In this paper, four specimens with different thickness of top and seat angle with double web angle connections are experimentally tested and numerically modeled. The model has been solved by means of Abaqus® finite element package. Moment rotation curves obtained from the experiments are compared with those obtained from FE models and good agreement is observed. These results validate this numerical modeling in order to use it in future studies on angle connections.

En este artículo se presenta el ensayo experimental y el modelo numérico de cuatro uniones de estructura metálica realizadas con casquillos angulares de diferentes espesores. El problema se ha resuelto mediante el programa comercial de elementos finitos Abaqus®. Las curvas experimentales momento-rotación obtenidas concuerdan razonablemente con los resultados de los modelos propuestos, de modo que con este trabajo se ha establecido una base numérica sólida para estudios posteriores.

In conventional analysis and design procedures of steel frames, beam to column connections are assumed to be either perfectly rigid or ideally pinned. Thus, the true behaviour of joints is disregarded. Moreover, semi-rigid connections have highly nonlinear behaviour so they are seldom used by designers. On the other hand semi-rigidity introduces economic and structural benefits. In order to change this trend and to establish a rational design procedure, it is very important to determinate the moment-rotation characteristics of the semi-rigid connections

One of the typologies of semi-rigid connections is the top and seat angle connection with double web angle. The semi-rigidity concept reduces the cost and provides structural profits for both steel and composite construction.

The general Eurocode approach is based on a mechanical model that simulates the connection by a series of different components which are represented by elastic springs. These springs are characterized by a specific stiffness and strength. The appropriate coupling of these springs in parallel and series provides the global stiffness of the connection. The procedure for calculating the connection flexural resistance by means of the component methodology can result in a complex task. This complexity is due to the need of taking into account the interaction between the various bolt rows and the existence of a large number of components involved in the analysis.

Annex J of Eurocode3 has emphasized the need to account for the influence of the sources of deformation due to the column (the panel zone components), which can be up to 20 % of the joint deformability. But the main sources of deformation in angle connections are the angles in bending (up to 70 % of the joint deformability)

Since Eurocode 3 does not consider specifically this type of joint, it is substantial to improve the knowledge about angle connections in order to make easy its incorporation to European steel design

On the other hand, the Finite Element Method (FEM) has become a powerful tool for investigating the effect of all relevant parameters related to the connection behavior. Nowadays, with the evolution of computers in solving structural problems, investigation is usually related to parametric analyses on FE models to investigate the behavior of bolted connections. Considering that existing tests in literature are related to American profiles and preloaded joints

The test set up consist of a pair of beams connected to a central stub column via top and seat angles bolted to the flanges of the beam and column and web angles bolted to the beam web and column flanges. For practical reasons, the tests have been developed on reversed configurations and the load has been applied on the column, as shown in

The test set up consist of a HEA 300 column profile with IPE 240 beams attached by means of L100x8 web angles and top and seat angles: L120x90x12 (Test 1), L120x90x9 (Test 2), L120x90x8 (Test 3) and L120x90x10 (Test 4)

The tests were carried out by means of

The moment-rotation response has been computed by using the force-displacement data obtained from the tests. The force-displacement response of the connection is converted to the moment-rotation response using simple relations:

Where

3D finite element models of the tests have been performed. The Test 1 3D FE model of top and seat angle connection with double web angles is shown in

Additionally, the washers were modelled as isolated elements, so that appropriate interactions between components may be developed, as they have been estimated to be relevant. Finally, the model was improved by introducing the actual length of the beam.

The experimental data describing the stress-strain top angle response is taken from coupon test for Test 1 and Test 2, and translated to true-stress-strain cuatrilineal relations to be used in the

The load was simulated by an imposed displacement on the column. To achieve the “snug tight” condition, little pretension has been applied to the bolts by means of a thermal load applied to the bolt shank. The thermal decrease is calculated by means of the next equation, which disregards the head bolt deformation:

Where _{p}_{sh}

Where

Where _{bh}_{sh}

Considering that the unthreaded part of the bolt is generally larger than the threaded part, the nominal value of the bolt shank diameter will be introduced in Equations 5 and 6 in accordance with the bolt geometry related to the FE model.

As it is known, two plastic hinges are developed in the tension angle. The first one is located at the toe of the fillet in the angle attached to the tension flange of the beam. The second one is located in the vicinity of the bolt line, on the leg of the angle attached to the column.

As it can be verified (

By comparing Test 3 (top angle thickness: 8 mm) and Test 1 (top angle thickness: 12 mm), both the strength and stiffness have increased by 100%.

These results show the possibilities of this connection in order to match with different design requirements, just varying the angle thickness (

3D FE models of top and seat angle connections with double web angles made up of rolled European profiles have been developed.

In order to ease the experimental lack in literature and to obtain empirical data for comparing with numerical results, four specimens on non-preloaded European connections have been tested.

The effectiveness of this modelling approach has been proved by comparison with experimental data, so this numerical approximation could be successfully used in future parametric studies.

The increase in stiffness and resistance, due to angle thickness growth, has shown the possibilities of angle connections in European steel construction as an alternative to other semi-rigid typologies.