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Bending behaviour of cross laminated timber panels made from locally sourced spruce wood
Get PDFCross laminated timber (CLT) is relatively new engineering wood product made by gluing cross-wise layers of solid timber boards to form large-scale panels. Due to excellent in-plane and out-of-plane resistance, CLT panels have become very common as wall and floor structural elements. CLT is validated as an excellent alternative to more traditional construction materials like reinforced concrete and steel for use in single- and multi-storey buildings.
This paper presents an experimental study conducted on five-layer CLT panels manufactured using spruce boards. The panels were tested in four-point bending configuration, loaded in the out-of-plane direction. Bending behaviour of CLT panels in the major axis orientation was evaluated through failure modes, load-deflection relationship, ultimate moment capacity, stiffness and strain distribution profile. The obtained experimental results indicated brittle failure modes and linear load-deflection relationship up to failure. In addition, strain distributions of panels were quite linear during the entire loading, confirming the assumption that plane sections remain plane after bending.
Bending response of CLT panels was also investigated using finite element modelling. The stress and deflection analysis was executed in the RFEM software using the RF-LAMINATE module. The calculation was carried out according to the laminate theory, taking into account shear coupling of layers. A good agreement between the results of numerical model and experimental investigation was found
Behaviour of masonry infills with door openings under sequential in-plane and out-of-plane loading
Get PDFReinforced concrete (RC) frame structures with masonry infills are common in seismic-prone regions. Masonry infills are activated in in-plane and out-of-plane directions under seismic loading and often damaged during earthquakes. Several recent investigations have shown that the combined effects of in-plane and out-of-plane loads are particularly dangerous for masonry infills. However, most of these studies focused on solid infills, and there is little information about the influence of openings on the seismic performance of infills, even though openings may alter the seismic performance of infilled frames significantly. This paper presents results of two experimental tests carried out on masonry infills with full-height door openings. One was tested under pure out-of-plane load, and the second one with sequential in-plane and out-of-plane loads. Thereafter, results of these two tests are compared with experimental findings obtained from two experimental tests with similar loading protocol conducted on solid masonry infills. Results of the study demonstrate the deteriorating effect of door openings, especially under combined in-plane and out-of-plane loads. The results also highlight a need for practical solutions for damage prevention in both infills with and without openings
Ispitivanje uticaja broja orijentacionih tačaka na geometrijsku tačnost UAV fotogrametrijskih proizvoda formiranih pomoću pristupa strukture iz pokreta
No full textThe positional and vertical accuracy of UAV aerial photogrammetry products generated using the Structure from Motion (SfM) approach depends on various factors, such as flight plan parameters, camera quality, camera calibration, the SfM algorithm used, and the georeferencing process. The influence of the quantity of Ground Control Points (GCPs) on the geometric quality of generated models and the stability of camera calibration parameters assessed through self-calibration in the blockaerotriangulation process was investigated in this study. Three software systems were used to process the collected UAV photogrammetry images: Pix4D Mapper, Agisoft Metashape, and Trimble Inpho UASMaster. Standard statistical quality assessments were employed to assess the accuracy of the blockaerotriangulation. The research findings indicate that augmenting the quantity of GCPs enhances model reliability and decreases the RMSE values of vertical deviation on the control points. The RMSE values of vertical deviation on the check points for all three used software systems converged to approximately twice the value of the average spatial resolution. Additionally, the RMSE values of positional deviation on check points converged to the value of the average spatial resolution
Research in computing‑intensive simulations for nature‑oriented civil‑engineering and related scientific fields, using machine learning and big data: an overview of open problems
No full textThis article presents a taxonomy and represents a repository of open problems in computing for numerically and logically intensive problems in a number of disciplines that have to synergize for the best performance of simulation-based feasibility studies on nature-oriented engineering in general and civil engineering in particular. Topics include but are not limited to: Nature-based construction, genomics supporting nature-based construction, earthquake engineering, and other types of geophysical disaster prevention activities, as well as the studies of processes and materials of interest for the above. In all these fields, problems are discussed that generate huge amounts of Big Data and are characterized with mathematically highly complex Iterative Algorithms. In the domain of applications, it has been stressed that problems could be made less computationally demanding if the number of computing iterations is made smaller (with the help of Artificial Intelligence or Conditional Algorithms), or if each computing iteration is made shorter in time (with the help of Data Filtration and Data Quantization). In the domain of computing, it has been stressed that computing could be made more powerful if the implementation technology is changed (Si, GaAs, etc.…), or if the computing paradigm is changed (Control Flow, Data Flow, etc.…)
Uticaj prslina na trajnost armiranobetonskih konstrukcija
Get PDFPojava prslina dovodi do narušavanja strukture zaštitnog sloja betona i do ubrzanja transporta štetnih materija, čime utiču na trajnost armiranobetonskih (AB) konstrukcija. Kroz sveobuhvatni pregled literature, zaključeno je da deterioracija AB konstrukcija izazvana karbonatizacijom predstavlja jedan od glavnih problema trajnosti širom sveta. Za potrebe ispitivanja, u okviru doktorske disertacije, spravljeni su referentni beton, beton sa 50% letećeg pepela (LP) i beton sa 100% recikliranog agregata (RA). Analizirani su postojeći modeli predikcije dubine karbonatizacije i predložena je njihova modifikacija u slučaju betona sa RA i LP. Ustanovljena je veza između karbonatizacione otpornosti i čvrstoće pri pritisku na osnovu koje je izvršena analiza upotrebnog veka kroz definisanje debljine zaštitnog sloja različitih vrsta betona. Za potrebe ispitivanja uticaja prslina na upotrebni vek spravljeni su uzorci sa 5 različitih širina prslina (0.05, 0.10, 0.15, 0.20 i 0.30 mm) kao i referentni uzorci bez prslina. Na kraju, predloženo je ograničenje napona u armaturi čime se omogućava da celokupni upotrebni vek (period inicijacije i propagacije) AB konstrukcija zadovolji propisane zahteve trajnosti
Модел за детекцију и анализу узрока кашњења на пројектима базиран на подацима издвојеним из неструктурираних извора
Get PDFПрекорачење рокова на грађевинским пројектима представља глобални
феномен који се истражује већ деценијама. Традиционални приступ детекцији
и анализи узрока кашњења најчешће подразумева прикупљање искустава
експерата везано за групе сродних пројеката (по врсти или географској
локацији). Резултат таквог приступа је листа узрока кашњења хијерархијски
поређана према њиховом значају. Таква емпиријска истраживања су
неминовно обојена субјективизмом и пристрасношћу експерата и не доводе до
утврђивања који су то базни узроци кашњења (root causes of delay) на нивоу
појединачног пројекта.
У циљу приказа наведених слабости традиционалног приступа, као и због
стварања основе за дефинисање и каснију валидацију новог приступа,
прикупљени су подаци са 75 пројеката путне инфраструктуре који су
реализовани у Србији у периоду од 2004. до 2021. године и формирана је
одговарајућа база података. Резултати истраживања и анализе података из
базе указују да је преко 80% пројеката имало кашњење док је просечно
прекорачење износило више од 90% уговореног трајања. На основу спроведене
анкете кључних учесника на пројектима из базе, формирана је листа узрока
која не одступа у односу на већину студија. При томе, добијене су ниске
вредности Spearman-овог ранга корелације (0,204 - 0,565) између ставова
различитих учесника, што потврђује значајно присуство субјективизма и
пристрасности у спроведеним емпиријским истраживањима (анкетама).
Главни циљ докторске дисертације је формирање новог модела за
непристрасно откривање базних узрока кашњења на нивоу појединачног
пројекта и његових физичких целина, применом машинског учења на
неструктурираној текстуалној документацији са пројекта. Изабрани
текстуални документи за развој модела су записници са састанака (Minutes of
Meetings), зато што они садрже свеобухватне информације о кашњењима,
настале у време настанка проблема и то са прецизном временском
одредницом. Технике машинског учења, користећи Transformer језичке моделе,
омогућавају аутоматску детекцију узрока кашњења. Фокусирано експертско
знање се користи за додатно непристрасно обучавање модела за изабрани
домен путне инфраструктуре, повезивањем делова текста са узроцима
кашњења из претходно дефинисане листе. Препознате физичке целине путних
инфраструктурних пројеката су: тунел, траса и мост. Комбинујући наведене
елементе, у дисертацији је развијен аналитички Модел за детекцију и анализу
узрока кашњења на грађевинским пројектима путне инфраструктуре, назван
DREAM (Delay Root-causes Extraction and Analysis Model).
У првој фази, DREAM аутоматски генерише листу детектованих узрока
кашњења по пројектним целинама, засновану на учесталости њиховог
viii
појављивања у записницима са састанака. Резултати показују да је модел у
стању да детектује узроке кашњења са задовољавајућим вредностима одзива
(recall =0,69, за најучесталије узроке кашњења).
У другој фази, DREAM, захваљујући временској компоненти записника,
омогућава потпуно нову и јединствену функционалност - графичку
презентацију временске дистрибуције узрока кашњења током пројекта.
Квалитативном анализом информативних графикона који показују учесталост
и интензитет појединачних узрока кашњења, стручњаци могу да разумеју
природу проблема и открију базне узроке кашњења (root causes of delay), што
је кључни циљ свих истраживања о кашњењима на грађевинским пројектима.
Спроведено истраживање пружа научни и стручни допринос. Предложен је
нов приступ идентификацији и анализи узрока кашњења, кроз развијен
аналитички модел базиран на текстуалним подацима, машинском учењу и
фокусираној употреби експертског знања. DREAM превазилази недостатке
традиционалног приступа приликом формирања листе узрока кашњења, и
омогућава откривање базних узрока кашњења применом јединствене
функционалности – временске дистрибуције узрока кашњења. У стручном
смислу, предложени модел пружа непристрасну помоћ при реконструкцији
догађаја који су проузроковали кашњење на нивоу појединачног пројекта и
његових целина, што доприноси смањењу спорова између уговорних страна и
помажу приликом интелигентног доношења одлука на будућим пројектима
Performance of reinforced concrete buildings in the February 6, 2023 Türkiye earthquakes
Get PDF: The paper discusses consequences of the February 6, 2023 earthquake sequence (a M 7.7 earthquake with epicentre in Pazarcik, followed by a M 7.5 earthquake with epicentre in Elbistan) which affected south Türkiye and northwestern part of Syria. The earthquakes caused more than 56,000 fatalities. More than 230,000 buildings experienced severe damage or collapse, while additional 40,000 buildings experienced moderate damage. The focus of the paper is on the performance of reinforced concrete buildings, which are prevalent in the affected area. The causes of structural damage are discussed in the context of the local codes, and in design and construction practices. Extensive non-structural damage was observed in these buildings, and it was caused by flexible RC frame system and inadequate amount of RC walls. The topic is relevant for Serbia since reinforced concrete is prevalent technology for buildings in our country, and some similarities in construction practices exist in Serbia and Türkiye
Shear behaviour of demountable connections with bolts and headed studs
No full textFollowing the trend of sustainable development and structure reuse, many novel solutions related to demountable shear connectors for application in steel-concrete composite beams have been proposed in recent years. This paper provides a further contribution to the research field by proposing a demountable connection with bolts and welded headed studs. The transfer of shear force between a steel flange and a composite concrete slab cast in an open trough profiled steel sheeting is indirect, passing through a steel plate or angles. The proposed solution enables convenient dismantling and reuse of both the composite slab and the steel profile. The experimental investigation included push-out tests, performed to assess the connection shear behaviour, determine resistance and ductility, and identify failure modes. Various configurations of the demountable connection were analysed, including connections with continuous and discontinuous slabs over the support. The response of the suggested demountable solution was compared to the corresponding non-demountable shear connection with headed studs. According to experimental investigation, finite element models were developed, and their accuracy was validated by comparing numerical predictions with experimental results. Parametric studies were conducted using numerical models to evaluate the effects of key parameters on the connection performance, such as plate and angle thickness, stirrup reinforcement position, and transverse distance between a headed stud and slab edge. Directions for design were proposed taking into account the results obtained
Thick Resistive Film Application on Steel Bars for Structural Health Monitoring
No full textThis paper aims to examine the applicability of thick-film piezo-resistive sensors on steel bars for the structural health monitoring purposes. A thick film ceramic piezo-resistive sensor was manufactured and used to investigate the possibility of its application on a bar. To form the device, Bi2Ru2O7 resistive thick-film composition was used in combination with Pd/Ag conductive composition on alumina ceramic substrates. Six conductive pads divided the resistor into seven identical segments. Sensor was subjected to a three-point bending test. After it was glued to a steel bar like a common foil strain gauge, a four-point bending test was performed on a sensor placed on the upper side of the bar. Under strain, sensor experienced reversible deformation that was registered as a change in the resistivity of the film. Evaluation of the sensor included measurements of the resistance change under the applied strain, determination of the gage factor and investigations of its physical integrity and temperature stability