Composite Arches Research Articles

Buckling of composite arches under indentation of a rigid plane

Buckling of composite arches under indentation of a rigid plane

Refined shear deformation theories for laminated composite arches and beams with variable thickness: Natural frequency analysis

A higher-order mathematical formulation with applications is presented in this paper for the free vibration analysis of arches and beams made of composite materials. Higher-order shear deformation theories are required to capture accurately the three-dimensional behavior of these structures through a one-dimensional scheme. Several orders of kinematic expansion are investigated and compared. In addition, the so-called zig–zag theories obtained through the use of the well-known Murakami's function are employed. Their effectiveness is extremely clear when laminates with inner-soft cores are analyzed. A set of numerical applications is presented to prove the accuracy of the current methodology. In particular, the comparison with exact solutions and results available in the literature or obtained through three-dimensional finite element commercial codes justifies the use of higher-order models, in which the displacement field is defined through the arbitrary choice of the maximum order of kinematic expansion. The in-plane vibrational modes of arches and beams, as well as annular ring structures, are computed and presented, discussing also the Poisson effect on the solutions.

Hilbert–Huang Transform based method for monitoring the crack of concrete arch by using FBG sensors

Little cracks in civil engineering structures may be the first indication of a serious defect. Crack monitoring of concrete is crucial for the integrity of civil engineering structures. In this paper, fiber Bragg grating (FBG) sensors were used for monitoring the crack of two CFRP concrete composite arches in MTS loading and unloading test. During the test, time series of strain data can be obtained by different FBG sensors. At the same time, initial cracking time is observed and recorded by the experimenters. After the test, a method based on Hilbert–Huang Transform (HHT) is used for determining the cracking time, which take the advantage of Empirical Mode Decomposition (EMD). The test results indicate that the HHT based method can be used to determined the cracking time when using different pasting method, even if the fix location of FBG sensors is not very accurate, and the 2nd IMF is better than other IMFs in crack monitoring, which is selected as a criterion in crack monitoring.

Special Issue on Sustainable Building Structures

Special Issue on Sustainable Building Structures

Studies of In-Plane Ultimate Loads of the Steel Truss Web–RC Composite Arch

AbstractThis paper describes an experiment on the in-plane mechanical behaviors of the steel truss web–RC composite arch subjected to the unsymmetrical concentrated loads applied simultaneously at the 2/3 and 5/6 span points of the arch. The experimental results show that loads were transmitted as shear forces through the steel truss webs. The maximum measured strain in two steel tubes near the cross section at the 5/6 span point was less than the yield strain, and punching shear failure was observed at the loading sections. Using the experimental model, the authors developed and performed a finite-element simulation. They found that double N-shaped webs might be the most conducive to the stiffness and bearing capacity of the composite arches and require comparatively less steel. The critical wall thickness of the web tubes at which punching shear failure occurred was 3.5 mm for this arch model. Given the same wall thickness, the ultimate bearing capacity of the composite arch decreased as the incline ang...

Time-Dependent Response of Spatially Curved Steel-Concrete Composite Members. I: Computational Modeling

This paper develops a numerical formulation for the nonlinear time-dependent analysis of steel-concrete composite members that are curved arbitrarily in space, which includes the effects of concrete shrinkage, creep, and geometric nonlinearity. This formulation is applicable to the analysis of composite arches and composite beams curved in plan, representing the limiting cases of members that are vertically and horizontally curved. The flexibility of the shear connection at the interface surface between the steel girder and the concrete deck is taken into consideration in the formulation. For an accurate serviceability limit state analysis of composite curved members, it is essential to include the shrinkage and creep response of the concrete component in the analysis. To also include the effects of geometric nonlinearity, a step-by-step incremental iterative solution procedure is adopted. Comparisons of the numerical solutions with those based on much less efficient and tractable viscoelastic ABAQUS shell element models, and with available experimental results, verify the accuracy of the computational formulation that is developed. Examples are chosen to illustrate the effects of partial interaction and initial curvature on the time-dependent behavior of spatially curved composite beams.

Erratum for “On the Flexural Analysis of Sandwich and Composite Arches through an Isoparametric Higher-Order Model” by Sudhakar R. Marur and Tarun Kant

Erratum for “On the Flexural Analysis of Sandwich and Composite Arches through an Isoparametric Higher-Order Model” by Sudhakar R. Marur and Tarun Kant

Transient dynamic analysis of higher order sandwich and composite arches

A higher order refined model with isoparametric elements is proposed to study the transient dynamic response of laminated arches/curved beams. The strain field is modeled through cubic axial, cubic transverse shear and linear transverse normal strain components. As the cross-sectional warping is accurately modeled by this theory, the shear correction factor is rendered redundant. The stress–strain relationship is derived from an orthotropic lamina in a three-dimensional state of stress, so that angle-ply laminates can be studied through one-dimensional elements. Consistent mass matrix is constituted for the equation of motion, which is solved by Newmark integration scheme. The higher order formulation is validated with available results and subsequently applied to arches with various curvatures, aspect ratios, boundary conditions, loadings and lamination schemes to evaluate its transient dynamic performance and suitable conclusions are drawn.

Trial design of arch bridge of composite box section with steel web-concrete flange

The concrete arch bridge is a natural and appropriate structural solution, aesthetically pleasing and easily integrated into the environment, especially in mountainous and island areas. However, construction difficulty and cost will increase with heavy self-weight when the span enlarges. A potential solution is to use a composite box arch ring with steel web-concrete flange. Taking Wanzhou Yangtze River Bridge (the longest concrete arch bridge in the world with a main span of 420 m) as a prototype, trial designs of a composite box arch with steel webs (including corrugated steel webs and plain steel webs) and concrete flanges were carried out. Comparison of quantities and structural behaviors of the prototype concrete arch with the two trial designed composite arch was presented. It is shown that the self-weight of the composite arch can reduce about 28% and the structures can meet the design requirements, therefore it is possible to use the two composite arches in long span arch bridges.

Nonlinear thermoelastic analysis of composite steel–concrete arches including partial interaction and elevated temperature loading

Composite structural elements containing two materials joined by means of an elastic shear connection find widespread use in both traditional and innovative structural engineering applications. The most common of these are steel–concrete members, joined by headed mechanical stud shear connectors. Despite their popularity and ubiquity, a thorough understanding of the behaviour of composite elements has yet to be fully developed, especially in an environment when they are subjected to elevated temperatures. This paper presents a somewhat generic model for the nonlinear elastic behaviour of composite arches subjected to sustained loading at elevated temperatures. The effect of partial interaction between the steel and concrete components in the tangential direction, as well as the variation of internal axial compressive forces along the member, is taken into account. Based on the governing differential equation obtained from the longitudinal equilibrium of an element of the concrete component, exact solutions for the displacement field are presented. The generic technique that is developed is shown to agree with solutions obtained from ABAQUS, and has a potential for inclusion in prescriptive design recommendations. The scope of the formulation is illustrated by presenting a parametric study of a steel–concrete composite arch at elevated temperatures, which indicates the variation of the displacements, axial force and internal bending moment with respect to both the thermal profile and the degree of partial interaction between the concrete slab and steel component.

Effects of Fiber Geometry on Energy Absorption of Arched Composites

This article presents the effects of fiber geometry on the energy absorption capability of arched composites. Composite arches with different fiber constructions, i.e., laminated and woven, and different fiber orientations, i.e., large angle (908) and small angle (158) between adjacent layers (for laminated) and between strands (for woven), were fabricated with a VARTM technique and centrally impacted at low velocities. It was found that both fiber construction and fiber orientation played important roles in the damage process. Composite arches with a large angle between adjacent layers and strands suffered delamination and fiber breakage during the buckling—post-buckling process while composite arches with a small angle between adjacent layers and strands suffered fiber bridging during the progressive damage process. Although the larger-angle composite arches absorbed more energy than the small-angle counterparts, the former experienced catastrophic damage after maximum impact while the latter retained significant integrity.

On the Flexural Analysis of Sandwich and Composite Arches through an Isoparametric Higher-Order Model

A higher-order arch model with seven degrees of freedom per node is proposed to study the deep, shallow, thick, and thin composite and sandwich arches under static loads. The strain field is modeled through cubic axial, cubic transverse shear, and linear transverse normal strain components. As the cross-sectional warping is accurately modeled by this theory, it does not require any shear correction factor. The stress-strain relationship is derived from an orthotropic lamina in a three-dimensional state of stress. The proposed formulation is validated through models with various curvatures, aspect ratios, boundary conditions, materials, and loading conditions.

Effects of Fiber Orientation on Out-of-plane and In-plane Natural Frequencies of Angle-ply Laminated Composite Arches

Variation of natural frequencies of in-plane and out-of-plane vibrations of 4-layer angle-ply composite arch with respect to fiber angle is investigated by the finite element method. The arch has clamped-clamped boundary conditions. It is concluded that the fiber angle is particularly important for in-plane vibrations. For any certain value of radius/length ratio of the arch, the natural frequency can be either increased or decreased with respect to fiber angle; therefore, angle-ply lamination can be preferable to cross-ply lamination. On the other hand, the effect of fiber angle on the out-of-plane frequencies can be used as an advantage in the design of laminated composite arches.

Free Vibration of Laminated Composite Circular Arches by Dynamic Stiffness Analysis

The dynamic stiffness method for studying the vibration characteristics of the laminated composite shallow circular arches is introduced in this article. The exact dynamic stiffness matrix is formulated from the analytical solutions of the governing differential equations of motion of the laminated circular arches, based on second-order shear deformation theory. The application of the present method is illustrated by miscellaneous numerical examples, in which the effects of material orthotropy, the lamination scheme, the curvature ratio, length-to-thickness ratio, and boundary condition upon the natural frequencies of the composite arches are investigated. Compared to those solutions available in the literature, the numerical results demonstrate the accuracy and effectiveness of the present method.

Free vibration of higher-order sandwich and composite arches, Part II: Frequency spectra analysis

The frequency spectra of the higher-order model, for laminated arches, are identified through a novel process, proposed in this paper. Besides the basic spectra corresponding to axial, flexural and shear, presence of higher-order spectra is established. Coupled spectra of first-order and higher-order degrees of freedom, in various combinations, are identified. Based on this spectra identification framework, the frequencies of sandwich and composite arches, for various boundary conditions are classified and presented. Also, the role of curvature and aspect ratio on the fundamental frequency of arches with various end-conditions is investigated, in the second part of this paper.

Free vibration of higher-order sandwich and composite arches, Part I: Formulation

A higher-order refined model with seven degrees of freedom per node is presented in this paper for the free vibration analysis of composite and sandwich arches. The strain field is modeled through cubic axial, cubic transverse shear and linear transverse normal strain components. As the cross-sectional warping is accurately modeled by this theory, it does not require any shear correction factor. The stress–strain relationship is derived from an orthotropic lamina in a three-dimensional state of stress. The proposed higher-order formulation is validated, in this first part, through arches with various curvatures, aspect ratios, boundary conditions and materials.

An Elastic-Plastic Thermal Stress Analysis of Cross-ply and Angle-ply Aluminum Metal-matrix Composite Arches

A thermal elastic-plastic stress analysis is carried out on cross-ply and angle-ply steel fiber reinforced aluminum metal-matrix laminated composite arch under uniform temperature distribution. The composite material is assumed to be strain hardening linearly and consists of 4, 8, 12, and 16 layers bonded symmetrically and anti-symmetrically. First yielding temperature, thermal residual stresses, and the distribution of these stresses under thermal loading are investigated by using the finite element method (FEM). The effects of orientation angle, layer number, and stacking sequence on the residual stresses are analyzed. The magnitudes of residual stress components increase gradually depending on the temperature increment. It is found that the orientation angle affects the yield point and the intensity of residual stresses significantly, while the layer number and stacking sequence result in slight differences.

Free vibration and stability of laminated composite circular arches subjected to initial axial stress

Natural frequencies and buckling stresses of laminated composite circular arches subjected to initial axial stress are analyzed by taking into account the complete effects of transverse shear and normal stresses and rotatory inertia. By using the method of power series expansion of displacement components, a set of fundamental dynamic equations of a one-dimensional higher order theory for laminated composite circular arches subjected to initial axial stress is derived through Hamilton's principle. Several sets of truncated approximate theories are applied to solve the eigenvalue problems of a simply supported circular arch. In order to assure the accuracy of the present theory, convergence properties of the first four natural frequencies are examined in detail. Numerical results are compared with those of the published existing theories. The present global higher order approximate theories can predict the natural frequencies and buckling stresses of multilayered circular arches accurately with a small number of unknowns.

Study of the model experiment of blinding-hole UCG

In order to meet the demand of recovering the “three unders” coal resources (under buildings, under railways, and under water bodies), the technique of blinding-hole underground coal gasification (UCG) is presented and its method is briefly explained in the paper. We did not merely explain the model experiment platform, experiment system, and process, but also analyzed the experimental results. The measured results indicate that the nature of gasification agent influences the temperature distribution of the gasifier as well as gas composition and heating value. According to the experimental results, on the condition of blind-hole gasification, when the gasification agent is air, oxygen-enriched air, steam with oxygen, and steam free of oxygen, the heating value of the gas is 3.46–5.75, 3.93–10.48, 8.3–11.0, and 9.17–14.51 MJ/m 3, respectively. The coal body around the gasifier (under the effect of high temperature), its organizational structure, and surface morphology have altered completely and formed the so-called dry distillation composite arches, which consist of porous zone, semichar zone, and char zone. As a result, the formation of the composite arches improves the physical and mechanical intensity of the coal body and the overall loading capacity and the integrity of the coal body around the gasifier. Thus, the blinding-hole UCG enables the recovery of the “three unders” coal resources, which, undoubtedly, lays an important theoretical foundation for the commercial-scale production of the UCG.

Stability Tests of Sandwich Composite Elastica Arches

A novel sandwich elastica arch is made by buckling its individual layers into shape, and then laminating them in place. One single-layer arch and four prototype sandwich composite arches with aluminum skins and discrete cores of balsa or oak wood were tested. Sandwich composite section resulted in a significant increase in the strength-to-weight ratio of the arch. The spacing of the core and the interlaminar shear strength are shown to affect the mode of failure and capacity of the arch. Test results and the relative ease of fabrication suggest that this novel arch can be used as a skeletal system for large clear-span domes.