Keywords: structural engineering, semi-rigid connections, steel structures, parametric analysis, non-linear finite element modelling, semi-rigid behaviour, composite construction.

Traditionally, the steel portal frame design assumes that beam-to-column joints are rigid or pinned [1]. Despite this fact, it is largely recognised that the great majority of joints does not exhibit such idealised behaviour. These joints are called semi-rigid, and their design should be performed according to their actual structural behaviour. To estimate the actual behaviour of such joints, extensive research studies have been carried out over the past twenty five years [2,3,4], leading to code specifications that enable the calculation of the moment rotation characteristics of beam-to-column joints, as stated in the current version of Eurocode 3, [5].

Despite the substantial increase in structural design knowledge, the semi-rigid connection steel design is still facing resistance from structural engineers. This can be explained by the fact that few design standards allows their use and by the lack of detailed information of the advantages of the semi-rigid design philosophy.

This paper presents a parametric analysis performed on low-rise steel buildings taking into account all the steps necessary to a semi-rigid design. The analysis considered parameters like: beam-to-column connection stiffness and strength, structural system (steel or composite) and lateral frame stability.

The parametric analysis is based on the procedures proposed in the Eurocode 3, revised annex J, [5], for semi-rigid connection design. Based on this methodology a simple design model was proposed and implemented with the aid of the finite element program ANSYS, [6]. The model included geometrical and material non- linearities and considered the connections semi-rigid behaviour like the one associated with the connection depicted in Figure 96.1, avoiding the conventional approximations suggested in several current steel design standards. The results of these investigations are presented, discussed and compared to standard designs as means to access the economic potential and efficiency of the semi-rigid solutions. The best structural solution, which leads to the minimum steel consumption, for the investigated construction was a non-sway composite semi-rigid structure, Figure 96.2. The parametric analysis results confirmed the advantage of the use of these connections in low height residential buildings.

1

L.R.O. de Lima, P.C.G. daS Vellasco, S.A.L. de Andrade, L.A.P.S. da Silva, "Experimental and Mechanical Model for Predicting the Behaviour of Minor Axis Beam-to-Column Semi-Rigid Joints", International Journal of Mechanical Sciences, 44(6), 1047-1065, 2002. doi:10.1016/S0020-7403(02)00013-9

2

L.C.V. de Carvalho, S.A.L. de Andrade, P.C.G.S. Vellasco, "Experimental Analysis of Bolted Semi-Rigid Connections", Journal of Constructional Steel Research, 46, 1-3, 1998.

3

L.T.S. Ferreira, S.A.L. de Andrade, P.C.G. da S. Vellasco, "Composite Semi- Rigid Connections for Edge and Corner Columns", Eurosteel, Second European Conference on Steel Structures, Prague, 569-572, 1999.

4

L.A.P.S. Silva , L.R.O. de Lima, , P.C.G.S. Vellasco , S.A.L. de Andrade, "Experimental and Numerical Assessment of Beam-to-Column Joints Under Bending and Axial Force", 1st ICSCS � The First International Conference on Steel & Composite Structures, Pusan, Corea, 715-722, 2001.

5

Eurocode 3, PREN - 1993-1-8: 20, Part 1.8: "Design of Joints, Eurocode 3: Design of Steel Structures", CEN, European Com. for Standardisation, 2000.

6

ANSYS, "Basic Analysis Procedures Guide", 3rd Edition, Release 5.5. September 1998.

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