Proceedings of the International rilem conference Materials, Systems and Structures in Civil Engineering 2016

136

International RILEM Conference on Materials, Systems and Structures in Civil Engineering 

Conference segment on Service Life of Cement-Based Materials and Structures 

22-24 August 2016, Technical University of Denmark, Lyngby, Denmark 

 

Ballast & 

Subgrade 

Sleeper 

Rail 

Pad 

a rail [4].  The magnitude of the dynamic impact loads per railseat is varying from 200 kN to 

sometimes more than 750 kN, whilst the design static wheel load per railseat for a 40-tone 

axle load could be only as much as 110 kN [5-6]. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 1: Illustration of typical railway track system and its components (generally sleepers 

are embedded in ballast) 

 

All static, quasi-static, and impact loads are very important in design and analysis of railway 

track and its components. The typical dynamic load imposed by running wagons can be 

treated as a quasi-static load when no irregularity exists. However, when the irregularity 

appears, dynamic shock loading corresponds to the frequency range from 0 to 2000 Hz due to 

modern track vehicles passing at any generic operational speed [7-8]. The shape of impact 

loading varies depending on various possible sources of such loading, e.g. wheel flats, out-of-

round wheels, wheel corrugation, short and long wavelength rail corrugation, dipped welds 

and joints, pitting, and shelling. Wheel/rail irregularities induce high dynamic impact forces 

along the rails that may greatly exceed the static wheel load. In all cases, the impact forces are 

significantly dependent on the train speed. These impulses would occur repetitively during the 

roll. Loss of contact between wheel/rail, so-called “wheel fly”, will occur if the irregularity is 

large enough, or the speed is fast enough. However, the impact force could be simplified as a 

shock pulse applied right after when the static wheel load is removed during the loss of 

contact [8]. The typical magnitude of impact loads depends on the causes and the traveling 

speed of train. The durations of such loads are quite similar, varying between 1 and 10 msec. 

However, the representative values of the first peak (P

1

) of the forces caused by dipped joints 

should be about 400 kN magnitude with 1 to 5 msec time duration. For the second peak (P

2

), 

the average values are about 80 kN magnitude and 5 to 12 msec time duration. The effect of 

impact forces depends on the duration. It was found that the longer the duration, the 

significance the effect [4]. Therefore, it should be taken into account that the typical duration 

of impact wheel forces varies widely between 1 and 12 msec [4, 9, 10].  

A recent study showed that it is highly likely that railway sleepers could be frequently 

subjected to severe impact loads [11]. In general, the dynamic load characteristics considered 

in design and analysis include the magnitudes of impact loading and the variety of pulse 

durations.  In general, although the loading and strain rate effects may increase the strength of 

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137

International RILEM Conference on Materials, Systems and Structures in Civil Engineering 

Conference segment on Service Life of Cement-Based Materials and Structures 

22-24 August 2016, Technical University of Denmark, Lyngby, Denmark 

 

materials, the high loading magnitude could devastate the structural members. In structural 

design and analysis, the public safety must not be compromised so the design loads must be 

appropriate and associated with the long return periods, which would optimally provide the 

low probability of occurrence on structures during their design life. For further explanation, a 

design load that is associated with 50 year return period has the likelihood of occurrence that 

the design load might happen only once in 50 years regardless of the structural life span. 

Wheel load is an important factor in design and analysis of railway track and its components. 

The design load (F*) for the limit states design concept takes into account both the static (F

s

) 

and dynamic (F

i

) wheel loads. There are three main steps in designing the concrete sleepers. 

First, the design actions or loads are to be determined based on the importance level of the 

track (e.g. F*  = 1.2  F

s

 + 1.5  F

i

). Then, the design shear and moment envelopes can be 

achieved by converting the design load to sleeper responses using advanced railtrack dynamic 

analysis or the design formulation [12]. Last, the strength and serviceability of the prestressed 

concrete sleepers can be optimized in accordance with AS3600 Concrete structures (Standards 

Australia, 2012). An initially proposed limit states design methodology and procedure can be 

found in details in Remennikov et al. [13]. 

 

 

 

 

 

 

 

 

 

 

Figure 2: Example of statistical data of actual track loading [15] 

Leong [15] showed the statistical data of wheel loading obtained from railway networks in 

Queensland, Australia. Using probabilistic analysis, the possibility of occurrence related to 

the magnitude of impact loading on railway sleepers can be predicted. Figure 2 shows a 

statistical data of actual wheel loading applied on top of the rail obtained from a railway 

network in North Queensland [15-16]. From Figure 2, the relationships between the impact 

forces I (kN) and the return periods R (year) can be written as follows: 

 

1

.

4

010

.

0

10

1

I

R

  

  

 

        (1) 

Impact force, kN 

Number of 

axles 

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