Shear Capacity of Monolithic Concrete Joints without Transverse Reinforcement.

yesA mechanism analysis based on the upper-bound theorem of concrete plasticity for monolithic concrete joints without transverse reinforcement is presented. Concrete is modelled as a rigid–perfectly plastic material obeying modified Coulomb failure criteria. Existing stress–strain relationships of concrete in compression and tension are comprehensively modified using the crack band theory to allow for concrete type and maximum aggregate size. Simple equations for the effectiveness factor for compression, ratio of effective tensile strength to compressive strength and angle of concrete friction are then mathematically developed using the modified stress–strain relationships of concrete. In addition, 12 push-off specimens made of all-lightweight, sand–lightweight and normal-weight concrete having maximum aggregate size between 4 and 19 mm were physically tested. Test results and mechanism analysis clearly showed that the shear capacity of monolithic concrete joints increased with the increase of the maximum aggregate size and dry density of concrete. The mean and standard deviation of the ratio between experimentally measured and predicted (by the mechanism analysis shear capacities) are 1·01 and 0·16 respectively, showing a closer prediction and less variation than Vecchio and Collins' equation, regardless of concrete type and maximum aggregate size

Study protocol of a Dutch smoking cessation e-health program

<p>Abstract</p> <p>Background</p> <p>The study aims to test the differential effects of a web-based text and a web-based video-driven computer-tailored approach for lower socio-economic status (LSES) and higher socio-economic status (HSES) smokers which incorporate multiple computer-tailored feedback moments. The two programs differ only in the mode of delivery (video- versus text-based messages). The paper aims to describe the development and design of the two computer-tailored programs.</p> <p>Methods/design</p> <p>Respondents who smoked at the time of the study inclusion, who were motivated to quit within the following six months and who were aged 18 or older were included in the program. The study is a randomized control trial with a 2 (video/text) * 2(LSES/HSES) design. Respondents were assigned either to one of the intervention groups (text versus video tailored feedback) or to the control group (non-tailored generic advice). In all three conditions participants were asked to fill in the baseline questionnaire based on the I-Change model. The questionnaire assessed socio-demographics, attitude towards smoking, knowledge, self-efficacy, social influence, depression, level of addiction, action planning, goal actions, intention to quit smoking, seven-day point prevalence and continued abstinence. Follow-up measurements were conducted at six and twelve months after baseline.</p> <p>Discussion</p> <p>The present paper describes the development of the two computer-tailored smoking cessation programs, their components and the design of the study. The study results reveal different working mechanisms of multiple tailored smoking cessation interventions and will help us to gain more insight into effective strategies to target different subgroups, especially smokers with a lower socio-economic status.</p> <p>Trial registration</p> <p>Dutch Trial Register <a href="http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=NTR3102">NTR3102</a></p

Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta