Bespoke Reinforcement for Optimised Concrete Structures

Flexible formwork for concrete structures has been shown to be an appropriate method for the construction of optimised concrete structures (Veenendaal et al. [1], Orr et al. [2]). With the goal of achieving low carbon design, two major challenges exist: 1) to reinforce structures with complex geometries and 2) to provide durable and resilient infrastructures. Meeting both challenges would allow one to capitalise on the fluidity of concrete to meet long-term emissions reductions targets. This will require an entirely new approach to design and construction of concrete structures.Research underway at the University of Bath is attempting to completely replace internal steel reinforcement with a knitted composite cage made from fibre reinforced polymer (FRP) reinforcement. By fabricating the cage in exactly the right geometry, it will be possible to provide the required strength exactly where it is needed.This paper will outline ongoing work which aims demonstrate that CFRP can be woven into geometrically appropriate ‘cages’ for the reinforcement of concrete beams, including consideration of the manufacturing process, construction technique, and technical design requirements

Shear strength theories for beams of variable depth

Flexibly formed reinforced concrete beams usually have varying cross sections along their longitudinal axis, capitalising on the fluidity of concrete to create optimised geometries. According to Orr et al. [1], these new shapes have led to challenges for shear design, especially when the depth of the beams is relatively small. It is crucial to be able to accurately determine the shear strength of such beams to maintain structural safety whilst achieving material optimisation.The effective shear force method is adopted for tapering beams in many design codes. Recent work by Paglietti et al. [2] has highlighted concerns over the use of such an approach. In this paper, the theoretical basis for stress distributions in tapered beams built by Timoshenko [3] and Oden [4] in their elastic range is reviewed and then extended to included cracked behaviour.It is found that the effective shear force method used in design codes does not accurately account for the stress distribution in a section both in elastic and cracked stage of concrete, underestimating the peak shear stress for beams with inclined soffits. This is important for flexibly formed beams, and has implications for designersAs a result of this work, a new calculation and design method for shear reinforcement is proposed.Keywords: variable depth beam, shear strength, shear stress distribution, flexible formwork.The authors acknowledge and are grateful for the support of the BRE CICM (www.bath.ac.uk/bre), the University of Bath, and the China Scholarship Council who collectively fund the PhD position that has resulted in this work

Likelihood ratio tests in random graph models with increasing dimensions

We explore the Wilks phenomena in two random graph models: the $\beta$-model and the Bradley-Terry model. For two increasing dimensional null hypotheses, including a specified null $H_0: \beta_i=\beta_i^0$ for $i=1,\ldots, r$ and a homogenous null $H_0: \beta_1=\cdots=\beta_r$, we reveal high dimensional Wilks' phenomena that the normalized log-likelihood ratio statistic, $[2\{\ell(\widehat{\mathbf{\beta}}) - \ell(\widehat{\mathbf{\beta}}^0)\} -r]/(2r)^{1/2}$, converges in distribution to the standard normal distribution as $r$ goes to infinity. Here, $\ell( \mathbf{\beta})$ is the log-likelihood function on the model parameter $\mathbf{\beta}=(\beta_1, \ldots, \beta_n)^\top$, $\widehat{\mathbf{\beta}}$ is its maximum likelihood estimator (MLE) under the full parameter space, and $\widehat{\mathbf{\beta}}^0$ is the restricted MLE under the null parameter space. For the homogenous null with a fixed $r$, we establish Wilks-type theorems that $2\{\ell(\widehat{\mathbf{\beta}}) - \ell(\widehat{\mathbf{\beta}}^0)\}$ converges in distribution to a chi-square distribution with $r-1$ degrees of freedom, as the total number of parameters, $n$, goes to infinity. When testing the fixed dimensional specified null, we find that its asymptotic null distribution is a chi-square distribution in the $\beta$-model. However, unexpectedly, this is not true in the Bradley-Terry model. By developing several novel technical methods for asymptotic expansion, we explore Wilks type results in a principled manner; these principled methods should be applicable to a class of random graph models beyond the $\beta$-model and the Bradley-Terry model. Simulation studies and real network data applications further demonstrate the theoretical results.Comment: This paper supersedes arxiv article arXiv:2211.10055 titled "Wilks' theorems in the $\beta$-model" by T. Yan, Y. Zhang, J. Xu, Y. Yang and J. Zh

Less is more:a review of low energy standards and the urgent need for an international universal zero energy standard

There are in excess of 70 low or zero energy/carbon building definitions/standards in circulation around the world. However there are few zero energy or zero carbon buildings. This suggests that despite, or possibly because of, a continuing debate over definitions, aspiration has not been met by reality. In this paper the most important 35 standards are reviewed and a correlation between activity in standard generation and completed buildings is presented. Combining this with the requirement for an 80% cut in carbon emissions, a consideration of the proportion of humanity that live in countries without any standards and the ratio of new-build activity vs. pre-existing stock, leads to a conclusion that there is an urgent need for a binding international zero (rather than low) energy/carbon standard that can be adopted world-wide. It is argued this is only possible if carbon is ignored in favour of energy, and many lifecycle issues put to one side. In part this is because of changing national carbon intensities within the energy supply chain, but it is also due to unresolved issues in carbon and energy accountancy. It is hence suggested that such issues are left to optional additional local standards

Ca2+/CaM Modulates the Functional Effects of cMyBP-C on the Thin Filament

Background. Cardiac myosin binding protein-C (cMyBP-C) is an essential regulator of heart muscle function that is necessary for both normal contraction and for increased contractility in response to inotropic stimuli(1-7). Effects of cMyBP-C on contraction are due to dynamic interactions of cMyBP-C with both actin and myosin, but the mechanism(s) by which cMyBP-C binding to these ligands is modulated are only partly understood. Recently, calmodulin (CaM) was shown to bind to cMyBP-C in the regulatory M-domain(8, 9) near a conserved actin binding site(10). Here we investigated whether CaM competes with actin for binding to cMyBP-C and thus whether CaM affects cMyBP-C function. Methods. Recombinant N’-terminal domains of cMyBP-C were used in pull-down assays, co-sedimentation binding assays, and actin activated myosin ATPase assays to determine effects of CaM binding on cMyBP-C. Results. In accordance with previous reports, we found that CaM binds to N’-terminal domains of cMyBP-C in the presence of Ca2+ (Ca2+/CaM) with a binding affinity comparable to cMyBP-C binding to actin (3-10 μM). We further show that Ca2+/CaM reduces cMyBP-C apparent binding affinity for actin, consistent with the competition between Ca2+/CaM and actin for binding to cMyBP-C. Ca2+/CaM also reversed the inhibitory effects of cMyBP-C N’-terminal domains on actin activated myosin ATPase rates, consistent with reduced cMyBP-C interactions with actin. However, apo-CaM (calcium-free calmodulin) did not influence the ability of cMyBP-C to activate actomyosin ATPase rates at low Ca2+. Phosphorylation of cMyBP-C by PKA significantly increased its binding to both Ca2+/CaM and apo-CaM. Phosphorylated cMyBP-C was also a less potent regulator of cross-bridge cycling in ATPase assays. Conclusions. These data demonstrate that Ca2+/CaM competes with actin for binding to cMyBP-C and selectively reverses the inhibitory effects of cMyBP-C on actomyosin interactions. However, apo-CaM does not compete with cMyBP-C binding to actin and does not affect the ability of cMyBP-C to activate the thin filament at low Ca2+. Ca2+/CaM may serve as additional regulatory mechanism in addition to phosphorylation of cMyBP-C to regulate its function. These data suggest that Ca2+/CaM is a novel modulator of cMyBP-C function that can dynamically tune cMyBP-C effects on contraction potentially as [Ca2+]i rises and falls during the time course of a single heart beat

Dataset for "Wound Fibre Reinforced Polymer shear reinforcement for non-prismatic concrete beams"

The dataset includes: 1. experimental data measuring the strain of W-FRP (Wound Fibre Reinforced Polymer) reinforced tapered beams under different load conditions; 2. MATLAB files of the prediction-making following the revised ACI 440, CSA S806 and MCFT model; 3. a spreadsheet to summarise the predictions.The experimental data were collected during the tests of the tapered beams. They include the load, displacement, strain of longitudinal bars and strain of shear reinforcement. Respectively, they were collected by the loading cell, transducers, strain gauges. The predictions were calculated by the models built based on MATLAB