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The effect of mixing method on capillary moisture content of concretes with recycled concrete aggregates

IOP Conference Series: Materials Science and engineering 2018年第1期385卷

作者： A Sicakova K Urban Institute of Environmental Engineering Faculty of Civil Engineering Technical University of Kosice Vysokoskolska 4 042 00 Kosice Slovakia Institute of Construction Technology and Management Faculty of Civil Engineering Technical University of Kosice Vysokoskolska 4 042 00 Kosice Slovakia

Recycled concrete aggregate represents a major environmental burden in the affected area and its use as an aggregate in concrete production is widespread in many countries. However, such aggregates have worse characteristics and strength than those of natural aggregate. In particular they have a higher absorption rate than natural aggregates, need much more water for mixing, and cause a high slump loss rate depending on the elapsed time. In this context, it is possible to monitor globally extensive research aimed on the elimination of improper properties of alternative aggregates, which are an obstacle to their application in concrete. The sorptivity expressed by capillary moisture content is a characteristic of moisture transport into the material, and recently it has been recognized as an important performance characteristic of durability. The paper is focused on the specific approach to concrete mixing as a way of the improvement of recycled aggregate´s surface using 3 variations of powders as coating materials and 2 kinds of aggregate. The changes in the capillary moisture content are compared and discussed. It is clear that the kind of coating material can influence this performance parameter significantly, so the careful design of mixing process together with the selection of powdery materials is essential. The triple mixing method was found to be promising for recycled concrete aggregate concrete, when fly ash or recycled concrete powder are used in the first stage of mixing. It is a favourable result, taking into account the perspective of the application of secondary raw materials for concrete production.

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An approach for evaluating fire resistance of steel beams considering creep effect

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Procedia engineering 2017年 210卷 544-550页

作者： Weiyong Wang Linbo Zhang College of Civil Engineering Chongqing University Chongqing 400045 China Key Laboratory of New Technology for Construction of Cities in Mountain Area (Ministry of Education) Chongqing University Chongqing 400045 China

Most of previous studies on fire resistance of restrained steel beams neglected creep effect due to lack of suitable creep model. This paper presents a finite element model (FEM) for accessing the fire resistance of restrained high strength Q460 steel beams by taking high temperature Norton creep model of steel into consideration. The validation of the established model is verified by comparing the axial force and deflection of restrained beams obtained by finite element analysis with test results. In order to explore the creep effect on fire response of restrained Q460 steel beams, the thermal axial force and deflection of the beams are also analyzed excluding creep effect. Results from comparison infer that creep plays a crucial role in fire response of restrained steel beam and neglecting the effect of creep may leads to unsafe design. A simplified design approach to determine the moment capacity of restrained Q460 steel beams is proposed based on the results of parametric studies by considering creep effect.

关键词： Fire resistance creep restrained beams high strength steel simplified approach

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Towards an automated damage detection system for miter gates on navigation locks: Detecting boundary condition degradation 11

Towards an automated damage detection system for miter gates...

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11th International Workshop on Structural Health Monitoring 2017: Real-Time Material State Awareness and Data-Driven Safety Assurance, IWSHM 2017

作者： Eick, Brian A. Spencer, Billie F. Smith, Matthew D. Alexander, Quincy G. Foltz, Stuart D. Construction Engineering Research Laboratory 2902 Newmark Drive ChampaignIL61822 United States Smart Structures Technology Laboratory Newmark Civil Engineering Laboratory University of Illinois Urbana-Champaign 205 N Mathews Avenue UrbanaIL61801 United States Army Engineer Research and Development Center 3909 Halls Ferry Road VicksburgMI39180 United States

ISBN: (纸本)9781605953304

Navigation locks are critical infrastructure components, and their closure for maintenance and repair can have significant impacts on the global economy. The current state of inspection and monitoring of lock components is generally to close the lock and perform a visual inspection. While structural health monitoring (SHM) of navigation locks is gaining acceptance, automation of the SHM process is lacking. This paper reports on efforts to develop an automated damage detection system for miter gates of navigation locks. The study focuses on using strain gage measurements to identify the redistribution of load throughout lock gates in the presence of damage. To eliminate the environmental variability in the data, a new damage sensitive feature is introduced, termed here as "slope" and defined as the derivative of the strain with respect to the water levels in the lock chamber. The slopes form a new, stationary time series effectively purged of environmental effects. Principal Component Analysis (PCA), a method of analyzing multivariate, stationary time series, is then used to detect significant changes in the statistics of slopes as an indication of damage. To validate the approach, damage is simulated in a finite element model, and the resulting changes in strain from the finite element model are superimposed on the measured data. The results demonstrate the potential of the proposed approach for detecting damage in navigational lock gates.

关键词： Locks (fasteners)

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Shear Strength of Engineered Cementitious Composites under Push-Off Loads

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Procedia engineering 2017年 210卷 53-60页

作者： Pei-Zhi Zhao Shao-Bo Kang Bo Yang Key laboratory of New Technology for Construction of Cities in Mountain Area (Chongqing University) Ministry of Education Chongqing China 400045 School of Civil Engineering Chongqing University Chongqing China 400045

This paper studies the shear strength of engineered cementitious composites (ECC) under push-off loads. In total six specimens were tested experimentally on conventional concrete and ECC specimens. The effects of concrete ductility and stirrups crossing the shear plane were investigated in the experimental programme. Test results showed that ECC specimens could reach substantially higher load capacities than concrete specimens as a result of its superior tensile ductility. In terms of failure modes, concrete specimens developed severe crushing and spalling near the shear plane, whereas only a dominant crack was formed in ECC specimens. After attaining the load capacity, ECC specimens with stirrups crossing the shear plane could sustain a certain level of residual forces when the slip across the shear plane was relatively large. Besides the shear strength, the dilatancy of specimens was measured to shed light on the differences between the shear behaviour of ECC and concrete specimens. Finally, conclusions were drawn from experimental results which can be used for the shear design of ECC members.

关键词： push-off test engineered cementitious composites shear strength residual stress

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An Occupational Profile of People Injured in Accidents at Work in the Polish construction Industry

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Procedia engineering 2017年 208卷 43-51页

作者： Bożena Hoła Mariusz Szóstak Wroclaw University of Science and Technology Faculty of Civil Engineering Department of Construction Methods and Management Wybrzeże Wyspiańskiego 27 building C-7 Wroclaw 50-370 Poland

The construction industry in Poland and in the world is characterized by a high level of threat to the life and health of workers. In accident processes, a man exists in a triple role, namely: a decision maker, a perpetrator of an accident and a victim. Statistical data published by the Central Statistical Office regarding the causes of accidents indicates that human causes account for around 60% of all reported cases. Identification of the factors affecting the accident rate and also the direct causes of accidents is the first step in determining the directions of preventive action. The aim of the research conducted by the authors of this article is to present the occupational characteristics of people injured in accidents at work in the Polish construction industry. The article presents the results obtained from the analysis of occupational accidents that occurred in the years 2008-2014 in five voivodships of Poland, namely: Kujawsko-Pomorskie, Slaskie, Lubelskie, Dolnoslaskie and Lubuskie. The paper identifies and examines the impact of the following characteristics: the employment status of a victim, occupation, age, length of service, preparation of the employee to perform duties at a workplace and the size of an enterprise in which the accident took place. 485 occupational accidents were analysed, 37% of which were fatal accidents, 61% were severe, and 2% were light.

关键词： accident at work construction industry occupational safety

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Determination of Properties and Heat Transfer Rate through building boundary of Corn Cob Cement Material for Applying to be construction Material

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Energy Procedia 2017年 138卷 217-222页

作者： Pakasit Hongthong Anan Pongtornkulpanich Kamonwan Chawna Division of Civil Engineering Faculty of Engineering and Architecture Rajamangala University of Technology Tawan-Ok Uthenthawai Campus Pathumwan District Bangkok 10330 Thailand Division of Construction Engineering Faculty of Engineering and Architecture Rajamangala University of Technology Tawan-Ok Uthenthawai Campus Pathumwan District Bangkok 10330 Thailand Division of General Education Faculty of Engineering and Architecture Rajamangala University of Technology Tawan-Ok Uthenthawai Campus Pathumwan District Bangkok 10330 Thailand

In order to reduce heat transferring through building boundary affecting the increase of energy efficiency, the development of property of construction material is significant. An effective way to be used is the utilization of agricultural waste, biomass such as palm, bagasse, coconut shell which has fiber structure, mixing with cement material to be formed as concrete. This research aims to develop and test the property of concrete, which have structure of mixing between corn cob and cement material. With the large amount of agricultural residue, corn cob is selected for this study. Test of physical, mechanical and thermal properties of corn cob cement material is performed. Comparison of property of cement materials consisting of different types of fibers, corn cob, palm, bagasse, coconut shell, is investigated one another. Two house models consisting of the structure of pure and corn cob cement materials with the same size of 2 x 2 m 2 in each are fabricated. Each house is positioned to face to the sun all day. Conduction heat transfer rate passing through boundary in each house models is determined and compared each other. Evaluation of suitability of use of corn cob cement material for applying with construction purpose is given.

关键词： Biomass fiber fiber cement property heat transfer rate

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Simulation of A Hot-rolled H-section Steel Beam Subject to Static Loading Based on Discrete Element Method

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Procedia engineering 2017年 210卷 312-319页

作者： Li-Qiang Zhou Bo Yang Key Laboratory of New Technology for Construction of Cities in Mountain Area (Chongqing University) Ministry of Education Chongqing 400045 China School of Civil Engineering Chongqing University Chongqing 400045 China

In this paper, a new discrete element method (DEM) containing particle flow code (PFC) is presented as an efficient-to-implement alternative to the existing finite element method (FEM) for simulating internal forces and deformations of a hot-rolled H-section steel beam subject to static loading. Unlike FEM, which is efficient to solve continuous problems, the PFC method can solve discontinuous problems, such as collapse procedure of structures, and the collapse procedure of the structure can be monitored at different times in a more time-saving way. First of all, a linear constitutive model in FEM was built to compare with the linear parallel bond model built in PFC, a hot-rolled H-section steel beam considering geometrically non-linearity subject to static loading was simulated and the simulation results were compared with theoretical solution and FEM results. Both internal forces and deformations before yielding were compared and good agreements were achieved. Secondly, with the object-oriented programming technique and the redeveloped interface of PFC, a user-defined parallel bond model was developed to consider material nonlinearity and compared with the bilinear constitutive model built in FEM. Both internal forces and deformations before and after yielding were compared and good agreements were observed. Thus, the DEM model adopted in this paper can be efficiently used to simulate the behavior of the H-section steel beam. In the future, the developed parallel bond model can be used to simulate the performance of H-section steel beam subject to vertical impact loading and three-dimensional steel framed structure subject to horizontal collision.

关键词： Discrete Element Method Simulation H-section Steel Beam Internal forces Deformations User-defined Parallel Bond Model

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Development of a groundwater model for a tropical eogenetic karst aquifer in Rote Island, Indonesia 37

Development of a groundwater model for a tropical eogenetic ...

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37th Hydrology and Water Resources Symposium 2016: Water, Infrastructure and the Environment, HWRS 2016

作者： Yejezkial Klaas, Dua Kudushana Singgih Imteaz, Monzur Alam Department of Civil and Construction Engineering Swinburne University of Technology Melbourne Australia Department of Civil Engineering Politeknik Negeri Kupang Kupang Indonesia

ISBN: (纸本)9781922107954

Groundwater is a very important source of drinking water for inhabitants living in a remote tropical karst island of Rote in Indonesia. In this island karst spring is the only dependable source of water throughout the year because of the intermittent river flow and porous nature of carbonate rocks in the island. Meanwhile, rapid regional development resulting in increased population and land use change in Rote Island could contribute to recharge depletion of karst springs. These situations may ultimately threaten the ability of the Mamar springs to continuously provide water for the community in Rote Island. In order to assess the effect of these anthropogenic stresses on future groundwater availability in the catchment a calibrated and validated groundwater model is needed. In this study a single-continuum model using MODFLOW was developed applying 50 x 50 m grid cell for spatial discretisation. Using Parameter Estimation (PEST) and geostatistical Pilot Point methods, hydraulic conductivity and specific yield values were estimated. The results of the simulations show good model performances both in calibration and validation steps. The outcome is highly useful for the evaluation of the current and projected conditions of the groundwater resources in accordance with climate change and for deciding the best management measures to cope with these scenarios. © 2017 Engineers Australia. All Rights Reserved.

关键词： Groundwater resources

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Neural networks prediction of critical responses related to top-down and bottom-up cracking in airfield concrete pavement 10th

Neural networks prediction of critical responses related to ...

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10th International Conference on the Bearing Capacity of Roads, Railways and Airfields, BCRRA 2017

作者： Rezaei-Tarahomi, A. Kaya, O. Ceylan, H. Gopalakrishnan, K. Kim, S. Brill, D.R. Department of Civil Construction and Environmental Engineering Iowa State University AmesIA United States FAA Airport Technology R&D Branch ANG-E262 William J. Hughes Technical Center Atlantic City International Airport NJ United States

ISBN: (纸本)9781138295957

In this study Artificial Neural Networks (ANNs) have been used to predict the critical responses calculated by a NIKE3D-FAA Finite Element (FE) tool, a fully implicit three-dimensional finite element model representing a significant modification of the NIKE3D program originally developed by the Lawrence Livermore National Laboratory (LLNL) of the U.S. Department of Energy. A synthetic database has been constructed by implementing a great deal of analysis of a concrete pavement structure using NIKE3D-FAA for a reasonable range of inputs. ANNs have been trained to produce the critical responses at the top and bottom of such slabs. These responses are tensile stresses with in-plane directions, shear stress, and deflection. The concrete pavement studied in this paper is a four-layer structure pavement subjected to mechanical loading by a Boeing heavy airplane (B777-300ER) and the loading effects of a temperature gradient in the slab. The ANN models were found to successfully predict critical pavement responses in all cases, with a minimum of 0.99 for the coefficient of determination (R2). The observed results exhibits how ANN models can both accurately predict critical responses used for designing and account for failures. Because the ANN models can accomplish rapid prediction of responses it is suggested that they have significant potential for producing accurate stress predictions in a fraction of the time needed to perform full 3D-FE computation. © 2017 Taylor & Francis Group, London.

关键词： Concrete pavements

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Modeling of strength and deformation of overconsolidated clays based on bounding surface plasticity

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Science China(Technological Sciences) 2016年第9期59卷 1452-1462页

作者： XIAO Yang[[ LIU HanLong SUN YiFei LIU Hong State Key Laboratory of Coal Mine Disaster Dynamics and Control Chongqing University Key Laboratory of New Technology for Construction of Cities in Mountain Area Chongqing University College of Civil Engineering Chongqing University Faculty of Engineering and Information Sciences University of Wollongong

An elastoplastic constitutive model for overconsolidated clays is established in the framework of the critical state theory and bounding surface plasticity theory. The bounding surface is defined as the maximum yield surface in the loading history. A yielding ratio, i.e., an internal variant, is defined as the size ratio of the current yield surface to the corresponding bounding surface. The yielding ratio instead of the overconsolidation ratio(OCR) is used to evaluate the strength and stress-strain behaviors of overconsolidated clays in the shearing process. The bounding stress ratio incorporating the effect of the yielding ratio is used to characterize the potential failure strength of the overconsolidated clays. The dilation stress ratio taking into account the effect of the yielding ratio is applied to describe the dilatancy behaviors of the overconsolidated clays. Comparisons between model predictions and test data show that the proposed model could well capture the strength and stress-strain behaviors of normally consolidated and overconsolidated clays.

关键词： overconsolidated clay overconsolidated ratio critical state theory yielding ratio peak state strength dilatancy

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