Derivation of normalized pressure impulse curves for flexural ultra high performance concrete slabs

In previous studies, a finite-difference procedure was developed to analyze the dynamic response of simply supported normal reinforced concrete (NRC) slabs under blast loads. Ultra high performance concrete (UHPC) is a relatively new material with high strength and high deformation capacity in comparison with conventional normal strength concrete. Therefore, the finite-difference procedure for analysis of conventional reinforced concrete members against blast loads needs to be significantly adapted and extended to accommodate UHPC. In this paper, an advanced moment-rotation analysis model, employed to simulate the behavior of the plastic hinge of an UHPC member, is incorporated into the finite-difference procedure for the dynamic response analysis of reinforced UHPC slabs under blast loads. The accuracy of the finite-difference analysis model that utilized the moment-rotation analysis technique was validated using results from blast tests conducted on UHPC slabs. The validated finite-difference model was then used to generate pressure impulse (PI) curves. Parametric studies were then conducted to investigate the effects of various sectional and member properties on PI curves. Based on the simulated results, two equations were derived that can be used to normalize a PI curve. Further numerical testing of the normalization equations for UHPC members was then undertaken. The generated normalized PI curve, accompanied by the derived normalization equations, can be used for the purposes of general UHPC blast design.Jonathon Dragos; Chengqing Wu; Matthew Haskett; and Deric Oehler

Effect of Maternal Retinol Status at Time of Term Delivery on Retinol Placental Concentration, Intrauterine Transfer Rate, and Newborn Retinol Status

Retinol (vitamin A) is essential, so the objective of this Institutional Review Board approved study is to evaluate retinol placental concentration, intrauterine transfer, and neonatal status at time of term delivery between cases of maternal retinol adequacy, insufficiency, and deficiency in a United States population. Birth information and biological samples were collected for mother-infant dyads (n = 260). Maternal and umbilical cord blood retinol concentrations (n = 260) were analyzed by HPLC and categorized: deficient (≤0.7 umol/L), insufficient (\u3e0.7-1.05 umol/L), adequate (\u3e1.05 umol/L). Intrauterine transfer rate was calculated: (umbilical cord blood retinol concentration/maternal retinol concentration) × 100. Non-parametric statistics used include Spearman\u27s correlations, Mann-Whitney U, and Kruskal-Wallis tests. p-values \u3c0.05 were statistically significant. Only 51.2% of mothers were retinol adequate, with 38.4% insufficient, 10.4% deficient. Only 1.5% of infants were retinol adequate. Placental concentrations (n = 73) differed between adequate vs. deficient mothers (median 0.13 vs. 0.10 μg/g; p = 0.003). Umbilical cord blood concentrations were similar between deficient, insufficient, and adequate mothers (0.61 vs. 0.55 vs. 0.57 μmol/L; p = 0.35). Intrauterine transfer increased with maternal deficiency (103.4%) and insufficiency (61.2%) compared to adequacy (43.1%), p \u3c 0.0001. Results indicate that intrauterine transfer rate is augmented in cases of maternal retinol inadequacy, leading to similar concentrations in umbilical cord blood at term delivery

The discrete rigid body rotation of reinforced concrete beams using partial interaction and shear friction theory.

In reinforced concrete members, two types of deformations exist: deformations due to curvature distribution and deformation due to discrete localised conditions such as cracks. The latter is the subject of this thesis, which presents a new approach for evaluating the discrete moment-rotation relationship of reinforced concrete members. This thesis is a collection of submitted, accepted or published papers from internationally recognised Journals, where the titles of Chapters 1 through 13 reflect the titles of the Journal papers. Each chapter takes the following format: the key theory and results from each journal paper are presented in a short synopsis, after which the journal paper is presented in full. This provides the reader, if desired, with the ability to understand the research in full by only reading the synopses of each chapter. In Chapter 1, the peripheral areas of shear friction theory, partial interaction theory and rigid body displacement are combined to quantify the moment-rotation response of any reinforced concrete member. It is discussed how partial interaction theory is used to model the behaviour of the reinforcement, shear friction theory the behaviour of the concrete, and that both these behaviours are combined through a rigid body displacement profile. This rigid body rotation approach is a structural mechanics model, and hence can be used to quantify the moment-rotation response of any reinforced concrete member (the subject of this thesis), and amongst other things the shear capacity of a concrete member and the influence of confinement on member behaviour (not covered in or the subject of this thesis). Importantly, closed form solution can be developed for all failure mechanisms, and flexural failure closed form solutions are presented in this thesis. In Chapters 2-4, the partial interaction behaviour of steel reinforcing bars and externally bonded and near surface mounted FRP plates is described in detail. Specifically, Chapters 2 and 3 quantify the bond characteristics of steel reinforcing bars and embedded near surface mounted (NSM) fibre reinforced polymer (FRP) plates. Previously published pull test data is analysed to determine the local bond stress-slip relationship of deformed steel reinforcing bars, and experimental testing of embedded NSM FRP plates performed and analysed to determine the influence of embedment on the bond behaviour of embedded NSM FRP plates. In Chapter 4, partial interaction mathematical expressions are developed to model the elasto-plastic load-slip (P-Δ) behaviour of steel reinforcing bars. These mathematical expressions are later used to model the behaviour of externally bonded (EB) and NSM steel plates. These mathematical load-slip expressions are a critical component of the moment-rotation analysis technique. In Chapter 5, the rigid body rotation model is described in detail and an iterative solution technique presented. The predicted moment-rotation behaviour of reinforced concrete beams is compared to that obtained experimentally with excellent accuracy. In Chapter 6, a closed form solution technique is presented for determining the moment-rotation response of an unplated or plated reinforced concrete member. This is a more user friendly analysis technique and can be used directly to determine the moment and rotation at failure without developing the entire moment-rotation response from the start of loading to failure. In Chapter 7, the influence of bond on the rotation capacity of both unplated, externally bonded and near surface mounted plated reinforced concrete members is assessed, where it is shown that bond is a critical component of ductility. In Chapters 8-11, an application of the moment-rotation model is presented. Moment redistribution expressions are derived for propped cantilevers and continuous members from elementary structural mechanics, and it is shown that the moment redistribution capacity of a member is proportional to the moment and rotation capacity of the section. Various examples of moment redistribution are presented, and finally a method to design for moment redistribution is presented where it is shown that the non-hinging region needs to remain elastic for the hinge to redistribute its maximum moment. In Chapters 12 and 13, the shear friction behaviour of concrete is examined in detail and a method for extracting the shear friction parameters of initially uncracked hydrostatically confined concrete is presented. A generic expression for the shear friction parameters of initially uncracked concrete is developed, where the shear stress is a function of the normal stress across and displacement of the sliding plane, and the compressive strength of concrete. A previously developed expression for the shear friction parameters of initially cracked concrete is modified so that the shear stress is expressed as a function of the normal stress across and displacement of the sliding plane and the compressive strength of concrete. Expressing the shear friction parameters in this way allows bounds to be developed using Mattock’s shear stress limits. These bounds for both initially cracked and uncracked concrete are expressed mathematically for the generic shear friction parameters. The development of these shear friction parameters and bounds will allow the rigid body rotation model to consider sliding failure of concrete, and quantify the effect of confinement through stirrups or FRP wrapping on the moment-rotation response.Thesis (Ph.D.) -- University of Adelaide, School of Civil, Environmental and Mining Engineering, 201

A generic unified reinforced concrete model

The behaviour of reinforced concrete members with ductile steel reinforcing bars at the ultimate limit state is extremely complex. Consequently, there has been a tendency for the seemingly disparate research areas of flexure, shear and confinement to follow separate paths in order to develop safe approaches to design. In this paper, it is shown how the already much researched and established, but somewhat peripheral, areas of reinforced concrete research of shear friction, partial interaction and rigid body displacements can be combined to produce a single unified reinforced concrete model that simulates the moment-rotation of hinges and their capacities, the shear deformation across critical diagonal cracks leading to failure and the effect of confinement on these behaviours. It is shown that this unified reinforced concrete model is completely generic, as it can be used to simulate reinforced concrete members with any type of reinforcement material (including brittle steel or fibre-reinforced polymer), various cross-sectional shapes of reinforcement (not only round bars but also flat externally bonded or rectangular near surface mounted adhesively bonded plates) and any type of concrete (e.g. high-strength or fibre-reinforced concrete). This new model, therefore, should allow the development of more accurate and safe design procedures as well as enabling more rapid development of new technologies

Citalopram improves metabolic risk factors among high hostile adults: Results of a placebo-controlled intervention.

Hostility is associated with a number of metabolic risk factors for cardiovascular disease, including waist—hip ratio, glucose, and triglycerides. Along with hostility, many of these measures have also been shown to be associated with reduced central serotonergic function. We have previously reported that a citalopram intervention was successful in reducing hostility by self-report assessment (Kamarck et al., 2009). Here we examine the effects of this serotonergic intervention on metabolic risk factors in the same sample