1.  AFHTech RC overview

RC is provided free of charge on the AFHTech Internet Platform.

RC is also provided on the AFHTech PocketPC Platform.

AFHTech Internet Platform main objective is to provide and keep Online Applications free of charge for all users in the world based on Internet Technology. To know more about AFHTech.com, go to www.afhtech.com.

AFHTech RC Software allows users to design and check Reinforced Concrete columns and beams.

RC is designed in order to provide civil engineering and civil engineers with simple, fast and anywhere usable technology.

Two kinds of analysis can be made with RC: ultimate resistance state and serviceability state analysis.

In ultimate state analysis RC provides:

·         Complete resistance’s surface calculated from full integration over the reinforced concrete section. Resistance’s surface can be view on N-M and Mx-MY diagram.

·         Checks of design efforts under the previous resistance’s surface. Checks can be made by visual comparison of design efforts over N-M diagram, by checking the ratio Efforts/Resistance provided by RC   or by checking the minimum reinforced area that satisfies design values. Note: Efforts/Resistance coefficient is considered to be the inverse of the Safety Factor given by Design Resistance/Design Efforts

·         The ultimate analyses provided by RC are made considering biaxial bending with axial force and that all second order effects are already included in design efforts. Beam design and check can be made by considering N=0.

In serviceability state analysis RC provides:

·         Service stresses in concrete and steel bars under cracked state subjected to user defined service efforts. Stresses can be useful to many serviceability design checks including crack width control.

2. Links to AFHTech RC Software

If you want to reach AFHTech web site go to www.afhtech.com

RC is provided free of charge on the AFHTech Internet Platform.

To reach AfhTech RC software follow this link.

RC is also provided on the AFHTech PocketPC Platform, reachable at this link.

3. Units

RC units are not explicit.

You can choose the units that best suit your interests, knowing that units must be consistence over all data.

Since concrete area and steel bar area can have a large scale displacement, RC allows you to define a Steel Unit Factor that convert Steel Bar Area Units into Global Area Units.

RC default values are in SI units, as follows:

        Force: kN

        Moment: kNm

        Length: m

        Area: m²

        Steel Bar Area: cm²              Steel Unit Factor = 0.0001  (1 cm² = 0.0001 m²)

4. Materials

RC uses two materials: concrete and steel bars.

4.1. Concrete

Concrete is the base material of concrete columns and beams.

In RC concrete is defined as stated in Eurocode2 (EN 1992-1-1:2004 – «Eurocode 2: Design of concrete structures, part 1-1: general rules and rules for buildings»).

If you want to check a column or beam with another code, please be free to try RC formula first. If you found significant differences please inform us to webmaster@afhtech.com, attaching your formulas, the reference of your code and the results you achieved. We’ll be pleased to upgrade our software for better serve your interests.

Below, eurocode 2 is called EC2.

In RC, concrete and steel don’t overlap: Concrete Area = Gross Area – Steel Area.

4.1.1. Compression resistance

Compression resistance is defined with two variables:

         that represents the design compression resistance for ultimate limit sate analysis.

         that represents the mean compression resistance for service limit sate analysis.

4.1.2. Tension resistance

RC considers that concrete is cracked under tension. As so, concrete can’t provide tension stresses, both in ultimate and service limit states.

RC doesn’t take into account tension-stiffening effects.

4.1.3. Secant Modulus of Elasticity

Ecm represents the mean secant modulus of elasticity needed for stress-strain definition in service analysis (see below).

4.1.4. Stress-strain relationship

EC2 defines concrete stress-strain relationship for both ultimate and service analysis.

For ultimate analysis, RC adopts the following formulas, with positive signs for compression:

For compression:                           ( 

                                                                                                             (         

For tension:                      

Maximum compression strain:

Maximum strain under uniform compression:

For service analysis, RC adopts the EC2 formula for non-linear analysis, with positive signs for compression:

For compression:                                                              (

For tension:                      

4.1.5. Concrete wizard

For your comfort, RC provides you with a concrete wizard.

You only need to choose the concrete resistance class and RC fills all concrete data for you.

RC concrete wizard knows the following EC2 categories:

C12/15, C16/20, C20/25, C25/30, C30/37, C35/45, C40/50, C45/55, C50/60

When defining concrete with concrete wizard, RC takes fcd = acc x fck/1.5.

4.2. Steel

RC adopts a bilinear stress-strain relationship to steel behavior both at ultimate and service limit states.

RC nomenclature:

Es            modulus of elasticity, needed for both ultimate and service analysis

f_yk           characteristic yield stress, needed for service analysis

f_yd           design yield stress, needed for ultimate limit state analysis, is given by the coefficient between the characteristic yield stress and the adopted partial safety factor

5. Sign and geometry convention

In all inputs and outputs RC adopts the following sign convention:

Moments: right hand convention about the relevant axis.

Axial efforts: positive for tension, negative for compression

Strains: positive for tension, negative for compression

Curvatures: right hand convention about the relevant axis.                                               

The axis convention follows the usual beam principle: Mx positive moment imposes compression in section’s upper part and tension in the down part. As so, YY axis points downward and XX axis points towards left.

Cover+D/2 defines the distance between concrete surface and steel bar center.

Angle at Resistance Surface and Check Resistance tabs is given by the angle between the XX plane and the point considered. The angle’s center lies over the line segment that connects Nmax and Nmin. In sections with symmetry, the angle’s center lies over the ZZ axis. The angle is measured in a plane perpendicular to ZZ axis.

6. Number convention and expressions

On Internet Platform, RC input boxes use JavaScript convention (only if JavaScript is enabled):

Numbers started with 0 (zero) are considered in octal base (ex: 010 = 8; 0100=64)

Numbers started with 0x are considered in hexadecimal base (ex: 010 = 16; 0x100=254; 0xFA=250)

Simple expressions are evaluated before processing (ex: 1+4=5; 10/4=2.5)

7. Additional questions, suggestions and bug reports

If you have questions not responded in this page, suggestions you want to make in order to improve RC software or if you think you have found a bug please feel free to contact us by sending an e-mail to webmaster@afhtech.com. We will be glad to answer you as soon as possible.

If you want to suggest the development of a specific software application, feel free to send an e-mail to webmaster@afhtech.com.

We want AFHTech web site to serve civil engineering community the best as possible.