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Alternative bottom beam reinforcement layouts can reduce congestion
Beam-column joints are frequently areas of congestion in reinforced concrete construction. Several factors can contribute to beam-column joint congestion, such as column verticals that terminate in the beam with hooks and excessive top steel over the column. By far the most common problem, however, is the lapping of bottom beam bars at a column to meet the structural integrity requirements in Section 7.13 of ACI 318-05,1 especially if the column and beam are the same width.
When the bottom beam bars are lapped at the column, the number of bottom bars that must pass through the joint doubles. The resulting congestion can contribute to poor consolidation of the concrete at a critical location where the concrete is under a complex state of stress and may also cause clearance problems with the column ties or beam stirrups. This congestion can be significantly reduced by using alternative splice locations and bar arrangements.
The following discussion presents four general splice arrangements, along with the advantages and disadvantages of each from a constructibility point of view. Designers must also consider structural issues when selecting among the alternative locations for the bottom bar splices. Only continuous bottom beam bars are shown. All other bars are omitted for clarity.
ARRANGEMENT #1-SPLICES LOCATED AT SUPPORTS
The most common arrangement is to locate...