Design Load Research Articles

Responses of air-conditioning loads to climate change and its impact on carbon emissions in the hot summer and warm winter climate

Energy consumption of air-conditioning in wet and hot climates is not only for cooling but, to a large extent, for dehumidification. Taking urban agglomeration in the Pearl River Delta region as a case study, this study analysed the cooling and dehumidification loads during the past 20 years. In addition, the impacts of cooling and dehumidification loads on carbon emissions were determined. The results showed that there was large spatial heterogeneity in the variations of the cooling and dehumidification loads. The cooling design loads in 1991–2020 was increased 1.83% to 5.56% compared to those in 1971–2000, while the loads for dehumidification was decreased 0.92% to 5.5%. Carbon emissions from cooling were increased, exceeding the carbon reduction from dehumidification, which leads to a weak increase in total carbon emissions. This study revealed that air-conditioning design should fully consider climate change impact by separating cooling and dehumidification loads, increasing the cooling load to avoid insufficient air-conditioning output but reducing the dehumidification load to promote energy efficiency of the air-conditioning system and to reduce carbon emissions. More importantly, an assessment of design loads with climate change in city or small scales should be made before determining summer air-conditioning system design capacity.

Study of erosion-induced leakage flow in guide vane of Francis turbine using erosion-coupled mesh deformation simulations

Erosion of the hydro-turbine components in sediment-laden flows results in a reduction in the efficiency and life of turbine components. The particles in the water affect the operation of both stationary and dynamic components. In the present study, the guide vanes and facing plates of a Francis turbine are numerically investigated regarding their susceptibility towards erosion using an erosion-induced geometry deformation approach. The effects of non-uniform changes in the clearance gap between the guide vanes and facing plates on the erosion and leakage flow are explored. A segment of the actual distributor is analysed for the design and part load operation of the turbine. The simulations were performed for a period equivalent to 2400 h and the comparisons are drawn with the geometry at the end of 240 and 1200 h, respectively. The results show an increase in thickness loss with operation time, however, the position of maximum thickness loss shifted towards the tailing edge for guide vanes and towards center for the face plate. The increase in clearance gap leads to higher cross-flow across the clearance gap and thus, the crossflow and the erosion rate feed off each other. The erosion of the guide vane and face plate was symmetric for BEP but asymmetric for PL. Further, the simulations were performed with three different initial clearance gaps ranging from 0.5 mm to 1.5 mm highlighting the changes in erosion rate for different clearances. The present work provides important engineering insights for the design and operation of the Francis turbine guide vanes to control their erosion and leakage flow.

Exploring key factors affecting the ultimate compression capacity of Unbonded Steel-mesh-reinforced Rubber Bearings

To address bearing-sliding damage in highway bridges during seismic events, the Unbonded Steel-mesh-reinforced Rubber Bearing (USRB) was developed. This novel bearing employs flexible, high-strength steel wire meshes as reinforcement, enhancing lateral deformation capacity and reducing bearing-sliding risk. Recent seismic specifications increased the bearings' vertical design load to 30 MPa, where existing bearings with flexible reinforcements (e.g., fiber-reinforced bearings) fail to meet this standard. Hence, for the first time, our study thoroughly investigated the ultimate compression capacity of USRBs and the key factors influencing the capacity. Through ultimate compression tests on full-scale prototypes, we demonstrated that USRBs can comply with heightened seismic requirements, with primary failure attributed to the tensile failure of the steel mesh reinforcement. These tests were complemented by 3D finite element modeling in ANSYS, employing the LINK180 elements for mesh reinforcement and defining the ultimate capacity as the point at which reinforcement stress reached tensile strength. This particular modeling approach, validated against experimental data, can accurately predict the ultimate compression capacity and the force-deformation response of USRBs. A comprehensive parametric analysis, using the validated modeling approach and an advanced statistical method LHS-PRCC, was conducted to identify the key factors influencing the compressive capacity, including bearing geometric parameters (i.e., bearing width, the second shape factor, and rubber layer thickness), steel-mesh configuration characteristics, and steel-mesh material properties. Our findings emphasize the significance of rubber layer thickness, steel mesh weight, and steel wire tensile strength and strain in influencing the USRBs' ultimate compression capacity. Based on these key factors, an empirical equation for the ultimate compression capacity of USRBs was established to guide the optimization design of USRBs. This study not only fills the gap in USRB's performance under extensive compression but also provides a foundation for future optimization of these bearings to enhance their performance in bridge engineering.

Prevalence of Postural Deformities Among School Going Children in Rural Areas Due To School Furniture: A Cross-Sectional Study

Posture is an upright position that is generally kept against gravity. Body posture is influenced by many factors including general health, musculoskeletal alignment, body endurance, muscle strength, weight, height, fatigue, state of mind, and age etc. The perfect collaboration between segments of the body is called good posture. The imperfect collaboration between segments of the body is called bad posture. Abnormal body posture can cause various musculoskeletal disorders along with headache, fatigue, cervical and lumber pain. The prevalence of musculoskeletal disorders in school going children can be reduced by macro and micro ergonomic approach such as postural awareness, furniture design and bag pack loads carriage. School pupils sit for many of their classroom lessons and adopt different postures. An inappropriate body posture can destroy a student’s interest, even during the most stimulating lecture. School children attend schools for a considerable amount of time, 6 h a day on average. They spend the largest part of their time at school performing different related activities, which lead them to be seated on their seats constantly for a long time. Classroom furniture is usually not designed to accommodate the dimensions of the individual user. Considering that school is an ideal setting for the acquisition of healthy habits that can continue into adulthood, it is necessary to implement actions to identify ideal school furniture dimensions.

A new highway cost allocation framework in the day of connected and autonomous vehicles

The objectives of the present study are to explore potential changes expected in highway infrastructure expenditures and revenues, and develop a robust framework that will facilitate highway cost allocation when connected and autonomous vehicles (CAVs) are in operation. The scope of this study covered both federal and state expenditures and revenue sources. The highway cost allocation elements covered in the paper include vehicle miles of travel, highway expenditures highway revenues, and equity analysis. In the day of CAVs, significant changes are expected in all these elements, and these changes are incorporated into the proposed highway cost allocation framework. Pavement-related expenditures would increase due to the addition of CAV-related infrastructure integrated into the pavement infrastructure to ensure it is an intelligent pavement. Bridge-related expenditures are expected to increase due to the infrastructure technologies on the bridges making them smart bridges, and the design loads of these bridges may have to be increased due to potential platooning on long span bridges. It is expected that many of the CAVs on the road will be electric vehicles. All these changes are incorporated into the proposed highway cost allocation framework.

Co-Influence of Restoration Bonding and Inlay Cavity Design on Fracture Load of Restored Tooth.

The aim of this study was to investigate the co-influence of indirect mesio- occlusal-distal (MOD) cavity geometry and inlay restoration bonding on quasi-static fracture load of the restored tooth. Forty-eight intact human molar teeth were selected and prepared for standardized edge-shaped or round-shaped MOD cavities. The resin composite (Cerasmart, GC) inlays were bonded with the state-of-the-art inlay bonding protocol or with intentionally deteriorated bonding using n-hexane-wax solution for preconditioning. Restored teeth were loaded along the long axis of the tooth. Ultimate fracture load was recorded, and the type of fracture was visually determined and classified. Statistical analysis of load values was performed by Kruskal-Wallis test. Round-shaped cavity design with bonded restoration presented the highest fracture load (1658N). Bonding had significant influence on the fracture load of roundshaped cavity design (p=0.0003), whereas cavity design had no influence when the bonding was deteriorated (p=0.8075). In the case of deteriorated bonding, either the inlay or tooth fractured separately whereas in the bonded inlays fractures were commonly found both in the tooth and inlay. According to this study, bonded inlay restoration increased fracture resistance, while cavity design had no statistical difference on fracture resistance of the restored tooth.

Subregional Differentiated Safety Factors Design Based on Nonprobabilistic Structural Reliability

The structural safety factor is an essential parameter in aircraft design, representing the ratio of the design load to the operating load. Traditional design methods rely on subjective determination of safety factor values based on experience, lacking objectivity in quantifying uncertainty. However, with advancements in aircraft design technology and increasing competition in the commercial space market, new-generation hypersonic aircraft with complex load environments require a more optimal approach. Applying a uniform safety factor to each component within subregions of the aircraft leads to overly conservative results and impacts flight performance. To address this limitation, a design scheme that incorporates subregional, differentiated safety factors is necessary. This approach allows for better material utilization and ensures compliance with safety requirements. This paper utilizes reliability-based design optimization theory to consider uncertainty in structural systems. It establishes a mapping relationship between structural reliability and differentiated safety factors, providing safety under uncertainty while guaranteeing weight reduction. Additionally, this paper develops a subregional, differentiated safety factors distribution program to determine the safety factors of different subregions of the structure. Consequently, a refined subregional differentiated safety factors scheme that balances safety and economy is derived.

The displacement mechanism of the cracked rock – a seismic design and prediction study using XFEM and ANNs

Materials with sufficient strength and stiffness can transfer nonlinear design loads without damage. The present study compares crack propagation speed and shape in rock-like material and sandstone when subjected to seismic acceleration. The nonlinear extended finite element method (NXFEM) has been used in numerical simulation. It assumes the model has a pre-existing crack at 0° from the horizontal. The mechanical properties of the model, crack propagation shape, and crack speed were selected as the main parameters. The nonlinear stress and strain along the crack have been compared in two simulated models. NXFEM and Artificial Neural Networks (ANNs) were used to predict the displacement. The simulation results illustrate that the materials’ crack propagation mechanism and mechanical properties control the stress, strain, and displacement at the selected points in the model. In addition, crack propagation in materials is related to elastic-plastic stresses and strains along the crack path. The speed and shape of the crack are associated with the mechanical properties of the materials. The prediction of crack paths helps to understand failure patterns. Comparison of the seismic response of the rock-like material with sandstone helps to assess the stress, strain, and displacement levels during cracking. This study’s findings agree with the literature report and field observations.

Tensile strength analysis of sandwich composite-to-metal joints based on experimental investigation and progressive failure method

In this study, the tensile strength characteristics of the hybrid sandwich composite-to-metal specimen consisting of two steel I-beams and a T-shaped sandwich composite structure were studied. The tensile strength of the sandwich hybrid joints under design load and ultimate load has been tested. The progressive failure model is established according to the modified Shokrieh-Hashin criterion. The interface cohesive zone model is applied to reveal the damage development of the bonding layer. The stresses, strains, ultimate strength, and main damage modes of the hybrid joint under design load and ultimate load conditions are simulated and the predicted results are compared with those from tests. The experimental and numerical results show that the strain, the trend of load-displacement curves and the damage modes are in good agreement. The strength of matrix is the main factor limiting ultimate strength. Therefore, the influences of the overlapping width and thickness on ultimate bearing capacity were analyzed to obtain the optimized structural strength of the sandwich composite-to-metal bolted joints.

Influence of Excitation by Idling Rotor on Wind Turbine Ultimate Loads in Storm Conditions

Typical large scale pitch-controlled wind turbines idle their rotors during storm conditions. The design loads of wind turbines are calculated by aeroelastic simulations under various conditions. These include grid loss and failures, which can increase rotor speed and excite the first-mode of the tower bending. In this study, the influences of self-excitation by the idling rotor on the ultimate loads in storm conditions were investigated. Aeroelastic simulations were conducted for a three-bladed 5 MW upwind turbine as an example, under steady and extreme turbulent wind conditions according to the international design standard IEC61400-1 ed.4. As a result, we confirmed that yaw misalignment increases the idling rotor speed and 6P, second order harmonics of blade passing frequency, excites the first-mode tower bending, which can generate a large load on the tower. Pitch stick can increase the rotor speed but not as noticeably as yaw error. Although no clear provisions exist in wind turbine design standards or guidelines for the self-excited vibration during wind turbine idling, these results indicate that conditions must be set that consider self-excited vibration.

Target shape approximation of funicular surfaces by load control using RBF interpolation

Existing methods for form-finding prioritize discovering optimal shapes under design load conditions, often overlooking the designer’s shape preferences. To address this problem, this research relaxes the load condition and develops a user-friendly form-finding tool that encapsulates a new method for obtaining funicular surfaces that pass through user-prescribed points through load control. The method involves generating smooth load distributions via RBF interpolation of nodal loads, which are repeatedly adjusted so that the equilibrium shape is close enough to the target points. For faster convergence, the step size of the load adjustment is automatically determined through a coarse line search, and a warm start is introduced in form-finding with the dynamic relaxation method. Despite uneven load distributions, the method ensures high accuracy in approximating the surface shape to the desired points while preserving funicularity against the load distributions. Additionally, the resulting load distribution gives designers valuable feedback on the specified target points, as the degree of load non-uniformity indicates the deviation from the equilibrium shape for uniformly distributed loads.

Towards standardised design of wave energy converters: A high-fidelity modelling approach

Within this study, an analysis of the global standard panorama for wave energy converters (WECs) is presented, in order to develop design methodologies as close as possible to the state-of-the-art. In particular, an analysis of such international standards panorama exhibits a lack of information and detail regarding WEC system design, and the specific simulations procedures that shall be followed accordingly. In the light of this, this study proposes a standardised design process that can be followed to define the design loads which characterise a structural analysis, which are obtained by high-fidelity models. The device assessment in extreme states is analysed on intact and damaged conditions, where the use of a computational fluid dynamics (CFD) software is proposed to encompass any non-linear behaviour related to extreme events. Furthermore, this article also describes a fatigue assessment based on linear system theory, with the inclusion of linearised significant terms, such as, e.g. mooring influence on device dynamics.

The Impact of Increased Traffic and Explosion Loads on the Concrete Bridges Baniwalid Bridge - Case Study

The Baniwalid Bridge is located at the entrance of the city. This bridge was implemented during the seventies of the last century and was opened to traffic in the eighties. It is considered the main artery for traffic, linking the two sides of the city. Its length is about 500m, and its width is 20m. It has two directions; each direction is 8 meters wide. The construction system of the bridge consists of 31 average spans, each of which is 14.5 meters long, and each span consists of 18 pre-stressed beams, with a height of 0.72 meters and a width of 1.00 meters. Traffic increased within the city in previous years as a result of the closure of the coastal road, which led to a change in the movement of freight and land transport to eastern and southern Libya through the cities of Baniwalid and Gharyan, where the bridge was subjected to very high traffic loads that far exceed the design loads. In this study, the bridge was inspected, some previous reports were reviewed, and the construction status of the bridge was determined in general. There are many cracks in the bridge due to water, shells and increased traffic. The foundations were also exposed to erosion due to torrential rains. In general, the bridge needs immediate maintenance.

Physical and Numerical Models of Mechanically Stabilized Earth Walls Using Self-Fabricated Steel Reinforcement Grids Applied to Cohesive Soil in Vietnam

Mechanically stabilized earth (MSE) walls have been widely applied in construction to maintain the stability of high embankments. In Vietnam, imported reinforcement materials are expensive; thus, finding locally available materials for MSE walls is beneficial. This study examines the behavior of an MSE wall using local reinforcement materials in Danang, Vietnam. The MSE was reinforced by self-fabricated galvanized steel grids using CB300V steel with 3 cm ribs. The backfill soil was sandy clay soil from the local area with a low cohesion. A full-scale model with full instrumentation was installed to investigate the distribution of tensile forces along the reinforcement layers. The highest load that caused the wall to collapse due to internal instability (reinforcement rupture) was 302 kN/m2, which is 15 times greater than the design load of 20 kN/m2. The failure surface within the reinforced soil had a parabolic sliding shape that was similar to the theoretical studies. At the failure load level, the maximum lateral displacement at the top of the wall facing was small (3.9 mm), significantly lower than the allowable displacement for a retaining wall. Furthermore, a numerical model using FLAC software 7.0 was applied to simulate the performance of the MSE wall. The modeling results were in good agreement with the physical model. Thus, self-fabricated galvanized steel grids could confidently be used in combination with the local backfill soil for MSE walls.

Using numerical simulation to analyze the strength properties of the developed demountable body of a trolley

One of the safest types of public transport is the metro, which is actively developing in many countries. Despite a number of advantages, the construction of metro tunnels is a rather labor-intensive process, which involves complex technical equipment in the form of tunnel boring complexes. Tunnel boring complexes include locomotives that perform the functions of hauling away rock using trolley with removable body. Trolley differs from their usual characteristics - in weight, dimensions, as well as the component composition of individual systems, in particular the compressed-air braking system. The article is devoted to the analysis of the parameters of the stress-strain state of one of the main load-bearing elements of a trolley- the casing. As a result of the analysis, design loading cases were selected, the most loaded parts of the body were determined, recommendations were formed for choosing the optimal material thickness of various elements and increasing the load-bearing capacity of the body.

A Review on Design and Analysis of Foot Over Bridge

Abstract: foot over, which is defined as the bridge that is constructed for pedestrian crossing purposes. The detail and preliminary survey were performed before any design began. The majority of mass movement analysis is performed for live load purposes. The load are considered for design is live load, dead load, wind load , seismic load for design. The design of the foot over bridge was done with mostly software from Staad Pro. The methodology accepted mostly for design is modeling, defining and assigning material and sectional properties, putting boundary conditions in place, applying loading, analysis and design, interpretation results, and conclusions. The conclusion that the Staad Pro software is mostly claimed to be easy to use and simpler than other. The wind load has a reduced effect on the bridge by giving a large opening. The cable material is mostly suitable for the foot-over bridge. A detailed analysis is required to know the exact live load calculation. The steel truss bridge is mostly used for foot-over bridges.

Structural assessment of an ASR-affected reinforced concrete bridge

ASR (alkali-silica reaction) has long been acknowledged as a key consideration when designing concrete structures in South Africa. This study raises awareness of the influence of ASR on the structural behaviour of reinforced concrete bridge structures. Aggregate type plays a role in how the ASR develops over the structural life cycle. Greywacke aggregate is found to be prominent in ASR-affected structures within the Western Cape region, and in the structure that was investigated. ASR decreases concrete tensile strength, compressive strength, and E-modulus over time. To develop a standardised approach that can be replicated on other bridge structures, a simply supported rectangular reinforced concrete bridge deck slab was analysed. The slab was modelled according to the construction drawings, including the reinforcement detailing, to determine the ultimate shear and moment resistance according to the code (BS 1972) used for the original design, and current Eurocode standards, for both unaffected and ASR-affected concrete. Traffic load was determined from the relevant TMH7 standard, and from weigh-in-motion data collected at a station on the high-traffic-volume route crossing the bridge. Due to compressive strength being the least affected material property by ASR deterioration, the ultimate resistance to original design loads was found to be sufficient.

Procedure for evaluation of LNG CCS with reference vessel using nonlinear dynamic analysis

This paper presents a procedure for evaluating the structural safety of Liquefied Natural Gas (LNG) Cargo Containment System (CCS) against sloshing load by comparing the results of linear and nonlinear dynamic structural strength analysis with those of verified reference vessels. This comparative procedure indirectly considers (1) limitation of implementing real physical phenomena in model experiments including the Froude scaling method, density ratio, etc., (2) assumptions in statistical analysis for calculating design loads, and (3) complicated effects not implemented in nonlinear dynamic analysis such as phase transition between liquid and gas, hull deflection, and the detailed geometry of the CCS, among others. The uncertainties in sloshing model experiments and statistical analysis can be addressed by introducing the pressure correction factors, which make the linear design loads of the reference vessel satisfy the CCS’s capacity. Finally, the structural nonlinearity, which was not accounted for in the nonlinear dynamic analysis, can be taken into consideration through a comparison of the usage factors from nonlinear dynamic analysis. To apply the proposed structural assessment procedure, the GTT NO96 series were selected and applied to two failure modes. In the application of this procedure, the Triangular Impulse Response Function (TIRF) method was adopted, to efficiently calculate numerous linear dynamic structural strength analyses required for Dynamic Amplification Factor (DAF). Through this application applying larger sloshing loads to the reinforced NO96 CCS of the target vessel compared to the reference vessel, the feasibility of this procedure was shown.

An approach for cost and configuration optimization of horizontal axis wind turbine (HAWT)

In addition to the environmental advantage of wind turbines, the modern wind turbine design is aiming to become more competitive by minimizing the cost of energy (COE). When evaluating any change to the design of a wind turbine, it is critical that the designer evaluates the impact of the design change on the system cost and performance. A typical problem when start a wind turbine design project is to determine the optimum configuration and operation parameters to minimize COE. In this article an optimization approach is adopted using COE as objective function with the rotor size, power rating and rated rotational velocity (RPM) as design variable. The cost of energy model of the National Renewable Energy Laboratory (NREL) is adopted with modifications to include the main components load level effects on the COE. An aerodynamic blade design is developed and used as base for evaluating the rotor performance. The blade is scaled to present different rotor size and operating conditions for each power rating. Analysis tool is developed to consider coupled interactions between power rating and the rotor size. The Blade Element Momentum (BEM) technique is used to evaluate the effect of configuration and operational conditions on the wind turbine load levels and the expected annual energy production (AEP). These are used as inputs for the proposed COE model in addition to main parameters presenting the manufacturing technology and site conditions. The COE model is based on several elements such initial capital cost (ICC), balance of station (BOS), operations and maintenance (O&M), levelized replacement cost (LRC), AEP and design load levels. A pattern search technique is adopted for the optimization and the approach is illustrated by means of a principle test examples for two types of turbines platform one for low wind onshore site and another for high wind offshore site.

Experimentally and numerically verified behaviour of splice joints under multiple loading conditions and their capacity predictions using artificial neural networks

Splicing steel beams is a widely adopted practice, necessitated by span constraints that arise from challenges in transporting and handling longer beams, which may jeopardize the safety of the onsite workforce. The spliced joint must possess adequate strength and stiffness while effectively distributing the design loads without compromising the structural stability of the system. In this paper, an experimental study was carried out on various spliced joints, followed by finite element-based simulations on the validated girders. Extensive finite element analyses were conducted to investigate the influence of the width and thickness parameters of the splice plates under both three-point and four-point loading. Under both these loading conditions, superior performance was attained when a thicker flange splice and a thinner web splice were adopted. Strength improvements of 10% and 4% were achieved when the width of the flange splice (WFS) was dropped from 140 mm to 50 mm while maintaining a constant width of the web splice (WWS) at 270 mm, under three-point and four-point loading conditions respectively. Capacity enhancements of 16% and 23% were noted when WWS was raised from 60 mm to 270 mm while maintaining a constant WFS at 140 mm, under the above mentioned loading conditions, respectively. Lastly, the feasibility of artificial neural networks (ANNs) to predict the ultimate capacity of the splice joints was assessed, and it was verified that they could predict the ultimate load capacity with reasonable accuracy. The predicted load capacity of the splice joint outside the training set revealed that an appropriately trained and optimized ANN network could reliably estimate the strengths with a mean absolute error of less than 2%.