Optimization of purlins cross-section exposed to fire

In practice, consideration of fire protection for structural elements mainly occurs after the adopted dimensions of sections. However, this procedure leads to not the most cost-effective solution in general. To find the optimal solution, it is necessary to apply one of the optimization methods. The presented optimization of purlins RHS cross-section is performed with nonlinear programming available in widely used program Excel. The objective function is defined as producing the purlin at a minimal price, considering the price of steel, work, and fire-resistant paint. Limits are introduced to ensure the cross-section satisfies the ultimate limit state for permanent and transient load situations, as well as in case of fire. Besides the ultimate limit states, the limits are defined for serviceability limit states and for cross-sectional geometry. Optimization analysis for different ISO 834 fire durations is followed by a result comparison. It provides an overview of cross-sectional parameters that most influence the bearing capacity in case of fire. It is concluded that by increasing the exposure time to fire, the optimal solution becomes a section with a smaller perimeter, larger surface area, and a thicker layer of fire-resistant coating

Plastic bending resistance of composite beams according to second generation EUROCODE 4

The paper discusses changes related to the calculation of the plastic resistance moment of a composite beam according to the second generation Eurocode 4. An efficient algorithm for determining the resistance moment through nonlinear analysis is presented, considering the limitation of compression strain in concrete. A comparison of results obtained using the first generation Eurocode 4 with calculation methods based on the second generation Eurocode 4 (rigid-plastic and nonlinear analysis) is conducted for a characteristic cross-section of a beam with a steel I-profile coupled with a solid concrete slab using ductile connectors and a full shear connection

Towards camera-based sewer discharge monitoring: experiences using a low-cost DIY setup

• Camera-based velocimetry can be viable alternative for discharge measurements in sewers. • Computer vision algorithms were employed for the automatic generation of rating curves. • Environmental conditions can have a considerable impact of the data accuracy and reliability

Seismic protection and vibration control in laboratory buildings - Biosense in Novi Sad

In Novi Sad (Serbia), a new state-of-the-art research building is being constructed for the Biosense institute. It consists of multiple building parts with laboratories, workshops, offices and a lecture hall. Sensitive laboratory equipment is placed in a special four-storey RC-building section which has to meet strict requirements for earthquake resistance and vibration control. This section is decoupled from the rest of the building and rests on base-isolation which serves as seismic protection and is supplemented by isolation against structure-borne noise, which is needed to maintain a low level of vibration. Also, vibration dampers were installed to reduce the movement of the structure in the event of an earthquake. With the start of the project, SDA-engineering has been involved in the structural dynamic topics. This included the conceptual design of the structural measures and the investigation and measurement of possible sources of vibration. For a precise adjustment and evaluation of these measures, simulations were carried out, before, during and after construction. This includes FE calculations, which were validated with vibration measurements. In this way, the natural frequencies and modal shapes of the laboratory section could be precisely determined for different stages of construction and use. In addition, the vibration measurements were used to validate success and effectiveness of the decoupling and the other structural dynamic measures. Based on the simulations, predictions for the vibration level were made. A monitoring system with acceleration sensors was installed to permanently monitor compliance with the vibration limit. This allows for the detection of both damage to the structure in case of seismic events and of problems with the vibration control

Prediction model for calculation of the limestone powder concrete carbonation depth

The efficient way to mitigate the impact of the concrete industry on climate change is to reduce the clinker content in the concrete mix. Beside incorporating supplementary cementitious materials (SCMs), it is possible to use high filler content combined with concrete mix optimisation. Limestone powder emerges as a promising filler mineral due to its availability and ready-to-use technology. In this work, the carbonation resistance of concrete with a high limestone powder content (45–65% of the powder phase) was experimentally tested. Test results showed that, with an optimized mix design featuring low water content and increased paste and plasticizer volume, concrete mixes satisfied high workability and strength demands for commonly applied strength classes. However, carbonation resistance remains a challenge. After two years in indoor natural conditions, carbonation depths were 8%, 28%, and 67% greater than referent Portland cement concrete for mixes with 47%, 58%, and 65% limestone powder content, respectively. Further analyses showed the inapplicability of the existing fib Model Code 2010 service life prediction model to limestone powder concrete. Based on a comprehensive database of experimental results, the modification of the fib prediction was proposed. A full probabilistic service life analysis revealed that for concrete with more than 20% limestone powder content and for both 50 and 100-years’ design service life, the currently prescribed concrete cover depths in European standards should be increased, depending on the carbonation exposure class

Geometric properties and idealized model of the Monument to the fallen soldiers of the Kosmaj detachment

In the territory of the former Yugoslavia, in the post-war period, numerous monumental sculptures, also referred to as "spomeniks" (monuments), were erected at various points, often in natural settings, to commemorate the People's Liberation War. Our focus in this paper is on one of them, the monument to the Kosmaj Partisan Detachment on mountain Kosmaj, near Belgrade. We examine the historical context in which the monument was created, directing the emphasis of the work towards the geometrical analysis of this object. We delve into the geometric elements of the monument, utilizing photogrammetry and descriptive geometry procedures. Through 'reverse engineering' based on the point cloud model and its orthogonal projections, we provide its idealized dimensions and plan.The 9th International Conference on Engineering Graphics and Design ICEGD 2024, 14-15 May 2024, Cluj Napoca, Romani

Experimental investigation of the construction joint in concrete ground floors

Ground floors of industrial buildings, fully supported on the ground or piles, are usually made of several concrete segments connected through free-movement construction joints. These joints should provide shear load transfer of the slab and minimise its vertical displacements while allowing slab horizontal movement to prevent damage due to concrete dry shrinkage. The construction joint “Dilat 08”, consisting of round steel dowels and steel formwork, was experimentally tested in a laboratory environment to determine its behaviour to shear load. The experimental double-shear setup consisted of three slabs connecting through the “Dilat 08” join system, with two side slabs fully supported on the base and the middle slab on which the vertical loading was applied. Specimens were formed with a gap of 10 mm between adjacent slabs to simulate the construction joint opening. Two construction joint orientations were investigated introducing the vertical load to the slab with a steel plate on the edge and to the slab with an angle profile on the edge. Experimental testing of both specimens resulted in construction joint failure due to concrete cracking around steel dowels, near the edges of the middle slab. The investigation confirmed that the joint orientation affects the joint shear response, demonstrating larger joint resistance when the steel plate is installed in the slab subjected to failure. Although contributing to the joint bending stiffness before formwork installation on the site, the horizontal leg of the angle profile decreases the joint resistance. Experimentally obtained joint resistance was compared to the design values of resistance according to Technical Report 34 and EN 1992- 4, highlighting a considerable difference between the two analytical approaches. The comparison between the “Dilat 08” and three types of free-movement joints available on the construction market showed that “Dilat 08” features larger resistance according to Technical Report 34, but it also weighs more

Numerical Modeling of Two Adjacent Interacting URM Structures

Masonry structures in addition to their long heritage are still widely used in civil engineering practice. It should be emphasized that a lot of research has already been done on the seismic behavior of masonry structures. However, due to the nature of such a problem, its complexity and seriousness, the development of numerical models and their connection with experimental tests are always important. This is particularly significant considering their vulnerability to the action of horizontal forces generated during seismic excitations. In recent decades, many researchers have tried to capture the behavior of unreinforced masonry (URM) structures or reinforced concrete (RC) frames with masonry infills exposed to earthquakes, using different approaches. This paper tackles numerical modeling based on the finite element method (FEM) for the estimation of the dynamic response of two adjacent interacting URM units, subjected to shaking table motions. Geometrical and material properties of the specimen are provided by the Horizon 2020 project SERA-AIMS (The Seismology and Earthquake Engineering Research Infrastructure Alliance for Europe – Seismic Testing of Adjacent Interacting Masonry Structures). The analyses of dynamic performance were executed in SAP2000 software. Obtained results on the numerical model provide useful guidelines for modeling the nonlinear seismic behavior of masonry buildings

Mogućnosti optimizacije dilatacione spojnice industrijskih podova u cilju povećanja efikasnosti

Construction joints for industrial floor buildings are designed to relieve longitudinal stresses due to volumetric changes in large concrete surfaces. Various geometries of construction joints have been designed to obtain main constructional requirements, i.e. horizontal movements of the concrete slab panels due to expansion and contraction and transfer of vertical loads between adjoining slabs. This paper presents an experimental and numerical investigation of the free movement construction joint with embedded formwork and steel dowel bars as an integral solution. Analysis has the main focus on the two main aspects of the construction joint behaviour, i.e. resistance and stiffness, through obtained failure modes and joint geometry, towards higher joint efficiency.Dilatacione spojnice u podnim pločama industrijskih zgrada su konstruisane da obezbede oslobađanje podužnih napona koji se javljaju kao posledica promena u zapremini velikih površina betonskih ploča. Dilatacione spojnice različitih geometrija se konstruišu u svrhu postizanja osnovnih konstrukcijskih zahteva: obezbeđivanje horizontalnih pomeranja usled skupljanja i tečenja betona, kao i prenošenje vertikalnog opterećenja između susednih segmenata betonskih ploča. U ovom radu predstavljeno je eksperimentalno i numeričko ispitivanje dilatacione spojnice sa ugrađenom čeličnom oplatom i čeličnim moždanicima kao integralnim rešenjem. Analizom su obuhvaćene dve osnovne karakteristike ponašanja dilatacione spojnice: nosivost i krutost, kroz ostvarene oblike loma i uticaj geometrije dilatacione spojnice u svrhu postizanja veće efikasnosti

Modeli loma čeličnih grednih nosača sa otvorima u rebru

As an alternative to trusses and open-web joist systems, beams with web openings are lightweight, long-spanning structural elements that bind structural role (efficient load distribution) and functionality in a visually acceptable way by allowing service routes to be installed within their cross-section height. Due to the presence of web openings, load transfer is accompanied by complex stress distributions in the section web, causing failure modes that are distinguishable from those of solid I-section beams. This paper summarizes the different failure modes of the beams with web openings that have been discovered and confirmed in numerous experiments of reference scientific researches. Based on the state-of-the art in this structural area, the predictions of different failure modes that are affected by influencing geometric parameters are provided.Prisustvo otvora u rebrima nosača prouzrokuje složenu raspodelu napona i posledično modele loma koji se značajno razlikuju od onih kod tradicionalnih čeličnih grednih elemenata. Shodno tome, mnoge studije su se bavile ovim problemom kroz eksperimentalna ispitivanja i numeričku analizu. Ovaj rad rezimira sprovedena istraživanja o različitim modelima loma ovih nosača. Na osnovu dostupne literature, formirana je baza sa više od stotinu eksperimentalnih i numeričkih primera, što je dalje omogućilo bolje sagledavanje zaključaka pojedinih autora. Na osnovu pomenute baze, data su predviđanja očekivanih modela loma na osnovu različitih odnosa geometrijskih parametara