Composite Space Truss Research Articles

Structural performance evaluation of pultruded GFRP composite space truss: Experimental study and numerical simulation

This paper presents space truss structures assembled from pultruded square hollow glass fiber reinforced plastic (GFRP) members. The novel steel connectors are used to connect the GFRP members, which can significantly improve construction efficiency. The structural performance of the four-span space truss and space truss unit is evaluated by the four-point bending test and the static test, respectively. The test results show that the GFRP space truss structure exhibited satisfactory overall stiffness and load-bearing capacity. The failure modes mainly include shear failure of the bolt, local buckling of GFRP profiles, and local cracks at holes and cuts. The structural stiffness of the space truss unit increases at the post-failure stage, which is caused by the compression buckling of the pultruded GFRP profile. The structural stiffness of the four-span space truss decreases at the post-failure stage, and the large nonlinear deformation capability provides an early warning before the ultimate collapse. In addition, a finite element model considering material nonlinearity is developed to predict the failure mode, overall structural stiffness, and load-carrying capacity of the GFRP space truss structure.

Analytical Study on the Behaviour of Composite Space Truss Structures with Openings in a Concrete Slab

A space truss structural system is a three-dimensional arrangement of linear elements in a pyramid pattern forming a Double Layer Grid (DLG) system. Space trusses are an elegant and economical means of covering larger areas such as roof systems, in a wide variety of applications such as a stadium, aircraft-hanger, assembly hall, etc. The major problem encountered in using the space truss as a roofing system is the sudden failure of the whole structure due to critical buckling of the top chord member. Earlier research has shown that the optimal solution to overcome such a failure is by providing a small thickness of concrete slab over the space truss, so that the space truss with concrete slab (Composite Space Truss) will act as a floor system for the multi-storey building. For better ventilation and lighting in the building, the need for openings in the composite space truss is unavoidable; however, providing an opening in the concrete slab will reduce the load carrying capacity of the structure. The analysis of a composite space truss of size 30m x 30m with all possible locations of openings for four different support conditions was carried out using ANSYS in order to study the load - deflection behaviour. Further, the ductility factor and energy absorption capacity of the composite space truss with different locations of slab openings were compared.

Finite Element Simulation of Space Trusses

AbstractThe purpose of this paper is introducing a simplified and computationally efficient finite element model to investigate the nonlinear behavior of composite and non-composite space trusses. Two models were employed using the Finite Element ANSYS program in order to analyze the space trusses. The first model simulates the non-composite space trusses while the second model simulates the composite space trusses. Also this research presents the comparisons between the results of the current finite element models and four previous published space trusses in order to verify the validity of the current models. Comparisons between the results of the two models and the results of the four previous published space trusses indicated that the numerical analysis created by the FE ANSYS program using the two employed models can predict the general collapse behavior of the space trusses.

Parametric study on the stiffness and energy absorption capacity of composite space truss

Parametric study on the stiffness and energy absorption capacity of composite space truss

A study on ultimate behaviour of composite space truss

Space truss are widely used to cover large area.The main challenge of the composite space truss was transfer of shear from concrete slab to concrete. This paper presents an experimental study of the space truss with the concrete slab by introducing steel plates and bolts as shear connector. The Ultimate load carrying capacity of space truss 3 m × 2 m × 0.7 m with 50 mm concrete slab on the top was studied under two point loading. From the experimental results; it was observed that the composite action was achieved by introducing steel plate and bolts with the minimum slip of 0.82 mm and thereby strength and stiffness has increased. An analytical study using finite element analysis software ANSYS was carried out and it have subsequently compared with the experimental results.

Effect of floor openings on the capacity of composite space trusses

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.

Optimal Design Analysis of Prestressed Composite Space Truss

More than 40 prestressed composite space truss models of different dimensions are built with APDL design language, and the span, height, lattice number, prestressed value, section area of the chord, width and height of ribbed beam are chosen as design variables. With selecting total cost as objective function, constraint conditions such as strength, rigidity, stability, section size, prestressed limit and structural deflection are also considered, we conduct optimal design for structures by means of zero order optimization. From the results of regression analysis, the optimal span-to-height ratio, lattice number and empirical formula of optimal prestressed value can be found out for designers’ references.

Application and development of modern long-span space structures in China

Modern long-span space structures, developed during the 1970s and 1980s, are light and effective structures based on new technologies and light-weight high-strength materials, such as membranes and steel cables. These structures include air-supported membrane structures, cable-membrane structures, cable truss structures, beam string structures, suspen-domes, cable domes, composite structures of cable dome and single-layer lattice shell, Tensairity structures and so forth. For the premodern space structures widely used since the mid-twentieth century (such as thin shells, space trusses, lattice shells and ordinary cable structures), new space structures have been developed by the combination of different structural forms and materials. The application of prestressing technology and the innovation of structural concepts and configurations are also associated with modern space structures, including composite space trusses, open-web grid structures, polyhedron space frame structures, partial double-layer lattice shells, cable-stayed grid structures, tree-type structures, prestressed segmental steel structures and so forth. This paper provides a review of the structural characteristics and practical applications in China of modern rigid space structures, modern flexible space structures and modern rigid-flexible combined space structures.

Reliability Analysis of Composite Space Truss Based on Integral Loading Ultimate State

The paper makes a reliability analysis of composite space truss based on integral loading ultimate state. Double nonlinear numerical model is established based on finite element software ANSYS to track the ultimate loading capacity of the structure and confirm the failure mode of the structure; by the deep research and discussion for the composite space truss based on integral loading ultimate state, the scope of structural reliability index and sensitivity degree of various parameters to the reliability are obtained and the measures for improving reliability are proposed.

Research on Manufacture and Test of Advanced Composite Material Flange

Due to the problems of potential corrosion and thermal expansion differences between traditional metal connecting pieces and carbon fiber poles, it is difficult for them to meet the operating requirements of truss structures in the environment of stratosphere. Based on the large scale composite space truss structure of stratosphere aerostats, the carbon fiber flange connection joints were studied in the present paper. Adopting the three-dimensional full five- directional braiding technology, Toray T700S - 12K carbon fiber is used as the raw material to manufacture flange joint preform, and to manufacture flange forming by RTM(resin transfer molding) process. As demonstrated by tensile and bending tests, the composite flange joints have better mechanical properties than flanges manufactured by aviation aluminum alloy, and meet requirements of stratosphere truss structure connecting pieces. In conjunction with the results of finite element analysis, mechanical properties can be further enhanced by the improvements of the braiding process, the forming process and the physical dimension.

The Manufacture and Test of Advanced Composite Material Flange

Due to the problems of potential corrosion and thermal expansion differences between traditional metal connecting pieces and carbon fiber poles, it is difficult for them to meet the operating requirements of truss structures in the environment of stratosphere. Based on the large scale composite space truss structure of stratosphere aerostats, the carbon fiber flange connection joints were studied in the present paper. Adopting the three-dimensional full five-directional braiding technology, Toray T700S – 12K carbon fiber is used as the raw material to manufacture flange joint preform, and to manufacture flange forming by RTM(resin transfer molding) process. As demonstrated by tension tests, the composite flange joints have equivalent mechanical properties with flanges manufactured by common aviation aluminum alloy, and meet requirements of stratosphere truss structure connecting pieces.

Numerical Analysis and Experimental Study of Prestressed Diagonal-On-Square Composite Space Truss

The prestressed composite space truss (PCST) is a new kind of space structure composed of steel cables, steel tubes and reinforced concrete ribbed slabs. The prestressed steel cables are arranged in one direction or two directions within the plane of the bottom chord of the composite space truss. There are two main forms of PCST in practice; one is prestressed square on square offset composite space truss (PSSCST), the other is prestressed diagonal on square composite space truss (PDSCST). In this paper, the static behaviour of PDSCST is analyzed in detail using the linear finite element method. The first 10 natural frequencies of a PDSCST are calculated using the subspace iteration method and are found to be really close together, and all of the corresponding mode shapes are vertical vibrations. A simplified formula for calculating the first period is obtained by a linear regression method. The initial tension values in the cables to be applied during construction are calculated by the Release Tension Method which can also take into account the influence of different tensioning sequences. Finally, both the static behaviour of a PDSCST and the influence of different tensioning sequences are studied on a physical model test.

Nonlinear FE Analysis of Steel-Concrete Composite Structures

This paper presents an advanced nonlinear finite-element (FE) program developed for the analysis of general composite structures of steel and reinforced concrete, including composite space trusses. The elements used to represent the concrete slab and steel beam actions are described, and in particular the ability to model ribbed composite slabs of reinforced concrete on profiled steel sheeting is demonstrated. Attention is drawn to the usefulness of the layering technique in determining local stress redistributions associated with progressive through-depth cracking and yielding in the slab and steel beam elements. Concrete is represented as a nonlinear elastic isotropic material before cracking and nonlinear orthotropic thereafter, while steel is taken to be initially elastic with strain-hardening capabilities after yielding. All material models are empirical in origin. A specialized stub element with empirical nonlinear shear force-slip relationships is used at the concrete slab–steel beam interface to p...

New Structural Forms and New Technologies in the Development of Steel Space Structures in China

The last decades have seen major advances in the research, design and construction of steel space structures (space grid structures) in China. This paper provides a review of these developments, with particular attention to the new technologies and new structural forms employed in China. The following topics on new technologies and new structures are given emphasis: long-span and large-area grid structures; composite space trusses; composite reticulated shells; triple-layer space trusses; partial double-layer (single-layer) lattice shells; prestressed grid structures; cable-stayed grid structures; special grid structures; new types of joints; theoretical work and application research. Prospects for steel space structures in the 21st century are presented at the end of this paper.

Experimental Study of Composite Space Trusses with Continuous Chords

The last decade saw the emergence of a new type of space truss built with continuous chord members. Earlier studies on these trusses confirmed that besides the cost savings resulting from their simple jointing methods, their behaviour is sound and ductile. The present study investigates the possibility of using either a concrete slab or top timber boards acting compositely with the top chord, to improve the behaviour of these trusses. New techniques are developed to allow the easy and inexpensive attachment of both types of top continuum. With these techniques, a high level of shear interaction can be developed, leading to significant improvements in behaviour. The paper also introduces an analytical study based on the finite element method for the analysis of space trusses with continuous chords, both in the composite and non-composite states.

Design of top concrete slabs of composite space trusses

The design of composite space trusses is a demanding task that involves taking several decisions on the truss depth, number of panels, member configuration, number of chord layers and concrete slab thickness and grade. The focus in this paper is on the design of top concrete slabs of composite space trusses, and in particular their thickness. Several effects must be considered in the process of designing the slab before an optimum thickness can be chosen. These effects include the inplane forces arising from shear interaction with the steel sub-truss and the flexural. and sheer effects of direct lateral slab loading. They also include a constructional consideration that the thickness must allow for sufficient cover and adequate space for placing the reinforcement. The work presented in this paper shows that the structural requirements on the concrete slab thickness are in many cases insignificant compared with the constructional requirements.

Nonlinear Numerical Analysis of Composite Space Trusses

The composite action between an upper concrete slab and a double-layer space truss has been shown to have positive effects on the behaviour of such structures. Primarily, the prevention of the typical brittle behaviour of trusses and the introduction of appreciable ductility are among the important benefits. Substantial improvements have been achieved also in both stiffness and ultimate strength. The analysis of composite space trusses requires a careful study especially in the modelling of the shear connection between the concrete slab and the steel truss, involving shear studs mounted on both the nodes and the members of the top chord. Additionally, parts of the concrete slab may be projecting inside the top chord members, and therefore contribute to the shear interaction. This connection, being far from simple, could be modelled using various techniques. The present paper concentrates on these techniques, and numerical results are produced for each case (using a previously-developed and verified finite element program) and compared with the experimental results of a full-scale composite space truss tested earlier. As a conclusion of this work, two methods for preliminary and final design of composite space trusses are recommended for future use.

Sensitivity of Composite and Non-Composite Space Trusses to Member Loss

Since double layer space trusses have typically a large number of redundant members, it is frequently assumed that they are quite safe as the loss of one or more members can be accommodated without any noticeable effect on truss overall behaviour. The present study shows that every truss includes a number of critical members, the loss of any of which would cause force distributions that could lead to an overall premature collapse. The sensitivity of space trusses to member loss is clearly identified. The composite action between a top concrete slab and a space truss is also introduced as a means to control truss sensitivity to member loss. Factors that affect this sensitivity such as the truss supporting conditions are also investigated.

Numerical Analysis of Space Trusses With Flexible Member-End Joints

The conventional procedure for the analysis of space trusses, lattice domes and similar structures, assumes that member-end joints behave as pure pins or, in some cases, as rigid joints. However, experimental studies have shown that these joints typically exhibit some level of flexural stiffness and are therefore flexible (semi-rigid). It was reported that the characteristics of the space truss jointing system play a major role in truss response (see Refs. 1,2,3). The results of experiments conducted on space trusses with rigid or flexible joints produced less brittle behaviour than that found for assemblies with nominally-pinned joints. A nonlinear beam-column element with end springs has been developed to model the actual rotational stiffness of truss member-node connections, and its stiffness expressions are presented in this paper. Incorporation of this element in the numerical analysis of space trusses has led to better predictions of behaviour and strength when compared to the commonly-used two-noded frictionless truss element. This new element was used successfully in the numerical analysis of two non-composite and one composite double-layer space truss, and the results are presented in this paper.