Techno Press
Tp_Editing System.E (TES.E)
Login Search


cac
 
CONTENTS
Volume 15, Number 6, June 2015
 

Abstract
In order to construct a multiscale model for the compressive strength of plain concrete columns with circular cross section subjected to central longitudinal compressive load, a column failure mechanism is proposed based on the theory of internal instability. Based on an energy analysis, the multiscale model is developed to describe the failure process and predict the column\'s compressive strength. Comparisons of the predicted results with experimental data show that the proposed multiscale model can accurately represent both the compressive strength of the concrete columns with circular cross section, and the effect of column size on its strength.

Key Words
multiscale modeling; analytical solution; energy analysis; fracture mechanics; circular concrete columns; size effet

Address
Han-liang Wu: School of Civil Engineering, Beijing Jiaotong University, Beijing, 100044, PR China;
Bridge Technology Research Center, Research Institute of Highway, Ministry of Transportation, Beijing, 100088, P R China
Yuan-feng Wang: School of Civil Engineering, Beijing Jiaotong University, Beijing, 100044, PR China

Abstract
The remaining service life (RSL) of buildings has been an important issue in the field of building and facility management, and its development is also one of the essential factors for achieving sustainable infrastructure. Since the estimation of RSL of buildings is heavily affected by the subjectivity of individual inspector or engineer,much effort has been placed in the development of a rational method that can estimate the RSL of existing buildings more quantitatively using objective measurement indices. Various uncertain factors contribute to the deterioration of the structural performance of buildings, and most of the common building structures are constructed not with a single structural member but with various types of structural components (e.g., beams, slabs, and columns) in multistory floors. Most existing RSL estimation methods, however, consider only an individual factor. In this study, an estimation method for RSL of concrete buildings is presented by utilizing a fuzzy theory to consider the effects of multiple influencing factors on the deterioration of durability (e.g., concrete carbonation, chloride attack, sulfate attack), as well as the current structural condition (or damage level) of buildings.

Key Words
remaining service life; chloride attack; concrete carbonation; sulfate attack; Choquet integral;

Address
Hae-Chang Cho,Deuck Hang Lee,Hyunjin Ju and Kang Su Kim : Department of Architectural Engineering, University of Seoul, 163 Seoulsiripdaero, Dongdaemun-gu, Seoul 130-743, Republic of Korea
Ki-Hyun Kim and Paulo J.M.Monteiro : Department of Civil & Environmental Engineering, University of California, 725 Davis Hall, Berkeley,CA 94720, USA


Abstract
The flow of freshly mixed cement-based material shows thixotropy, which implies some difficulties on robust measurement of its rheological properties: The flow curve of thixotropic materials depends on the used protocol. For examples, higher viscosity is obtained when the rate of shear strain is more quickly increased. Even though precise measurement and modelling of the concrete rheology needs to consider the thixotropic effect, engineers in the concrete field prefer considering as a non-thixotropic Herschel-Bulkley fluid, even more simply Bingham fluid. That is due to robustness of the measurement and application in casting process. In the aspect of simplification, this papers attempts to mimic the thixoropic flow by the non-thixotropic Herschel-Bulkley model. Disregarding the thixotropy of cement based materials allows us to adopt the rheological concept in the field. An optimized protocol to measure the Bingham parameters was finally found based on the accuracy and reproducibility test of cement paste samples, which minimizes the error of simulation stemming from the assumption of non-thixotropy.

Key Words
cement paste; suspension; thixotropy; rheology; flow simulation; VOF techniques

Address
Jae Hong Kim and Hye Rim Jang : School of Urban and Environmental Engineering, Ulsan National Institute of Science and Technology,Ulsan 698-798, Republic of Korea
Hong Jae Yim : Department of Construction and Disaster Prevention Engineering, Kyungpook National University,2559 Gyeongsang-daero, Sangju, Gyeongsangbuk-do, 742-711, Republic of Korea

Abstract
The aim of this study is to determine the earthquake performances of reinforced concrete (R/C) residential buildings in Turkey and to analyze the parameters that affect the performance. The performance of Turkish residential buildings, determined by their levels of damage, directly relates to their structural systems. Damage parameters observed from previous earthquakes define structural parameters selected to be used in the present study. Five different types of frame R/C buildings were modeled. For the analysis, the model buildings vary according to the number of stories, column sizes, and reinforcement and concrete strength parameters. The analyses consider gravity forces and earthquake loads through 1975 and 2007 Turkish design codes. In a total of 720 different R/C buildings were investigated for the analysis to obtain capacity curves. A performance evaluation was employed by considering the Turkish design code (TDC-2007). The current study ignores irregularities such as soft stories or short columns. The study ignores irregularities such as soft stories or short columns. The study\'s analysis considers a comparison of the parameters\' influence on the structural performance of the model buildings.

Key Words
earthquake performance evaluation; Turkish R/C residential buildings; Turkish Design Codes; pushover analyses; performance estimation

Address
Kasim Armagan Korkmaz : Istanbul Technical University, Civil Engineering Department, Istanbul, Turkey
Fuat Demir and Tugce Yenice : Suleyman Demirel University, Civil Engineering Department, Isparta, Turkey

Abstract
The aim of this study is to provide experimental data regarding the compressive, shear and torsional strength of self-compacting concrete (SCC) used in rectangular beams, and then comparing the results with the equations presented by the CSA A23.3-04 and ACI 318-11. In fact, the gathered information in this field is quite useful for calibrating the computer models of other researchers. The other goal of this study was to investigate the effects of silica fume and superplasticizer dosages on the mechanical properties of SCC. In this research, SCC is made based on 16 different type mixing layout. Also two normal concrete(NC) or vibrating concrete are constructed to compare the results of SCC and NC. This work concentrated on concrete mixes having water/binder ratios of 0.45 and 0.35, which contained constant total binder contents of 400 kg/m3 and 500 kg/m3, respectively. The percentages of silica fume that replaced cement were 0% and 10%. The superplasticizer dosages utilized in the mixtures were 0.4%, 0.8%, 1.2% and 1.6% of the weight of cement. Beam dimensions used in this test were 30x30x120cm3. The results of this research indicated that shear and torsional strength of SCC beams to be used in computer models can be calculated utilizing the equations presented in CSA A23.3-04 and ACI 318-11.

Key Words
self-compacting concrete; rectangular beam; shear strength; torsional strength

Address
Moosa Mazloom and Amiali Saffari : Department of Civil Engineering, Shahid Rajaee Teacher Training University, Tehran, Iran
Morteza Mehvand : Department of Civil Engineering, University of Science and Culture, Tehran, Iran

Abstract
The focus of the present study is to investigate both local and global behaviour of a precast concrete sandwich panel. The selected prototype consists of two reinforced concrete layers coupled by a system of cold-drawn steel profiles and one intermediate layer of insulating material. High-definition nonlinear finite element (FE) models,based on 3D brick and 2D interface elements, are used to assess the capacity of this technology under shear, tension and compression. Geometrical nonlinearities are accounted via large displacement-large strain formulation, whilst material nonlinearities are included, in the series of simulations, by means of Von Mises yielding criterion for steel elements and a classical total strain crack model for concrete; a bond-slip constitutive law is additionally adopted to reproduce steel profile-concrete layer interaction. First, constitutive models are calibrated on the basis of preliminary pull and pull-out tests for steel and concrete, respectively. Geometrically and materially nonlinear FE simulations are performed, in compliance with experimental tests, to validate the proposed modeling approach and characterize shear,compressive and tensile response of this system, in terms of global capacity curves and local stress/strain distributions. Based on these experimental and numerical data, the structural performance is then quantified under various loading conditions, aimed to reproduce the behaviour of this solution during production, transport, construction and service conditions.

Key Words
precast panel; composite panel; steel profile; shear response; void shape; FE models; interface elements

Address
E.Brunesi and M.Deyanova : ROSE Programme, UME School, IUSS Pavia, Institute for Advanced Study Via Ferrata 1, 27100 Pavia (PV), Italy
R. Nascimbene : EUCENTRE, European Centre for Training and Research in Earthquake Engineering Via Ferrata 1, 27100 Pavia (PV), Italy
C.Pagani and S.Zambelli : B.S.Italia, Styl-Comp group Via Stezzano 16, 24050 Zanica (BG), Italy
S.Zambelli

Abstract
The electrical resistivity of air-dried, saturated, and carbonated concretes with different mixture proportions was monitored to evaluate and quantify the influence of the age of the specimen, carbonation, and curing condition. After 28 days of curing, four prepared specimens were stored in a vacuum chamber with 5% CO2 for 330 days to make carbonated specimens. Four of the specimens were placed in water, and four specimens were cured in air until the end of the experiments. It was observed that the electrical resistivity of the carbonated specimens increased as carbonation progressed due to the decrease of porosity and the increase of hydrated products. Therefore, in order to estimate the durability of concrete, its carbonation depth was used as the measurement of electrical resistivity. Moreover, an increase of electrical resistivity for air-dried and saturated concretes was observed as a function of age of the specimen. From the relationship between chloride diffusivity provided by Yoon et al. (2007) and the measurements of electrical resistivity, it is expected that the results well be of significant use in calibrating chloride diffusivity based on regular measurements of electrical resistivity during concrete construction.

Key Words
carbonation depth; chloride diffusivity; curing condition; durability; electrical resistivity

Address
In-Seok Yoon: Department of Construction Information Engineering, Induk University, 12 Choansan-ro, Nowon-gu, Seoul 139-749, Republic of Korea
Seongwon Hong : Engineering Research Institute, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-744, Republic of Korea
Thomas H.K. Kang : Department of Architecture and Architectural Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-744, Republic of Korea

Abstract
An advanced continuum-based multi-physical single particle model was recently introduce for the hydration of tricalcium silicate (C3S). In this model, the dissolution and the precipitation events are modeled as two different yet simultaneous chemical reactions. Product precipitation involves a nucleation and growth mechanism wherein nucleation is assumed to happen only at the surface of the unreacted core and product growth is characterized via a two-step densification mechanism having rapid growth of a low density initial product followed by slow densification. Although this modeling strategy has been shown to nicely mimic all stages of C3S hydration – dissolution, dormancy (induction), the onset of rapid hydration, the transition to slow hydration and prolonged reaction – the major criticism is that many adjustable parameters are required. If formulated correctly, however, the model parameters are shown here to be statistically independent and significant.

Key Words
precast modeling; parameter estimation; statistical confidence; hydration; cement

Address
Joseph J. Biernacki and Manohar Gottapu : Department of Chemical Engineering, Tennessee Technological University, Cookeville, Tennessee, USA


Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2017 Techno-Press
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Tel: +82-42-828-7996, Fax : +82-42-828-7997, Email: info@techno-press.com