Response of timber bridges under train loading

1990 ◽  
Vol 17 (6) ◽  
pp. 940-951 ◽  
Author(s):  
A. S. Uppal ◽  
S. H. Rizkalla ◽  
R. B. Pinkney
Keyword(s):  
Load Factor ◽  
Attractive Alternative ◽  
Dynamic Displacement ◽  
Load Factors ◽  
Vertical Displacements ◽  
Current Design ◽  
Train Speed ◽  
Bridge Spans ◽  
Timber Bridges ◽  
Normal Track

Timber bridges are still commonly used by several North American railroads. For short spans, they offer an attractive alternative to other types of bridges, as they are economical, faster to construct, and easy to maintain. Current design practices do not allow an independent consideration of the effects of the dynamic loads in sizing the bridge components, because very little information is available on the subject. Dynamic tests were carried out at two timber railroad bridge sites under the passage of trains at speeds varying from crawl, i.e., 1.6 km/h (1 mph), to 80.5 km/h (50 mph). The loads at wheel–rail interfaces, the vertical displacements, and the accelerations were measured at several locations on the bridge spans, the bridge approaches, and the normal track sections. The maximum values of the dynamic load factors obtained were 1.50, 1.65, and 1.85 for bridge, bridge approach, and normal track, respectively; and the corresponding maximum values of the dynamic displacement factors obtained were 1.30, 1.00, and 1.20. The main objective of this paper is to describe the experimental work and the influence on the measured values of the train speed and other factors. Key words: railroad, timber, bridge, wheel–rail interfaces, load, deflection, frequency, load factor, dynamic displacement, track modulus.

An analytical approach for dynamic response of timber railroad bridges

1990 ◽  
Vol 17 (6) ◽  
pp. 952-964
Author(s):  
A. S. Uppal ◽  
R. B. Pinkney ◽  
S. H. Rizkalla
Keyword(s):  
Dynamic Response ◽  
Analytical Approach ◽  
The United States ◽  
Constant Speed ◽  
Attractive Alternative ◽  
Railroad Bridges ◽  
Vertical Displacements ◽  
Current Design ◽  
The Subject ◽  
Bridge Spans

In the 1970s, it was reported that there were approximately 3700 track kilometers of timber railroad bridges in the United States and Canada. For short spans, they offer an attractive alternative to other types of bridges, as they are economical, faster to construct, and easy to maintain. Current design practices do not allow an independent consideration of the effects of the dynamic loads in sizing the bridge components, because very little information is available on the subject. Dynamic tests were carried out in 1986 on timber bridge spans at two test sites using test trains consisting of a locomotive unit, two loaded hopper cars, and a caboose. This paper gives a brief description of the analytical approach employed for determining the dynamic response of timber bridge spans under railway vehicles travelling at a constant speed. The model comprises a multi-degree-of-freedom system with each vehicle having bounce, pitch, and roll movements. Two parallel chords, each having its distributed mass lumped at discrete points, were used to idealize the bridge spans. A computer program developed on this basis was used to predict the loads at the wheel–rail interfaces and the vertical displacements at the discrete points on the spans. The predicted loads at wheel–rail interfaces and the maximum vertical displacements were found to be in agreement within about 20% and 16% respectively of the measured values. The program was utilized to study the effect of speed and other factors on the dynamic response of open-deck and ballast-deck bridges. Key words: analytical approach, timber railway bridge, railway locomotive and cars, constant speed, wheel–rail interface, loads, displacements, accelerations, dynamic response.

Effect of guy initial tension on design of guyed antenna towers

1996 ◽  
Vol 23 (2) ◽  
pp. 457-463
Author(s):  
Yohanna M. F. Wahba ◽  
Murty K. S. Madugula ◽  
Gerard R. Monforton
Keyword(s):  
Load Factor ◽  
Case Scenario ◽  
Limit States ◽  
Initial Tension ◽  
Worst Case ◽  
Design Procedures ◽  
Design Engineers ◽  
Load Factors ◽  
Current Design ◽  
Guyed Towers

This study examines the effect of changing the initial guy tension on the design of guyed antenna towers. Six different guyed towers with various heights and loading conditions are used in this study, in which initial guy tensions are changed and the corresponding effect on the forces in the tower components are examined. Also, the methods used in measuring the initial tension are reviewed. On the basis of this study, it is proposed that the initial guy tensions have a load factor different from the value of 1.0 suggested in CSA S37-94. Two additional load combinations are developed from this analysis in order to assist design engineers in determining the worst case scenario for the variation of initial tension in the guys. Results are compared for designs using the current design procedures and the design using the proposed load factors for initial tensions in guy wires. Key words: antenna towers, guyed towers, limit states design, guys, initial tension.

scholarly journals Numerical and experimental study of the dynamic factor of the dynamic load on the urban railway

2020 ◽  
Vol 29 (1) ◽  
pp. 195-202
Author(s):  
Tran Anh Dung ◽  
Mai Van Tham ◽  
Do Xuan Quy ◽  
Tran The Truyen ◽  
Pham Van Ky ◽  
...  
Keyword(s):  
Experimental Study ◽  
Dynamic Load ◽  
Dynamic Measurement ◽  
Experimental Results ◽  
Load Factor ◽  
Dynamic Factor ◽  
Experimental Measurements ◽  
Train Speed ◽  
Dynamic Load Factor

AbstractThis paper presents simulation calculations and experimental measurements to determine the dynamic load factor (DLF) of train on the urban railway in Vietnam. Simulation calculations are performed by SIMPACK software. Dynamic measurement experiments were conducted on Cat Linh – Ha Dong line. The simulation and experimental results provide the DLF values with the largest difference of 2.46% when the train speed varies from 0 km/h to 80 km/h

Analysis of Robin Hood and Other Hashing Algorithms Under the Random Probing Model, With and Without Deletions

2018 ◽  
Vol 28 (4) ◽  
pp. 600-617
Author(s):  
P. V. POBLETE ◽  
A. VIOLA
Keyword(s):  
Search Algorithm ◽  
Recurrence Equation ◽  
Constant Time ◽  
Collision Resolution ◽  
Load Factor ◽  
Hash Tables ◽  
Search Cost ◽  
Robin Hood ◽  
Small Constant ◽  
Load Factors

Thirty years ago, the Robin Hood collision resolution strategy was introduced for open addressing hash tables, and a recurrence equation was found for the distribution of its search cost. Although this recurrence could not be solved analytically, it allowed for numerical computations that, remarkably, suggested that the variance of the search cost approached a value of 1.883 when the table was full. Furthermore, by using a non-standard mean-centred search algorithm, this would imply that searches could be performed in expected constant time even in a full table.In spite of the time elapsed since these observations were made, no progress has been made in proving them. In this paper we introduce a technique to work around the intractability of the recurrence equation by solving instead an associated differential equation. While this does not provide an exact solution, it is sufficiently powerful to prove a bound of π2/3 for the variance, and thus obtain a proof that the variance of Robin Hood is bounded by a small constant for load factors arbitrarily close to 1. As a corollary, this proves that the mean-centred search algorithm runs in expected constant time.We also use this technique to study the performance of Robin Hood hash tables under a long sequence of insertions and deletions, where deletions are implemented by marking elements as deleted. We prove that, in this case, the variance is bounded by 1/(1−α), where α is the load factor.To model the behaviour of these hash tables, we use a unified approach that we apply also to study the First-Come-First-Served and Last-Come-First-Served collision resolution disciplines, both with and without deletions.

scholarly journals A Measure of Capacity Contribution of Static Mono-Si Photovoltaic Systems

2013 ◽  
Vol 2013 ◽  
pp. 1-6
Author(s):  
Constantinos Varnavas ◽  
Andreas Poullikkas
Keyword(s):  
Load Capacity ◽  
Load Factor ◽  
Photovoltaic Systems ◽  
High Demand ◽  
Pv System ◽  
Pv Systems ◽  
Mediterranean Countries ◽  
Load Factors ◽  
High System ◽  
Installed Capacity

Photovoltaic (PV) systems generate electricity in the daytime when system demand is generally moderate to high. For Mediterranean countries, there is also seasonal coincidence of high system demand and high PV load factors. The present study quantifies the above statements by calculating the load factor of the PV system when system demand is high (above 90–99% of the maximum demand of the month). The percentage of time the PV load factor is above 90% for these periods of maximum demand is evaluated. The PV load capacity contribution is defined in this study as the minimum PV load factor during these periods of high demand. Actual generation data from a static (without tracking) mono-Si PV system, recorded every half hour for the year 2010 are compared to system demand data. The seasonality analysis indicates that PV contribution to capacity is only significant during the months May–October. For the months November–April, when daily demand peak occurs during the evening, PVs do not contribute towards capacity. The evaluated capacity contribution of PV systems depends on the threshold of maximum demand considered (90%–99%). For the threshold of 95%, the capacity contribution for May–October ranges between 27%–41% of PV installed capacity.

Aircraft Configuration Improvement Study from Aerodynamic and Structure Standpoints

2015 ◽  
Vol 798 ◽  
pp. 565-570
Author(s):  
Luciano Magno Fragola Barbosa ◽  
Ricardo Luiz Utsch de Freitas Pinto ◽  
Bernardo Oliveira Hargreaves
Keyword(s):  
Finite Element ◽  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Load Distribution ◽  
Structural Deformation ◽  
Load Factor ◽  
Aircraft Wing ◽  
Induced Drag ◽  
Vertical Displacements ◽  
Lifting Line

In this work improvements on the geometry of a high aspect ratio aircraft wing are studied, in order to reduce the wing in-flight deformation, without changing the drag of the aircraft and without increasing the structural weight. For this, from a reference rectangular wing, one new wing with elliptical planform has been defined; and comparative analyses of loads and structural deformation have been made for the wings considered: the original rectangular wing and the new corresponding elliptical wing. The aerodynamic analysis is based on the lifting line approach. A computer routine is made by the authors based on this approach, to obtain both induced drag values and the load distribution of the two wings, the original one and the corresponding elliptical. Based on the loads, spars for the two wings have been defined, and in order to evaluate the vertical displacements in flight, a finite element routine have been used. The main result of this study is the comparison of the deformation of wings considered, subjected to the same load factor, and for the same aircraft mass. The results obtained are encouraging for further developments using the present methodology.

Parametric Instability of Tapered Beams by Finite Element Method

1982 ◽  
Vol 24 (4) ◽  
pp. 205-208 ◽  
Author(s):  
P. K. Datta ◽  
S. Chakraborty
Keyword(s):  
Finite Element ◽  
Dynamic Load ◽  
Parametric Instability ◽  
Mathieu Equation ◽  
Stability Diagram ◽  
Load Factor ◽  
Element Analysis ◽  
Load Factors ◽  
Principal Region ◽  
Dynamic Load Factor

The dynamic stability behaviour of a tapered beam has been studied using a finite element analysis. The instability zones of the parametric stability diagram have been discussed for the entire ranges of static and dynamic load factors. It has been observed that at high values of static load and beyond a particular value of the dynamic load factor, the periodic solution of the Mathieu equation does not exist in the principal region. This leads to unstable behaviour due to large displacement of the beam due to increasing values of static and dynamic load factors.

Bolt Load Changes Due to Internal Pressure in Gasketed Flange Connections

2003 ◽  
Author(s):  
Satoshi Nagata ◽  
Mitsuhiro Matsumoto ◽  
Toshiyuki Sawa
Keyword(s):  
Internal Pressure ◽  
Thrust Force ◽  
High Reliability ◽  
Constant Load ◽  
Point Of View ◽  
Load Factor ◽  
Test Results ◽  
Performance Point ◽  
Load Factors ◽  
Sealing Performance

Bolt load changes due to internal pressure are very important in order to evaluate the integrity of gasketed flange connections in the sealing performance point of view, because its gasket stress which dominates leak rate changes according to the bolt load changes. For establishing a connection possesses high reliability and sufficient integrity, it is necessary to clarify the mechanics ofgasketed flange connections. For this purpose, authors carried out experimental pressurizing tests for 3B and 20B gasketed flange connections clamped by various bolt preloads and measured the bolt load changes with increasing internal pressure up to 5MPa. Also a load factor, which is defined as the ratio of axial bolt force increment to pressure thrust force, was calculated using the test results. The test results indicate that 3B and 20B flange connections with the spiral wound gaskets have a constant load factors under sufficient initial clamping forces in assemble.

Static aeroelastic optimisation to wing structural weight estimation of an extremely manoeuvrable UAV

2015 ◽  
Vol 119 (1218) ◽  
pp. 1033-1043
Author(s):  
L. Yi ◽  
Y. Jun ◽  
K. Bin
Keyword(s):  
Conceptual Design ◽  
Element Model ◽  
Empirical Method ◽  
Structure Design ◽  
Load Factor ◽  
Load Factors ◽  
Aerial Vehicle ◽  
Wing Structure ◽  
Aircraft Conceptual Design ◽  
The Finite Element Model

Abstract Estimating the wing structural weight of an extremely manoeuvrable Unmanned Aerial Vehicle (UAV) during conceptual design has proven to be a significant challenge due to its high load factor (the ratio of an aircraft lift to its weight). The traditional empirical method relies on existing statistical data of previously built aircraft, then is inadequate for the innovative UAV structure design which can endure extremely manoeuvrable load (load factor is greater than 9g). In this paper, the finite element model for wing structure of an extremely manoeuvrable UAV with foreplane was built, and the structural weight was estimated by static aeroelastic optimisation considering structural strength and buckling constraints. The methodology developed here is only consisted of three components, which is much less than that for existing method, thus the procedure developed here sacrificed some accuracy, but it’s faster and more suitable for aircraft conceptual design. It was validated by the overlap between the weights given by the methodology, and the results from empirical equations when the load factors are less than 9g. Through the analysis procedure developed, the wing structural weights of the extremely manoeuvrable UAV were given under different load cases (load factor changes from 5g to 12g).

Comparison of Recent Parametric Trenched and Partially Embedded/ Spanning Pipelines With DNV-RP-F109 Load Reduction Design Curves

2012 ◽  
Author(s):  
Terry Griffiths ◽  
Wenwen Shen ◽  
Mengmeng Xu ◽  
Jeremy Leggoe
Keyword(s):  
Stability Analysis ◽  
Dynamic Stability ◽  
Reduction Factor ◽  
Load Factor ◽  
Load Reduction ◽  
Load Factors ◽  
Time Histories ◽  
Force Time ◽  
Cfd Analyses ◽  
Reduction Factors

An extensive series of 2D CFD analyses of subsea pipelines with parametrically varying seabed profiles have been performed in the past two years. These cases feature variations on wave and current flow conditions with pipeline partial embedment or spanning which extend beyond the range of conditions which have been published to date. This paper presents a comparison of the reduction factors calculated from this work with DNV-RP-F109 load factors and previous published research. At present, the DNV-RP-F109 partial embedment / trenched pipeline load reduction factors are applied in both absolute stability analysis and also as a reduction factor on hydrodynamic force-time histories used in dynamic stability analysis. The suitability of this load factor reduction for dynamic stability analysis will also be considered. In addition, a limited number of cases have been constructed in 3D which provide some initial insights into the variation of hydrodynamic loads across a pipeline span as a function of finite span length, enabling the validity of applying the 2D DNV load reduction factors across a 3D span to be considered. The 3D cases also consider inclined attack angles, and the effect they have on hydrodynamic forces across a span.

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