Investigation of Grouted Dowel Connection for Precast Concrete Wall Construction

The grouted dowel connection is a simple and cost-effective connection used in many precast concrete structural systems. The required dowel length is currently designed as a regular bar in reinforced concrete, which underestimates the bond strength, thus resulting in excessive connection lengths. Furthermore, precast wall construction continues throughout cold weather, where in-situ heating of the grout used in the grouted dowel connections is usually conducted for short periods of time. Hence, early-age exposure to subfreezing conditions may affect the quality of the grout and subsequently the bond strength of the connection, which can compromise structural integrity. In this thesis, full-scale pullout tests were performed and their results were compared with relevant data in the open literature in order to develop a reliable design equation for predicting the required dowel development length. The equation was found to produce results three times smaller than that determined by the ACI 318-14 code, while being desirably 10% more conservative than equations proposed in previous research. The effect of subfreezing exposure on the bond strength of the connection, along with the mechanical properties, hydration process and pore size distribution of the grout were also examined. Grout specimens were initially cured at ambient temperature (23 ± 1°C) for one day and then placed inside an environmental chamber at -10°C. The compressive strength of the grout was monitored at additional temperatures of 1°C and -20°C. It was found that early-age subfreezing curing temperatures reduced the compressive strength of the grout, leading to increased dowel embedment length to achieve bar fracture. The bond strength of the connection remained proportional to the square root of compressive strength, even when subsequent to early-age subfreezing exposure

MAT-719: INVESTIGATION OF GROUTED PRECAST CONCRETE WALL CONNECTIONS AT SUBFREEZING CONDITIONS

The effect of exposing grouted precast wall connections to subfreezing curing temperatures at early-age was explored in this study. In cold weather construction, heating of the surrounding environment of grouted precast wall connections is usually conducted for short periods of time. Hence, subfreezing conditions can affect the strength of the grout and the bond strength of the connection, which can ultimately compromise the integrity of the structure. In this study, grout specimens typical of that used in precast wall construction were cured at ambient conditions for one day, and then placed in an environmental chamber at subfreezing temperatures (-10°C and -20°C). The compressive strength development of the grout was monitored, and the bond strength of grouted connections cured at cold temperature were quantified and compared to that of specimens cured at ambient temperature. The bond was investigated on 25M deformed steel bars, which is the typical size used in precast concrete wall grouted connections. Test results indicate a reduction in grout strength and the need for a longer embedment length when early-age curing is conducted at subfreezing conditions

MAT-723: BOND BEHAVIOUR OF GROUTED CONNECTIONS UNDER MONOTONIC TENSILE LOADS

Grouted bar-in-conduit connections are versatile connections widely used in the precast concrete construction. In precast load bearing wall structures, two vertical wall panels are connected by a reinforcing bar, which is projected from one panel and grouted into a sleeve placed in the other. The main function of the ties is to resist tension induced by in-plane and out-of-plane straining actions and to provide ductility to the wall assembly through the yielding of the reinforcement. Limited information is currently available on the behaviour of such connections. This paper presents the findings of an investigation conducted to investigate the behaviour of grouted reinforcing bar connections and their failure mechanisms. The bond strength was evaluated using a pull-out test on a bar extended from a grouted sleeve specimen. The test parameters of the study were the bar surface condition (deformed and smooth) and the embedded length (6, 12 and 36 diameter-of-bar (db)). A total of eight specimens were tested to failure under direct tensile loads and the slip of the bars was recorded. Results indicate that an embedment length of 6db allowed the bar to yield, but bond failure dominated in the strain hardening zone. It was also observed that an embedment length of 12db was sufficient to mobilize the tensile capacity of the bar, after which an increase in the grouted sleeve length resulted in no additional capacity

The summer undergraduate research experience as a work-integrated learning opportunity and potential pathway to publication in psychology

© 2019 Golding, Breen, Krause and Allen. Unlike disciplines which focus on skill development from year one of a bachelor's degree, training in psychology in Australia follows the scientist-practitioner model. According to this model, an undergraduate psychology degree should focus on the scientific principles underpinning the discipline and provide a foundation for the development of professional skills in graduate school. However, most Australian psychology undergraduates do not continue into graduate school, and concerns have been raised about their lack of applied skills and work-readiness. Work-integrated learning (WIL) refers to strategies aimed at providing students with practical experiences (e.g., fieldwork, placements, and internships) directly related to their course of study. The objective of WIL is to increase work-readiness. Accreditation standards coupled with the norms of the discipline have historically prevented the inclusion of typical WIL experiences in Australian undergraduate psychology degrees. However, one particular type of WIL activity-the undergraduate research experience (URE)-is particularly suited to psychology. In a typical URE, students collaborate with faculty to conduct research designed to make an original contribution to their field. The current study is a qualitative investigation of stakeholder perceptions of a competitive summer URE program ran from 2012 to 2016. Six faculty members and seven undergraduate students were engaged in semi-structured interviews about their URE experiences. Constructed themes broadly reflected the benefits and challenges of the program and included work-readiness and additional research experience, networking and teamwork, publication, quality of experience and equity of opportunities. Faculty members and students spoke favorably of their UREs in most cases, although issues of administration and financial concerns were mentioned consistently, as were concerns about the length, timing, and nature of projects. Students reported skill development and networking as two of the key benefits of their participation in the program, and article publication was seen as particularly beneficial to career prospects. Our findings suggest that student co-authored publications resulting from UREs are possible, but careful thought is required to optimize their likelihood. Overall, this research adds to a growing literature suggesting that UREs can confer a range of benefits to Australian psychology schools related to increased research capacity and student satisfaction

Corticostriatal connectivity fingerprints:Probability maps based on resting-state functional connectivity

Over the last decade, structure-function relationships have begun to encompass networks of brain areas rather than individual structures. For example, corticostriatal circuits have been associated with sensorimotor, limbic, and cognitive information processing, and damage to these circuits has been shown to produce unique behavioral outcomes in Autism, Parkinson's Disease, Schizophrenia and healthy ageing. However, it remains an open question how abnormal or absent connectivity can be detected at the individual level. Here, we provide a method for clustering gross morphological structures into subregions with unique functional connectivity fingerprints, and generate network probability maps usable as a baseline to compare individual cases against. We used connectivity metrics derived from resting-state fMRI (N = 100), in conjunction with hierarchical clustering methods, to parcellate the striatum into functionally distinct clusters. We identified three highly reproducible striatal subregions, across both hemispheres and in an independent replication dataset (N = 100) (dice-similarity values 0.40-1.00). Each striatal seed region resulted in a highly reproducible distinct connectivity fingerprint: the putamen showed predominant connectivity with cortical and cerebellar sensorimotor and language processing areas; the ventromedial striatum cluster had a distinct limbic connectivity pattern; the caudate showed predominant connectivity with the thalamus, frontal and occipital areas, and the cerebellum. Our corticostriatal probability maps agree with existing connectivity data in humans and non-human primates, and showed a high degree of replication. We believe that these maps offer an efficient tool to further advance hypothesis driven research and provide important guidance when investigating deviant connectivity in neurological patient populations suffering from e.g., stroke or cerebral palsy. Hum Brain Mapp 38:1478-1491, 2017. © 2016 Wiley Periodicals, Inc.status: publishe

Do Children With Autism Spectrum Disorders Understand Pantomimic Events?

SW was supported by grant DEC-2017/01/X/HS2/01722 from the National Science Centre, Poland.Impairments of motor representation of actions have been reported as a core component of autism spectrum disorders (ASD). Individuals with ASD have difficulties in a number of functions such as assuming anticipatory postures, imitating body movements, producing and understanding gestures, and recognizing motor intentions. Such cognitive-motor abilities are all involved in pantomime. However, the available evidence on the production and comprehension of pantomime in individuals with ASD is still inconclusive. The current investigation assessed pantomime comprehension in 40 children with high-functioning ASD and 40 children with typical development balanced for age, IQ, level of formal education, and cognitive profile. The participants were asked to watch video recordings of pantomimes representing simple transitive events enacted by actors and match them to the corresponding pictorial representations. Such pantomimes were delivered in two conditions with different levels of information content (i.e., lean or rich). The two groups of children performed similarly on these tasks. Nonetheless, children with ASD who were administered the pantomimes in the lean condition performed worse than participants who were administered the informatively richer pantomimes. The methodological implications for interpretation of previous findings and future studies are discussed

TAL nucleases (TALNs): hybrid proteins composed of TAL effectors and FokI DNA-cleavage domain

DNA double-strand breaks enhance homologous recombination in cells and have been exploited for targeted genome editing through use of engineered endonucleases. Here we report the creation and initial characterization of a group of rare-cutting, site-specific DNA nucleases produced by fusion of the restriction enzyme FokI endonuclease domain (FN) with the high-specificity DNA-binding domains of AvrXa7 and PthXo1. AvrXa7 and PthXo1 are members of the transcription activator-like (TAL) effector family whose central repeat units dictate target DNA recognition and can be modularly constructed to create novel DNA specificity. The hybrid FN-AvrXa7, AvrXa7-FN and PthXo1-FN proteins retain both recognition specificity for their target DNA (a 26 bp sequence for AvrXa7 and 24 bp for PthXo1) and the double-stranded DNA cleaving activity of FokI and, thus, are called TAL nucleases (TALNs). With all three TALNs, DNA is cleaved adjacent to the TAL-binding site under optimal conditions in vitro. When expressed in yeast, the TALNs promote DNA homologous recombination of a LacZ gene containing paired AvrXa7 or asymmetric AvrXa7/PthXo1 target sequences. Our results demonstrate the feasibility of creating a tool box of novel TALNs with potential for targeted genome modification in organisms lacking facile mechanisms for targeted gene knockout and homologous recombination

Astrometry and geodesy with radio interferometry: experiments, models, results

Summarizes current status of radio interferometry at radio frequencies between Earth-based receivers, for astrometric and geodetic applications. Emphasizes theoretical models of VLBI observables that are required to extract results at the present accuracy levels of 1 cm and 1 nanoradian. Highlights the achievements of VLBI during the past two decades in reference frames, Earth orientation, atmospheric effects on microwave propagation, and relativity.Comment: 83 pages, 19 Postscript figures. To be published in Rev. Mod. Phys., Vol. 70, Oct. 199

Asteroseismology and Interferometry

Asteroseismology provides us with a unique opportunity to improve our understanding of stellar structure and evolution. Recent developments, including the first systematic studies of solar-like pulsators, have boosted the impact of this field of research within Astrophysics and have led to a significant increase in the size of the research community. In the present paper we start by reviewing the basic observational and theoretical properties of classical and solar-like pulsators and present results from some of the most recent and outstanding studies of these stars. We centre our review on those classes of pulsators for which interferometric studies are expected to provide a significant input. We discuss current limitations to asteroseismic studies, including difficulties in mode identification and in the accurate determination of global parameters of pulsating stars, and, after a brief review of those aspects of interferometry that are most relevant in this context, anticipate how interferometric observations may contribute to overcome these limitations. Moreover, we present results of recent pilot studies of pulsating stars involving both asteroseismic and interferometric constraints and look into the future, summarizing ongoing efforts concerning the development of future instruments and satellite missions which are expected to have an impact in this field of research.Comment: Version as published in The Astronomy and Astrophysics Review, Volume 14, Issue 3-4, pp. 217-36