Deconstructable Flush End Plate Beam-to-Column Composite Joints: Component- Based Modelling

[EN] Within a paradigm of designing building structures for their end-of-life deconstruction, thispaper addresses flush end plate beam-to-column composite joints that may be dis-assembledand reused elsewhere. The joints consist of steel beams bolted to steel columns, and these aremade composite over the joint with precast concrete slabs attached to the top flange of thesteel beams with post-tensioned high strength bolted shear connectors installed in clearanceholes. Joints of this type experience partial shear connection, and accordingly their designneeds to incorporate this effect. Experimental work reported elsewhere by the authors showsthat a structural system of this type may indeed be deconstructed, even when loaded beyondthe serviceability limit state, and that the moment-rotation response is both robust andductile. A numerical modelling using ABAQUS software is introduced in the paper, and theresults of this are used identify the parameters most influential in the structural response,and to propose equations for the initial stiffness, moment capacity and rotation capacity of ajoint. These equations are consistent with the component-based representation of theEurocode 4 and draft Australian AS2327 composite structures standard.The work in this paper was supported by the Australian Research Council through an Australian Laureate Fellowship (FL100100063) and a Discovery Project (DP150100446) awarded to the first author. This support is gratefully acknowledged.Bradford, M.; Ataei, A.; Liu, X. (2018). Deconstructable Flush End Plate Beam-to-Column Composite Joints: Component- Based Modelling. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 601-606. https://doi.org/10.4995/ASCCS2018.2018.7296OCS60160

Modeling Virus Transport and Removal during Storage and Recovery in Heterogeneous Aquifers

A quantitative understanding of virus removal during aquifer storage and recovery (ASR) in physically and geochemically heterogeneous aquifers is needed to accurately assess human health risks from viral infections. A two-dimensional axisymmetric numerical model incorporating processes of virus attachment, detachment, and inactivation in aqueous and solid phases was developed to systematically evaluate the virus removal performance of ASR schemes. Physical heterogeneity was considered as either layered or randomly distributed hydraulic conductivities (with selected variance and horizontal correlation length). Geochemical heterogeneity in the aquifer was accounted for using Colloid Filtration Theory to predict the spatial distribution of attachment rate coefficient. Simulation results demonstrate that the combined effects of aquifer physical heterogeneity and spatial variability of attachment rate resulted in higher virus concentrations in the recovered water at the ASR well (i.e. reduced virus removal). While the sticking efficiency of viruses to aquifer sediments was found to significantly influence virus concentration in the recovered water, the solid phase inactivation under realistic field conditions combined with the duration of storage phase had a predominant influence on the overall virus removal. The relative importance of physical heterogeneity increased under physicochemical conditions that reduced virus removal (e.g. lower value of sticking efficiency or solid phase inactivation rate). This study provides valuable insight on site selection of ASR projects and an approach to optimize ASR operational parameters (e.g. storage time) for virus removal and to minimize costs associated with post-recovery treatment

Sustainable high strength steel flush end plate beam-tocolumn composite joints with deconstructable bolted shear connectors

The design of engineering structures for deconstructability can reduce the energy and cost required for their demolition and the disposal of their construction waste, and it also enhances the sustainability of a building by allowing for easy dismantling and the reuse or recycling of structural components and construction materials at the end of the service life of the building. In addition, using high performance materials such as High Strength Steel (HSS) can improve the sustainability of a structure by providing for higher design stresses and accordingly reducing the self-weight of the structure. This paper describes the results of four full-scale beam-to-column deconstructable composite joints with HSS S690 flush end plates. The structural behaviour of the new system in conjunction with application of post-installed friction-grip bolted shear connectors for developing deconstructable composite floors is investigated. The test results show that the proposed composite beam-tocolumn joints can provide the required strength and ductility according to EC3 and EC4 specifications, and that the system can be easily deconstructed at the end of the service life of the structure as a proof of concept

Performance of bolted connections in deconstructable composite frames

The design of engineering structures for deconstructability can reduce the energy and cost required for their demolition and the disposal of their construction waste, and it also enhances the sustainability of a building by allowing for easy dismantling and the reuse or recycling of structural components and construction materials at the end of the service life of the building. In addition, using high performance materials such as High Strength Steel (HSS) can improve the sustainability of a structure by providing for higher design stresses and accordingly reducing the self-weight of the structure. This paper describes the results of four full-scale beam-to-column deconstructable composite joints with HSS S690 flush end plates. The structural behaviour of the new system in conjunction with application of post-installed friction-grip bolted shear connectors for developing deconstructable composite floors is investigated. The test results show that the proposed composite beam-tocolumn joints can provide the required strength and ductility according to EC3 and EC4 specifications, and that the system can be easily deconstructed at the end of the service life of the structure as a proof of concept

The performance of a cable-stayed bridge pylon under close-range blast loads

Recent bridge collapses have raised an awareness of, and a concern for, the safety and robustness of bridges subjected to blast loading scenarios. The incident pressure generated by the explosion can cause severe structural damage and a loss of critical structural members, resulting in partial collapse of the bridge. Previously, most relevant research effort has been devoted to understanding the response of buildings under blast loading and to develop guidelines to increase the resistance of such structures, while relatively little research attention has been focused on bridge structures. Recent advancements in numerical methods have enabled the viable and cost-effective simulation of complicated blast scenarios, and hence these methods provide a useful reference for safeguarding design and assessment of critical infrastructure. To reduce the computational costs, previous studies on long span bridges under blast loads typically take advantage of sub-structuring techniques, in which only part of the structure is modelled. However, such oversimplifications can lead to erroneous results. Accordingly, this study is an attempt to simulate the dynamic response of an entire cable-stayed bridge subjected to blast loading based on best practice techniques obtained from the literature. The response of a steel bridge, designed according to the minimum requirements of the Australian Standard AS5100, is investigated when subjected to blast loads ranging from small to large explosions at different positions above the deck using numerical simulations. In addition, the potential effects of blast loads on different structural components (i.e. the deck and pylons) are discussed and possible blast mitigation strategies such as the application of FRP and optimization of the geometry of the pylons are investigated

Consequences of non-random species loss for decomposition dynamics: experimental evidence for additive and non-additive effects

1.   Although litter decomposition is a fundamental ecological process, most of our understanding comes from studies of single-species decay. Recently, litter-mixing studies have tested whether monoculture data can be applied to mixed-litter systems. These studies have mainly attempted to detect non-additive effects of litter mixing, which address potential consequences of random species loss – the focus is not on which species are lost, but the decline in diversity per se . 2.   Under global change, species loss is likely to be non-random, with some species more vulnerable to extinction than others. Under such scenarios, the effects of individual species (additivity) as well as of species interactions (non-additivity) on decomposition rates are of interest. 3.   To examine potential impacts of non-random species loss on ecosystems, we studied additive and non-additive effects of litter mixing on decomposition. A full-factorial litterbag experiment was conducted using four deciduous leaf species, from which mass loss and nitrogen content were measured. Data were analysed using a statistical approach that first looks for additive identity effects based on the presence or absence of species and then significant species interactions occurring beyond those. It partitions non-additive effects into those caused by richness and/or composition. 4.   This approach addresses questions key to understanding the potential effects of species loss on ecosystem processes. If additive effects dominate, the consequences for decomposition dynamics will be predictable based on our knowledge of individual species, but not statistically predictable if non-additive effects dominate. 5.   We found additive (identity) effects on mass loss and non-additive (composition) effects on litter nitrogen dynamics, suggesting that non-random species loss could significantly affect this system. We were able to identify the species responsible for effects that would otherwise have been considered idiosyncratic or absent when analysed by the methods used in previous work. 6.   Synthesis . We observed both additive and non-additive effects of litter-mixing on decomposition, indicating consequences of non-random species loss. To predict the consequences of global change for ecosystem functioning, studies should examine the effects of both random and non-random species loss, which will help identify the mechanisms that influence the response of ecosystems to environmental change.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73943/1/j.1365-2745.2007.01346.x.pd

SPIFI: a Direct-Detection Imaging Spectrometer for Submillimeter Wavelengths

The South Pole Imaging Fabry-Perot Interferometer (SPIFI) is the first instrument of its kind -a direct-detection imaging spectrometer for astronomy in the submillimeter band. SPIFI ’s focal plane is a square array of 25 silicon bolometers cooled to 60 mK; the spectrometer consists of two cryogenic scanning Fabry-Perot interferometers in series with a 60-mK bandpass filter. The instrument operates in the short submillimeter windows (350 and 450 μm) available from the ground, with spectral resolving power selectable between 500 and 10,000. At present, SPIFI’s sensitivity is within a factor of 1.5-3 of the photon background limit, comparable with the best heterodyne spectrometers. The instrument ’s large bandwidth and mapping capability provide substantial advantages for specific astrophysical projects, including deep extragalactic observations. We present the motivation for and design of SPIFI and its operational characteristics on the telescope

Increasing microbial carbon use efficiency with warming predicts soil heterotrophic respiration globally

The degree to which climate warming will stimulate soil organic carbon (SOC) losses via heterotrophic respiration remains uncertain, in part because different or even opposite microbial physiology and temperature relationships have been proposed in SOC models. We incorporated competing microbial carbon use efficiency (CUE)–mean annual temperature (MAT) and enzyme kinetic–MAT relationships into SOC models, and compared the simulated mass‐specific soil heterotrophic respiration rates with multiple published datasets of measured respiration. The measured data included 110 dryland soils globally distributed and two continental to global‐scale cross‐biome datasets. Model–data comparisons suggested that a positive CUE–MAT relationship best predicts the measured mass‐specific soil heterotrophic respiration rates in soils distributed globally. These results are robust when considering models of increasing complexity and competing mechanisms driving soil heterotrophic respiration–MAT relationships (e.g., carbon substrate availability). Our findings suggest that a warmer climate selects for microbial communities with higher CUE, as opposed to the often hypothesized reductions in CUE by warming based on soil laboratory assays. Our results help to build the impetus for, and confidence in, including microbial mechanisms in soil biogeochemical models used to forecast changes in global soil carbon stocks in response to warming.J.‐S.Y. was funded by the Second Tibetan Plateau Scientific Expedition and Research Program (2019QZKK0305) and the Fundamental Research Funds for the Central Universities (lzujbky‐2019‐kb36). This research was supported by the European Research Council (ERC Grant Agreements 242658 [BIOCOM] and 647038 [BIODESERT]). M. D. is supported by a FPU fellowship from the Spanish Ministry of Education, Culture and Sports (Ref. FPU‐15/00392). P.G.P. acknowledges the Spanish Ministry of Economy and Competitiveness for financial support via the Juan de la Cierva Incorporación Program (IJCI‐2014‐20058)

The Incidence of Malignancy and the Preoperative Assessment of Women Undergoing Hysterectomy with Morcellation for Benign Indications

Background: The use of power morcellation in gynecologic surgery has come under scrutiny secondary to concerns for occult malignancy dissemination. The incidence of undiagnosed gynecologic malignancy when hysterectomy performed for benign indications is not definitive but has been quoted as high as 2.7% (1:37). There is not a standard recommended preoperative evaluation, and variation is anticipated by preoperative complaint or diagnosis. Objectives: To quantify the malignancy incidence in women undergoing hysterectomy for benign indications and to compare the preoperative evaluation of patients undergoing hysterectomy with and without morcellation. Methods: Retrospective cohort of women undergoing hysterectomies between October 2007 and June 2014 was identified by procedural codes through the hospital billing system. Exclusions included hysterectomies performed by gynecologic oncologists or non-gynecologic surgeons and surgeries performed outside the UMass healthcare system. Chart abstraction included demographics; pre-hysterectomy evaluation, including current cervical cytology, pathologic endometrial assessment (biopsy, dilation and curettage), and imaging (ultrasound, MRI, CT scan, sonohysterogram, or hysteroscopy); intraoperative factors; and final diagnosis. Results: Analytic cohort included 2,332 women undergoing hysterectomy with 396 (17.0%) including use of morcellation. The malignancy incidence on final pathology was 2.1% and was different between non-morcellated versus morcellated specimens (2.5% vs. 0.3%, p Conclusion: The incidence of malignancy at time ofhysterectomy performed by non­-oncology trained gynecologists was 2.1% overall, and 0.3% in morcellated cases. The pre-operative evaluation of patients undergoing hysterectomy with morcellation is similar to those without morcellation, except for lower rates of pathologic endometrial assessment. An argument could be made that a pathology assessment is indicated in this group due to risk of dissemination in the case of occult malignancy. The risk of occult malignancy is rare, but this should be discussed with patients and taken into account during the pre-operative evaluation

Non-linear inelastic analysis of steel arches at elevated temperatures

An innovative non-discretisation mechanical-based method is developed in this paper to analyse a steel arch at elevated temperatures so that its behaviour can be quantified. The steel arch has a generic but singly-symmetric cross-section with elastic and plastic parts,and it is subjected to an arbitrary thermal profile which varies along the length of the arch as well as through the depth of the cross-section. The effects of geometric and material non-linearity as well as potential catenary action which can occur at high temperatures are taken into account in the formulation.The efficiency and accuracy of the generic model developed is demonstrated by a comparison with a finite element model undertaken using ABAQUS. The proposed method is then utilised to elucidate some significant factors,such as the magnitude of the temperature at bottom fibre of the cross-section as well as the ratio of the temperature at the top fibre to that at the bottom fibre, on the response of a steel arch member during fire loading. The proposed model provides a computationally superior formulation to that of commercial finite element packages,and forms a platform which can be used for structural steel arch design and evaluation in the development of codified approaches to fire design on a performance basis