Beam-to-column joints

Although a few tests on bonded pultruded GFRP WF prohle beam-to-column joints have been reported (see Sanders et al., 1996), in practice mechanical fastening is the preferred means of connecting beams to columns in frame structures made of these materials. Consequently, only tests on bolted configurations of these joints are considered in this sub-section. 

Image of the test set-up for determining the moment versus rotation responses of beam-to-column joints using two simply supported half-beams connected to a vertically loaded stub column. 

Compared to traditional bare steel structures, SCC frames can achieve more effective beam-to-column connections through the contribution of the concrete slab in resisting bending moments under gravitatiOTial and lateral loads. Additionally, these structures comprising partial-strength partially restrained beam-to-column joints designed in such a way to exhibit ductile seismic... 

This section deals with the modeling of the panel zone region within the beam-to-column joints of SCC moment-resisting frames. This... 

The other type of bolted joint considered here is that used to connect beams to columns, and columns to colunm bases. These joints usually involve additional connection components in the form of angle or flat plate profiles. Consequently, both the bolts and the angles/plates participate in the transfer of bending moments and shear forces between beams and columns and between columns and their bases, and in the latter case also uplift forces. 

Tests on beam-to-column and column-to-base joints... 

Note The proposed model presented in the above sections considers only rigid beam-to-column coimections. Nevertheless, semirigid connections can be considered in the same numerical procedure by introducing special joint elements with prescribed constitutive behavior. 

Fire safety design requires the same kind of approach. We must develop the necessary scientific quantitative understanding of fire so as to be able to predict the level of a building s fire safety. Again, looking at structural engineering, we see the use of simple formulas for beams, columns, joints, reenforcing rods, etc., which permit quantitative evaluation of structural safety. The phenomena of fire also results in... 

Support beams must be installed level, or tray levelness may be difficult to achieve, especially in large columns. Support beams are often equipped with levelling screws (288) to permit on-site levelling. A less satisfactory alternative is using slotted holes on the joint of a major support beam to its shell support brackets. Slotted holes, however, are often used on the joints of minor beams to the major support beam to allow levelling. 

In Equation (3) the first and third terms in the square brackets, when multiplied by the factor outside these brackets, represent respectively the flexural and shear deflections of a simply supported beam carrying a point load at its centre. The second term accounts for the fact that the beam is not simply supported but forms part of a frame with identical semi-rigid beam-column Joints. Also in Equation (3), the a (= EI/GA) and p (= EI/K, where K is the joint stiffness) parameters reflect the contributions of shear deformation and semi-rigidity respectively to the mid-span deflection. Similar expressions have been derived for the beam translation under sway mode loading and the corresponding rotations at the beam-column joints and pinned bases. Some of these expressions have been used to predict the frame deformations described in the next section. 

Columns and beam-column joints are identified using an alphanumeric ID code that contains the location of the stmctural element in plan and elevation. The first number and letter of the ID stand for the axes intersection at which the structural element is located, whilst the number after the hyphen denotes the floor number. For instance, the ID lA-2 corresponds to the 2nd floor joint located at the intersection of axes 1 and A (refer to Fig. 11.3a). 

No evident damage occurred during the shaking table tests up to PGA = 0.05g. As expected, the first cracks were detected at the beam-column joints of the 2nd floor after the tests at PGA = O.lOg. The subsequent tests at PGA levels of 0.15g... 

Boundary conditions were kept the same as in the actual test of beam-column joints, Fig. 13.20 shows the bottom end of the column surface, constrained in the X and Y direction. The top end of the column is constrained in the X-direction and free in the Y-direction due to downward axial force (150 KN). Near the tip of the free end of the beam, the point is constrained in the y direction because the loading method is displacement control. All the specimens were modeled with eight-node quadrilateral isoparametric plane stress element CQ16M with embedded steel (Fig. 13.21). 

For the KFUPM beam-column joint specimen, the failure was initiated by joint shear failure. In order to model this in the DIANA environment using Dmcker-Prager yield criteria, non-associated plasticity theory had to be used, with = 10° and q> = A° in the joint and (p = 30° and q> = 10° in the beam and column zones. Such a partitioning of the structures into zones of biaxiality (0 = 10°) in contrast to uniaxiality (0 = 30°) appears to allow the use of the 2-parameter Dmcker-Prager model in finite element simulation of complex structures. 

A wide section of the guideline focuses on the brittle failure mechanisms. In particular, according to experiences gained from examining the performances of RC structures after seismic events, a wide section focuses on the most common brittle collapse mechanisms resulting from shear failure of partially confined beam-column joints (i.e. exterior or comer joints on the perimeter of the stmcture in some cases, where frames are only in one of the plan directions, they could be also interior). The typical joint failures observed in the L Aquila post earthquake are described and a local strengthening procedure by means of FRP, steel jacketing or CAM technique is discussed. 

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