Behavior of FRP–concrete–steel double skin tubular members under lateral impact: Experimental study

In this paper, an experimental investigation on the impact performance of FRP–concrete–steel double skin tubular members is presented. Twenty-four tests were carried out to examine the failure modes and the time histories of the impact forces, lateral deformations and strains. The effects of the impact energy and number of FRP layers on the impact behavior of the double skin tubular members were discussed. The results show that FRP–concrete–steel double skin tubular members behave in a ductile manner; there is a long stabilized stage of impact forces and the residual deformation mainly results from the cracking of FRP and concrete, as well as the overall bending deformation. The confinement of the outer FRP layers in the hoop direction to the sandwiched concrete in the composite members is small during the whole impact process. However, increasing the number of the outer FRP layers is somewhat beneficial to improve the dynamic resistance ability. The effect of the impact energy on the dynamic response of the composite members is significant. The difference between the FRP–concrete–steel double skin tubular members, concrete filled double skin steel tubes and concrete filled steel tubes is discussed based on the test results in this paper.     

A comprehensive study of externally venting flames—Part I: Experimental plume characteristics for through-draft and no-through-draft ventilation conditions and repeatability

Externally venting flames have been examined during a series of eight full-scale flashover tests. Furniture was used in a burn room larger than a standard one. The purpose of the work has been to investigate the likelihood of external fire spread from a burn room window with standard glass when the external facade is non-combustible. The effects on externally venting flames of internal ventilation conditions and wind have been studied in detail. Secondary fires and glass breakage have been examined. Repeatable experimental data and reliable information on externally venting flames have been generated for numerical model validation and performance-based design code development. In Part I of this two-part paper, the emphasis is on the repeatability of the experimental data on externally venting flames. A new averaging method introduced previously has been used for this purpose. In Part II, extensive comparisons are given with available experimental data and empirical approximations from the literature. Surface fits to the experimental data are also presented for communication purposes.     

Impact of urban conditions on firm performance of migrant entrepreneurs: a comparative Dutch–US study

Recent studies on ethnic entrepreneurship have pointed at an increasing share of migrants in urban small- and medium-sized entrepreneurial businesses. These migrant activities are crucial to the urban economy in many countries, as they employ a significant part of the workforce. The main objective of our study is to identify success conditions of ethnic entrepreneurship by using concepts from social capital and human capital from the literature on empirical factors that are responsible for successful ethnic entrepreneurship. The empirical part of the paper is based on a survey questionnaire among migrant entrepreneurs in the city of Amsterdam in the Netherlands and in Fairfax, County in the state of Virginia in the US. We present an overview of cultural, ethno-psychological and motivational aspects that contribute to the understanding of similarities and differences between ethnic entrepreneurs in both locations. The analysis is structured around several dimensions of social and human capital including personal and business characteristics, and network participation for improving business performance. The findings of the two studies are compared to explore a possible correspondence in business performance patterns. The research tool used to assess performance is Data Envelopment Analysis (DEA), a technique for comparative efficiency analysis in various types of corporate organizations. Finally, concluding remarks are presented and possible extensions of the analysis are suggested.     

Fatigue performance and stiffness variation of stud connectors in steel–concrete–steel sandwich systems

In this study, a series of fatigue tests on six nominally identical push-shear specimens is conducted. The test specimens were subjected to an initial quasi-static test, up to a predefined maximum load, followed by a fatigue test to failure. For all the fatigue tests the mean applied load was the same while the load range varied to induce fatigue failure. The push-shear fatigue tests indicated that stiffness of the shear connections is gradually decreased during the test. Overall, the test results revealed that the lifetime of steel–concrete–steel sandwich systems under cycling loads could be predicted beforehand through the evaluation of the stiffness reduction in shear connections.     

Static behavior of ribbed folded plate roof under vertical uniform load—Experimental study and meshfree method analysis

Folded plate roofs are widely used in building roofs due to their light weight and high stiffness. However, traditional folded plate roofs are often limited in application due to insufficient stiffness under the current trend of pursuing larger-span roofs. Ribbed folded plate roofs can effectively solve this problem because ribs not only increase the stiffness of the roof and reduce stress concentration, but they are also easy to be formed into various shapes to meet different needs for buildings. Therefore, the detailed analysis was carried out on a reinforced concrete ribbed folded plate roof (RCRFR) under the vertical uniform load to investigate its static behavior. The bearing capacity, failure mode, load–displacement relationship, and strain variation were obtained through the test. Additionally, based on the finite element (FE) method, not only a comparison was conducted between RCRFR and reinforced concrete ribless folded plate roof (RCLFR), but the influence of material nonlinearity and geometric nonlinearity on the structure was also investigated. Moreover, the bending characteristics of RCRFR under design load were analyzed based on the reproducing kernel particle method. The experimental results showed that this structure had good mechanical properties within the design load. In the overload stage, the concrete on the underside of the structure was severely damaged. Furthermore, the yielding of the ribbed plate's reinforcing bars caused the increased vertical deformation difference between the ribbed plate and the top chord, and the ribbed plate and the central ridge beam. Eventually, the failure of the anchorage of the ribbed plate's reinforcing bars anchored in the central ridge beam and the top chord led to the loss of structural load-bearing capacity. The FE analysis results demonstrated that ribs enhance the stiffness of the structure, with material nonlinearity having the primary impact and geometric nonlinearity exerting a secondary effect. The meshfree method analysis was in concordance with the experimental results as well as those of the FE analysis.     

Perception of plant species richness by people with different nationalities—an experimental study

This study investigates with the help of a manipulative experiment how people with different nationalities perceive meadow-like arrays of different species richness (1, 8, 16, 32, 64 species). Participants (n = 187) were all residents of the canton of Zurich and originated from 43 different countries. Overall valuation of the meadow-like arrays increased with species richness. However, while participants from high-income countries (measured by GDP per capita) clearly liked species-rich meadows most and species-poor ones least, participants from low-income countries did not have such clear preferences. Preferences were not related to the length of time a participant had already spent in Switzerland (on average seven years), but to perceived familiarity with a meadow-like array. Sex and education did not influence valuations. Environmental expertise fostered participants’ dislike of species-poor arrays, as did age.     

Analytical and experimental study on flexural performance of WPC–FRP beams

Wood plastic composite (WPC) beams retrofitted with carbon and glass fiber-reinforced polymer (CFRP and GFRP) composites offer an attractive solution to enhance the behavior of wood in terms of strength and ductility, as well as altering the mode of rupture of such structural members. However, very little is known about their performance. Thus, this paper presents a theoretical model based on nonlinear WPC properties, to investigate the behavior of hybrid WPC–FRP beams. In order to calculate the bending moment, the model considers an exponential function in the stress–strain diagram of WPC in both tension and compression parallel to the fibers. A four-point bending test configuration was conducted as short-term experiments to determine the load–displacement relationships of WPC beams with CFRP and GFRP sheets adhered to the tensile side. In order to validate the employed approach, the results obtained from the theoretical model were compared with the experimental results where a satisfactory agreement was achieved.     

The effect of indoor environmental quality on occupants’ perception of performance: A case study of refurbished historic buildings in Malaysia

This paper presents an assessment of occupants’ opinion of the internal environment of buildings, based upon their responses to questions relating to a range of discrete factors. The survey considers many aspects of the internal environment and seeks to gain occupants responses to each of these in terms of “User Satisfaction” and “Degree of Importance”. The questionnaire utilised a seven-point bi-polar scale to score these responses against each of the factors. In addition, the questionnaire elicits a ‘fingerprint’ that combines up to 22 factors relating to satisfaction with the building. The study documents and considers aspects of the building environment for which the users noted that they were least satisfied as well as those that are considered by the occupants as being of most importance. It is critical that sustainable development results not just in resource conservation, but also in increasing productivity and occupant well-being within buildings. This study hopes to provide insight for the design community on the perceptions of occupants in relation to building performance based on indoor environmental quality (IEQ) criteria. It also seeks to add to the growing body of research on sustainable design and occupants’ perception of IEQ.     

Interface load–displacement behaviour of sand grains coated with clayey powder: Experimental and analytical studies

In the present study, the micromechanical behaviour at the interfaces of sand grains coated with kaolinite powder is examined. Two different classes of coated grains were produced, one with lighter coating and one with heavier coating. The interface micromechanical experiments were conducted on pairs of grains and the emphasis was placed on the normal and tangential load-displacement relationships and the inter-particle friction of the different pairs highlighting the differences between uncoated and coated grains and also between the different classes of coating. All the experiments were conducted using a micromechanical custom-built loading apparatus and for the analysis of the data, analytical models from the literature were used, where adequate modifications were applied in specific in the tangential direction to match with the experimental results. Iteration processes, image analyses and microscopic image observations were adopted in the study of the frictional behaviour of the grains as well as the study of the damage of the surfaces. Work done and rate of work done concepts were introduced and linked to the damage of the surfaces of the grains and the role of repeating the shearing tests following the same shearing paths were particularly emphasized. The results from the study can provide some useful insights into the grain-scale behaviour of soil grains as well as input parameters in DEM studies.     

Factors affecting the coprecipitation of inorganic phosphate with calcite in hardwaters—I Laboratory studies

Results are presented for the coprecipitation of inorganic phosphate on calcite and interpreted using a chemical model. The model is used to elucidate why three different chalk waters (two natural and one artificial) coprecipitated different surface densities of phosphorus under similar conditions. Inhibitors of calcite growth such as magnesium and iron have a substantial effect on the amount of phosphorus coprecipitated on calcite, whereas a humic acid material had very little effect. The complete inhibition of calcite growth by inorganic phosphate is also demonstrated.     

The moisture performance of framed structures—A mathematical model

A mathematical model is developed for the moisture performance of a framed structure (e.g., a flat roof or a wall), containing a hygroscopic framing material and a cavity filled with air or insulation. A formula is developed that connects the enclosed and unenclosed drying time constants for the framing material. The enclosed drying time constant alone describes the longer term moisture behaviour of the structure (much greater than one day) under any driving forces given the linearity assumptions used. The model allows for anisotropic framing materials with initial moisture contents above or below fibre saturation.     

The building volume with hygroscopic materials—an analytical study of a classical building physics problem

A global analytical solution covering all cases of a building volume with hygroscopic materials is given. The mathematical and physical simplifications and assumptions are quite modest. Isothermality is not assumed. Examples are rooms, attics, subfloor spaces and building cavities. All share the same physics describing the vapour pressure in the building volume and the moisture content in the hygroscopic materials as a function of building volume temperature and moisture emission rates, external vapour pressure and building volume ventilation levels, heat and mass transfer between the building volume and the hygroscopic materials, and heat and mass storage and transfer within the hygroscopic materials.     

Interactions of resin acids with aerobic and anaerobic biomass—I. Degradation by non-acclimated inocula

The fate and effects of resin acids in anaerobic and aerobic biological treatment systems were compared under batch reactor test conditions. With a non-acclimated anaerobic biomass inoculum, no degradation of resin acids was observed under anaerobic conditions after exposure times of up to 24 d. Inhibition of methanogenic activity of the anaerobic consortium was noted at initial resin acid/biomass ratios exceeding 0.0031 mg resin acids/mg VSS. Inhibited methanogenic populations were capable of acclimation to high concentrations of resin acids after 7–13 d of exposure. Under aerobic batch conditions with a non-acclimated activated sludge inoculum, high initial resin acid concentrations were reduced to detection limits in 2–3 d. The highest specific removal rate of 109 mg resin acids/g VSS · d measured in this study with non-acclimated aerobic biomass, was much higher than comparable values reported by others for acclimated aerobic biomass. The time required for removal appeared to be independent of the batch reactor biomass concentration. No evidence was found to suggest that high concentrations of resin acids resulted in inhibition under aerobic conditions.     

Anti-corrosion performance of bridge strands consisting of steel wires galvanised with zinc–aluminium alloy

Strands consisting of 19 parallel steel wires galvanised with zinc (Zn, 90%) and aluminium (Al, 10%) alloy were produced and accelerated corrosion tests were conducted, and the anti-corrosion performance was compared with the conventional strands galvanised with Zn. The strands were placed at a relative humidity (RH) of 60%, RH of 100% and the wet condition in the thermo-hygrostat at 40°C for 150 days. The mass loss due to corrosion of the strands galvanised with Zn–Al at an RH of 60% and 100% was small, and the strands had good corrosion resistance. The corroded mass of the strands at the wet condition was 15 times larger than that at RH of 100%. The strands galvanised with Zn–Al had lesser corrosion than those galvanised with Zn under the three environmental conditions. Corroded mass was larger in the surface wire, the inside wire and the centre wire in this order. The cross-sections of corroded strands were investigated by using a microscope and an electron probe micro-analyser showing that the corrosion product of Zn was porous and coarse. By contrast, the corrosion product of Zn–Al alloy was dense and hard to exfoliate from the steel layer. This difference made Zn–Al galvanised wire strands superior to Zn galvanised wire strands.     

Behavior of Steel–Concrete Partially Composite Beams Subjected to Fire—Part 1: Experimental Study

Partially composite steel–concrete beams are commonly used in building construction, and so the behavior of such beams in fire is an important problem. This paper presents the results of an experimental investigation on the response of two composite beam specimens subject to fire exposure. The two specimens were nominally identical, except for the shear connection ratio. Based on room temperature calculations, one specimen was designed as fully composite, and the second was designed as partially composite with a 50% shear connection ratio. The concrete slab for each specimen was constructed with a flat steel deck and reinforcement was provided by a reinforcing bar truss. Both specimens were subject to a constant vertical load applied at four locations along the span and tested in a furnace with an ISO-834 standard fire. Both specimens achieved large deflections associated with flexural yielding of the composite beams and exhibited measured flexural capacities larger than predicted from Eurocode 4. Based on test measurements, the shear connection ratio had a significant influence on interface slip and uplift behavior of concrete slabs. Failure of the specimens was defined when the maximum deflection reached span/30. The fire exposure time needed to reach this definition of failure was nearly the same for both specimens, and was 51 min for the fully composite beam and 49 min for the partially composite beam. A companion paper considers the degradation of material properties with temperature and slips behavior of shear connectors at elevated temperatures and also provides an analytical approach to predict fire response of steel–concrete partially composite beams.     

Long-term deflection of cracked composite beams with nonlinear partial shear interaction — A study using neural networks

A new study of the short- and long-term deflections of simply-supported composite beams using finite element analysis and artificial neural networks (ANNs) is presented. In this study, two ANN models are developed and trained using the results of a finite element model developed by the authors in a companion paper. The finite element model accounted for the nonlinear load–slip relationship of shear connectors as well as the creep, shrinkage, and cracking of concrete slabs. The effects of creep and shrinkage of the concrete slab are considered only for non-cracked concrete. A large database representing a wide range of different design parameters was constructed for the purpose of training and verifying the two ANN models. It was found that the two ANN models were capable of predicting deflections of composite beams not used as part of the training process. The ANN models were then used to evaluate the effects of non-geometric design variables on the short- and long-term deflections of simply-supported composite beams. Finally, the short- and long-term deflections computed based on the approaches given in the AISC specification and Eurocode 4 were assessed using the results of the finite element model. It was found that the AISC approach underestimates short-term deflections and overestimate long-term deflections when compared with the results of the finite element method.     

Erring with high‐level nuclear waste disposal: a case study of the precautionary principle

Increasingly, the “Precautionary Principle” is being discussed as a basis for decision‐making to protect environmental and human health where there are risks of serious or irreversible damage but where there are gaps in knowledge and uncertainties to demonstrate conclusively either the existence of the risks or their levels. Many analyses of the precautionary principle focus on the abstract or philosophical theories of the principle. Here, I provide a more practical case study to demonstrate some of the prospects and problems of the principle. While the case study focuses specifically on the disposal of high‐level radioactive waste at a potential repository at Yucca Mountain, Nevada, it also provides insight to other problems of complex technologies and the protection of health.     

Independent Reinforced Soil Structure with Pile Foundation—Piled Geo-Wall: An Experimental Study on the Application to Seismic Measure for Embankment—

Our aim in this study was to achieve an independent reinforced soil structure with pile foundation that can be applied to such structures as earth retaining walls and countermeasures against the collapse of embankments or rockfall impact built on narrow construction sites, such as on slopes. In order to confirm the effectiveness of the application of pile foundation to reinforced soil structures by geogrid for improvement of the lateral resistance of the structure and to investigate the interaction between pile and reinforced soil structure, a dynamic centrifuge model test (25 G) was carried out. Two geogrid reinforced soil, one with piles and one without, were used in a countermeasure to reduce the deformation of a road embankment built on a slope in the event of an earthquake, and the effectiveness of the pile foundation to the reinforced soil structure was considered with regard to it affected the road surface. The details and the results of the dynamic centrifuge model test, as well as the interaction between pile and reinforced soil structure are described, and the effectiveness of the application of pile foundation to reinforced soil structure is discussed in this paper.     

Detection of spacecraft fire signatures and post-fire aerosols—Part I: Ground-based results

Preventing fires in spacecraft and other remote platforms is an important facet of avoiding fires that potentially compromise missions, hardware, and crew. If a fire occurs, the objective is to detect the associated fire signatures at the earliest possible time from inception, thus minimizing propagation and collateral damage while providing maximal margin for suppression. The goal is to provide detection sensitivity without introducing spurious false alarms that compromise operations and trigger responsive abatement and containment provisions. A related issue in sealed, self-contained environments is post-fire clean up, and sensors to evaluate the environmental suitability in crewed quarters. In both situations, knowledge of the particulate and/or gaseous fire signatures as they occur under the unique combination of a reduced-gravity environment and materials typical of spaceflight applications is essential for the design of spacecraft fire detectors and habitat sensors. This paper describes recent ground and spaced-based data on fire signatures, and the response of a novel multi-channel optical scattering sensor. This detector, known as the Multi-Parameter Aerosol Scattering Sensor (MPASS), determines multiple moments of the aerosol distributions. The methodology for designing a sensor with the desired response function is discussed, as well as test results that demonstrate the performance of prototype devices.