Positive Moment Research Articles

Productive Failures: From Class Requirement to Fostering a Support Group

Mistakes occur frequently in mathematics. Reframing mistakes into positive moments can be psychologically important in a student’s educational journey. We investigated two tertiary math classes that explicitly valued mistakes through a pedagogical requirement called “productive failure”. For a percentage of their grade, students demonstrated how they made mistakes in their problem solving and, most importantly, how they overcame those mistakes. Through interviews, video-stimulated recalls, and evaluations of the course all from students, we initially looked for affectual responses to the pedagogical allowance and student-led demonstration. Many of the responses, both benefits and drawbacks of the productive failure, were interpreted by the research group to resemble the psychology literature on peer-led support groups. Descriptions of both productive failure and support groups, as well as quotes from the students, aim to shed light on psychological benefits of valuing mistakes. Finally, we believe that productive failures benefitted many students because it made the human aspect of mathematics more explicit.

A Proposal for a Simple Method for Determining the Concrete Slab Width of Composite Beam-to-Column Joints

Extensive brittle failures in the weld zone of the beam bottom flange in composite joints of SMRFs were observed during the Northridge earthquake and the Kobe earthquake. One of the main reasons is the large tensile strain demand generated at the beam bottom flange zone under positive bending. The key to accurately understanding the mechanical properties of composite joints is the effective width of the slab. However, researchers have no consensus on the flange slab’s effective width for composite joints, even with the simplest solid concrete slab. Therefore, the best way to design the composite joint specimen is by following the current design specifications. However, each specification implements different ideas and approaches for specifying an effective slab width. This paper presents comparisons of the effective flange width provisions in China, the United States, Australia/New Zealand, and the European Union. The characteristics of each provision are briefly described and summarized. Numerical comparisons for positive and negative moment regions of continuous spans follow. Based on the commonalities and main differences among all these provisions, we propose a recommended equation for calculating the effective width of a solid concrete slab, reflecting the specification differences. The reliability of the recommended equation was verified with ABAQUS software analysis. The recommended equation can meet the fast and secure design requirements for composite joints in tests with concrete slabs.

The marketing study of the pharmaceutical market of Ukraine in the segment of antihemorrhagic agents to stop dental bleeding

Aim. To conduct the marketing research of the Ukrainian market in the segment of antihemorrhagic agents used in dentistry.Materials and methods. The study was performed using the structural analysis, logical and graphical methods, marketing analysis methods.Results. The state of the Ukrainian market of drugs of this group has been determined. The market structure has been revealed in the number of names, brands, in forms of production, manufacturers, composition. Despite the sufficient number of registered drugs at the market (26 positions), a rather small arsenal of active substances (4) and dosage forms (3) can be observed. The market is characterized by a limited amount of drugs with a certain pharmacodynamics combining a rapid hemostatic effect, safety in use, the ability to suppress bacterial flora, and without the effect on healthy tissues. However, a positive moment should be noted: by the structure of manufacturer countries the market remains domestic (60 : 40).Conclusions. The Ukrainian pharmaceutical market is characterized by a sufficient assortment of hemostatic agents, but the use of these drugs in dentistry has its limitations. Dental doctors have certain problems with the occurrence of capillary bleeding and require a sufficient amount of effective and fastacting drugs for local application. Therefore, the search and creation of new drugs with a similar action at this stage remains a relevant scientific issue.

Методы удаленной работы и способы ее защиты

The topic of remote work with the arrival of the pandemic was an unusual way of working for many companies and organizations, but as time goes on, it continues to become more and more relevant and even becomes more convenient and applicable for different fields of activity. This form of organization of work has brought many innovations both in the work and in the organization of the protection of processed and transmitted information in the process of work. Both ordinary workers and managers faced a lot of problems, but also acquired a lot of positive moments. We will analyze the negative and positive aspects of "remote work" and methods of protecting the processed information in this process.

Comparative Study on Structural Behavior of Reinforced Concrete Straight Beam and Beams with out of Plane Parts

This paper aims to experimentally investigate and compare the structural behavior of reinforced concrete straight beam and other beams there made with one, two, and three out of plane parts. The study focused on the effect of the number and location of the out plane parts on the beams mid span deflection, and rotation, as well as the ductility index, cracking loads, and failure modes. Four beams were manufactured with a cross-sectional width of 150 mm and a depth of 200 mm, and 2000 mm in length. All the beams were made with normal strength concrete and constant longitudinal reinforcement ratio 0.011 for negative and positive moment. All the beam specimens were clamped by a special steel fixed ends and subjected to the two-point load up to their failure. The obtained results presented that the load bearing capacity of straight beam was higher than the beams with out of plane parts. Furthermore, the beam with two out of plane parts has capacity higher than the beams with one and three out of plane part by 5.86%, and 55.07%. In addition, the results showed that the ductility increased with increasing number of out of plane parts by 5.52%, and 32.71% as copared with the beam with one out of plane part.

Frame structure analysis model for the effect of typical tunnel diseases on lining structure

The frame structure analysis method has been generally applied for the tunnel structure design, which was widely utilized due to its fast calculation speed and convenient modeling. In this paper, the frame analysis model was established to explore the effect of typical tunnel diseases of voids and lining insufficient thickness on the mechanical and deformation behavior of concrete linings. At first, the lining model with the diseases of void and lining insufficient thickness was established in the frame structure analysis platform. Subsequently, the lining inner force (taking the bending moment as an example) and the deformation behavior were explored. At final, the differences in the deformation behavior were investigated with different vertical loading conditions. The main results in this paper revealed that when the vertical loosening pressure can be transferred to the lining structure within the void zone, the maximum positive bending moment of the lining is located near the crown, while the maximum negative is at the shoulder, and the phenomenon of internal bending mainly occurs in the void area, and the phenomenon of external bending occurs at the shoulder. The lining has a significant downward displacement at the crown, while the deformation direction of the structure is outward at the shoulder. However, when the vertical loading cannot be transferred to the lining within the void zone, the obvious phenomenon of deformation outwards will occur within the void zone.

Effects of Web Height Reduction and Skew Angle Variation on Behavior of RC Inverted T-Beams

The use of precast inverted T-beams has been frequently used to minimize construction activities and installation time. However, shipping and placement of large invert T-beams can become challenging tasks due to their weight. Decreasing the web height of the beam can be effective in reducing the beam weight. This paper considers inverted T-beams with two overhangs, negative moment regions, and one span, a positive moment region. The examined parameters were the web height and skew angle of the inverted T-beams. To avoid high costs of testing beams and to save time, the application of numerical modeling is, hence, inevitable. A calibrated 3D nonlinear numerical model, using ATENA software, was further used to numerically investigate the effects of reducing the weight, by decreasing the web height and varying the skew angle of inverted T-beams on their structural performance. The outcomes of this study indicated that reducing the web height of the beam was an effective tool to reduce the weight without jeopardizing the strength of the beams. Increasing the skew angle of the inverted T-beam also decreased their ductility.

Design equations for buckling strength of steel I-beam under non-uniform heating condition

This paper presents a numerical study on lateral-torsional buckling strength of the simply supported beam under fire subjected to general loading conditions. The influence of length to height ratio and the non-uniform temperature distribution in the steel beam was considered to evaluate the buckling strength of the beam. The numerical simulations were carried out by utilizing a commercial finite element program, ABAQUS. The buckling strengths of steel beams using buckling design curves at elevated temperature of Eurocode 3 Part 1–2 were also generated and compared. The results showed that the buckling resistance of the steel beam under fire using Eurocode 3 can give unconservative values for beams subjected to positive moment and give very conservative values for beams subjected to negative moment. The new correction factor was proposed to take into account the effect of length to height ratio and non-uniform heating condition on buckling strength. The proposal equation was suggested to determine the lateral-torsional buckling capacity of the steel beam under fire and general loading conditions.

The distribution of numbers with many ordered factorizations

Let g(n) be the number of ordered factorizations of n into numbers larger than 1. We find precise bounds on the positive moments of g. We use these results to estimate the number of n≤x satisfying g(n)≥x α for all positive α. In addition, let G(n) and g 𝒫 (n) be the number of ordered factorizations of n into distinct numbers larger than 1 and primes, respectively. We also bound the positive moments of G and g 𝒫 from below.

Numerical investigations on the influence of transverse beams and slab on the seismic behavior of substandard beam-column joints

The paper investigates the seismic performance of non-seismically designed reinforced concrete exterior and interior beam-column joints. The study focuses on the influence of transverse beams and slab on the sub-assemblies which are failing due to a joint shear failure. In the case of exterior joints, top and bottom longitudinal deformed bars of the loaded beam are anchored with a 90° bend in the joint, where no transverse reinforcement is available. The work is carried out in the framework of a 3D finite element analysis, where the microplane model with relaxed kinematic constraint is used for the constitutive law of concrete. First, the numerical approach is validated against an experiment from the literature carried out on an exterior edge joint with transverse beams and monolithically cast slab. The verification of the modeling approach is done in terms of cyclic load–displacement behavior and crack pattern. The validated modeling approach is then used to further analyze various configurations of exterior and interior joints without and with transverse beams and slab. The results of the numerical study show that the presence of transverse beams leads to an increased joint shear strength due to the confining action, whereas the slab substantially affects the flexural behavior of the loaded beam as well as the overall load transfer in the sub-assembly. It is found that the presence of slab leads to an unsymmetric load–displacement behavior under positive and negative moments, particularly when a relatively high effective slab width is contributing under negative moments. The results are evaluated to obtain the values of critical principal tensile stresses for joint shear strength that might be appropriate for the analysis of joints of different configurations considering the presence of transverse beams and slabs.

Numerical modelling of CFST column to I beam end plate joints

AbstractThe use of concrete‐filled tubular structural elements around the world has been boosted in recent years. The most common geometries for these sections are circular (CHS), Square (SHS) and rectangular (RHS). They have been extensively used in multi‐story buildings due to their aesthetical features and structural advantages, due to their favorable resistance to weight ratio. One of the limitations for using these geometries is the inaccessibility to the interior of the section, thus arising difficulties and added costs in materializing the connections. This paper presents a numerical study dealing with tubular columns to I beam end plate joints using welded studs as the connecting elements and aiming to evaluate their structural performance. Following a series of full‐scale monotonic tests performed at the Civil Engineering Department of the University of Coimbra, Portugal, with the abovementioned geometry, several numerical models using 3D nonlinear elements have been developed to investigate the mechanical response of these joints.The main variables were the column and beam geometries, the thickness of the hollow sections, and the presence or absence of infilling concrete. The numerical results have been compared to the tests performed under positive and negative bending moments, to validate the finite element model. The numerical model was proven to lead to accurate predictions of the initial stiffness and joint resistance. The model validation was followed by a parametric study with the abovementioned variables to investigate the influence of the governing components and behavioral features. The column face loaded out of its plane proved to be the governing component, with its width‐to‐thickness ratio having a significant role in determining both elastic stiffness and resistance, together with the endplate dimensions and the number of bolt rows in tension.

Behaviour of rectangular concrete filled tubular flange girders under combined loading

AbstractSteel‐concrete composite construction can provide an efficient structural solution by utilizing the two component materials to create a single effective composite section. The high tensile strength and ductility of steel combined with the excellent compressive strength and robustness of concrete results in an effective composite cross‐section which can be used in a wide variety of applications. There are a number of different shapes of composite beam, and this paper is focussed on a relatively new structural solution called concrete filled tubular flange girders (CFTFGs). These comprise a steel beam in which the top flange plate is replaced with a concrete‐filled hollow section. The compression flange can be any shape (e.g. circular, rectangular, and pentagonal) and the focus in the current paper is on simply supported girders with a rectangular section for the compression flange (i.e. RCFTFGs). These members have very high lateral torsional buckling resistance compared with conventional steel I‐girders of similar depth, width and steel weight and are therefore capable of carrying very heavy loads over long spans. However, they are complex to analyse and their behaviour is governed by several inter‐related parameters which are investigated and discussed herein. Given the most common applications of these girders, such as in bridges and carparks for example, they are frequently exposed to a simultaneous combination of high axial loads and bending moments. Although current design codes offer rules for the design of composite columns under combined loading, the design of RCFTFGs, which are asymmetric in nature under the combined effects of tension and bending, are not explicitly included. This work aims to investigate the ultimate strength of RCFTFGs with stiffened webs under the combined effects of various levels of axial tension and positive (sagging) bending moment. Nonlinear three‐dimensional finite element analyses using the ABAQUS computer software package have been developed to facilitate the study. The model is validated using available experimental data and then employed to conduct an extensive parametric study. It is shown that the moment capacity of RCFTFGs is reduced in most situations under the presence of an axial tensile force in the steel beam. In addition, the tensile capacity of the RCFTFGs is limited by the axial capacity of the steel beam alone, with little contribution from the concrete infill. Several influential parameters are examined and conclusions are discussed. Based on the finite element analysis, the moment–axial force interaction relationship is presented and discussed.

Mathematical Modeling of Linear Static and Dynamic Analysis for Pier Height Effect on the Structural Performance of Bridges Structures

The results of linear static analysis explained that the increasing of pier heights was leaded to rise the values of positive bending moment, tensile stresses, and downward vertical deflection. Whereas the compressive stresses and negative bending moment were decreased, indicating that the structural performance of bridge structure representing by stiffness, bearing capacity of structural members, and elasticity will decrease and the bridges structures will be damaged. Therefore, the bridges structures need safe design when using tall piers by adopting high quality materials such as high strength concrete, more steel reinforcement, more prestressed tendons, and increasing of cross section dimensions of girders and piers. The results of modal analysis show that the un-loaded dynamic frequency for three types of bridges models were decreased when the pier heights were increased, indicating that the stiffness of bridges structure was became low with higher pier height. According to response spectra and time history analysis results, the loaded dynamic frequency (vibration state) and dynamic displacement were increased when the pier heights were increased, showing that the bridge of structure will suffer from high vibration when the pier height was high. It can be concluded that from this study, the piers heights have significant effects on the static and dynamic structural performance of bridges structures under traffic loads.

Control strategies during fast turning manoeuvers - the free moment and its contribution to body rotation and joint loading

ABSTRACT The purpose of this study was to identify the relationship between ACL relevant knee joint loading and the free (reaction) moment during 90° sidestepping task. It was hypothesized that the specific movement strategy of an athlete will impact this relationship and therefore contribute to joint loading. Functional principal component and canonical correlation analysis were used to understand the nature of free moments and their interaction with 3D joint loading in 52 athletes. It was observed that the orientation of either a positive or negative free moment is associated with different orientations and location of the foot segment at initial touch down. This impacted the rotational moment that is transferred to the knee joint: A higher internal reaction moment is observed when athletes were exposed to a positive free reaction moment, which potentially increases the load on the ACL. Furthermore, the free moment predicted joint moments and joint reaction forces. The interpretation of the principal components identified the function of the free moment to control body rotation. Free moments of different orientation were generated during the same movement, which highlights the importance of investigating individual movement strategies to understand potential injury risk and control factors.

Effect of uniform temperature load on design of long reinforced concrete structures without expansion joints

This study presents an investigation on the design of long reinforced concrete (RC) structures subjected to uniform temperature load by considering three RC frame building models with different lengths of 45 m, 135 m, and 270 m using Etabs. The uniform temperature load is considered being the change from the annual average highest to lowest air temperature at the construction site in the case of unavailable temperature data of concrete. The analysis results indicate that the uniform temperature load mainly influences on the internal forces of RC members at storey 1 and slightly effects on the internal forces of RC members at storey 2. For short-length RC structures, the effect of temperature load can be ignored in the design of RC elements, whereas it must be taken into account in design of slab, beams and some column positions at storey 1 of medium-length and long RC structures without expansion joints. For the present RC frame building models, the required slab reinforcement in long direction increases about 33.4% for medium-length RC structures (135 m) and about 48.2% for long RC structures (270 m) without expansion joints. The required reinforcement for positive moment at mid-span increases from 33.7 to 39.4%, whereas the total required reinforcement for negative moment at the supports of beams increases from 19.4 to 34.9% in long direction of 270 m long RC structures without expansion joints due to uniform temperature load. Column design of long RC structures without expansion joints under uniform temperature load must be concerned, especially for columns in the corners.

Strengthening of Concrete Structures Using UHPC - Experimental Verification

UHPC is a material which exhibits excellent mechanical properties and durability. Beside new structures it is also convenient for strengthening of existing structures. The paper investigates the possibilities of strengthening experimentally. A part of the experimental program is presented which is focused on bond of UHPC and existing concrete and on behaviour in bending. Acceptable bond may be achieved when the existing concrete is clean and reasonably rough. Structural elements are exposed to positive and negative bending moments. If UHPC overlay is applied, it works in compression and in tension. The experiments were therefore focused on verification of both alternatives (UHPC in compression and in tension). Finally, the conclusions from the experiments are drawn, which may be applied in practical design.

Research on flexural behavior of composite box continuous girder with corrugated steel webs and trusses

A new type of composite structure, the composite box girder with corrugated steel webs (CSWs) and trusses, is proposed recently. In order to investigate the structural behavior under positive and negative bending moments, flexural tests of the continuous girder were carried out, and the failure modes, deformation patterns, strain distribution, and development of the concrete cracks were investigated. Finite element analysis was conducted to investigate the effect of the range of concrete in the steel tube and the thickness of CSWs on the flexural behavior. The experimental and numerical results show that the test beam has a good ductility and integrity under flexural load. The contribution of CSWs to the flexural bearing capacity is very small and can be neglected. Besides, the plane section assumption is still valid when only top concrete slab and bottom steel tubes are concerned. The concrete filled in bottom steel tubes increases the stiffness and the bearing capacity of the girder. Equations to calculate the flexural bearing capacity under positive and negative bending moments were put forward and then verified with experimental results.

Evaluation of Micropiles With Different Configuration Settings for Landslide Stabilization Based on Large-Scale Experimental Testing

In this study, a large-scale model test was performed to investigate the effect of the single-row and double-row micropiles on the landside stabilization. For two different testing configuration settings, the bending moment along the micropiles, failure mode, and force condition were captured and compared. It is found that the landslide thrust on piles was distributed in a triangular shape. The piles in the front row carried greater pressure than the piles in the rear row. The resistance of the sliding body behind the pile was distributed in a parabolic shape, and mainly concentrated on the middle of the pile. The piles were destroyed due to the combined shearing and bending impact applied near the slipping surface. The boundary of the failure zone was from the position of two times the pile diameter under the slipping surface to the position of two and a half times the pile diameter above the slipping surface. Under the action of the landslide, each row of piles deformed at the same time. The capability of landslide stabilization for double-row piles was better than that of a single-row pile. The sections of the pile above slide surface were mainly subjected to negative bending moments and were distributed mainly within the pile length range of one-third of the anti-sliding section above the sliding surface. The pile body of the embedded section located in the range of ten times the pile diameter below the sliding surface was subjected to a positive bending moment.

Thermally-activated shape memory alloys for retrofitting bridge double-angle connections

Double-angle connections are prone to fatigue cracking in old steel bridges; however, owing to their complexity, there are not many retrofitting solutions for these details. This study proposes a retrofitting system for double-angle connections using iron-based shape memory alloys (Fe-SMAs). An innovative connection test setup equipped with an optical 3D digital image correlation (DIC) measurement system was developed. The retrofitting system included two end-anchorages set on either side of the connection. Fe-SMA strips were inserted inside the anchorages, and then were thermally activated (pre-stressed) to a temperature of 260 °C. Numerical finite element studies were performed to investigate the static behavior of the system. It was found that the activated/prestressed Fe-SMA strips not only apply a reverse positive moment on the connection (versus an undesirable negative fixity moment), but also “absorb” a portion of the negative moment, owing to the added axial stiffness. The proposed SMA-based system offers a versatile and cost-effective technique (with quick and easy installation) for bridge connections, and can significantly reduce the effects from undesirable sources of fatigue cracking.

Metaphors of Life in German Idioms

The aim of the study is to define the metaphoric meaning of the concept ‘life’ in the German idioms. The German word das Leben means both to live and life in Georgian. It means German does not differentiate them. Our task is to define the positive and the negative connotations of idioms containing the concept of life/ live. To solve this task, we searched for the relevant phraseologisms in the dictionaries and classified them. The study has revealed that lexemes denoting seasons prevail in such idioms. In a metaphoric sense, we can show these idioms as a whole life cycle: from cradle to grave. The lexeme spring stands for youth years (Der Frühling des Lebens-the spring of life), while the lexeme autumn stands for the old age (Der Herbst des Lebens- the autumn of life). In the same figurative sense, the lexeme Lebenmay refers to one day only. For instance, Leben ist ein Tag – Life is one day. This phraseologism shows the brevity of life. Metaphorical compound Lebensabend means the evening of life, that is the old age. The brevity of life is also reflected in the idiom sein letztes Stündlein hat geschlagen- ‘his last hour struck’, meaning, his life came to an end. Metaphorisation of human’s life is also common with the following lexemes: plants, travel, road, food, struggle, liquid and vessel. Thus, life is alternation of positive and negative moments. The former are often compared to light and the sun, while the latter - to shade, darkness and night. Proceeding from this life is a regular alteration of light and darkness, the sun and shade, light and dark.