Bracing
The bracing of a structure is a decisive factor for its stability and safety. The structural design criteria listed below are independent of the construction method. They apply to masonry construction as well as to steel and timber construction. For spatial systems, a minimum stiffness must be provided by the structural components in all three directions (x, y and z axes). The stiffness is needed to transfer external loads (e.g. wind and earthquake loads) on the one hand and to ensure internal postures (e.g. against buckling, tilting) on the other.
Bracing constructions
The external loads on the stiffening structure must always be transferred to the foundation soil. This is not necessary for internal loads if the internal forces can be balanced within the structure. Since the direction of the external loads is variable (wind direction), the stiffening structure must be connected to the load-transmitting components in a compression- and tension-resistant manner.
Horizontal and vertical bracing elements are required in the three-dimensional structure to transfer the horizontal loads.
Horizontal bracings are e.g. bracings, disks or crossings. In timber frame construction, ceiling discs made of wooden beams and stiffening planking are mainly used. Crossings made of diagonally arranged wind trusses are usually only used for visible ceiling constructions and should remain the exception there as well. Bracing is unusual in timber house construction.
Vertical bracing elements are panes, crossings, bracing, frames or restraints. Typical for timber frame construction are (wall) panes consisting of the load-bearing structural timbers and the interior wood-based panels (as stiffening planking). In special cases (such as large-scale façade glazing or elevated balcony constructions), cross-outs can be used as a practical or visually desirable variant.
If walls are used for vertical bracing, they must be designed and anchored accordingly. In particular, the type and number of fasteners used, the material properties of the wood-based panel used and the tension anchoring of the end studs of wall panels require careful planning and execution. Necessary openings (window openings, door openings) can affect or dictate the bracing systems.
Bracing constructions lying in the roof plane (such as roof bracing or disks) are considered as horizontal bracing. For the design and verification, however, roof slabs can be considered as wall slabs or crossings tilted from the vertical.
If steel windage strips are used to create the effect of the pane, the introduction and dissipation of forces must be precisely detailed and a tight position must be ensured in the installed state.
Braces are truss constructions composed of tension- and/or compression-stiff members. Cross-outs are (diagonally arranged) tension-stiff or compression-stiff (steel) tension members. To form the frame, frame ledgers and stiles must be connected to each other in the corners in a flexurally rigid manner. Alternatively, a truss construction with frame action can be used. Clamped supports transmit the force acting perpendicularly on the beam axis via bending.
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