EVALUATION OF TWO ANALYTICAL PLASTIC DESIGN MODELS FOR LIGHT-FRAME SHEAR WALLS

摘要

The objective of this paper is to clarify the difference between two analytical models for plastic design of shear walls and evaluate their potential for hand calculation by comparing calculated load-bearing capacities of different wall configurations with the corresponding ones obtained by finite element analyses. The first analytical model is based on a true plastic lower bound concept, i.e. always fulfilling the conditions of equilibrium. The second model is based on the assumption that the full vertical shear capacity of the wall is utilized, considering that the vertical equilibrium is always fulfilled but disregarding that the horizontal equilibrium of the wall is not always satisfied. If the shear capacity of the stud-to-rail joints is sufficiently large, then the second model is also a true plastic lower bound method. The ratios between the calculated load-carrying capacities of the two analytical models are in the range between 1.00 - 1.24 with a mean value of 1.12 for the wall and load configurations studied. Results from FE simulations show that the first analytical method underestimates the load-carrying capacity by about 10 %, but that the method gives very stable capacity values relative to the FE simulations. It is further evident that there is a good agreement between the second analytical model and the results of the FE calculations at the mean level, but that this method has a considerably higher variation in the capacity values relative to the FE-simulations. Performed tests of different wall and load configurations show about 30 % higher measured capacities than calculated ones. The large deviations are mainly due to differences in the manufacturing of the specimens for the sheathing-to-framing joint tests and the specimens for the wall tests.