What is the concrete content of how to place the longitudinal prestressing steel bar? Here is your answer.

　?。?）預應力鋼筋的凈距。先張法預應力鋼筋之間的凈距離應根據澆注混凝土、施加預應力及鋼筋錨固等要求斷定。預應力鋼筋之間的凈距離不該小于其公稱直徑或等效直徑的1.5倍，且應契合下列規則：對熱處理鋼筋及鋼絲，不該小于15mm；對三股鋼絞線，不該小于20mm；對七股鋼絞線，不該小于25mm。

　　(1) Net distance of prestressing steel bar. The net distance between pre-tensioned tendons should be determined according to the requirements of pouring concrete, applying prestressing force and reinforcing bar anchorage. The net distance between prestressing steel bars should not be less than 1.5 times of their nominal diameter or equivalent diameter, and should conform to the following rules: for heat treated steel bars and steel wires, it should not be less than 15 mm; for three strands, it should not be less than 20 mm; and for seven strands, it should not be less than 25 mm.

　?。?）鋼筋、鋼絲的錨固。先張法預應力混凝土構件應確保鋼筋與混凝土之間有牢靠的粘結力，一般宜選用變形鋼筋、刻痕鋼絲、鋼絞線等類鋼材。當選用光面圓鋼絲作預應力配筋時，應根據鋼絲強度、直徑及構件之受力特色選用適當辦法，以確保鋼絲在混凝土中牢靠地錨固，防止鋼絲滑動，并應考慮在預應力傳遞長度規模內抗裂性較低的晦氣影響。

　　(2) Anchorage of steel bar and steel wire. The pre-tensioned pre-stressed concrete members should ensure that there is a strong bonding force between reinforcement and concrete. Generally, deformed steel bars, notched steel wires and steel strands should be selected. When choosing smooth circular steel wire as prestressing reinforcement, appropriate methods should be selected according to the strength, diameter and stress characteristics of steel wire, so as to ensure that steel wire is firmly anchored in concrete and prevent steel wire from sliding, and the obscure effect of low crack resistance in the scale of prestressing transfer length should be considered.

　?。?）后張法預應力鋼絲束、鋼絞線束的預留孔道應契合下列規則：

　　(3) The reserved passages of post-tensioned prestressing tendons and stranded tendons shall conform to the following rules:

　　①對預制構件，孔道之間的水平凈距離不宜小于50mm；孔道構件邊際的凈距離不宜小于30mm，且不宜小于孔道直徑的一半。

　　For prefabricated members, the net horizontal distance between the channels should not be less than 50 mm, and the net distance between the channels and the edge of the components should not be less than 30 mm, and should not be less than half of the diameter of the channels.

　?、谠诳蚣芰褐?，預留孔道在豎直方向的凈距離不該小于孔道外徑，水平方向的凈距離不該小于1.5倍孔道外徑；從孔壁算起的混凝土保護層厚度，梁底不宜小于50mm，梁側不宜小于40mm.

　　(2) In the frame beam, the net distance of the reserved channel in the vertical direction should not be less than the outside diameter of the channel, and the net distance in the horizontal direction should not be less than 1.5 times the outside diameter of the channel; the thickness of the concrete protective layer calculated from the hole wall should not be less than 50 mm at the bottom of the beam and less than 40 mm at the side of the beam.

　?、垲A留孔道的內徑應比預應力鋼絲束或鋼絞線束外徑及需穿過孔道的連接器外徑大10mm～15mm。

　　(3) The inner diameter of the reserved channel should be 10 mm to 15 mm larger than the outer diameter of the prestressing steel wire or strand bundle and the outer diameter of the connector that needs to pass through the channel.

　?、茉跇嫾啥思翱缰袘O置灌漿孔或排氣孔，其孔距不宜大于12m。

　　(4) Grouting holes or exhaust holes should be installed at both ends and spans of components, and the spacing of holes should not be greater than 12 M.

　?、莘仓谱鲿r需求預先起拱的構件，預留孔道宜隨構件一起起拱。

　　Where pre-arched components are required during fabrication, the reserved channel should be arched together with the components.

　?。?）預應力混凝土構件端部安置鋼筋應盡或許均勻安置，一起還應留意以下要求：

　　(4) Reinforcement bars should be placed evenly at the end of the pre-stressed concrete members. Together, the following requirements should be noted:

　?、僖藢⒁徊糠诸A應力鋼筋在接近支座處彎起，彎起的預應力鋼筋宜沿構件端部均勻安置。

　　It is advisable to bend a part of the prestressing steel bar near the support, and the bending prestressing steel bar should be evenly placed along the end of the member.

　?、诋敇嫾瞬款A應力鋼筋需會集安置在截面下部或會集安置在上部和下部時，應在構件端部0.2h（h為構件端部截面高度）規模內設置附加豎向焊接鋼筋網、封閉式箍筋或其他方式的結構鋼筋。

　　(2) When the pre-stressed steel bars at the end of a member need to be assembled at the lower part of the section or at the upper and lower parts, additional vertical welded steel nets, closed stirrups or other structural steel bars should be installed within the scale of 0.2h (h is the height of the section at the end of the member).

　?。?）對先張法預應力混凝土構件，預應力鋼筋端部周圍的混凝土應采取下列加強辦法：

　　(5) For pre-tensioned pre-stressed concrete members, the concrete around the end of the pre-stressed steel bar should adopt the following strengthening methods:

　　①對單根配置的預應力鋼筋，其端部宜設置長度不小于150mm且不少于4圈的螺旋筋；當有牢靠經驗時，亦可利用支座墊板上的插筋代替螺旋筋，但插筋數量不該少于4根，其長度不宜小于120mm.

　　For a single pre-stressed steel bar, it is advisable to install spiral bars with length not less than 150 mm and no less than 4 circles at the end; when there is solid experience, the insertion bars on the support cushion plate can also be used to replace the spiral bars, but the number of insertions should not be less than 4, and the length should not be less than 120 mm.

　?、趯Ψ稚仓玫亩喔A應力鋼筋，在構件端部10d（d為預應力鋼筋的公稱直徑）規模內應設置3片～5片與預應力鋼筋筆直的鋼筋網。

　　(2) Three to five pieces of steel mesh with straight prestressing bars should be set at the end of the member for 10 days (d is the nominal diameter of the prestressing bars).

　　③對選用預應力鋼絲配筋的薄板，在板端100mm規模內應適當加密橫向鋼筋。

　　(3) The transverse reinforcing bar should be properly encrypted in the 100mm scale of the plate end for the thin plate with prestressing steel wire reinforcement.

　?、軐Σ坌伟孱悩嫾?，應在構件端部100mm規模內沿構件板面設置附加橫向鋼筋，其數量不該少于兩根。

　　(4) For grooved slab members, additional transverse reinforcement should be installed along the slab surface of the member within the 100 mm scale at the end of the member, and the number of reinforcement should not be less than two.

　　⑤對預制肋形板，宜設置加強其整體性和橫向剛度的橫肋。端橫肋的受力鋼筋應彎入縱肋內。當選用先張長線法出產有端橫肋的預應力混凝土肋形板時，應在設計和制作上采取防止放張預應力時端橫肋產生裂縫的有用辦法。

　　_For prefabricated ribbed slabs, transverse ribs should be set to strengthen their integrity and transverse stiffness. The reinforced bar of the end transverse rib should bend into the longitudinal rib. When the pre-tensioned long-line method is used to produce the prestressed concrete ribbed slabs with end transverse ribs, a useful method to prevent cracks in end transverse ribs should be adopted in design and fabrication.

　?。?）后張法預應力混凝土構件中，曲線預應力鋼絲束、鋼絞線束的曲率半徑不宜小于4m；對折線配筋的構件，在預應力鋼筋彎折處的曲率半徑可適當減小。在后張法預應力混凝土構件的預拉區和預壓區中，應設置縱向非預應力結構鋼筋；在預應力鋼筋彎折處，應加密箍筋或沿彎折處內側設置鋼筋網片。

　　(6) Curvature radius of curved prestressing steel wire bundle and strand bundle should not be less than 4m in post-tensioned prestressed concrete members, and the curvature radius of folded-wire reinforced components can be reduced appropriately at the bending point of prestressing steel bar. In the pre-tension zone and pre-compression zone of post-tensioned pre-stressed concrete members, longitudinal non-pre-stressed structural steel bars should be installed; in the bending zone of pre-stressed steel bars, stirrups should be tightened or steel meshes should be installed along the inside of the bending zone.