Page 9 - Riem-Vol6_nº3

1. Introduction
The zone of overlapping of beams and columns in reinforced con-
crete buildings is called frame joint. This region has significant
bending stiffness but is subjected to large shear stresses. In build-
ing framed structures subjected to lateral loading, zero moment
can be considered at mid-height of columns and at mid-span of
beams. Thus, the subassemblage highlighted in Figure 1 can be
used to represent the interaction between beams and columns of
a frame.
This work studies the cases where the axes of beams intersect
the axes of framed columns. Two types of joints are studied: com-
plete joints, whose beams and columns have the same width, and
concentric joints, where the column width is larger than the beam
width, as illustrated in Figure 3. As shown in Figure 2 the joints are
grouped according to their geometry as interior cross-type joint, T-
Lateral exterior joint, T-Top exterior joint, and L-type joint.
The main objective of this study is to propose a simplified model
of ready numerical implementation that uses only bars and spring
elements to take into account the flexibility of joint regions which
may account for 20% of total structural lateral displacement, as
demonstrated by the experimental results of Shin and LaFave [1].
To simplify the development of the proposed approximate model
the restraining effects of slabs and transverse beams are neglect-
ed. This is a conservative assumption since it tends to decrease
joint stiffness. These additional effects will be the focus of the next
phases of the present research. Unfortunately very few experimen-
tal results are reported in the literature of joints including those
restraining members.
361 IBRACON Structures and Materials Journal • 2013 • vol. 6 • nº 3
S. J. P. J. MARQUES FILHO | B. HOROWITZ
Figure 1 – Bending moment diagram of a laterally loaded frame
Figure 2 – Building subjected to lateral loads with all different joint types:
(a) L-type joint; (b) T-Top exterior joint; (c) Cross-Type interior joint; (d) T-Lateral exterior joint