Transfer of forces through the structure

 

We introduce some demands for the statical way of behavior of the components.

 

Slab function - the ability to transfer loads perpendicular to the plan of the component.

 

 

Wall function – the ability to transfer loads parallel with or just inside the plan of the element.

 

 

Column function – the ability to transfer loads parallel with the longitudinal axis.

 

 

Beam function – the ability to transfer loads perpendicular to the longitudinal axis.

 

 

 

The methods of the analysis

 

 

 

 
 

 

 

 

If the wall has 1 fixed support line it is moveable.
 

If the wall has 2 fixed support lines it is moveable.
 

If the wall has 3 fixed support lines it is stable.

 

 

In the determination of how to transfer the forces we introduce some demands for statical way of behavior of the structure.

 

Early in the outline proposal phase  you determine the transfer of forces in the overall statical system of the structure

 

At this time you are normally not bounded by certain choice of materials and therefore the determination of the transfer of forces can be determined entirely by statical principles .

Furthermore you combine the building components to form a structure which is global stable.

 

 

Principles

 

Principles to reach these goals can be one or more of following:

 

a)  To set up statical demands of behavior of the individual building components.

 

b)  To use "self bracing" building components in the structure

 

c)  To use bracing  triangles (additional constructions).

 

d)  To identify the transfer of forces from one building component to another.

 

 

ad. a)

 

There are worked with demands for functions to the individual building components.

 

 

Slab function

 

The ability to resist loads perpendicular to the planar face.

 

 

Wall function

 

The ability to resist loads in plan with the component.

 

 

 

 

 

 

Beam function

 

The ability to continue loads perpendicular to the longitudinal axis.

 

Column function

 

The ability to continue loads inside the planar of the element.

 

 

ad. b)

 

Of common existing system can be mentioned:

 

Column-girder system with cantilevered columns.

2-charnier arch.

2-charnier frame with moment stiff corners.

3-charnier frames with moment stiff corners.

 

 

ad. c)

 

Triangle constructions

 

Diagonals made as tension and/or compression bars. In the structure they act as stable simple triangles or truss.

 

 

ad. d)

 

This could  be essential for the design of the joints.

 

For instance:  

·        How are horizontal forces transferred from a diaphragm  to the end of house.

·        How is a force transferred from a wind bracing to the structure below.

 

 

The individual building components

 

There is of course also demands to the stability of the individual building components where the component becomes unstable for at specific load called the stability load.

The components will additional be loaded for instance by forces caused by temperature fluctuation, eccentric acting forces due to deviation in execution ect.

 

Attention to those forces must be taken later in the engineering design phase.

 

Below follow examples showing how the transfer of forces can be identified and how to illustrate it during the planning.

 

This can be performed in many different ways. Here two essentially different methods are shown.

 

Method A: A mixture of text and sketches.

 

Method B:  A strictly schematic form.

 

 

Example 1

 

Determination of the transfer of  forces in a minor single-story building.

Outline - example

Extract of construction description

Roof construction:
Wing tiles on battens with underlay of plastic foil.
Wooden trusses - 45º roof inclination.
Ceiling facing - 19 mm rebated boards.
200 mm insulation mats.

Masonry:
Outside: 350 mm hollow wall with insulation and steel wall ties.
Inside.: 11 cm wall.

Light weight facades:
Timber skeleton frame.
200 mm insulation.
High impact outside and inside cladding.

 

 

Method A


Disposion of the transfer of forces.

 

Wind load on facades

The load is transferred by the wall to the wall foundation and the roof. The wall has a slab function.

Through the stiffness of the roof area (shear function or wind bracing) the load is leaded to the gable areas, that by shear function deliever the load to the foundation of the gables.

  
 
Wind load on gables

The load is transferred by the wall area to the facades by slab function, and then by wall function to the foundation of the facades.

  
 
Vertical load

The load from the roof area is transferred through the trusses (beam function) to the facades and then through beams, columns and masonry to the foundations (column function).

  

 

 

Method B

 

Disposion to force transferring

Signature:

BF = beam function

SF = slab function

CF = column function

WF = wall function

WB = wind bracing

 

Wind load on facades

Wind load on gables

 

 

 

 

 

Vertical load

 

 

 

Example 2

 

Determination of the transfer of forces in a minor single-story hall building.

Outline - example

Extract of construction description

Load bearing structure:
3 charnier arch on pad foundations.

Roof construction:
Cardboard on underlay of 250 mm insulated roof components with completed down side.

Masonry:
Outside: 400 mm hollow wall with insulation and steel wall ties.

 

 

Method A

 

Disposion to course of forces.

 

Wind load on facades

The load is transferred from the wall area by slab function to the 3-charnier arches and by their self stiffening function they transfer the load further to the pad foundation in the facade.

  
 

Wind load on gables

The load is transferred from the wall area by beam function to vertical wind beams and then further to gable foundation and roof area.

Through the purlins of the roof area (compression members) the load is transferred  further to wind bracings and then by tension to the foundation of the facade.

  
 

Vertical load

The load from the roof area is transferred through the purlins (beam function) to the 3-charnier archs in the structure.

By beam-column function  the arches transfer the load to the pad foundations in the facade.

  


 

Method B

 

Disposion to force transferring

Signature:

BF = beam function

SF = slab function

CF = column function

WF = wall function

WB = wind bracing

 

Wind load on facades

Wind load on gables

Vertical load

 

 

 

Example 3

 

Determination of the transfer of forces in a minor two-story building.

Outline - example

Extract of construction description

Roof construction:
Cardboards on boards.

 

Ceiling construction:
Class 1 facing with insulation.

Suspended floor:
 Precast hollow floor units.

Walls:
First floor:
Outside: Precast concrete sandwich components
Inside: precast concrete components

Second floor:
Wooden based light weight wall with external board facing and internal class 1 facing.

 

 

 

Method A

 

Determination of the transfer of forces.

 

Wind load on facades

 

Second floor:

The load is transferred from the wall area by beam function to suspended floor and roof area.

 

Through the wind bracing of the roof area the load is transferred to the gable areas that by wall function transfer the load to the foundations of the gables.

 

First floor:

The load is transferred from the wall area by slab function to the foundation of the facade and the suspended floor.

 

Through the wall function of the suspended floor the load is transferred to the gable areas that by shear function deliver the load to the foundations of the gables.

  
 

Wind load on gables

 

Second floor:

The load is transferred from the wall area by beam function to suspended floor and roof area.

 

Through the wind bracing of the roof area the load is transferred to the facades that by wall function transfer the load to the foundations of the facades.

 

First floor:

The load is transferred from the wall area by wall  function to the foundation of the gable and the suspended floor.

 

Through the wall function of the suspended floor the load is transferred to longitudinal wall and facades that by wall  function transfer the load to the foundations.

  
 

Vertical load

 

The load from the roof area is transferred by the trusses by beam function to the light weight facade that by beam- and column function transfer the load further

 

The load on the suspended floor is transferred by slab function to the facades and the longitudinal wall and from here further down to the foundation by column function.

  

 

 

Method B

 

Disposion to force transferring

Signature:

BF = beam function

SF = slab function

CF = column function

WF = wall function

WB = wind bracing

 

Wind load on facades

Wind load on gables

Vertical load