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Peak pressures on high-rise buildings roof: A dual approach through validated LES and wind tunnel experiments with uncertainty quantification
No full textUnderstanding the accuracy of predicted peak pressure in wind engineering is crucial for effective risk assessment and structural design. This study investigates the capacity of large eddy simulation (LES) in predicting peak pressure coefficients on the flat roof and facade of a high-rise building, incorporating uncertainty quantification from 11-hour equivalent full-scale experimental measurements. The isolated and group configurations under 0° and 45° wind angles are analysed.
The performance of two estimation methods for peak pressure coefficients—the traditional "epochal" approach and peaks over threshold (POT)—is evaluated, determining the optimal set of parameters that minimises uncertainty. While the stationarity test reaches satisfactory residuals for a 75-minute equivalent full-scale duration, 25- and 37.5-minute durations are also analysed. The traditional approach is preferred for its reliability and consistency, although POT notably excels in capturing higher peak pressure coefficients.
Numerical results demonstrate negligible differences across all analysed durations and align well with experimental findings. A 25-minute equivalent full-scale duration is found to be a suitable representative of the entire signal. However, notable discrepancies near the upwind corners on the roof, with larger uncertainty in experimental data, underscore challenges in prediction accuracy for these regions. It emphasises importance of individual treatment and validation for each case
Energy based damage model for low-cycle fatigue of ductile materials
No full textA uniaxial material model for fatigue damage accumulation, established on the connection of unit elements, is presented in this paper. Although these units are regarded as micro-elements in the proposed model, they are based on a hysteretic operator that enables calculating hysteretic energy loss as an analytical expression. Further, this unit element represents a mechanical model with elastoplastic damage behavior in function of strain. The second level of modeling is defined by the connection of these units (micro-elements) with different values of total energy dissipated at failure. By changing the distribution of dissipated energy limit, various fatigue damage evolution laws are developed. Calculation of total and hysteretic energy loss in one loading cycle is also affected by fatigue damage as the varying number of unit elements are been eliminated when their maximum dissipation energy is reached. Material parameters for the model were defined based on the experimental monotonic and cyclic stress-strain tests, still, detailed comparison was not performed as the main advantage and aim of the paper was the development of the method for assessment of damage evolution in fatigue analysis. On the other hand, the number of cycles to failure (Nf) and total heat dissipation are compared in both qualitative and quantitative aspects with experimental results. Finally, based on the proposed model, mean strain and load sequence effect diagrams were constructed. It is shown that the proposed model can provide a reliable estimation of fatigue life in the low-cycle regime of loading. The maximum error for the calculated Nf was 3% for constant strain loading for experiments with strain amplitude less than 5%. In load sequence fatigue life estimation, the proposed model demonstrated good accuracy, with a maximum error of 34%. Further, obtained results were achieved with different types of damage evolution that could be defined for the same material and fatigue life
Simulating instabilities of rare rock landforms in the Devils Town, Serbia
No full textThe Devils Town site in Serbia hosts weathered volcaniclastic deposit, shaped by erosion into numerous closely spaced pillars, up to 15 m high and 5 m across, commonly capped by a large andesite boulder. The site has currently been subjected to monitoring projects,
using non-invasive techniques, such as terrestrial LiDAR and SfM, providing several sequences of point clouds for change analyses. Herein, a preliminary sequence 2017-2018 is used to reconstruct instabilities of a distinct pillar. Analysis was targeted at locating minor
rockfall source areas. Detachments were identified and simulated using 2D and 3D geotechnical tools. Rock fragment and ground simulation properties were assumed from field observations and index properties determined using portable tools. Reconstructed trajectories show good correlation with post-event (201 8) point cloud. Further systematic monitoring could help understand the erosion and weathering processes better and undertake strategies towards the site's sustainability and resilience to climate change
Claims and dispute resolutions on construction projects
No full textConstruction industry is a very specific industry as it executes its unique projects in specific and
for every project different conditions. The problems between the contract parties that occur on a
construction project are mainly connected with not fulfilling or erroneous fulfilment of the
obligations of the contract parties or due to unforeseen situations and circumstances. Occurrence
of any of the numerous risk events surrounding each construction project can have a significant
impact on a project, especially money and time wise. Parties submit claims to the other party
when they think that they have a right to additional payment or extension of time. The procedure
for approving or disapproving a claim should be reasonably short in order to avoid further
complications and misunderstandings. FIDIC Red Book envisages a time frame of 42 days for
the Engineer to approve or disapprove a submitted claim with full supporting particulars.
If there is no agreement between the parties concerning a claim, it becomes a dispute. At present,
most of the disputes in the construction industry are resolved through court proceedings, which
are expensive and take a long time. Due to these reasons, other dispute resolution methods have
been introduced into the construction practice. These are: Mediation, Neutral Evaluations,
Decision by an Independent Expert, Adjudication, Arbitration.
Mediation and Neutral Evaluations are methods in which the parties receive help to find a
mutually acceptable solution to a dispute, but there is no imposing of a solution by a third party.
Adjudication was promoted as a fast-track method for resolving disputes on construction projects
since mid 90’s. This method is somewhat similar to arbitration, but much less formal and with a
short time period for the adjudicator to bring a decision. The decision made by the adjudicator is
binding on the parties and immediately enforceable. FIDIC, in its 1999 edition of construction
contracts, has introduced the role of Dispute Adjudication Board (DAB).
Arbitration is an alternative to litigation, but it must be agreed between the parties. For
international construction contracts, international arbitration is the dominant method of dispute
resolution. The International Court of Arbitration of the (ICC) in Paris is referred to as the
institution for final settlement of disputes between the parties on FIDIC based contracts
Parametarsko modelovanje srednjevekovnih portala Raških crkava
Get PDFU ovom radu zasnovanom na geometrijskim
pravilnostima arhitektonskog dizajna, istražuju se mogućnosti
načina kreiranja digitalnih parametarskih modela portala crkava
u Raškoj (srednjevekovna teritorija Srbije). U literaturi, ovi
portali su prepoznati kao romanički, prema karakterističnom
dizajnu i geometriji. Rad je nastavak istraživanja autora na
analizama šest izabranih portala, u kontekstu njihovog
arhitektonskog dizajna i geometrije. Na osnovu definisanih
dimenzionih parametara i geometrije oblika elemenata jednog
portala, kreirani su odgovarajući 3D modeli elemenata, kroz
nekoliko faza, obradom u različitim programskim paketima. Kroz
modelovanje izabranog portala pokazan je postupak koji
kombinuje tri programska paketa: AutoCAD, SolidWorks i
ArchiCAD. Cilj rada je doprinos u sferi kreiranja digitalnih
biblioteka elemenata izabranog tipa portala, u okviru Heritage
Building Information Modelling-a (HBIM-informaciono
modelovanje istorijskih objekata)
Optimization of purlins cross-section exposed to fire
Get PDFIn 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
Implementation of deep neural networks (DNN) for pavement crack detection
Get PDFThe lifespan of a structure encompasses its initial construction, followed by its
operational phase, and ultimately, its rehabilitation. To accurately determine the optimal timing for
rehabilitation, it is essential to continuously monitor the current state of the structure. Applied to
road infrastructure, this monitoring process entails the systematic collection of data on pavement
damage. This paper provides an analysis of existing models for detecting pavement cracks and
introduces a detection method leveraging artificial intelligence techniques, specifically deep neural
networks, and transfer learning. During the selection process, various deep neural network
architectures, including ResNET 50 and ResNET 34, were evaluated. Comparative analysis
revealed that the ResNET 50 network achieved the highest accuracy (Acc) in crack detection
2022 Düzce, Türkiye earthquake: advances in the past 2 decades, lessons learned, and future projections
No full textIn the year 1999, two devastating earthquakes ( Mw 7.4 Kocaeli earthquake in August and Mw 7.2 Duzce earthquake in November) occurred in Northwest Turkiye. These two earthquakes led to a very large number of casualties and building collapses. When the 1999 earthquakes occurred, most of the structures in the earthquake-impacted region were not designed according to modern seismic design codes. During the 25 years following those earthquakes, there have been significant advances in building construction in the light of earthquake engineering, including adequate seismic codes, new regulations, and effective code enforcement in the earthquake impacted region. These advances have been reflected in the construction of new structures in the region and the retrofitting of existing ones. As a result, 70–80% of the current building stock in Duzce was designed, constructed, or retrofitted after the 1999 earthquakes. Almost 23 years later, in 2022, an Mw 6.1 earthquake occurred in Duzce, with ground shaking close to the seismic design code life safety performance level. The 2022 earthquake provided a great opportunity to evaluate the effectiveness and consequences of the advances in earthquake engineering and the relevant policy-making and regulations. This paper provides a comparative overview of the 1999 and 2022 earthquakes that struck the city of Duzce in terms of hazard, vulnerability, and consequences. Furthermore, other key lessons learned from the 2022 Duzce earthquake are documented based on field reconnaissance and numerical simulations. The lessons learned are expected to provide useful guidance for the reconstruction efforts after the 2023 Kahramanmaraş Turkiye earthquake sequence or in similar efforts in other parts of the world
Dinamičke toplotne karakteristike homogenih građevinskih pregrada
Get PDFU radu je analizirana jedna gradjevinska pregrada
poznatih toplotnih i fizičkih karakteristika, i odredjen je toplotni
impulsni odziv pregrade u analitičkom obliku na zadate granične
uslove na spoljašnjoj i unutrašnjoj površini. Odziv je odredjen
rešavanjem Fourier-ove jednačine za zadati problem u
frekventnom i vremenskom domenu. Na osnovu ovih rešenja
diskutovane su dinamičke toplotne karakteristike gradjevinskih
pregrada
Optimization of adjustment factors for EUROCODE traffic load model for road bridges
No full textThe main traffic design load for road bridges used throughout the Europe is the Load Model
1 (LM1) as defined in the EN1991-2 (European standard for traffic loads on bridges). It consists of
tandem system (TS), i.e. a pair of concentrated forces representing a heavy vehicle, and uniformly
distributed load (UDL), positioned across the bridge in several design lanes. This load model is
multiplied by the adjustment factors – the α coefficients – adjusted for each country as the Nationally
Determined Parameters. There are different α coefficient for TS and for UDL, and for different lanes
(αQ1 for TS in first heaviest lane, αQ2 for TS in second heaviest lane, αq1 for UDL in first heaviest lane,
and so on). These coefficients should be determined for each country who adopted the Eurocode,
based on the local traffic volume and composition. Calculation of the ratio of αQ1 / αQ2 / αq (where αq
is the adjustment coefficient for UDL for all lanes) has been performed as an optimization problem,
first using the conventional safety partial factor calibration approach, and then verified with genetic
algorithm procedure. Optimization was based on 127 yearly extreme values of actual traffic
scenarios, detected by the extreme values of blended (averaged) α coefficient (one value of α
coefficient for all lanes, and for both TS and UDL) obtained by structural analysis of a set of
representative bridges (or more precisely structural systems), loaded by actual recorded traffic data
from long-term weigh-in-motion (WIM) measurements. Optimum ratio of these three adjustment
factors for bridge traffic load will allow the extrapolation of all three values to the required return
period in the further research study. By this, optimum traffic load model for existing bridges can be
obtained, which would have significant economic impact for bridge owners (“JP Putevi Srbije” in
Serbia), since the lower α coefficients on the sound scientific basis would safely keep many bridges
in service, without the need for their upgrading or replacement