Wood structural design data pdf

Thereby is the design value of the shear strength given by: The design value of the shear capacity is given by: According to the national annex in Sweden, at present EKS 10 BFS , the value of A should be determined on the basis of bef for a structural element subjected to bending moment. Now the notched areas have to be checked. In Eurocode 5: Section 6. Further calculations give that it could be possible to have a notch corresponding to 16 percent of the total depth, in order to still have the sufficient shear capacity.

Alternatively the notches could be reinforced for example with wood screws. Check if the beam dimension is enough in service class 1 and safety class 3.

Include the effect of lateral torsional buckling 3. Loads acting on the beam The loads considered for the design of the double tapered beam are the following: beam self weight, roof dead load and snow load. The wind load can be neglected. Here as an approximation on the safe side we calculate with the snow load on the leeward side according to EKS 10 as uniformly distributed along the whole beam length.

Table 3. The beams are assumed to be indoors, in a heated environment. Thus, the service class can be assumed to be 1. The magnification factor k l increases with increasing roof slope and it can be obtained from Volume 2: Section 8. Within this distance, the depth of the cross section can be regarded as constant.

The critical bending stress can be calculated according to Volume 1: Equation 3. It is important to check the shear capacity for tapered beams due to the normally low beam depth at the supports.

Yet this check is omitted in this example. Determination of stresses The tensile stress perpendicular to the grain can be evaluated by multiplying the bending stress at mid-span by the factor kp, which can be taken from Volume 1: Figure 3. Verifications The tension strength perpendicular to grain shall be reduced in order to take into account the volume effect. The volume of wood which is loaded in tension can be estimated as follows, see Volume 1: Table 3. Additionally the shear capacity at the supports has to be verified.

This is of special importance for double tapered beams because of their reduced cross sectional height at the supports. With purlins spaced at mm centres a load on 1 mm of the primary beam goes directly to the support and does so not contribute to the shear stress.

The compression stress perpendicular to the grain can be evaluated according to Volume 2: Section 5. This steel rod is attached to the floor beam of the balcony with 12 wood screws. The wood screws have a length of 60 mm, a diameter of 8 mm and an ultimate strength of MPa. For simplicity the effective diameter def is here assumed to be equal the outer thread diameter d. This information is usually to be found in the decla- rations from the screw manufacturers.

The thickness of the steel plate is 8 mm. The tensile resistance perpendicular to the grain of the floor beam is assumed to be sufficient to withstand the force from the tie rod. Calculate the maximum load in the tie rod with respect to the capacity of the steel-to-wood connection. Spacings and edge distances for the screws are assumed to be adequate.

However in the example this have been ignored and focus is to show how nail design is done. The beam is loaded with an evenly distributed load. The connection shall thus be designed so that no moment is transferred.

A principal sketch is shown in Figure 4. But for the large connection in Figure 4. Please refer to Eurocode 3 for further details on steel design. The connection will be a single shear connection steel-wood. Volume 1: Table 4. The lowest of these three values will be the characteristic resistance for one nail. In practice this value is usually obtained from each nail manufacturer.

The regulations for spacing parallel and perpendicular to grain needs to be followed, Volume 2: Section For nailed joints, a distance of 5d is prescribed perpen- dicular to the grain and 10d parallel to the grain.

A proposed placement of fasteners would be according to Figure 4. To complete the design of the connection, the steel plates would need to be designed, refer to Eurocode 3 for steel design. Furthermore, the compression perpendicular to the grain of the wood must be checked as indicated in Figure 4. The connection could be the bottom chord in a truss or a purlin in tension. The number of bolts is unknown at the onset of design.

The group effect is in turn dependent on the number n of fasteners in a row, and therefore it is of interest to determine the number of rows that can be placed within the beam height mm. The minimum distance between fasteners in a row is 4d according to Volume 2: Table The edge distance to an unloaded edge is 3d.

Thus, the maximum number of rows that can be placed perpendicular to grain is: 4. The spacing for bolts parallel to the grain is chosen as 7d, which is more than what the standard requires. If more rows could be accommodated within the beam height, this would yield a lower number of bolts in total.

Increasing the beam height can therefore be a good suggestion if not other parameters affect the selection of height. For a connection of this type, a block shear check would have been necessary in practice, see Volume 1: Section 4.

The timber column is fastened with nails to steel sheets cast into the concrete. The vertical force is taken as contact between the bottom of the column and the foundation. The moment is taken as a force couple in the steel sheets. In this case Eurocode 3: Section 6. This means that in this case there is no risk of buckling, but that is so because the moment being moderate in the example and the bottow row of nails are placed as close to the lower end as possible, with respect to end distance 15d.

If the steel sheet would buckle, the lower end of the glulam column would transfer the force to the concrete through contact pressure and we would get a much shorter lever to withstand the moment and therefore an increased force in the tensioned sheet.

Force taken as contact between the steel sheet and the column. To perform a complete check of the connection it is also necssary to check plug shear failure, the strength of the steel sheets, and if the steel sheet can withstand the horizontal force as well as to check the connection between the steel sheets and the foundation.

Check all important resistances in the ultimate limit state ULS , except crushing perpendicular to grain due to support reactions. Check also the maximum instantaneous and final deflections in the serviceability limit state SLS. Note that the beam is braced sideways such that lateral torsional buckling cannot occur. Note also that full composite action can be assumed between the flange timber and the web panel. Transverse web stiffeners are used at both supports.

Let the elastic modulus of the Cflange be the reference material. Note also that the flange is checked at final conditions, while the web edge is checked at instantaneous conditions. This is because the flanges have better creep properties than the web panel.

Maximum bending moment Stress in the Ctimber at the centre of the tension flange Compare! Stress in the Ctimber at the flange edge Stress in the OSB web panel at the edge of the tension flange We conclude that the tension flange is perfectly optimized with regard to bending failure of the timber flange as well as the web panel.

Shear buckling will have a negligible effect on the shear resistance, which can be determined by Volume 1: Equation 5. Maximum design shear force Compare! Shear force resistance without regarding shear buckling, noting that we have one web panel No fiddling around with fictitious cross sections is need, as the flanges are not involved in this failure.

We conclude that also the web panel is well designed with regard to its shear resistance. Check for failure in the glue line between the web panel and the flange timber, see Volume 1: Section 5. Note that bw is the physical thickness and not a fictitious thickness.

It is just that the shear stresses are more concentrated towards the inner corner in an I-beam than in a boxed beam that is taken into account through ngl. The depth of the glue line is We must, therefore, use a reduced planar rolling shear strength of the board material, which is lower than the shear strength of the timber.

Compare to the reduced planar shear strength We conclude that the glue line has more than sufficient strength. The deflections calculated are based on Volume 1: Equations 5. Instantaneous shear deflection caused by the permanent load Note that there is no difference between the two values as they are not based on a fictitious cross section.

Instantaneous shear deflection caused by the snow load Note that there is no difference between the two values as they are not based on a fictitious cross section. The wind truss is placed right below the roof plane. The horizontal loads are led by means of purlins to separate compression struts, which lay in the same plane as the diagonal steel bars. This to avoid eccentricities in the truss joints.

The support reactions from the wind truss are led by means of a pair of diagonal steel bars in each longside wall to the foundation, but they are not designed in this example.

The geometry of the structure is shown in Figure 6. The pressure coefficient are assumed 0,85 and 0,3 for the windward wall and the leeward wall respectively.

The wind loads considered for the design of the roof wind truss are shown in Figure 6. When you buy books using these links the Internet Archive may earn a small commission. Open Library is a project of the Internet Archive , a c 3 non-profit. This edition doesn't have a description yet. Can you add one? Add another edition? Copy and paste this code into your Wikipedia page. Need help? Wood structural design data. Donate this book to the Internet Archive library.

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