A homeowner reported extensive settlement damage approximately two weeks after the groundwater in the vicinity of the home was lowered at a nearby construction project. The infrastructure improvement project consisted...A homeowner reported extensive settlement damage approximately two weeks after the groundwater in the vicinity of the home was lowered at a nearby construction project. The infrastructure improvement project consisted of installing a 27-inch-diameter sanitary sewer main with an invert elevation about 19 ft below existing grade. Groundwater was lowered 12 ft during construction, down to a depth of 23 ft below existing grade. This paper addresses the following key questions regarding settlement and potential structural damage as a result of a temporary drop in groundwater caused by construction dewatering： （1） How could a decrease in groundwater elevation cause settlement？ （2） Is this a highly unusual or atypical phenomenon that cannot be explained or estimated using science and engineering techniques available to the engineering profession？ （3） Based on the standard of care at the time, should these problems have been anticipated, or at least examined, by the engineering firms engaged on this project？ Answers to these questions are addressed herein using results from geotechnical analyses and data obtained from laboratory and in-situ tests.展开更多
This paper, based on Deming＇s quality management （QM） theory embodied in ISO 9001, uses structural equation modelling （SEM） in a construction management research. Based on 100 usable responses collected from a na...This paper, based on Deming＇s quality management （QM） theory embodied in ISO 9001, uses structural equation modelling （SEM） in a construction management research. Based on 100 usable responses collected from a nationwide survey carried out from 14th February to 30th May 2008 on all key players in the Malaysian construction value chain, this paper aims to： （a） validate the dimensions of registration efforts to obtain and maintain ISO 9001 certifications; （b） validate the eight QM principles in ISO 9001 for quality management system （QMS） practices; （c） determine the components of organisational improvements experienced as a result of ISO 9001 certifications in terms of company competitiveness, customer satisfaction, and business performance; and （d） investigate the causal relationships among registration efforts, QMS practices, company competitiveness, customer satisfaction, business performance of ISO 9001-certified companies. The knowledge gained from the application of SEM is an important contribution to the body of theoretical literature in QM.展开更多
Spur dykes are the structures which are used to protect the eroding bank of rivers.They are sometimes also used to safeguard the life of many structures such as bridge piers,abutments etc.The efficiency of spur ...Spur dykes are the structures which are used to protect the eroding bank of rivers.They are sometimes also used to safeguard the life of many structures such as bridge piers,abutments etc.The efficiency of spur dykes has been checked in straight channels by conducting model tests in laboratories by many investigators.Very few studies were done in curved channels.In present work an attempt has been made to study the effect of location of spur dyke on bed and scour around bridge pier in curved open channel(bend angle=80o)with time.Experiment has been carried out in 80o channel bend at constant discharge(3.5×10^(-3) m^(3)/s)and bridge pier is located at angular displacementϴ=60o.Hereϴis the angle the line drawn at the inlet of any bend to the line joining the centre of curvature and any point on the outer portion of the bend.It is found that maximum scouring occurs atϴ=0o and 20oalong inner wall and atϴ=60o and 80o along outer wall.It is also found that scouring around bridge pier is more in the vicinity of pier and decreases with increase in distance from pier.The most suitable location for spur dyke to protect bridge pier is at angular displacementϴ=20o.Scour developed rapidly during initial time and then rate of scouring decreases with elapse of time.展开更多
Local scour is the reduction of original bed level around any hydraulic structure.Bridge failure due to scouring has made researchers study the cause of scouring and predict the scour depth and pattern around bridge p...Local scour is the reduction of original bed level around any hydraulic structure.Bridge failure due to scouring has made researchers study the cause of scouring and predict the scour depth and pattern around bridge piers and foundations.Several investigators have extensively studied local scour around isolated bridge pier,but modern designs of the bridges comprise of wide span and thus group of piers rather than a single pier.The flow and scour pattern around group of piers are different from the case of a single pier due to the interaction effect.The objective of present study is to investigate the effect of mutual interference of bridge piers on local scour experimentally around two piers in non-cohesive bed.Experiments were carried out on model bridge piers of circular cross section in a meandering channel.It was observed that when front and rear piers were placed at an angular displacement ofθ=40°and 80°respectively,maximum depth of scour is maximum.Hereθis the angle the line drawn at the inlet of bend to the line joining the centre of curvature and any point on the outer portion of the bend.展开更多
A number of three-point bending and fracture tests of 200 MPa-level reactive powder concrete (RPC) with the various fiber contents have been conducted to probe the nature and characteristics of toughness of RPC200. Th...A number of three-point bending and fracture tests of 200 MPa-level reactive powder concrete (RPC) with the various fiber contents have been conducted to probe the nature and characteristics of toughness of RPC200. The contribution of the embedded fibers to improving the crack-resistant capacity, energy absorption capacity and toughness with various deformation mechanisms has been analyzed. Taking account of that the first-crack deformation, peak-load deformation and their improvement varied with the fiber contents and that the deformation mechanism affected differently the performance at the first crack and the peak load, we took the peak-load deformation of plain RPC200 as the reference deformation to measure the toughness of fibered RPC200. Two toughness indices T <SUB>2(n−1)</SUB>(n) and FT <SUB>2(n−1)</SUB>(n) have been formulated based on P-δ responses and P-CMOD responses. The indices quantify the toughness of RPC200 with the various deformation mechanisms relative to perfectly elastoplastic materials by setting the toughness level 2(n−1) as the initial reference. It is shown that the toughness index T <SUB>2(n−1)</SUB>(n) reflects the function of fibers to improve the toughness of RPC with the deformation throughout specimens, but overestimates the contribution to enhancing the toughness in post-peak periods. It underestimates, on other hands, the contribution to improving the toughness in the period from the first crack to the peak load. In contrast, the toughness index FT <SUB>2(n−1)</SUB>(n) properly presents the capability that fibers absorb energy and constrain crack propagation in the matrix when the deformation is concentrated on the open crack. The proposed index unveils the contribution of fibers to toughening RPC200 both in the period from the first-crack to the peak load and in the period of post peak. This characterization method not only reveals the nature of toughness but also levels the toughness of RPC200. It could provide a way to establish an objective toughness characterization for RPC200 and facilitate its applications.展开更多
Summary What is already known on this topic?Vibrio parahaemolyticus(V.parahaemolyticus)is frequently resistant to common antimicrobials such as ampicillin and generally highly susceptible to most clinically used antim...Summary What is already known on this topic?Vibrio parahaemolyticus(V.parahaemolyticus)is frequently resistant to common antimicrobials such as ampicillin and generally highly susceptible to most clinically used antimicrobials.What is added by this report?V.parahaemolyticus were highly resistant to cefazolin and ampicillin:94.4% and 37.0%,respectively.展开更多
INTRODUCTIONGreen building design can be a complex process, and windows are an important part of that process. A wide rangeof performance parameters can make selecting the right options diffi cult, and some parameters...INTRODUCTIONGreen building design can be a complex process, and windows are an important part of that process. A wide rangeof performance parameters can make selecting the right options diffi cult, and some parameters provide confl ictingperformance trade-offs. Good information about how to design green windows is not readily available, as most peoplelook through windows, but not many people look at them. Designed correctly, windows can greatly enhance the occupants’enjoyment of the space and enhance the energy performance of the entire building. Designed incorrectly,windows can be a source of irreparable failing of the building to meet the occupants’ requirements for comfort, energyeffi ciency, and long-term durability of the building envelope.This article discusses the physics behind window performance, describes some of the design parameters, and explainshow to determine whether you can get the performance you want on site. This is not meant to be an exhaustivereference on the subject, as that would require several books. Rather, the intent is to provide an overview of thephysical behavior of window components, so that appropriate design choices are based on sound knowledge and notguesswork. This article also provides some fl uency with window-performance terminology for use in discussing designoptions with specialists.展开更多
INTRODUCTION Passive ventilation employs a set of strategies,potentially including building shape,internal confi guration,orientation,aperture size and position,and microclimate design,to direct air through a building...INTRODUCTION Passive ventilation employs a set of strategies,potentially including building shape,internal confi guration,orientation,aperture size and position,and microclimate design,to direct air through a building without the assistance of fans or pumps.Passive ventilation has received widespread attention in green building design,particularly in mild climates,because of its great potential to reduce cooling costs.The challenge of predicting airfl ow speed and direction within a building has encouraged development of sophisticated computational simulation tools,and the resulting confi dence has,in turn,led to the design of passive and passive/mechanical hybrid ventilation systems in increasingly extreme climates.The Harm A.Weber Academic Center possesses one of the most ambitious hybrid ventilation systems in the world:in the hot continental climate of the midwestern United States,this building integrates passive and mechanical systems into a single network of airfl ow pathways.Aperture openings for the system are controlled automatically,using information provided by numerous internal and external sensors,such that the building can make use of multiple hybrid modes to utilize the cooling power of outdoor air to the greatest extent possible.During August 2007,shortly after the peak of the local cooling season,when the building was expected to be under mechanical control,this investigation of the airfl ow and thermal properties of the new building was undertaken to provide useful information about its early performance.展开更多
文摘A homeowner reported extensive settlement damage approximately two weeks after the groundwater in the vicinity of the home was lowered at a nearby construction project. The infrastructure improvement project consisted of installing a 27-inch-diameter sanitary sewer main with an invert elevation about 19 ft below existing grade. Groundwater was lowered 12 ft during construction, down to a depth of 23 ft below existing grade. This paper addresses the following key questions regarding settlement and potential structural damage as a result of a temporary drop in groundwater caused by construction dewatering： （1） How could a decrease in groundwater elevation cause settlement？ （2） Is this a highly unusual or atypical phenomenon that cannot be explained or estimated using science and engineering techniques available to the engineering profession？ （3） Based on the standard of care at the time, should these problems have been anticipated, or at least examined, by the engineering firms engaged on this project？ Answers to these questions are addressed herein using results from geotechnical analyses and data obtained from laboratory and in-situ tests.
文摘This paper, based on Deming＇s quality management （QM） theory embodied in ISO 9001, uses structural equation modelling （SEM） in a construction management research. Based on 100 usable responses collected from a nationwide survey carried out from 14th February to 30th May 2008 on all key players in the Malaysian construction value chain, this paper aims to： （a） validate the dimensions of registration efforts to obtain and maintain ISO 9001 certifications; （b） validate the eight QM principles in ISO 9001 for quality management system （QMS） practices; （c） determine the components of organisational improvements experienced as a result of ISO 9001 certifications in terms of company competitiveness, customer satisfaction, and business performance; and （d） investigate the causal relationships among registration efforts, QMS practices, company competitiveness, customer satisfaction, business performance of ISO 9001-certified companies. The knowledge gained from the application of SEM is an important contribution to the body of theoretical literature in QM.
文摘Spur dykes are the structures which are used to protect the eroding bank of rivers.They are sometimes also used to safeguard the life of many structures such as bridge piers,abutments etc.The efficiency of spur dykes has been checked in straight channels by conducting model tests in laboratories by many investigators.Very few studies were done in curved channels.In present work an attempt has been made to study the effect of location of spur dyke on bed and scour around bridge pier in curved open channel(bend angle=80o)with time.Experiment has been carried out in 80o channel bend at constant discharge(3.5×10^(-3) m^(3)/s)and bridge pier is located at angular displacementϴ=60o.Hereϴis the angle the line drawn at the inlet of any bend to the line joining the centre of curvature and any point on the outer portion of the bend.It is found that maximum scouring occurs atϴ=0o and 20oalong inner wall and atϴ=60o and 80o along outer wall.It is also found that scouring around bridge pier is more in the vicinity of pier and decreases with increase in distance from pier.The most suitable location for spur dyke to protect bridge pier is at angular displacementϴ=20o.Scour developed rapidly during initial time and then rate of scouring decreases with elapse of time.
文摘Local scour is the reduction of original bed level around any hydraulic structure.Bridge failure due to scouring has made researchers study the cause of scouring and predict the scour depth and pattern around bridge piers and foundations.Several investigators have extensively studied local scour around isolated bridge pier,but modern designs of the bridges comprise of wide span and thus group of piers rather than a single pier.The flow and scour pattern around group of piers are different from the case of a single pier due to the interaction effect.The objective of present study is to investigate the effect of mutual interference of bridge piers on local scour experimentally around two piers in non-cohesive bed.Experiments were carried out on model bridge piers of circular cross section in a meandering channel.It was observed that when front and rear piers were placed at an angular displacement ofθ=40°and 80°respectively,maximum depth of scour is maximum.Hereθis the angle the line drawn at the inlet of bend to the line joining the centre of curvature and any point on the outer portion of the bend.
基金Supported by the New Century Excellent Talents Program (Grant No. NCET-05-0215)the Natural Science and Engineering Research Council of Canada (Grant No. PGS D2 2006)+1 种基金the Laboratory Innovation Plan of Beijing Science and Education Committee (Grant No. JD102900671)the National Basic Research Project of China ("973" Project) (Grant No. 2002CB412705)
文摘A number of three-point bending and fracture tests of 200 MPa-level reactive powder concrete (RPC) with the various fiber contents have been conducted to probe the nature and characteristics of toughness of RPC200. The contribution of the embedded fibers to improving the crack-resistant capacity, energy absorption capacity and toughness with various deformation mechanisms has been analyzed. Taking account of that the first-crack deformation, peak-load deformation and their improvement varied with the fiber contents and that the deformation mechanism affected differently the performance at the first crack and the peak load, we took the peak-load deformation of plain RPC200 as the reference deformation to measure the toughness of fibered RPC200. Two toughness indices T <SUB>2(n−1)</SUB>(n) and FT <SUB>2(n−1)</SUB>(n) have been formulated based on P-δ responses and P-CMOD responses. The indices quantify the toughness of RPC200 with the various deformation mechanisms relative to perfectly elastoplastic materials by setting the toughness level 2(n−1) as the initial reference. It is shown that the toughness index T <SUB>2(n−1)</SUB>(n) reflects the function of fibers to improve the toughness of RPC with the deformation throughout specimens, but overestimates the contribution to enhancing the toughness in post-peak periods. It underestimates, on other hands, the contribution to improving the toughness in the period from the first crack to the peak load. In contrast, the toughness index FT <SUB>2(n−1)</SUB>(n) properly presents the capability that fibers absorb energy and constrain crack propagation in the matrix when the deformation is concentrated on the open crack. The proposed index unveils the contribution of fibers to toughening RPC200 both in the period from the first-crack to the peak load and in the period of post peak. This characterization method not only reveals the nature of toughness but also levels the toughness of RPC200. It could provide a way to establish an objective toughness characterization for RPC200 and facilitate its applications.
基金supported by the National Science and Technology Major Project of China(Grant agreement 2018ZX10733402).
文摘Summary What is already known on this topic?Vibrio parahaemolyticus(V.parahaemolyticus)is frequently resistant to common antimicrobials such as ampicillin and generally highly susceptible to most clinically used antimicrobials.What is added by this report?V.parahaemolyticus were highly resistant to cefazolin and ampicillin:94.4% and 37.0%,respectively.
文摘INTRODUCTIONGreen building design can be a complex process, and windows are an important part of that process. A wide rangeof performance parameters can make selecting the right options diffi cult, and some parameters provide confl ictingperformance trade-offs. Good information about how to design green windows is not readily available, as most peoplelook through windows, but not many people look at them. Designed correctly, windows can greatly enhance the occupants’enjoyment of the space and enhance the energy performance of the entire building. Designed incorrectly,windows can be a source of irreparable failing of the building to meet the occupants’ requirements for comfort, energyeffi ciency, and long-term durability of the building envelope.This article discusses the physics behind window performance, describes some of the design parameters, and explainshow to determine whether you can get the performance you want on site. This is not meant to be an exhaustivereference on the subject, as that would require several books. Rather, the intent is to provide an overview of thephysical behavior of window components, so that appropriate design choices are based on sound knowledge and notguesswork. This article also provides some fl uency with window-performance terminology for use in discussing designoptions with specialists.
文摘INTRODUCTION Passive ventilation employs a set of strategies,potentially including building shape,internal confi guration,orientation,aperture size and position,and microclimate design,to direct air through a building without the assistance of fans or pumps.Passive ventilation has received widespread attention in green building design,particularly in mild climates,because of its great potential to reduce cooling costs.The challenge of predicting airfl ow speed and direction within a building has encouraged development of sophisticated computational simulation tools,and the resulting confi dence has,in turn,led to the design of passive and passive/mechanical hybrid ventilation systems in increasingly extreme climates.The Harm A.Weber Academic Center possesses one of the most ambitious hybrid ventilation systems in the world:in the hot continental climate of the midwestern United States,this building integrates passive and mechanical systems into a single network of airfl ow pathways.Aperture openings for the system are controlled automatically,using information provided by numerous internal and external sensors,such that the building can make use of multiple hybrid modes to utilize the cooling power of outdoor air to the greatest extent possible.During August 2007,shortly after the peak of the local cooling season,when the building was expected to be under mechanical control,this investigation of the airfl ow and thermal properties of the new building was undertaken to provide useful information about its early performance.
