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Experimental testing of rc frames with isolated/decoupled infills: results and benefits
No full textArmiranobetonske ramovske konstrukcije sa zidanim zidovima su popularne zbog svoje brze izgradnje. Međutim, one često imaju loše seizmičke ponašanje zbog oštećenja ispune, što dovodi do skupih popravki i bezbednosnih rizika. Tradicionalni spojevi na bazi maltera lako bivaju oštećeni tokom zemljotresa, što dovodi do oštećenja i loma zidane ispune. Da bi se ovo rešilo, razvijen je i testiran inovativni sistem izolacije ispune, koji razdvaja ispunu od rama. Veza se sastoji od traka na bazi reciklirane gume. Sistem je eksperimetalno testiran na uzorcima u prirodnoj veličini. Početne prsline su otkrivene pri relativnom međuspratnom pomeranju nakon 2%, što dokazuje sprečavanje oštećenja ispune i smanjenje troškova popravke. Ovaj sistem nudi isplativo rešenje za povećanje seizmičke otpornosti i ekonomske prednosti smanjenjem potrebne količine armature i betona za AB elemente
Experimental investigation of bearing capacity of 3D printed concrete segmental girder
No full text3D concrete printing (3DCP) technology represents a new approach to producing contemporary concrete structures. The application of sophisticated equipment such as a 3D printer has brought numerous advantages, which were noted through significant practical application. Currently, 3DCP technology is being developed in two main directions: on-site production of entire structures and prefabricated construction. However, 3DCP technology has not yet reached its full potential in prefabrication as the connections between individual segments and their capacities under horizontal and vertical loads, have not yet been extensively investigated. This paper focuses on the experimental testing of the bearing capacity of a beam constructed by connecting individual segments of 3D printed concrete. The segments are connected using post-tensioning steel bars. The experimental program included testing a single segment as well as a segmental girder in a 3-point test. In the case of the individual segment, failure occurred due to the loss of tensile capacity of the concrete. For the segmental beam, failure occured when the shear capacity was reached. Shear fracture was accompanied by diagonal cracks extending from the point of force application towards the beam supports
Heavy damage to infills in the February 2023 Kahramanmaras earthquakes: Reasons and potential solution
No full textThe most dominant type of damage in the February 2023 Kahramanmaras earthquakes was the failure of masonry infill walls. The paper presents documentation of widespread damage observed during field visits. One of the reasons for such a heavy infill damage was the flexible configuration of RC frame structures. However, substantial infill damage was also noticed in cases of RC wall and dual systems. Usually, infills at the lower stories experienced out-of-plane collapse, demonstrating that in-plane/out-of-plane interaction is decisive for the level of infill damage. Therefore, this needs to be taken into account during the design. Field observations show that the infill/frame contact plays a major role in the behaviour of infills during earthquakes. It can be seen that mortar connection and other variations such as polyurethane foam are inadequate to provide out-of-plane restraint for the infill panels, and therefore so many infill walls have collapsed in out-of-plane. Due to the lack of infill isolation, despite being prescribed by the Turkish code, substantial in-plane damage occurred due to the deflection of the RC structure. This is also confirmed in a comprehensive experimental campaign documented in the paper. The main results of the 18 full-scale tests on infilled RC frames are summarized, highlighting the issues with traditional infill and its poor behaviour. An infill isolation system that provides in-plane decoupling and out-of-plane infill/frame connection is presented, along with the results of the experimental campaign. All potential benefits of the solution are summarized based on the comparison of the experimental results on traditional infills and isolated specimens
An introduction to data-driven modelling of the water-energy-food-ecosystem nexus
No full textAttaining resource security in the water, energy, food, and ecosystem (WEFE) sectors, the WEFE nexus, is paramount. This necessitates the use of quantitative modelling, which presents many challenges, as this is a complex system acting at the intersection of the physical- and social sciences. However, as WEFE data is becoming more widely available, data-driven methods of modelling this system are becoming increasingly viable. Here, we discuss two main problems in WEFE nexus modelling: system identification and control. System identification uses Machine Learning algorithms to obtain dynamical models from data and have shown promise in many disciplines with similar characteristics as the nexus. Meanwhile, control algorithms manipulate a system to achieve objectives and are becoming instrumental in shaping nexus policy. Despite the promise of these algorithms, data-driven modelling is a vast and daunting field, and so here we provide an introductory overview of this field, with emphasis on nexus applications
Comprehensive review of the structural behaviour and numerical modelling of recycled aggregate concrete-filled steel tubes
Get PDFThis paper summarises current research findings related to the behaviour and simulation of a relatively new type
of structural component: recycled aggregate concrete-filled steel tube columns (RACFST). The first part of the
paper presents a review of the latest experimental campaigns on RACFST columns subjected to a variety of
loading conditions. For each of loading condition, highlight observations about the behaviour of RACFST columns are presented. The second part of the paper provides a summary of numerical modelling approaches
developed for simulating the structural behaviour of RACFST columns. Special attention is paid to the selection
and calibration of material models for recycled aggregate concrete. Finally, directions for future investigations in
this area are outlined and discussed. The review will benefit researchers and professionals seeking to gain an indepth understanding of the behaviour of RACFST columns, and fills a gap in existing literature regarding a
number of practical issues related to the numerical modelling of these components
Static analysis of FGM plates using layer wise finite element
No full textIn limit state design, one of the limit states needed to provide structural safety under the design loads is the Ultimate Limit State (ULS). In ULS, as a computational condition, the strength or stresses field have to fulfil relevant design criteria, defined in the National Building Codes. Thus, the computation of stress as well as displacement field of plate structures, under static loading conditions, is the aim of this paper. After establishing the accuracy of the present layer wise (LW) model for linear and geometrically nonlinear bending, vibration and buckling analysis of laminated composite and sandwich plates subjected to mechanical and thermal load, as well as buckling and free vibrations of Functionally Graded Material (FGM) plates, in this paper, mechanical bending of FGM plates is presented. The mathematical model based on LW theory of Reddy, assumes layer wise variation of in plane displacements and constant transverse displacement through the thickness, linear strain displacement relations and linear orthotropic material properties. The properties of FGMs are assumed to be constant in xy plane and vary through thickness by power law function in terms of volume fraction of the constituent materials. The mathematical model includes the quadratic variation of transverse shear stresses within each layer of the plate. The principle of virtual displacement (PVD) is used to derive Euler-Lagrange differential equation of mechanical bending problem. In plane the weak form is discretized using nine node Lagrangian isoparametric finite element or 2D quadratic in-plane interpolation, while 1D Lagrangian interpolation is used for discretization through the thickness. The original MATLAB computer program is coded for the finite element (FEM) solution. The accuracy of the numerical model is verified by comparison with the available results from the literature. It is found that the effects of power low index affect the stress and displacement fields of FGM plates and should be taken into account when designing safe FGM plate like structures
On the application of independence tests to variable selection problems
No full textWe explore the potential of kernel-based generalizations of distance covariance for variable screening procedures. The flexibility of this association measure allows for the integration of models with spherical and hyperspherical data, which are commonly encountered in fields such as meteorology, geology, biology, and more. Through extensive empirical studies, we demonstrate the robustness and adaptability of our proposed method
The Future of Machine Control
No full textIn civil engineering, machine control refers to the use of advanced technology and equipment to automate and enhance the precision of construction processes. In order to assess the current situation and predict future trends in construction machinery control, several surveys of companies that use construction machinery were conducted. The research included European countries and companies of different sizes. Companies generally showed interest in the application of new technologies. The advantages of applying new systems for controlling the operation of machines are most often emphasized Accuracy, Efficiency and Sustainability and can bring a considerable advantage to companies when obtaining new business. However, the procedure and costs of introducing new technologies for small companies are still in the high risk zone, especially for small companies. The main obstacles to the introduction of new technologies are "lack of government initiatives and support for technology adoption" and "lack of buy-in from senior decision makers". Also, the lack of support from governments across Europe was recognized as an obstacle. The application of new technologies is also recognized as a strong incentive for the construction industry, with a great possibility of attracting young, qualified personnel. Despite everyone's belief that the implementation of new technologies can make a difference, executives in the construction sector cannot afford, financially and operationally, to invest in technologies from which they do not see an immediate return. Conducted research shows that this caution on the part of senior decision makers and the lack of support from policy makers were the main obstacles preventing the wider application of modern technological solutions
Vibration serviceability assessment of complex-shaped CLT floor
Get PDFCross-laminated timber (CLT) floors are typically an assembly of prefabricated panels connected together on the site. CLT offers a wide range of configuration possibilities, as it can be easily pre-cut into various shapes and sizes, making it suitable for use in different architectural design requirements. However, available CLT design guidelines do not apply to complex-shaped CLT floors, i.e. unconventional geometry of floor plans including concave polygons, arches and openings. This paper presents a numerical vibration analysis of such a floor with openings, which represents a standard floor structure for residential and commercial buildings. Influence of panel orientation and inter-panel connections on modal properties and vibration response induced by a single pedestrian walking is analysed and discussed
Discharge measurements at the tubular turbine intakes with EM current meters: Improvements of the procedure for the measurement uncertainty assessment
Get PDFU periodu od 2020. do 2023. godine korišćen je inovativni sistem za merenje i proračun protoka na prilazima cevnih turbina, na 6 (od 10) agregata HE Đerdap 2. Merenja su deo šireg skupa aktivnosti sa ciljem definisanja hidrauličke efikasnosti agregata, pre i posle revitalizacije. Međutim, upravo je merenje protoka tehnički najzahtevniji zadatak gde su i same merne nesigurnosti veće nego kod merenja ostalih hidrauličkih ali i električnih veličina. Kompleksnost mernog procesa u kome se koriste elektromagnetni senzori (EM) brzine kao i veći broj drugih merila fizičkih veličina koji funkcionišu na različitim radnim principima, diktira i složenost postupka proračuna merne nesigurnosti. Pored EM senzora, u mernom procesu se koriste i dva redudantna akustična Dopler senzora brzine, merila položaja rama i merila nivoa. Sva merenja su sinhronizovana sa lokalnim SCADA sistemom, tako da se u konačnom obračunu protoka koriste i odgovarajući podaci o radu turbine. Originalno je, na osnovu standardizovane procedure za procenu nesigurnosti u merenju protoka u otvorenim tokovima pomoću hidrometrijskih krila, razvijena specifična procedura za određivanje merne nesigurnosti protoka dobijenog primenom inovativnog mernog sistema. Međutim, iskustva sa terena su ukazala da je varijacija nivoa slobodne površine, tokom jedne merne sesije, zanemarljiva, pa je predložena nova procedura za proračun merne nesigurnosti koja se oslanja na standardizovanu metodu obračuna nesigurnosti pri merenju protoka u zatvorenim tokovima, primenom hidrometrijskih krila. U ovom radu je predstavljena novorazvijena metoda, a posebno su apostrofirane razlike u odnosu na prethodno korišćen pristup. Analizirani su i rezultati dobijeni za merenja sprovedena u 2023. godine, sa osvrtom na dominantne komponente merne nesigurnosti.From 2020. to 2023. an innovative discharge measurement system, based on electromagnetic (EM) velocity sensors, was used on 6 (out of 10) turbines of HPP Iron Gate 2. Discharge measurements were a part of a group of activities used to define the turbine hydraulic efficiency, before and after the revitalization. However, performing discharge measurements is technically most complex activity, where the measurement uncertainty values are higher than within the measurement of other hydraulic and electrical parameters. The complexity of the measurement process, associated with the larger number of different sensors measuring different parameters, imposes the complexity of the uncertainty assessment procedure. In the measurement process, besides EM sensors, two redundant acoustic Doppler velocimeters, shaft encoders and level sensors are used. The measurements are synchronized with local SCADA system, hence in the final discharge value assessment, data from turbine monitoring system are utilized. During the first measurement campaign a specific uncertainty procedure was tailored for the flow measurements, based on the standard uncertainty assessment procedure used for the discharge measurements in rivers with current meters. However, field data implied that the free surface level variations during one measurement are negligible, hence an additional procedure was proposed, now based on the standard procedure for current meter discharge measurements in full closed conduits. In this paper, the newly developed procedure is described with particular emphasis on the differences between the two methods. Discharge measurement results from 2023. are analyzed and key uncertainty contributing components are identified