Structural Steel Joints with Bolts in Threaded Holes

The application of tubular columns in steel structures offers many advantages. However, this potential has not been fully utilized due to a lack of access for the installation of standard bolts in end-plate beam-to-column joints. Blind bolts are an alternative way of connecting the beam end-plate to hollow section column, for they can be installed and tightened from outside of the column. Standard high strength bolts can be directly screwed into the threaded hole tapped in the column hole wall. Bolts in threaded holes (BTH) - use threads on the bolt hole wall as an anchorage instead of nuts used in standard bolt assemblies. Provisions regarding BTH can be found in the draft version of new Eurocode 3, Part 1-8, including the definition of minimum thread engagement lengths. Parametric study of beam-to-tubular column joint with extended end-plate was conducted in order to analyse the influence of BTH and specific failure modes on overall joint resistance. Minimum thread engagement length limitations were checked for all considered combinations of parameters, and based on these results, an overview of the general applicability of bolts in threaded holes was gained

PSYCHOLOGICAL EFFECTS OF INDOOR AIR POLLUTION

Office buildings need to provide clean, cozy and comfortable working environment with good indoor air quality in order to create favorable conditions for psychological and physical functioning. Most people are not satisfied with the quality of air in an enclosed office space, which is one of the factors that affect people’s work, productivity and stress levels. Indoor air pollution reduces person's ability to respond to the demands of the environment, which often leads to fatigue, malaise, anxiety, headaches, mental confusion, reduced mental and physical performance, as well as irritation of the eyes and throat, coughing and wheezing. The outcomes of exposure to air pollution is largely mediated by the intervening perceptive and cognitive processes that shape behavioral and health responses to stressors. Longer exposure to pollutants can lead to behavioral and mood changes, personality changes, impaired memory, slower motor responses and other functional deviations. Poor indoor air quality can cause diseases such as "sick building syndrome" mass psychogenic illness, and environmental diseases caused by the influence of environmental stress

IMPLEMENTATION AND TESTING OF WEBSOCKET PROTOCOL IN ESP32 BASED IOT SYSTEMS

This paper gives insight on the WebSocket communication methodin Internet of Things system, where the hardware part of the system is based on ESP32 microcontroller. Method of implementation is discussed and the reliability of the real-time data transfer in Wi-Fi networks is tested and compared with the long-polling method. Special circuit is designed with the goal to stress the hardware part of the system and the client-server communication link in order to enable proper comparison of data transfer methods. For the comprehensive testing of the real-time data ow, a web server application is designed and used to visualize received data. Impact of RSSI on transfer methods is discussed as well. Eciency of the WebSocket method is discussed and then compared to the long-polling method

Phytochemical and Antioxidant Properties of Fresh Fruits and Some Traditional Products of Wild Grown Raspberry (Rubus idaeus L.)

The current study investigated and compared phytochemical and antioxidant activity of fresh fruit and some traditional products of Rubus idaeus grown in mountain region of Serbia. The total organic acid, total sugar content, total phenolics, flavonoids, tannins, anthocyanins and vitamin C were evaluated. The antioxidant activities were evaluated using two antioxidant systems 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). The fresh fruit contained highest amount of vitamin C (46.62 mg AA g(-1)) and total organic acids (882.22 mg CA g(-1)). The sweet preserve had highest content of total phenolics (200.83 mg GA g(-1)), flavonoids (12.85 mg RU g(-1)) and tannins (39.11 mg g(-1)). The juice had the highest total anthocyanin content (107.22 mu g mL(-1)) and total sugar content (25 degrees Brix). The best antioxidant activity in ABTS assay had juice (IC50 = 4.87 mu mol TE g(-1)), followed by sweet preserve (IC50 = 5.14 mu mol TE g(-1)), almost identical to standard gallic acid. In the DPPH free radical scavenging assay, sweet fruit preserve showed significant better antioxidant activity (IC50 = 41.27 mu g mL(-1)) compared to juice (IC50 = 106.07 mu g mL(-1)) and fresh fruit (IC50 = 294.79 mu g mL(-1)). Our results indicated promising perspectives for usage of R. idaeus fresh fruits and traditional products studied with considerable levels of vitamin C, bioactive compounds and antioxidant activity

Analysis of the Frequency of Verbal and Vocal Signs in True and False Statements

The paper presents research aimed at analysing the frequency of verbal and vocal signs in a situation of false and true statements, by introducing a secondary task. The research involved 100 students (47 men and 53 women) of the master's studies of criminal investigation at the University of Criminal Investigation and Police Studies, aged 23-44. Students had the task, based on the observation of twenty selected videos (10 true statements and 10 false statements), to mark the frequency of each individual verbal and vocal sign, on a previously generated and prepared list. The results show that there is a statistically significant difference in terms of the frequency of all verbal and vocal signs in a false or true statement: response latency, speech hesitation, speech errors, speech rate, number of spoken words in the utterance, and length of utterance. Response latency, speech hesitation, and speech errors have higher median values in false utterances than in true ones, while speech rate, number of words spoken, and length of utterance show higher median values in true than false utterances

Savremena rešenja podužnog smičućeg spoja kod prefabrikovanih spregnutih konstrukcija od čelika

Prefabrication of steel-concrete composite decks can improve their competitiveness and sustainability. This paper presents recent studie of longitudinal shear connection at the University of Belgrade, Faculty of Civil Engineering. Grouped welded headed studs and bolted shear connectors, suitable for prefabricated composite construction, has been examined in push-out tests. Totally 30 tests were conducted, and advanced Finite Element Analysis (FEA) were made using Abaqus/Explicit dynamic solver. Influence of the bolt-to-hole clearance in case of the composite beam with bolted shear connectors is examined using FEA, as well. Based on the experimental and numerical studies behaviour those two shear connectors are compared.Prefabrikacijom spregnutih konstrukcija od čelika i betona može se povećati njihova konkurentnost i smanjiti uticaj konstrukcije na životnu sredinu. Ovde su prikazana istraživanja podužnih smičućih spojeva koja su nedavno sprovedena na Građevinskom fakultetu Univerziteta u Beogradu. Rešenja podužnog smičućeg spoja sa grupisanim moždanicima sa glavom i zavrtnjevima kao sredstvima za sprezanje koja su pogodna za prefabrikaciju spregnutih konstrukcija su ispitivana standardnim eksperimentom smicanja. Eksperimentalno je ispitano ukupno 30 uzoraka i vršene su analize na bazi MKE korišćenjem softverskog paketa Abaqus/Explicit. Primenom MKE analizirano je i ponašanjenosača sa zavrtnjevima kao sredstvima za sprezanje i uticaj zazora između rupe i zavrtnja. Na bazi eksperimentalnih i numeričkih ispitivanja izvršeno je poređenje ponašanja ova dva sredstva za sprezanje i razvijene su nove preporuke za proračun i konstruisanje

Savremena istraživanja smičućeg spoja prefabrikovanih spregnutih greda od čelika i betona

Prefabrication of steel-concrete composite decks can improve their competitiveness and sustainability. This paper presents recent studies of longitudinal shear connection at the University of Belgrade, Faculty of Civil Engineering. Grouped welded headed studs and bolted shear connectors, suitable for prefabricated composite construction, has been examined in push-out tests. Totally 30 tests were conducted, and advanced FEA were made using Abaqus/Explicit dynamic solver. Based on the experimental and numerical studies behaviour those two shear connectors are compared.Prefabrikacijom spregnutih konstrukcija od čelika i betona može se povećati njihova konkurentnost i održivost. Ovde su prikazana istraživanja podužnih smičućih spojeva koja su nedavno sprovedena na Građevinskom fakultetu Univerziteta u Beogradu. Grupisani moždanici sa glavom i zavrtnjevi kao sredstva za sprezanje koja su pogodna za prefabrikaciju spregnutih konstrukcija su ispitivani standardnim eksperimentom smicanja. Eksperimentalno je ispitano ukupno 30 uzoraka i vršene su analize na bazi MKE korišćenjem softverskog paketa Abaqus/Explicit. Na bazi ekserimentalnih i numeričkih ispitivanja izvršeno je poređenje ponašanja ova dva sredstva za sprezanje

Savremena rešenja podužnog smičućeg spoja kod prefabrikovanih spregnutih konstrukcija od čelika

Prefabrication of steel-concrete composite decks can improve their competitiveness and sustainability. This paper presents recent studie of longitudinal shear connection at the University of Belgrade, Faculty of Civil Engineering. Grouped welded headed studs and bolted shear connectors, suitable for prefabricated composite construction, has been examined in push-out tests. Totally 30 tests were conducted, and advanced Finite Element Analysis (FEA) were made using Abaqus/Explicit dynamic solver. Influence of the bolt-to-hole clearance in case of the composite beam with bolted shear connectors is examined using FEA, as well. Based on the experimental and numerical studies behaviour those two shear connectors are compared.Prefabrikacijom spregnutih konstrukcija od čelika i betona može se povećati njihova konkurentnost i smanjiti uticaj konstrukcije na životnu sredinu. Ovde su prikazana istraživanja podužnih smičućih spojeva koja su nedavno sprovedena na Građevinskom fakultetu Univerziteta u Beogradu. Rešenja podužnog smičućeg spoja sa grupisanim moždanicima sa glavom i zavrtnjevima kao sredstvima za sprezanje koja su pogodna za prefabrikaciju spregnutih konstrukcija su ispitivana standardnim eksperimentom smicanja. Eksperimentalno je ispitano ukupno 30 uzoraka i vršene su analize na bazi MKE korišćenjem softverskog paketa Abaqus/Explicit. Primenom MKE analizirano je i ponašanjenosača sa zavrtnjevima kao sredstvima za sprezanje i uticaj zazora između rupe i zavrtnja. Na bazi eksperimentalnih i numeričkih ispitivanja izvršeno je poređenje ponašanja ova dva sredstva za sprezanje i razvijene su nove preporuke za proračun i konstruisanje

Shear connection with groups of headed studs

Ponašanje i karakteristike predgotovljenih spregnutih elemenata konstrukcija od čelika i betona određeni su ponašanjem uzdužnog posmičnog spoja. Grupe moždanika s glavom najčešće se koriste za formiranje uzdužnog posmičnog spoja predgotovljenih spregnutih nosača. U radu su prikazani rezultati eksperimentalnih istraživanja i naprednih numeričkih modela posmičnih spojeva, koji su ostvareni grupama moždanika s glavom. Kada se moždanici izvode u grupama, preporuka je da se koriste veće visine od 4d koja je propisana europskom normom.The behaviour and characteristics of the elements of prefabricated composite steel and concrete structures are determined by behaviour of the longitudinal shear connection. Headed studs in groups are most frequently used for forming longitudinal shear connection of prefabricated composite beams. The results of experimental research and advanced numerical models of shear connections, obtained using groups of headed studs, are presented in the paper. When headed studs are arranged in groups, it is recommended to use the headed studs with the height greater than the 4d height prescribed by the Eurocode