If a flat slab is found it will either be considered as a restraint, or not, in each direction at each end of the stack - this is controlled by checking the option Use slab for stiffness calculation. If no effective beams are found to restrain the end of the stack in the direction in question, then the program will consider whether there is a flat slab restraining the stack at this end. There is a lower limit 5 for the value of k:Īdditionally, Tekla Structural Designer imposes an upper limit:įor bracing stacks, a warning is displayed when the calculated value of k exceeds this limit. For the stacks beyond the restraint, "E * I" are the values for the stack attached to the restraint, and l is the restrained length that the stack exists within.Īny beams framing into the end of the stack within 45 degrees of the axis being considered are said to be restraining beams for the stack in that direction. Note that as the restrained length may be multiple stacks, "E * I" for this stack are the values for the stack being designed, and l is the restrained length. These stacks can be part of the same column length or another column length. ∑(E * I / l) cols = (E * I / l) stack under consideration + ∑(E * I / l) stacks beyond this joint
∑(E * I / l) cols = (E * I / l) stack under consideration Therefore:ġ.85 ≤ ∑((E *I/ l) stacks beyond this joint) / (E * I/ l) stack under consideration ≤ 1.15 If the stiffness are similar then the stiffness of the adjacent stacks can be ignored, and the guidance in PD6687 suggests that this range of similarity of stiffness can be taken as 15% above or below the stiffness of the stack being designed. If there are any adjacent stacks beyond the joint at the end of the restrained length under consideration, then it must be considered whether these adjacent stacks are likely to contribute to the deflection or restrain it. K = ∑(E * I / l) cols / ∑(2 * E * I / l) beams Also, "E * I / l" is the sum of the stiffness of column stacks joining at the connection. The standard approximation 4 for "θ / M" is between "l / (4 * E * I)" and "l / (3 * E * I)", so to allow for cracking the value is increased. It is recommended to take "θ / M" for the beams as "l / (2 * E * I)". (E * I / l) is the bending stiffness of the compression member or members considered to be buckling. Θ is the rotation of the joint at the end of the stack considered for the bending moment M, M is the moment applied to the restraining members by the buckling member or members, The value of k, which may refer to either k 1 or k 2 depending on which end of the stack is being examined, is defined by 3: The program uses the bottom end of the stack as end 1 and the top end as end 2. Which way the ends are numbered is irrelevant to the result. K 1 and k 2 are the relative flexibilities of rotational restraints at ends 1 and 2 respectively, in the direction under consideration. In addition Tekla Structural Designer imposes the following limits for stacks that are designated as braced:įor stacks designated as "bracing", the effective length is the larger of 2: 5.8.3.2, the equations for calculating the effective length are as follows.įor stacks designated as "braced", the effective length is given by 1: The effective length, l 0 is calculated automatically - you also have the ability to override the calculated value.įrom EC2, cl. Tekla Structural Designer reference Expand.Pile cap design to EC2 (Eurocode) Expand.Pad and strip base design to EC2 (Eurocode) Expand.Concrete slab design to EC2 (Eurocode) Expand.Design parameters for shear (column and wall:EC2).Design for combined axial and bending (column and wall:EC2).Design moment calculations (column and wall:EC2).Column stack and wall panel classification (column and wall:EC2).Effective length calculations (column and wall:EC2).Ultimate axial load limit (column and wall: EC2).Design Parameters for Horizontal Bars (Concrete wall: EC2).Design Parameters for Vertical Bars (Concrete wall: EC2).Cover to Reinforcement (Concrete wall: EC2).Concrete wall design to EC2 (Eurocode) Expand.Concrete column design to EC2 (Eurocode) Expand.Concrete beam design to EC2 (Eurocode) Expand.Concrete design to EC2 (Eurocode) Expand.Steel design to EC3 and EC4 (Eurocode) Expand.Get started with Tekla Structural Designer Expand.
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