Extraordinary Loads Research Articles

Vision-based survey method for extraordinary loads on buildings

The statistical modeling of extraordinary loads on buildings has been stagnant for decades due to the laborious and error-prone nature of existing survey methods, such as questionnaires and verbal inquiries. This study proposes a new vision-based survey method for collecting extraordinary load data by automatically analyzing surveillance videos. For this purpose, a crowd head tracking framework is developed that integrates crowd head detection and reidentification models based on convolutional neural networks to obtain head trajectories of the crowd in the survey area. The crowd head trajectories are then analyzed to extract crowd quantity and velocities, which are the essential factors for extraordinary loads. For survey areas with frequent crowd movements during temporary events, the equivalent dynamic load factor can be further estimated using crowd velocity to consider dynamic effects. A crowd quantity investigation experiment and a crowd walking experiment are conducted to validate the proposed survey method. The experimental results prove that the proposed survey method is effective and accurate in collecting load data and reasonable in considering dynamic effects during extraordinary events. The proposed survey method is easy to deploy and has the potential to collect substantial and reliable extraordinary load data for determining design load on buildings.

Global sensitivity analysis of the maximum live load and its applications

The design live loads are determined by the probability distribution of the maximum live load, which is influenced by the amplitudes and time intervals of various sustained and extraordinary loads. If the relative impact of different input variables on the maximum can be clarified, more targeted load surveys and modeling can be achieved. However, there is currently no global sensitivity analysis that simultaneously considers all input variables. In this study, the probability density function of the maximum live load is determined using the load coincidence principle and probability density evolution method. The relative entropy is employed as a measure for conducting a global sensitivity analysis across five common building occupancy types. The results indicate a significant imbalance in the impact of different input variables. The load amplitudes have a much greater effect than the time intervals. Among various load amplitudes, those related to the extraordinary loads often have the most significant impact. Regarding the time intervals, the occurrence intervals corresponding to the extraordinary loads caused by furniture stacking and normal crowding consistently have the least influence. For the time intervals with minimal impact, it is suggested to treat them as deterministic values in the live load modeling. This treatment has a negligible impact (not exceeding 10%) on the mean and upper fractile of the maximum, which are generally used for design in load codes.

Risk Assessment of Mamak Dam Based on The ICOLD Modification Method and Risk Index Method

The Mamak Dam has the risk of damage and the need for evacuation at an extreme downstream level. Risk considerations are based on the potential natural disasters of the dam, the impact of dam failure, design loads, and safety coefficients. The Risk Index method results in a score with parameters such as spillway capacity adequacy, safety factor adequacy against slopes, disaster factor (hazard), and all parameters analyzed to determine the Dam Safety Index (Idam). The drawback of the Risk Index method is neglecting downstream failure analysis. The ICOLD modification method for parameters is the same as the Risk Index method, but the ICOLD method considers downstream analysis. The modification involves adding parameters, such as the condition of the dam slope cover layer, based on the Mamak Dam Large Inspection results. In the Risk Index method, the Idam calculation value is 262.5. The total risk index value for Mamak Dam is 51.73, with a dam safety value of 92.337. In the ICOLD method, the Idam calculation value is 245, with a total risk index value for Mamak Dam of 48.28 and a Dam Safety value of 92.848. Meanwhile, using the Modified ICOLD method, the Idam calculation value is 245, with a total risk index value for Mamak Dam of 49.93 and a Dam Safety value of 92.603. Based on these results, the Dam Safety value with the Modified ICOLD method has decreased but still falls within the satisfactory classification (>75). Therefore, it can be concluded that Mamak Dam is currently at a safe level against normal loads and extraordinary loads (design floods and design earthquakes).

Numerical algorithm for determining serviceability live loads and its applications

The live load duration refers to the period when the live load is larger than a given threshold in the reference period. The smallest threshold that allows the duration to be shorter than the required length is employed as the design live load for serviceability limit states. However, the traditional method only considers the mean duration and the probability that the duration exceeds the required length is unknown. This study proposes a new algorithm to determine the probability distributions of the live load duration. A sustained or extraordinary load process is transformed into a random variable set based on the stochastic harmonic functions. Subsequently, the duration distributions can be derived by employing the load coincidence principle and probability density evolution method. Three numerical examples including one sustained load and multiple extraordinary loads are provided and the results of the proposed algorithm are compared with those of Monte Carlo simulation. The proposed algorithm allows the exact determination of design live loads based on a predefined exceeding probability. As an application, the quasi-permanent and frequent values of seven user categories are calculated when the exceeding probabilities are taken as 10%, 5% and 2%, respectively. It is found that the quasi-permanent values can increase with increasing area and the differences between the frequent and quasi-permanent values can be more than 20 times.

Nonlinear gain models in a quantum cascade laser.

Density matrix analysis of a three-state model of quantum cascade laser (QCL) reveals that in this device, the optical gain is composed of the linear part (proportional to population inversion Δn) and the remaining nonlinear part. The nonlinear component non-negligibly contributes even to the small-signal response of the medium. In many attempts to modeling QCLs, the common practice to account for nonlinear gain components is to complement the equation for the gain, g = gcΔn, gc is the gain cross-section, by a compression factor f. In this paper, improved (but still simple) models of the optical gain in QCL are proposed, which preserve the two-component gain structure. With these models, there is no need to solve the Hamiltonian with time-dependent potentials, so that extraordinary numerical loads can be avoided, but simultaneously the essential physics of the phenomena is kept. The improved gain models defined by Eqs.(12), (15) and (16) enable accounting for its nonlinear components while preserving the load-saving, scattering-like approach to light-matter interaction. It is also shown that as long as the populations and dc coherences are determined such that they account for the interaction with the optical field, the small-signal formulation of the gain gives its realistic estimate also for a large optical signal. This conjecture validates the use of non-equilibrium Green's function-based approaches, in which the interaction with the optical field is included through electron-photon selfenergies. The small-signal formulation of the gain can be used in this approach to monitor the saturation process, estimate the clamping flux and the light-current characteristic.

A modern survey method for determining extraordinary loads based on multi-source online data

Induced by unusual events such as people gatherings or furniture stacking, extraordinary loads rarely occur but can exhibit significant amplitudes. Though, sufficient statistical data are required to quantify the stochastic behavior of such loads, traditional surveys typically depend on manual on-site questionnaires, leading to low efficiency, occupant resistance and problematic weight estimation. In this study, multi-source online data are therefore used to propose a new survey method. Object weights are obtained from commodity information on e-commerce websites. Object quantities and occurrence intervals are acquired from questionnaires whose distribution employs an online user database. Using the proposed method, an online extraordinary load survey is conducted on residential buildings, covering 43,941 [Formula: see text] of floor area and collecting 14,186 weight samples. Three types of extraordinary loads are considered and their statistical properties of amplitudes and occurrence intervals are determined. The survey results indicate that the variations of amplitude statistics with area are well fitted by a form of the power function. On average, furniture stacking events are found to occur 0.07 time per year, but are most likely to exhibit a considerable amplitude. Finally, the acquired data are utilized to determine the fractile values of the lifetime maximum extraordinary loads.

Prevention of collapse: Analysis and Design

Throughout the ages men were engaged in construction activities besides other pursuits - to build their dwellings and shelter other activities. They willed to make these structures safe and free from collapse and hence employed various methods and designs. However in spite of all precautions it is impossible to guarantee the safety from collapse and destruction due to unforeseen causes. Some of the causes could be related to human errors like: poor design, faulty construction, foundation failures, extraordinary loads, compromising on quality of building materials, workmanship for economic reasons, negligence in enforcing building codes and their compliance laxity in supervision, inspection and approval by authorities etc. the other cause could be gas explosions, soil liquefaction, terrorist attacks, material degradations etc. It is admitted that it is uneconomical to design the structure for unforeseen events unless they have a reasonable chance of occurrence. The project study “Prevention of collapse: Analysis and design” ispresumedto help understand the collapse behavior of structure and accordingly design to prevent drastic, severe failures and save human lives and property. Secondly the practices employed to ensure safety and prevent collapse are to incorporate redundancies in structure in the form of detailing, ductile designs, tying of elements at particular locations, provision of hinges and their connections. However this study is limited to understand the outcome of failures for G+5 = buildings for column loss on different storeys, the adjacent beams, the increased loads on columns and footings studied and its resistances to failures and accordingly some measures are noted to prevent further collapse and danger.

Horizontal impact loads and torsional moment induced by partial cargo shifts

Previous studies demonstrate that significant cargo shifts occurred in all cargo holds of vessels in carriage of nickel ores may lead to catastrophic consequences of ship capsizing and sinking. Nevertheless, partial cargo shifts, despite its seldom occurrence in other types of vessels, are not unusual in bulk carriers, specifically for those with nickel ores which tend to liquefy as vessels experience long-time engine vibrations or unfavorable oblique waves. Regrettably, it has not been well described in previous literatures, therefore overlooked by ship operators and naval architects in ship structural design. The instantaneous impact loads to vessel's structures induced by partial cargo shifts, thus, remain unclear. Despite partial cargo shifts being unlikely to lead to life lost or ship capsizing, critical damage to cargo holds, shell plates and precise apparatuses in the wheelhouse can be identified frequently, sometimes even causing ship a hazardous list of 6–15°. Unfortunately, a number of similar accidents occurred in S.E. Asia waters have been found without reporting these accidents to IMO due to various reasons. The instantaneous impact loads, involving the torsional moments and horizontal sectional loads, initially overlooked by plenty of naval architects but subsequently estimated by our research team, are really huge, usually giving rise to a dangerous list of vessels as well as apparent or underlying damage to vessel's configurations. Conventional approaches, such as potential flow theory, volume of fluid method, moving particle semi-implicit method, smoothed particle hydrodynamics, etc., are significantly limited by their unsatisfactory precision in predicting and calculating those extraordinary loads. Here we estimate the torsional moments and horizontal sectional loads in oblique waves at various exciting rolling frequencies using improved Finite Element approach. The final results yielded from the model tests are strikingly in line with that from the numerical approach, manifesting that the modified numerical method behaves in a reasonable manner in tracking and capturing the complicated surface of large viscous fluid.

Using Modern Experimental Equipment to Determine Process Vibration Effects on Building and the Human Body

The paper presents the original results of an experimental dynamic study of the impact of vibrations generated by a manufacturing process on a building and its occupants. Machinery can cause extraordinary dynamic loads through technical seismicity. For research and education purposes, the article includes a methodology for measuring and evaluating random vibration in the context of assessing the adverse effects of vibration. In particular, this involves the identification of the dominant frequency bands, the amplitude and frequency composition, and the identification of the main source of vibration. For these purposes, the experiments were divided into different measurement stages. Each stage pursued a specific objective. The resulting processed data were evaluated according to the target impact groups. The paper includes an assessment of the vibration impacts on the building and human body, discussion, conclusions, and recommendations.

Heavy load carrying and musculoskeletal health: An exploratory study of biomechanical risk factors among sand miners in Pokhara, Kaski District, Nepal

BackgroundTrends in urbanization contribute to the growing global demand for raw construction materials. The health effects of load carrying among occupational groups that mine and carry sand and stone used for construction of roads and buildings remains poorly understood. MethodsWe conducted an exploratory cross-sectional study among a convenience sample of sand miners working at an excavation site on the Seti River in Pokhara, Nepal. Load carrying weight, duration, and frequency were used to categorize miners as having “low” or “high” load-carrying exposures. Musculoskeletal disorders (MSDs) were identified using self-reported symptoms of moderate to severe musculoskeletal pain, as well as physical examinations. ResultsThe average loads carried by female and male sand miners weighed 66 kg and 87 kg, respectively. Among all participants (N = 42), 45% reported moderate to severe musculoskeletal pain in at least one body region and 16 (38%) had MSDs identified using specified case criteria. The prevalence of MSDs was lower among miners carrying, on average, heavier loads compared to those carrying lighter loads (OR = 0.18; 95% CI: 0.04, 0.7), possibly indicative of the healthy worker survival effect. Miners carrying loads for longer durations had higher odds of MSDs compared with those carrying for shorter durations. ConclusionThis study has provided data on the extraordinary loads carried by sand miners in Nepal and preliminary evidence of health impacts associated with these loads. However, larger epidemiologic studies are needed to justify action to protect the health and safety of these unrecognized and understudied groups.

The effects of 12\u2009weeks of functional strength training on muscle strength, volume and activity upon exposure to elevated Gz forces in high-performance aircraft personnel

BackgroundTechnological advancements in modern military and acrobatic jet planes have resulted in extraordinary psychophysiological loads being exerted upon flying personnel, including inducing neck and back pain. The purpose of this study was to examine the effects of 12 weeks of functional strength training on 1) the volume and strength of the neck and shoulder muscles and 2) muscular activity upon exposure to helmets of different masses and elevated Gz forces in a long-arm centrifuge in high-performance aircraft personnel.MethodsEighteen participants underwent 12 weeks of functional strength training (n = 12) or the control protocol (n = 6) without additional strength training. Pre- and post-intervention tests included evaluations of isometric strength of the head extensor muscles, flexion, and lateral flexion and rotation, as well as magnetic resonance imaging (MRI) to measure the volume of the m. sternocleidomastoideus, m. trapezius, and deep neck muscles. Furthermore, during a long-arm centrifuge (+ 1.4 and + 3 Gz) protocol, the muscular activity levels of the m. sternocleidomastoideus, m. trapezius and m. erector spinae muscles were assessed without a flight helmet, with a helmet, and with a helmet and night vision goggles. Each participant’s perception of muscular strain was noted immediately after the long-arm centrifuge protocol.ResultsThe maximal isometric strength in all exercises and muscle volumes increased in the training group but not the control group (P < 0.05). Relative muscle activity (%MVC) with a helmet decreased after the intervention in the training but not the control group (P = 0.01). Relative muscle activity while wearing a helmet and night vision goggles was higher after intervention in the control group than in the training group (P < 0.01). The perceived muscular strain of the neck muscles induced by the long-arm centrifuge did not differ between the groups.ConclusionTwelve weeks of functional strength training improves the maximal isometric strength and volume of neck and shoulder muscles and leads to lower relative muscle activation upon exposure to elevated Gz forces in a long-arm centrifuge.

Analysis of Selected Assets against the Extraordinary Loads

The current security situation in the world creates pressure to improve the pro-tection of critical infrastructure assets against negative events, such as bomb attacks, industrial accidents, explosions, or fire. The research at the Faculty of Security Engineer-ing is focusing on such extraordinary loads. The present paper analyses selected assets against extraordinary load and describes their experimental testing.

A case study of the collapse of the over-chamber reinforced concrete ceiling of a meal silo

This paper discusses the failure of the over-chamber reinforced concrete ceiling of a cylindrical silo for storing extracted rapeseed meal. The failure resulted from the caving in of an arch formed in the chamber and the sliding down of the material column. Some factors contributing to the caking and arching of the cohesive materials stored in silos are identified. An analysis of the extraordinary loads during the autogenous or induced clearance of arches is made. Such loads are not taken into account by design standards. Attention was paid to the necessity of figuring these loads in the design (an own proposition was put forward); also, ways of preventing such impact or its limitation were pointed out. The direct cause and the indirect causes of the failure are determined. Design and utilization errors which contributed to the formation of the arch, the failure of the ceiling of silo and the compounding of the failure consequences are identified.

Reliability of laminated veneer lumber (LVL) beams manufactured from early to mid-rotation subtropical hardwood plantation logs

This paper presents the reliability analysis of Laminated Veneer Lumber (LVL) beams manufactured from veneers recovered from early to mid-rotation (juvenile) subtropical hardwood plantation logs, with plantations established either for sawn timber applications or pulpwood production. While these logs have a high number of natural defects (knots, gum veins, grain deviation, etc.), are considered of low quality and have little to no commercial value, they produce high strength Veneered Based Composite products, such as Plywood and LVL. Yet, the reliability of these products is unknown. In this paper, the relationship between the reliability index and the capacity factors, also referred to as “resistance factors”, used in design equations of such LVL beams in both edge and flat bending is investigated taking into account the load duration effects (damage accumulation). The relationship is presented for six different beam sizes, four grades and three hardwood species (Gympie messmate (Eucalyptus cloeziana), spotted gum (Corymbia citriodora) and southern blue gum (Eucalyptus globulus)) using the strength distribution of the beams recently quantified by the authors. Parametric studies on five main design load combinations stipulated in the Australian standard and three rates of damage accumulation, based on the data available in the literature, are conducted. Results show that the reliability index is highly sensitive to the damage accumulation rate and that the “Dead + Sustained and Extraordinary live loads” and “Dead + Wind + Sustained live loads” load combinations govern the choice of the capacity factor. Recommendations are made on the appropriate capacity factors to be used for various service categories of structures. The proposed capacity factors are found to be 5%–12% lower than the ones currently used in Australia for the LVL beams manufactured from mature softwood logs, as opposed to juvenile hardwood logs as in the proposed products.

Problems of application and automation of methods of evaluation of risks of projects of objects reconstruction

The urgency of the problem. Process of reconstructing objects faces many challenges and risks. The problem of risk assessment in construction is of paramount importance. This is due to erosion of an increasing number of modern structures with extraordinary structural features and loads, increasingly world-wide scales of reconstruction in difficult geotechnical conditions with a high degree of responsibility in reconstruction of capital construction objects. Purpose - is to identify and consider application and automation of risk assessment of reconstruction projects. Methodology. The problem of automation of risk assessment of reconstruction projects to date hasn’t been properly addressed. This is largely due to use of technical and economic substantiation of objects of construction and reconstruction of methods for risk assessment, which doesn’t fully take into account the specifics of construction activity of objects and peculiarities of their exploitation. Investigation of existing quantitative and qualitative methods of risk management allows us to conclude that they need to be developed and improved to be used for design, construction, reconstruction, repair of construction objects. This is especially true of risk management in construction activities. The reason for this is changing prices for building materials and construction, transportation and operation of construction machinery, machinery and equipment, transportation of workers to construction sites, travel expenses when performing work in other regions. The brief description of each method is given in article. Features of their application are analyzed and revealed. Problems of use of risk management methodology in the management of building projects are formulated. Conclusions. To manage and automate risks of reconstruction projects, need to understand scope and objectives of software to use the appropriate automated risk management tool. The automated risk management tool doesn’t guarantee success, but serves main purpose of storing and analyzing identified problems, timely response. Definitely, each project is unique and requires adaptation and adjustment of selected automated tools for its practical implementation. This set of criteria should be defined for each specific project and consider the objectives of the implementation, the objectives of risk management process, the size of the reconstruction project and its needs, the ability to integrate with the required standards and methodologies.

The Dawn of Thiol-Yne Triazine Triones Thermosets as a New Material Platform Suited for Hard Tissue Repair.

The identification of a unique set of advanced materials that can bear extraordinary loads for use in bone and tooth repair will inevitably unlock unlimited opportunities for clinical use. Herein, the design of high-performance thermosets is reported based on triazine-trione (TATO) monomers using light-initiated thiol-yne coupling (TYC) chemistry as a polymerization strategy. In comparison to traditional thiol-ene coupling (TEC) systems, TYC chemistry has yielded highly dense networks with unprecedented mechanical properties. The most promising system notes 4.6 GPa in flexural modulus and 160 MPa in flexural strength, an increase of 84% in modulus and 191% in strength when compared to the corresponding TATO system based on TEC chemistry. Remarkably, the mechanical properties exceed those of polylactide (PLA) and challenge poly(ether ether ketone) PEEK and today's methacrylate-based dental resin composites. All the materials display excellent biocompatibility, in vitro, and are successfully: i) molded into medical devices for fracture repair, and ii) used as bone adhesive for fracture fixation and as tooth fillers with the outstanding bond strength that outperform methacrylate systems used today in dental restoration application. Collectively, a new era of advanced TYC materials is unfolded that can fulfill the preconditions as bone fixating implants and for tooth restorations.

Small RNAs from a Big Genome: The piRNA Pathway and Transposable Elements in the Salamander Species Desmognathus fuscus.

Most of the largest vertebrate genomes are found in salamanders, a clade of amphibians that includes 686 species. Salamander genomes range in size from 14 to 120Gb, reflecting the accumulation of large numbers of transposable element (TE) sequences from all three TE classes. Although DNA loss rates are slow in salamanders relative to other vertebrates, high levels of TE insertion are also likely required to explain such high TE loads. Across the Tree of Life, novel TE insertions are suppressed by several pathways involving small RNA molecules. In most known animals, TE activity in the germline is primarily regulated by the Piwi-interacting RNA (piRNA) pathway. In this study, we test the hypothesis that salamanders' unusually high TE loads reflect the loss of the ancestral piRNA-mediated TE-silencing machinery. We characterized the small RNA pool in the female and male adult gonads, testing for the presence of small RNA molecules that bear the characteristics of TE-targeting piRNAs. We also analyzed the amino acid sequences of piRNA pathway proteins from salamanders and other vertebrates, testing whether the overall patterns of sequence divergence are consistent with conserved pathway function across the vertebrate clade. Our results do not support the hypothesis of piRNA pathway loss; instead, they suggest that the piRNA pathway is expressed in salamanders. Given these results, we propose hypotheses to explain how the extraordinary TE loads in salamander genomes could have accumulated, despite the expression of TE-silencing machinery.

Influence of Anchoring Cables Position on Load Carrying Capacity of Tension Transmission Tower

In the last stage to install conductors to insulation chain hanging on transmission tower conductors have to be pulled extra 20cm. Small shortening of conductors (in comparison to span length) cause much greater horizontal forces imposed on tower supporting conductors. These forces are not taken into account when the tower is designed under normal loads. The paper deals with analysis of the tension transmission tower M6W, designed according to standard procedure and subjected to extraordinary loads when power and ground conductors have to be installed with help of anchoring cables.The main goal of this paper is to specify safe combination of different parameters: the distance between the axis of tower and anchoring foundation, position of winch, influence of existing already installed conductors.

Fatigue assessment of AA 8090 friction stir butt welds after surface finishing treatment

Combining great performances with high standards of safety and efficiency is the challenge for most aircraft manufacturers. Aircraft are subjected to extraordinary loads, repeated for millions of cycles also in extreme environmental conditions, hence every component must be designed and manufactured to maximize its fatigue resistance.Friction Stir Welding of aluminium alloys and surface finishing process as might be a good solution to reach this goal.The high performances reached in this field with the use of this technique could be further increased reducing the welded surface irregularity, which might promote the development of a dangerous fatigue failure mechanism.In this work, the effect of the welded surface finishing treatment on the fatigue behavior of AA8090 FSW butt joints was assessed. The results obtained from the dynamic tests highlighted the higher fatigue resistance of finished specimens, with respect to the as-welded joints.

Preliminary dust-impact risk study for the “Solar Probe” spacecraft

Solar Probe is a mission currently under study, funded by the NASA's Office of Space Science—Sun–Earth Connection theme. This mission seeks to achieve the first visit to the Sun to explore the physical phenomenon that occurs at close proximity to our star. The mission requires the spacecraft to follow a polar orbit around the Sun with a perihelion of four (4) solar radii. A flyby at this close distance from the Sun will put the spacecraft under extraordinary environmental loads. One of the concerns is the effect that interplanetary and interstellar dust will have on the integrity of the spacecraft. The maximum dust impact velocity is expected to be around 500 km/s. This velocity is well above current experimental capabilities—more than an order of magnitude higher. For this reason, numerical simulations appear to be the best tool to determine the expected level of damage generated by the solar dust on the structural components and instruments of the Solar Probe spacecraft. Presented here are the results of the analysis of the dust environment to be experienced by the spacecraft and the shielding design parameters for different components. The design parameters of various structural components and instruments were used to conduct computer simulations using CTH to study shielding concepts.