Influence of lateral load distributions on pushover analysis effectiveness

The effectiveness of two simple load distributions for pushover analysis recently proposed by the authors is investigated through a comparative study, involving static and dynamic analyses of seismic response of eccentrically braced frames. It is shown that in the upper floors only multimodal pushover procedures provide results close to the dynamic profile, while the proposed load patterns are always conservative in the lower floors. They over-estimate the seismic response less than the uniform distribution, representing a reliable alternative to the uniform or more sophisticated adaptive procedures proposed by seismic codes. © 2008 American Institute of Physics

Non linear and linearized combination coefficients for modal pushover analysis

Current design practice and seismic codes tend to assess seismic demand of buildings by Non linear Static Analysis (NSA), based on the evaluation of the pushover curve. Earlier non-linear static analysis procedure estimate the response peak value by evaluating the push-over curve adopting a distribution of invariant forces proportional to the fundamental vibration mode. In order to include the effect of higher modes several multimodal push-over analysis procedures were proposed in literature. In In the most famous of these, namely Modal Pushover Analysis (MPA), nodal response peak values are obtained by combination of "modal" responses by the traditional SRSS or CQC methods: the use of the CQC rule is mandatory for irregular plane frames or spatial structures possessing modes with close natural frequencies. In order to take into account the actual characteristics of modal oscillators, the use of pertinent cross correlation coefficients defined for non-linear systems is required. In this paper the accuracy of correlation coefficients for linear systems in predicting the statistical correlation of hysteretic oscillator responses is investigated by a parametric analysis by Monte Carlo simulation. Furthermore, new correlation coefficients, determined through a pertinent statistical linearization are introduced, and the results provided by the classical and the proposed approach for two illustrative irregular plane and spatial frame are compared with non-linear time history analysis results, showing the effectiveness of the new procedure

Influence of lateral load distribution in estimation of target displacement and capacity demand by pushover analysis

Two simplified adaptive load patterns for conservative estimation of seismic demand in 2D frames by pushover analysis are presented. The influence of load pattern in assessment of target displacement and distribution of demand along the height of the structure is investigated by comparing results of non linear history analysis, and non linear static analysis for eccentric braced frames. Numerical analyses show that the proposed load patterns provide safe estimation of the seismic response more accurately than load patterns proposed by seismic code

Combination coefficients for modal pushover analysis

Conventional non-linear static analysis estimates the response peak value by evaluating the pushover curve adopting a distribution of invariant forces proportional to the fundamental vibration mode. In order to include the effect of higher modes, multi-modal push-over analysis has been proposed in literature. Nodal response peak values are obtained by combination of “modal” responses usually by the traditional CQC method, requiring cross correlation coefficients defined for linear systems. In this paper, the accuracy of correlation coefficients for linear systems in predicting the statistical correlation of hysteretic oscillator responses is investigated by the Monte Carlo Simulation conducted on non-dimensional non-linear oscillators. Furthermore, new correlation coefficients determined through a pertinent statistical linearization are introduced, and the results provided by the classical and the proposed approach for two illustrative frames are compared with non-linear time history analysis, showing the effectiveness of the new procedure

Sul controllo del meccanismo di collasso di controventi eccentrici

The effectiveness of different non-linear static procedures, for the detection of the collapse mechanism of eccentric braced frames, is investigated. EBFs introduced into truss frame structures are considered. For such a typology of structures, plastic deformations are concen-trated in a single resistant element at each floor, greatly increasing the risk of the formation of soft storey mechanisms, even if the structure is designed according to the capacity design. The results of different non-linear static procedures are compared to those obtained by incremental dynamic non-linear analysis, considering a meaningful set of artificially generated stationary accelerograms, compatible with a target spectrum

The CA-SCR-9 Archaeofauna: Insights into Prey Choice, Seasonality, and Processing

Excavations of the Bonny Doon site (CA-SCR-9) in the Santa Cruz Mountains of northern Santa Cruz County, California by Hylkema in the late 1980s recovered a large and well-preserved faunal assemblage that spans the Early-Middle Period transition. With over 8,000 recorded specimens (from an estimated 12,000 total number of specimens [NSP]) and with demonstrated sampling to redundancy, the SCR-9 assemblage is one of the largest faunal samples in the region, and only the second published at this level of specificity. Analysis of the SCR-9 assemblage shows there were no changes in prey choice or handling in this part of the California central coast during the site’s occupation, while the presence of northern fur seals (Callorhinus ursinus) suggests the site’s inhabitants were connected to fur seal hunting at Año Nuevo Point. Notably, there is evidence for intensive exploitation of cervid bone nutrients, a pattern that may be typical of inland sites in this region