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Behaviour of demountable steel-concrete composite beams with bolts and headed studs
No full textImplementation of demountable beams in steel-concrete composite floors enables
structure reuse during several life cycles, consequently leading to savings in material
consumption and reduction of emissions, providing overall ecological benefits.
The behaviour of the innovative demountable beam with a shear connection consisting
of headed studs and bolts is analysed in this paper. The proposed beam is
formed of a steel profile and a steel-concrete composite slab cast in open trough
profiled steel sheeting. Headed studs, welded to the additional steel angles, are
placed in sheeting ribs, whereas bolts are installed between ribs, connecting the
steel angles and profile flange. A numerical FE model of a full-scale steel-concrete
composite beam has been developed to analyse the beam behaviour under service
loads. Experimental results of push-out tests have been used to describe the loadslip
behaviour of headed studs, whereas bolt response has been simulated according
to the experimental investigations of lap joints with preloaded bolts and oversize
holes. The parametric study has been conducted by varying the bolt diameter, grade
and bolt hole size. The results have validated the applicability of the proposed system,
confirming the fulfilment of serviceability limit state requirements
Contribution of strain-hardening cementitious composites (SHCC) to shear resistance in hybrid reinforced concrete beams
Get PDFStrain Hardening Cementitious Composite (SHCC) is an innovative type of fibrereinforced
cement-based composite that has superior tensile properties. Because
of this, it holds the potential to enhance the shear capacity of reinforced concrete
(RC) beams, if applied properly. This paper presents the general and distinctive
properties of SHCC as well as a literature review of topics related to the contribution
of SHCC layers to the shear resistance of RC beams with and without shear
reinforcement. Based on the analysed results, it is concluded that the main
characteristics of SHCC are its microcracking behaviour, high ductility, and
increased tensile strength (between 2 and 8 MPa) at large deformations. When used
in structural elements, SHCC develops multiple parallel cracks compared to
concentrated cracks in conventionally reinforced concrete. The biggest
disadvantage of SHCC is its significant drying shrinkage. Although showing high
variability, using SHCC as laminates with a thickness of 10 mm improves the shear
capacity of hybrid RC beams, but debonding of interfaces in a hybrid system occurrs
in some cases
Experimental determination of dynamic parameters of heat passage through the facade wall of a weekend cottage on mountain Kopaonik, Serbia
Get PDFIn this paper, using a dynamic RC model for heat transfer in a room on the ground floor,
the three-time constants of heat transfer that corresponds to the different parts of a
weekend cottage on Kopaonik were determined. The model considered the heat
accumulation and losses through the facade wall, floor and interior part of the room. The
time constant of the wall is the characteristic time for establishing a stationary state of the
temperature inside the wall during rapid changes in the external air temperature and it
represents a measure of the thermal inertia of the wall. The model was validated by
experimental measurements of air temperatures and wall surface temperatures.
Measurements were carried out in situ continuously for 21 hours in real conditions in the
winter period. Air temperature measurements were made with standalone data loggers.
The paper presents the results of the measurements, the parameters and the electrical
diagram of the RC model and the results comparing the measured temperatures with the
same temperatures obtained by this model. Satisfactory agreements were obtained
Effect of Inter-panel Connections on Modal Properties of Cross-Laminated Timber Floors
Get PDFCross-laminated timber (CLT) floors are typically composed of prefabricated CLT panels assembled on a construction site. The actual connections are commonly disregarded at design stage. CLT floors are modelled either as a monolithic slab or more frequently as a collection of CLT panels with no connections. This paper presents a numerical study designed to demonstrate the effect of two common inter-panel connections, i.e. single surface spline and half-lapped joint, on vibration modes of various CLT floor configurations. The inter-panel connections are modelled as an equivalent 2D elastic strip between the CLT panels. This uncomplicated yet robust approximation of reality can be used readily in design practice, regardless finite element (FE) software used to determine modal properties of a floor. The corresponding monolithic floors and those without inter-panel connections are studied for comparison. The results showed that the common practice of modelling CLT floors either as monolithic slabs or as a set of independent panels should come to an end
Behaviour and design of bolted connectors with mechanical coupler: an overview
Get PDFThe construction industry is one of the most important parts of economic development of society but it
also has a very negative impact on the environment. Using the three concepts of circular economy: reuse,
reduce and recycle, it is possible to decrease its negative impact. The steel-concrete composite structures
and prefabricated structures enable, environmentally beneficial, circular life-cycle of buildings. For
structural performance during the lifecycle, it is very important to have an adequate connection between
the steel and reinforced concrete members.
Different types of connectors have been widely used in composite structures. Demountable ones are
advantageous in terms of reuse. In the last few years, the innovative demountable steel-concrete bolted
connector with mechanical coupler has been proposed. There are two types of these bolted connectors
depending on the type anchorage i.e., with the rebar anchor or with the second bolt.
This paper gives an overview of previous research of bolted connectors with mechanical coupler
capacity under static load. Influence of key parameters on the shear behaviour of the connector was
observed: concrete compressive strength, connector dimensions and concrete edge distance. The shear
and tension resistances of individual parts of the commercially available connectors were determined
using recommendations of design codes and technical documentation. In case of the connector loaded
in tension, it was concluded that the resistance is governed by the resistance of the rebar anchor. In case
of the connector loaded in shear, design recommendations were also compared with the previous
experimental tests. It was concluded that the shear resistance highly depends on the connection layout
and concrete strength
Wastewater flow measurements in sewer networks: Combining innovative and conventional measurement methods
Get PDFJedan od preduslova za efikasno upravljanje i strateško planiranje razvoja kanalizacionih sistema je dobro poznavanje dinamike rada mreže. Ključnu ulogu imaju mereni podaci, prvenstveno o promenama protoka i nivoa, kako u sušnom tako i u kišnom period. Nažalost, kanalizacione mreže su u većini slučajeva slabo pokrivene adekvatnim mernim mestima. Tako prilikom planiranja kapitalnih investicija, npr. postrojenja za prečišćavanje otpadnih voda, nedostajući podaci se obezbeđuju kroz merne kampanje. Ključni izazovi pri sprovođenju mernih kampanja su povezani sa lokacijski i hidraulički nepovoljnim mernim lokacijama, koje negativno utiču na kvalitet izmerenih podataka. U ovom radu je prikazan primer kombinovanja inovativnih sa konvencionalnim metodama za merenja protoka u kanalizacionim sistemima sa ciljem dobijanja reprezentativnih podataka u složenim mernim uslovima.One of the prerequisites for efficient management and development planning of the sewer systems is the adequate knowledge of network dynamics. Measured data play a key role, mainly the flow rate and level variations in dry and wet periods. Unfortunately, sewer networks are commonly scarcely covered with measurement systems. Thus, when capital investments are planned, e.g. wastewater treatment plants (WWTP), missing data is acquired through measurement campaigns. Challenges in the execution of the measurement campaigns are mostly correlated to hydraulically and organizationally unfavorable measurement locations, reflecting negatively on the quality of the measured data. In this paper, an example of the combination of the innovative and conventional flow measurement methods in sewer networks is shown, to allow for the acquisition of the representative data in complex measurement conditions
Stability Calculation of the Plane Steel Frame Structures Using Tangent Modulus Theory
No full textThis paper considers the phenomenon of the instability of steel plane frame structures in the elastic-plastic domain. The numerical analysis uses FEM, where the corresponding stiffness matrices are based upon the trigonometric and hyperbolic interpolation functions of normal forces. The tangent modulus concept is applied when buckling occurs in the plastic range. Thus, the stiffness matrices for nonlinear material behavior are also derived. The procedure for determining effective length factors of compressed columns, which implies a global stability analysis of entire frames, is established too. It means that the proposed approach is based on the assumption that the collapse of the structure occurs when the most loaded columns reach their stability limit. So, the presented procedure enables the calculation of the real critical load of plane frame structures in the elastic-plastic domain and determines the corresponding effective length factors
Experimental results of reinforced concrete frames with masonry infills with and without openings under combined quasi‑static in‑plane and out‑of‑plane seismic loading
Get PDFReinforced concrete (RC) frames with masonry infills can be encountered all over the world, especially in earthquake prone regions. Although masonry infills are usually not considered in the design process, in the case of seismic loading they are subjected to inplane and out-of-plane forces that can act separately or simultaneously. In recent earthquakes it was observed that seismic loads can severely damage masonry infills or even cause their complete collapse, especially when the loads act simultaneously. Due to this, effects of interaction of in-plane and out-of-plane loads on seismic performance of masonry infills have received more attention recently. However, most of studies focus only on fully infilled frames, even though openings, such as windows and doors are essential parts of infills that substantially affect the seismic response of masonry infills. Therefore, this article presents the results of a comprehensive experimental study on nine full-scale traditional masonry RC frames infilled with modern hollow clay bricks for configurations with and without window and door openings under separate, sequential and combined inplane and out-of-plane loading. Based on the results, a detailed comparison and interpretation for the different infill and loading configurations is presented. The test results clearly show the unfavourable influence of openings and combined loading conditions as well as the importance of the quality of execution of the circumferential mortar joint between infill and frame. The new findings can be used as a basis for the required development of innovative solutions to improve significantly the seismic performance of RC frames with masonry infills
Uni- and multivariate bias adjustment of climate model simulations in Nordic catchments: Effects on hydrological signatures relevant for water resources management in a changing climate
Get PDFHydrological climate-change-impact studies depend on climatic variables simulated by climate models. Due to parametrization and numerous simplifications, however, climate-model outputs come with systematic biases compared to the observations. In the past decade, several methods of different complexity and dimensionality for adjustment of such biases were introduced, but their benefits for impact studies and accurate streamflow projections are still debated. In this paper, we evaluated the ability of two state-of-the-art, advanced multivariate bias-adjustment methods to accurately reproduce 16 hydrological signatures, and compared their performance against two parsimonious univariate bias-adjustment methods based on a multi-criteria performance evaluation. The results indicated that all bias-adjustment methods considerably reduced biases and increased the consistency of simulated hydrological signatures. The added value of multivariate methods in maintaining dependence structures between precipitation and temperature was not systematically reflected in the resulting hydrological signatures, as they were generally outperformed by univariate methods. The benefits of multivariate methods only emerged for low-flow signatures in snowmelt-driven catchments. Based on these findings, we identified the most suitable bias-adjustment methods for water-resources management in Nordic regions under a changing climate, and provided practical guidelines for the selection of bias-adjustment methods given specific research targets and hydroclimatic regimes
Коришћење UAV фотограметрије и ласерског скенирања из ваздуха (LiDAR) приликом праћења активности клизишта на Умци
Get PDFКлизишта, као природне непогоде, егзистирају годинама, па у неком случајевима и више деценија. Због штетних последица које проузрокују, а како би се потенцијална опасност благовремено уочила и на време спречила, потребно је спроводити континуирани мониторинг активности клизишта. Овај рад приказује праћење активности клизишта Дубоко на Умци у периоду од годину дана (2018 – 2019). Коришћене су 2 техникеприкупљања података – UAV фотограметрија и LiDAR ласерско скенирање из ваздуха. UAV системи беспилотних летелица омогућавају лаку примену при снимању мањих подручја уз приступачнију цену од конвенционалних фотограметријских система. Веома су корисни у неприступачним пределима, на пример приликом пожара, поплава или других природних непогода. Са друге стране, LiDAR систем се показао као јако користан код снимања терена обраслог густом вегетацијом. Како би се показало коришћење обе технологије, а и примена различитих програма за обраду података, клизиште је подељено на 2 дела – горњи и доњи део клизишта. Подаци за 2019. годину, за оба дела клизишта, су прикупљени уз помоћ UAV фотограметрије, као и за 2018. годину горњег дела клизишта, док су подаци о доњем делу клизишта за 2018. прикупљени LiDAR-ом. Активност клизишта је посматрана на 2 начина: кроз праћење висинског померања терена и детекцију померања објеката (хоризонтално померање). Детекција померања терена извршена је на основу генерисаних дигиталних модела терена, док је хоризонталнно померање посматрано кроз генерисане ортофотое. У завршном делу рада на основу теоријских поставки и експерименталне реализације изведени су закључци у погледу примењивости UAV система као алтернативне фотограметријске платформе за снимање и ласерског скенирања из ваздуха у циљу праћења кретања клизишта