Plan-drawing (pingfa) rebar terminology: the formal terms for top bars / bottom bars / additional bars / through bars, their atlas and code basis, and construction requirements

Topic Positioning

A terminology dictionary for reading pingfa (plan-integrated structural drawing) construction drawings: mapping common slang — top bars / bottom bars / additional bars / through bars — to formal atlas/code terms with their construction requirements, for cast-concrete detailing, rebar takeoff, and drawing reviews.

Core Conclusions

1. Pingfa background GB/T 50105-2010 Section 3.3: text-annotated member representation, i.e., the plan-integrated method (pingfa), is a major reform of cast-concrete detailing... 3.3.1: member sections and reinforcement may be expressed by text annotation; besides traditional details, text-annotated (pingfa) representation may be used. Jianke [2000] No. 157 approved eleven atlases including "Plan-integrated representation rules and detail drawings for cast-concrete construction drawings" as national standard design atlases, effective from approval. The current general series is 22G101 (2022, replacing 16G101; 22G101-1 covers frames, shear walls, beams, slabs); where drawings cite another edition, that edition governs.

2. Four-term mapping

1. Top bars -> upper reinforcement (face bars in slabs): the bar layer near the top face. In slabs: top continuous bars and support-top non-continuous bars (trade "kou-jin", extending only per marked lengths near supports); in beams: "upper longitudinal bars / upper through bars". Note: beam "first row, second row" are rows within the same position, not top/bottom layers. Raft slabs likewise use top/bottom mesh.
2. Bottom bars -> lower reinforcement (bottom bars in slabs): the layer near the bottom; in beams "lower longitudinal bars". One-way slab distribution bars are usually noted globally.
3. Additional bars -> additional reinforcement (strengthening; the most easily missed or double-counted in takeoff — compute per occurrence). Code term "transverse additional reinforcement": GB 50010-2010 (2015 ed.), 9.2.11 — "concentrated loads acting below the bottom or within the beam depth shall be carried entirely by transverse additional reinforcement; stirrups are preferred"; "stirrups shall be arranged over a length of 2h1 + 3b"; "where hanger bars are used, the bent segments extend to the beam top edge with end horizontal lengths per 9.2.7"; the commentary forbids substituting shear stirrups in the influence zone. Additional stirrups and hanger bars at primary-secondary beam junctions are typical; slab corner (radial) bars, opening bars, and support short bars are marked "add + value".
4. Through bars -> bars continuous over the full length (formal term, vs "support-top negative bars" and "erection/spacer bars"). GB 50010-2010 (2015 ed.), 11.3.7: "at least two continuous longitudinal bars top and bottom over the full beam length; grades 1-2: diameter >= 14mm and respectively >= 1/4 of the larger top/bottom end section areas; grades 3-4: >= 12mm." GB 50011-2010 (2016 ed.), 6.3.4(1) the same: grades 1-2 not less than 2φ14 (and >= 1/4); grades 3-4 not less than 2φ12.

3. Key clarifications

• "Through" permits splices (11.3.7 commentary): "'through' here ensures these bars exist at all beam positions; it does not forbid splices at suitable points."
• Vs spacer (erection) bars: construction-positioning bars with diameters per 9.2.6 — spans < 4m preferably >= 8mm; 4-6m >= 10mm; > 6m preferably >= 12mm. Pingfa writes same-row through + spacer bars as "2Φ25+(2Φ12)" (brackets = spacers).
• Formal usage: top/bottom/additional bars are slang with regional variants ("upper/lower bars", "face/bottom bars"); formal documents, BOQ descriptions, and as-built records use the formal terms.

Applicable Boundaries

• Applies to cast-concrete drawing reading, rebar takeoff, and reviews; the slang is not for formal documents.
• Clauses cited: GB 50010-2010 (2015 ed.) 9.2.6, 9.2.11, 11.3.7; GB 50011-2010 (2016 ed.) 6.3.4; construction values per design and current codes; partial revisions govern.
• Atlas edition per the drawings: 22G101 is the current general reference; older projects may cite 16G101 or earlier — follow the cited edition for construction and takeoff.

Further Reading

• GB/T 50105-2010 Section 3.3 (incl. 3.3.1).
• Jianke [2000] No. 157 approval notice for the eleven atlases.
• GB 50010-2010 (2015 ed.) 9.2.6, 9.2.11, 11.3.7 (with commentary).
• GB 50011-2010 (2016 ed.) 6.3.4, 6.3.3.
• 22G101 series atlases — full notation rules (slab T/B, beam collective/site annotations) per the atlases.