The Vietnamese standard for steel structural design has only two types of connections between components: rigid (mounted) – with moment or pin – not supporting from the moment in the connection. However, the actual calculation and structure of steel structure have many cases that cannot be clearly delineated, a connection, which is a mount or a complete pin. The standard Eurocode 3 steel structure design standard is a pretty good reference base to assess the connection hardness, which is not completely rigid or absolutely rigid, but has an intermediate level. This is very useful in some cases that need to model the connection hardness to check the internal force distribution in the steel frame compared to the original assumption when the structural model is rigid or absolute pin. This article presents how to calculate the steel -steel bonding hardness (base plan) according to Eurocode 3 standards and applied into a spreadsheet to facilitate the construction design.
Structure model of steel pole bonding
Basic column bonds include baseplate and bolts, compressed with $z_ {tl}, z_ {cr} $. The internal force calculated at the column leg due to the bonding is the vertical force of compressed $n_ {SD} $ and the bending moment $M_ {SD} $.
The initial elastic hardness when rotating the base of the column of the column is defined by the formula:
$$s_{j.ini}=\frac{M_{sd}}{\phi}$$
$\Phi $: The rotating angle of the base when bearing the moment:
$$\phi=\frac{\delta_{t,l}+\delta_{c,r}}{z}=\frac{1}{Ez^2}\left(\frac{M_{sd}+N_{sd}z_{c,r}}{k_{t,l}}+\frac{M_{sd}-N_{sd}z_{t,l}}{k_{c,r}}\right)$$
$E $: elastic module of steel
$k_b $: The hardness coefficient of the bolt according to the composition method, defined by:
$$k_b=\frac{F}{E\delta_b}=2\frac{A_s}{L_b}$$
$A_S $: The full section area of the anchor bolt
$L_b $: The length of the anchor bolt
According to Eurocode 3, if $30\frac {ei_c} {l_c}$, the connection is considered rigid (mounted) completely.
$I_C $: Moment inertia of the steel column section
$L_c $: column length
In contrast, the connection is Semi-rigid with anti-rotating hardness with $s_ {J.ini} $. If $30\frac {EI_C} {l_c} $ is very large compared to $s_ {J.ini} $, linked is considered joint Structural design.
Refer to the hardness calculation table in the link here
