obtained from the damage database compiled after 1999 Düzce earthquake. Among the inspected building parameters, number of stories, overhang ratio, priority index, soft story index, normalized redundancy ratio and normalized lateral stiffness index
were specifically selected as the predictor variables for vulnerability classification. As a result, normalized redundancy ratio and soft story index were identified as the most significant predictors affecting seismic vulnerability in terms of life safety performance level. In conclusion, it is revealed that both models are capable of classifying the set of buildings being severely damaged or collapsed with a balanced accuracy of 73%, hence, both are able to filter out high-priority buildings for life safety performance assessment. Thus, in this study, having the same high accuracy as the full model, the reduced model using fewer
predictors is proposed as a simple and viable classifier for determining life safety levels of reinforced concrete buildings in the preliminary seismic risk assessment.
Key Words
binary logistic regression; reinforced concrete buildings; seismic assessment; seismic vulnerability; statistical
model
Address
Işil Sanri Karapinar, Ayşe E. Özsoy Özbay and Emin Çiftçi: Department of Civil Engineering, Maltepe University, Marmara Eğitim Köyü, 34857, İstanbul, Turkey
Abstract
This paper predicts the combined resonance behavior of the truncated conical shells (TCSs) under transverse and parametric coupled excitation. The motion governing equation is formulated in the framework of high-order shear deformation theory, von Kármán theory and Hamilton principle. The displacements and boundary conditions are characterized by a set of displacement shape functions with double Fourier series. Subsequently, the method of varying amplitude (MVA) is utilized to derive the approximate analytical solution of system response of TCSs. A comparative analysis is conducted to verify the accuracy of the current computational method. Additionally, the interaction mechanism of combined resonance, parametric resonance and primary resonance is examined. And the effect of damping coefficient, the external excitation, initial phase, axial motion speed, temperature variation, humidity variation, material properties and semi-vortex angle on the vibration mechanism are analyzed.
Key Words
functionally graded material; hygro-thermal environment; the method of varying amplitude; truncated conical shell
Address
Zhong-Shi Ma and Gui-Lin She: College of Mechanical and Vehicle Engineering, Chongqing University, Chongqing 400044, China
Abstract
Plastic buckling of tubular columns has been attributed to rotational instability of plastic hinges. The present study
aimed to characterize the plastic hinges for two different grades of strain-hardening, examined in mild-steel (MS) and stainlesssteel (SS) tubes with un-strengthened and strengthened conditions. At the primary stage, the formerly tested experimental specimens were simulated using full-scale FE models considering nonlinear response of the materials, then to estimate the characteristics of the plastic hinges, a meso model was developed from the critical region of the tubes and the moment-rotation diagrams were depicted under pure bending conditions. By comparison of the relative rotation diagram obtained by the full-scale models with the critical rotation under pure bending, the length and critical rotation of the plastic hinges under eccentric axial load were estimated. The stress and displacement diagrams indicated the mechanism of higher energy absorption in the strengthened tubes, compared to unstrengthened specimens, due to establishment of stable wrinkles along the tubes. The meso model showed that by increasing the critical rotation in the strengthened MS tube equal to 1450%, the energy absorption of the tube has been enhanced to 2100%, prior to collapse.
Address
Ali Reza Nazari: Department of Civil Engineering, Technical and Vocational University, Tehran, Iran
Farid Taheri: Department of Mechanical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada
Abstract
An expansive soil in 4970 special railway line in Dangyang City, China, has encountered a series of landslides due to the expansion characteristics of expansive soil over the past 50 years. Thereafter, a sheet-pile retaining structure was adopted to fortify the expansive soil slope after a comprehensive discussion. In order to evaluate the efficacy of engineering measure of sheet-pile retaining structure, the field test was carried out to investigate the lateral pressure and pile bending moment subjected to construction and service conditions, and the local daily rainfall was also recorded. It took more than 500 days to carry out the field investigation, and the general change laws of lateral pressure and pile bending moment versus local daily rainfall were obtained. The results show that the effect of rainfall on the moisture content of backfill behind the wall decreases with depth. The performance of sheet-pile retaining structure is sensitive to the intensity of rainfall. The arching effect is reduced significantly by employing a series of sheet behind piles. The lateral pressure behind the sheet exhibits a single-peak distribution. The turning point of the horizontal swelling pressure distribution is correlated with the self-weight pressure distribution of soil and the variation of soil moisture content. The measured pile bending moment is approximately 44% of the ultimate pile capacity, which indicates that the sheet-pile retaining structure is in a stable service condition with enough safety reserve.
Key Words
EPS; expansive soil slope; lateral pressure; sheet-pile wall
Address
Zhen Zhang, Yu-Liang Lin, Guo-Lin Yang: School of Civil Engineering, Central South University, Changsha, 410075, China
Hong-Ri Zhang: Guangxi Transportation Science & Technology Group Co. Ltd., Nanning, 530029, China
Bin He: Yueyang Planning, Survey and Design Institute Co. Ltd., Yueyang, 414004, China
Yong-Fu Xu: Department of Civil Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
Abstract
This paper deals with the dynamic buckling behavior of truncated conical shells composed of carbon nanotube composites, an important area of study in view of their very wide engineering applications in aerospace industries. In this regard, the effective material properties of the nanocomposite have been computed using the Mori-Tanaka model, which has already been established for such analyses. The motion equations ruling the structure's behavior are derived using first order shear deformation theory, Hamilton's principle, and energy method. This will provide adequate background information on its dynamic response. In an effort to probe the dynamic instability region of the structure, differential quadrature method combined with Bolotin's method will be adopted to tackle the resulting motion equations, which enables efficient and accurate analysis. This work considers the effect of various parameters in the geometrical parameters and the volume fraction of CNTs on the structure's DIR. Specifically, it became clear that increasing the volume fraction of CNTs shifted the frequency range of the DIR to higher values, indicating the significant role of nanocomposite composition regarding structure stability.
Address
S.M.R. Allahyari: Department of Mechanical Engineering, Dariun Branch, Islamic Azad University, Dariun, Iran
M. Shokravi: Energy Institute of Higher Education, Mehrab High School, Saveh, Iran
T.T. Murmy: Faculty of Mechanical Engineering, University of Hongkong, Hong Kong
