Vol.03, Issue 04, April 2018, Available Online: www.ajeee.co.in/index.php/AJEEE
EFFECTS OF MATERIAL CHANGES ON THE PERFORMANCE OF DIFFERENT INDUSTRIAL TRUSSES: A CONCEPTUAL REVIEW
1RAHUL SHARMA, 2SUMIT PAHWA
[1] PG Research Scholar; [2] Professor and Head
Department of Civil Engineering, Alpine Institute of Technology, Ujjain (M.P) INDIA Abstract- For many years, trusses have served as one of the excellent load carrying members for domestic and industrial buildings, and are becoming more-and-more useful day-by-day. Present research work is devoted to the trusses, and presents the summaries of research contributions made by different researchers in the field of trusses, identified gaps in the research and concludes with objectives of the new research.
Keywords: Trusses, load carrying members, research contributions.
1. INTRODUCTION
A truss is a structure where each element, typically a bar, only supports tension or compression forces because it is connected to other bars through what are assumed to be multiple spherical joints, although in some cases the joints may be separated in the actual construction. Truss structures and space frames have long been preferred solutions to the problem of maximizing structural efficiency, as they allow for very large increases in the flexural rigidity and load carrying capacity achievable from a given amount of material. The primary advantage of a truss over a monolithic or tubular structure is that grouping the material available into discrete local beam members allows for the overall size of a structure built from a given amount of material to be increased to take advantage of the highly non-linear scaling laws governing bending stiffness and strength (as determined by equivalent flexural rigidity) without being overly restricted by the strength limitations inherent in trying to make large, thin walled tubular structures. Another key advantage of truss structures is that they divide the
large structure into a number of local members which due to their slenderness, straightness, and attachment methods are able to act in a manner which approaches an ideal two-force member. A two force member, unlike a beam, experiences only tensile and compressive forces. Structures are considerably stiffer and stronger under axial loading then they are under bending loading, and so the use of trusses allows the material to experience lower stress levels and to be used more efficiently. In present research work , investigations on the research contributions made by different researchers in the field of trusses are made. The paper presents summaries of research contributions made by different researchers in the field of trusses, identifies gaps in the literature, and concludes with the objectives of new research.
2. RESEARCH CONTRIBUTIONS IN THE FIELD OF TRUSSES
Table 2.1 shows the summary of research contributions made by different researchers in the field of trusses.
Table 2.1: Research Contributions in the Field of Trusses S.No Researcher
(Year ) Contribution
1. Hou et al.
(2017) Concrete filled steel tubular truss (CFST truss for short) structures composed of CFST members as chords and steel tube members as braces are having expanded utilization in large-scale infrastructure constructions. In bridge structures, a concrete slab is usually provided on top of the CFST truss to form a hybrid CFST truss.
Besides previous research work on the experimental performance of CFST and hybrid CFST trusses reported in the companion paper (Han et al., 2015), detailed analytical behavior of such composite truss systems is needed. This paper thus presents a finite element analysis
Vol.03, Issue 04, April 2018, Available Online: www.ajeee.co.in/index.php/AJEEE (FEA) modeling on CFST truss without concrete slab as well as hybrid CFST truss with concrete slab subjected to flexural loading, which is validated through reported test data. The FEA modeling is then used to perform analysis on typical failure modes, moment-deflection relations, stress developments, material interactions and the load transferring paths of the composite truss systems. Influences of important parameters on the flexural performance of the composite truss are also investigated, including chord types, existence of reinforced concrete (RC) slab, strength ratio between chords, cross- section profiles, etc. Finally, simplified methods for calculating the flexural strength of CFST and hybrid CFST trusses are recommended and validated.
2. Zeynalian
et al. (2016) This paper presents an experimental study on the behavior of cold formed steel truss connections. Eighteen full scale cold-formed steel truss connections were tested. Of particular interests are the specimens maximum load capacity and the load-deformation behavior. The study also looks at the failure modes of the connections.
The behaviors exhibited by the connections are discussed and the design capacities calculated from the current CFS design standards are compared to the experimental results of the connections. This study investigates the main factors contributing to the ductile response of the CFS truss connections in order to suggest recommendations for connection designs, and improvements so that the connections respond plastically with a significant drift and without any risk of brittle failure. Also, a number of alternative fasteners are chosen and investigated for comparison with those that are currently specified for trusses' connections.
3. Xu et al.
(2016) This study presented a new method for forming the graded corrugated truss core sandwich structures based on an auto-cutting and mould- press process. The bending stiffness, strength and failure mechanism were investigated. Analytical models were presented to estimate the performance and failure mode of the sandwich beams. In order to demonstrate sensitivity of geometric parameters on the bending behavior of the truss core sandwich beams, a uniform and two kinds of graded corrugated truss core sandwich panels were fabricated and tested to probe different failure modes. Results showed that the distributions of the truss cores have strong influences on the bending behaviors of the sandwich beams. The predicting results were also compared with the measurements investigated. In general, the measured failure loads showed good agreement with the analytical predictions, except the uniform truss core sandwich beam. The graded corrugated truss core sandwich structures investigated appear to be promising candidates for lightweight systems and multifunctional applications.
4. Porta and Thomas
(2017)
Variable geometry trusses are composed, in general, of unit cells which can be modeled as bars connected by spherical joints. Under mild conditions, it has been shown that the only feasible cells are topologically equivalent to bi pyramids. Unfortunately, using standard formulations, the closed-form position analysis of bi pyramids is not a trivial task. Actually, it has only been achieved for bi pyramids with up to 7 vertices, whose closure polynomial has been shown to be of order 24. In this paper, using a distance-based formulation and a kinematic inversion for fans of tetrahedra, the problem is solved for bi pyramids with up to 11 vertices, whose closure polynomial is of degree 896. No other position analysis problem leading to such a high-order closure polynomial has been previously solved.
5. Chen et al.
(2018) Composite box girders with corrugated steel webs and trusses are a new type of advanced bridge structure proposed recently. This kind of
Vol.03, Issue 04, April 2018, Available Online: www.ajeee.co.in/index.php/AJEEE structure consists of a top concrete slab, corrugated steel webs and two bottom concrete-filled steel tubes connected by trusses. The resistance to torsion and overturning of this kind of structure is larger than that of composite bridges with a single concrete-filled steel tube.
This kind of structure is able to satisfy the requirement of rapid construction, environment protection and cost effectiveness. Two composite box girder bridges with corrugated steel webs and trusses have been or are being constructed in China. This paper presents the design of these two bridges in detail, which will provide valuable engineering experience for the further promotion of this kind of new bridge structure. Experimental research has been carried out to study the flexural behavior and the flexural capacity of this kind of new bridge structure. The test results show that when the test beam is at the elastic stage, the cross-section can be viewed as a plane section if only the strains of the concrete top slab and the bottom steel tubes are considered. The test beam shows good ductility throughout the whole loading process.
6. Huang et
al. (2018) This paper investigates the behavior of Warren-vertical CFT truss girders by conducting both experimental tests and finite element analyses. Experimental tests on three CFT truss girders are first conducted. The test parameter is the compressive strength of the concrete infill. Finite element models, which were developed and benchmarked previously by the authors, are then used to further investigate the behavior of CFT truss girders and the influence of parameters such as the brace-to-chord strength ratio, shear span-to- depth ratio, and concrete compressive strength. Results from the parametric studies indicate that CFT truss girders are flexure dominated if (i) the brace-to-chord strength ratio ≥0.8 and (ii) the shear span-to-depth ratio ≥4.8. Both the experimental tests and FEM analyses indicate that the concrete compressive strength has negligible effects on the failure mode of CFT truss girders. Based on results from the experimental tests and FEM analyses, design equations are also proposed for estimating the flexural strength of Warren-vertical CFT truss girders.
7. Liu et al.
(2015) This paper describes a novel composite tubular truss bridge with concrete slab and concrete-filled rectangular chords. With concrete slab plus truss system and joints reinforced with concrete and Perfobond Leiste rib, double composite truss bridge proved to be a fairly suitable solution in negative moment area. Perfobond Leiste shear connector (PBL) is widely implemented in the composite structure for its outstanding fatigue resistance. In this pilot bridge, Perfobond Leister ribs (PBR) were installed in the truss girder's joints, which played double roles as shear connector and stiffener. An erection method and overall bridge structural analysis were then presented. Typical joints in the pilot bridge were selected to analyze the effect of PBR. Investigation of the effect of PBR in concrete filled tubular joints was elaborated. Comparison has revealed that concrete- filled tubular joints with PBR have much higher constraint capability than joints without PBR. For rectangular tubular truss, the punching shear force of the concrete filled joint with PBR is approximately 43%
larger than that of the joint without PBR. Fatigue performance of the joint installed with PBR was improved, which was found through analysis of the stress concentration factor of joint. The PBR installed in the joints mitigated the stress concentration factor in the chord face. Therefore, the advantages of this new type of bridge are demonstrated, including the convenience of construction using rectangular truss, innovative concept of structural design and better global and local performances.
Vol.03, Issue 04, April 2018, Available Online: www.ajeee.co.in/index.php/AJEEE 8. Ufimtcev
(2017) In the present research work, an example of the interim analysis of vibrations of a 3-rod truss construction on the work of a half-sine pulse load is given. The example considers two options for the design calculation: in the first one there is the analysis of elastic-plastic oscillations with drawing a multi-cycle diagram of deformation for one of the rods; the second one – along with the physically nonlinear the constructive non-linear work of the system associated with the cyclical loss stability of one of the compressed rods is given. The features of the behavior of parameters of dynamic reaction in non linear oscillations are shown.
9. Shami et al.
(2018) Presenting the composite deck, which consists of concrete slab with profiled steel sheets fixed to the top layer of Double Layer Grid (DLG), proved its great efficiency in increasing the load carrying capacity for this type of structures. Earlier studies concluded that the application of the prescribed composite action had solved many problems facing the spread of DLG structures such as their prone to collapse in a progressive manner besides their suitability to be used only as roof covering structures. In addition, the application of the composite action introduced an economical solution due to considerable savings in steel material used in building the top layer of the DLG structures.
However, openings in the deck are needed for architectural purposes such as passing service ducts, day-lighting panels or passing shear walls or continuous structural elements. Adding such openings in the deck affects the efficiency of the composite deck in carrying the assigned loads especially if the openings are being added after the construction is completed. The current research introduced experimental tests along with numerical investigation using ABAQUS software for composite deck space trusses with common cases of support patterns and different deck opening locations. The study shows the obvious effect of the existence of openings and their locations on the load carrying capacity and ductility of DLG space structures.
10. Song et al.
(2016) Truss core sandwich panels have been widely investigated due to their superior mechanical performances. However, local defects or damages during preparation and service may reduce the strength significantly.
The objective of this paper is to examine the imperfection sensitive of this kind of structures under in-plane compression. The elastic and plastic buckling behavior of pyramidal truss core sandwich panels with local damages under in-plane compression are studied experimentally and numerically. Local damages including unbound nodes between lattice truss and the face sheet, missing lattice cells and holes in the face sheet are considered. In-plane compression tests of truss core sandwich panels with prefabricated local damages are conducted, and then a finite element model in conjunction with random number is developed to simulate the buckling behavior of the panel with randomly distributed damages in a specific region.
Experimental and numerical results show that, besides the damage extent, the location of unbound nodes and missing lattice cells have significant effect on the buckling strength of the pyramidal truss core sandwich panel. In addition, the local damage sensitiveness of sandwich panel with round holes in the face sheet is lower than that with square holes.
11. Huang et
al. (2017) Prestressed concrete-filled steel tube (CFT) truss girders usually consist of CFT chords, hollow steel tube braces, and high-strength prestressing strands. This paper investigates the behavior of prestressed CFT truss girders by conducting both experimental tests and finite element analyses. Experimental tests on five prestressed CFT truss girders are first conducted. The test parameters are the
Vol.03, Issue 04, April 2018, Available Online: www.ajeee.co.in/index.php/AJEEE prestress level and shear span-to-depth ratio. Results from the experimental tests indicate that: (i) the initial flexural stiffness and flexural strength of prestressed CFT truss girders increase as the priestess level or shear-spanto- depth ratio increases, and (ii) the failure modes of prestressed CFT truss girders are influenced by the prestress level and shear span-to-depth ratio. Finite element models, which were developed previously by the authors for CFT truss girders, are then modified to predict the behavior of prestressed CFT truss girders. Comparisons with experimental load-deformation responses indicate that the developed finite element models can reasonably predict the behavior of prestressed CFT truss girders.
12. Qi and Ma
(2018) Composite sandwich structures with lattice truss cores have both lightweight characteristics and multifunctional potential, which attract a large number of studies on topological optimization, manufacture process and performance evaluation in recent years.
However, reliability study on the joint is an inevitable research subject for engineering application, and few studies on inserts within sandwich panels with lattice truss cores are published. In this paper, composite pyramidal truss core sandwich panels with lightweight metallic quadrangular-prism inserts are designed and fabricated. Pull- out and shear tests are carried out to investigate their load capability and failure behaviors, respectively. It is observed that, compared to the honeycomb panels, the present sandwich panels with quadrangular-prism inserts normally can obtain a similar level of pull- out strength but a higher level of shear load capabilities.
13. Huang et
al. (2017) Concrete-filled steel tubular (CFST) trusses are widely used in bridge construction. Inadequate pumping of the concrete and other faults during construction and shrinkage of the concrete may cause interfacial imperfections such as deboning separation at the steel- concrete interface in many early built CFST arch bridges. It is important to investigate the effects of interfacial imperfections on the flexural behavior of CFST trusses. For this, experimental investigations are carried out and four experimental truss models with different interfacial imperfections are tested under four-point bending.
Finite element models are also developed to conduct the corresponding mechanism and parametric analyses. The test results show that interfacial imperfections between the steel tube and concrete core have significant effects on the ultimate loading capacity of CFST trusses. The ultimate loading capacity of tested models with 100% interfacial separation, 10% depth separation and 20% depth separation are 9.2%, 18.0% and 37.7% lower than that of the model with fully bonded steel tube and concrete core. The finite element model is validated by the test results and is used to conduct further parametric studies for effects of interfacial imperfections such as friction coefficient, interfacial separation ratio and depth separation ratio on the ultimate load carrying capacity of CFST trusses. The finite element results show that the effect of depth separation on the ultimate load of CFST truss is more significant than other interfacial imperfections, and that the ultimate load of models with a depth separation ratio kh=10% and kh=20% are 13% and 33% lower than that of the model with no depth separation. Therefore, it is very important to avoid the depth separation problem in the CFST truss structures.
14. Huang et
al. (2018) Concrete Filled Steel Tubular (CFST) structures are increasingly used not only for columns in tall buildings but also in the arch trusses of many arch bridges and in the truss girders of buildings and bridge decks. Therefore, the chords of Circular Hollow Section (CHS) truss arches and girders are increasingly filled with concrete, effectively
Vol.03, Issue 04, April 2018, Available Online: www.ajeee.co.in/index.php/AJEEE making them CFST structures. In addition to the strength and stiffness of the CFST members, the failure mode of the CFST joint connecting them to the tubular member is also affected by the concrete filling. In this study, truss girders with different web arrangements were tested, and their behavior investigated. The girders were not slender because they were designed to attain the peak limiting state for joint failure rather than chord failure due to bending moments. Moreover, two other types of girders were tested: one without concrete-filled chords (CHS girder) and anotherwith only the upper chord filled with concrete; thus allowing an investigation of how a concrete-filled chord affects joint failure mode. The geometry of the CHS girder joints was such that only chord face failure and punching shear failure could occur. The former required an inward deformation that was prevented by the concrete filling in a CFST girder with similar geometry. Finally, the study considers extending the Eurocode 3 and the AWS D1.1 code formulae, originally proposed for CHS joints, to calculate the resistance of CFST joints.
15. Zhao et al.
(2017) This paper presents an experimental study on the dynamic progressive collapse behavior of planar trusses. A specially designed member-breaking device has been invented to ‘break’ a predefined structural member suddenly, particularly a diagonal member in the experiments. Videogrammetric technique was adopted to obtain the full field 3D displacement of the remaining structure, and strain instrumentation was carefully used to monitor the internal forces of all members. In association with the experiments, finite-element simulations of the test trusses have also been performed, with extended analysis on the effect of removal of members at different locations. Experimental results in conjunction with the numerical analysis have shown that: (1) the truss with directly welded joints (specimen truss-WJ) was able to quickly regain balance upon member loss, and the load-redistributing capacity was provided mainly through catenary action developed in the bottom chord; (2) the truss with pinned joints (truss-PJ) behaved almost identically to truss-WJ, suggesting that when computational models of truss structures need to be developed to obtain structural responses under a collapse scenario, pinned-joints with continuous chord could be assumed; (3) the truss with rigid joints (truss-RJ) experienced progressive buckling of three diagonal members and was damaged severely, indicating a detrimental influence of excessive joint stiffness on the collapse resistance of trusses.
16. Ding et al.
(2018) In high-rise and super-high-rise buildings, steel outrigger trusses are commonly used as key components for improving the structural seismic performance. The joints between the trusses and core concretewalls enable reliable transfer of large axial loads from the former to the latter and therefore deserve special attention. In the present study, an equivalent fishbone-shaped beam–column model is developed for the analysis and design of the composite joint. The joint is composed of concrete-filled steel tube (CFT) boundary columns and double-skin steel plates, which work together to transfer the axial loads. In the proposed model, elastic beam–column elements are used to represent the CFT boundary columns, double-skin steel plates, horizontal rebar, and diagonal concrete struts in the wall. Two important geometric parameters of the model, namely the length of the double-skin steel plates and the height of the CFT boundary columns, are investigated. Comprehensive parametric analyses based on elaborate finite elementmodelswith solid and shell elements are conducted to reveal themain factors that determine the two above- mentioned parameters, and to propose calculating formulas. Then
Vol.03, Issue 04, April 2018, Available Online: www.ajeee.co.in/index.php/AJEEE themodel is further verified by finite element modelswith shell and solid elements in terms of the axial force distribution and horizontal displacement. Finally, a method for designing the truss–wall joint using the proposed beam–column model is developed and a typical design example is presented. It is demonstrated that the design of the joint is convenient and reliable once the axial load demand is determined by seismic analysis of the entire building.
17. Chang et al.
(2017) The importance of constructability is often understated in the design phase of a construction project. Issues regarding constructability often do not receive sufficient attention until it is too late for design changes. This paper proposes a quantitative measure of truss structural system design that can be used as an index of constructability in the aspect of standardization and repetition elements at early design stages. Construction can be regarded as a co- operative undertaking among architects, who specify the form of a building, and builders, who implement construction tasks. The designed form alone does not provide enough information to specify feasible processes for actual building. Sufficient fabrication information is needed so that fabricators can be completely certain concerning how to actually build the form. The goal of this study is to establish a model for estimating the amount of information needed for construction based on Shannon's information theory. This amount of information is based on uncertainty concerning assembly construction in the topological graph of the designed form, and the knowledge base shared by the designer and the builder in a design-build communication model. In this paper, the entropy of uncertainty is shown as being quantified as an index of constructability assessment for the attributes of standardization and repetition. Markov chain, Monte Carlo method and symmetry-group theories are also used in our model to analyze different levels of assembly. The scope of this research is currently focused on analyzing the constructability of truss structure systems. The assessment of constructability is demonstrated for six different types of truss structural systems. The five alternative designs are assessed for a schoolhouse project in Cambodia requiring easy construction, identified by our theoretical model. The results show that our methodology can help architects to design easily constructed truss structural systems and explore important design principles for improving constructability. The limitations and future works are discussed in the final two sections.
18. Bureerat Pholdee and
(2018)
This paper proposes the integration of an inverse problem process using radial basis functions (RBFs) into meta-heuristics (MHs) for performance enhancement in solving structural health monitoring optimization problems. A differential evolution (DE) algorithm is chosen as the MH for this study. In this work, RBF is integrated into the DE algorithm for generating an approximate solution rather than approximating the function value as with traditional surrogate- assisted optimization. Four structural damage detection test problems of two trusses are used to examine the search performance of the proposed algorithms. The results obtained from using various MHs and the proposed algorithms indicate that the new algorithm is the best for all test problems. DE search performance for structural damage detection can be considerably improved by integrating RBF into its procedure.
19. Clifton and
Lin (2016) Cold-formed steel trusses are a popular form of construction for light- weight buildings, particularly portal frame structures for which spans up to 25 m are increasingly common. A novel pin-jointed truss connector named the Howick Rivet Connector (HRC) has been tested, firstly in a T-joint arrangement, then in a truss assemblage to
Vol.03, Issue 04, April 2018, Available Online: www.ajeee.co.in/index.php/AJEEE determine its reliable strength and stiffness. Results show that the HRC performs similarly to a bolted connection in heavy steel in terms of failure modes observed, loads reached and proportionality limit.
Finite element models of both T-joints and trusses tested show good agreement with experimental results, particularly in the transition from elastic to inelastic behavior.
20. Zok et al.
(2016) Despite the recognition of the enormous potential of periodic trusses for use in a broad range of technologies, there are no widely-accepted descriptors of their structure. The terminology has been based loosely either on geometry of polyhedra or of point lattices: neither of which, on its own, has an appropriate structure to fully define periodic trusses. The present article lays out a system for classification of truss structure types. The system employs concepts from crystallography and geometry to describe nodal locations and connectivity of struts.
Through a series of illustrative examples of progressively increasing complexity, a rational taxonomy of truss structure is developed. Its conceptual evolution begins with elementary cubic trusses, increasing in complexity with non-cubic and compound trusses as well as super trusses, and, finally, with complex trusses. The con- ventions and terminology adopted to define truss structure yield concise yet unambiguous descriptions of structure types and of specific (finite) trusses. The utility of the taxonomy is demonstrated by bringing into alignment a disparate set of ad hoc and incomplete truss designations previously employed in a broad range of science and engineering fields. Additionally, the merit of a particular compound truss (comprising two interpenetrating elementary trusses) is shown to be superior to the octet truss for applications requiring high stiffness and elastic isotropy. By systematically stepping through and analyzing the finite number of structure types identified through the present classification system, optimal structures for prescribed mechanical and functional requirements are expected to be ascertained in an expeditious manner.
21. Eom et al.
(2017) In this study, punching-shear tests were performed to investigate the behavior of slabs supported by rectangular columns with capital. The slabs were subjected to an uneven shear transfer in two orthogonal directions by using the rectangular columns and different span lengths. Column capitals were used at the slab-column joints and preassembled bar trusses were placed at the periphery of the column capital to enhance the punching-shear capacity. Furthermore, the corners of the rectangular column and column capital were rounded to alleviate the shear stress concentration at the corners of the critical perimeter for shear. The test results show that the punching-shear strength of the slabs were significantly enhanced by the bar trusses.
The shear resistance of the bar trusses was mostly contributed by the diagonal bars undergoing significant strains. On the basis of the results, the effects of the uneven shear transfer and bar truss arrangement on the slab shear behavior were investigated. In addition, the punching-shear strengths predicted by ACI 318-14, Eurocode 2, and KCI 2012 were compared with the test strengths.
22. Liu et al.
(2018) This study proposed a new-type on-site all-bolted connection that connects a truss to a column and connects a column to a column in modularized prefabricated multi-story and high-rise steel structures.
The components in a module are welded together in the factory, and various modules are assembled together quickly using the proposed connection on site. The connection connects a truss to a column through cover plates that extend from the flanges as well as through the vertical connecting plates and the joint flitches. The stiffness of the connection undergoes step-like changes as the load changes. During
Vol.03, Issue 04, April 2018, Available Online: www.ajeee.co.in/index.php/AJEEE an earthquake, the cover plates slip relative to the chord members of the truss, dissipating energy. This study conducted tests and finite element analysis on the seismic performance of two specimens of the proposed bolted connection in which slip occurs between the cover plate and chord members, and some seismic performance data associated with the connection, such as hysteretic performance, skeleton curve, ductility, rotational capacity, stiffness degradation and failure mode, are obtained. Some parameters that affect mechanical and seismic properties of the connection were studied, and the slipping rule of the contact surfaces of the bolted connection was obtained. A comparative analysis of the test results for the slipping connection and the non-slipping connection shows that the slipping connection exhibited improved ductility and energy dissipation capacity without significantly reducing the ultimate bearing capacity, and most of the energy was dissipated from the slip. The proposed connection can be used for structures in seismic regions.
23. Taylor et al.
(2018) The development of in situ fabrication methods for the infrastructure required to support human life on the Moon is necessary due to the prohibitive cost of transporting large quantities of materials from the Earth. Cellular structures, consisting of a regular network (truss) of micro-struts with ~500 μm diameters, suitable for bricks, blocks, panels, and other load-bearing structural elements for habitats and other infrastructure are created by direct-extrusion 3D-printing of liquid inks containing JSC-1A lunar regolith simulant powders, followed by sintering. The effects of sintering time, temperature, and atmosphere (air or hydrogen) on the microstructures, mechanical properties, and magnetic properties of the sintered lunar regolith micro-trusses are investigated. The air-sintered micro-trusses have higher relative densities, linear shrinkages, and peak compressive strengths, due to the improved sintering of the struts within the micro-trusses achieved by a liquid or glassy phase. Whereas the hydrogen-sintered micro-trusses show no liquid-phase sintering or glassy phase, they contain metallic iron 0.1–2 μm particles from the reduction of ilmenite, which allows them to be lifted with magnets.
24. Wan and
Fan (2018) To provide solutions for large span structures, the use of a Tensairity truss with a 60-m span, which was studied numerically, is proposed.
The influence of the internal pressure and cable tension length on the mechanical properties is investigated for several load cases. A simplified spring model based on the vertical stiffness formula of the inflated air beam is presented, and a static design principle and a design method are proposed. The results show that the adoption of a steel truss can greatly increase the spanning capacity of a Tensairity structure, and the stiffness and load bearing capacity for the structure increase with the increase in air pressure. However, the structure is very sensitive to wind load, which can be improved by re-tensioning the lower cable. Comparisons between the simplified spring model and the original model show a good correlation for the displacement distribution and overall stiffness at a relatively high internal pressure for all load cases considered. The simplified design method will be an easy way for designers to evaluate the behavior of Tensairity structures, and can be conveniently applied to practical engineering cases.
25. Abramyan and Ishmametov
(2016)
The relevance of this article is explained by the increasingly extensive efforts associated with construction and reconstruction of buildings and structures having mainly architectural and cultural significance, as well as preserving their pristine ambience and integrity for use by future generations. Furthermore, reconstruction helps to serve a range of social demands, such as the provision of comfortable and safe
Vol.03, Issue 04, April 2018, Available Online: www.ajeee.co.in/index.php/AJEEE living conditions for people. The review of research publications shows that wooden structures are the first to lose their load-bearing capacity during the long-term use of buildings and structures. Still, the scientific literature mostly features the traditional labor-intensive methods of timberwork strengthening that further increase its weight, or the methods of external reinforcing with composite tapes. This article, for the first time, discusses the technology of the strengthening timber framing with butterfly shaped wooden inserts. Joints between existing rafters and wooden inserts are reinforced with two layers of the furniture duct tape and fine composite mesh pressed in between, with the plywood top finishing of the duct tape. The experimental studies that were in progress for two years showed that the technology suggested meeting all the reliability requirements applicable for timber trusses. As compared to traditional technologies, the suggested solution is less labor-intensive and more sparing in terms of the truss weight, as it only adds the weight of furniture duct tape, composite mesh and plywood at the joints. This is the applied research, and its outcome can be used not only for strengthening of roof timber, but also for reinforcing of wooden inter-floor joists
26.
Milton (2017)
The problem of determining those multiplets of forces, or sets of force multiplets, acting at a set of points, such that there exists a truss structure, or wire web, that can support these force multiplets with all the elements of the truss or wire web being under tension, is considered. The two-dimensional problem where the points are at the vertices of a convex polygon is essentially solved: each multiplet of forces must be such that the net anticlockwise torque around any vertex of the forces summed over any number of consecutive points clockwise past the vertex must be non-negative; and one can find a truss structure that supports under tension, and only supports, those force multiplets in a convex polyhedron of force multiplets that is generated by a finite number of force multiplets each satisfying the torque condition. Progress is also made on the problem where only subsets of the points are at the vertices of a convex polygon, and the other points are inside. In particular, in the case where only one point is inside, an explicit procedure is described for constructing a suitable truss, if one exists. An alternative recipe to that provided by Guevara Vasquez et al. (2011), based on earlier work of Camar-Eddine and Seppecher (2003), is given for constructing a truss structure, with elements under either compression or tension, that supports an arbitrary collection of balanced forces at the vertices of a convex polygon. Finally some constraints are given on the forces that a three- dimension truss, or wire web, under tension must satisfy.
27. Rumlová and Fojtik
(2016)
Using of timber in civil engineering is increasing at the moment. Main timber ele-ments are used for main supporting structures, typically for buildings, roofs, and footbridges or towers. This work studies unique timber trusses as a supporting roof structure of spatial timber building. Timber trusses are used as roof supporting construction for objects with open inside space, especially halls or office buildings.
This paper resolved critical joint in roof construction which is created by four timber trusses. The FEM model monitored strain changes in critical places of resolved joint.
28. Zhang et al.
(2018) A novel lightweight hybrid fiber-reinforced polymer (FRP) – aluminum space truss structure that consists of two triangular deck-truss beams has been designed for rapid emergency bridging system. This paper reports a largescale pure torsion test on a cantilever full-scale specimen to evaluate the detailed linear-elastic torsional behavior and the load-carrying mechanism of the hybrid twin-trackway spatial structure. Additionally, a structural computational finite element
Vol.03, Issue 04, April 2018, Available Online: www.ajeee.co.in/index.php/AJEEE model (FEM) was constructed and validated against the experiments.
To fully understand the load-carrying mechanism obtained from the experiments, numerical analyses were performed by equivalently converting the torsion reaction of the hybrid twin-trackway structure to the bending and torsion of its twin triangular deck-truss beams.
The results indicate that the experimental structure exhibits a good and specific torsional response, which can be well described by FEM.
The unidirectional pultruded FRP profiles are mainly subjected to axial forces and are thus appropriate for application to this unique twin-trackway space truss, unlike in the case of the alone single- trackway triangular beam under torsion. The vertical bending of the twin triangular deck-truss beams play a key role in the behavior of load-carrying of the entire bridge, unlike in the case of the conventional torsional calculation method for the separated box beam.
In the initial design, the torsional calculation of such a novel bridge can be carried out using the flexural analytical and numerical models of the triangular deck-truss beam.
29. Madah and
Amir (2017) A unified approach that accounts for various buckling phenomena in truss design optimization is presented. Euler buckling of slender members, global buckling and stability of sequences of bars are all considered by optimizing the geometric nonlinear response instead of by imposing a large number of constraints. In the proposed approach, each truss member is modeled as a sequence of co-rotational beam elements with appropriate end-releases. By applying various imperfections, buckling of single truss members, unstable configurations and global buckling can be taken into account implicitly. A detailed discussion on key aspects of the proposed approach is presented, showing how the choice of imperfections highlights certain buckling types and leads to respectively stable designs. A comparison to other approaches and to results from the literature shows that the proposed approach can ensure local and global stability without actually imposing any buckling constraints.
Finally, truss optimization for various levels of global deflections is presented, exposing the potential of the formulation for optimizing highly nonlinear responses.
30. Tejani et
al. (2018) Many engineering structures are subjected to dynamic excitation, which may lead to undesirable vibrations. The multiple natural frequency bounds in truss optimization problems can improve dynamic be- haviour of structures. However, shape and size variables with frequency bounds are challenging due to its characteristic, which is non-linear, non-convex, and implicit with respect to the design variables. As the main contribution, this work proposes an improved version of recently proposed Symbiotic Organ- isms Search (SOS) called an Improved SOS (ISOS) to tackle the above-mentioned challenges. The main motivation is to improve the exploitative behavior of SOS since this algorithm significantly promotes exploration which is a good mechanism to avoid local solution, yet it negatively impacts the accuracy of solutions (exploitation) as a consequence. The feasibility and effectiveness of ISOS is studied with six benchmark planar/space trusses and thirty functions extracted from the CEC2014 test suite, and the re- sults are compared with other meta-heuristics. The experimental results show that ISOS is more reliable and efficient as compared to the basis SOS algorithm and other state-of-the-art algorithms.
31. Bezerra et
al. (2018) Shear connectors are important in composite steel-concrete beams.
This work presents a new connector, named truss-type shear connector. This connector is an alternative to replace stud bolt in special situation. The connector’s geometry was conceived aiming at
Vol.03, Issue 04, April 2018, Available Online: www.ajeee.co.in/index.php/AJEEE low cost, easy execution, high resistance, and efficiency concerning slipping and uplift. Six specimens were constructed for push-out tests comparing this alternative connector with stud bolts. The behavior of the specimens was investigated for collapse, slipping and uplift.
Experimental results were compared against numerical FE simulation showing good agreement and providing a global view of the truss-type shear connector behavior and its viability.
32. Woods et al.
(2016) This paper presents the design, analysis, manufacturing, experimental testing, and multi objective optimization of a new family of ultra- efficient composite truss structures. The continuously wound truss concept introduced here is a versatile, low cost and scalable method of manufacturing truss structures based on a simple winding process. A prototype truss configuration is shown and experimentally characterized under torsion and three point bending loads. A large deformation implementation of the direct stiffness method is shown to provide good prediction of the stiffness properties of the prototype truss. This model is extended to include strength prediction with multiple failure modes. The design space achievable with these truss structures is then explored through multiobjective optimization using the NSGA II genetic algorithm. These continuously wound truss structures have the potential to provide between one and two orders of magnitude increase in structural efficiency compared to existing carbon fiber composite tubes.
2.1 GAPS IN THE RESEARCH AND OBJECTIVES OF NEW RESEARCH On the basis of survey of above literature, following research gaps are being identified.
1. There is very limited research which compares different industrial trusses;
and
2. There is almost none research available which analyses the effects of material changes on the performance of trusses.
On the basis of gaps in the research, following objectives are being proposed for the new research.
1. Analyze the effects of material changes on the performance of different industrial trusses;
2. Ranking of different combinations of materials and trusses.
3. CONCLUDING REMARKS
Present research work portrays the summaries of research contributions in the field of trusses, and identifies the gaps in the research and objectives of new research. Based on these foundations, a new research work is proposed which shall lead the trusses in the direction of strength enhancement.
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