基坑地下连续墙渗漏水事故原因和处理措施

从三个方面分析了地下连续墙漏水的原因,通过对地下连续墙漏水案例的论述,探讨了造成基坑事故的原因,提出了相应的处理措施,总结出地下连续墙渗漏水分析中得到的启示.     

Test description of steel X‐bracing system using low‐grade steel and internal oblique transverse stiffeners

A sample of steel X‐braced frame was studied using laboratory tests by which system behaviour and its failure modes were driven. The braces were designed based on the idea of using low‐grade steel in lateral load resisting system. Therefore, stocky braces were used. A rigid central core at intersection point of braces was considered. Oblique transverse stiffeners were provided inside the braces' cross‐section for more lateral stiffness and reduction of system yield displacement. Intervals between stiffeners were determined to create guided local buckling before global buckling of braces and thus dissipate energy by accordion behaviour. The hysteresis and energy absorption diagrams were presented. The system ductility has also been calculated. The obtained results represent uniform and stable energy absorption and reasonable system ductility by using low‐grade steel, rigid central core and oblique transverse stiffeners. Copyright © 2010 John Wiley & Sons, Ltd.     

Optimum design of post‐tensioned axially symmetric cylindrical walls using novel hybrid metaheuristic methods

An efficient methodology for various structural design problems is needed to optimize the total cost for structures. Although some methods seem to be efficient for applications, due to using special algorithm parameters, computational cost, and some other reasons, there is still much to be done in order to develop an effective method for general design applications. This paper describes the influence of the selected procedure on the design of cost‐optimized, post‐tensioned axially symmetric cylindrical reinforced concrete walls. In this study, the optimum design of axially symmetric cylindrical walls using several metaheuristic algorithms is investigated. The new generation algorithms used in the study are flower pollination algorithm, teaching–learning‐based optimization, and Jaya algorithm (JA). These algorithms are also compared with one of the previously developed algorithm called harmony search. The numerical examples were done for walls with 4‐ to 10‐m height and for 1, 5, 10, 15, 20, and 25 post‐tensioned load cases, respectively. Several independent runs are conducted, and in some of these runs, JA may trap to a local solution. To overcome this situation, hybrid algorithms such as JA using Lévy flights, JA using Lévy flights with probabilistic student phase (JALS), JA using Lévy Flights with consequent student phase (JALS2), and JA with probabilistic student phase are developed. It is seen that in many respects, the JALS2 and JALS are the most effective within the proposed hybrid approaches.     

Seismic behavior of T‐shaped steel reinforced concrete shear walls in tall buildings under cyclic loading

Shear walls are often used as the primary lateral load resisting elements in high‐rise buildings because of their large in‐plane stiffness and strength. It is a common practice to combine rectangular walls to form T‐shaped, I‐shaped and L‐shaped walls for functionality and esthetic reasons. Three relatively slender steel reinforced concrete (SRC) shear walls with T‐shaped cross‐sections were constructed and tested to failure under cyclic lateral loading. This research was conducted to assess the failure mechanism, hysteretic behavior, ductility and energy dissipating capacity of SRC T‐shaped walls under various axial load ratios. All the specimens exhibited a flexural mode characterized by crushing of the concrete and buckling of the steel at the free web boundary. The experimental results showed good hysteretic characteristics without pinching phenomena. The ductility coefficient varied from 2.3 to 4.1, and the deformation capability decreased with the increasing of axial load ratios. The stiffness, strength and ductility of T‐shaped walls are dependent upon the direction of the applied lateral loads. Higher stiffness and strength and lower ductility are achieved when the flange is in tension. The failure mechanism suggested that special attention should be paid to the design of the free web boundary to prevent premature failure under compression. Copyright © 2014 John Wiley & Sons, Ltd.     

Bacteria in a water‐damaged building: associations of actinomycetes and non‐tuberculous mycobacteria with respiratory health in occupants

We examined microbial correlates of health outcomes in building occupants with a sarcoidosis cluster and excess asthma. We offered employees a questionnaire and pulmonary function testing and collected floor dust and liquid/sludge from drain tubing traps of heat pumps that were analyzed for various microbial agents. Forty‐nine percent of participants reported any symptom reflecting possible granulomatous disease (shortness of breath on exertion, flu‐like achiness, or fever and chills) weekly in the last 4 weeks. In multivariate regressions, thermophilic actinomycetes (median = 529 CFU/m²) in dust were associated with FEV₁/FVC [coefficient = ?2.8 per interquartile range change, P = 0.02], percent predicted FEF_25–75% (coefficient = ?12.9, P = 0.01), and any granulomatous disease‐like symptom [odds ratio (OR) = 3.1, 95% confidence interval (CI) = 1.45?6.73]. Mycobacteria (median = 658 CFU/m²) were positively associated with asthma symptoms (OR = 1.5, 95% CI = 0.97?2.43). Composite score (median = 11.5) of total bacteria from heat pumps was negatively associated with asthma (0.8, 0.71?1.00) and positively associated with FEV₁/FVC (coefficient = 0.44, P = 0.095). Endotoxin (median score = 12.0) was negatively associated with two or more granulomatous disease‐like symptoms (OR = 0.8, 95% CI = 0.67?0.98) and asthma (0.8, 0.67?0.96). Fungi or (1→3)‐β‐D‐glucan in dust or heat pump traps was not associated with any health outcomes. Thermophilic actinomycetes and non‐tuberculous mycobacteria may have played a role in the occupants' respiratory outcomes in this water‐damaged building.     

Behavior of coupled shear walls with buckling‐restrained steel plates in high‐rise buildings under lateral actions

Traditional coupling beams in coupled shear walls (CSWs) may be lack of required ductility or inconvenient to be fully repaired or replaceable after earthquake damage. To improve the CSW seismic performance, a type of new structural system, which is referred to as coupled shear walls with buckling‐restrained steel plates (CSW–BRSP), is proposed and thoroughly studied. In the system, a pair of individual concrete wall is coupled through buckling‐restrained steel plates instead of traditional concrete coupling beams. Based on the continuous medium method (CMM), stiffness and strength design formulas are developed for the seismic design of this system. Intensive investigations have been conducted to assess the undesirable axial forces in the buckling‐restrained steel plates induced by lateral loads. In order to facilitate the application of this system, a detailed design procedure is also explicitly stated. Finally, an example of typical high‐rise building is presented to illustrate the design procedure as well as demonstrate the excellent seismic performance of the proposed system by means of nonlinear time‐history analysis. Copyright © 2015 John Wiley & Sons, Ltd.     

Microbial growth in building material samples and occupants’ health in severely moisture‐damaged homes

There is no commonly approved approach to detect and quantify the health‐relevant microbial exposure in moisture‐damaged buildings. In 39 single‐family homes with severe moisture damage, we studied whether concentrations of viable microbes in building material samples are associated with health among 71 adults and 68 children, and assessed with symptoms questionnaires, exhaled NO, and peak expiratory flow (PEF) variability. Symptoms were grouped into three scores: upper respiratory symptoms, lower respiratory symptoms, and general symptoms. The homes were divided into three groups based on viable counts of fungi, actinomycetes, and total bacteria cultivated from building material samples. Highest group of actinomycete counts was associated with more general symptoms, worse perceived health, and higher daily PEF variability (aOR 12.51; 1.10‐141.90 as compared to the lowest group) among adults, and with an increase in lower respiratory symptoms in children, but the confidence intervals were wide. We observed significant associations of fungal counts and total microbial score with worse perceived health in adults. No associations with exhaled NO were observed.     

Numerical study of isolation in the backfill zone of foundation pit method to reduce railway generated vibration in high‐rise buildings

The conventional methods to reduce building vibration include isolation of vibration sources, isolation of buildings, and setting trenches in the propagation path. However, it is evidenced that these methods are not feasible for high‐rise buildings in crowded urban areas. This paper proposes a new method to reduce vibration for high‐rise buildings by using the existing construction backfill zone, the isolation in the backfill zone of foundation pit (IBF). Numerical analyses were first carried out to obtain a realistic excitation time history, and a finite element–infinite element model was developed and calibrated using test data from an actual building site. The contributions of the basement sidewalls and foundation slabs to floor vibration and the influence of infill material properties are investigated. Lastly, a composite isolation layer was suggested to provide both sufficient restraining effects to the building foundation and satisfactory vibration isolation. The analyses confirmed that the proposed IBF method reduces ground‐borne vibration in high‐rise buildings by up to 66% when railway is on the ground.     

Prevalence and risk factors associated with nonspecific building‐related symptoms in office employees in Japan: relationships between work environment,Indoor Air Quality,and occupational stress

A nationwide cross‐sectional study of 3335 employees was conducted in 320 offices in Japan to estimate the prevalence of building‐related symptoms (BRSs) and determine the risk factors related to work environment, Indoor Air Quality, and occupational stress. Data were collected through self‐administered questionnaires. The prevalences of general symptoms, eye irritation, and upper respiratory symptoms were 14.4%, 12.1%, and 8.9%, respectively. Multiple logistic regression analyses revealed that eye irritation was significantly associated with carpeting [odds ratio (OR), 1.73; 95% confidence interval (CI), 1.24–2.41], coldness perception (OR, 1.28; 95% CI, 1.13–1.45), and air dryness perception (OR, 1.61; 95% CI, 1.42–1.82). General symptoms were significantly associated with unpleasant odors (OR, 1.37; 95% CI, 1.13–1.65), amount of work (OR, 1.24; 95% CI, 1.06–1.45), and interpersonal conflicts (OR, 1.44; 95% CI, 1.23–1.69). Upper respiratory symptoms were significantly associated with crowded workspaces (OR, 1.36; 95% CI, 1.13–1.63), air dryness perception (OR, 2.07; 95% CI, 1.79–2.38), and reported dustiness on the floor (OR, 1.39; 95% CI, 1.16–1.67). Although psychosocial support is important to reduce and control BRSs, maintaining appropriate air‐conditioning and a clean and uncrowded workspace is of equal importance.     

Load‐sharing ratio of prebored and precast pile in top‐down method construction process

The load‐sharing ratio of the prebored and precast pile in top‐down method foundation was investigated by using a numerical analysis and field case study. The emphasis was on quantifying the apparent load‐sharing ratio of the prebored and precast pile during the top‐down method construction process. A series of three‐dimensional finite element analysis were conducted, with special attention given to the pile load‐sharing ratio under various conditions, such as soil condition, pile geometry, pile length, and structure load. In addition, the load‐sharing ratio of a single pile was also investigated based on the location of the pile in the raft (footing). The analysis model was validated by comparing the analysis model with the field data of an actual construction site using the prebored and precast pile and the top‐down method. On the basis of the series of analysis results and the field measurements, when the soil condition is better than weathered rock and for moderate pile length, at least 15% of the total structure load was supported by the pile throughout the construction process. Furthermore, it was shown that the pile near the center of the raft carried more structure load compared with the piles in the side and the corner of the raft.     

The effects of building‐related factors on classroom relative humidity among North Carolina schools participating in the ‘Free to Breathe,Free to Teach’ study

Both high and low indoor relative humidity (RH) directly impact Indoor Air Quality (IAQ), an important school health concern. Prior school studies reported a high prevalence of mold, roaches, and water damage; however, few examined associations between modifiable classroom factors and RH, a quantitative indicator of dampness. We recorded RH longitudinally in 134 North Carolina classrooms (n = 9066 classroom‐days) to quantify the relationships between modifiable classroom factors and average daily RH below, within, or above levels recommended to improve school IAQ (30–50% or 30–60% RH). The odds of having high RH (>60%) were 5.8 [95% Confidence Interval (CI): 2.9, 11.3] times higher in classrooms with annual compared to quarterly heating, ventilating, and air‐conditioning (HVAC) system maintenance and 2.5 (95% CI: 1.5, 4.2) times higher in classrooms with HVAC economizers compared to those without economizers. Classrooms with direct‐expansion split systems compared to chilled water systems had 2.7 (95% CI: 1.7, 4.4) times higher odds of low RH (<30%). When unoccupied, classrooms with thermostat setbacks had 3.7 (95% CI: 1.7, 8.3) times the odds of high RH (>60%) of those without setbacks. This research suggests actionable decision points for school design and maintenance to prevent high or low classroom RH.     

Endotoxin,extracellular polysaccharides,and β(1‐3)‐glucan concentrations in dust and their determinants in four European birth cohorts: results from the HITEA project

Early‐life exposure to microbial agents may play a protective role in asthma and allergies development. Geographical differences in the prevalence of these diseases exist, but the differences in early‐life indoor microbial agent levels and their determinants have been hardly studied. We aimed to describe the early‐life levels of endotoxin, extracellular polysaccharides (EPS), and β(1‐3)‐glucans in living room dust of four geographically spread European birth cohorts (LISA in Germany, PIAMA in the Netherlands, INMA in Spain, and LUKAS2 in Finland) and to assess their determinants. A total of 1572 dust samples from living rooms of participants were analyzed for endotoxin, Penicillium/Aspergillus EPS, and β(1‐3)‐glucans. Information on potential determinants was obtained through questionnaires. Concentrations of endotoxin, EPS, and β(1‐3)‐glucans were different across cohorts. Concentrations of endotoxin and EPS were respectively lower and higher in INMA than in other cohorts, while glucans were higher in LUKAS2. Season of sampling, dog ownership, dampness, and the number of people living at home were significantly associated with concentrations of at least one microbial agent, with heterogeneity of effect estimates of the determinants across cohorts. In conclusion, both early‐life microbial exposure levels and exposure determinants differ across cohorts derived from diverse European countries.     

Deformation of compensated piled raft foundations with deep embedment in super‐tall buildings of Shanghai

This paper presents a synergetic approach based on a statistical‐empirical method, conservation of energy method and superstructure‐foundation interaction theory, and this paper aims to estimate the deformation level of a compensated piled raft foundation. The advantages and main characteristics of such a compensated piled raft foundation are described, and a history of the heave, recompression deformation and final settlement data measurements is provided. Case studies of four super‐tall buildings, the 88‐story Jinmao Building, 66‐story Henglong Plaza, 101‐story Shanghai World Financial Center and 121‐story Shanghai Center Tower in Shanghai, all of which are engineering projects that the second author participated in, are provided to illustrate the effectiveness of different calculations for heave, recompression deformation and final settlement. This study demonstrates that the deformation process can be reasonably projected for a piled raft foundation with deep embedment in Shanghai using superstructure‐foundation interaction methods, statistical‐empirical formulas and a method based on the conservation of energy. The coefficients in the statistical‐empirical method are also further optimized. This deformation estimation considering compensation for deep embedment unloading is reasonable and can be used to avoid excessively conservative designs, and the synergetic approach is applicable to any compensated piled raft foundation with deep embedment in Shanghai. Copyright © 2014 John Wiley & Sons, Ltd.     

Inflammatory potential in relation to the microbial content of settled dust samples collected from moisture‐damaged and reference schools: results of HITEA study

Aiming to identify factors causing the adverse health effects associated with moisture‐damaged indoor environments, we analyzed immunotoxicological potential of settled dust from moisture‐damaged and reference schools in relation to their microbiological composition. Mouse RAW264.7 macrophages were exposed to settled dust samples (n = 25) collected from moisture‐damaged and reference schools in Spain, the Netherlands, and Finland. After exposure, we analyzed production of inflammatory markers [nitric oxide (NO), tumor necrosis factor‐α (TNF‐)α, interleukin (IL)‐6, and macrophage inflammatory protein (MIP)2] as well as mitochondrial activity, viability, apoptosis, and cell cycle arrest. Furthermore, particle counts, concentration of selected microbial groups as well as chemical markers such as ergosterol, 3‐hydroxy fatty acids, muramic acid, endotoxins, and glucans were measured as markers of exposure. Dust from moisture‐damaged schools in Spain and the Netherlands induced stronger immunotoxicological responses compared to samples from reference schools; the responses to Finnish samples were generally lower with no difference between the schools. In multivariate analysis, IL‐6 and apoptosis responses were most strongly associated with moisture status of the school. The measured responses correlated with several microbial markers and numbers of particles, but the most important predictor of the immunotoxicological potential of settled dust was muramic acid concentration, a marker of Gram‐positive bacteria.     

Bacterial communities in commercial aircraft high‐efficiency particulate air (HEPA) filters assessed by PhyloChip analysis

Abstract  Air travel can rapidly transport infectious diseases globally. To facilitate the design of biosensors for infectious organisms in commercial aircraft, we characterized bacterial diversity in aircraft air. Samples from 61 aircraft high‐efficiency particulate air (HEPA) filters were analyzed with a custom microarray of 16S rRNA gene sequences (PhyloChip), representing bacterial lineages. A total of 606 subfamilies from 41 phyla were detected. The most abundant bacterial subfamilies included bacteria associated with humans, especially skin, gastrointestinal and respiratory tracts, and with water and soil habitats. Operational taxonomic units that contain important human pathogens as well as their close, more benign relatives were detected. When compared to 43 samples of urban outdoor air, aircraft samples differed in composition, with higher relative abundance of Firmicutes and Gammaproteobacteria lineages in aircraft samples, and higher relative abundance of Actinobacteria and Betaproteobacteria lineages in outdoor air samples. In addition, aircraft and outdoor air samples differed in the incidence of taxa containing human pathogens. Overall, these results demonstrate that HEPA filter samples can be used to deeply characterize bacterial diversity in aircraft air and suggest that the presence of close relatives of certain pathogens must be taken into account in probe design for aircraft biosensors.

Practical Implications

A biosensor that could be deployed in commercial aircraft would be required to function at an extremely low false alarm rate, making an understanding of microbial background important. This study reveals a diverse bacterial background present on aircraft, including bacteria closely related to pathogens of public health concern. Furthermore, this aircraft background is different from outdoor air, suggesting different probes may be needed to detect airborne contaminants to achieve minimal false alarm rates. This study also indicates that aircraft HEPA filters could be used with other molecular techniques to further characterize background bacteria and in investigations in the wake of a disease outbreak.