Bridge design in SCIA Engineer

New material classes are introduced in this project according to EN1992-2. The performed checks are based on the chosen type of material. For example: if C35/45 (EN 1992-2) is used, then checks are done according to the concrete code for bridges. The following classes will be introduced:

• C30/37(EN 1992-2)
• C35/45(EN 1992-2)
• C40/50(EN 1992-2)
• C45/55(EN 1992-2)
• C50/60(EN 1992-2)

Time dependent analysis according to EN 1992-2 annex B is provided only for concrete with strength fck ≥55MPa (C55/67 and higher). For the concrete classes with fck <55MPa even if these are assigned as EN1992-2, TDA will be done using EN1992-1-1 annex B.

Next to this, also EN1992-2 requires the input of Nationally Determined Parameters. As an answer to this, numerous National Annexes to EN1992-2. 

To evaluate the design strength of construction elements with the new concrete grades, a check is performed on minimal and maximal characteristic cylinder strength. A message will appear when the characteristic cylinder strength is exceeded. This message appears in the following checks:

• Design As
• Design of nonprestressed reinforcement tin prestress members
• Check response
• Prestress check response

Another performed check is the check on reinforcement class for adequate ductility. According to article 3.2.4(101) the recommended classes of non-prestressed reinforcement for concrete bridges are B and C. If class A is used, following message appears: "The used non-prestressed reinforcement is not allowed due to low ductility." The warning appears in the following services:

• Design As
• Design of nonprestressed reinforcement tin prestress members
• Crack width
• Check response
• Detailing provisions
• Check capacity
• Prestress crack width
• Prestress check response
• Prestress check capacity

To calculate the ratio of the redistributed moment to the elastic bending moment, the formula for the redistribution of the bending moments has been implemented according to clause 5.5.4 (104) of EN 1992-2.

For a crack check, it's important to know the maximum crack width for each exposure class. These values are integrated in SCIA Engineer according to clause 7.3.1(105). It is applied for the crack check of 1D members, ULS+SLS design of 2D members and crack check of 2D members.

The decompression distance of prestressed concrete is now also checked for bridge design according to clause 7.3.1(105): i.e. the required perpendicular distance from the edge of the prestressing strand or duct to the neutral axis where the concrete has to be in compression.

Under the detailing provisions, a check of the minimal diameter of transversal reinforcement for columns has been added according to clause 9.5.3(101).

When a concrete surface is subjected to abrasion caused by ice or solid transportation in running water the cover should be increased by a 10mm. A new option has been added to the Design defaults in the concrete service. Delta_cabr: value of deviation for the concrete cover for members exposed to abrasion by ice or solid transportation in running water

Related to this a new item is inserted in the Concrete 1D member data, called Abrasion deviation.

When the checkbox above is activated, then the minimal calculated cover is increased by the value set in Design defaults:

When a member consists of a material from EN 1992-2 then the global imperfection is calculated in a different way than for a standard EN 1992-1-1 material.

The factor alfa_m is not considered in the formula for theta_i and the factor alfa_h has no lower limit:

The factor theta_i is used in the for the calculation of recalculated internal forces:

When a member consists of a concrete material from EN1992-2 then the adequate rotation capacity for plastic analysis is achieved if the depth of compression zone is restricted to the depth as follows:

This is applied when checking the calculated redistributed bending moment My (around y axis of LCS of the member) by using method 5.6.2.

The bonded prestressing reinforcement in the tensile zone of concrete can be taken into account for the calculation of shear check too according to 6.2.2(1)(101). Currently the prestressing reinforcement is not taken into account for calculation of d. Value Asl is needed for calculation of rho_l.

Shear check according to formula 6.2.

A new factor is implemented to take into account the maximum compressive stress during execution for a quasi-permanent combination. This is according to EN 1992-2, clause 113.3.2(103).

It's available in the National Annex setup manager under Concrete > SLS > Stress limitation.

By default this factor k = 1.

It is applied for the calculation of the allowable concrete stresses. The verification is only done for members where a decompression check is required.

For members where the decompression should be checked (quasi-perm or frequent combination) the allowable stress has to be less than k*fctm(t) for a combination (quasi-perm) from construction stages (k=1,0). This verification is only done for:

• Combinations generated from construction stages (it means stages which are before or a stage marked as Last construction stage)
• Quasi-permanent combination

The procedure is the following:

1) A new value is introduced in the service Allowable concrete stresses - sigma_c,ex – allowable stresses in concrete during execution

2) The comparative values are sigma_clt,max

3) The check value is calculated

This value appears only if :

1) Concrete extension check is activated in the functionality

2) Type of model is set to Construction stages