Space Structures: Forms, Analytical Tools, Joints, And Constructions

Classification of Space Structures

Discuss about the Calculation of Statically Indeterminate Trusses.

Space structures also commonly referred to as space frames are rigid, light-weight, truss-like structures which are constructed from some interlocking struts in geometrical patterns (Leet, Uang, and Gilbert, 2011). The space structures can be used to span very large areas with only a few interior supports. Just like the trusses, the space structures are strong due to the inherent rigidity of the triangles and hence the flexing loads or the bending moments are normally transmitted as compression or tension loads along the length of the individual struts (Megson, 2005). Steel space structures which are among the most common space structures provide a great freedom of composition and expression as well as the possibilities to distribute the loads evenly along the individual rods and the external constraints. Due to these features, the steel space structures are among the most common structures and are used to produce complex symmetries which have lower structural weights compared to the other space structures (Trahair & Bradford, 2014). In this paper, we are going to discuss space structures in details where we’ll concentrate on different forms of the space structures, the analytical tools associated with the space structures, the types of joints associated with the space structures, the behavior of the space structures during strong winds and earthquakes, and ten different constructions which can be made using the space structures. This discussion will enhance our knowledge and understanding of space structures which will make us be more informed on how we can utilize the space structures to achieve the maximum benefits from them which will help to improve our lives in a way especially when the building and the constructions fields are involved.

The space structures occur in different forms where the forms or the types are classified mainly based on the curvature of the structures or the frames or based on the arrangements of their elements. While classifying the space structures according to the curvatures of the frames used, the main forms of the space structures are the space plane covers structures, the barrel vaults space structures, and the spherical domes space structures (Bhatt, 1999). The space plane covers or the spatial structures are the space structures which are composed of some planar substructures. These space structures behave like plates in the sense that in case there are some deflections, the deflections on the planes are normally channeled through the horizontal bars and all the shear forces are normally supported by the diagonals of these space structures (Koenders et al., 2015, pp.101-116). To the barrel vaults space structures, they usually have simple arcs on their cross-sections, and with these space structures, the designers don’t need to use some tetrahedral modules or pyramid meant to enhance their backing (Mohammadi, Abedi, and Taghizadieh, 2012, pp.203-218). Unlike the barrel vaults space structures, the spherical domes space structures require the designers to use some tetrahedral modules or some pyramids to enhance their backing management.

Analytical Tools for Space Structures

When classifying the space structures according to the arrangement of their elements, the main forms of the space structures available are the single layer grid space structures, the double layer grid space structures, and the triple layer grid space structures. In the single layer grid space structures, all the elements of the space structures are located on the surface which is to be approximated (Ataca and Ciraci, 2011, pp.13303-13311). The double layer grid space structures have the elements organized in two different layers parallel to each other and the layers are separated by a defined distance. Each of the layers in the double layer grid space structures forms a lattice of triangles, squares, or even hexagons where the nodes the projections of the nodes in the layers may overlap or be slightly displaced from each other. The diagonal bars of these space structures connect the nodes of the layers in different directions in the space. In the triple layer grid space structures, the elements are normally placed in three different parallel layers which are always linked by the diagonals. These space structures are always almost flat. There are some other forms of the space structures which are always not very common although they are always used but in rare cases. These forms of space structures include the hanging covers space structures, the pneumatic space structures, the pleated metallic space structures, among other forms. The designers should always make sure they choose the best of the space structures when designing different structures to make sure they establish strong and long-lasting structures which meet the required standards (Hibbler, 2012).

On top of the classification methods described above, the space structures may also be classified according to the trusses used to form them. Giving consideration to the trusses, we may have the roof trusses which are commonly used as parts of the industrial building frames and the bridge trusses which are normally used in the construction of bridges. These trusses are commonly referred to as the coplanar trusses which can further be divided into three basic categories namely the simple trusses, the compound trusses, and the complex trusses. The simple trusses are normally constructed by starting with basic triangular arrangements and then some other joints may be added to make the simple trusses take the shapes desired by the designers. Simple trusses do not consist of only triangles but may take some other shapes (Rebielak, 2014). Compound trusses are normally constructed by connecting two or more simple trusses together. Compound trusses are normally used to support the loads which act over a large span which may not be supported well or as required by the simple trusses (Dong, Zhao, and Xing, 2012, pp.224-239). It’s also good to mention that it’s easier to construct light compound trusses than constructing heavier simple trusses. Complex trusses are the trusses which can’t be considered either as simple trusses or compound trusses and can be used in supporting loads with either narrow or wide spans.

Types of Joints in Space Structures

As already discussed, there are many types and forms of space structures management. Some space structures are very simple while we have other very complex space structures. This great variation or the many differences which exist between different types of space structures make their study and analysis quite challenging. To enhance the study and the analysis of the space structures, various analytical tools have been established and these tools make the analysis of the space structures very simple. Some of the most common analytical tools include NASTRAN, ANSYS, ABAQUS, among other tools (Ghali, Neville, and Brown, 2009).

NASTRAN is a common analytical tool used in the analysis of space structures where it’s mainly used in dynamic modeling which generally deals with the mass, the stiffness, the damping, among other dynamic properties of the space structures. NASTRAN is mainly used to perform the following analysis; Guyan reduction or the static condensation, modal reduction, and the component mode synthesis (Padula, Robinson, & Eldred, 2012, p.1753). ANSYS analytical tool is a simulation tool and is used in the simulation of the space structures during the design process to make sure the designers will produce the space structures which meet the required specifications and which will fulfill all the demands of the customers (Moaveni, 2011). The ABAQUS analysis tool is the tool used in finite element analysis and in computer-aided engineering. This tool is very helpful in the analysis of the space structures as it helps in pre-processing or modeling of the space structures in the computers before they can be fabricated which makes their fabrication very easy (Hibbitt, Karlsson, and Sorensen, 2011). These three main analytical tools (NASTRAN, ANSYS, and ABAQUS) enhances the analysis of space structures in a great way.

There are many types of joints which are normally associated with the space structures. These joints are normally classified into three broad categories which are the rigid joints, the semi-rigid joints, and the pinned joints (Yu, Zha, and Ye, 2010, pp.442-451). Rigid joints are the joints which are capable of transmitting all the force at the end of one member to all the other members framing into those specific joints. The rigid joints which occur between structural members do not allow any relative motion between the members. The main advantage of the rigid joints is that they increase the overall resistance of the members to the external loads (Ohsaki, Kanno, & Tsuda, 2014, pp.945-956). These joints have many disadvantages the main disadvantage being that they require very high skilled-labor to be constructed successfully and work according to the expectations of the designers and the constructors. The rigid joints used to be very common and popular joints in the past and most designers and constructors preferred to use them in their construction work but due to their complexity in design they are being replaced by the semi-rigid joints which have become very popular in the last few decades (Li, Guo, and Cao, 2011, pp.974-983).

Conclusion

The semi-rigid joints are the joints which mainly consists of the ball points, the members, and the connection mechanisms which mainly use some bolts alone or at times use both bolts and nuts. There are many advantages associated with the semi-rigid joints and these many advantages make them better than the rigid joints and thus preferred by most designers and contractors. Some of the major advantages of the semi-rigid joints include their usability with a wide range of structures, easier to refabricate in the industries as they don’t need very high-skills to be refabricated, they can be easily used with tubular members, among other advantages (Ma et al., pp.13-28). The main disadvantage or drawback associated with the semi-rigid joints is that if the joints are not designed properly, they may become very complex and expensive than the other joints.

The last category of the joints is the pinned joints in which all the members are normally connected to these joints to help in eliminating the bending moments in some or in all the directions. The main design concept used in making of these joints is the pinning concept where the center lines of all the members are normally taken and then the members are either welded or bolted together making sure they are properly aligned to the joint thus making the joint to be pinned (Pisano, Fuschi, and De Domenico, 2012, pp.940-952).

As already discussed, we have different types or forms of space structures and their behaviors or responses to strong winds or earthquakes differ according to many factors where the main factor which determines the way they will behave is the strengths of the members and the types of the joints used to make them and their strengths and the strengths of the winds or the earthquakes (Holmes, 2015). We know that strong winds and the earthquakes are normally associated with very strong forces which act on the space structures making them behave differently depending on their strengths. When the forces exerted by the strong winds and or the earthquakes exceed the force which can be withstood by the members and the joints used in making of the space structures, the expected response of the space structures is deformation which may be slight deformation or extreme deformation depending on the strength of the forces exerted by the strong winds or the earthquakes. If the forces exerted by the strong winds or the earthquakes exceed the strengths of the space structures by far, the space structures may deform completely and collapse (Islam, Jameel, and Jumaat, 2011. pp.99-117). We may also have some cases of some strong winds or earthquakes failing to affect the space structures in any way. If the forces of the winds or the earthquakes don’t exceed the strengths of the space structures, the space structures will comfortably withstand these forces without any deformation or collapsing although they may be slightly weakened by the forces.

There are many constructions made using space structures. In this section, we shall consider ten of some of the most common constructions in the world which have been made using the space structures. The ten constructions which we shall give special considerations are the stadium Roof of Pala Armani Baskets in Italy, the third canopy structure in Chile, the Italian Lightness Freedom Canopy, the Kolkata Atmosphere Sky Bridge in India, the Carpenter’s church in Nigeria, KAIA – King Abdulaziz International Airport in Saudi Arabia, XXXL Lutz in Germany, Jura West Sign Gantry in Germany, the Lake Gardens Boat House in Malaysia, and the Power Plant Croix de Metz/Toul in France (MERO-TSK International GmbH & Co. KG, 2018). All these constructions have been made using very high and advanced technology which makes them be among the most prestigious structures in the world.

The stadium Roof of Pala Armani Baskets in Italy is a major construction made using space structures which was realized in MERO KK-System and was completed in 2017. It contains 18 different columns which have been arranged around the structure on the outer rim.

The Italian Lightness Freedom Canopy was completed in 2016 and has been designed with some superior architectural skills. It has a curved free-form structure realized as MERO KK system and some polycarbonate panels.

The third canopy structure of Penco-Lirquen Hospital in Chile is another major space structure which was completed in 2016 and was realized in MERO Ball Node System. The canopy is usually supported by two columns and some wall bearings.

The Kolkata Atmosphere Sky Bridge in India is another space structure of METRO-PLUS System. The structure forms the connection between two Indian skyscrapers with a height of about 130 meters. 

The carpenter’s church in Nigeria which was completed in 2016 is another major space structure which was realized using the KK system. The double-layer space frame of this structure is made of two steel grades and has some laser-welded tubes which cover the roof area.

KAIA – King Abdulaziz International Airport is a major space structure in Saudi Arabia which was completed in 2015 by the MERO-TSK International GmbH and CO.KG. The structure comprises of some triangular trusses which curve inwards and a slightly biconvex roof surface of approximately 35,000 square meters.

XXXL Lutz in Germany is another example of a construction made using the space structures. The structure has a roofing and some cladded façade elements on its two sides. It was realized in MERO Ball Node System and is supported by two columns and some wall bearings.

Jura West Sign Gantry in Germany is another major construction made using the space structures and was realized by MERO in 2014. The structure is one meter high and has a module of about 120 square meters and this module is usually covered with some perforated plates.

The Lake Gardens Boat House in Malaysia is another modern construction realized using the space structures. The structure is realized in MERO PLUS-System and its roof is constructed as a freeform geometry using single layer steel structure. It has a special glass print which on its glass and aluminum panels which prevents the shading effects.

The Power Plant Croix de Metz/Toul in France is another major construction which is realized using the space structures and was completed in 2013. The structure is mainly made of steel and it’s made in a way that the steel sheet sheathings are taken at particular mounting joints and its joints and lamellas are permanently mounted.

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