Melting of polymer blends in single-screw extrusion : an experimental study

Melting is a major step in plasticating single screw extrusion, but most of the existing phenomenological know how was gathered by performing Maddock-type experiments with homopolymers. Given the current widespread industrial use of polymer blends, it is worth determining whether the same mechanisms and mathematical models apply, or whether different sequences develop. This work reports the results of Maddock-type experiments using a PA6/PP blend, both in its immiscible and compatibilized varieties. A melting mechanism combining the features of the classical Tadmor mechanism and of the dispersed melting mechanism, also previously reported in the literature, was observed.The authors are grateful to Portuguese Fundacao para a Ciencia e Tecnologia for supporting this work under grant SFRH/BD/19997/2004 and to DSM, the Netherlands, for supplying PA6

Effect of Plan Configuration on Seismic Performance of Single-Story, Wood-Frame Dwellings

A numerical investigation is presented on effects of plan configuration on seismic responses of single-story, wood-frame dwellings. 151 models were developed using observations of 412 dwellings of rectangular, L, T, U, and Z-shapes in Oregon. A nonlinear, time-history program, Seismic Analysis Package for Wood-frame Structures, was the analysis platform. Models were analyzed for 10 pairs of biaxial ground motions (spectral accelerations from 0.1 g to 2.0 g) for Seattle. Configuration comparisons were made using median shear wall maximum drifts and occurrences of maximum drifts exceeding the 3% collapse prevention limit. Plan configuration significantly affects performance through building mass, lateral stiffnesses, and eccentricities. Irregular configuration tends to induce eccentricity and cause one wall to exceed the allowable drift limit, and fail, earlier than others. Square-like buildings usually perform better than long, thin rectangles. Classification of single-story dwellings based on shape parameters, including size and overall aspect ratio, plan shape, and percent cutoff area, can organize a building population into groups having similar performance and be a basis for including plan configuration in rapid visual screening.Keywords: Configuration, Seismic analysis, Wood structure

A procedure for rapid visual screening for seismic safety of wood-frame dwellings with plan irregularity

This paper highlights the development of a rapid visual screening (RVS) tool to quickly identify, inventory, and rank residential buildings that are potentially seismically hazardous, focusing on single-family, wood-frame dwellings with plan irregularity. The SAPWood software was used to perform a series of nonlinear time-history analyses for 480 representative models, covering different combinations of plan shapes, numbers of floors, base-rectangular areas, shape aspect ratio, area percentage cutoffs, window and door openings, and garage doors. The evolutionary parameter hysteresis model was used to represent the load–displacement relationship of structural panel-sheathed shear walls and a 10 parameter CUREE hysteresis model for gypsum wallboard sheathed walls. Ten pairs of ground motion time histories were used and scaled to four levels of spectral acceleration at 0.167, 0.5, 1.0, and 1.5g. An average seismic performance grade for each model was generated based on the predicted maximum shear wall drifts. Five seismic performance grades: 4, 3, 2, 1, and 0, are associated with the 1% immediate occupancy drift limit, 2% life safety limit, 3% collapse prevention limit, 10% drift, and exceeding 10% drift, respectively. The obtained average seismic performance grades were used to develop a new RVS tool that is applicable for checking the seismic performance of either existing or newly designed single-family, wood-frame dwellings. It examines the adequacy of the structure’s exterior shear walls to resist lateral forces resulting from ground motions, including torsional forces induced from plan irregularity

Multi-hazard Earthquake-Tsunami Structural Fragility Assessment Framework

A probabilistic multi-hazard earthquake-tsunami fragility assessment framework is presented, which accounts for the effect of accumulated damage on the structure due to earthquake loading on its subsequent tsunami response. The fragility assessment framework involves simulating structural response using advanced three dimensional (3D) nonlinear finite-element structural model subjected to sequential earthquake-tsunami loading at multiple seismic and tsunami intensity levels, using back to back nonlinear response history analyses (NRHA) and nonlinear static pushover (NSP) analyses. A modern earthquake-tsunami code designed four story reinforced concrete (RC) special moment resisting frame (SMRF) building is used as an application example to illustrate the proposed framework. Results indicate that the effect of accumulated damage due to earthquake loading is more pronounced in reducing the stiffness of the structure compared to the reduction in structural capacity. Moreover, the tsunami structural capacity required to achieve a given probability of damage exceedance decreases with increasing seismic intensity, especially at lower damage states.Funding for this study was provided as part of the cooperative agreement 70NANB15H044 between the National Institute of Standards and Technology (NIST) and Colorado State University through a subaward to Oregon State University. The content expressed in this paper are the views of the authors and do not necessarily represent the opinions or views of NIST or the US Department of Commerce

Effect of Plan Configuration on Seismic Performance of Single-Story Wood-Frame Dwellings

A numerical investigation is presented on effects of plan configuration on seismic responses of single-story, wood-frame dwellings. 151 models were developed using observations of 412 dwellings of rectangular, L, T, U, and Z-shapes in Oregon. A nonlinear, time-history program, Seismic Analysis Package for Wood-frame Structures, was the analysis platform. Models were analyzed for 10 pairs of biaxial ground motions (spectral accelerations from 0.1 g to 2.0 g) for Seattle. Configuration comparisons were made using median shear wall maximum drifts and occurrences of maximum drifts exceeding the 3% collapse prevention limit. Plan configuration significantly affects performance through building mass, lateral stiffnesses, and eccentricities. Irregular configuration tends to induce eccentricity and cause one wall to exceed the allowable drift limit, and fail, earlier than others. Square-like buildings usually perform better than long, thin rectangles. Classification of single-story dwellings based on shape parameters, including size and overall aspect ratio, plan shape, and percent cutoff area, can organize a building population into groups having similar performance and be a basis for including plan configuration in rapid visual screening

Implementation of Plan Irregularity Rapid Visual Screening Tool for Wood-Frame, Single-Family Dwellings

A plan irregularity rapid visual screening method for seismic performance assessment of wood-frame, single-family dwellings is presented. Results from 124 samples were compared with (i) building-specific, non-linear time-history analysis, and (ii) FEMA 154 and ASCE 31 Tier 1. Verification using two houses damaged in the 1994 Northridge Earthquake is presented. The method includes effects of shape, torsional forces from eccentricity, and is based on conservative values of shear wall capacities and a non-linear time-history analysis. The method is relatively more conservative than ASCE 31 Tier 1 and FEMA 154, and provides conservative but reasonable predictions of actual earthquake damage.Keywords: wood structures, rapid visual screening, seismic analysi

Cinema-going trajectories in the digital age

The activity of cinema-going constantly evolves and gradually integrates the use of digital data and platforms to become more engaging for the audiences. Combining methods from the fields of Human Computer Interaction and Film Studies, we conducted two workshops seeking to understand cinema audiences’ digital practices and explore how the contemporary cinema-going experience is shaped in the digital age. Our findings suggest that going to the movies constitutes a trajectory during which cinemagoers interact with multiple digital platforms. At the same time, depending on their choices, they construct unique digital identities that represent a set of online behaviours and rituals that cinemagoers adopt before, while and after cinema-going. To inform the design of new, engaging cinemagoing experiences, this research establishes a preliminary map of contemporary cinema-going including digital data and platforms. We then discuss how audiences perceive the potential improvement of the experience and how that would lead to the construction of digital identities

Seismic assessment of a heavy-timber frame structure with ring-doweled moment-resisting connections

The performance of heavy-timber structures in earthquakes depends strongly on the inelastic behavior of the mechanical connections. Nevertheless, the nonlinear behavior of timber structures is only considered in the design phase indirectly through the use of an R-factor or a q-factor, which reduces the seismic elastic response spectrum. To improve the estimation of this, the seismic performance of a three-story building designed with ring-doweled moment resisting connections is analyzed here. Connections and members were designed to fulfill the seismic detailing requirements present in Eurocode 5 and Eurocode 8 for high ductility class structures. The performance of the structure is evaluated through a probabilistic approach, which accounts for uncertainties in mechanical properties of members and connections. Nonlinear static analyses and multi-record incremental dynamic analyses were performed to characterize the q-factor and develop fragility curves for different damage levels. The results indicate that the detailing requirements of Eurocode 5 and Eurocode 8 are sufficient to achieve the required performance, even though they also indicate that these requirements may be optimized to achieve more cost-effective connections and members. From the obtained fragility curves, it was verified that neglecting modeling uncertainties may lead to overestimation of the collapse capacity