Abstract
This work presents a model-order reduction framework for three-dimensional finite element-based rotating systems parameterized by rotational speed. To address potential vibration problems in linearized rotor dynamics, both co-rotating and fixed-reference frames are considered to establish governing equations in the time, frequency, and modal domains. The proposed approach represents solutions to these equations as a low-rank approximation. Based on this approximation, a nonlinear equation is formulated and a unified algorithmic framework is developed with specific derivations tailored for each analysis domain. Basis vectors spanning the low-dimensional subspace are progressively enriched on-the-fly without solving the full-order model. Solutions at evaluation points are obtained using the reduced-order model based on Galerkin projection. The performance of the proposed approach is examined through numerical examples, demonstrating its ability to provide accurate solutions across various analysis domains. Additionally, by replacing the direct computation of full-order models at evaluation points with the acquisition of basis vectors and solving reduced-order models, computational efficiency is significantly enhanced.
Key Words
3D finite element rotor; low-rank approximation; parameterized model-order reduction; reduced-order modeling; rotor dynamics
Address
Gil-Yong Lee: SMART Technology Development Division, Korea Atomic Energy Research Institute, 111, Daedeok-Daero 989 beon-gil, Yuseong-gu, Daejeon, 34141, Republic of Korea
Dae-Guen Lim: Department of Mechanical Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon ,34141, Republic of Korea
Kwanghyun Ahn: SMART Technology Development Division, Korea Atomic Energy Research Institute, 111, Daedeok-Daero 989 beon-gil, Yuseong-gu, Daejeon, 34141, Republic of Korea
Abstract
China's high-speed railway (HSR) has entered the operation and maintenance stage. Exploring the damage mechanism of HSR is of great significance in determining its post-earthquake functional usability. China Railway Track System III (CRTS III) Slab Ballastless Track (SBT) is a mainstream track system independently developed by China, but the damage mechanism and failure chain of the HSR CRTS III SBT simple-supported bridge (SSB) is still unclear. To explore the damage mechanism and failure chain of the HSR SSB under the action of different combinations of seismic directions, a test of CRTS III SBT was carried out to explore the constitutive relationship of the isolation layer. Then based on the test data, a non-linear finite element model (FEM) of CRTS III SBT SSB for HSR was built and validated. The vulnerable parts of the HSR SSB system under earthquake excitation were analyzed, and the damage distribution pattern, damage and failure sequences of vulnerable parts under four kinds of earthquake conditions were investigated. According to the research, the most vulnerable components of the HSR SSB system were the bearings, piers, and fasteners under earthquake, The fixed bearing experienced earlier failure than the sliding bearing, The pier's damage under transverse seismic was far smaller than that under longitudinal seismic, The failure chain of the HSR SSB system were different under transverse and longitudinal earthquake, During the bridge design phase, it is suggested to strengthen the middle span bearing and pier, and to strengthen the fasteners at the beam joints without affecting the track smoothness.
Key Words
CRTS III slab ballastless track; high-speed railway; seismic-induced damage distribution mode; seismicinduced damage sequence; seismic-induced failure sequence
Address
Lili Liu: Department of Civil Engineering, Hefei University of Technology, Hefei, 230009, P.R. China; School of Civil Engineering, Central South University, Changsha, 410075, P.R. China; National Engineering Research Center of High-speed Railway Construction Technology, Changsha, 410075, P.R. China
Lizhong Jiang: School of Civil Engineering, Central South University, Changsha, 410075, P.R. China; National Engineering Research Center of High-speed Railway Construction Technology, Changsha, 410075, P.R. China
Wangbao Zhou: School of Civil Engineering, Central South University, Changsha, 410075, P.R. China; National Engineering Research Center of High-speed Railway Construction Technology, Changsha, 410075, P.R. China
Xiang Liu: School of Civil Engineering, Fujian University of Technology, Fuzhou, 350118, P.R. China
Jian Zhong: Department of Civil Engineering, Hefei University of Technology, Hefei, 230009, P.R. China
Abstract
The growing demand for innovation and carbon dioxide reduction in the civil construction sector has accelerated
interest in eco-friendly and sustainable alternatives to traditional binding materials, such as geopolymer concrete. This study investigates the enhancement of Water-Cooled Slag-Metakaolin (WCS-MK) geopolymer composites with polypropylene (PP) fibers to address traditional geopolymer drawbacks, such as high shrinkage and brittleness. Using a mixture of 10% NaOH and 10% Na2SiO3 as an alkaline activator, PP fibers were added incrementally up to 2% by weight. The results demonstrated a 21% increase in compressive strength with the optimal addition of 1% PP fiber, alongside a significant reduction in drying shrinkage. The incorporation of PP fibers not only improved the ductility of the composites but also facilitated effective void management, as confirmed by SEM analysis. XRD analysis further revealed enhanced mineralogical phases, contributing to improved morphological properties. This study highlights the potential of fiber-reinforced geopolymer composites as a sustainable solution with improved mechanical and durability characteristics, offering promising applications in eco-friendly construction and repair work.
Key Words
composites; metakaolin; polypropylene; shrinkage; slag
Address
Hisham Mostafa Khater and Sara Abd ElMoied Sayed: Institute of Raw and Building Materials, Housing and Building National Research Center, 87 ElTahrir St., Giza, Egypt
Abstract
The study aimed at developing an adaptive Linear Quadratic Gaussian Design with artificial intelligence based
Particle Swarm Optimization (LQG-PSO) mechanism. The purpose of the proposed mechanism is to reduce the dynamic vibration of a space framed structure subjected to seismic loads. The addressed damper force has been measured and provided
using a developed MR damper ARX model. A framed structure has been adopted as a benchmark study model to illustrate the performance of the proposed algorithm. Various time histories data has been used as input to the framed structure. For the benchmark frame problem, the proposed method has been found to be more significant in reducing the floor vibration responses in comparison with the conventional Linear Quadratic Gaussian (LQG) design method and passive control method with tuned liquid column damper. The proposed artificial intelligence based control method with the designated MR damper model is effective in calculating the optimized control force required from MR damper. Therefore, it minimizes the need of dampers capable of attaining higher damper force and the number of dampers. In consequence, it reduces the structural vibration reduction and the cost of maintenance during earthquakes.
Key Words
artificial intelligence; auto-regressive exogenous input model; Linear Quadratic Gaussian Design; Magnetorheological damper; particle swarm optimization; semi-active control
Address
Payel Chaudhuri: Department of Civil Engineering, Vignan
Abstract
Thin-walled structures are commonly seen in many engineering fields, and their mechanical properties attract increasing interest from researchers. Thin-walled tubes are apt to flatten, especially crushed by a transverse load, which greatly decreases their global load-carry capacity. Investigations have shown that it is favorable to reinforce the thin-walled tubes to enhance their load resistance at the cost of small increase of structural mass. For this purpose, a novel reinforcing method called triangular stiffening to empty circular tubes is proposed, and the influence on the three-point bending crashworthiness is studied using finite element modelling with the aid of ABAQUS/Explicit code. The finite element model for the case of empty tube is verified by experimental results. According to the two popular crashworthiness indicators including SEA (Specific Energy Absorption) and CLE (Crash Load Efficiency), the tubes reinforced by the triangular stiffeners have an advantage over the two reinforcing methods suggested by previous literature. Deformation mechanism of triangular stiffening is demonstrated in terms
of the comparison with corresponding empty tubes. The impact of three parameters including thickness, length and intersecting angles of stiffeners on the bending crashworthiness is analyzed and discussed in detail.
Key Words
bending crashworthiness; finite element analysis; reinforcing method; thin-walled circular tubes; triangular stiffening
Address
Zhong-you Xie: School of Architectural Engineering, Tongling University, Tongling, 244061, Anhui, China
Ze-yi Wang: School of Automotive Engineering, Changzhou Institute of Technology, Changzhou, 213032, Jiangsu, China
Li-min Guo: School of Sciences, Changzhou Institute of Technology, Changzhou, 213032, Jiangsu, China
Cheng Li, Jian-wen Cai: School of Automotive Engineering, Changzhou Institute of Technology, Changzhou, 213032, Jiangsu, China
Abstract
Steel-concrete composite (SCC) girders are gaining popularity in the construction industry due to their ease of rapid construction and higher span-to-depth ratios. Simply-supported SCC girders are widely used in flyover and railway over bridges to avoid traffic disturbance during construction. The present paper considers an SCC girder consisting of a concrete slab and steel girder integrated together to resist stresses through composite action. The cross-section of SCC girders is slender, hence they would be susceptible to serviceability criteria like deflection and cracking. From the comprehensive literature survey, it has been deduced that the thermal stresses due to the temperature gradient effect play an important role in inducing concrete cracking and a further increase in deflection. In the present study, the explicit equations are derived to predict the thermal stress distribution across the cross-section. Further, the equations are also derived for the mid-span deflection considering concrete cracking in addition to temperature gradient effects. In order to validate the results obtained from the proposed equations, the finite element (FE) models are developed. The results obtained from the equations and FE models are compared and found within an acceptable limit for everyday design purposes. The explicit equations significantly reduce computational time compared to the finite element analysis (FEA).
Key Words
cracking; deflection; steel-concrete composite girder; temperature gradient; tension stiffening
Address
M.A. Modi, K.A. Patel: Department of Civil Engineering, Sardar Vallabhbhai National Institute of Technology (SV-NIT), Ichchhanath, Dumas Road, Surat, 395007, India
Sandeep Chaudhary: Department of Civil Engineering, Indian Institute of Technology Indore (IIT Indore), Simrol, Indore, 453552, India
