Seismic Damage Observations of Precast Hollow-Core Floors From Two Full-Scale Super-Assembly Tests.

Serious concerns about the life safety risk of hollow-core floors during earthquakes were raised following the collapse of hollow-core units during the 1994 Northridge earthquake and in subsequent laboratory tests. To enhance the understanding of the seismic performance of existing hollow-core floors, a substantial experimental programme of two large-scale super-assembly tests with hollow-core floors was carried out. Each test specimen consisted of a two-bay by one-bay concrete frame with full-scale hollow-core floors, which were constructed using typical 1980s floor detailing. The specimens were loaded with a simulated earthquake record applied quasi-statically. This paper discusses the progression of hollow-core floor damage observed in both super-assembly experiments. The main findings include the early onset of cracks in the unreinforced webs of the hollow-core units at 0.5% interstorey drift. The tests also demonstrated the detrimental effect of web cracking on the gravity load-carrying capacity of hollowcore floors. Additionally, hollow-core units that are seated at intermediate columns (so-called ‘beta units’) were found to get damaged more heavily than those supported away from the columns. Moreover, several transverse cracks were observed in the floor soffit away from the support and beyond the provided seating retrofits. Lastly, the extent of floor damage was found to be sensitive to the ground motion, with pulse-type motions (pushing the structure in one direction) tending to cause more severe floor damage than far-field motions with multiple cycles. The paper also outlines key challenges and recommendations for web crack inspections

Load-Path and Stiffness Degradation of Floor Diaphragms in Reinforced Concrete Buildings Subjected to Lateral Loading - Part I, Experimental Observations.

An experimental investigation into the degradation of load-paths in damaged diaphragms was conducted to provide answers to the New Zealand structural engineering community following concerns that strut-and-tie load-paths could not cross wide cracks that develop around the floor perimeter during earthquake loading demands. A full-scale super-assembly concrete moment frame specimen with a hollow-core flooring system installed was subjected to realistic drift deformations to induce damage in the floor, followed by in-plane shear deformation demands to assess the ability of the diaphragm to transfer load between frames at different floor damage levels. It was found that compression struts could form across much wider cracks in floors than previously anticipated. This was due to contact compressive stresses forming via loose aggregate that lodged within rugged sinusoidal wide floor cracks. Additionally, it was found that diaphragm compression struts can only transfer to the primary lateral load resisting frame through beam plastic hinges acting in minor axis shear following gaps opening between the floor and columns at moderate drift demands. Smooth floor to column interfaces did not provide the same residual rubble aggregate binding compressive load path observed in cracks within the floor. The primary driver of diaphragm shear stiffness degradation was found to be torsional softening of the perimeter beams of the floor. This was caused by simultaneous bi-directional demands applied to longitudinal beam bars and a phenomenon known as the bowstring effect applying large torsional demands through the beam-floor continuity reinforcement. The diaphragm strength and rate of shear stiffness degradation was found to be highly reliant on earthquake directionality. A set of generalised equations was developed to describe the rate of diaphragm shear stiffness degradation with respect to magnitude and directionality of drift demands. Part I of II in this journal series details the full-scale super-assembly experiment conducted on a floor diaphragm at different damage states and the observed behaviour during testing

Ultrahigh ionic exclusion through carbon nanomembranes

The collective “single‐file” motion of water molecules through natural and artificial nanoconduits inspires the development of high‐performance membranes for water separation. However, a material that contains a large number of pores combining rapid water flow with superior ion rejection is still highly desirable. Here, a 1.2 nm thick carbon nanomembrane (CNM) made from cross‐linking of terphenylthiol (TPT) self‐assembled monolayers is reported to possess these properties. Utilizing their extremely high pore density of 1 sub‐nm channel nm−2, TPT CNMs let water molecules rapidly pass, while the translocation of ions, including protons, is efficiently hindered. Their membrane resistance reaches ≈104 Ω cm2 in 1 m Cl− solutions, comparable to lipid bilayers of a cell membrane. Consequently, a single CNM channel yields an ≈108 higher resistance than pores in lipid membrane channels and carbon nanotubes. The ultrahigh ionic exclusion by CNMs is likely dominated by a steric hindrance mechanism, coupled with electrostatic repulsion and entrance effects. The operation of TPT CNM membrane composites in forward osmosis is also demonstrated. These observations highlight the potential of utilizing CNMs for water purification and opens up a simple avenue to creating 2D membranes through molecular self‐assembly for highly selective and fast separations

Comparison of different stomatal conductance algorithms for ozone flux modelling

A multiplicative and a semi-mechanistic, BWB-type [Ball, J.T., Woodrow, I.E., Berry, J.A., 1987. A model predicting stomatalconductance and its contribution to the control of photosynthesis under different environmental conditions. In: Biggens, J. (Ed.), Progress in Photosynthesis Research, vol. IV. Martinus Nijhoff, Dordrecht, pp. 221–224.] algorithm for calculating stomatalconductance (gs) at the leaf level have been parameterised for two crop and two tree species to test their use in regional scale ozone deposition modelling. The algorithms were tested against measured, site-specific data for durum wheat, grapevine, beech and birch of different European provenances. A direct comparison of both algorithms showed a similar performance in predicting hourly means and daily time-courses of gs, whereas the multiplicative algorithm outperformed the BWB-type algorithm in modelling seasonal time-courses due to the inclusion of a phenology function. The re-parameterisation of the algorithms for local conditions in order to validate ozone deposition modelling on a European scale reveals the higher input requirements of the BWB-type algorithm as compared to the multiplicative algorithm because of the need of the former to model net photosynthesis (An

Investigation of relationship between functional level, cognitive status, emotional status, and quality of life in elderly people living at home

Purpose: This study was planned to investigate the relationship between cognitive status, depression level, functional status, and quality of life in elderly people living at home. Methods: One hundred thirteen voluntary elderly subjects living at home participated in this study. Demographics of the participants were recorded. The data was obtained by face-to-face interviews. The questionnaire covered socio-demographic characteristics, administration of the Standardized Mini Mental Test (SMMT), Geriatric Depression Scale-Short Form (GDS-SF), Lawton Instrumental Activities of Daily Living (IADL) Scale, Katz Index of Independence in Activities of Daily Living (ADL) and World Health Organization Quality of Life Instrument-Older Adults Module (WHOQOL-OLD). Results: The mean age was 71.4±5.9 years. Ninety two percent of the elderly subjects were independent in ADL, whereas 83.2% were independent in IADL. The subjects had a high cognitive level (8.63±1.57) and low depression status (4.09±3.17). Also, there was a positive correlation between ADL, IADL, cognitive status, and quality of life (p<0.05) and a negative correlation between ADL, IADL, cognitive status, and depression status (p<0.05). Conclusion: This study indicated importance of the relationship between functional level, cognitive status, depression level, and quality of life in the rehabilitation of elderly people living at home

First detection of Borrelia burgdorferi-antibodies in free-living birds of prey from Eastern Westphalia, Germany

Borrelia (B.) burgdorferi sensu lato, the causative agent of Lyme disease, is the most important arthropodborne zoonosis-pathogen in the Northern hemisphere. Besides small mammals, birds, primarily Passeriformes and sea birds, play an important role in the transmission, distribution and maintenance of this disease. Previous studies on birds have focused mainly on the detection of Borrelia-infected ticks. However, the presence or absence of an infected tick cannot be taken as an indicator of the infective status of the avian host; to date this area of research has not been explored. In this study, serological analyses of blood collected from free-living birds of prey (n = 29) at the rehabilitation centre in Eastern Westphalia, Germany, highlights that birds of prey are also susceptible to B. burgdorferi and react immunologically to an infection. Increased antibody-levels could be found by using a modified Indirect Immunofl uorescent-testing in two common buzzards, Buteo buteo, and two eagle owls, Bubo bubo. Further research regarding the serological diagnostics of B. burgdorferi within the avian host is required. In the future, it should be taken into account that birds of prey can be reservoirs for B. burgdorferi, as well as carriers of infected ticks; although at present their epidemiological importance is still to be confirmed