SEISMIC BEHAVIOUR OF PERIMETER AND SPATIAL STEEL FRAMES

The present study deals with the seismic performance of partial perimeter and spatial moment resisting frames (MRFs) for low-to-medium rise buildings. It seeks to establish perimeter configuration systems and hence the lack of redundancy can detrimentally affect the seismic response of framed buildings. The paper tackles this key issue by com-paring the performance of a set of perimeter and spatial MRFs, which were “consistently designed”. The starting point is the set of low-(three-storey) and medium-rise (nine-storey) perimeter frames designed within the SAC Steel Project for the Los Angeles, Seattle and Boston seismic zones. Extensive design analyses (static and multi-modal) of the perimeter frame buildings and consistent design of spatial frame systems, as an alternative to the perimeter configuration, were conducted within this analytical study. The objectives of the consistent design are two-fold, i.e. obtaining fundamental periods similar to those of the perimeter frames, i.e. same lateral stiffness under design horizon-tal loads, and supplying similar yield strength. The seismic behaviour of perimeter and spatial configuration structures was evaluated by means of push-over non-linear static analyses and inelastic dynamic analyses (non linear time histories). Comparisons be-tween analysis results were developed in a well defined framework since a clear scheme to define and evaluate relevant limit states is suggested. The failure modes, either local or global, were computed and correlated to design choices, particularly those concerning the strength requirements (column overstrength factors) and stiffness (elastic stability indexes). The inelastic response exhibited by the sample MRFs under severe ground motions was assessed in a detailed fashion. Conclusions are drawn in terms of local and global performance, namely global and inter-storey drifts, beam and column plas-tic rotations, hysteretic energy. The finding is that the seismic response of perimeter and spatial MRFs is fairly similar. Therefore, an equivalent behaviour between the two configurations can be obtained if the design is “consistent”.     

EVALUATION OF THE APPLICABILITY OF CONVENTIONAL METHODS FOR THE CHEMICAL CHARACTERIZATION OF WATERLOGGED ARCHAEOLOGICAL WOOD

A series of 112 waterlogged archaeological wood samples of different provenances, wood species, burial times and states of preservation were analysed with the aim of assessing the validity (in terms of limits and reliability) of procedures conventionally used in the pulp and paper industry, to evaluate the state of preservation of decayed wood. In particular, the extent of any damage wrought on decayed wood tissue by the repetitive cycles that characterize these procedures was evaluated as a function of the degradation of the samples. The results indicated that standard methodologies give reliable measurements regardless of the extent of wood decay. However, it is essential to compare these data with those of non‐decayed wood that has been measured using the same procedures to take account of the errors that are inherent in these methodologies and that affect measurements.     

Developing a Synthetic Index of Land Vulnerability to Drought and Desertification

This paper develops an index of the vulnerability of land to drought and desertification (LVI) for Italy. The index takes into account changes in climate, land use, vegetation cover, soil properties, and population during the period 1990–2000. The LVI was built up through a multivariate approach aimed at assessing the importance of the various indicators included in the synthetic index. Increasing land vulnerability was observed during this time, especially in dry areas of the southern regions. This is interpreted as a consequence of land management practices, agricultural intensification, population pressure, and bio-physical degradation. The LVI can be used in an integrated, decision-support system to evaluate the impact of mitigation policies in rural environments.