Gusset plate connections under monotonic and cyclic loading

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992 Can. J. Civ. Eng. Vol. 32, 2005 Fig. 16. Buckling of brace member (BBT). member assembly for different load limiting mechanisms for a 6 mm gusset plate (GP1). Figure 18a presents the behaviour when the load in tension is limited by yielding of the gusset plate and the load in compression is limited by buckling of the gusset plate (YGT/BGC). Figure 18b presents the behaviour when the limiting condition in tension is yielding of the gusset plate and the limiting condition in compression is buckling of the brace member (YGT/BBC). A comparison of Fig. 18a with Fig. 18b shows that buckling of the brace member as a limiting condition in the compression range results in a greater reduction in compression capacity under cyclic loading and a deterioration of the load carrying capacity in tension. The same observation is made when Fig. 18b is compared with Fig. 18c, which represents the behaviour when the limiting condition in tension is yielding of the brace member and the limiting condition in compression is buckling of the gusset plate (YBT/BGC). The behaviour of the assembly when the limiting mechanism in tension is yielding of the brace member and the limiting mechanism in compression is buckling of the brace member (YBT/BBC) is illustrated in Fig. 17a. As observed in Figs. 17a and 18b, the reduction in tension stiffness at zero load can be quite significant when the compression capacity is limited by buckling of the bracing member (BBC). This reduction in tension stiffness was not observed when buckling of the gusset plate limited the compression capacity. A comparison of the cumulative energy absorbed for the various gusset plate GP1 subassemblies is presented in Fig. 19. The figure shows clearly that the specimens for which the load limiting mechanism in compression is buckling of the gusset plate (GP1B1 and GP1B3) absorbed significantly more energy (about twice) than the specimens for which the load limiting mechanism in compression is buckling of the bracing member (GP1B2 and GP1B4). Whereas, the load limiting mechanism in tension does not have a significant effect on the energy absorption capacity (the tension capacity of GP1B1 is limited by yielding of the bracing member, whereas the tension capacity of GP1B3 is limited by yielding of the gusset plate and both (GP1B1 and GP1B3) dissipated about the same amount of energy). Effect of gusset plate thickness Three different gusset plate thicknesses were investigated, namely 6, 9, and 12 mm. Figure 20 shows the difference in behaviour for gusset plate – brace member subassemblies proportioned to have a tension capacity limited by yielding of the gusset plate and a compression capacity limited by buckling of the gusset plate. Although all plate thicknesses display good behaviour, the thicker gusset plate shows fuller hysteresis loops. Finally, dashed lines are shown in Fig. 20, corresponding to the monotonic loading curves for each of the specimens. In all cases, the monotonic loading curves were found to represent well an envelope of the hysteresis under cyclic loading. Summary and conclusions Finite element models of gusset plates were developed to predict results of tests on gusset plates under monotonic compression, tension, and cyclic loading. The models were validated for monotonic tension and compression and cyclic loading. The effects of material inelasticity, large displacements, and initial imperfections were included in the models. The load resistance of the gusset plates in tension was predicted closely by the numerical models. The models were also seen to predict well the buckling load as well as the subsequent decay of the compressive post-buckling load resistance under cyclic loading. © 2005 NRC Canada
Walbridge et al. 993 Fig. 17. Effect of load sequence on cyclic response of gusset plate – brace member assembly: (a) LS1, (b) LS2, and (c) LS3. A parametric study of the cyclic behaviour of gusset plate – brace member subassemblies was performed. A series of parameters were investigated, which included: the effect of gusset plate – brace member interaction, the effect of loading sequence and the effect of gusset plate thickness. The weak gusset plate – strong brace member concept was examined in the study as an alternative design approach for concentrically braced frames. The following conclusions can be drawn from this parametric study: Load sequence does not have a significant effect on the cyclic behaviour of the gusset plate – brace member subassemblies. Limiting the capacity in tension either by brace member yielding or by gusset plate yielding does not result in a sig- Fig. 18. Effect of load limiting mechanism on hysteresis curves: (a) tension and compression – gusset (YGT/BGC), (b) tension – gusset/compression – brace (YGT/BBC), (c) tension – brace/ compression – gusset (YBT/BGC). nificant change in behaviour over the displacement range studied. Buckling of the gusset plate results in only a small reduction in capacity and a very stable cyclic behaviour. Failure in compression by buckling of the gusset plate rather than buckling of the brace member results in better energy absorption characteristics. Although all plate thickness display good behaviour, the thicker gusset plate shows fuller hysteresis loops Monotonic load versus displacement plots tended to delineate the cyclic load versus displacement hysteresis envelope. © 2005 NRC Canada
Page 1 and 2: Introduction Gusset plate connectio
Page 3 and 4: Walbridge et al. 983 Table 1. Parti
Page 5 and 6: Walbridge et al. 985 Fig. 2. Gusset
Page 7 and 8: Walbridge et al. 987 Fig. 9. Spring
Page 9 and 10: Walbridge et al. 989 Fig. 13. Finit
Page 11: Walbridge et al. 991 Table 4. Gusse
Page 15: Walbridge et al. 995 neering, Unive

Gusset plate connections under monotonic and cyclic loading

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