Ans: It depends on the friction factor input in the dialog of the saddles between the sliding saddles and the concrete or the plate under the sliding saddles.

A small friction factor value indicates that a PTFE plate or in some cases rolling bars have been installed.

The values of the longitudinal loads (RaHL) are calculated as follow:

No.	Support saddles Location (mm) Stiffness (daN/mm)	Vertical			Horizontal				Combined
		Reactions (daN)	Shear Loads (daN)	Bending moments (daN∙m)	Reactions Transverse (daN)	Shear Loads (daN)	Bending moments (daN∙m)	Reactions Longitudinal (daN)	Reactions (daN)	Shear Loads (daN)	Bending moments (daN∙m)
1	500.0	2,716.2	-324.1 2,392.2	-144.2 -2,424.7	0.0	0.0	0.0	2,402.7	2,716.2	-324.1 2,392.2	-144.2 -2,424.7
2	4,500.0	4,190.7	-1,623.1 2,567.7	-2,245.8 -697.1	0.0	0.0	0.0	-1,629.2	4,190.7	-1,623.1 2,567.7	-2,245.8 -697.1
3	8,500.0	2,057.6	-1,433.9 623.8	-1,134.0 -744.0	0.0	0.0	0.0	-521.1	2,057.6	-1,433.9 623.8	-1,134.0 -744.0
4	11,500.0	673.9	-349.8 324.1	-333.5 -144.2	0.0	0.0	0.0	-252.4	673.9	-349.8 324.1	-333.5 -144.2

The fixed saddle is located in this example on the left hand.

 How are the RaHL values calculated? Run the model with a friction factor equal to 0 and you will obtain the values of vertical reaction loads used for the calculation of RaHL (as shown here after):

No.	Support saddles Location (mm) Stiffness (daN/mm)	Vertical			Horizontal				Combined
		Reactions (daN)	Shear Loads (daN)	Bending moments (daN∙m)	Reactions Transverse (daN)	Shear Loads (daN)	Bending moments (daN∙m)	Reactions Longitudinal (daN)	Reactions (daN)	Shear Loads (daN)	Bending moments (daN∙m)
1	500.0	2,162.0	-324.1 1,837.9	-144.5	0.0	0.0	0.0	0.0	2,162.0	-324.1 1,837.9	-144.5
2	4,500.0	5,253.1	-2,177.3 3,075.8	-2,181.7	0.0	0.0	0.0	0.0	5,253.1	-2,177.3 3,075.8	-2,181.7
3	8,500.0	1,559.4	-925.8 633.7	-585.1	0.0	0.0	0.0	0.0	1,559.4	-925.8 633.7	-585.1
4	11,500.0	664.0	-339.9 324.1	-144.5	0.0	0.0	0.0	0.0	664.0	-339.9 324.1	-144.5

In this example, the mass of the each saddle is 181 kg (177.4 daN).

The friction factor is equal to 0.3

The loads on the sliding saddles are equal to:

W2ini = 5253.1 + 177.4 = 5430.5 daN                  RaHL2 = 5430.5 x 0.3 = 1629.2 daN

W3ini = 1559.4 + 177.4 = 1736.8 daN                 RaHL3 = 1736.8 x 0.3 = 521.1 daN

W4ini = 664 + 177.4 = 841.4 daN                         RaHL4 = 841.4 x 0.3 = 252.4 daN

The sign is – for these loads.

 The system is on equilibrium è S RaHL = 0

The load on the fixed saddle is equal to:  RaHL1 = 1629.2 + 521.1 + 252.4 = 2402.7 daN

When the longitudinal loads exist, the vertical loads are modified.

These modified values are due to the moments