AxisVM Capacity Calculation - McR

cadsoft

This is about how to prevent shear failure of columns and beams in case of dissipative structures in RC2 module.  

As a first step it´s recommended to read related parts of the User manual, which contains a detailed description of the topic. Depend how deeply users know AXISVM, so I tried to summarise the main steps briefly. If there are further questions, insert your comments and we will try to answer with more details.

In case of dissipative structures with DCM or DCH ductility class, in order to avoid shear failure in RC columns, beams and ribs, the design values of shear forces are determined in accordance with the capacity design rule (if seismic load case is included in the selected load combination). Capacity design is only available if the q behaviour factor is greater than 1.50.

Main steps:

1. Vibration analysis (User manual: 5.2 Vibration)

A first step is therefore to carry out a vibration analysis to determine the mode shapes needed to define the seismic loading case.

1. Create a seismic load case (SE1 module):

 After having the mode shapes available, the seismic load case shall be created at the Loads tab in the Load Cases and Load Groups dialog window.

1. Setting seismic load parameters (User manual: 4.10.25 Seismic loads – SE1 module)

 On the Seismic load dialog window, parameters can be specified, including the behaviour factor.

Program will generate the critical load combinations in the background, so it is not needed to create manually the load combinations.  

1. Perform linear static analysis

1. RC2 – Reinforced concrete column or beam design

Column reinforcement design (User manual: 6.5.4)

In case of dissipative structures with DCM or DCH ductility class (EN 1998-1-1), the design values of shear forces are determined in accordance with the capacity design rule (if seismic load case is included in the selected load combination), on the basis of the equilibrium of the column under end moments Mi,d (with i=1,2 denoting the end sections of the column), corresponding to plastic hinge formation for positive and negative directions of seismic loading.

The following parameters can be specified by the user: the safety factor, the ductility class, the clear length of the column (clear length: the distance between end sections where plastic hinges can be formed) and the ratio between the sum of moment capacity of beams and columns connected to the same joint respectively.

Background and description of the capacity design in accordance with the specifications of standard EN 1998-1-1 (Chapter 5.4.2.3 ; Equation 5.9) can be found in the User manual in the chapter 6.5.9.7:

Beam reinforcement design -Check of shear forces calculated from plastic hinges (User manual: 6.5.12.1)

In the capacity design drop-down menu choose the option “Antiseismic beams”

Choose plastic hinges icon, in the beam reinforcement design window

In case of dissipative structures with DCM or DCH ductility class (EN 1998-1-1), in order to avoid shear failure of beams, the design values of shear forces are determined in accordance with the capacity design rule (if seismic load case is included in the selected load combination), on the basis of the equilibrium of the beam under: a) the transverse load acting on it in the seismic design situation and b) end moments Mi,d (with i=1,2 denoting the end sections of the beam), corresponding to plastic hinge formation for positive and negative directions of seismic loading.

 The following parameters can be given by the user: the safety factor, the distance between plastic hinges and the reinforcement of plastic hinges. If Actual reinforcement checkbox is checked, the reinforcement parameters related to plastic hinges are calculated automatically based on the defined actual beam reinforcement. The length below the plastic hinges in the window is the length of critical region where the program considers stricter requirements regarding detailing rules of shear reinforcement in order achieve the expected ductility.