Eccentric Opening Research Articles

Cyclic behavior of the reinforced concrete shear walls with opening retrofitted with steel plate

AbstractThe reinforced concrete (RC) shear walls are widely used as the lateral load‐resisting system due to their adequate ductility and great energy dissipation capacity. On the other hand, use of these walls can reduce the size of the beams and columns and also, decreases the lateral displacements. However, presence of the openings in the shear walls alters the behavior of the wall and therefore, the dimensions and position of the opening play a key role in the performance of this structural system. In this study, an RC shear wall with eccentric opening was verified using ABAQUS software. This model, which is called the reference model, a wall and a pier have been created according to aspect ratios given by ACI318‐14. This model was retrofitted with the steel plates arranged in various patterns and effect of each pattern on the system's performance was investigated and the best one was selected. The best steel plate arrangement increased the ultimate strength, maximum strength, cracking strength, and energy dissipation capacity by 127.3%, 13.42%, 22.53%, and 16.8%, respectively. To practically use this retrofit technique, three low, mid, and high‐rise buildings designed based on the old and new versions of the Iranian Code of Practice for Seismic Resistant Design of Buildings (Standard 2800) were upgraded with this technique and their performance was evaluated and performance of the substandard and standard buildings were compared with each other. The research results showed the ST52 steel plates do not considerably increase the maximum and cracking strength and could enhance the ultimate strength insignificantly. By retrofitting the edges of the openings by the diagonal steel plates and preventing spread of the cracks at the edges and corners, satisfactory results could be attained. Simultaneous use of the vertical and horizontal plates is an effective solution to increase the flexural and shear capacity of the structure.

Cyclic response of infilled RC frames with window and door openings: Experimental results and damage interpretation

AbstractThe paper presents the results of an experimental investigation assessing the influence of the openings typology and position on the cyclic response of masonry‐infilled reinforced concrete frames. The experimental program consisted of seven 2/3 scale square frame specimens infilled with hollow clay bricks, which were subjected to quasi‐static lateral cyclic tests up to large drifts. A reference bare frame was also tested for comparison. The specimens included solid infill walls, infills with door openings, and infills with window central and eccentric openings. The experimental responses of the specimens were analyzed in terms of strength, stiffness, energy dissipation capacity, and equivalent damping, and were compared to those of the reference bare frame and fully infilled frame. Results revealed a significant modification of the resisting mechanisms as a function of the typology and position of the openings with respect to the case of a fully infilled frame, although the lateral resisting capacity was not substantially modified. On the other hand, it was observed that the achievement of the limit state thresholds occurred at substantially different interstorey drifts, indicating different damage metrics. Simple regression analyses, based on the experimental results of this study and from the literature, were finally conducted to interpret the modification of the peak force and of the corresponding drift as a function of synthetic parameters defining the opening arrangement.

Analytical study on behaviour and performance of infilled frame structure with reinforced eccentric opening

This numerical analysis has discussed the behaviour of the frame structure with eccentric infill wall opening modelled with shell and strut elements. In the beginning, validation models were created by following the laboratory tests results. Then, a simple one-storey infill frame structure with an opening was modelled with varying ratios by taking the strut angle formed to obtain an equation for the strut width that corresponds to the behaviour of shell element model with strut angles variation. The strut width equation was then applied to the 3-storey infill frame structures. The behaviour comparison between the strut and shell element model was then investigated by linear and nonlinear static analysis. The strut width equation for infill wall frame with eccentric openings (Weo) is determined by modifying the stiffness coefficient (Ce) based on the opening ratio. The application of the Weo equation to the infill frame model showed that the strut model had a comparable behaviour to the shell element model. The drift ratio comparison showed that the smaller the strut angle, the greater the structure stiffness. The pushover analysis shows the infilled frame model was able to withstand a larger base shear force than the open frame model.

Response of steel frame filled by prefabricated RC infill walls with eccentric opening: Experimental study

A steel frame filled by prefabricated RC infill wall (SFRCW) is an effective lateral load-resisting system wherein RC infill walls are embedded inside. The presence of eccentric opening (EO) such as door or window usually significantly reduces the lateral stiffness and strength. In order to accurately evaluate the effect of the EO on the seismic performance of the SFRCW structure, the cyclic quasi-static tests on two, 1/3-scaled, two-story, single-span SFRCW-EO specimens were performed. Both specimens showed the shear-dominated failure mode, moderate ductile behavior, and pinching hysteretic feature. The concrete cracks were induced from the corners of the EO and were attributed to stress concentration phenomena. The initial lateral stiffness was approximately 50 kN/mm, overall ductility ranged from 2.48 to 2.95, and the overstrength factor reached 2.5. The interface slips and separations between RC infill wall and surrounding steel frame in SFRCW-EO specimens were considerably tiny that could be neglected. The flushed end-plate connection, which had the enough rotation capacity and tension-resisting capacity, was an effective partially-restrained (PR) connection used in the SFRCW-EO. The overall seismic behavior of SFRCW-EO was weaker compared to that of the steel frame with solid RC infill walls because it failed by serious concrete crush. In addition, the on-site assembly was more convenient for the SFRCW-EO specimen. Further, strengthening measures such as the use of an embedded beam were essential for ensuring the integrity of infill walls and improving their overall seismic behavior.

Analysis of confined masonry with strengthening around the opening

Analysing confined masonry (CM) with strengthening around the opening (analytical model) was conducted numerically. The opening variations were centric and eccentric opening doors with an opening ratio of 16.93% and 31.75%; centric and eccentric opening windows with opening ratios of 10.16% and 19.05%. This analysis aims to apply the procedure for analysing the CM models by using layered shell elements and also comparing the behaviour and performance of each model. The masonry and frames were modelled using layered shell elements in SAP2000 software and analysis were done by using nonlinear static pushover analysis. This analysis starts by making a validation model based on other experimental work and comparing the behaviour of the structure modelled in the form of CM without openings and CM with openings. The results show that both models have load-displacement diagrams similar to the experimental results. By using the same modelling method applied to the analytical model, it was found that CM with large opening ratios have less strength than small opening ratios, and CM with centric openings was more robust than the eccentric openings.

In-Plane Loading Tests and a Retrofitting Technique for Masonry Infill Panels in RC Frames with Eccentric Openings

In-Plane Loading Tests and a Retrofitting Technique for Masonry Infill Panels in RC Frames with Eccentric Openings

The Effects of Eccentric Web Openings on the Compressive Performance of Pultruded GFRP Boxes Wrapped with GFRP and CFRP Sheets.

Pultruded fiber-reinforced polymer (PFRP) profiles have started to find widespread use in the structure industry. The position of the web openings on these elements, which are especially exposed to axial pressure force, causes a change in the behavior. In this study, a total of 21 pultruded box profiles were tested under vertical loads and some of them were strengthened with carbon-FRP (CFRP) and glass-FRP (GFRP). The location, number and reinforcement type of the web openings on the profiles were taken into account as parameters. As a result of the axial test, it was understood that when a hole with a certain diameter is to be drilled on the profile, its position and number are very important. The height-centered openings in the middle of the web had the least effect on the reduction in the load-carrying capacity and the stability of the profile. In addition, it has been determined that the web openings away from the center and especially the eccentric opening significantly reduces the load carrying capacity. Furthermore, when double holes were drilled close to each other, a significant decrease in the capacity was observed and strengthening had the least effect on these specimens. It was also determined that the specimens reinforced with carbon FRP contribute more to the load-carrying capacity than GFRP.

Limited subcatenous secondary sinuses excision in complex pilonidal sinus disease.

Introduction Pilonidal sinus disease (PSD) is a simple chronic inflammatory condition . Many surgical procedures used to treat pilonidal disease. In this study we represent a case series for treating complex PSD by Subcutaneous Sinusectomy and cystectomy.Patients and methods: Thirty five patients with complex PSD according Tezel classification were enrolled in the study. Marking of eccentric openings then an elliptical incision was done 1 cm from midline with 0.5 cm depth , all cases has a lateral remote openings from the midline we start dissection around the opening itself by a narrow ellipse then the side tracks palpated and we started subcutaneous dissection of the track then randveau dissection from the main midline wound to meet each other to extract the side track as one peace with main cyst. Results he studied group was 35 patients , 28 (80%) were males , 7 (20%) were females the mean age was 26±5.44 years with range 18-43 years. The mean operative time was 25.71 ±5.21 minutes with range 20-45 minutes, while the hospital stay was 28±5.32 hours with range 24-36 hours Recurrence occurred in 2 patients 5.71%. Primary non healing was the most common complication 5.71% . Conclusion: Subcutaneous Sinusectomy and cystectomy is a feasible and accepted option for management of complex PSD with a fair recurrence rate, short hospital stay and early return to work.

A new procedure to determine equivalent strut of infill walls with openings for engineering applications

In architecture, design of doors and windows for functional requirements, circulation, natural light and ventilation, aesthetics and view is inevitable. Parameters such as size, location and aspect ratio of the openings change the seismic behaviour of infilled frames. Ignoring these parameters in structural analysis may lead to substantial inaccuracy in predicting the lateral stiffness, strength and ductility of the frame. Despite numerous experimental and numerical studies on perforated infill walls in recent decades, the related provisions are rare in seismic codes and engineers tend not to use their results in analysis and design due to their complexity. The main purpose of this work was to propose a new procedure to determine the specifications of equivalent struts of perforated infill walls for engineering applications considering structural stiffness and load path based on valuable existing literature. All common types of windows used in architectural design (central openings, eccentric openings, corner openings and full-length openings) were investigated and the literature was reviewed for reduction factors of equivalent struts of infill walls with openings. Where there was a lack of studies, 27 micro models and 14 macro models were analysed to achieve the purpose of the research. A comprehensive and practical algorithm based on the size and location of openings is proposed.

An experimental investigation into the impacts of eccentric openings on the in-plane behavior of squat RC shear walls

Changing the use of an existing building may require removing some portions of its structural members, such as introducing door and window openings in the existing shear walls. Imposing these changes affects the structural performance of reinforced concrete (RC) shear walls, depending on the size and position of the openings. This study investigated the structural performance of three RC shear walls containing cut-out openings, with a special focus on increasing the opening eccentricity. Moreover, one reference RC shear wall (without any opening) was used to compare the impacts of the openings and their eccentricities. RC shear walls were loaded under reversed cyclic loading conditions, and the impacts of the eccentric openings on the load carrying capacity, stiffness, and energy dissipation were studied. The results showed that the creation of openings and imposing eccentricity significantly affect the failure modes in RC shear walls. It was also revealed that RC shear walls with openings immediately entered to softening behavior at the final stage of loading. The eccentric openings in squat RC shear walls increased the ductility of the RC shear walls. Moreover, it was noticed that the creation of openings greatly reduced cumulative energy dissipation.

Analytical estimation of lateral resistance of low‐shear strength masonry infilled reinforced concrete frames with openings

SummaryPresence of openings in an infill wall alters its behavior and reduces load resistance and stiffness of the infilled frame. In this paper, a simple method for estimating the lateral resistance of infilled frames with openings is proposed based on experimental data. Six half‐scale, single‐story single‐bay reinforced concrete frame specimens were tested under in‐plane lateral loading. The lateral strength of reinforced concrete (RC) frame could be estimated by assuming the formation of plastic hinges in the end regions of the members. In the specimens with central openings, the major load resistance mechanism of the infill panel was the formation of a compression strut and lateral strength of infill panel could be considered as the smallest values of the diagonal tension and corner crushing modes. In the specimens with eccentric openings, the load resistance mechanism of masonry infill was the formation of a compression strut and bed‐joint sliding in 2 opposite loading directions; thus, the lateral resistance of infill panel could be estimated in diagonal tension and corner crushing modes in one direction and bed‐joint sliding mode in another direction. Furthermore, the deformation capacity and structural performance levels are suggested for solid and perforated infill panels based on test observations.

A New Technique of Defining a Crossing Angle in Bicuspid Aortic Valve Stenosis

Introduction: Crossing bicuspid aortic valve (BAV) stenosis is challenging given the very eccentric opening of the valve. We describe a novel algorithm to define the plane of this eccentric orifice and our initial experience in aiding crossing the valve with a catheter and J-wire. Methods: Between 1st July 2015 and 28th Feb 2017, all BAV stenosis cases requiring transcatheter aortic valve implantation (TAVI) at St Andrew's War Memorial Hospital had a novel algorithm applied to their CT TAVI data with the aid of OsiriX MD medical software to determine a crossing angle pre TAVI. The plane of the virtual ring was determined by annular segmentation on multiplanar reformats and then points of interests (POI) placed along the circumference of the virtual ring. Immediately superior to this plane, POI were allocated along the commissural line. A three dimensional maximum intensity projection was then reconstructed to define the exact angle where the POI along the commissural line formed one point and the POI along the virtual ring plane formed a straight line. This angle showed both cusps in profile with the opening of the valves in the middle. Crossing times in this angle were then recorded at the time of TAVI. Results: 4 patients were included. A steep RAO Caudal view was always best for crossing. Using a catheter and straight wire, all valves were crossed in < 60 seconds. Conclusions: This unique technique for crossing BAV stenosis with the aid of CT reconstruction is feasible and may decrease xray and procedural time.

Flow field during eccentric discharge from quasi‐two‐dimensional silos–extension of the kinematic model with validation

A comprehensive investigation of granular discharge through the eccentric opening of rectangular silos has been presented. Slip flow of the grains over the vertical wall closer to the orifice was observed experimentally. This has not been emphasized by the earlier researchers. Considering slip flow at the wall, the kinematic model of granular discharge has been extended to simulate the hydrodynamics during drainage through any eccentric opening. The simulation is applicable over the entire range of eccentricity possible and for both the uniform and the triangular velocity profile through the orifice. Results from the experiments using sand grains (300–500 μm) and glass beads (400–600 μm) have been used for validating the model. The excellent agreement not only justifies the application of the kinematic model for eccentric discharge, it also extends the model for irregular and much smaller grain size. Finally, some limitations of the kinematic model have been examined critically. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1439–1453, 2016

Tubular flange plate girders with corner square web openings in the panel of maximum shear: Strength and behaviour

Eccentric web openings are usually unavoidable in the maximum shear panels of the girders used in offshore and bridge constructions. Hence, this paper is devoted to the investigation of their effects on the strength and behaviour of hollow tubular flange plate girders (HTFPGs), which were previously suggested in literature to enhance the lateral–torsional, flexural and shear strengths of plate girders. The finite element (FE) programme ABAQUS is currently used to generate parametric studies after validating the models by using the available experimental results in literature. These parametric studies have emphasised on four main parameters; namely, the depth of the tubular flange, the relative web opening size (d0/hw), the web plate slenderness and the opening location. The eccentric openings are located at the corners of the tension and the compression diagonals of the maximum shear panels of the considered HTFPGs. The results show that the tubular flanges bear a considerable amount of shear even if the web openings are existed. Also, it is found that locating the openings, as possible, in the corners of the compression diagonals becomes an effective solution to reduce the shear loss associated with the presence of openings in the HTFPGs compared to those located at the tension diagonal corners. For cases of openings of different sizes in the tension corners as well as large openings in the compression corners, the existence of the opening is shown to modify the behaviour near the opening compared to the opposite side of each girder at which the web is solid. On the opposite, small openings (d0/hw≤0.30) in the compression corners are found to have a minor effect on the girder's deformed shape and stress contour. It is, finally, found that the shear design model should consider the sum of the contributions of the flanges and the webs of the HTFPGs with eccentric web openings to accurately predict their strengths. However, several new conclusions on the shear strength and behaviour of the HTFPGs with eccentric web openings are presented.

A numerical model for the analysis of masonry walls in-plane loaded and strengthened with steel bars

A novel macro-model for the analysis of masonry shear walls reinforced with steel bar grids is presented. The model is based on the so-called disturbed state concept (DSC), with a modified hierarchical single yield surface (HISS-CT) plasticity model accounting for a distinct behavior in tension and compression. The effect induced by the introduction of different reinforcement ratios is discussed, in terms of increase of both failure load and ductility. With reference to a quasi-square shear wall, an optimal reinforcement ratio is evaluated by means of the numerical model proposed and subsequently compared with recommendations provided by the Canadian masonry design standard. The comparison shows how minimum values proposed by Canadian standard are suboptimal and hence not totally suitable to obtain a proper increase of the seismic performance of shear walls in high seismicity region. A second example, relying into a shear panel with eccentric openings and subjected to horizontal loads, is analyzed in detail. It is assumed to strengthen the structure by means of a light and a heavy reinforcement, to deeply investigate the role played by steel bars in masonry seismic upgrading. A new explicit formula is finally presented, useful to provide a quick estimation of the load carrying capacity of reinforced masonry, to be eventually used in common design.

OP-001 UNICUSPID AORTIC VALVE DUE TO CHRONIC INFECTIVE ENDOCARDITIS: A CASE REPORT

Figure 1. (A). Transesophageal echocardiograpic view of unicuspid aortic valve. (B) Short axis view of valve on TEE C. Microscopic examination reveals that there is a chronic inflammation process on the extracted valve. On transthoracic echocardiography, severe calcified and unicuspid aortic valve was demonstrated. In addition, the single commissure had fibro-calcific degeneration, with an eccentric opening. The patient undergone to cardiac surgery and performed aortic valve replacement with prosthetic valve. A unicuspid aortic valve (UAV) is a rare congenital defect that may manifest clinically as severe aortic stenosis or regurgitation in the third to fifth decade of life. In this case, we present an aquired unicuspid aortic valve due to subclinical infective endocarditis.

Investigation of the shear behaviour of multi-story reinforced concrete walls with eccentric openings

Four Reinforced Concrete (RC) single span structural walls having various opening sizes and locations were constructed and tested under lateral reversed cyclic loading at the structural laboratory of Kyoto University. These specimens were scaled to 40% and represented the lower three stories of a six-storied RC building. The main purposes of the experimental tests were to evaluate the shear behavior and to identify the influence of opening ratios on the cracks distribution and shear strength of RC structural walls. The shear strength of the specimens was estimated by combining the shear strength of structural wall without openings and the reduction factor that takes into account the openings. Experimental and analytical results showed that the shear strength was different depending on the loading direction due to opening locations. A two-dimensional finite element analysis was carried out to simulate the performance of the tested specimens. The constructed finite elements model simulated the lateral load-drift angle relations quite well.

Shear behaviour of reinforced concrete structural walls with eccentric openings under cyclic loading: experimental study

SUMMARYReinforced concrete (RC) structural walls usually have some eccentric large openings according to the intention of the architectural design. However, the behaviour of such structures that are shear critical under cyclic loading has not been well studied. In this study, three single‐span, three‐storied, 40% scale specimens of RC structural walls with various eccentric opening ratios were constructed and tested in a lateral reverse cyclic manner until severe shear damage occurred in the walls. The main purposes of these tests were to evaluate the shear behaviour and to recognize the influence of various opening ratios on cracking and shear strength of structural walls under cyclic loading. The shear strength of specimen was calculated combining the shear strength of a structural wall without openings and the reduction factor due to openings. The comparison between the experimental results and the analytical results shows that the shear strength is different depending on the loading direction due to the eccentric opening location, the span length of short span beams may affect the cracking process and the failure mode, the approximate calculation method using Ono's reduction factor could be well applied to RC structural walls with various opening ratios less than 0.46. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Experimental investigation of infilled r/c frames with eccentric openings

The influence of masonry infills with eccentric openings on the seismic performance of reinforced concrete (r/c) frames that were designed in accordance with current code provisions are investigated. Eight 1/3-scale, single-story, single-bay frame specimens were tested under cyclic horizontal loading up to a drift level of 4%. In all examined cases the shear strength of columns was higher than the cracking shear strength of solid infill. The parameters investigated include the shape and the location of the opening. Assessment of the behavior of the frames is also attempted, based on the observed failure modes, strength, stiffness, ductility, energy dissipation capacity and degradation from cycling loading. Based on these results there can be deduced that masonry infills with eccentrically located openings has been proven to be beneficial to the seismic capacity of the bare r/c frames in terms of strength, stiffness, ductility and energy dissipation. The location of the opening must be as near to the edge of the infill as possible in order to provide an improvement in the performance of the infilled frame.

The microanatomy of the alveolar duct of the human lung imaged by confocal microscopy and visualised with computer-based 3D reconstruction

The most widely accepted model of human lung alveolar duct systems is that they are constructed from central helical fibres between the turns of which lie alveolar openings. Experimental difficulties of handling and sectioning lung tissue have made it difficult to confirm this. Confocal laser scanning microscopy (CLSM) was therefore used to generate optical serial sections of the lung that were reconstructed in three dimensions and displayed using volume rendering techniques. From images of the reconstructions, a new structure is proposed in which alveolar ducts consist of collections of connected oval, twisted loop structures with eccentric openings.