Experimental Analysis of Space Trusses Using Spacers of Concrete with Steel Fiber and Sisal Fiber

Abstract

Space trusses are structural systems, generally made of tubes, used worldwide because of their advantages in covering long-span roofs. In addition to having a low cost, the truss weight is relatively reduced. The load capacity of these structures depends also on the strength of their node connection. Connections made with the superposition of flattened tube ends trespassed by one bolt are, generally, known as typical nodes. They are inexpensive but present eccentricities that reduce significantly the strength of such space trusses. To increase the truss load capacity, this research presents the results of an experimental program to reduce the eccentricities of the typical nodes. This reduction is done with a new type of spacer made of encapsulated concrete with steel fiber or sisal fiber. The experimental tests showed that the trusses with typical nodes collapsed under reduced load by local failure due to high distortions at the nodes. The trusses with encapsulated concrete spacer showed good results, with an increase in collapse load of 36% and failure by buckling bars.

Experimental and Numerical Analysis for Eccentricity Solution in Double-Layer Space Truss

“…Space trusses are made from different materials such as steel, aluminum, wood etc. Space trusses were copied from nature, the natural elements always seek to minimize stress and maximize strength in an efficient way, taking advantage of the load capacity of all members of the body [1, 3,4]. The natural shapes have exceptional stiffness and use minimum materials to obtain the maximum structural advantage.…”

“…There are high concentrations of stress on the nodal region, separation and slip between bars, which can sensibly increase the loss of bearing capacity with the emergence of bending moment [4,11,16]. (c) The eccentricities in the connections can cause increases of stress for a reduced nodal stiffness [17,18].…”

“…(d) Since the sudden collapse of the Hartford Coliseum space truss, in 1978, a large number of theoretical and experimental studies have been carried out. Several studies have shown the collapse was due to local instability of compressed members with eccentricity, resulting in flexocompression at the connection [4,11].…”

Numerical analysis of isolated end-flattened steel bars under compression in space trusses

“…A space truss type that has been frequently adopted as a structural system worldwide is the one composed of hollow circular cross-section bars, whose ends are previously flattened to promote coupling with other connection members by use of a single bolt. According to Bezerra et al and Silva et al [1][2], the simplicity and low cost of its construction method are relevant factors in its choice among engineering professionals. Despite this fact, some of its critical features, such as potential bending moments generated by eccentricity in the connections and the reduced rigidity due to the flattening process, must be duly considered in the designing process Silva et al [3].…”

“…Already in 2013, another failure of a coverage in space truss using bar with reduced section in conical shape occurred in the Shah Alam Stadium football at Malaysia. The report carried out by the Malaysia technical team concluded that the collapse was due to buckling of the bars and in conjunction with the rupture of several connections [2,[20][21]. In this context, the Fig.…”