Truss Elements Research Articles

Mesoscale analysis of Fiber-Reinforced concrete beams

Unlike traditionalconcrete,steel fiber reinforcementimproves durability and crack control. The current work developed an extensive numerical study, using a three-dimensional mesoscale model, to investigate the effect of steel fibers on the mechanical properties of steel fiber-reinforced concrete (SFRC) beams. The proposed model was developed using the numerical computing environment MATLAB. Concrete was simulated using solid elements with a damaged plasticity model. The steel fibers were randomly located and modeled by truss elements with an elastic–plastic material model, while the interface was represented by springs connecting the nodes of the concrete and steel fiber elements. Traction separation model behavior was assumed for the springs at the direction tangent to the fibers’ major axis and elastic with high stiffness in the normal directions. The proposed model was validated using experimental results with different fiber ratios. Moreover, a parametric study was conducted to investigate the effect of steel fiber ratios and orientations as well as the effect of the beam size. Good agreement with differences of 3%−5% at the peak loads and 3%−18% at the post-peak loads were obtained. The orientation of the steel fibers had a big effect on the behavior of the SFRC beams. A 73% increase in the peak load of the SFRC beams with aligned fibers in the flexural direction was obtained relative to the random alignments. Whereas the beams with steel fibers aligned in different directions showed unchanged behavior and strength. The beams with smaller sizes experienced higher variation between realizations and higher peak stresses than those with larger sizes for all fiber ratios. A clear size effect of type II in peak stresses was obtained for beams with different fiber ratios.

An energy-based study of the embedded element method for explicit dynamics

The embedded finite element technique provides a unique approach for modeling of fiber-reinforced composites. Meshing fibers as distinct bundles represented by truss elements embedded in a matrix material mesh allows for the assignment of more specific material properties for each component rather than homogenization of all of the properties. However, the implementations of the embedded element technique available in commercial software do not replace the material of the matrix elements with the material of the embedded elements. This causes a redundancy in the volume calculation of the overlapping meshes leading to artificially increased stiffness and mass. This paper investigates the consequences in the energy calculations of an explicit dynamic model due to this redundancy. A method for the correction of the edundancy within a finite element code is suggested which removes extra energy and is shown to be effective at correcting the energy calculations for large amounts of redundant volume.

Finite element analysis of steel-concrete composite connection with prefabricated permanent steel form

Composite structural members are widely used due to superior performance to traditional structural members consisting of either concrete or steel material. This study proposes steel-concrete composite beam-column connections utilizing prefabricated permanent steel form and presents a finite element analysis to ver-ify the structural performance of the system, which is based on the experimental data conducted under cyclic loading protocol simulating seismic action. Five different design specimens are covered where the key varia-bles include the asymmetric section of the steel beam, the type of the column, and the detail of longitudinal reinforcement placement. The specimens were modeled in ABAQUS with solid and truss elements for concrete and steel parts, respectively. In addition, the nonlinear material behavior of the concrete was considered in the model where the concrete damaged plasticity model was assigned. The interaction between concrete and steel was also investigated to capture the structural behavior of the specimens measured from the test. The analysis showed that the concrete section improves the structural performance of the composite beam while preventing the steel beam from bucking. The finite element analysis was not capable of catching the strength degradation at the ultimate state but provided reliable results with overall moment-story drift behavior.

Topology and size optimization for X-bracing system of nonlinear inelastic space steel frames

In this article, a Python-programmed advanced design paradigm is firstly introduced to topology and size optimization of the X-bracing system of nonlinear inelastic space steel frames. For that purpose, an advanced analysis method considering both geometric and material nonlinearities is utilized as an effective finite element analysis (FEA) solver. In which, X-bracing members are modeled by truss elements, while the beam and column members are simulated by beam-column ones. The bracing members’ cross-sectional area and their position are respectively treated as discrete size and topology design variables. The problem aims to minimize the weight of X-bracing system so that the constraints on the strength, inter-story drift and maximum displacement are satisfied. An adaptive hybrid evolutionary firefly algorithm (AHEFA) is employed as an optimizer. Numerical examples are exhibited to illustrate the powerful ability of the present methodology.

Multi-strut and empirical formula-based macro modeling for masonry infilled RC frames

It is widely accepted that infill walls play an important role in the structural response of buildings under seismic excitations. Disregarding their influences on the seismic design and evaluation of structures could be potentially dangerous. Therefore, a reliable numerical model is necessary. Because of its simplicity and efficiency, the equivalent strut model is the most widely used to represent infilled frames. In this study, a novel multi-strut macro model and associated empirical formulas for modeling infilled RC frames are proposed. The model was developed based on previous experimental observations. Fiber-section truss elements are used as the struts. All potential failure modes of the infill wall were considered by means of the equivalent stress–strain parameters of the struts. Empirical formulas for predicting these equivalent stress–strain parameters were developed and calibrated based on a comprehensive experimental database and regression analysis. Finally, blind validation tests of the proposed model and empirical formulas were performed to assess their reliability. Monotonic and cyclic load simulations of the infilled RC frames were carried out and compared with experimental results. The application of the proposed approach for both single-bay and multi-bay infilled frame simulations was examined.

Finite element modeling and simulating pilling of polyester fabric

PurposeThe paper aims to build a finite element simulation model for pilling of polyester hairiness on the fabric to study the effects of hairiness performance on pilling and reveal pilling mechanisms.Design/methodology/approachThe finite element simulation model of pilling of polyester hairiness was established by ABAQUS. Polyester hairiness was treated as elastic thin rod, which was divided by two-node linear three-dimensional truss element. The effects of hairiness elastic modulus, hairiness friction coefficient and hairiness diameter on frictional dissipation energy, strain energy and kinetic energy produced by pilling have been studied. The analysis solution values were compared with the finite element simulation results, which was used to verify finite element simulation.FindingsThe paper provides new insights about how to reveal pilling mechanisms of polyester hairiness with different performance. Comparing finite element simulation results with analysis solutions shows that the fitness is greater than 0.96, which verifies finite element simulation. Larger hairiness elastic modulus gives rise to higher friction dissipation energy and strain energy of hairiness but lower kinetic energy. Increasing friction coefficient enhances friction dissipation and strain energy of hairiness. However, kinetic energy decreases with the increase of friction coefficient. Hairiness diameter also has an important effect on hairiness entanglement and pilling. Increasing hairiness diameter can decrease friction dissipation energy but enhance strain energy and kinetic energy.Research limitations/implicationsFinite element simulation was verified by analysis solutions. The solutions include friction dissipation energy, strain energy and kinetic energy, which cannot measured b experiment. Therefore, researchers are encouraged to simulate pilling to obtain pilling grades, which be compared with experiment results.Originality/valuePilling of polyester hairiness was simulated by ABAQUS. This method makes pilling process visualization, and pilling mechanisms was revealed from non-linear dynamics.

Research Paper on Analysis and Design of Steel Truss by using Angle and Tube Section

Now a days many structures such as railway station roof, aircraft hangers, airport terminals, parking garage, industrial building roof, large factory roof, multi-story roof truss, parking garages roof truss are for the best truss section which will suited for that selected steel roof truss structures because of the large spacing required heavy concreting and large quantity of steel for beam, column and slab casting so that is why, it is uneconomical and deflection in member is more. That’s why most probable solution for this condition tubular steel truss is unique solution within the economical point of view and various parameter are high in strength to weight ratio, low maintenance cost, long life span, no angularity, easy to manufacture and install. In today’s construction industry most of the steel building are constructed with critical sections of steel which is analysis and designed also built by regular practices approaches, therefore result of such structures are under in heavy loads or highly expensive structures. So tubular trusses are the most effective and best possible replacement for regular steel angle section. As we compare various section it is best construction industry as one of the types of steel section is most light weigh, with less economy, and other technical parameters. For low-cost economy point of view which is the main objective of the research work includes comparison of regular steel angle section structures with tube section structure for selected steel roof truss conditions. After reading literature review it is found that 15-20% cost is saved by using tube section. Analysis and design of steel roof truss elements was carried out by STADD PRO V8i computer software, by manually applying Indian Standards codes of practices. The advantage of tube section buildings is under the economy of roof truss design. There are totally different ten types of the steel roof truss section available in market. As we comparing two of them which are angle and tubular section. Other are I- section, T-section, Channel Section, Round bars, square bars, Corrugated Sheet, expanded metals, Flat sheets. This research study is carried out to provides in comparing that which method is low in economy, more load capacity of load transport of roof to purlins and purlins to members then member to column and further column to RCC block then RCC block to soil subgrade. Comparing both the section on the economical parameters by STAAD PRO V8i Software by calculating steel take off and price comparison of both the section. Also comparing parameters like node displacement, node reaction, beam reaction, min. & max axial forces and beam stresses. Structural analysis and design of both section by STADD PRO V8i computer software. After reviewing literature review papers final research paper is based on optimum and accurate steel roof truss design. Manually calculate dead load, dead load and wind load by using Indian Standard Code of Practice IS 800:2007 and IS 875(Part 3)-1987. The STAAD PRO OUTPUT method is used for determining the quantity of steel (weight) & other parameter like max. vertical displacement, max. & min. vertical force, moment at X-axis, moment at Z- axis. After analyzing fully deciding and comparing least value of quantity of steel take off in software considered as most economical truss. Key Words: Structural Analysis, Conventional/Traditional Steel Truss, Angle Section, Tube Section, AutoCAD, STAAD PRO V8i, Steel Roof Truss, IS 800: 2007, IS 806: 1968, IS 875 : 1987 for Tube Section, etc.

Out‐of‐plane shear‐axial failure in slender rectangular reinforced concrete walls

AbstractOn 22 February 2011, one of the main structural walls of one of the tallest buildings in Christchurch, New Zealand (Grand Chancellor Hotel), had an extremely brittle and unusual failure that significantly damaged the building, severely compromising its structural stability. To this date, this peculiar failure mode has not yet been fully investigated and understood. Moreover, currently, it is not possible to identify and assess walls that are prone to this failure mode. Following recent findings based on experimental investigations, this failure mode was identified as out‐of‐plane shear‐axial failure. A Finite Element (FE) model was developed in DIANA to capture this failure mode, and through a numerical parametric study, the key parameters that contribute to the development of this failure mode in rectangular reinforced concrete (RC) walls were identified. Solid elements were used for the concrete material and embedded truss elements for the steel reinforcement. Bar buckling was not included in this investigation due to the limitation of DIANA in implementing the bar buckling and Menegotto‐Pinto models together, among which the latter was found to be more influential on the behaviour of RC walls investigated in this study. Based on the numerical and experimental studies conducted, an analytical method is proposed to: (1) identify rectangular walls prone to out‐of‐plane shear‐axial failure as a first‐level check for both design and assessment purposes; and (2) determine the out‐of‐plane drift capacity of rectangular walls prone to out‐of‐plane shear‐axial failure. Design recommendations are provided for rectangular walls prone to out‐of‐plane shear‐axial failure.

Development of new passive vibration control system in coupled structures with block and tackle

An innovative passive vibration control system employed pulley tackle mechanism (Movable Pulley Damper System: MPDS) in coupled structures is proposed in this paper. A cable can be continuously stretched several times to connect the two buildings through the pulley blocks to amplify the relative displacement and provide the high energy absorption efficiency to the damper linked at the middle of the wire. The principle and the theoretical formulation of the system are initially discussed. Also, the effectiveness of the MPDS is examined through the shaking table tests using a scaled-down building model. The experiments demonstrate the ability of the MPDS to mitigate the building response during earthquake excitations as well as the successful amplification of the damping effect. The validity of the mathematical formulation and the equivalent modeling of the MPDS using the truss elements are confirmed by comparing the analytical and the experimental results.

Reinforcement of concrete principal and secondary trusses after service damages

The paper studies reinforced concrete principal and secondary trusses of a one-floor industrial building made as a precast reinforced concrete frame. The aim of the work is to restore the serviceability of reinforced principal and secondary trusses after instrumental examination with regard to the detected significant corrosion damage of reinforcement and longitudinal cracks in the protective concrete layer with opening width of several millimeters. After the analysis of the building structural scheme, its stress-strain state is simulated in the MicroFe software, and a calculation model is developed allowing for the identified damages of reinforced concrete structures and the proposed design solution for the truss reinforcement. The serviceability restoration of principal and secondary trusses implies the creation of solid truss elements, the joint operation of the reinforcement with the repaired protective concrete layer, and secondary truss reinforcement with polymer fibers.

A novel practical truss-based approach for evaluation the non-linear behavior of steel plate shear walls

Nowadays steel plate shear walls (SPSW) are widely used as an effective structural system subjected to seismic loads. So far, several numerical approaches were presented to evaluate the non-linear behavior of these structures. Remarkably simplifications accomplished by researchers to performance-based design purposes, but the implementation of a practical method in commercial code to engineers’ utilization still remained a challenge. In this paper, a simplified approach based on (1D) truss elements is developed for the non-linear analysis of SPSWs. In this approach, the complicated continuous (2D) elements are substituted by two vertical elements (columns) and two diagonal rods (braces). The equivalent truss-based (ETB) system consists of continuous columns and pin-ended braces with a specific configuration. The axial and shear stiffnesses of the ETB system are provided by the axial behavior of columns and braces, respectively. A bi-linear stress–strain diagram of steel including strength drop due to buckling was adopted for ETB elements. The proposed method was benchmarked to several experimental SPSWs at the structural level. The specimens include five SPSWs with different aspect ratios in the absence or presence of openings and/or stiffeners. The obtained results by means of the novel approach including global behavior and local buckling modes compared with experimental results and available numerical predictions in the literature as well. The results proved the method is able to estimate the non-linear behavior of SPSWs in satisfactory accuracy with very limited computational cost.

Size, layout and tendon profile optimization of prestressed steel trusses using Jaya algorithm

Depending on the increasing raw material costs in the construction area, it is becoming more and more significant to design the structures using minimum materials. For steel systems, where raw material prices are relatively higher than reinforced concrete structures, prestressing is one of the factors that can reduce the cost. Therefore, this study aims to cost optimization of prestressed steel trusses, considering the size and shape variables, simultaneously. It is assumed in the study that the prestressing force is applied via a tendon settled under the bottom chord and shaped with deviators. The cross-sections of the truss elements and deviators are size variables; on the other hand, the layout of the truss beam and the profile of the prestressing tendon are the shape variables. Discrete and continuous values are preferred for the size and shape variables, respectively. Strength, slenderness, and displacement are considered as the constraints in the design of prestressed steel trusses, depending on the different prestress loss conditions. The Jaya, a popular metaheuristic algorithm, is used for the optimization procedure. As numerical examples, the optimization of trusses with different spans and shapes is conducted. The results achieved are compared with those of the non-prestressed trusses and the results in the literature. It is observed that the prestressing, especially thanks to shape variables used, provides a considerable cost saving in the optimum design of steel trusses.

A coupled implicit material point-finite element method for modeling reinforced materials

PurposeThis paper aims to introduce a method to couple truss finite elements to the material point method (MPM). It presents modeling reinforced material using MPM and describes how to consider the bond behavior between the reinforcement and the continuum.Design/methodology/approachThe embedded approach is used for coupling reinforcement bars with continuum elements. This description is achieved by coupling continuum elements in the background mesh to the reinforcement bars, which are described using truss- finite elements. The coupling is implemented between the truss elements and the continuum elements in the background mesh through bond elements that allow for freely distributed truss elements independent of the continuum element discretization. The bond elements allow for modeling the bond behavior between the reinforcement and the continuum.FindingsThe paper introduces a novel method to include the reinforcement bars in the MPM applications. The reinforcement bars can be modeled without any constraints with a bond-slip constitutive model being considered.Originality/valueAs modeling of reinforced materials is required in a wide range of applications, a method to include the reinforcement into the MPM framework is required. The proposed approach allows for modeling reinforced material within MPM applications.

Additive Manufacturing of Large Structures Using Free-Flying Satellites

In-Space Manufacturing (ISM) is being investigated as a method for producing larger, cheaper, and more capable spacecraft and space stations. One of the most promising manufacturing techniques is additive manufacturing (AM) due to its inherent flexibility and low waste. The feasibility of a free-flying small spacecraft to manufacture large structures using a robotic arm with an AM end effector has been examined. These large structures would aid the construction of a large space station or spacecraft. Using the Experimental Lab for Proximity Operations and Space Situational Awareness (ELISSA) at the Institute of Space Systems at TU Braunschweig, a process has been designed and tested which is capable of producing structures with arbitrary length. This process was demonstrated by manufacturing support free truss elements of unlimited length using a free-floating mobile robot. Avenues for further extending the process to produce structures of any size in 3D space are discussed.

Modeling methods of self-centering energy dissipation braces using OpenSees

Self-centering energy dissipation (SCED) braces as a high-performance structural member has been extensively investigated in the last decade. The unique hysteretic behavior of the SCED brace generally dominates the seismic performance of building structures. This paper presents three available simulation methods for predicting the hysteretic behavior of a typical SCED brace in the widely-used open-source computational platform OpenSees. The simulation methods are implemented using the built-in material and element libraries in OpenSees, and aim to investigate the advantages/disadvantages between different modeling methods. Furthermore, two general-purpose self-centering (SC) uniaxial hysteretic models are developed and implemented for modeling different types of SCED braces. Representative validation studies are then presented through using the developed material models to predict the experimental results of the SCED braces under cyclic loading. The SC hysteretic models can capture primary characteristics of hysteretic responses with reasonable accuracy. Additionally, an improved truss element is also proposed for straightforward application of the developed SC models. The users are able to define the experimentally-observed hysteretic features of the SCED braces in line with the envelopes established in the developed material models. A shaking table test of the SCED braced frame in the literature is further simulated to verify the feasibility of the developed material models and modified truss element under seismic loadings. The research outcomes validate a more convenient and accurate method for predicting the behavior of SCED braces and provide some useful insights on the modeling methods in OpenSees.

A Numerical Study to Predict the Mechanical Response of FRCM Composites

Fabric Reinforced Cementitious Matrix (FRCM) materials are increasingly common for strengthening existing masonry structures. Their popularity is due to their many advantages with respect to resin-based composites, especially when applied to stone supports. The constitutive behaviour of FRCM materials is defined by the combination of their tensile response and the bond behaviour with the masonry support, both depending on complex stress transfer mechanisms between matrix and fabric, especially in the post-cracking stage. This paper presents a numerical study which aims to predict the mechanical behaviour of FRCM systems through simple 2D models of truss elements and non-linear springs to simulate the fabric-to-matrix and composite-to-substrate interaction. The comparisons between results of numerical approach and experimental responses showing that the proposed methodology is an effective and easy tool to predict the mechanical behaviour of FRCM composites.

Modelling of Curved Masonry Elements Reinforced with TRM: From a Detailed to a Simplified Approach

Numerical modeling of curved masonry structures reinforced with TRM can be particularly demanding. Indeed, several failure typologies can be encountered when a masonry element is reinforced with this strengthening solution. In the case of arches and vaults, the curvature itself complicates furtherly a correct prediction. The paper wants to provide a reasonable way to model numerically curved masonry structures reinforced with TRM and explore the advantages and detriments of advanced simulation and simplified approaches. At first, an advanced micro-modeling is applied to an arch reinforced at the extrados. Then, the same approach is applied to a limited portion of the same arch and numerical lap shear tests are performed. Finally, a simplified model equipped with a set of truss elements is proposed.

Numerical Simulations of Masonry Elements Strengthened through Fibre-Reinforced Mortar: Detailed Level Modelling Using the OOFEM Code

A detailed level numerical model for Fibre Reinforced Mortar (FRM) using the free, opensource code OOFEM has been recently calibrated and validated by the authors through comparisonwith experimental characterization tests (i.e. pull-off tests, tensile tests and shear bond tests). In thispaper, the developed model is adopted to perform numerical simulations on FRM strengthenedmasonry elements. In particular, out-of-plane and in-plane bending tests and in-plane diagonalcompressiontests are simulated by adopting the same modelling hypostasis and characteristics andthe results are compared with experimental tests available in the literature. Both the masonry and themortar are modeled through solid elements, the yarns of the fibre-based mesh with truss elements andthe interactions among the components (yarns, mortar, masonry) by means of interface elements.Non-linear static analyses are performed, considering the materials and interfaces non-linearity. Thesimulations result capable to realistically reproduce the typical performances of masonry elements interms of global performances and damage pattern and permit to investigate on the resistingmechanisms and on the interactions between the components.

Prediction of flexural drift capacity in masonry walls through a nonlinear truss-based model

In this paper, the in-plane flexural drift capacity of masonry walls is numerically investigated. In particular, a nonlinear truss-based model is specifically developed to predict the monotonic response of in-plane horizontally-loaded masonry walls undergoing flexural failure, so that to investigate their deformation capacity. This novel modelling strategy assumes a band of nonlinear truss elements at the wall toe to account for flexural failure. The truss elements are supposed no-tension with plastic-softening behaviour in compression. This simple and original model is easily and fully characterizable by experimentally-based compressive stress–strain relationships available in the literature for different masonry types. The modelling strategy is validated against two different pier-scale experimental tests which experienced flexural failure. The model is then used to predict the flexural drift capacity of walls with different masonry types and geometrical features, subjected to a full-range of axial load ratios. As a result, drift capacity is found to nonlinearly decrease while increasing the axial load ratio, and to be sensibly dependent on the wall width (i.e. drift capacity diminishes while increasing wall width), for any masonry type. Finally, a simple analytic expression based on numerical results is deduced for the flexural drift capacity of masonry walls, function of axial load ratio, masonry type, and wall size. Accordingly, this analytic expression could be implemented in any structural analysis masonry-oriented commercial code to account for a consistent description of the flexural drift capacity of masonry walls.

Development of Vibration Control Structure on Suspended Ceiling Using Pulley Mechanism

A suspended ceiling system (SCS) is one of the most fragile and non-structural elements during earthquakes. However, effective seismic protection technologies for enhancing the suspended ceiling system have not been developed other than the steel bracing system. An innovative passive vibration control system is proposed in this paper, which equipped a damper-employed pulley amplification mechanism into the indirect suspended ceiling system, named the pulley–damper ceiling system (PDCS). Theoretical formulation and the detailed information on the system were presented first. In addition, a new rotational damper composition consisting of a non-linear viscous damper was developed to follow the large wire-cable stroke. Six types of the full-scale ceiling specimens of a 15.6-square meter area with different configurations were constructed for the preliminary experiments to evaluate the seismic performance and feasibility of PDCS under simulated earthquake motions. The comparative results of the shake table test demonstrated that the application of PDCS is capable of controlling both displacement and acceleration of the ceiling panels. This study also presents the nonlinear time history analyses by modeling a wire-cable as an equivalent truss element to transmit the relative displacement of the ceiling system to the damper. The analytical model accurately simulated the dynamic behavior of PDCS.