scholarly journals Failure Mechanisms and Parameters of Elastoplastic Deformations of Anchorage in a Damaged Concrete Base under Seismic Loading

Buildings ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 78
Author(s):  
Oleg Kabantsev ◽  
Mikhail Kovalev

The article addresses mechanisms of anchorage failure in a concrete base studied within the framework of physical experiments. The authors investigated the most frequently used types of anchors, such as the cast-in-place and post-installed ones. The anchorages were studied under static and dynamic loading, similar to the seismic type. During the experiments, the post-earthquake condition of a concrete base was simulated. Within the framework of the study, the authors modified the values of such parameters, such as the anchor embedment depth, anchor steel strength, base concrete class, and base crack width. As a result of the experimental studies, the authors identified all possible failure mechanisms for versatile types of anchorages, including steel and concrete cone failures, anchor slippage at the interface with the base concrete (two types of failure mechanisms were identified), as well as the failure involving the slippage of the adhesive composition at the interface with the concrete of the anchor embedment area. The data obtained by the authors encompasses total displacements in the elastic and plastic phases of deformation, values of the bearing capacity for each type of anchorage, values of the bearing capacity reduction, and displacements following multi-cyclic loading compared to static loading. As a result of the research, the authors identified two types of patterns that anchorages follow approaching the limit state: elastic-brittle and elastoplastic mechanisms. The findings of the experimental research allowed the authors to determine the plasticity coefficients for the studied types of anchors and different failure mechanisms. The research findings can be used to justify seismic load reduction factors to be further used in the seismic design of anchorages.

2008 ◽  
Vol 400-402 ◽  
pp. 513-518 ◽  
Author(s):  
Yong Chang Guo ◽  
Pei Yan Huang ◽  
Yang Yang ◽  
Li Juan Li

The improvement of the load carrying capacity of concrete columns under a triaxial compressive stress results from the strain restriction. Under a triaxial stress state, the capacity of the deformation of concrete is greatly decreased with the increase of the side compression. Therefore, confining the deformation in the lateral orientation is an effective way to improve the strength and ductility of concrete columns. This paper carried out an experimental investigation on axially loaded normal strength concrete columns confined by 10 different types of materials, including steel tube, glass fiber confined steel tube (GFRP), PVC tube, carbon fiber confined PVC tube (CFRP), glass fiber confined PVC tube (GFRP), CFRP, GFRP, polyethylene (PE), PE hybrid CFRP and PE hybrid GFRP. The deformation, macroscopical deformation characters, failure mechanism and failure modes are studied in this paper. The ultimate bearing capacity of these 10 types of confined concrete columns and the influences of the confining materials on the ultimate bearing capacity are obtained. The advantages and disadvantages of these 10 types of confining methods are compared.


Author(s):  
И.Е. Кажекин

В работе рассмотрены вопросы безопасности бортовых электросетей объектов морской индустрии, показано влияние перенапряжений на их основные показатели, которыми определяются опасности смертельных электротравм, опасности возникновения пожаров и взрывов. Представлены результаты математического моделирования электрического разряда по уравнению Майра с учетом особенностей переходного процесса при однофазных замыканиях на корпус. Показана роль напряжения смещения нейтрали по постоянному потенциалу, наибольшие значения которого формируются при неустойчивом контакте фазы с корпусом судна. Описаны результаты экспериментальных исследований переходных процессов, сопровождающихся возникновением неустойчивыми искровыми разрядами. Сравнение результатов расчета по предложенной методике с результатами физических экспериментов показало весьма удовлетворительную сходимость. Предложенная модель может быть использована для уточнения показателей, характеризующих безопасность судовых электросетей. The paper deals with the safety issues of on-board power grids of the marine industry facilities, shows the influence of overvoltages on their main indicators, which determine the dangers of fatal electrical injuries, the risk of fires and explosions. The results of mathematical modeling of an electric discharge according to the Mayr equation, taking into account the features of the transient process in single-phase short circuits to the case, are presented. The role of the bias voltage of the neutral at a constant potential is shown, the highest values ​​of which are formed during unstable contact of the phase with the ship's hull. The results of experimental studies of transient processes accompanied by the appearance of unstable spark discharges are described. Comparison of the calculation results by the proposed method with the results of physical experiments showed a very satisfactory convergence. The proposed model can be used to refine the indicators characterizing the safety of ship power grids.


2020 ◽  
Vol 17 (35) ◽  
pp. 599-608 ◽  
Author(s):  
Alexander A. OREKHOV ◽  
Yuri A. UTKIN ◽  
Polina F. PRONINA

One of the significant innovative technologies is the creation of large-sized structures that work for a long time in space and meet stringent restrictions on overall mass characteristics. Among these structures, in the first place, is the section of bearing truss (BT). This article presents the results of experimental studies of sectors of load-bearing trusses of mesh design for compression. Recently, composite mesh cylindrical shells are used as spacecraft housings. The mesh shell is a supporting structure to which the instruments and mechanisms of the spacecraft are attached. The truss section is made of cross-linked polymer composite material with carbon fibers. The objective of the tests is to confirm the possibility of creating a lightweight mesh construction using a carbon fiber reinforced polymer composite material. To achieve this goal, the authors were assigned the following tasks: selection of carbon filler of polymer composite materials (PCM); selection of PCM binder; determination of the degree of carbon fiber reinforcement; choice of the number and orientation paths of spiral ribs, number of ring ribs and the sizes of individual ribs. As a result of the research, the calculated indicators for ensuring the bearing capacity and stiffness under the application of axial compressive load were obtained. At the same time, with the determination of bearing capacity, the deformation characteristics of the structure were twice determined in order to confirm their repeatability, as well as linear nature of the dependence of axial and radial deformations as a result of the applied load.


2021 ◽  
Vol 42 (3) ◽  
pp. 130
Author(s):  
Sudip Dhakal

The difficulties in performing experimental studies related to diseases of the human brain have fostered a range of disease models from highly expensive and complex animal models to simple, robust, unicellular yeast models. Yeast models have been used in numerous studies to understand Alzheimer’s disease (AD) pathogenesis and to search for drugs targeting AD. Thanks to the conservation of fundamental eukaryotic processes including ageing and the availability of appropriate technological platforms, budding yeast are a simple model eukaryote to assist with understanding human cell biology, offering a platform to study human diseases. This article aims to provide insights from yeast models on the contributions of amyloid beta, a causative agent in AD, and recent research findings on AD chemoprevention.


Geosciences ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 392
Author(s):  
Maurizio Ziccarelli ◽  
Marco Rosone

The presence of minor details of the ground, including soil or rock masses, occurs more frequently than what is normally believed. Thin weak layers, shear bands, and slickensided surfaces can substantially affect the behaviour of foundations, as well as that of other geostructures. In fact, they can affect the failure mechanisms, the ultimate bearing capacity of footings, and the safety factor of the geotechnical system. In this research, numerically conducted through Finite Element Code Plaxis 2D, the influence of a horizontal thin weak layer on the mechanical behaviour of shallow footings was evaluated. The obtained results prove that the weak layer strongly influences both the failure mechanism and the ultimate bearing capacity if its depth is lower than two to four times the footing width. In fact, under these circumstances, the failure mechanisms are always mixtilinear in shape because the shear strains largely develop on the weak layer. However, the reduction in the ultimate bearing capacity is a function of the difference between the shear strength of the foundation soil and the layer. The presence of a thin weak layer decreases the ultimate bearing capacity up to 90%. In conclusion, this research suggests that particular attention must be paid during detailed ground investigations to find thin weak layers. Based on the obtained results, it is convenient to increase the soil volume investigation to a depth equal to four times the width of the foundation.


AERA Open ◽  
2019 ◽  
Vol 5 (3) ◽  
pp. 233285841986815
Author(s):  
Samuel Merk ◽  
Tom Rosman

In-service and preservice teachers are increasingly required to integrate research results into their classroom practice. However, due to their limited methodological background knowledge, they often cannot evaluate scientific evidence firsthand and instead must trust the sources on which they rely. In two experimental studies, we investigated the amount of this so-called epistemic trustworthiness (dimensions expertise, integrity, and benevolence) that student-teachers ascribe to the authors of texts who present classical research findings (e.g., learning with worked-out examples) that allegedly were written by a practitioner, an expert, or a scientist. Results from the first exploratory study suggest that student-teachers view scientists as “smart but evil,” since they rate them as having substantially more expertise than practitioners, while also being less benevolent and lacking in integrity. Moreover, results from the exploratory study suggest that evaluativistic epistemic beliefs (beliefs about the nature of knowledge) predict epistemic trustworthiness. A preregistered conceptual replication study (Study 2) provided more evidence for the “smart but evil” stereotype. Further directions of research as well as implications for practice are discussed.


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