Search results for: normal concrete

Authors: Mourad Morsli, Mohamed Tahiri, Azzedine Samdi

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The Cities are the urbanized territories most favorable to the consumption of resources (materials, energy). In Morocco, the economic capital Casablanca is one of them, with its 4M inhabitants and its 60% share in the economic and industrial activity of the kingdom. In the absence of legal status in force, urban development has favored the generation of millions of tons of demolition and construction waste scattered in open spaces causing a significant nuisance to the environment and citizens. Hence the main objective of our work is to valorize concrete waste. The representative wastes are mainly concrete, concrete, and fired clay bricks, ceramic tiles, marble panels, gypsum, and scrap metal. The work carried out includes: geolocation with a combination of artificial intelligence, GIS, and Google Earth, which allowed the estimation of the quantity of these wastes per site; then the sorting, crushing, grinding, and physicochemical characterization of the collected samples allowed the definition of the exploitation ways for each extracted fraction for integrated management of the said wastes. In the present work, we proceeded to the exploitation of the fractions obtained after sieving the representative samples to incorporate them in the manufacture of new ecological materials for construction. These formulations prepared studies have been tested and characterized: physical criteria (specific surface, resistance to flexion and compression) and appearance (cracks, deformation). We will present in detail the main results of our research work and also describe the specific properties of each material developed.

Keywords: demolition and construction waste, GIS combination software, inert waste recovery, ecological materials, Casablanca, Morocco

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Authors: Bineet Kumar

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Many civil engineering infrastructures frequently encounter repetitive loading during their service life. Due to the inherent complexity observed in concrete, like quasi-brittle materials, understanding the fatigue behavior in concrete still posesa challenge. Moreover, the fracture process zone characteristics ahead of the crack tip have been observed to be different in fatigue loading than in the monotonic cases. Therefore, it is crucial to comprehend the energy dissipation associated with the fracture process zone (FPZ) due to repetitive loading. It is well known that stiffness degradation due to cyclic loadingprovides a better understanding of the fracture behavior of concrete. Under repetitive load cycles, concrete members exhibit a two-stage stiffness degradation process. Experimentally it has been observed that the stiffness decreases initially with an increase in crack length and subsequently increases. In this work, an attempt has been made to propose an analytical expression to predict energy dissipation and later the stiffness degradation as a function of crack length. Three-point bend specimens have been considered in the present work to derive the formulations. In this approach, the expression for the resultant stress distribution below the neutral axis has been derived by correlating the bending stress with the cohesive stresses developed ahead of the crack tip due to the existence of the fracture process zone. This resultant stress expression is utilized to estimate the dissipated energydue to crack propagation as a function of crack length. Further, the formulation for the stiffness degradation has been developed by relating the dissipated energy with the work done. It can be used to predict the critical crack length and fatigue life. An attempt has been made to understand the influence of stress amplitude on the damage pattern by using the information on the rate of stiffness degradation. It has been demonstrated that with the increase in the stress amplitude, the damage/FPZ proceeds more in the direction of crack propagation compared to the damage in the direction parallel to the span of the beam, which causes a lesser rate of stiffness degradation for the incremental crack length. Further, the effect of loading frequency has been investigated in terms of stiffness degradation. Under low-frequency loading cases, the damage/FPZ has been found to spread more in the direction parallel to the span, in turn reducing the critical crack length and fatigue life. In such a case, a higher rate of stiffness degradation has been observed in comparison to the high-frequency loading case.

Keywords: fatigue life, fatigue, fracture, concrete

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Authors: Henar Martín-Sanz García, Eleni Chatzi, Eugen Brühwiler

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Located on the shore of Geneva Lake, in Switzerland, the Chillon Viaducts are two parallel structures consisted of post-tensioned concrete box girders, with a total length of 2 kilometers and 100m spans. Built in 1969, the bridges currently accommodate a traffic load of 50.000 vehicles per day, thereby holding a key role both in terms of historic value as well as socio-economic significance. Although several improvements have been carried out in the past two decades, recent inspections demonstrate an Alkali-Aggregate reaction in the concrete deck and piers reducing the concrete strength. In order to prevent further expansion of this issue, a layer of 40 mm of Ultra High Performance Fiber Reinforced cement-based Composite (UHPFRC) (incorporating rebars) was casted over the slabs, acting as a waterproof membrane and providing significant increase in resistance of the bridge structure by composite UHPFRC – RC composite action in particular of the deck slab. After completing the rehabilitation works, a Structural Monitoring campaign was installed on the deck slab in one representative span, based on accelerometers, strain gauges, thermal and humidity sensors. This campaign seeks to reveal information on the behavior of UHPFRC-concrete composite systems, such as increase in stiffness, fatigue strength, durability and long-term performance. Consequently, the structural monitoring is expected to last for at least three years. A first insight of the analyzed results from the initial months of measurements is presented herein, along with future improvements or necessary changes on the deployment.

Keywords: composite materials, rehabilitation, structural health monitoring, UHPFRC

Procedia PDF Downloads 275

Authors: Alejandro Salicrup, Riacrdo Gelhman, Geetha Gopalakrishna

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The main aim of this session is to have a panel to discuss specific steps for the integration of traditional, complementary and alternative medicine (TCAM) with conventional oncology for enhancing treatment practices at the global level, specifically in low-and-middle-income-countries (LMICs). Concrete current and required programs for strengthening Integrative Oncology research in LMICs will also be discussed. Case Studies from Latin America, Asia, Europe and Africa will discuss and highlight 1) What is working regarding treatment practices in integrative oncology in their countries/regions providing concrete examples 2) What is not working on this integration for cancer treatment in their countries/regions with concrete examples and 3) What are the challenges and opportunities for research related to integrative oncology treatment. Discussion will include potential next steps and potential mechanisms to enhance global integrative oncology research aimed to enhance the use of TCAM therapies and strengthening cancer treatment in LMICs.

Keywords: global cancer treatment, integrative oncology research, low and middle income countries, traditional, complementary and alternative medicines

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Authors: Henry Munoz, Muhammad Mohsan, Takashi Kiyota

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Strength and deformability characteristics of a liquefiable sand deposit including the development of earthquake-induced shear stress and shear strain as well as soil softening via the progressive degradation of shear modulus were studied via shaking table experiments. To do so, a model of a liquefiable sand deposit was constructed and densely instrumented where accelerations, pressures, and displacements at different locations were continuously monitored. Furthermore, the confinement effects on the strength and deformation characteristics of the liquefiable sand deposit due to an external surcharge by placing a heavy concrete slab (i.e. the model of an actual structural rigid pavement) on the ground surface were examined. The results indicate that as the number of seismic-loading cycles increases, the sand deposit softens progressively as large shear strains take place in different sand elements. Liquefaction state is reached after the combined effects of the progressive degradation of the initial shear modulus associated with the continuous decrease in the mean principal stress, and the buildup of the excess of pore pressure takes place in the sand deposit. Finally, the confinement effects given by a concrete slab placed on the surface of the sand deposit resulted in a favorable increasing in the initial shear modulus, an increase in the mean principal stress and a decrease in the softening rate (i.e. the decreasing rate in shear modulus) of the sand, thus making the onset of liquefaction to take place at a later stage. This is, only after the sand deposit having a concrete slab experienced a higher number of seismic loading cycles liquefaction took place, in contrast to an ordinary sand deposit having no concrete slab.

Keywords: liquefaction, shear modulus degradation, shaking table, earthquake

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Authors: Vahid Ayan, Joshua R Omer, Alireza Khavandi, Mukesh C Limbachiya

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In Iran, utilization of reclaimed asphalt pavement (RAP) aggregate has become a common practice in pavement rehabilitation during the last ten years. Such developments in highway engineering have necessitated several studies to clarify the technical and environmental feasibility of other alternative materials in road rehabilitation and maintenance. The use of recycled concrete aggregates (RCA) in asphalt pavements is one of the major goals of municipality of Tehran. Nevertheless little research has been done to examine the potential benefits of local RCA. The objective of this study is laboratory investigation of incorporating RCA into RAP for use in unbound subbase application. Laboratory investigation showed that 50%RCA+50%RAP is both technically and economically appropriate for subbase use.

Keywords: Roads & highways, Sustainability, Recycling & reuse of materials

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Authors: Azin Shakibabarough, Mojtaba Valinejadshoubi, Ashutosh Bagchi

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Catastrophic bridge failure happens due to the lack of inspection, lack of design and extreme events like flooding, an earthquake. Bridge Management System (BMS) is utilized to diminish such an accident with proper design and frequent inspection. Visual inspection cannot detect any subsurface defects, so using Non-Destructive Evaluation (NDE) techniques remove these barriers as far as possible. Among all NDE techniques, Ground Penetrating Radar (GPR) has been proved as a highly effective device for detecting internal defects in a reinforced concrete bridge deck. GPR is used for detecting rebar location and rebar corrosion in the reinforced concrete deck. GPR profile is composed of hyperbola series in which sound hyperbola denotes sound rebar and blur hyperbola or signal attenuation shows corroded rebar. Interpretation of GPR images is implemented by numerical analysis or visualization. Researchers recently found that interpretation through visualization is more precise than interpretation through numerical analysis, but visualization is time-consuming and a highly subjective process. Automating the interpretation of GPR image through visualization can solve these problems. After interpretation of all scans of a bridge, condition assessment is conducted based on the generated corrosion map. However, this such a condition assessment is not objective and precise. Condition assessment based on structural integrity and strength parameters can make it more objective and precise. The main purpose of this study is to present an automated interpretation method of a reinforced concrete bridge deck through a visualization technique. In the end, the combined analysis of the structural condition in a bridge is implemented.

Keywords: bridge condition assessment, ground penetrating radar, GPR, NDE techniques, visualization

Procedia PDF Downloads 143

Authors: Mahtab Abdollahi Sarvi, Siamak Epackachi, Ali Imanpour

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Reinforced concrete shear walls are commonly used as the lateral load-resisting system of mid- to high-rise office or residential buildings around the world. Design of such systems is often governed by wind rather than seismic effects, in particular in low-to-moderate seismic regions. The current design philosophy as per the majority of building codes under wind loads require elastic response of lateral load-resisting systems including reinforced concrete shear walls when subjected to the rare design wind load, resulting in significantly large wall sections needed to meet strength requirements and drift limits. The latter can highly influence the design in upper stories due to stringent drift limits specified by building codes, leading to substantial added costs to the construction of the wall. However, such walls may offer limited to moderate over-strength and ductility due to their large reserve capacity provided that they are designed and detailed to appropriately develop such over-strength and ductility under extreme wind loads. This would significantly contribute to reducing construction time and costs, while maintaining structural integrity under gravity and frequently-occurring and less frequent wind events. This paper aims to investigate the over-strength and ductility capacity of several imaginary office buildings located in Edmonton, Canada with a glance at earthquake design philosophy. Selected models are 10- to 25-story buildings with three types of reinforced concrete shear wall configurations including rectangular, barbell, and flanged. The buildings are designed according to National Building Code of Canada. Then fiber-based numerical models of the walls are developed in Perform 3D and by conducting nonlinear static (pushover) analysis, lateral nonlinear behavior of the walls are evaluated. Ductility and over-strength of the structures are obtained based on the results of the pushover analyses. The results confirmed moderate nonlinear capacity of reinforced concrete shear walls under extreme wind loads. This is while lateral displacements of the walls pass the serviceability limit states defined in Pre standard for Performance-Based Wind Design (ASCE). The results indicate that we can benefit the limited nonlinear response observed in the reinforced concrete shear walls to economize the design of such systems under wind loads.

Keywords: concrete shear wall, high-rise buildings, nonlinear static analysis, response modification factor, wind load

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Authors: Saida Dorbani, M'hammed Badaoui, Djilali Benouar

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This paper deals with the effect of the building design and epicentral distance on the storey lateral displacement, for several reinforced concrete buildings (6, 9 and 12 stories), with three floor plans: symmetric, mono symmetric, and unsymmetrical. These structures are subjected to seismic accelerations from the Boumerdes earthquake (Algeria, May 21st, Mw=6.5). The objective of this study is to highlight the impact of the fundamental period and epicentral distance on storey displacements for a given earthquake. The seismic lateral displacement is carried out in both longitudinal and transverse direction by the response spectrum method.

Keywords: natural period, epicenter distance, reinforced concrete buildings, storey displacement

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Authors: Devinder Singh, Arvind Kumar, Rajneesh Kumar

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The general solution of the equations for a homogeneous isotropic microstretch thermo elastic medium with mass diffusion for two dimensional problems is obtained due to normal and tangential forces. The integral transform technique is used to obtain the components of displacements, microrotation, stress and mass concentration, temperature change and mass concentration. A particular case of interest is deduced from the present investigation.

Keywords: normal force, tangential force, microstretch, thermoelastic, the integral transform technique, deforming force, microstress force, boundary value problem

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Authors: S. A. Faizi, S. Yoshitomi

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The optimal design procedure of buckling restrained braces (BRBs) in reinforced concrete (RC) building structures can provide the distribution of horizontal stiffness of BRBs at each story, which minimizes story drift response of the structure under the constraint of specified total stiffness of BRBs. In this paper, a simple rule is proposed to convert continuous horizontal stiffness of BRBs into sectional sizes of BRB which are available from standardized section list assuming realistic structural design stage.

Keywords: buckling restrained brace, building engineering, optimal damper placement, structural engineering

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Authors: Sharifah M. Syed Mohsin, Sayid J. Azimi, Abdoullah Namdar

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The present article reports the findings of a study into the behavior of oil palm shell reinforced concrete (OPSRC) beams with the addition of kenaf fibres. The work aim is to examine the potential of using kenaf fibres to improve the strength and ductility of the OPSRC beams and also observe its potential in serving as part of shear reinforcement in the beams. Two different arrangements of the shear links in OPSRC beams with a selection of kenaf fibres (amount of [10kg/m] ^3 and [20kg/m] ^3) content are tested under monotonic loading. In the first arrangement, the kenaf fibres are added to the beam which has full shear reinforcement to study the structural behavior of OPSRC beams with fibres. In the second arrangement, the spacing between the shear links in the OPSRC beams are increased by 50% and experimental work is carried out to study the effect of kenaf fibres without compromising the beams strength and ductility. The results show that the addition of kenaf fibres enhanced the load carrying capacity, ductility and also altered the failure mode of the beams from a brittle shear mode to a flexural ductile one. Furthermore, the study depicts that kenaf fibres are compatible with OPSRC and suggest prospective results.

Keywords: oil palm shell reinforced concrete, kenaf fibres, peak strength, ductility

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Authors: M. Zielina, W. Dabrowski, E. Radziszewska-Zielina

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Several different cements have been tested to evaluate their potential to leach calcium, chromium and aluminum ions in soft water environment. The research allows comparing some different cements in order to the potential risk of water contamination. This can be done only in the same environment. To reach the results in reasonable short time intervals and to make heavy metals measurements with high accuracy, demineralized water was used. In this case the conditions of experiments are far away from the water supply practice, but short time experiments and measurably high concentrations of elements in the water solution are an important advantage. Moreover leaching mechanisms can be recognized, our experiments reported here refer to this kind of cements evaluation.

Keywords: concrete corrosion, hydrogen sulfide, odors, reinforced concrete sewers, sewerage

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Authors: Anicet Dansou

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Textile reinforced concrete (TRC)is increasingly used nowadays in various fields, in particular civil engineering, where it is mainly used for the reinforcement of damaged reinforced concrete structures. TRC is a composite material composed of multi- or uni-axial textile reinforcements coupled with a fine-grained cementitious matrix. The TRC composite is an alternative solution to the traditional Fiber Reinforcement Polymer (FRP) composite. It has good mechanical performance and better temperature stability but also, it makes it possible to meet the criteria of sustainable development better.TRCs are highly anisotropic composite materials with nonlinear hardening behavior; their macroscopic behavior depends on multi-scale mechanisms. The characterization of these materials through numerical simulation has been the subject of many studies. Since TRCs are multiscale material by definition, numerical multi-scale approaches have emerged as one of the most suitable methods for the simulation of TRCs. They aim to incorporate information pertaining to microscale constitute behavior, mesoscale behavior, and macro-scale structure response within a unified model that enables rapid simulation of structures. The computational costs are hence significantly reduced compared to standard simulation at a fine scale. The fine scale information can be implicitly introduced in the macro scale model: approaches of this type are called non-classical. A representative volume element is defined, and the fine scale information are homogenized over it. Analytical and computational homogenization and nested mesh methods belong to these approaches. On the other hand, in classical approaches, the fine scale information are explicitly introduced in the macro scale model. Such approaches pertain to adaptive mesh refinement strategies, sub-modelling, domain decomposition, and multigrid methods This research presents the main principles of numerical multiscale approaches. Advantages and limitations are identified according to several criteria: the assumptions made (fidelity), the number of input parameters required, the calculation costs (efficiency), etc. A bibliographic study of recent results and advances and of the scientific obstacles to be overcome in order to achieve an effective simulation of textile reinforced concrete in civil engineering is presented. A comparative study is further carried out between several methods for the simulation of TRCs used for the structural reinforcement of reinforced concrete structures.

Keywords: composites structures, multiscale methods, numerical modeling, textile reinforced concrete

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Authors: Iman Mohseni

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Current studies indicate that neglecting the effect of intermediate diaphragms might lead to highly conservative values for bending moment distribution factors and result in non-economic designs for skew bridges. This paper reports on a parametric study performed on 160 prototypes of straight and skew concrete multicell box-girder bridges. The obtained results were used to develop practical expressions to account for the diaphragm effects on American Association of State Highway and Transportation Officials formulas for live load distribution factors. It was observed that decks with internal transverse diaphragms perpendicular to the longitudinal webs are the best arrangement for load distribution in skew bridges.

Keywords: box bridges, truck, distribution factor, diaphragm

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Authors: Kahil Amar, Nekmouche Aghiles, Titouche Billal, Hamizi Mohand, Hannachi Naceur Eddine

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The ductility is an important parameter in the nonlinear behavior of portal structures reinforced concrete. It may be explained by the ability of the structure to deform in the plastic range, or the geometric characteristics in the map may influence the overall ductility. Our study is based on the influence of geometric slenderness (Lx / Ly) on the overall ductility of these structures, a study is made on a structure has 05 floors with varying the column section of 900 cm², 1600 cm² and 1225 cm². A slight variation in global ductility is noticed as (Lx/Ly) varies; however, column sections can control satisfactorily the plastic behavior of buildings.

Keywords: ductility, nonlinear behavior, pushover analysis, geometric slenderness, structural behavior

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Authors: Junkyeong Kim, Jooyoung Park, Aoqi Zhang, Seunghee Park

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The tensile force of Pre-Stressed Concrete (PSC) girder is the most important factor for evaluating the performance of PSC girder bridges. To measure the tensile force of PSC girder, several NDT methods were studied. However, conventional NDT method cannot be applied to the real-size PSC girder because the PS tendons could not be approached. To measure the tensile force of real-size PSC girder, this study proposed embedded EM sensor based tensile force estimation method. The embedded EM sensor could be installed inside of PSC girder as a sheath joint before the concrete casting. After curing process, the PS tendons were installed, and the tensile force was induced step by step using hydraulic jacking machine. The B-H loop was measured using embedded EM sensor at each tensile force steps and to compare with actual tensile force, the load cell was installed at each end of girder. The magnetization energy loss, that is the closed area of B-H loop, was decreased according to the increase of tensile force with regular pattern. Thus, the tensile force could be estimated by the tracking the change of magnetization energy loss of PS tendons. Through the experimental result, the proposed method can be used to estimate the tensile force of the in-situ real-size PSC girder bridge.

Keywords: tensile force estimation, embedded EM sensor, magnetization energy loss, PSC girder

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Authors: Shakir Iqbal, Muhammad Aqeel, Asghar Ali Shah, Aftab Hussain

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The present study was aimed to investigate and compare the emotional indicators of patients with schizophrenia on Draw a Person test in Pakistan. Draw a Person test was administered on a sample of 400 (Schizophrenia patients=200, Normal=200) age ranged from 20 to 50 years. The data was collected from two provinces of Pakistan (Punjab and Khyber Pakhtun Khwa). The sample was selected by the age levels. According to the Koppitz method of scoring a list of 40 Emotional indicators was selected that were derived from the literature review. It was found that 26 out of 40 emotional indicators (EIs) on Draw a Person test significantly differentiated between patients with schizophrenia and normal (healthy) population. Chi square analysis of the study indicated that 23 EIs were found significant at (p=.001) level, while three EIs were found significant at (P=.05) levels. It was also found that 9 exclusive and 4 frequent EIs on Human Figure Drawings may be significant diagnostic emotional indicators for schizophrenia. It was found that DAP test can be used as a diagnostic tool with the battery of psychological tests such as MCMI-III, MMPI, MSE, HTP for schizophrenia in Pakistan.

Keywords: draw a person test, normal population, Schizophrenia patients, psychological sciences

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Authors: Rajai Al-Rousan

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This paper presents a proposed analytical model for predicting the shear strength of reinforced concrete beams strengthened with CFRP composites as external reinforcement. The proposed analytical model can predict the shear contribution of CFRP composites of RC beams with an acceptable coefficient of correlation with the tested results. Based on the comparison of the proposed model with the published well-known models (ACI model, Triantafillou model, and Colotti model), the ACI model had a wider range of 0.16 to 10.08 for the ratio between tested and predicted ultimate shears at failure. Also, an acceptable range of 0.27 to 2.78 for the ratio between tested and predicted ultimate shears by the Triantafillou model. Finally, the best prediction (the ratio between the tested and predicted ones) of the ultimate shear capacity is observed by using Colotti model with a range of 0.20 to 1.78. Thus, the contribution of the CFRP composites as external reinforcement can be predicted with high accuracy by using the proposed analytical model.

Keywords: predicting, shear capacity, reinforced concrete, beams, strengthened, externally, CFRP composites

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Authors: N. Attari, S. Amziane, M. Chemrouk

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A large number of old buildings have been identified as having potentially critical detailing to resist earthquakes. The main reinforcement of lap-spliced columns just above the joint region, discontinuous bottom beam reinforcement, and little or no joint transverse reinforcement are the most critical details of interior beam column joints in such buildings. This structural type constitutes a large share of the building stock, both in developed and developing countries, and hence it represents a substantial exposure. Direct observation of damaged structures, following the Algiers 2003 earthquake, has shown that damage occurs usually at the beam-column joints, with failure in bending or shear, depending on geometry and reinforcement distribution and type. While substantial literature exists for the design of concrete frame joints to withstand this type of failure, after the earthquake many structures were classified as slightly damaged and, being uneconomic to replace them, at least in the short term, suitable means of repairs of the beam column joint area are being studied. Furthermore; there exists a large number of buildings that need retrofitting of the joints before the next earthquake. The paper reports the results of the experimental programme, constituted of three beam-column reinforced concrete joints at a scale of one to three (1/3) tested under the effect of a pre-stressing axial load acting over the column. The beams were subjected at their ends to an alternate cyclic loading under displacement control to simulate a seismic action. Strain and cracking fields were monitored with the help a digital recording camera. Following the analysis of the results, a comparison can be made between the performances in terms of ductility, strength and mode of failure of the different strengthening solution considered.

Keywords: fibre reinforced polymers, joints, reinforced concrete, beam columns

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Authors: H. Nikzad, S. Yoshitomi

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In this paper, the optimal seismic design of reinforced concrete shear wall-frame building structures was done using structural optimization. The optimal section sizes were generated through structural optimization based on linear static analysis conforming to American Concrete Institute building design code (ACI 318-14). An analytical procedure was followed to validate the accuracy of the proposed method by comparing stresses on structural members through output files of MATLAB and ETABS. In order to consider the difference of stresses in structural elements by ETABS and MATLAB, and to avoid over-stress members by ETABS, a stress constraint ratio of MATLAB to ETABS was modified and introduced for the most critical load combinations and structural members. Moreover, seismic design of the structure was done following the International Building Code (IBC 2012), American Concrete Institute Building Code (ACI 318-14) and American Society of Civil Engineering (ASCE 7-10) standards. Typical reinforcement requirements for the structural wall, beam and column were discussed and presented using ETABS structural analysis software. The placement and detailing of reinforcement of structural members were also explained and discussed. The outcomes of this study show that the modification of section sizes play a vital role in finding an optimal combination of practical section sizes. In contrast, the optimization problem with size constraints has a higher cost than that of without size constraints. Moreover, the comparison of optimization problem with that of ETABS program shown to be satisfactory and governed ACI 318-14 building design code criteria.

Keywords: structural optimization, seismic design, linear static analysis, etabs, matlab, rc shear wall-frame structures

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Authors: Manali Jain, Neeta Singh, Raunaq Fatima, Soniya Nityanand, Mandakini Pradhan, Chandra Prakash Chaturvedi

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Isolated Congenital Heart Defect (ICHD) is the major cause of neonatal death worldwide among all forms of CHDs. A significant proportion of fetuses with ICHD die in the neonatal period if no treatment is provided. Recently, stem cell therapies have emerged as a potential approach to ameliorate ICHD in children. ICHD is characterized by cardiac structural abnormalities during embryogenesis due to alterations in the cardiomyogenic properties of a pool of cardiac progenitors/ stem cells associated with fetal heart development. The stem cells present in the amniotic fluid (AF) are of fetal origin and may reflect the physiological and pathological changes in the fetus during embryogenesis. Therefore, in the present study, the cardiomyogenic potential of AF-MSCs derived from fetuses with ICHD (ICHD AF-MSCs) has been evaluated and compared with that of AF-MSCs of structurally normal fetuses (normal AF-MSCs). Normal and ICHD AF-MSC were analyzed for the expression of cardiac progenitor markers viz., stage-specific embryonic antigen-1 (SSEA-1), vascular endothelial growth factor 2 (VEGFR-2) and platelet-derived growth factor receptor-alpha (PDGFR-α) by flow cytometry. The immunophenotypic characterization revealed that ICHD AF-MSCs have significantly lower expression of cardiac progenitor markers VEGFR-2 (0.14% ± 0.6 vs.48.80% ± 0.9; p <0.01), SSEA-1 (70.86% ± 2.4 vs. 88.36% ±2.7; p <0.01), and PDGFR-α (3.92% ± 1.8 vs. 47.59% ± 3.09; p <0.01) in comparison to normal AF-MSCs. Upon induction with 5’-azacytidine for 21 days, ICHD AF-MSCs showed a significantly down-regulated expression of cardiac transcription factors such as GATA-4 (0.4 ± 0.1 vs. 6.8 ± 1.2; p<0.01), ISL-1 (2.3± 0.6 vs. 14.3 ± 1.12; p<0.01), NK-x 2-5 (1.1 ± 0.3 vs. 14.1 ±2.8; p<0.01), TBX-5 (0.4 ± 0.07 vs. 4.4 ± 0.3; p<0.001), and TBX-18 (1.3 ± 0.2 vs. 4.19 ± 0.3; p<0.01) when compared with the normal AF-MSCs. Furthermore, immunocytochemical staining revealed that both types of AF-MSCs could differentiate into cardiovascular lineages and express cardiomyogenic, endothelial, and smooth muscle actin markers, viz., cardiac troponin (cTNT), CD31, and alpha-smooth muscle actin (α-SMA). However, normal AF-MSCs showed an enhanced expression of cTNT (p<0.001), CD31 (p<0.01), and α-SMA (p<0.05), compared to ICHD AF-MSCs. Overall, these results suggest that the ICHD-AF-MSCs have a defective cardiomyogenic differentiation potential and that the defects in these stem cells may have a role in the pathogenesis of ICHD.

Keywords: amniotic fluid, cardiomyogenic potential, isolated congenital heart defect, mesenchymal stem cells

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Authors: Aloke Bapli, Debabrata Seth

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Graphene oxide (GO) is the two-dimensional (2D) nanoscale allotrope of carbon having several physiochemical properties such as high mechanical strength, high surface area, strong thermal and electrical conductivity makes it an important candidate in various modern applications such as drug delivery, supercapacitors, sensors etc. GO has been used in the photothermal treatment of cancers and Alzheimer’s disease etc. The main idea to choose GO in our work is that it is a surface active molecule, it has a large number of hydrophilic functional groups such as carboxylic acid, hydroxyl, epoxide on its surface and in basal plane. So it can easily interact with organic fluorophores through hydrogen bonding or any other kind of interaction and easily modulate the photophysics of the probe molecules. We have used different spectroscopic techniques for our work. The Ground-state absorption spectra and steady-state fluorescence emission spectra were measured by using UV-Vis spectrophotometer from Shimadzu (model-UV-2550) and spectrofluorometer from Horiba Jobin Yvon (model-Fluoromax 4P) respectively. All the fluorescence lifetime and anisotropy decays were collected by using time-correlated single photon counting (TCSPC) setup from Edinburgh instrument (model: LifeSpec-II, U.K.). Herein, we described the photophysics of a hydrophilic molecule 7-(n,n׀-diethylamino) coumarin-3-carboxylic acid (7-DCCA) in the reverse micelles containing GO. It was observed that photophysics of dye is modulated in the presence of GO compared to photophysics of dye in the absence of GO inside the reverse micelles. Here we have reported the solvent relaxation and rotational relaxation time in GO containing reverse micelle and compare our work with normal reverse micelle system by using 7-DCCA molecule. Normal reverse micelle means reverse micelle in the absence of GO. The absorption maxima of 7-DCCA were blue shifted and emission maxima were red shifted in GO containing reverse micelle compared to normal reverse micelle. The rotational relaxation time in GO containing reverse micelle is always faster compare to normal reverse micelle. Solvent relaxation time, at lower w₀ values, is always slower in GO containing reverse micelle compare to normal reverse micelle and at higher w₀ solvent relaxation time of GO containing reverse micelle becomes almost equal to normal reverse micelle. Here emission maximum of 7-DCCA exhibit bathochromic shift in GO containing reverse micelles compared to that in normal reverse micelles because in presence of GO the polarity of the system increases, as polarity increases the emission maxima was red shifted an average decay time of GO containing reverse micelle is less than that of the normal reverse micelle. In GO containing reverse micelle quantum yield, decay time, rotational relaxation time, solvent relaxation time at λₑₓ=375 nm is always higher than λₑₓ=405 nm, shows the excitation wavelength dependent photophysics of 7-DCCA in GO containing reverse micelles.

Keywords: photophysics, reverse micelle, rotational relaxation, solvent relaxation

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Authors: Mohammed Mahmood, Walid Tizani, Carlo Sansour

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In this paper, experimental testing and numerical analysis were used to investigate the effect of tube thickness on the face bending for concrete filled hollow sections connected to other structural members using Extended Hollobolts. Six samples were tested experimentally by applying pull-out load on the bolts. These samples were designed to fail by column face bending. The main variable in all tests is the column face thickness. Finite element analyses were also performed using ABAQUS 6.11 to extend the experimental results and to quantify the effect of column face thickness. Results show that, the column face thickness has a clear impact on the connection strength and stiffness. However, the amount of improvement in the connection stiffness by changing the column face thickness from 5 mm to 6.3 mm seems to be higher than that when increasing it from 6.3 mm to 8 mm. The displacement at which the bolts start pulling-out from their holes increased with the use of thinner column face due to the high flexibility of the section. At the ultimate strength, the yielding of the column face propagated to the column corner and there was no yielding in its walls. After the ultimate resistance is reached, the propagation of the yielding was mainly in the column face with a miner yielding in the walls.

Keywords: anchored bolted connection, Extended Hollobolt, column faces bending, concrete filled hollow sections

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Authors: Jelena R. Pejović, Nina N. Serdar

Abstract:

This paper presents an analysis of the “Performance-Based” seismic design method, in order to overcome the perceived disadvantages and limitations of the existing seismic design approach based on force, in engineering practice. Bearing in mind, the specificity of the earthquake as a load and the fact that the seismic resistance of the structures solely depends on its behaviour in the nonlinear field, traditional seismic design approach based on force and linear analysis is not adequate. “Performance-Based” seismic design method is based on nonlinear analysis and can be used in everyday engineering practice. This paper presents the application of this method to eight-story high reinforced concrete building with combined structural system (reinforced concrete frame structural system in one direction and reinforced concrete ductile wall system in other direction). The nonlinear time-history analysis is performed on the spatial model of the structure using program Perform 3D, where the structure is exposed to forty real earthquake records. For considered building, large number of results were obtained. It was concluded that using this method we could, with a high degree of reliability, evaluate structural behavior under earthquake. It is obtained significant differences in the response of structures to various earthquake records. Also analysis showed that frame structural system had not performed well at the effect of earthquake records on soil like sand and gravel, while a ductile wall system had a satisfactory behavior on different types of soils.

Keywords: ductile wall, frame system, nonlinear time-history analysis, performance-based methodology, RC building

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Authors: Mohd Ritzman Abdul Karim, Zhaohui Huang

Abstract:

A current focus in seismic engineering practice is the development of seismic design approach that focuses on the performance-based design. Performance-based design aims to design the structures to achieve specified performance based on the damage limit states. This damage limit is more restrictive limit than life safety and needs to be carefully estimated to avoid damage in piers due to failure in transverse reinforcement. In this paper, a different perspective of damage limit states has been explored by integrating two damage control material limit state, concrete and reinforcement by introduced parameters such as expected yield stress of transverse reinforcement where peak tension strain prior to bar buckling is introduced in a recent study. The different perspective of damage limit states with modified yield displacement and the modified plastic-hinge length is used in order to predict damage-control target displacement for reinforced concreate (RC) bridge pier. Three-dimensional (3D) finite element (FE) model has been developed for estimating damage target displacement to validate proposed damage limit states. The result from 3D FE analysis was validated with experimental study found in the literature. The validated model then was applied to predict the damage target displacement for RC bridge pier and to validate the proposed study. The tensile strain on reinforcement and compression on concrete were used to determine the predicted damage target displacement and compared with the proposed study. The result shows that the proposed damage limit states were efficient in predicting damage-control target displacement consistent with FE simulations.

Keywords: damage-control target displacement, damage limit states, reinforced concrete bridge pier, yield displacement

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Authors: Ichrak Hamrouni, Tariq Ouahbi, Natalija Lhuissier, Saïd Taibi, Mehrez Jemai, Olivier Crumeyrolle, Hatem Zenzri

Abstract:

Raw earth is the oldest building technique used for over 11 centuries, thanks to its various benefits. The most known raw earth construction technics are compressed earth blocks, rammed earth, raw earth concrete, and daub. The raw earth can be stabilized with hydraulic binders, mixed by fibers, or hyper-compacted in order to improve its mechanical behaviour. Moreover, raw earth is characterized by a low thermal conductivity what make it a good thermal insulator, and it has a very important capacity to condense and evaporate relative humidity. In this context, many researches have been developed. They have shown that the mechanical characteristics of earth materials increase with the hyper-compaction and adding fibers or hydraulic binders. Besides, other researches have been determined the thermal and hygroscopic properties of raw earth. They have shown that this material able to contribute to moisture and heat control in constructions. Its hygrothermal properties are better than fired earth bricks and concrete. The aim of this study is to evaluate the thermal and hygrometric behavior of raw earth material using experimental tests allows to determine the main Hygrothermal properties such as the water Vapour permeability and thermal conductivity and compare the results with those of other building materials such as fired clay bricks and cement concrete is presented.

Keywords: raw earth material, hygro-thermal, thermal conductivity, water vapour permeability, building materials, building materials

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Authors: S. Al-Fadala, J. Chakkamalayath, S. Al-Bahar, A. Al-Aibani, S. Ahmed

Abstract:

Globally, the use of pozzolan in blended cement is gaining great interest due to the desirable effect of pozzolan from the environmental and energy conservation standpoint and the technical benefits they provide to the performance of cement. The deterioration of concrete structures in the marine environment and extreme climates demand the use of pozzolana cement in concrete construction in the Gulf region. Also, natural sources of cement clinker materials are limited in the Gulf region, and cement industry imports the raw materials for the production of Portland cement, resulting in an increase in the greenhouse gas effect due to the CO₂ emissions generated from transportation. Even though the Gulf region has vast deposits of natural pozzolana, it is not explored properly for the production of high performance concrete. Hence, an optimum use of regionally available natural pozzolana for the production of blended cement can result in sustainable construction. This paper investigates the effect of incorporating natural pozzolan sourced from the Gulf region on the performance of blended cement in terms of heat evolution and strength development. For this purpose, a locally produced Ordinary Portland Cement (OPC) and pozzolan-incorporated blended cements containing different amounts of natural pozzolan (volcanic ash) were prepared on laboratory scale. The strength development and heat evolution were measured and quantified. Promising results of strength development were obtained for blends with the percentages of Volcanic Ash (VA) replacement varying from 10 to 30%. Results showed that the heat of hydration decreased with increase in percentage of replacement of OPC with VA, indicating increased retardation in hydration due to the addition of VA. This property could be used in mass concreting in which a reduction in heat of hydration is required to reduce cracking in concrete, especially in hot weather concreting.

Keywords: blended cement, hot weather, hydration, volcanic ash

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Authors: Robert J. Thomas, Colton Bedke, Andrew Sorensen

Abstract:

The exemplary mechanical performance and durability of ultra-high performance concrete (UHPC) has led to its rapid emergence as an advanced cementitious material. The uncharacteristically high mechanical strength and ductility of UHPC makes it a promising potential material for defense structures which may be subject to highly dynamic loads like impact or blast. However, the mechanical response of UHPC under dynamic loading has not been fully characterized. In particular, there is a need to characterize the energy absorption of UHPC under high-frequency shear loading. This paper presents preliminary results from a parametric study of the dynamic shear energy absorption of UHPC using the Charpy impact test. UHPC mixtures with compressive strengths in the range of 100-150 MPa exhibited dynamic shear energy absorption in the range of 0.9-1.5 kJ/m. Energy absorption is shown to be sensitive to the water/cement ratio, silica fume content, and aggregate gradation. Energy absorption was weakly correlated to compressive strength. Results are highly sensitive to specimen preparation methods, and there is a demonstrated need for a standardized test method for high frequency shear in cementitious composites.

Keywords: Charpy impact test, dynamic shear, impact loading, ultra-high performance concrete

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Authors: Sangdeok Lee, Sangwon Han, Changtaek Hyun

Abstract:

Construction defects are major components that result in negative impacts on project performance including schedule delays and cost overruns. Since construction defects generally occur when a few associated causes combine, a thorough understanding of defect causality is required in order to more systematically prevent construction defects. To address this issue, this paper uses association rule mining (ARM) to quantify the causality between defect causes, and social network analysis (SNA) to find indirect causality among them. The suggested approach is validated with 350 defect instances from concrete works in 32 projects in Korea. The results show that the interrelationships revealed by the approach reflect the characteristics of the concrete task and the important causes that should be prevented.

Keywords: causality, defect causes, social network analysis, association rule mining

Procedia PDF Downloads 363