GENERATIVE DESIGN OF STRUCTURAL STEEL JOINTS

Structural project is based on technical regulations, structural codes, construction conditions, and client requirements. Through the structural design process, some important decisions that can significantly affect the final result must be implemented. The most important factor for optimal design is the reduction in material and overall work costs. Selecting appropriate joint configurations that can reduce the overall weight and work on the structure is critical. To examine a significant number of possible configurations and their effect on structural behavior, the generative design method (GDM) is used. In this study, software is custom developed, and a relevant example of generative joint structural design is provided. The methodology for the optimal joint and structure design is described comprehensively. The final results show that the GDM is an effective methodology for application in the design of steel structures.

ACHIEVING SUSTAINABLE URBANIZATION OF THE NATIONAL THEATRE IN LONDON THROUGH CHANGE OF USE AND FUNCTIONS OF ARCHITECTURE

The human population is currently on the rise and most Europeans live in urban areas, leading to increased urbanization. The change comes with its challenges, as cities, architecture, and urban spaces need to become more fluid, multi-functional, and innovative. This paper examines whether a change of use of public spaces, and functions of architectural and urban forms, can be used as an element in the implementation of sustainable urbanization. The theoretical framework of this paper focuses on literature findings relating to identified key aspects such as innovative approaches in changes of use — recycling and upcycling, green infrastructure and financial aspects, concepts of “right of the place”, and public participation. These aspects are addressed on both theoretical and practical levels, with the National Theatre in London as a case study. Findings convey that the change of use of spaces can be utilized to achieve sustainable urbanization, together with the management of functions and uses of architectural and urban forms. However, further research is needed with various stakeholders to identify a solid and inherent database, as a foundation on which the most optimal urban spaces would emerge, by identifying new functions and uses of urban space and architecture.

NUMERICAL MODELLING OF THE MORPHODYNAMICS OF THE PLOČE GRAVEL BEACH IN RIJEKA

The morphodynamics of an artificial gravel beach in the Bay of Rijeka (Ploče Beach) was analyzed. The morphological changes of the beach face were monitored through an intense situation of gravitational surface wind waves from the incident SSW direction. A numerical modeling technique was applied, after initially establishing a numerical model for wave deformation. A model for sediment transport was established based on its results. Both models were based on the finite volume method. In addition, the partial contribution of the longshore component of sediment transport was analyzed based on empirical formulae. The modeling results were verified by comparing the positions and amounts of eroded/accumulated material along the beach with the processing of terrain images in the form of point clouds. The erosion and accumulation positions of the beach sediment material, obtained by numerical model simulations, corresponded to the surveyed positions. The total volume of eroded and accumulated material based on terrain image processing corresponded to the model values.

EXPLORING THE EFFECT OF ORGANIC ADDITIVES ON PHYSICAL PROPERTIES OF BITUMEN

Warm additives had wide popularity in recent years due to saving in energy and lowering emissions dealt with asphalt mixture production. Warm Mix Asphalt (WMA) is produced by using foaming technology or reducing -viscosity additives of binder to enhance the rheological properties. In this study, organic-based additives (Asphaltan A and Asphaltan B) are used to investigate their effect to minimize the viscosity and lower the temperature of asphalt mixture production. Bitumen is mixed with three doses of each additive: 1, 2, and 3% of its weight. The binder viscosity was measured by rotational viscometer with and without the additives at three different temperatures. The study showed that the organic additives have a positive impact on the behavior of the binder in terms of viscosity reduction and made enhancements in terms of bitumen properties. This result could be useful in the reduction of production temperature and quantity of odour emissions.

CALCULATION OF CLIMATE LOADS DESIGN VALUES ACCORDING TO THE PROBABILITY MODEL OF ANNUAL MAXIMUM SERIES

The aim of this work is to improve a method for determining the characteristic values of climatic loads according to a probabilistic model of the annual maxima sequence, by choosing a rational type of generalized extreme value distribution law. An analysis is provided regarding the suitability of using four types of distributions for describing a data collection of maximum values of climatic loads. Using example data from the meteorological stations of Ukraine, it is found that for coefficients of variation smaller than 0.85–1.0, it is advisable to use the double exponential Gumbel distribution (generalized extreme value distribution type-I), and at higher values of the coefficient of variation, it is advisable to use the Weibull distribution (generalized extreme value distribution type-III). Recommendations are provided for considering the accuracy in the estimations of the characteristic values of loads according to the probabilistic model for the annual maximum value series.

FIBER-REINFORCED CONCRETE FOR RIGID ROAD PAVEMENTS MODIFIED WITH POLYCARBOXYLATE ADMIXTURE AND METAKAOLIN

Increasing the strength and durability of road surfaces is crucial. Therefore, the concrete compressive strength, flexural strength, frost, and abrasion resistance of fiber-reinforced concrete for rigid pavements are investigated in this study an experiment is performed based on an optimal plan, in which four factors of concrete composition are varied: the amounts of Portland cement, polypropylene fiber, metakaolin, and polycarboxylate type admixture. Experimental statistical models for investigating the effects of composition factors on concrete properties are established. It is discovered that owing to the use of metakaolin and a superplasticizer, the concrete compressive strength increases. Furthermore, the use of modifiers and fiber reinforcement increases the flexural strength, frost resistance, and wear resistance of concrete. X-ray phase analysis of the fiber-reinforced concrete structure confirm the effectiveness of the modifier effect, in particular the positive role of metakaolin as an active pozzolana. The developed fiber-reinforced concrete for rigid pavements with rational modifiers, depending on the Portland cement content, exhibits compressive strengths from 55 to 70 MPa, flexural strengths from 8 to 9.5 MPa, frost resistances from F350 to F450, and abrasion resistances from 0.3 to 0.4 g/cm2. Such properties ensure the high durability of fiber-reinforced concrete and allow it to be used on road pavements that support heavy loads and traffic.

WETTING AND DRYING RESISTANCE OF LIME-STABILIZED EXPANSIVE SOILS MODIFIED WITH NANO-ALUMINA

Weak soil at construction sites necessitates ground improvement. Chemical stabilization is typically carried out using either lime or cement. The primary objective of this study was to assess the strength and durability of lime-stabilized soils modified with nano-alumina (NA). This study adopted the scientifically established initial consumption of lime (ICL) content for soil stabilization. In addition, nano-alumina was added in varying percentages as an auxiliary additive. It was observed that 0.5 % of nano-alumina was optimal with respect to the ICL for maximizing the soil stabilization. The stabilized soils were cured for 0, 7, 14, and 28 days. Post-curing testing revealed that the strength increased sixfold for the optimal combination, compared with the virgin soil. To understand the durability behavior of the optimal combination, the stabilized soil specimens were subjected to wetting and drying cycles after 28 days of curing. The optimal combination was nearly as durable as that of the lime-stabilized soil subjected to five cycles of wetting and drying.

APPLICATION OF PRINCIPAL COMPONENT ANALYSIS TO DROUGHT INDICATORS OF THREE REPRESENTATIVE CROATIAN REGIONS

Drought has become a very frequent hydrological event globally, including in Croatia. It can generally be explained by air temperature and precipitation changes on an annual and seasonal basis, owing to climate change. To contribute to the knowledge on drought phenomena in Croatia, the changes in air temperature and precipitation over a relatively long period between 1951 and 2018 were analyzed. The meteorological stations included in the research were Osijek, Zagreb, and Split, which represented the climate of the entire country. Drought was estimated using the standardized precipitation evapotranspiration index, which is one of the most comprehensive drought indices. Furthermore, the drought severity and duration were calculated using run theory. These parameters were tested for homogeneity using the standard normal homogeneity test. Only the air temperature exhibited inhomogeneity, with a break year in 1991 (Zagreb and Split) and 1998 (Osijek). The existence of significant temporal trends was tested using the non-parametric Mann–Kendall trend test. The probability of drought occurrence with a certain duration and severity was calculated using the copula function. Finally, principal component analysis was applied to the computed standardized Mann–Kendall test statistic (ZMK ) to define the relevance of each parameter change and their combination in drought occurrence on a seasonal basis. Drought occurrence was less recognizable from 1951 to 1991 (1998). In the second sub-period, the impact of an increasing air temperature was the most significant variable, particularly in Zagreb.

PEDESTRIAN BRIDGES AS ELEMENTS OF THE NEW URBAN IDENTITY OF CITIES

By the start of the 21st century, the majority of the world’s population was living in cities. Therefore, a top priority has been solving the problem of connecting parts of the city divided by traffic infrastructure in the shortest possible manner by using pedestrian paths. The aim of this study was to analyze, systematize, and typologically define the specific types of structures that make this possible, specifically pedestrian bridges located above roads and railway corridors. The primary and secondary requirements that must be met when designing a pedestrian bridge were identified, and an analysis and comparison of examples of constructed pedestrian bridges in Croatia and the world are herein presented. The results of this study enable the conclusion that, in recent times, in the age of the spectacle society and spectacle architecture, pedestrian bridges are simultaneously deemed architecture, engineering, and infrastructure projects. They are becoming new elements in a city’s image and contribute to the creation of a new urban identity. The original design of pedestrian bridges fosters the use of different construction systems and materials in accordance with technical and technological advancements in construction.

ANALYTICAL CALCULATIONS OF THE VIBRATIONS OF VERTICAL STRUCTURES CONSIDERING THEIR DEAD WEIGHT

This paper presents the results of studies on the analytical dependence between the value of a longitudinal distributed load and the frequency of free vibrations in a uniform rod. Based on the exact solution of the corresponding differential equation, a method for calculating vibrations in rod structures, while considering their dead weight, is implemented. The method algorithm is shown using the example of a rod with both ends clamped. This article contains graphs and analytical formulas for displaying dependencies. A table is provided that contains all the necessary coefficients to perform similar calculations for other boundary conditions. These results allow the physical and mechanical characteristics of a system to be used to determine the natural frequency of rod structures without using approximate methods.