Nonlinear static analysis of cable-stayed bridge structures

During the development stage of a liquid rocket engine structural analyses are needed for increasing structural reliability and identify necessary design changes. These analyses need enormous efforts for detail modeling and cause large computational cost. With increasing computational power, the modeling can be more detailed than in the past. In this study, non-linear static structural and free vibration analyses taking into account the static loading as preloading are performed for a 750 kN class liquid rocket engine system. The finite element (FE) structural analyses are performed using the general purpose commercial code, Abaqus 2016. The effects of the static loadings on stress distributions and the free vibration results are analyzed. Additionally a simple kinematic model using rigid body elements is made up to investigate the elasticity effects on the rotation angles due to engine gimbaling. The strains measured from a ground firing test are converted to equivalent stresses to be compared with the FE analysis results. And a certain leakage problem solved using the FE analysis results is also presented.

Nonlinear structural analysis, which can account for geometrical or material nonlinearities beyond the scope of linear methods, typically incurs high computational costs. Recent advances have shown that quantum computers can accelerate various numerical simulations. Although quantum acceleration of linear structural analysis via the Quantum Linear System Algorithm (QLSA) has been studied, its application to nonlinear structural analysis remains unexplored. Here, we introduce our proposed quantum algorithm for accelerating nonlinear structural analysis, summarizing its key features and performance results from our recent study.

Static and dynamic structural analyses of a turbine bladed-disk for a liquid rocket turbopump are performed to investigate the safety level of strength and vibration at design point. During operation, turbopump is exposed to various external loads. Therefore, the effects of them should be carefully considered and properly modeled. First, due to the high rotational speed of the turbopump, effects of centrifugal forces are considered in the structural analysis. Thermal load caused by severe temperature differences is also considered. A three dimensional finite element method (FEM) is used for linear and nonlinear structural analyses with modified Newton-Raphson iteration method. After the nonlinear solution is obtained from the structural analysis, dynamic characteristics are obtained as a function of rotational speed from the linearized eigenvalue analysis at an equilibrium position. From the analysis results, characteristics of stress distribution and vibration were thoroughly examined and investigated.

Static and dynamic physically non-linear analysis of concrete structures using a hybrid mixed finite element model

Current codes and guidelines provide different methods to perform nonlinear static analysis of structures that require some non-intuitive assumptions in their application. In the present paper an energy-based method for nonlinear static analysis that allows to overcome these assumptions is proposed. In the method the capacity and the demand are both expressed in terms of energy. An energy capacity curve is computed considering that at each step the work of the lateral forces is equal to the structure internal work. The demand is represented in terms of an energy quantity, defined pseudo-energy, that is computed from both the maximum response displacement and the maximum response force. Constant ductility pseudo-energy spectra are introduced as energy demand design spectra, alternative to the input energy demand spectra. The definition of the performance point does not require iterative procedures for equating the internal dissipated energy to the demand energy. For the direct evaluation of the performance point two different operative procedures are proposed. The proposed method is evaluated comparing the earthquake-induced deformations of single degree-of-freedom systems resulting from the application of the presented nonlinear static analysis procedures with those obtained from the time-history analysis and from the application of the EC8 nonlinear static analysis procedure. The method is also applied in the case of a RC plane frame representing the inner frame of a six story building. The results obtained with the proposed method are in good agreement with those computed using nonlinear dynamic analyses, moreover they are characterized by a better accuracy with respect to the results obtained with the method provided by EC8.

In this work, we describe the formulation and implementation for stress-based hybrid elements for conducting non-linear analysis of elastic structures. The motivation behind developing these elements is that they should be as simple to use as standard displacement-based isoparametric brick elements, but at the same time, be relatively immune to the shortcoming that these elements suffer from, namely, ‘locking’ problems which occur when they are used to model plate/shell geometries, almost incompressible materials or when the elements are distorted, and so on. The formulation is based on a two-field mixed variational principle. Numerical examples are presented to demonstrate the excellent performance of the proposed elements on a variety of challenging problems involving very large deformations, buckling, mesh distortions, almost incompressible materials, etc. Copyright © 2006 John Wiley & Sons, Ltd.

Piezoelectric composite laminates are a powerful material system that offers vast options to improve structural behavior. Successful design of piezoelectric adaptive structures and testing of control laws call for highly accurate, reliable and numerically efficient numerical tools. This paper puts focus onto linear and geometrically nonlinear static and dynamic analysis of smart structures made of such a material system. For this purpose, highly efficient linear 3-node and 4-node finite shell elements are proposed. Both elements employ the Mindlin-Reissner kinematics. The shear locking effect is treated by the discrete shear gap (DSG) technique with the 3-node element and by the assumed natural strain (ANS) approach with the 4-node element. Geometrically nonlinear effects are considered using the co-rotational approach. Static and dynamic examples involving actuator and sensor function of piezoelectric layers are considered.

A formulation of the nonlinear FEM truss element that takes into account both the geometric nonlinearity and material nonlinearity of the structure is derived. The associated iterative algorithm for the application is described. Based on two inelastic material models (isotropic hardening and dynamic hardening), three space truss structures are subjected to static and to dynamic loads in order to illustrate the application of nonlinear FEM. The nonlinear FEM described can accurately trace the complex structural behavior of space truss structures, including snap-through, and buckling. The FEM results match well with the theoretical results.

The application of a reinforced plaster mortar for seismic strengthening of masonry structures

With the improvement of force mode, the development of material characteristics and technologies, the Cable-stayed Bridge structures are used more and more widely. In 1975, Yunyang Bridge, the first experimental Cable-stayed Bridge of China, was completed. In the following decades, China has greatly increased the span of bridges and the height of towers. During construction, the materials used to build bridge structures are more diverse and safer. In 2017, the Hong Kong-Zhuhai-Macao Bridge, representing the most advanced bridge-building technology in China at the time, was born. In this paper, the history of ancient Cable-stayed Bridges is firstly introduced. Then, several Cable-stayed Bridges which have great influence are researched, respectively. Finally, this paper compares Yunyang Bridge and Hong Kong-Zhuhai-Macao Bridge in-depth from three aspects: comparison of the construction scales, comparison of the construction materials and comparison of the cable technologies. The results show the progress of bridge industry in the past 42 years of China.

Identification of Modal Combinations for Nonlinear Static Analysis of Building Structures

This paper presents a multi-dimensional variable-kinematics finite element model for nonlinear static analyses of structures with complex geometries. The approach incorporates higher-order beam models and classical solid finite elements in a unified framework, enabling refined modeling of complex geometries. The finite element procedure proposed follows the Carrera Unified Formulation (CUF) and uses a pure displacement-based methodology. The governing equations are derived within the classical continuum mechanics framework, and weak-form equilibrium equations are established using the Principle of Virtual Displacements (PVD). Within the CUF framework, higher-order beam and hexahedral solid models are defined in a unified manner, and the governing equations are written in terms of invariants of mathematical models used and the theory of structures approximation. A coupling technique is used between the beam and solid elements at the nodal level using superposition. The capabilities of fully nonlinear variable-kinematics models are investigated for the static analysis of various rectangular and curved structures. The numerical results are compared with solutions obtained using commercial software. Finally, the proposed methodology is applied to analyze more complex geometries in engineering applications. The results show the capabilities of variable-kinematics models in terms of both accuracy and computational efficiency for the computation of highly nonlinear deformed states and localized phenomena, such as stress concentrations and buckling.

A distributed inelasticity cyclic model of reinforced concrete (RC) columns is developed, using as a building block the tangent flexibility matrix of a section, which relates the three nondimensional normal stress resultants to the three corresponding section deformations. It is given in a companion paper in terms of the amount and distribution of the column longitudinal and transverse reinforcement. The tangent flexibility matrix of the cross section is integrated numerically along the element length to give the tangent flexibility (and stiffness, by inversion) matrix of slender reinforced concrete columns, in which flexure dominates the cyclic inelastic behavior. The model is implemented into a finite element program for the nonlinear static or dynamic analysis of structures in three dimensions. The program is applied to predict the results of cyclic uniaxial or biaxial tests, as well as the dynamic response of an actual reinforced concrete building to the three components of the Kalamata 1986 earthquake. The model predictions are in good agreement with the test results and with the damage inflicted to the building by the earthquake.

The article presents a finite element based study of linear and geometrically non-linear progressive failure analysis of thin walled composite aerospace structures subjected to combined in-plane and out-of-plane loading which are typically encountered in thin walled aerospace structures. Different ply and constituent based failure criteria and material property degradation schemes have been coded into a PCL code in Nastran. As case studies, progressive failure analyses of sample composite laminates with cut-outs under combined loading are executed to study the effect of geometric non-linearity on the first ply failure and progression of failure. Different ply and constituent based failure criteria and different material property degradation schemes are also compared in terms of predicting the first ply failure and failure progression. For mode independent failure criteria, a method is proposed for the determination of separate degradation factors for fiber and matrix failures which are assumed to occur simultaneously. The results of the present study, show that under combined out-of-plane and in-plane loading, depending on the load case linear analysis can significantly underestimate or overestimate the failure progression compared to geometrically non-linear analysis even at low levels of out-of-plane loading.

Comparison of ACI-318 and TS-500 codes for nonlinear seismic analysis of RC structures using force-based fiber element approach