Composite Truss Research Articles

Optimal depth selection of composite tubular-floor trusses based on cost estimation

The significance of this study initiates from the need to produce a selection guidance on the span range, span-to-depth ratio and scheme of the composite floor truss system to provide optimum performance and cost effectiveness for a particular application area. With this objective a parametric study was designed, based on three parallel chord trusses (Pratt, Howe, and Warren) using Rectangular Hollow Structural Shapes, a constant panel size of 2.5 m, four composite floor European-profiles and a range of load intensities. Hence, the span-to-depth ratios, RS/D, and dead-to-live load ratios, RDL/LL, were ranged from 3 to 27 and 0.84 to 3.22, respectively, for each truss type. The optimization was performed by using the design results of RFEM (2018) software for approximately 675 composite floor trusses with the objective of selecting optimal depth for each truss model. In addition, this paper attempts to introduce a cost function by considering the material, fabrication and painting costs and comparative figures allowing the design to be tailored with a focus on cost reduction. Accordingly, for all truss types, span-to-depth ratio of 9 to 12 with a span range of 7 to 23 m provides the most cost effective solution. Structural steel and the welding process are the two parameters that are found to have the highest impact on total cost.

Analysis Of Steel-Rcc Composite Deck Bridge

: In the literature, provisions for analysis and design of steel-RCC composite deck type truss and cable-stayed bridges do not exist. A composite deck type truss bridge model is analyzed using STAAD Pro V8i software and a model with the same dimensions is tested in the laboratory. The experimental test results are used to validate the STAAD analysis results.
 Bottom chord strain and mid-span deflection of the composite bridge model as found from the STAAD analysis and the laboratory experiment closely tally with each other. This validates the standard STAAD analysis results. However, in the top chord member, due to shrinkage cracks in the deck slab concrete, the experimentally recorded strain is higher by about 100% than the STAAD analysis result. 
 Shear force in studs is considerably large near supports and joints as compared to the midsection. Therefore, the design of shear studs may be carried out based on the shear forces in the studs found from the STAAD analysis. 
 Thus it is recommended that STAAD or any other standard finite element analysis software can be used for analysis and design of the composite bridges.

A combined finite element and hierarchical Deep learning approach for structural health monitoring: Test on a pin-joint composite truss structure

Structural Health Monitoring (SHM) is an emerging field of engineering with a wide range of applications. The most common SHM strategies operate on structural responses through vibration measurements and focus on training mathematical classifiers which are used after to identify damage in unknown responses. Classifiers may additionally locate damage when adequate labeled damaged data is available. In the present work, a novel SHM method is presented where labeled damaged data is generated through FE models for a pin-joint composite truss structure employing a model-based approach for the problem of data acquisition. The truss is made of carbon fiber reinforced polymer (CFRP) members joint on aluminum connections forming a complex and large FE problem. A Deep Learning (DL) Convolutional Neural Network (CNN) classifier is trained on the FE generated vibration data combined with a hierarchical multiple damage identification and location scheme. The numerically trained CNN is after validated on experimental statuses of the truss in both damage detection and location, proving to be robust and accurate for the considered test case. The potential of hierarchical CNNs with FE based SHM data for multiple damages is investigated in this work and a comparison is given between hierarchical and direct multiclass CNNs. The large performance gains of the former are proven for the studied experimental case highlighting also the importance of SHM system architectures with CNNs.

Mechanical behavior and energy dissipation of infilled, composite Ti-6Al-4V trusses

Trusses are open, three-dimensional structures with repeatable unit cells useful for high-specific strength, stiffness, and energy-dissipating applications. By infilling Ti-6Al-4V trusses with an incompressible elastomer (polydimethylsiloxane) or compressible foam (polyurethane), we demonstrate non-porous composite materials with controlled mechanical properties. The advantages of infilled composite trusses include corrosion resistance, density- or strength-matching, and the creation of a continuous external surface that can enable surface properties such as resistance to aerodynamic pressure and biomedical compatibility. Flexural and compressive testing of composite trusses show reproducible behavior dominated by the underlying truss in elastic and plastic regimes. Compared to unfilled trusses, those filled with an incompressible elastomer or compressible foam delay initial compressive failure to higher strains. For all investigated energy dissipation metrics, foam-infilled trusses demonstrated equivalent or improved performance compared to unfilled ones. This included plateau stress, volumetric energy dissipation (+19%), and energy absorption efficiency (+12%) and ideality (+20%). For the highest tested truss relative density (ρ∗ = 0.43), 150% improvement in volumetric energy absorption was observed. Compressive loading of the incompressible siloxane-filled trusses yielded higher peak failure stresses but at reduced energy dissipation. Composite trusses can therefore serve as structural solutions to improving energy absorption in higher stress applications with minimal increases to density.

A New Composite Truss Bridge and a Study on Its Dynamic Characteristics with FE and Experimental Methods

Improvements to the dynamic characteristics and stiffness of composite girder bridges are necessary to expand their applications and capabilities. The natural frequency of a bridge directly reflects the dynamic characteristics of a structure. From the calculation principle for the natural frequency, the natural frequencies of a bridge can be significantly increased if the load increases slightly while the structural stiffness increases significantly. Based on this, a new type of concrete-steel composite truss bridge is proposed. The new bridge has a reasonable new arrangement for the position of the concrete and steel, according to the bending moment law for continuous girders. The mechanical analysis of the new bridge shows that it has the characteristic of adding a small amount of load at a reasonable position, which can significantly improve the stiffness. Therefore, it is possible to achieve the purpose of improving the dynamic characteristics so that they are far better than those of a conventional composite truss bridge. To further study the dynamic characteristics of the new composite truss bridge, the finite element (FE) method was used to analyse the new bridges, and the results are compared with those of conventional composite truss bridges. Furthermore, several parameters that influence the dynamic characteristics of the new composite truss bridge were studied. Finally, the dynamic characteristics of the small-span new bridge were studied by finite element analysis (FEA) and experiment. The results show that the new composite truss bridges with different span arrangements and different second-stage dead loads always have better natural frequencies and stiffness advantages. Therefore, the new composite truss bridge is suitable for girder bridges with strict requirements for their stiffness and dynamic characteristics, especially for super-long span high-speed railway girder bridges.

Experimental and numerical analysis of composite steel and concrete trusses

Abstract In the present work, two composite trusses formed by tubular shapes supporting a concrete slab were evaluated. Based on analytical formulation related to the problem, according to recommendations of standards, numerical analyses were performed, with models created using the software Ansys, and an experimental analysis with full-scale tests. Good agreement between the three analysis types was observed. A possible shear connection failure in one truss was observed. With a change in the second truss's connector length, an increase in the structure's strength and rigidity was achieved. In this study, because the shear connectors were directly welded on the upper chord wall, local effects with localized plastifications were evidenced.

Micro and Macro Structural Investigations on Welded Joints of Composite Truss Steel Concrete Beams

The results of an experimental test campaign including micro and macro investigations on welded joints typically used in Composite Truss Steel‐Concrete beams are presented. The research was carried out with the aim of assessing the relevance of welding effects on the mechanical performance of different typologies of steel grades that can be used to realize the internal truss steel system, connected to the bottom steel plate used with the double structural and formwork function. Two different steel typologies were adopted for the steel truss: the “traditional” structural micro‐alloyed steel, normally used for composite steel‐concrete elements, and the typical reinforcing steel with TempCore® structure, achieved through the application of two‐phase thermomechanical treatment of quenching and tempering. The interest in the possibility of adopting reinforcing steel for the internal truss arises from its potential economic benefit, finding its justification in the intermediate condition in which this structural typology lies, between composite steel‐concrete and ordinary reinforced concrete buildings. Welding has a strong impact on such reinforcing steel material, resulting in relevant drops of ductility and brittle failure usually taking place in correspondence of the heat‐affected zone. So, it is advisable to refrain from using such steel grade, especially in constructions in seismic‐prone areas, where ductility is a major influencing and design factor.

Study on Mechanical behavior and equivalent calculation of GFRP- stainless Steel Composite Truss Bridge

GFRP is a kind of carbon fiber composite reinforced material, which has attracted wide attention in the engineering field because of its light weight, high strength, corrosion resistance and so on.The solid plate and shell finite element model of full GFRP truss bridge is established by ABAQUS, and its mechanical characteristics are analyzed. The study shows that the stress of each element is less than the material strength, but the mid-span deflection of the truss bridge exceeds the allowable value of the specification, so three kinds of stainless steel plate layout schemes are considered, and the structural gravity, mid-span deflection change and element stress are compared and analyzed. Finally, it is concluded that the upper and lower stainless steel plate has a great contribution to enhance the vertical stiffness of the GFRP truss bridge. The stainless steel plate largely replaces the upper chord under pressure and the lower chord is pulled. On this basis, the stainless steel plate beam filled between oblique bars is equivalent to the upper and lower chords by using the idea of average equivalence and the principle of equal mass. The finite element software analysis shows that the equivalent error is very small.

Reliability calibration for the design of multiple-chord CFST trusses by advanced analysis

Concrete-filled steel tubular (CFST) truss with complex configurations are now widely used in practice, especially in large-scale bridge constructions. For such complex composite trusses, traditional structural analysis approaches are readily applied for the safety checks of individual members and connections, whilst inelastic analysis and reliability calibration are very limited. Recently, the development of advanced system-level analysis that takes into account various nonlinearities and uncertainties allows a rational reliability calibration for CFST trusses to assess their structural reliability. This paper aims to present reliability calibrations on three typical CFST trusses (two-chord, three-chord and four-chord) by advanced finite element models implemented with random uncertainties. The established finite element models are validated against experimental results. Afterwards, stochastic finite element analyses (FEA) are conducted taking into account the material and geometric nonlinearities, the random initial imperfections and the potential model errors. Using the obtained statistics of resistance, reliability calibration is then undertaken to calculate the reliability indexes of the three typical CFST trusses in respect of resistance factors under various load conditions, with the target reliability discussed in accordance with AASHTO and ANSI/AISC 360–16. The proposed novel computational approach and the reliability calibration contribute to both the practical design and the standard drafting for CFST trusses.

Conceptual design of 1000 m scale steel-UHPFRC composite truss arch bridge

Excessive self-weight and difficulty in construction are the main issues confronted by super-long-span arch bridges. To address these issues, a conceptual design of steel-ultra-high performance fibre-reinforced concrete (UHPFRC) composite truss arch bridge with a main span of 1000 m was proposed, and the corresponding structural responses were numerically investigated based on finite element analysis (FEA) in this study. In this proposal, the UHPFRC was applied to box arch ribs for bearing the large axial forces, and the steel was used for web members and transversal connectors to avoid the risk of cracking. Such composite arch bridge has a much lower self-weight than traditional concrete arch bridges and avoids the need for welding on thick steel plates since only thin steel elements (thickness not exceeding 40 mm) are used compared to steel arch bridges. The cantilever erection with cables support was adopted during the main arch erection. In this scope, the temporary erection cables merely need to bear the self-weight of two truss arches and the transversal connectors during each closure and the process is repeated four times, which thus reduces largely the cost of temporary supports for construction and increases the feasibility of the construction. Based on the FEA results, the UHPFRC arch ribs are always in compression at a maximum compressive stress of 63.8 MPa. Furthermore, the stability, stress, and stiffness of each component during each construction stage meet the requirements of the code. By the comparative studies of the steel arch bridges, UHPFRC arch bridges, and the proposed one, the steel-UHPFRC composite truss arch bridge has significant technical and economical advantages and is suitable for a bridge with a main span in the range of 500~1000 m.

Design and Technology of Composite Truss Cores for Sandwich Panels

The paper presents the results of a study of the possibilities of a new technology aimed at production of truss cores for sandwich panels. This technology is based on the combination of folding technology, tailored fiber placement, and transfer molding.

Effect of filling steel tube chords by concrete on the structural behaviour of composite truss girders

In this study, three specimens of Warren truss girders composite with concrete deck slab were tested experimentally under a central monotonic load to study the effect of the existence of concrete inside the chords. The load capacity, deflection, slip between the concrete slab and steel tube, and failure modes were reported. Both chords were filled with concrete to the first specimen, only the lower chord was filled with concrete and the upper chord remained hollow to the second specimen and both chords were kept hollow in the third specimen. The result indicated that the existence of concrete inside the chords has a significant effect on the load capacity, failure pattern, and the slip. The steel tubes of the upper chord filled by concrete prevent surface plasticity failure of the upper chord under loading and increase the ultimate load by 6.68 %. Also, filling the lower chord with concrete prevents the surface plasticity failure in the supports zone and caused an increase in the ultimate load by 39.59 %. The slip at the end of the specimen of two chords filled with concrete is less by 71% than the end slip of specimen of hollow top chord and higher by 46.8 % than the specimen of two hollow chords.

WrapToR composite truss structures: Measurement and modelling of mechanical response

Wrapped Tow Reinforced (WrapToR) trusses are ultra-efficient structures that are produced from composite materials using a novel winding process. In this study, a structural model based on the stiffness method is developed for the novel truss configuration to predict the pre-failure mechanical response. To validate the model, the mechanical response of the structures is experimentally investigated to a high level of detail using a series of three-point bend tests. Results of the tests highlight the importance of modelling behaviour of the truss joints due to both internal joint deformations and their effect on load transfer between members. The results also show that the developed model can predict deflections and strains to a reasonable accuracy across a range of truss configurations.

MONITORING BY FIBER OPTICAL SENSORS OF RELIABILITY OF OPERATION OF BUILDING STRUCTURES WITH EXTERNAL COMPOSITE REINFORCEMENT

This article describes of the actual state of building structures by the example of structures of reinforced concrete and metal bridges. It is shown that a high degree of wear of artificial structures leads to the need for a reliable assessment of their actual condition using modern methods and means of non-destructive testing and diagnostics, as well as strengthening exploited structures with polymer composite materials. The results of researches on fiber-optic monitoring and strengthening of bridge spans with composite materials based on domestic and foreign carbon reinforcing fillers and epoxy polymer matrices are presented. It has been experimentally shown that for reinforced concrete structures it is advisable to use composite strengthening systems using external reinforcement installed directly on the damaged object by contact molding. For metal structures, this approach is not applicable due to a significant difference in the coefficients of linear thermal expansion of composites and metals. In this case, an amplification system based on prefabricated composite truss systems made by autoclave and unautoclave molding can be applied. The obtained research results also indicate the advisability of joint use of monitoring systems and strengthening of damaged bridge structures by composites.

Flexural behavior of concrete-filled rectangular steel tubular composite truss beams in the negative moment region

Two concrete-filled rectangular steel tubular (CFRST) composite truss beams were tested to investigate the flexural behaviors in the negative bending moment region. The specimens were designed with different forms of concrete slab and shear connection as follows: one truss with slip-releasing shear studs and prestressed concrete slab and the other one with conventional shear studs and reinforced concrete slab. In the test, the load–deflection response, cracking development, ultimate bearing capacity, relative slip between concrete slab and steel truss, and strain distributions on steel truss, concrete slabs and reinforcement were measured. The test results indicated that the difference in concrete slabs and shear studs had negligible influences on the ultimate bearing capacity, but significant effects on failure modes and stresses redistributions. Using the prestressed concrete slab and slip-releasing shear studs can improve the degree of prestressing applied to the concrete slab, thus effectively delaying the cracking development. For the purpose of the practical design, the formulae were derived to predict the cracking moment, concrete crack width under the serviceability limit state and the flexural bearing capacity under the ultimate limit state. The validation against test results showed that the proposed formulae were reliable.

Stress on Steel-concrete Composite Truss Joints Research Status and Application Overview

Based on the comprehensive analysis of various stress research schemes for steel-concrete composite truss joints, the current research status of steel-concrete composite truss joints and epoxy resin concrete at home and abroad are systematically elaborated. The existing problems in the current composite truss joints are analyzed, and possible solutions are proposed. At present, the research on epoxy resin concrete has been very extensive. Epoxy resin concrete has high strength, good toughness, high impact strength, good chemical corrosion resistance, wear resistance, water resistance, frost resistance, tensile resistance and compressive resistance, which make it widely used in engineering. The problem of using epoxy resin concrete instead of ordinary concrete in steel-concrete composite truss is put forward, analyzed and discussed.

Experimental study on vibration serviceability of steel-concrete composite floor

In this study, on-site testing was carried out to investigate the vibration serviceability of a composite steel-bar truss slab with steel girder system. Impulse excitations (heel-drop and jumping) and steady-state motion (walking and running) were performed to capture the primary vibration parameters (natural frequency and damping ratio) and distribution of peak acceleration. The composite floor possesses low frequency (<8.3Hz) and damping ratio (<2.47%). Based on experimental, theoretical, and numerical analyses on fundamental natural frequency, the boundary condition of SCSS (i.e., three edges simply supported and one edge clamped) is deemed more comparable substitutive for the investigated composite floor. Walking and running excitations by one person (single excitation) were considered to evaluate the vibration serviceability of the composite floor. The measured acceleration results show a satisfactory vibration perceptibility. For design convenience and safety, a crest factor βrp describing the ratio of peak acceleration to root-mean-square acceleration induced from the walking and running excitations is proposed. The comparisons of the modal parameters determined by walking and running tests reveal the interaction effect between the human excitation and the composite floor.

On the local identifiability of constituent stress–strain laws for hyperelastic composite materials

For natural composite materials such as biological tissues, mechanically characterizing the individual constituents and elucidating their roles in supporting structural integrity has remained experimentally challenging since the constituents can often not be isolated without impairment and require non-standard testing devices. Adopting an inverse viewpoint, we examine, in this article, macroscopic samples whose constituent architecture is accessible and investigate whether it is possible to conclude on the stress–strain behaviour of the individual constituents based on experimental measurements from standard material tests. Focussing on isotropic hyperelastic composites, a direct discretization of the constituents’ strain energy densities in terms of global shape functions is explored. In order to assess the local deterministic identifiability of material parameters near an initial estimate, we adopt a sensitivity-based criterion and determine feasible combinations of candidate experiments without recourse to experimental measurements. Both the local identifiability and attainable reidentification accuracy are investigated in detail for a composite truss and a composite sheet whose force–strain responses in uniaxial or biaxial tension tests, respectively, are mainly determined by the constituents’ volume fractions.

Shear connection, experimental and theoretical research

Abstract The resistance of steel-concrete composite trusses is significantly influenced by shear connection producing interaction between the steel beam and concrete slab. To create the interaction...

A possible analysis for failure of U.S. SMAP satellite

The Soil Moisture Active-Passive (SMAP) satellite is the only satellite with a large deployable space eccentric rotating ring truss antenna clamped along a generatrix and rounding a parallel axis. However, the active radar of SMAP satellite stopped working within months of its launch. What are the reasons leading to so dramatic consequences? It is a possibility that the satellite damage is caused by vibration. In this paper, the nonlinear breathing vibrations of the large deployable space eccentric rotating composite laminated ring truss antennas with the large radius are studied from a theoretical analysis of view. Referring to the equivalent model of the continuum circular cylindrical shell clamped along a generatrix, we propose a dynamic model of the eccentric rotating composite laminated circular cylindrical shell subjected to the lateral and the temperature excitations. Considering an eccentric rotating composite laminated circular cylindrical shell clamped along a generatrix and rounding a parallel axis, the nonlinear partial differential governing equations of motion are established by using Donnell thin shear deformation theory, von Karman-type nonlinear relation and Hamilton’s principle. The nonlinear ordinary differential governing equations of motion are obtained by using Galerkin discretization. Based on the theoretical model, the nonlinear breathing vibrations of the equivalent model are studied for the SMAP satellite antenna subjected to the lateral and the temperature excitations for the first time in this paper. Firstly, the effects of different parameters on the toggle condition of 1:2 internal resonance are studied. The effects of the radius and the eccentricity ratio on the natural frequencies are not obvious for the eccentric rotating composite laminated circular cylindrical shell. Furthermore, it is also found that the influence of the thickness and the eccentricity ratio on the resonant rotating speeds cannot be ignored for the eccentric rotating composite laminated circular cylindrical shell. Then, based on the case of 1:2 internal resonance and principal parametric resonance-1/2 subharmonic resonance, the parametric excitation T is selected as the controlling parameter to discover the nonlinear breathing vibrations of the eccentric rotating composite laminated circular cylindrical shell. The periodic and chaotic motions of the equivalent model for the SMAP satellite antenna are found when the rotating speed corresponds to the internal resonant point at the certain excitations for different lateral and temperature excitations. Therefore, the chaotic motions of the SMAP satellite antenna occur under the combined action of temperature parameter excitation and lateral excitation in the space environment. According to the research results of this paper, the active radar of the SMAP satellite may be damaged by severe nonlinear vibrations. We reasonably speculate that the failure of the active radar for the SMAP satellite antenna is caused by the nonlinear vibrations in 1:2 internal resonance. Thus, this paper not only provides a possible analysis for the failure of the SMAP satellite, but also provides the theoretical guidance for study of similar ring truss antennas. This research has important theoretical significance and engineering value.