Implementation and validation of a total displacement non-linear homogenization approach for in-plane loaded masonry

Two simple homogenization models suitable for the non-linear analysis of masonry walls in-plane loaded are presented. A rectangular running bond elementary cell is discretized by means of twenty-four constant stress threenoded plane-stress triangular elements and linear two-noded interfaces. Non-linearity is concentrated on mortar reduced to interface, exhibiting a holonomic behavior with softening. The paper shows how the mechanical problem in the unit cell can be characterized by very few displacement/stress variables and how homogenized stress-strain behavior can be evaluated by means of a small-scale system of non-linear equations. At a structural level, it is therefore not necessary to solve a homogenization problem at each load step in each Gauss point and a direct implementation into commercial software as an external user supplied subroutine is straightforward. Nonlinear structural analyses are conducted on a variety of different problems, for which experimental and numerical data are available in the literature, in order to show that accurate results can be obtained with a limited computational effort

Fatigue assessment of steel riveted railway bridges: Full-scale tests and analytical approach

[EN] This paper describes a double experimental and analytical study of the fatigue behaviour of the Quisi and Ferrandet Bridges, twin 170 m long steel railway bridges constructed between 1913 and 1915 with typical Pratt truss structures and riveted connections. These bridges are part of the Spanish national railway network connecting the towns of Alicante and Denia, one of the key networks in the Valencia Region (Spain). The experimental laboratory investigation involved fatigue testing in one of the ICITECH laboratories at the Universitat Politècnica de València of: (i) a full-scale bridge span and (ii) an upper cross beamfromthe Ferrandet Bridge. During the tests, Linear Variable Displacement Transducers (LVDTs) and Strain Gauge (SG) sensorswere used to capture the possible nucleation and propagation of fatigue cracks. Fatigue test carried out on the cross beam identified: (i) fatigue life of the critical detail, (ii) fatigue hot-spots along the cross beam and (iii) strain redistribution along the riveted element during crack growth. The experimental results from the full-scale bridge were adopted to calibrate an elastic numerical model of the whole structure, which was in turn used to estimate the Quisi Bridge's remaining fatigue life. The definition of the class of detail and remaining fatigue lifewere calculated by the S¿N curvesmethod, according to Eurocode 3, considering the available information on the bridges' loading histories.Bertolesi, E.; Buitrago, M.; Adam, JM.; Calderón García, PA. (2021). Fatigue assessment of steel riveted railway bridges: Full-scale tests and analytical approach. Journal of Constructional Steel Research. 182:1-16. https://doi.org/10.1016/j.jcsr.2021.10666411618

3D advanced numerical modelling of a catalan-layered masonry vault unreinforced and reinforced with glass-TRM materials and subjected to vertical support movements

Peer-review under responsibility of the organizing committee of COMPDYN 2021.The COMPDYN 2021 Proceedings are now available for download as an E-book: Volume 1: https://generalconferencefiles.s3.eu-west-1.amazonaws.com/compdyn_2021_proceedings_v1.pdf ; Volume 2: https://generalconferencefiles.s3.eu-west-1.amazonaws.com/compdyn_2021_proceedings_v2.pdf .The Conference was held online in conjunction with UNCECOMP 2021 and EUROGEN 2021.Copyright © 2021 The Authors. This paper presents the numerical results obtained simulating a 4x4mq masonry vault (unreinforced and reinforced with glass-TRM) tested at the Universitat Politecnica de Valencia (Spain). The vault was built using a traditional Catalan layered-construction technique and its structural behavior was analyzed when subjected to monotonic vertical displacements in one of its supports. The geometry and construction technique of the vault resembled those in a church on the outskirts of Valencia, which collapsed probably due to soil settlements. Indeed, due to their peculiar geometric and mechanical features, these structures are especially prone to damage from support movements produced by ground settlements or earthquakes. Two advanced 3D numerical models were developed using the commercial software Abaqus to study the vault response with and without the application of an extrados layer of lime based TRM strengthening material. The FE software allowed the adoption of a concrete damage plasticity (CDP) material model which was employed to both masonry support and TRM strengthening material, after a preliminary tuning of the compressive and tensile mechanical properties of the constituent materials. The outputs obtained with the FE models coupled with the results of the tests, provided valuable information to the scientific community on the available modelling strategies to be used to evaluate the behavior of ancient masonry double-curvature structures pre-damaged by vertical movements of the vault supports and repaired with TRM materials

TRM-Strengthened Timbrel Cross Vaults Subjected to Vertical Settlements

Two full-scale timbrel cross vaults subjected to vertical settlements in one of their supports were tested at the ICITECH laboratories of the Universitat Politècnica de València. In one of the vaults a support was moved downwards, while the other was subjected to upward-downward displacements in one support. Both tests are described and analysed in detail in Torres et al. [1,2]. Both vaults presented certain levels of post-test damage in the form of cracks and significant displacements. In order to analyse the effectiveness of the reinforcement of previously damaged vaults, both were strengthened with TRM and subjected to further testing in which vertical settlements were applied to one support. The TRM strengthening comprised an extrados layer composed of a 25x25mm glass grid embedded into two approximately 5 mm thick layers of cementitious matrix. The TRM strengthening was able to withstand higher peak loads and prevent the formation of cracks along the extrados surface of the structure, while as expected, ductility increased. A 3D macro-modelling FE strategy on Abaqus commercial software was also adopted to study the behaviour of the vaults during the tests

Analysing local failure scenarios to assess the robustness of steel truss-type bridges

Many of the steel bridge collapses occur in truss-type bridges. This is, in fact, the focus of this study involving an assessment of the robustness of this type of structures based on an actual bridge that the authors had extensively monitored and controlled. Robustness was assessed by means of computer simulations of various Damage Scenarios (DSs) to analyse the structural bridge capacity to efficiently activate Alternative Load Paths (ALPs). The computational models have been previously validated with the results of load tests on the bridge and a laboratory test on a full-scale bridge span. The DSs have considered a series of non-simultaneous failures in different elements. The results indicate that the structure is capable of not triggering a disproportionate collapse after each of the DSs with the help of the efficient activation of ALPs that required the contribution of other elements with extra-strength capacity as well as from the superstructure and the joints working under bending moments. The results were used as the basis for practical recommendations for: i) the design of new steel bridges and the retrofit of existing ones and ii) monitoring the structure for the optimal position of sensors to predict local failures that could spread to the rest of the bridge

Factors influencing self-healing mechanisms of cementitious materials: A review

Data availability: Data will be made available on request.Copyright © 2023 The Author(s). The increasing awareness of climate change and global warming has pushed industries to be more conscious of their environmental impact, especially in the construction industry with the main contributor being concrete. Concrete is a material that is in very high demand in the construction industry for structural applications. However, it’s a material with a major concern with the challenges of microcracking. New technology has seen the development of self-healing material, using novel techniques to bring cementitious materials back to its original state. This paper reviews and evaluates the novel techniques adopted by the researchers in the field to achieve a self-healing material, with the main focus being on the factors influencing the mechanisms of autogenous healing and bacteria-based healing. Various parameters including bacteria type, pH, temperature, nutrient, urea, and Ca2+ concentration, bacteria concentration and application, pre-cracking, healing condition, cement type, and crack width are all important for healing efficiency, although the use of water to facilitate both autogenous and ureolytic bacteria healing mechanism is paramount for the triggering of healing processes. This study thoroughly presents various factors and their correlation to the healing mechanisms of autogenous healing and ureolytic bacteria healing. Further studies are identified to better understand the exact mechanism taking place and which healing process contributed to how much of the healing, and this review could serve as an informative platform for these pursues

Cell-type expression and activation by light of neuropsins in the developing and mature Xenopus retina

Photosensitive opsins detect light and perform image- or nonimage-forming tasks. Opsins such as the “classical” visual opsins and melanopsin are well studied. However, the retinal expression and functions of a novel family of neuropsins are poorly understood. We explored the developmental time-course and cell-type specificity of neuropsin (opn5, 6a, 6b, and 8) expression in Xenopus laevis by in situ hybridization and immunohistochemistry. We compared the Xenopus results with publicly available single cell RNA sequencing (scRNA-seq) data from zebrafish, chicken, and mouse. Additionally, we analyzed light-activation of neuropsin-expressing cells through induction of c-fos mRNA. opn5 and opn8 expression begins at stage 37/38 when the retinal circuits begin to be activated. Once retinal circuits connect to the brain, opn5 mRNA is distributed across multiple retinal cell types, including bipolar (~70%–75%), amacrine (~10%), and retinal ganglion (~20%) cells, with opn8 present in amacrine (~70%) and retinal ganglion (~30%) cells. opn6a and opn6b mRNAs emerge in newborn-photoreceptors (stage 35), and are colocalized in rods and cones by stage 37/38. Interestingly, in the mature larval retina (stage 43/44), opn6a and opn6b mRNAs become preferentially localized to rods and cones, respectively, while newborn photoreceptors bordering the proliferative ciliary marginal zone express both genes. In zebrafish, opn6a and opn6b are also expressed in photoreceptors, while Müller glia and amacrine cells express opn8c. Most neuropsin-expressing retinal ganglion cells display c-fos expression in response to light, as do over half of the neuropsin-expressing interneurons. This study gave a better understanding of retinal neuropsin-expressing cells, their developmental onset, and light activation

Fatigue Assessment of Old Riveted Railway Bridges: Laboratory Testing of a Real Bridge

The bridge over the Quisi Ravine in Alicante Province (Spain), built between 1913 and 1915, consists of six 22-22-42-42-22-22 m long steel Pratt truss spans, the lateral spans being isostatic and the central spans continuous. All the joints between the steel elements are riveted. As the bridge has been carrying railway traffic for more than 100 years, its condition needed to be assessed before carrying out the necessary repairs reinforcement to extend its service life. One of the most interesting tasks on the bridge involved a study of its fatigue behaviour to estimate its remaining useful life. Only a few kilometres away there happened to be another bridge with identical geometry over the Ferrandet Ravine, which had recently been dismantled and taken out of service and had carried the same railway traffic as the one over the Quisi Ravine. Advantage was therefore taken of this unique opportunity to test one of its isostatic spans in order to extrapolate the results to the Quisi Bridge. These tests were carried out at the ICITECH laboratories at the Universitat Politècnica de València in two different scenarios: 1) one test on a 22 m span, and 2) another on one of its girders, in both of which simulated railway traffic cyclical loads were applied. The results allowed us to estimate the number of trains that could pass over the bridge and its remaining service life, and also to define a monitoring method to help in decision making in case of possible failures of its component parts. The study also included an analysis of the bridge’s robustness in local failures of some of its elements, which led to a further bridge cyclical loading test with a deliberately damaged component. Even though other researchers had previously carried out fatigue tests on full-scale riveted bridge elements, the ICITECH study is unique in that it is the first time a full-scale bridge has been subjected to fatigue tests. This work was accompanied by advanced numerical modelling studies considering the fracture mechanics theory

Cholinergic receptor pathways involved in apoptosis, cell proliferation and neuronal differentiation

Acetylcholine (ACh) has been shown to modulate neuronal differentiation during early development. Both muscarinic and nicotinic acetylcholine receptors (AChRs) regulate a wide variety of physiological responses, including apoptosis, cellular proliferation and neuronal differentiation. However, the intracellular mechanisms underlying these effects of AChR signaling are not fully understood. It is known that activation of AChRs increase cellular proliferation and neurogenesis and that regulation of intracellular calcium through AChRs may underlie the many functions of ACh. Intriguingly, activation of diverse signaling molecules such as Ras-mitogen-activated protein kinase, phosphatidylinositol 3-kinase-Akt, protein kinase C and c-Src is modulated by AChRs. Here we discuss the roles of ACh in neuronal differentiation, cell proliferation and apoptosis. We also discuss the pathways involved in these processes, as well as the effects of novel endogenous AChRs agonists and strategies to enhance neuronal-differentiation of stem and neural progenitor cells. Further understanding of the intracellular mechanisms underlying AChR signaling may provide insights for novel therapeutic strategies, as abnormal AChR activity is present in many diseases