A city’s microclimate is greatly impacted by urbanization. The ratio of building height to street width affects the thermal properties of urban canyons. This characteristic is one of the main ...elements that control the thermal radiation emitted and how much solar radiation is absorbed, causing the urban air temperature to be much greater than in rural areas (urban heat island effect). The main aim of this study is to examine the thermal effect of the variations in the height of housing buildings on the urban layout and canyons in the hot arid climate of the UAE. The study used a qualitative method based on ENVI-met software and a case study of an existing housing project to investigate the current situation and the future thermal conditions of proposed configurations. The study investigated two groups of configurations with unified and diverse heights. The results of the study found that the best case among the first group of configurations with unified heights was U3, which had unified mass heights reaching 20 m height, the highest H/W ratio, and the lowest sky view factor; it recorded 0.5°C reduction in the 2:00 p.m. air temperature compared to the base case. The results also revealed that in the case of diverse heights, it is better to locate the highest masses in the hot wind direction. The D2, with highest masses of 20 m height that were located only on the north and west sides of the area blocking the hot north-west prevailing wind, recorded a reduction about 0.9°C compared to the base case. Moreover, in the cases with lower air temperature, U3 and D2 recorded the best predicted mean vote readings, especially in the daytime, when the air temperature is highest.
Nielsen–Lohse bridges are tied arch bridges with inclined cables that cross each other and connect through intersection clamps. Estimating the tension acting on the cables is essential for ...maintenance. Currently, methods for estimating the tension of a single cable using natural frequencies are applied to each cable after removing the intersection clamps. However, the removal and re-installation of intersection clamps is time-consuming and laborious. To improve the efficiency of tension estimation, the authors previously proposed a method for simultaneously estimating the tension of two cables with an attached intersection clamp. However, the previous method has the drawback of considering simple support at both ends, even though the actual boundary is not a perfect simple support. The objective of this study is to develop a new method for estimating the tension of two cables with unknown boundary conditions. The cable is assumed to be supported by a rotational spring at both ends. The newly proposed method estimates the tension, bending stiffness, and rotational stiffness of two cables from the natural frequencies without requiring the removal of the intersection clamp. The proposed method can handle arbitrary boundary conditions such as simple support or fixed support. In the case of fixed support, the rotational spring constant becomes infinity. To avoid infinity in the computation, normalization was employed in the derivation of the estimation formula. The validity of the proposed method was verified by numerical simulations and field experiments on an actual Nielsen–Lohse bridge. In the field experiment, the tension of all eight cables was accurately estimated and the estimation error was less than 10%. Even when accelerometers were installed on only one of the two cables at a height near the girder, the tension of both cables was estimated with good accuracy. The proposed method improves the efficiency of tension estimation work, because the tension of two cables can be estimated simultaneously and with good accuracy by measuring the acceleration of only one cable at a height near the girder.
Soil is a naturally heterogeneous material and can show significant spatial variation in strength and other properties. For silty and clayey soils, these variations are often more pronounced. Despite ...such variation, many past studies considered these soils as homogeneous and only considered a single set of soil parameters. This may lead to underestimation of the failure potential of geo-structure such as natural slopes, water retaining dams, retaining walls,
etc.
A finite element method considering soil variability should be an ideal tool to investigate the behaviour of these soils. This study adopted a 2D random finite element method to evaluate the effect of such variability on slope stability. The spatial variability was implemented by using the coefficient of variation (
COV
) and the spatial correlation length (
θ
) for cohesion. It was found that the soil slope with higher
COV
would have a higher chance of failure, whereas the soil slope with less
COV
might not show any failure. In addition, the soil with a higher
θ
, in general, show less potential of failure. In the literature, most studies considered an isotropic condition for the soil, i.e.,
θ
in
x
and
y
directions are the same
θ
x
=
θ
y
, which is not realistic. Therefore, the soil anisotropy (i.e.,
θ
x
≠
θ
y
) was considered carefully in this study. It was found that the probability of failure for anisotropic soil might be significantly higher than the isotropic soil.
The development of the theories of undamageable materials and bimodal self-regenerating materials leads directly to four-dimensional materials. Both are types of sought after materials. The authors ...have established that undamageable materials are the limit of Voyiadjis-Kattan materials of order n as n approaches infinity. Similarly, the authors established also that so called bimodal materials are the limit of self-regenerating materials of order n as n approaches infinity. In this work, a solid link is established between these theories that were developed recently and the new four-dimensional materials to come. It is concluded that both undamageable materials and bimodal materials are prime examples of four-dimensional materials. The conclusion is based on sound mathematical and mechanical principles.
Bangladesh—located in south Asia and home to almost 167 M people, is one of the most densely populated countries in the world. Despite high population density, the country is yet to have a ...well-coordinated mass transit system. However, most people rely on public transportation due to comparatively low motorization. Public transport users, especially vulnerable cohorts (e.g., women), face enormous challenges, including molestations, assaults, and rape during their daily commute. Few studies that analyzed the state of harassment exclusively focused on women, which might not be comprehensive enough to understand the state of the problem and devise effective policies. Therefore, the current study explores the state of harassment in the three cities of Bangladesh, namely, Dhaka—the capital; Rajshahi; and Mymensingh across all genders. The study also investigates people’s perception of women’s mobility, the experience of using public transport, and the desirable safety precautions to understand the gender differences and the variability across the three cities. A detailed questionnaire survey was conducted to collect data from the three cities. The study found considerable gender differences regarding the perception of women’s mobility hindrances, the experience of using public transportation, and desirable safety precautions. The differences across the three cities were also noticeable. Contrary to the general belief, the study found that people from smaller towns like Mymensingh were more likely to get harassed than those from the bigger cities like Dhaka and Rajshahi—insinuating the lack of reporting from the smaller towns of the country. The findings from the study could be helpful for the transit and city planners in creating a conducive transit ambiance in Bangladesh. Based on the desirable safety precautions, female-only rides, especially at night, would be beneficial. City planners could also plan small and medium business activities around transit stops to attract the crowd and reduce the possibility of getting harassed while walking alone to access transit.
Replacing ordinary Portland cement-based materials with alkali-activated industrial wastes is often limited because of significant volume changes occurring in these materials at early age. This ...experimental study aims to quantify the extent of the volume changes and explore the underlying mechanisms of pastes composed of slag and fly ash (ratio 50:50) which are activated by sodium hydroxide and sodium silicate. Eight compositions were tested, with silica modulus (M
s
) varying between 1.04 and 1.58 and with solution-to-binder ratios (S/B) varying between 0.47 and 0.70. Specimen length changes in sealed conditions are monitored by applying repeated thermal variations in an adapted AutoShrink device and are accompanied by isothermal calorimetry, uniaxial compressive strength, and internal relative humidity (IRH) tests. This way, the temporal evolutions of autogenous strains, the coefficient of thermal expansion (CTE), the heat release, the apparent activation energy (E
a
), the IRH and the strength are determined and compared to each other. Both the measured autogenous shrinkage and CTEs are rather large; they amount to 4,000–5,000 μm/m and roughly 40 μm/m/°C, respectively, at material ages of 2 weeks. An increase in S/B leads to a decrease in autogenous shrinkage and an increase in CTE. An increase in the M
s
causes a decrease in both the autogenous shrinkage and the CTE. Most strikingly, autogenous shrinkage evolves linearly with the cumulative heat released by the binders. The IRH remains continuously above 94% during the first 2 weeks. The apparent activation energy amounts to roughly 74 kJ/mol and is virtually unaffected by S/B and M
s
.
The Natural Hazards Engineering Research Infrastructure (NHERI) experimental facility at the University of Florida provides a diverse suite of experimental resources to support wind hazard research. ...The 40-m long Boundary Layer Wind Tunnel (BLWT) simulates boundary layer flows to characterize wind loading on rigid structural models and assess the response of aeroelastic structures. The use of experimental automation tools provides researchers unparalleled flexibility in their test configurations while supporting high throughput testing and data collection. The Terraformer, an array of 1116 roughness elements, can be rapidly reconfigured to generate terrain conditions in less than 90 s, the test section turntable can move automatically through a range of wind approach angles, and the instrumentation gantry can traverse preset paths to collect wind field measurements anywhere in the tunnel cross-section. These test automation tools, along with mechatronic structural models and real-time data transfer and processing, provide new opportunities in experimental wind tunnel testing. Recent cyber-physical wind tunnel testing projects highlight the benefits of these experimental automation tools. This paper will also discuss the most recent addition to the BLWT, the Flow Field Modulator (FFM). It consists of a 2D array of 319 individually controlled ducted fans driven by electronic speed controllers. The FFM expands the BLWT capabilities by supporting the simulation of non-monotonic profiles and non-stationary events such as gust fronts and downbursts, where mean velocity and turbulence distributions change over short spatial scales. The ability to simulate these flow conditions in a wind tunnel enables the investigation of a wide range of damaging conditions and the solutions for mitigating their impact on structures.
This study focuses on multi-hazard analysis for bridges, following a two-tier approach. First, it identifies relevant open issues and recent literature developments in the field, presenting data in a ...meaningful manner, with specific focus on the issues related with the analysis of hazard chain scenario treated as low probability–high consequence events. Second, it describes a practically useful and sufficiently generic approach for efficient computational investigation of hazard chain scenarios in highway bridges. Following that, the applicability of the approach is exemplified in an appealing and commonly encountered in real-life hazard chain scenario, in which a multilevel modeling strategy is adopted to assess the structural response under hazard chain scenarios of a highway viaduct. Among the considered scenarios is the impact of a heavy vehicle (tank truck) on the bridge pier, and the fire spread following the collision due to the presence of inflammable materials. The bridge structure is a typical 189-m-long multi-span composite highway viaduct. The impact is modeled with a non-linear transient dynamic analysis that accounts the inertial effect of the global structure, while the fire modeling is performed with non-linear quasi static dynamic analysis focusing on local behavior with a substructured model. Then different impact and fire scenarios are considered, including different impact velocities of the truck.
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