Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

In this study, the dynamic behavior of one of the prominent structures in Istanbul, Üsküdar Observation Tower (UOT) has been investigated. The structural system of the tower is formed by a reinforced concrete circular tube having 2.8 meters outside diameter with a 40 centimeter thickness. By referring to the ground level, it starts from -18.2 meter due to five basement stories around the tower and its height is 44 meters. Two reinforced concrete floors were partially hanged over at 36 meter and 40 meter in height. The tower has an independent structural system from the ground level but a non-structural cladding assembly connects it to an adjacent building in the complex. With the mentioned structural features, Ambient Vibration Survey (AVS) was utilized to obtain the dynamic characteristics of UOT by Peak Picking (PP) method. The obtained dynamic properties were discussed with the peculiarities of UOT. While the performed analysis revealed the ineffectiveness of the adjacent building and the underground stories in the dynamic behavior of UOT, the torsion action of the floors has been noted. A numerical model has also been constructed to obtain the dynamic characteristics of UOT by Finite Element Analysis (FEA). The model calibration required to increase the code-based modulus of elasticity of the concrete by 23% for pairing the experimental and numerical dynamic properties. The reasons of the increase and the correlation between AVS and FEA were discussed. 

Transverse joint spacing is one of the fundamental input parameters in structural design of jointed plain concrete pavement (JPCP). It has to be determined considering many factors to produce a well-performing and cost-effective JPCP. In this study, a comprehensive evaluation of transverse joint spacing in JPCP was carried out based on the followings: (1) guidelines based on previous studies, the Federal Highway Administration and the American Concrete Pavement Association recommendations were summarized; (2) empirical and mechanistic-empirical (M-E) pavement design methodologies were reviewed; (3) current state highway agency practices in USA were surveyed as part of this study and the survey results were documented; (4) effects of joint spacing on JPCP performance were evaluated based on field observations; and (5) lastly, an economic analysis was performed to evaluate effects of joint spacing on life-cycle costs. This study demonstrated that a joint spacing between 15-18 ft (4.6-5.5 m) seems to be provide a safe zone for both performance and cost effectiveness.

In this study, the effect of particle size of quartz sand on the fresh and hardened properties of engineered cementitious composites (ECC) was investigated. For this purpose, three ECC mixtures that are identical except for the gradation of quartz sands used in their composition were designed. One of the mixtures includes a combination of quartz sands with amounts determined by the Andreasen and Andersen particle size optimization model while the remaining two have a finer and a coarser gradation. In the fresh state, mini slump, mini V-funnel and bleeding tests were applied, and rheological parameters were determined according to Bingham and modified Bingham models by using a rotational viscometer. In the hardened state, flexural strengths, mid-span deflections and numbers of microcracks formed under flexural loading were determined at 7 and 28 days. It was observed that the particle size optimization of the quartz sand can provide a balance between flow and bleeding characteristics of ECC mixtures. Although a reduction in flexural strength occurred at both ages in the optimized ECC mixture, the deflection capacity and the crack formation capacity under loading were significantly increased, reaching a deflection value of over 10 mm with at least 11 cracks formed during the test. As a result, it was revealed that particle size optimization can yield a mixture with the highest ductility without compromising the workability of ECC.

The purpose of this research is to evaluate the mineralogical, physical, and mechanical properties of compressed earth blocks (CEB) stabilized with lime and mineral admixtures easily obtained in Argentina: natural pozzolans and brick powder. the admixture mineralogical composition and their pozzolanic potential as well as the development of hydraulic phases upon reaction with calcium hydroxide (lime) were determined, emphasizing the formation of hydrated cementing compounds. Samples with different percentages of lime and mineral additions were prepared in order to test their compressive strength, wet erosion resistance, and water absorption, and contrasting the results with those of their counterparts stabilized exclusively with lime or cement. The results obtained allow us to affirm that both the brick powder and the pozzolan used have pozzolanic properties and, in combination with calcium hydroxide, form amorphous phases of C-(A)-S-H. However, the use of small amounts of both additions in combination with hydrated air lime in the manufacture of CEB, compared to CEB samples stabilized only with hydrated air lime, adversely affected their physical and mechanical properties.

Spiral ties with rectangular cross sections have been developed as a new technology in construction, reducing the workforce in the reinforcement production series, because the worker does not have to place the tie reinforcement for the columns on the construction site. In this paper, a new type of tie was evaluated in short tie-columns subjected to axial compression to be applied in confined masonry. A comparison was made in this paper among spiral ties, with circular and rectangular cross sections, and traditional closed ties. The main aim of this research is to prove that these rectangular cross-section spiral ties can be used in tie columns for confined masonry structures. Twenty-one specimens were tested to investigate their structural behavior. As a part of the results, maximum loads, strains, load-displacement curves, and stress-strain relationships, were obtained based on testing standards, for both specimens and component materials. In addition, the fracture energy in compression and the ductility index were assessed. These results demonstrate that spiral ties with rectangular cross sections have an efficient structural response compared to traditional and circular spiral ties.

In the presented paper, an attempt has been made to first find the permeability of the Euphorbia tortilis cactus (ETC) concrete by the water permeability method and infiltration method. After that, the flexural strength of the ETC RC beam wrapped with AFRP kelvar 149 is carried out by a 2-point load test.  This research aimed to develop a more durable, flexural, and sustainable beam under static load. Based on the state-of-the-art information available in the literature, 3-layer Kelvar 149 AFRP is considered as a laminate to solve the deflections of the ETC beam. In this project, RCC beams were strengthened by ETC and aramid FRP sheets. Novel results are obtained by different layers and patterns of Aramid FRP sheets. Based on the investigation 3-layers Kelvar 149 perform well than a normal concrete beam. As no result based on hydraulic conductivity and drying shrinkage of a beam with AFRP laminates are available in the literature, the obtained results are validated with the finite element method (ABAQUS) under static load conditions. 

Structural design has a significant impact on the overall cost of truss structures. In order to reduce the cost of a structure it is important to support designers' decision making starting from the early design phase. In this study, an optimization workflow is proposed, developed and implemented using well known generative design and Building Information Modeling (BIM) tools to achieve a cost-optimal design of a truss structure in the early design phase. Generative design aims to develop products that are lighter, stronger, more efficient and tailored to the specific needs of end users. Generative design tools allow users to create efficient designs via optimizing factors such as cost, weight, energy efficiency and performance. The aim of this study was to develop an optimization workflow to find and model the minimum weight / minimum cost design alternative in the early design phase using generative design, structural analysis and BIM tools in an integrated manner. The goal for the optimization was determined as finding the minimum weight (thus minimum cost) structure among the generated design alternatives. The single span steel truss was selected as the structure to be optimized, and optimization scenarios were prepared and implemented to determine the structural components of the truss with minimum weight. The results demonstrated that through integrated use of structural analysis, generative design and BIM tools minimum-weight truss design can be realized easily and practically.

In the presented research paper, investigated the torsional performance of reinforced concrete beams with light emissions grade of cement utilizing Carbon fiber and its relative investigation with aramid fiber, for its torsional conduct, utilizing both exploratory and insightful strategies. A distinctive example of its strips folded over RC beams and the torsional conduct of these restrengthened beams is considered. Carbon fiber (CF) is utilized as outside support. Reinforced concrete beam retrofitted with CF tried for torsional disappointment utilizing lever arms exposed to torque. The beams have dimensions of 150mm in width and 200mm in depth and 1 m long, as planned according to IS456-2000. Three bars are intended for a twist. Steel has a stronger ultimate strength but a lower density than aramid FRP, as well as being easier to install and requiring no interim support until it reaches its full strength. The impact of various sorts and designs of CF on the initial stage of breaking load, extreme load conveying limit, and disappointment method of the beam are thought about and its relative examination utilizing finite element programming with aramid fiber gives a better outcome for additional investigation.

The main purpose of this study is to determine the stress-strain behaviour of a rigid circular footing placed on recycled rubber tyre-reinforced granular filling built on weak soil. For this purpose, model plate loading tests were carried out on reinforced/unreinforced granular filling built with natural aggregates (NA) or construction and demolition waste materials (CDW). The rubber tyre used for reinforcement has become a waste material by completing its service life but it has retained its typical cylindrical shape. In model plate loading tests, the effects of the granular fillings, the type of fillings material and the placement of whole rubber tyre and/or geotextile in the granular fillings were investigated. Depending on the results of tests, it was determined that the bearing capacity was increased by reinforcing with the rubber tyre and/or the geotextile. Furthermore, it was specified that the highest increase in bearing capacity was occurred case of by reinforcing with the geotextile together with the rubber tyre of the granular filling. The CDW and the NA fills reinforced with geotextile together with the rubber tyre increased the bearing capacity of weak soils by 6.59 and 8.49 times, respectively, for the 5% deformation ratio. On the other hand, it was reported that although the bearing capacity of the NA was higher than that of the CDW, the bearing capacity of the reinforced CDW approached that of the NA.

In the recent years, there has been increased in concern on shrinkage response of concrete systems as abundant cases of premature deterioration were reported. The major factors affecting the deterioration of a concrete system are quality, composition and the surrounding environment. In connection with this, the work concentrates on the study of long-term effects on materials used in the concrete (supplementary cementitious materials SCMs) such as fly ash, slag and silica fume as a blended concrete system. To carry out the experimental work, nine concrete mixes were designed for varying proportions of SCMs and w/b. Evolution of compressive strength, elastic modulus, shrinkage and selected durability parameters were tested under a controlled laboratory condition. Based on the work, it was found that the inclusion of fly ash, slag and silica fume on the concrete systems enhance the compressive strength in long-term, also the shrinkage response of the ternary systems shows a substantial reduction in the measured strain. Durability performance like chloride penetration and sorptivity had a better performance in comparison with the conventional concrete systems.