Advances in Civil and Architectural Engineering

Risk factors in international rail-system projects

2024-04-08T12:35:36+02:00

Construction projects carry many risks due to their long-term, changeable, and dynamic structures. When these risks are transferred to the international environment, they may give rise to new risks and increase the effects of existing risks. International railway-system projects, involve many project-specific risks due to their long duration and high volume of technological manufacturing. Opening completed rail lines for use requires the anticipation of risks that may arise during the warranty period. This study conducted a survey with construction-sector employees working on rail-system projects in Turkey, Italy, and India regarding the risks they face within the scope of the project. Based on the exploratory factor analysis, the risks encountered in international rail-system projects were grouped under three factors: "management-related risks,” "time- and cost-related risks,” and "product quality-related risks.” The results showed that time and cost risks differed by country.

Improvement of Physical and Mechanical properties of High-performance Sand Concrete with different Silica Fume content

2024-03-11T10:15:43+01:00

Silica fume (SF) is widely used for the improvement of several properties of cementitious materials. For this purpose, this study investigated the effect of SF content on the mechanical and durability properties of high-performance sand concrete (HPSC). The experiment work consists of the preparation of HPSC by adding different amounts of SF (0 %, 4 %, 6 %, and 8 %) as a replacement for ordinary Portland cement at a constant water-to-cement ratio of 0,35. The compressive and flexural strengths were performed on the HPSC samples with two standardised sizes of 40 mm × 40 mm × 40 mm and 40 × 40 × 160 mm, which cured during 3, 7, and 28 d. In contrast, both water absorption and water capillary absorption analyses were conducted under a prismatic size of 40 × 40 × 160 mm and cured for 28 d. Based on the test results, the optimal amount of SF was obtained using mechanical strength analysis (6 %). The results showed that at this content of SF, the compressive strength and flexural strength increased by 6,19 and 10,03 %, respectively. In contrast, the addition of SF above this concentration slightly increased the mechanical properties. However, the lowest value of water absorption was obtained for the sample with 6 % SF content. Indeed, at this concentration of SF, the water absorption and the capillarity values of HPSC samples decreased by 8,80 and 8,57 %, respectively.

Fibre-reinforced concrete as an aspect of green construction technology

2024-06-18T08:29:32+02:00

This study investigates the effects of the different types and percentages of fibre reinforcements in concrete on structures' design life to advance the phase of the products' use. Clearly, relatively wide cracks in the concrete during the structure's exploitation, using fibre reinforcement, will be transformed into a pattern of fine microcracks. Restricting the width of cracks using fibres in concrete advances the structure's design life, increasing its durability. Moreover, the investigation of the correlation between compressive and tensile strength indicates a significant increase in the tensile strength of fibre-reinforced concrete. The safety factor against failure of fibre-reinforced beams on the shear strength for mixtures with different amounts of fibres increased approximately two times with the growth of content steel fibre from 0,25 to 1,50 %. Concrete with recycled coarse aggregates and fibre reinforcement shows similar strength and ductility properties as concrete with natural aggregates. Using the synergy of positive effects of increased recycled coarse aggregate content, reduced participation of cementitious materials, and improved tensile behaviour by incorporating fibres in the concrete mixture is believed to be an option for green concrete with improved resistance to aggressive environmental influences. Cost-effective and environmentally friendly methods to advance fibre-reinforced concrete sustainability imply increasing the recycled aggregate content and lowering the consumption of cementitious materials with improved behaviour in exploitation.

Impact of variations in the molarity of sodium hydroxide on metakaolin-ground granular blast-furnace slag-based geopolymer concrete

2024-05-27T11:25:44+02:00

The present study investigates the optimization of geopolymer concrete mixes with the addition of metakaolin and ground granular blast-furnace slag as binding agents, ensuring a sustainable and eco-friendly alternative to conventional concrete. In this study, different proportions of the input parameters, such as the molarity of sodium hydroxide, ratio of sodium silicate to sodium hydroxide, and ratio of fixed alkali activator to binder have been considered. Attributes such as compressive strength, ultra-sonic pulse velocity, electricity resistance, mass loss, and strength variation due to acid attack for six geopolymer concrete mixes have been evaluated at different ambient curing periods. In addition, the mathematical relationship, i.e., linear regression, between these properties was also evaluated. The results show that a sodium silicate to sodium hydroxide ratio of 1,8; n sodium-hydroxide molarity of 14, and an alkali activator to binder ratio of 0,45 demonstrated the highest strength (43,3 MPa), electrical resistivity (35,1 K.Ohm.cm), and pulse velocity (4,2 km/s) with the minimal effect of H2SO4 solution on mass (1,2 %) and strength (5,8 %). Additionally, statistical analysis indicated a strong relationship of compressive strength with other properties, which improved as the curing days extended from 28 (Avg. R2=0,68) to 56 (Avg. R2=0,74) days. The outcomes of the study are expected to contribute to the advancement of sustainable construction by providing relevant data regarding material selection, ensuring quality, and optimizing geopolymer concrete production with metakaolin and ground granular blast-furnace slag.

Analysis of homogeneity and isotropy of the flow in the watercourses by applying the RAPS and IPTA methods

2024-05-16T09:00:16+02:00

Due to the frequent climatic changes occurring worldwide, which are related to extreme meteorological parameters as well as human activities, it is obvious that these influence the flow regimes of rivers. River flow is the most important factor determining the hydrological regime of any river. This has a substantial influence on the water resources and the environment surrounding the river. Hydrotechnical structures are also dimensioned on the basis of the flow as the primary input parameter. The flow conditions have different properties and correlations with the material of the river bed. In this paper, possible dependencies and phenomena are investigated using real case studies on two rivers in Croatia - examples of river courses in alluvium and karst areas - with regard to homogeneity and isotropy analyses. For this purpose, rescaled adjusted partial sums and innovative polygon trend analysis methods will be applied on the form of a combination of methods at the same watercourses. It has been shown that the analysed time series of the flows do not exhibit homogeneity and isotropy. In addition, fluctuations and irregularities were detected in the same time series. This is key information for determining the reliability of the flow forecast.

Deficiencies of technical specifications in tender documentation for construction project

2024-03-26T15:53:52+01:00

In the context of tender documentation for construction projects in the Czech Republic, technical specifications define the content and scope of work to be conducted using drawing documentation and a list of works, supplies and services. In practice, such documents are often burdened with errors (deficiencies) that can have different causes and impacts on the success of a project in terms of cost, time and quality. This study aims to explore the perception of the probability of occurrence and degree of impact of errors from various perspectives including risk factors, causes, possible effects, responsibility and the role of stakeholders. Data collected from experienced construction professionals in the Czech Republic show that documentation errors mainly affect project constraints in terms of cost and time and are often underestimated by investors concerning their impact and the probability of occurrence. Several recommendations are formulated to serve as preventive measures contributing to the elimination of errors and their early detection.

Development of single and multi-coil MR damper subjected to cyclic loading for structural vibration control

2024-04-29T17:59:27+02:00

The magnetorheological (MR) damper can dissipate energy from a vibrating system with low power consumption, making it one of the most popular semi-active damping devices. This study compares single- and multi-coil dampers subjected to cyclic loading. A magnetic oil-based MR fluid is synthesized with 50% carbonyl iron and 50 % synthetic oil, resulting in maximum damping force and minimum sedimentation. A three-dimensional model of the MR damper is created using AutoCAD and is fabricated. Single- and multi-coil MR dampers with a 3000 N capacity are designed and fabricated. The MR dampers are experimentally tested in a universal testing machine with a 1000 kN capacity for various input currents from 1 to 3 A. As the current increases, the damping force also increases in both the single- and multi-coil MR dampers. The multi-coil MR damper has a maximum damping force of 2628 N at a 15 mm amplitude, and the single-coil MR damper has a maximum damping force of 1868 N. A numerical simulation of the magnetic properties of the single- and multi-coil MR dampers is conducted using the finite-element method magnetics. A spring is placed at the top of the piston pole and bottom of the piston to make the MR damper semi-active. The fabricated MR damper can be used in seismic-resistant structures and as a base isolator to protect the structure from vibrations. In addition to civil engineering, it can be used in the development of adaptive prosthetics and orthotic devices, providing dynamic support.