Load In Design Research Articles

Sensitivity analysis of structural response to position of external applied load in plate flexural condition

Procedures for discrete sensitivity analyses of the static responses of a structure, i.e., nodal displacements, mean compliance, local bending moments and stresses, are respectively developed for a plate or shell structure with regard to the position of an external load mainly because of the uncertainties related to the application point of a load in the preliminary design of an engineering structure. With the sensitivities developed herein, those responses can be estimated quickly and accurately by using the Taylor expansions after a position disturbance of the external load.Based on the classical theory of the finite element analysis, the shift influences of a point or distributed load are firstly transformed into the associated value variation of the equivalent nodal forces. As a result of this transformation, the first- and second-order derivatives of the external load to its movement are constituted readily in a regularized formulation. Subsequently, the relevant sensitivities of the structural responses aforementioned are developed upon the essential concepts of the discrete approach. Finally, two typical examples are provided to illustrate the implementation of the sensitivity analyses derived and their applications in a quick estimate of the structural response variation. The numerical results show a high accuracy of the response sensitivity calculation.

P-I Diagram Generation for Reinforced Concrete (RC) Columns Under High Impulsive Loads Using Ale Method

Reinforced concrete (RC) column systems are widely used in protective structures designed to resist blast events. Development of correlations between explosive load and the resulting damage in concrete elements are significant for incorporation of blast load in design and also for pre and post-damage assessments. The main purpose of this research is to organizing correlations between explosive load and damage. These correlations are being expressed in Pressure-Impulse diagrams. The damage level is calculated based on the residual axial load-carrying capacity of the damaged RC column. Finite element modeling in LS-DYNA is used to analyze the structures and calculate the damage level for each explosive phenomenon. The Arbitrary Lagrangian Eulerian (ALE) method is used to simulate the explosive loads in the reinforced concrete column. The results demonstrated that increase the column size cause to increase in pressure and impulsive asymptotes and lead to enhanced the pressure-impulse (P-I) diagram.

H-Plane and E-Plane Loaded Rectangular Slow-Wave Structure for Terahertz TWT Amplifier

A novel miniaturized rectangular slow-wave structure (SWS), composed of both H-plane and E-plane corrugations, is proposed for submillimeter or terahertz vacuum electron traveling-wave tube (TWT) devices. The advantage of this SWS is to enhance the interaction impedance, therefore, resulting in higher gain and improved output power of the device. In addition, this structure geometry permits design flexibility to achieve a better dispersion behavior (linear dispersion and wider bandwidth) and easy fabrication by available microfabrication processes. Incorporating an H-plane and E-plane load in the SWS design, we achieved a higher performance TWT amplifier with the central frequency of 400 GHz. Both electromagnetic characteristics and beam–wave interaction analysis are investigated using the 3-D electromagnetic software Computer Simulation Technology studio. The simulation results show that an enhanced interaction of the SWS is obtained, and the amplifier has wide instantaneous bandwidth of 80 GHz and 19.5-dB small signal gain at 400 GHz for 17-kV beam voltage and 20-mA beam current. A saturated output power of more than 19 W is obtained from the large-signal simulations.

Issues of alternating load in design of cold-formed steel frames with lap joints

Issues of alternating load in design of cold-formed steel frames with lap joints

Non‐linear seismic response analysis of vehicle‐bridge interactive systems

AbstractThe intention of this study is to investigate how vehicles on highway bridges affect the seismic responses of the bridges under strong ground motions. Most highway bridge design codes do not consider the live load in the seismic design of highway bridges because of the low probability of the two events of the critical live load and an earthquake occurring at the same time. As a result, little attention has been paid to the influence of vehicle loads on the seismic responses of highway bridges. However, considering the high probability of traffic jams on urban roads, it is preferable to examine and clarify the dynamic interaction effect of vehicles on road bridges while subjected to seismic loads. In this study, the vehicle‐bridge‐ground motion interactions are realized by combining ABAQUS and MATLAB. ABAQUS provides a GUI environment to establish the numerical bridge model and apply the seismic forces, while MATLAB provides a platform to control the iterations in both time and force increments. As a preliminary study, a simplified 3D pier‐beam bridge model loaded with multiple vehicles with two degrees of freedom moving at a constant speed has been considered. When subjected to identical, strong seismic loadings, it was observed that the transverse accelerations of the bridge with moving vehicles are smaller than those without moving vehicles. Further, permanent deformation occurs after earthquakes because of yielding at the bottom of the pier; it was observed that the permanent deformations of the bridge with moving vehicles tend to be smaller than those without moving vehicles.

Analysis on the Influence of the Primary Consolidation Settlement of the e~p Curves and the Soil Bulk Density of the Soft Soil Foundation

In general, primary consolidation settlement of soft foundation is calculated by layerwise summation method considering the design load in seawall engineering design, and the total settlement is obtained by multiplying a settlement correction coefficient which is difficult to select. In this paper, one seawall engineering case is enumerated, the impact on the thickness of compressible stratum and the primary consolidation settlement is studied by considering the changes of the e~p curves of the soft soil foundation. The results indicate that the thickness of the compressible stratum changes obviously for different stress ratio owing to the difference of the soil bulk density of the compressible soil, and the primary consolidation settlement has corresponding change tendency according to the shape of the e ~ p curves and the soil bulk density of the compressed soil. At last, this paper suggests that a designer can weaken the weight of settlement correction coefficient based on the analysis of the influence of primary consolidation settlement with different e ~ p curves of the soft soil foundation in future design.

Assessment of soil mixing with cement kiln dust to reduce soil lateral pressure compared to other soil improvement methods

The soil lateral earth pressure acting on retaining or wing walls of hydraulic structures is considered the most influential load in structural design of these walls. The general properties of the soil foundation and backfill soil are the factors that control the cost of engineering design of retaining or wing walls of hydraulic structures. Some water structures may be subjected to various forms of damage for reasons related to soil problems. These structures may need rapid intervention to repair these defects which are considered one of the most expensive and most complex flaws in the reform.In order to improve the mechanical properties of the soil backfill, which are reflected on the cost of new buildings or address problems of existing soil structures, this research compares between different soil improvement techniques, which can be easily applied to these kinds of buildings and has a significant effect. Many field tests were carried out to compare the retaining wall resistance to backfill soil using medium sand soils as backfill material processed in four different methods. These methods are filling sand using common compaction specifications, using sand filled baskets (gabions), soil reinforcement with geogrid and soil mixing with cement kiln dust.The results of experiments showed that the soil mixing with cement dust is considered the best method among the other used methods, although it may not be the fastest when considering the construction process.

강상자형교의 강바닥판에서 설계온도하중을 위한 유효온도 산정

국내 교량 설계에서 온도 하중에 대한 현재 LSD (한계 상태 설계법)는 다양한 교량 형식에 대한 동일한 기준을 적용하고 있다. 본 연구에서는 유효 온도를 산정하기 위해 실제 크기의 상판이 없는 강상자형거더교 시험체를 제작하였다. 1년동안 강상자형거더교모형의 18개 지점에서 온도데이터를 측정하였다. 측정된 데이터를 바탕으로 대기 온도에 따른 교량단면내 유효 온도를 산정 하였다. 유로 코드의 유효 온도와 비교할 때 실측 유효온도의 결과는 매우 유사한 상관 관계를 보였다. 따라서, 본 데이터를 기반으로 산정 된 유효 온도는 국내 교량 설계에 온도 하중에 적합한 설계 기준을 제시하기 위한 기초 자료로 사용할 수 있다. A present LSD (limited state design) code for temperature load in the domestic bridge design has applied a uniform standard for various bridge types. In this study, in order to calculate the effective temperature, a specimen of steel box girder bridge section with real size dimension was manufactured. For a year, the temperature data were measured at the 18 point in steel deck of steel box girder bridges specimen. Effective temperature within the cross section according to atmospheric temperature was calculated by this experiment data. The analyzed results were very similar correlation when compared with the effective temperature of the Euro Code. Therefore, the effective temperature which calculated based on the present data could be used as the basic data in order to present to the appropriate design criteria for the thermal loads on the domestic bridge design.

Wind Resistance Research and Wind Tunnel Test of Large-Span Roof Based on Yancheng Financial Center

A large number of buildings with large-span or complex-shape have come to the fore in recent years. To these structures, wind load tends to be control load in the structural design. Shape coefficient of wind load which Chinese load code for the design of building structures can provide is extremely limited due to complex-shape of long-span space structures, therefore carrying our related study is of great practical significance. Yancheng Financial Center model is established in this paper based on ETABS software. The acquired date in the use of wind tunnel test is to simulate wind load which is on the structure and to analysis stress distribution of critical element in order to ensure safety and applicability of structures. This paper mainly covers wind tunnel test, equivalent static wind load, and wind-induced response, etc.

Research on the Characteristics of Steel Frame Node under Explosive and Impact Load

With the characteristics of huge energy,short acting time and large destructiveness, Explosive and Impact Load leads a large punching force towards construction units. Once happened, it can cause serious of damaging effects. Therefore,the explosion protection performance of construction is being more and more concerned[1].The large finite element analysis software ABAQUS is being used to deal with numerical simulation of cross steel frame node, to analyses the response of the steel frame node and to discusses different steel material parameters on the influence of the nodes dynamic response under the effect of Explosive and Impact Load in this paper. According to conclusions, increase strength and modulus of elasticity of steel can reduce the damage of Explosive and Impact Load to construction. Meanwhile taking advantage of the function of transferring information between explicit processor and standard processor in ABAQUS, this paper analyses the effect of Explosive and Impact Load on steel frame node under low cyclic loading and concludes that it is harmful to the structural performance that the effect of Explosive and Impact Load can lower the ductility of the structure. According to the conclusion from the research on steel frame nodes characteristics under the effect of Explosive and Impact Load, this paper present that negative influence of Explosive and Impact Load should be taken fully into account, beneficial materials to explosion protection performance should be choosen and the corresponding measures to improve the ductility of structure should be taken to reduce structures degree of damage under Explosive and Impact Load in future structural design. All the research have a certain significance to the future structural design of explosion protection.

Analysis of the Primary Consolidation Settlement Considering of the Settlement Load

Aiming to improve the calculation result of the total settlement of soft ground of seawall engineering in design, one seawall engineering case is enumerated, and the changes in the thickness of compressible stratum and the primary consolidation settlement are studied by considering the settlement as filling load. The results indicate that the thickness of compressible stratum is increased and the growth of the primary consolidation settlement is about 30% in contrast with the primary consolidation settlement only considering the design load. At last, this paper suggests that a designer should weaken the weight of settlement correction coefficient instead of strengthening the settlement as filling load in future design.

Data Mining on Index of Static Load of Freight Cars

Static load of freight vehicles is one of the important indices to evaluate the efficiency of railway wagon usage, as well an important basis for predicting coefficient of static load in railway line design. Based on sorting out the data structure of static load, clustering algorithm of K-medorids is employed for data mining to find the significant and relatively stable classification characteristics between static load of railway administrations. It is different delivery proportions of heavy goods that are indicated by index factor analysis to cause the static load classification of railway administrations. The data-mining also indicates the differences of static load between different grading railway administrations which cannot be ignored, therefore determining the coefficient of static load in railway design based on divided region is recommended.

Seismic Design Scope of Tower Structures for UHV Transmission Lines on the Zone of Earthquake Fortification Intensity 8

The seismic action effects of tower structures for ultra-high-voltage(UHV, upon 750KV) overhead transmission lines are much greater than those of 500KV and below, it is necessary to inspect the control load in structural design and specify the seismic design scope of tower structures for these UHV transmission lines. In this paper, the current regulations of seismic design and non-seismic design of tower structures for overhead transmission line were contrasted firstly; then, a series of typical towers including large-crossing towers and cup-towers at soft sites, on the zone of earthquake fortification intensity region of 8, were analyzed. The ratios of seismic action effects and wind load effects for characteristic value were calculated and the control load in structural design of tower structure was investigated. The results show that, although the height and the weigth of tower structures for UHV transmission lines are increasing, the control load in structural design is still the wind load on the zone of earthquake fortification intensity region of 8 and below.

Seismic responses of a highway viaduct considering vehicles of design live load as dynamic system during moderate earthquakes

This study is intended to investigate the seismic response of a highway viaduct under vehicle loadings during moderate earthquakes of high probability occurrence. The highway bridge design code of the Japan Road Association (JRA code) does not consider the live load in the seismic design of highway bridges because of the low possibility that both heavy traffic and an earthquake occur at the same time. However, frequent traffic jams in urban areas involve a high possibility of encountering an earthquake during a traffic jam. To clarify the effect of traffic to seismic responses of highway viaducts, heavy vehicles are considered as dynamic system in a three-dimensional dynamic response analysis. The design live load of the JRA code is assumed to be a critical traffic condition for the highway bridges, even during earthquakes. Observations through numerical analyses demonstrate that considering heavy vehicles as a dynamic system reduces seismic responses of the highway viaduct compared with those responses disregarding vehicular loadings and considering vehicles as additional mass.

Preliminary Parametric Assessment of a Bolted Endplate Joint under Combined Axial Force and Cyclic Bending Moment

Problems regarding the combined axial force and bending moment for the behaviour of semi-rigid steel joints under service loading have been recognized in recent studies. As an extended research on the cyclic behaviour of a bolted endplate joint, this study is performed relating to the contribution of column axial force on the cyclic behaviour of the joint. Using finite element analysis, the deteriorations of the joint performance have been evaluated. The preliminary parametric study of the joint is conducted with the consideration of flexibility of the column flange. The column axial force was observed to significantly influence the joint behaviour when the bending of the column flange dominates the failure modes. The reductions of moment resistance predicted by numerical analysis have been compared with codified suggestions. Comments have been made for further consideration of the influence of column axial load in seismic design of bolted endplate joints.

Three-Dimensional Numerical Simulation of Downburst Wind Occurrded in Wuhan

Downburst is a strong downdraft generated below a cumulonimbus cloud, which hits the ground rapidly and causes significant low-level wind shear. It is a strong destructive regional weather phenomenon, which is the main reason for the transmission towers. In recent years, some scholars have researched the finer wind field characteristics and wind load of downburst by using the method of CFD. But the initial conditions are all assumed due to the small synoptic scale, the short lifecycle and the big measurement difficulty of downburst. So downburst wind load can not be taken into account in structural design. Based on the 3-D convective storm numerical model, by inputting temperature, humidity and wind fields detected in Wuhan radiosonde station at 8pm on July,27th,2007, simulation has been accomplished to understand the characteristics of the wind field in the place where the downburst incurred actually. The result provides model data and parameters for CFD simulation, which has directive significance to concern the high intensity downburst wind load in structure design.

Load and Resistance Factors for Progressive Collapse Resistance Design of Reinforced Concrete Building Structures

Due to the absence of provision for the load and resistance factors in design codes in China, designers often quote the provisions which are given in criterion or guidance of other countries such as USA. However, the partial safety factors of the load are various in different criterions. Based on the reliability theory, the load and resistance factors for progressive collapse resistance design of building structures were determined in this study. Firstly the simplified format of design expression in the ultimate state was obtained according to the expression in routine structural design. Then the failure probability of a structure during design reference period was taken as the sum of the probability of all incompatible failure events in this period, and the objective reliability index of the structure could be obtained. Finally using trial-and-error procedure and JC method, reliability analysis was performed for structural members to obtain the partial safety factors of load effects and resistance and the coefficient for combination value of load effects in design expression in the ultimate state. In this paper the load and resistance factors for progressive collapse resistance design of reinforced concrete structures subjected to blast was calculated as an example, and the recommendation values were given for the application at last.

Floor-Beam Web Cutout Shape Analysis to Improve the Fatigue Resistance in Orthotropic Steel Bridge Decks

The modern steel orthotropic decks have been used in steel bridges for 60 years all over the world because of its super structural advantages. Recently, more bridge owners, engineers and researchers pay more attention to the fatigue problem of orthotropic steel decks for a large number of fatigue cracks found in steel bridges. For example, bridge engineers have detected hundreds of fatigue cracks in steel orthotropic deck on the 888-meter long box girder of Humen Bridge only ten years after opening to traffic. How to design or repair the fatigue details in orthotropic steel decks is the critical question to be solved at first step. In current paper, the elaborate numerical analysis model of the orthotropic steel bridge decks was developed using ANSYS software with different floor-beam web cutouts shapes, such as conventional ellipse, circular, trapezoid and Haibach web cutouts. The finite element models were calibrated by static test of one full size orthotropic steel bridge deck model. According to the analysis results, it should select the rational cutout shapes based on actual load and structural conditions in steel bridge deck design and strengthening.

The relation of cognitive load and pupillary unrest

This study examines the relationship between pupillary unrest (PU) and cognitive load. PU represents a measure of reduced central nervous tonic arousal (sleepiness). A loss of tonic arousal can be associated with difficulties in maintaining the required level of performance. Thus, the measurement of tonic arousal in occupational contexts can help to prevent overload or errors. We compared a group with high cognitive load (30 apron controllers of an international airport) with a control group with low cognitive load (63 healthy people during their free time) in a non-randomized experimental design with pre- and post-test assessment of PU. PU was scanned by an infrared sensor with a frequency of 25 Hz and a resolution of .05 mm. To control for circadian effects, measurements for both groups were taken at the same time of the day. High PU at the start of the shift correlated with high perceived load during the shift. There were no indications of reverse effects. Analyses of group x time effects with generalized linear models (repeated measures) revealed that cognitive load did in no way affected PU. Initially low tonic arousal (indicated by high PU) may predict subsequent workload, but being exposed to high cognitive load does not influence tonic arousal after the end of the shift. With that, the study contributes to valid interpretations of pupillary unrest measurements in occupational contexts.

The reaction-time task-rule congruency effect is not affected by working memory load: further support for the activated long-term memory hypothesis

Previous studies claimed that task representation is carried out by the activated long-term memory portion of working memory (WM; Meiran and Kessler in J Exp Psychol Human Percept Perform 34:137-157, 2008). The present study provides a more direct support for this hypothesis. We used the reaction-time task-rule congruency effect (RT-TRCE) in a task-switching setup, and tested the effects of loading WM with irrelevant task rules on RT-TRCE. Experiment 1 manipulated WM load in a between-subject design. WM participants performed a color/shape task switching, while having 0, 1 or 3 numerical task rules as WM load. Experiment 2 used a similar load manipulation (1 or 3 rules to load WM) in a within-subject design. Experiment 3 extended these results by loading WM with perceptual tasks that were more similar to the shape/color tasks. The results show that RT-TRCE was not affected by WM load supporting the activated long-term memory hypothesis.