Experimental Study on the Effect of Elongation Degree on the Cracking of Highly-Reinforced R/C Members

The main objective of this research is to study the phenomenon of cracking in the R/C structural elements, in particular the columns and the walls, and more particularly in the extreme regions of the walls, namely the boundary columns. Various parameters of the phenomenon of cracking will be studied, e.g., load influence, tensile strain, etc. It has to be noted the fact that load application is a monotonic axial tensile loading that simulates the strain condition that takes place at the boundary edges of reinforced concrete seismic walls. Specifically, this type of loading simulates the tensile loading that takes place during the first semi-cycle of loading under seismic dynamic events. Experimental research takes place by the construction and use of a group of 4 experimental specimens subjected to different degrees of elongation. This test group examines the tensile parameter and how it affects the cracking. The test specimens in question are all reinforced with the same high longitudinal reinforcement ratio (3.68%) and subjected to tensile degrees 10‰, 20‰, 30‰ and 50‰. Significant conclusions are reached on cracking, e.g., its extent, the size of the cracks, their positions, minimum crack width, maximum crack width, average crack width, number of cracks, etc. © 2022, Avestia Publishing. All rights reserved

EXPERIMENTAL RESEARCH ON IMPROVEMENT OF THE DUCTILITY OF R/C SEISMIC WALLS THROUGH SLIP PREVENTION WITH THE USE OF STEEL RHS

Several researchers propose placing diagonal reinforcing bars at the base of the wall to treat the shear slip, while others have suggested various ways to address this problem associated with halting the effects incurred by the through-crack in the base of the wall during cyclic loading. An indicative proposal of the bibliography is the use of large diameter reinforcement bars in the web of the wall as vertical reinforcements, so as to be able to better control the shear action through the dowel action of these bars. The two aforementioned proposals, while adequately addressing the phenomenon of shear slip, present significant disadvantages. The use of diagonal reinforcement is very difficult to construct, because of the density of the existing reinforcement in the base of the walls, which involves compromising good concrete condensation. Also, the use of large diameter vertical reinforcement along the length of the whole wall section, including its web, is a strongly uneconomical solution. This work examines a solution without the aforementioned side-effects. The innovation of the present work is the fact that it positions stoppers in combination with the use of conventional reinforcing bars at positions in the critical zones of the walls, in order to prevent the expected slip along the through-crack in the base of the rigidly supported wall. The work is experimental and includes two stages. The first stage was carried out with the construction of six test specimens, which can be considered as preliminary base specimens used for a first examination of the mechanical behavior of the walls with integrated steel hollow beams at their ends. These test results are a prelude to the second stage of the present study, including the experimental investigation of the seismic mechanical properties of a wall specimen, detailed either with conventional reinforcement according to EC8 or with the same conventional reinforcement but including also steel hollow beams at its confined edges. © 2022. Ingegneria Sismica. All Rights Reserved

Experimental and Numerical Study of Strain Degree of Medium-Reinforced Prism Specimens

Lateral instability of seismic walls is a catastrophic phenomenon which can affect severely the seismic behaviour of reinforced concrete multi-story buildings. It can even lead to the total collapse of multi-story buildings affecting human safety and having socioeconomical consequences, too. In the framework of this work, the influence of the degree of tension on the phenomenon of transverse instability of reinforced concrete seismic walls is examined. This investigation is both experimental and analytical and includes 4 test specimens. These specimens model the edges at the end of seismic walls. All columns simulate only the extreme reinforced areas of the walls, in order to study the basic mechanism of the phenomenon. The detailing of the specimens includes of 4 rebars with 8 mm diameter and 2 rebars with 10 mm diameter. The geometric dimensions are the same for all specimens. What differentiates the specimens from each other is the degree of tension they have sustained. More specifically, the tensile degrees used are 1%, 2%, 3%and 5%. Extreme earthquake action needs to be considered and that is the reason for using in the work herein large elongation degrees, e.g., 3% and 5%. The numerical investigation follows the experimental investigation using appropriate statistical software and finite elements. The resulting load-strain diagrams prove the very good correlation that exists between the test results and the analyses. The elastic branch, the yielding point and the plastic branch coincide very good for all four test specimens. Basic conclusion is that the degree of elongation is a very crucial mechanical parameter that affects tremendously the behavior of the boundary edges of structural walls. © 2022, Avestia Publishing. All rights reserved

Does the design according to the seismic zone affect the environment and the manufacturing cost of a 5-storey R/C building with a conventional plan?

The main scope of the present research is the analysis, dimensioning and estimation of the cost of a five-storey reinforced concrete building, which is similarly constructed in three different seismic hazard zones (ZI, ZII, ZIII). The ground plan of the building is a conventional floor plan with solid reinforced concrete slabs. The cross-sections of the structural members remain stable, except for the columns whose cross-sections are reduced in height. The aim of the present study is to analyze how the cost of manufacturing the load-bearing structure of a reinforced concrete building is affected by the seismic risk of the area, if that influence is significant and in what extent. Moreover, along with the construction cost, the possible influence to the environment is studied, too. © Published under licence by IOP Publishing Ltd

In site geotechnical investigations in the city of Larissa and influence on the construction environment

Field testing is often a very reliable way to determine the mechanical properties of soil materials and in some cases the most appropriate and unique way to obtain accurate measurements. Geotechnical engineers and engineering geologists perform geotechnical investigations to obtain information on the physical and mechanical properties of soil and rock underlying (and sometimes adjacent to) a site to design earthworks and foundations for proposed structures. The object of the present work is the recording of the geotechnical data of the center and districts of the city of Larissa, the knowledge of which is necessary for the construction and erection of construction works, as well as the characteristics and points that need special attention in each area. Finally important conclusions refer to the construction culture, that project authorities and contractors should draw on, accordingly. © Published under licence by IOP Publishing Ltd

Assessment principles for the mechanical behavior of clay soils

The factors that determine the geotechnical behavior of soils are mainly their composition, the size of their grains and their moisture content. The design of a soil structure or foundation project must ensure the shear adequacy of the soil in all phases of construction and throughout the life of the project. However, the shear strength, in general, of the soil is not "constant" but depends on key external factors such as the prehistory of loads, the time and succession of load states, the overpressure of the pore water as well as other factors such as relative density, or any preload, the pressure field, the rate of change of the intensive state, etc. The influence of the deformations as well as the change of the intensive state during the sampling should not be ignored. Unlike other materials, in clay materials the determination of shear strength and its interpretation is a very complex problem. The aim of this article is to search for the mechanical behavior of clay soils (lignite, kaolinite, marl) as shown by the laboratory illustration related with the problems on shear strength of materials, based on the results of experimental research. © 2021, World Scientific and Engineering Academy and Society. All rights reserved

Study of the Effect of a Seismic Zone to the Construction Cost of a Five-Story Reinforced Concrete Building

Greece is divided into three earthquake hazard zones: Zone I, Zone II and Zone III. In the present research work, the same building in the three seismic zones in Greece was modeled, analyzed and dimensioned. Then, the construction cost of its structural body was estimated. The building modeling was performed in SAP2000 using frame elements. The analysis of the building was performed by dynamic spectral analysis methods using the design spectrum EC8. A five-story building with a standard rectangular floor plan per floor was used. The purpose of this research paper is to demonstrate whether the cost of construction of a load-bearing body of a reinforced concrete (R/C) building is influenced by the area of an earthquake hazard through a comparative analytical estimation of construction costs. It was determined if this impact is important and to what extent. Helpful conclusions were drawn in relation to the influence of seismicity on the construction cost of the load-bearing structure of R/C buildings. Furthermore, the probable environmental impact was examined. © 2022 by the authors

Speed limits and accident rates on highways around the world, is there a correlation?

The objective of this study stands for the investigation and evaluation of accidents that take place on highways, in comparison with speed limits. The main body of this research is based on the collection of highways speed limits from different countries around the globe regarding to years, 2010, 2017 and 2018. Secondly, accident rates are collected from highway authorities, as well as from international literature. Subsequently, a statistical analysis of the collected data is conducted and finally leads to an equation that links and correlates the speed limit values and the number of accidents. The results of this statistical analysis show that speed limit plays a certain and distinctive role in the accident rate value. However, one of the interesting findings, stands for the non-continuously increasing number of accidents in the speed limit range, from the lowest to the highest value, meaning that there is an inflection point in the graph of the correlation equation. To be noted, that in terms of this study, the aforementioned correlation is independent of other factors that could affect the accident rate, such as vehicles condition, technology, road network length and condition. © Published under licence by IOP Publishing Ltd