Analytical modeling of masonry load-bearing walls

2003 ◽  
Vol 30 (5) ◽  
pp. 795-806 ◽  
Author(s):  
Yi Liu ◽  
J L Dawe

An analytical technique was developed and encoded for computer application to study the behaviour of concrete masonry load-bearing walls under various loading conditions. Both geometrical and material nonlinearities to account for the moment magnification effect and the degradation of material stiffness are included in the development. Effects of vertical reinforcing steel, masonry tensile cracking, and compressive crushing are included directly in the moment–curvature relationship, which is used in the determination of element stiffnesses at successive load increments. A parametric study was conducted following verification of the analytical model by comparing results with experimental test data. Effective flexural rigidity (EIeff) values at failure were obtained analytically and compared with values suggested in the Canadian masonry code CSA-S304.1-M94. It was concluded that CSA-S304.1-M94 tends to underestimate EIeff values for reinforced walls and thus leads to a conservative design over a range of parameters. Based on approximately 500 computer model tests, a lower bound bilinear limit for the effective rigidity of reinforced masonry walls was established. This limit is believed to provide an accurate and realistic estimate of EIeff.Key words: walls, load bearing, masonry, analytical, nonlinear, rigidity, stress–strain, moment–curvature.

Author(s):  
Clayton Edward James Pettit ◽  
Erum Mohsin ◽  
Carlos Cruz-Noguez ◽  
Alaa E Elwi

Slender, load-bearing masonry walls with slenderness ratios (h/t) greater than 30 are required to be designed as pinned-pinned elements as per North American provisions for masonry, CSA S304-14 (2019) and TMS 402-16 (2016). This provision neglects the contribution of the reactive stiffness of the foundation to the strength of the wall and its effect on the redistribution of bending moments along its height. Eight full-scale masonry walls built with different degrees of base stiffness and tested under an eccentric axial load. Results from the tests showed an increased load-bearing capacity and decreased deflections with increased rotational base stiffness. Experimental data was used to determine key design parameters including the effective flexural rigidity and the moment distribution along the height of the walls. Comparing values of effective flexural rigidity determined from experimental results to code provisions, it was found both codes tend to underestimate the effective flexural rigidity of the walls.


2019 ◽  
Vol 8 (4) ◽  
pp. 4680-4684 ◽  

The research aims at conducting a quality research with Reinforcement of a hollow brick wall. The empty internal sections significantly lower the dead load. With a better surface finish, the side of the block was cast, minimizing the cost of plastering. Several sample mixes are tested to achieve a finished surface. The respective frames were cast with and without reinforcement and the test results were compared. The blocks were used to build masonry walls and ' load-bearing strength ' of the walls was tested. It is possible to use the reinforced hollow block as a load-bearing wall. Nearly 75 percent of the deaths related to the earthquake in the last century,Buildings have collapsed, the majority of which (more than 70 percent)is due to the collapse of buildings made of masonry. Most of the properties in India are Unreinforced Masonry (URM) buildings that are weak and vulnerable even under moderate earthquakes and that function on the wall due to high wind forces, causing severe damage to high wind loads and it is recognized that Reinforced Masonry Building has many advantages over unreinforced masonry building.The use was very limited in Indian building practices and there are still no approved codes and shear walls were used in most constructions, even in mild earthquakes, instead of reinforced masonry walls


2018 ◽  
Vol 49 ◽  
pp. 00100
Author(s):  
Monika Siewczynska ◽  
Barbara Ksit

The moisture content in historical masonry walls, particularly on the ground floor, caused by i.e. lack of damp insulation, is a phenomenon of common occurrence. It is usually analysed in terms of mycological changes, thermal insulation and frost damage. The paper discusses the influence of the increased moisture content on the weight and load bearing capacity of the structure. The determination of moisture content in masonry elements, performed during the inspection of the building, provides information from which an increase in the structure's weight can be defined. Reliable tests for the moisture content and compressive strength of masonry and mortar components are invasive, and the number of testing in historical buildings should be limited to the minimum necessary to preserve their vintage nature. As a result, the received overall picture of the work of masonry may not be consistent with its actual state since historical buildings could have been rebuilt or repaired, and consequently, contain masonry conversions made of various materials with different properties. Absorbability can serve here as an example as it is a factor that disrupts a reliable determination of load bearing capacity values of masonry structures. The article attempts to determine the change in load bearing capacity of a moist masonry structure compared to the original - in the air-dry state - for various types of historical masonry and mortar components. The main influence analysed was due to capillary action, whereas the effect of other sources of moisture, i.e. salinity, was excluded.


Author(s):  
Дмитрий Валериевич Судаков ◽  
Олег Валериевич Судаков ◽  
Людмила Валентиновна Кретинина ◽  
Наталья Владимировна Якушева ◽  
Артём Николаевич Шевцов

Статья посвящена построению прогноза эффективности реконструктивных вмешательств на магистральных нервах предплечья в зависимости от протяженности дефекта нервной ткани и особенностей последующего периода реабилитации пациентов. Данная тематика является весьма актуальной, так как с каждым годом во всем мире наблюдается определенный рост случаев травм различного генеза магистральных нервных стволов, которые затем нередко приводят к временной нетрудоспособности и даже инвалидности пациентов. Реконструктивная микрохирургия многие десятилетия пытается решить целый ряд проблем аутотрансплантации нервных стволов и повысить ее общую эффективность. Но из-за определенных проблем связанных с финансированием, некоторые вопросы трансплантологии и реабилитации остаются нерешенными и в настоящий момент. Все это придает представленной работе важное значение не только медицинского, но и социально - экономического плана. Целью работы стала попытка построения прогноза восстановительных операций на нервной ткани, с учетом объема пораженных структур и периода реабилитации. Объектами исследования стало 180 больных, которым по той или иной причине, осуществлялась реконструктивная операция на одном из магистральных нервов предплечья. Все пациенты были разделены на 3 группы по 60 человек, в зависимости от протяженности дефекта магистрального нерва: до 4 см, от 4 до 8 см и от 8 до 12 см. Последующее разделение внутри каждой группы на подгруппы производилось в зависимости от определенного поврежденного нерва (лучевой, локтевой, срединный). В работе изучалось течение раннего послеоперационного воспалительного процесса, с определением бактериальной микрофлоры в ране. Изучались и отдаленные последствия оперативного вмешательства. Своеобразной новизной для данной тематики в целом, стало выявление последующего установления инвалидности пациентов. Кроме того, важные данные были получены и по срокам реабилитации и частичного или полного восстановления утраченных функций по срокам в зависимости от размеров восстанавливаемого дефекта и от наличия или отсутствия необходимой реабилитации. Полученные в работе данные могут представлять интерес не только для врачей хирургов и травматологов, но и для организаторов здравоохранения, позволяя производить прогнозы по выздоровлению пациентов в каждой определенной клинической ситуации The article is devoted to the construction of a forecast of the effectiveness of reconstructive interventions on the main nerves of the forearm, depending on the length of the defect in the nervous tissue and the characteristics of the subsequent period of rehabilitation of patients. This topic is very relevant, since every year all over the world there is a certain increase in cases of injuries of various origins of the main nerve trunks, which then often lead to temporary disability and even disability of patients. For many decades, reconstructive microsurgery has been trying to solve a number of problems of autotransplantation of nerve trunks and improve its overall efficiency. But due to certain problems associated with funding, some issues of transplantation and rehabilitation remain unresolved at the moment. All this gives the presented work important not only medical, but also socio - economic importance. The aim of this work was to attempt to predict restorative operations on the nervous tissue, taking into account the volume of the affected structures and the period of rehabilitation. The objects of the study were 180 patients who, for one reason or another, underwent a reconstructive operation on one of the main nerves of the forearm. All patients were divided into 3 groups of 60 people, depending on the length of the main nerve defect: up to 4 cm, from 4 to 8 cm, and from 8 to 12 cm. Subsequent division within each group into subgroups was performed depending on the specific damaged nerve ( radial, ulnar, median). The work studied the course of the early postoperative inflammatory process, with the determination of bacterial microflora in the wound. The long-term consequences of surgery were also studied. A peculiar novelty for this topic as a whole was the identification of the subsequent establishment of disability in patients. In addition, important data were obtained on the timing of rehabilitation and partial or complete restoration of lost functions in terms of timing, depending on the size of the restored defect and on the presence or absence of the necessary rehabilitation. The data obtained in this work may be of interest not only for surgeons and traumatologists, but also for healthcare organizers, allowing them to make predictions about the recovery of patients in each specific clinical situation


2020 ◽  
Vol 16 ◽  
Author(s):  
Natasa P. Kalogiouri ◽  
Natalia Manousi ◽  
Erwin Rosenberg ◽  
George A. Zachariadis ◽  
Victoria F. Samanidou

Background:: Nuts have been incorporated into guidelines for healthy eating since they contain considerable amounts of antioxidants and their effects are related to health benefits since they contribute to the prevention of nutritional deficiencies. The micronutrient characterization is based mainly on the determination of phenolics which is the most abundant class of bioactive compounds in nuts. Terpenes constitute another class of bioactive compounds that are present in nuts and show high volatility. The analysis of phenolic compounds and terpenes are very demanding tasks that require optimization of the chromatographic conditions to improve the separation of the components. Moreover, nuts are rich in unsaturated fatty acids and they are therefore considered as cardioprotective. Gas chromatography is the predominant instrumental analytical technique for the determination of derivatized fatty acids and terpenes in food matrices, while high performance liquid chromatography is currently the most popular technique for the determination of phenolic compounds Objective:: This review summarizes all the recent advances in the optimization of the chromatographic conditions for the determination of phenolic compounds, fatty acids and terpenes in nuts Conclusion:: The state-of-the art in the technology available is critically discussed, exploring new analytical approaches to reduce the time of analysis and improve the performance of the chromatographic systems in terms of precision, reproducibility, limits of detection and quantification and overall quality of the results


2021 ◽  
Vol 4 (1) ◽  
pp. 11
Author(s):  
Evrysthenis Vartholomatos ◽  
George Vartholomatos ◽  
George A. Alexiou ◽  
Georgios S. Markopoulos

Central nervous system malignancies (CNSMs) are categorized among the most aggressive and deadly types of cancer. The low median survival in patients with CNSMs is partly explained by the objective difficulties of brain surgeries as well as by the acquired chemoresistance of CNSM cells. Flow Cytometry is an analytical technique with the ability to quantify cell phenotype and to categorize cell populations on the basis of their characteristics. In the current review, we summarize the Flow Cytometry methodologies that have been used to study different phenotypic aspects of CNSMs. These include DNA content analysis for the determination of malignancy status and phenotypic characterization, as well as the methodologies used during the development of novel therapeutic agents. We conclude with the historical and current utility of Flow Cytometry in the field, and we propose how we can exploit current and possible future methodologies in the battle against this dreadful type of malignancy.


2021 ◽  
Vol 242 ◽  
pp. 112569
Author(s):  
Zhiming Zhang ◽  
Juan Murcia-Delso ◽  
Cristián Sandoval ◽  
Gerardo Araya-Letelier ◽  
Fenglai Wang

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