Stresses In Structural Members Research Articles

Statics of integrated origami and tensegrity systems

This study presents an explicit form of the static equilibrium equations of integrated origami and tensegrity systems. The analytical approach allows one to model and analyze the isolated origami and tensegrity paradigms as a whole system. The tensegrity and origami members are described by the nodal coordinates and hinge angels between the origami panels. The nonlinear static equations of the integrated system are derived by the Lagrangian method. By Taylor’s expansion theory, we also presented its linearized form. The developed approach is capable of conducting the following comprehensive statics studies for any integrated origami and tensegrity systems: (1) Performing loading analysis, where bars and strings can have elastic or plastic deformations. (2) Conducting infinitesimal and large deformation analysis, which is helpful in understanding the stress in structural members and actuation strategies. (3) Dealing with various kinds of boundary conditions, for example, fixing or applying static loads at any nodes in any direction (i.e., gravitational force, some specified forces, or moments). (4) Conducting stiffness analysis, including eigenvalues and their modes. Three examples, a Miura origami unit, an integrated tensegrity origami shelter, and a cable-driven Kresling structure, are carefully selected and studied. This study provides a deep insight into structures, materials, as well as performances. The integration idea also promotes our ability to design and build deployable structures at large.

Nonlocal dynamic temperature stress simulation

The development of technologies for obtaining consolidated structural materials has increased interest in modelling materials with a heterogeneous structure. For models of such materials, an important factor is the relationship between the characteristics of the micro-(nano- ) level and the laws of continuum mechanics at the macro level. The widespread use of modern structure-sensitive materials in extreme conditions is the reason for the urgency of the problem of developing methods of mathematical modelling that allow describing such materials. New nonlinear dynamic problems that arise in this case require a new approach to the study and prediction of the mechanical behavior of such materials under conditions of high-intensity external influences. The paper considers a nonlocal model of dynamic temperature stresses. The model is based on the methods of globalized continuum mechanics. The basic equations of the model are derived from conservation laws. The model of thermomechanical processes in a nonlocal medium includes integro-differential equations with various boundary conditions. Equations describe stress in structural members. Also, the paper proposes an algorithm based on the finite element method to solve the problem. The distributions of temperature stresses in the nonlocal layer of the material are obtained and the influence of the main parameters of nonlocality on the solution of the problem is analyzed.

Flexural bond behavior of reinforced recycled aggregate concrete

Abstract Replacing natural aggregate concrete with recycled aggregate concrete (RAC) can effectively solve aggregate shortage problems. However, application of recycled aggregate in engineering structures requires analysis of the interaction between steel bars and RAC. The bond behavior under flexure is similar to the actual state of stress in structural members. 15 beam specimens were designed and tested to investigate the RAC-reinforcement bond behavior and the constitutive relationship at the interface between them. Test parameters include water-binder ratio, recycled coarse aggregate (RCA) replacement percentage, recycled fine aggregate (RFA) replacement percentage, bar surface shape, and anchorage length of reinforcements. The influence of the above variables on the load to slip curves, bond strength, and the bond efficiency coefficient is discussed. Bond strength between reinforcements and concrete decreases with increasing RCA replacement percentage, however, the rate of decrease is reduced for specimens with low water-binder ratio. The addition of RFA significantly degrades bond behavior. The bond strength between deformed reinforcements and RAC is approximately 2 times of that of plain reinforcements. With increasing anchorage length, the interface bond behavior between the reinforcements and RAC decreases.

Ultrasonic Nondestructive Method for Stress Analysis of Structural Members and Near-Surface Layers of Materials: Focus on Ukrainian Research (Review)

The results obtained by Ukrainian researchers on the justification, development, and application of ultrasonic nondestructive methods (UNDMs) for evaluating stresses in structural members and near-surface layers of materials are briefly discussed. A distinguishing feature of Ukrainian methods is that they are capable of determining triaxial (including biaxial and uniaxial as partial cases) stresses, unlike non-Ukrainian methods applicable only to uniaxial stresses. The UNDMs are based on the laws of wave propagation in solids with initial (residual) stresses, including the laws of Rayleigh wave propagation. The results discussed were obtained in the National Academy of Sciences of Ukraine (S. P. Timoshenko Institute of Mechanics and E. O. Paton Institute of Electric Welding)

Ultrasonic nondestructive methods of stress analysis in materials and structural members (review)

Results of the justification, development, and application of nondestructive ultrasonic methods of stress analysis are briefly outlined (summarized). These are the results of cooperative research by the S. P. Timoshenko Institute of Mechanics and the E. O. Paton Institute of Electric Welding. The nondestructive ultrasonic methods are intended to determine triaxial (including biaxial and uniaxial) stresses in structural members and biaxial (including uniaxial) stresses in near-surface layers of materials

Evaluation on Environmental Corrosion Damage of Steel Domes

The evaluation on environmental corrosion damage of steel domes is carried out in this study through an integration of knowledge in material science and structural analysis. The refined exponential model for estimating corrosion of steel materials is presented based on long-term experimental data available. The formula for relating structural natural frequency sensitivity to structural member thickness is then derived to assess the sensitivity of natural frequency to variation of member thickness due to corrosion. The nonlinear static analysis is conducted to evaluate effects of atmospheric corrosion on the stress of structural members and the safety of steel space structures. A real steel dome built in China is taken as the case study to examine the feasibility of the proposed approach and to assess the potential corrosion damage to the structure..

Finite element prediction of interfacial stresses in structural members bonded with a thin plate

The strength or stiffness of a reinforced concrete (RC), metallic or timber member can be increased by bonding a thin FRP or steel plate to its external surface. In such plated members, debonding of the thin plate from the original member is often the controlling failure mode, and such debonding depends strongly on the interfacial stresses in the adhesive layer between the member and the plate. This paper is concerned with the prediction of these interfacial stresses using the finite element method. The paper is primarily focused on simply-supported straight plated beams subjected to a uniformly-distributed load as a widely studied benchmark case. Five different finite element modeling approaches based on different assumptions for the deformations of the three components of such a plated beam (beam, adhesive layer and plate) are described. The predictions of the five models are then compared with each other and with analytical solutions of different levels of sophistication. These comparisons illustrate clearly how each assumption affects the predicted interfacial stresses and identify the beam–spring–beam (B–S–B) model as a relatively simple yet sufficiently accurate model for practical use in predicting interfacial stresses and debonding failure in more complex structural members bonded with a thin plate. To illustrate the versatility and power of the B–S–B type model, interfacial stresses in two more complicated structures (a plated flat panel and a plated curved panel) obtained from the same type of model are presented and discussed. These results provide useful insight into the risk of debonding in such plated panels.

Strength Behavior of Cemented Marine Clay Subjected to Storm Type Loading

Cyclic loading on offshore structures leads to an increase in long term deformations. These deformations will cause additional stresses in structural members. Overloading of offshore structures may have serious consequences and they must be designed to accommodate the increased deformations. During a storm, there is a surge in the mean sea level causing an increase in stress and they are believed to represent critical conditions for offshore foundations. This program encompasses an experimental investigation for establishing the behavior of soil subjected to storm type varied cyclic loading conditions on Indian East coast marine clay samples. In field situations where cyclic loading is imposed on the soil, it can be considered a stress controlled phenomenon. If the effects of cyclic loading on any soil have to evaluated, it is considered more appropriate if the cyclic load test results are compared with reference static strength results obtained from stress controlled tests. To meet these requirements, a series of triaxial shear tests are conducted by adopting different load durations at each load increment. In order to estimate the effect brought in by storm type cyclic loading, it becomes necessary to conduct reference standard tests under uniform cyclic loading at various cyclic stress ratios (CSR) on identical soil specimens and these stress levels are chosen in such a way that there is no failure taking place during testing. This paper presents the behavior of marine clay subjected to uniform and storm type of varied cyclic loading. The effects of this cyclic loading are brought through the comparisons of the results obtained from testing under both strain and stress controlled monotonic loading.

Evaluation of atmospheric corrosion damage to steel space structures in coastal areas

Steel space structures in coastal areas, often exposed in the open air, are inevitably subjected to atmospheric corrosion. This paper presents a framework for evaluation of potential damage due to atmospheric corrosion to steel space structures in coastal areas through an integration of knowledge in material science and structural analysis. An empirical model for estimating corrosion of steel material is first presented based on long-term experimental data available. Equations relating structural natural frequency sensitivity to structural member thickness are then derived in consideration of both inner and outer surface corrosions of the structural member. The nonlinear static analysis is finally conducted to evaluate effects of atmospheric corrosion on the stress of structural members and the safety of steel space structures. By taking a real large steel space structure built in southern coastal area in China as example, the feasibility of the proposed approach is examined and the potential damage caused by atmospheric corrosion to the structure is assessed. The results demonstrate that the atmospheric corrosion does not obviously affect the natural frequencies of the structure but it does create stress redistribution and some of the structural members may have large stress changes.

신경망 기법을 이용한 1축 잔류응력장에서 구멍뚫기법의 구멍편심 오차 보정

The measurement of residual stresses by the hole-drilling method has been commonly used to evaluate residual stresses in structural members. In this method, eccentricity can usually occur between the hole center and rosette gage center. In this study, the error due to the hole eccentricity is compensated using the neural network. The neural network has trained training examples of normalized eccentricity. eccentric direction and direction of maximum stress at eccentric case using backpropagation learning process. The trained neural network could compensated the error of measured residual stress in experiments with hole eccentricity. The proposed neural network is very useful for compensation of the error due to hole eccentricity in hole-drilling method.<br/> <br/>

Prediction of error due to eccentricity of hole in hole-drilling method using neural network

The measurement of residual stresses by the hole-drilling method has been used to evaluate residual stresses in structural members. In this method, eccentricity can usually occur between the hole center and rosette gage center. In this study, we obtained the magnitude of the error due to eccentricity of a hole through the finite element analysis. To predict the magnitude of the error due to eccentricity of a hole in the biaxial residual stress field, it could be learned through the backpropagation neural network. The prediction results of the error using the trained neural network showed good agreement with FE analyzed results.

The wind-induced response of a full-scale portal framed building

An experimental study is presented of gust loading on the Silsoe Structures Building, a steel portal framed building instrumented with wind pressure sensors and strain gauges. It traces the spectral correlation between the free-stream wind pressure, external pressure, internal pressure and strain response for the building both with and without a dominant opening. It shows that there is a strong correspondence between the strain spectra and the internal pressure spectrum when a dominant opening is present and that the observed ‘heaving’ behaviour of the building under strong winds can be attributed to a Helmholtz oscillation effect. Gust durations are presented which facilitate predictions of peak stresses in structural members for the ‘static’ (no dominant opening) case. For the ‘dynamic’ (with dominant opening) case, dynamic magnification factors are presented which take account of the higher peak stresses generated in the structure.

The wind-induced response of a full-scale portal framed building

An experimental study is presented of gust loading on the Silsoe Structures Building, a steel portal framed building instrumented with wind pressure sensors and strain gauges. It traces the spectral correlation between the free-stream wind pressure, external pressure, internal pressure and strain response for the building both with and without a dominant opening. It shows that there is a strong correspondence between the strain spectra and the internal pressure spectrum when a dominant opening is present and that the observed ‘heaving’ behaviour of the building under strong winds can be attributed to a Helmholtz oscillation effect. Gust durations are presented which facilitate predictions of peak stresses in structural members for the ‘static’ (no dominant opening) case. For the ‘dynamic’ (with dominant opening) case, dynamic magnification factors are presented which take account of the higher peak stresses generated in the structure.

Consideration on identification method of residual stresses by boundary element method

Residual stresses in structural members occur due to machining, welding, and so on. For estimating the residual stresses, it is necessary to clarify numerous unknown qualities, the shape and dimension of the body force acting region. The boundary element method (BEM) has the advantage of transforming a region type problem into a boundary type one. So, as a method for estimating in a nondestructive manner some unknown internal residual stresses from the data of known boundary displacements and tractions, BEM is in principle of analysis, considered to be one of the most suitable methods. In the present paper, inverse analysis based on BEM was formulated and the method for identifying residual stresses in a plate and a cylindrical tube was developed. As an example of the method, an identification simulation of residual stresses which occurs owing to local heating and cooling was performed. As a result, it turned out that the evaluation parameter R 1 and R 2, the sum of body forces with opposite direction, are useful indices for the location search of the acting body force in inverse analysis. It is possible to identify the residual stressess in a plate with sufficient accuracy by thus using the obtained body force. Next, we extended the method to the identification problem of residual stresses in an axisymmetric body and demonstrated that it is possible to identify the magnitude of the residual stresses occurring at the welding region in a cylindrical tube.

A study of an identification method of residual stresses by inverse analysis with the boundary-element method

Residual stresses in structural members exist after machining, welding, and so on. The boundary-element method (BEM) has an advantage in transforming a region-type problem to a boundary-type one. As a method of estimating in a non-destructive manner some unknown internal residual stresses from the data of known boundary displacements and tractions, BEM is in principle one of the most suitable methods. In the present paper, inverse analysis based on BEM is formulated, and the method of identifying residual stresses in a plate and a cylindrical tube is developed. As a demonstration of usefulness of the method, an identification simulation of residual stresses that occur owing to local heating was performed. As a result, it was found that the evaluation parameters R 1 and R 2 , the sum of the body forces in opposite directions, were useful indices for determining the location of the body force acting in inverse analysis. We consider that the residual stresses in a plate can be identified with sufficient accuracy by using the body force obtained in this way. Next, we extended the method for the two-dimensional plate to that for the axisymmetric body and demonstrated that inverse analysis to search for the location where the body force was acting was conducted under the various conditions for the radius of the region where the forced acted, the inner radius of the cylindrical tube, and the wall thickness. It was found that the dimensionless parameter R m was a useful index within the defined position of the region where the body force was assumed to be acting.

Residual stresses in structural members in radial tensioning of the contour of holes

Residual stresses in structural members in radial tensioning of the contour of holes

Design with ceramics for fusion reactors

Ceramic materials used in the first wall and blanket regions of fusion reactors can provide very low radioactivity and high temperature systems with abundant raw material resources. Design problems arise in accommodating tensile stresses in structural members, however, with suitable designs, crack initiation, crack propagation and failures can be minimized. Several design concepts are discussed for inertial and magnetic confinement fusion reactors. A companion paper describes the analytical methods and results.

Residual-stress measurement by the sectioning method

The measurement of residual stresses by the sectioning method has been used for decades to measure residual stresses in structural members. This method has proven itself adequate, accurate and economical if proper care is taken in the preparation of the specimen and the procedure of measurement. However, a standard procedure to carry out such measurement does not exist in the published literature. In this paper, a detailed description is presented on the procedure of testing, preparation of specimen, the required tools and measuring devices and working conditions.

Space Frame Buckling

The large dome structure is being used more and more because of its structural efficiency, its low cost, and its beauty. The Houston Astrodome (see Fig. 1) is an illustration of future trends in large covered areas. Domes have been built using structural shapes, tubing, shells with stiffeners and composite materials. Buckling analysis is one of the most important considerations facing the designer of such a structure. If buckling failure occurs, it is often sudden and often results in complete collapse of the structure. The failure of the 300-ft diameter dome in Bucharest, Rumania1, is but one example of such a collapse. The purpose of this report is to show that the designer can calculate the general buckling load in the nonlinear stress-strain range and can take into account the important factors in buckling such as yield strength, edge conditions, construction and fabrication tolerances, and residual stresses in structural members.

Basic Column Strength

Summary of theoretical and experimental investigation of strength of centrally loaded columns as influenced by residual stresses and variations in yield-stress level; basic strength of structural steel columns containing residual stresses may be expressed in terms of tangent modulus; approximations for design use are suggested; yield stress level and magnitude and distribution of residual stress in structural members.