Laps for transverse distribution reinforcement
All transverse bars may be lapped at the same location.
The lap length should be at least equal to S1(the spacing of the longitudinal
wires) or the values, given in Table II.5.
Welded mesh using smooth wires
EC2 does not provide direct guidance on this, but refers to national codes. In the UK, BS 8110 provides guidance for such a mesh. Table II.6 may be used to determine the lap length.
II.1.3. Detailing based on American practices
II.1.3.1. Reinforced concrete beam detailing
A reference is made to Sections II.1.1 and II.1.2 for the detailing philosophy of reinforced concrete beams. Mostly these details are based on ACI codes and ASCE codes. Some variations do exist which are directly related to individual state regulations. In some cases detailing needs to cater for the interstate construction activities. The designs are based on the working stress design and strength reduction approach. All beams are designed and detailed to ensure the moments shears and deflections produced by factored load do not exceed the available flexural design strength of the cross section at any point along the length of the beam. If the flexural design strength () Mnjust equals
to the required flexural strength Mu, the criterion for the design is established.
Where Mnis the nominal moment capacity of the cross section and is the
strength reduction of (generally0·9) the section using ACI code. Sometimes
Table II.5. Minimum lap length requirements
Diameter of transverse bars Minimum lap length
Ø6 mm 150 mm
6 mmØ8·5 mm 250 mm
Table II.6. Anchorage and lap lengths as multiples of bar size: smooth wire fabric, fyk460 kN/mm2
Concrete strength: fck 20 25 30 35 40
N/mm2 f
cu 25 30 37 45 50
Straight anchorage: compression 26 24 22 20 19
Straight anchorage: tension 33 30 27 25 23
Laps: compression, tension* 33 30 27 25 23
Laps: tension† 46 42 38 34 33
Laps: tension‡ 66 60 54 49 47
The values in the table apply to (a) good bond.
For poor bond conditions the table values should be divided by 0·7.
The values apply provided: the fabric is welded in a shear-resistant manner complying with BS 4483, and the number of welded intersections within the anchorage is at least equal to 4(Asreq/Asprov). If the latter condition is not
satisfied, values appropriate to the individual bars/wires should be used. * The bars lapped at the section 30%, clear spacing between bars 10Ø and side cover to the outer bar 5Ø (from NAD).
† The bars lapped at the section 30%, or clear spacing between bars 10Ø, or side cover to the outer bar 5Ø.
‡ The bars lapped at the section 30%, or clear spacing between bars 10Ø, or side cover to the outer bar 5Ø.
distribution of shear stresses created by torsion need to be checked. The interaction equations for shear and torsional strengths of concrete must be involved in order to assess the strength capacity of the beam. Various tables and charts are available to aid the design and detailing.
II.1.3.2. Beams and girders
Beam widths
To permit satisfactory placing of concrete and to protect bars from corrosion, the engineer must provide for adequate clear distance between parallel bars and between bars and forms.
The engineer must specify the required concrete protection for the reinforcement.
The engineer must also specify the distance between bars for bond development and concrete placing. For buildings, the clear space is at least one bar diameter, 113times the maximum size of coarse aggregate to be used, but
not less than 1 in. For cast-in-place bridges, required clear space is not less than 1·5 bar diameters, 1·5 times maximum size aggregate, nor 1·5 in.
A wide range of beam widths and the maximum number of bars permitted in a single layer for 34in. and 1 in. maximum aggregate size, respectively, as
provided by ACI 318-83 (revised 1986). Similarly this gives the same information for beams designed under the provisions of the AASHTO 1983 bridge specification. These tables are provided for the use of the engineer; the detailer is not in a position to determine whether bars should be permitted to be placed in more than a single layer.
Beams and girders
Schedules for beams and girders must contain: the beam mark; size of member; number and size of straight and bent bars; special notes on bending; number, size, grade, and spacing of stirrups or stirrup-ties; location of top bars; and any special information, such as the requirement of two layers of steel. Show sections for beam-column joints, where necessary.
In continuous beams the number and spacing of top bars to be placed in T- beam flanges (slabs) for crack control must be shown, if so required by the design.
Beams and joists
For beams, joists, and girders, reinforcement is usually shown in schedules. Bending details may be separate or incorporated in the schedule. Show number, mark, and size of members; number, size, and length of straight bars; number, size, mark, and length of bent bars and stirrups; spacing of stirrups; offsets of bars; lap splices; bar supports; and any other special information necessary for the proper fabrication and placement of the reinforcement. For typical layout a reference is made to Sheet No. II.11. Among the special items that must be noted are:
1. overall length of bar
2. height of hook where such dimensions are controlling 3. lap splice lengths
4. offset dimensions, if any, and
5. location of bar with respect to supporting members where the bar is not dimensioned symmetrically on each side of the support.
For one-way joists, a reference is made to Sheet No. II.12. Reinforcement
Drawings must show the grade, size, spacing, splices, and location of the coated and uncoated bars in the structure. The bar schedule (combined
TYPICAL DETAILS OF RC BEAMS SHEET NO. II.11