钢筋混凝土框架结构设计的几点心得体会

张永涛 姬广东

（山东省冶金设计院有限责任公司  莱芜  271104）

摘要：在钢筋混凝土结构设计中，每个设计者的经验不同，对规范的理解不同，所以在处理某个设计问题时，也就会采取不同的处理方法。对于钢筋混凝土框架结构设计中，基础、梁、柱、板四部分应注意的问题，分别提出了几点看法。

关键词：结构设计基础梁柱板

    现在越来越多的建筑物使用钢筋混凝土结构，故钢筋混凝土结构在整个建筑市场起到越来越重要的地位。在钢筋混凝土结构设计中，每个设计者的经验不同，对规范的理解不同，所以在处理某个设计问题时，也就会采取不同的处理方法。在这十年的结构设计工作中，本人也积累了一些经验，下面就钢筋混凝土框架结构设计中的基础、梁、柱、板四部分，在设计时应注意的问题，阐述一下个人观点。       

 1.基础部分        

1.1对于柱下扩展基础宽度较宽(大于4米)或地基不均匀及地基较软时宜采用柱下条基。并应考虑节点处基础底面积双向重复使用的不利因素，适当加宽基础。        

1.2建筑地段较好，基础埋深大于3米时，应建议甲方做地下室。当地基承载力满足设计要求时，地下室底板可不再外伸以利于防水。每隔30~40米设一后浇带，并注明两个月后用微膨胀混凝土浇注。设置地下室可降低地基的附加应力，提高地基的承载力(尤其是在周围有建筑时有用)，减少地震作用对上部结构的影响。不应设局部地下室，且地下室应有相同的埋深。        

1.3地下室外墙为混凝土时，相应的楼层处梁和基础梁可取消。        

1.4抗震缝、伸缩缝在地面以下可不设，连接处应加强。但沉降缝两侧墙体基础一定要分开。        

1.5新建建筑物基础不宜深于周围已有基础。如深于原有基础，其基础间的净距应不少于基础高差的2倍，否则应打抗滑移桩，防止原有建筑的破坏。建筑层数相差较大时，应在层数较低的基础方格中心的区域内垫焦碴来调整基底附加应力。        

1.6独立基础偏心不能过大，必要时可与相近的基础做成柱下条基。柱下条形基础的底板偏心不能过大，必要时可作成三面支承一面自由板(类似筏基中间开洞)。两根柱的柱下条基的荷载重心和基础底版的形心宜重合，基础底板可做成梯形或台阶形，或调整挑梁两端的出挑长度。        

1.7独立基础的拉梁宜通长配筋，其下应垫焦碴。拉梁顶标高宜较高，否则底层墙体过高。        

1.8底层内隔墙一般不用做基础，可将地面的混凝土垫层局部加厚。        

1.9考虑到一般建筑沉降为锅底形，结构的整体弯曲和上部结构与基础的协同作用，顶、底板钢筋应拉通(多层的负筋可截断1/2或1/3)，且纵向基础梁的底筋也应拉通。        

1.10基础底板混凝土不宜大于C3O，一是没用，二是容易出现裂缝。        

1.11基础底面积不应因地震附加力而过分加大，否则地震下安全了而常规情况下反而沉降差异较大，本末倒置。 免费论文下载中心         

2.柱部分        

2.1地上为圆柱时，地下部分应改为方柱，方便施工。圆柱纵筋根数最少为8根，箍筋用螺旋箍，并注明端部应有一圈半的水平段。方柱箍筋应使用井字箍，并按规范加密。角柱、楼梯间柱应增大纵筋并全柱高加密箍筋。幼儿园不宜用方柱。

     2.2原则上柱的纵筋宜大直径大间距，但间距不宜大于200。

     2.3柱内埋管，由于梁的纵筋锚入柱内，一般情况下仅在柱的四角才有条件埋设较粗的管。管截面面积占柱截面4%以下时，可不必验算。柱内不得穿暖气管。

     2.4柱断面不宜小于450×450，混凝土不宜小于C25，否则梁纵筋锚入柱内的水平段不容易满足0.45La的要求，不满足时应加横筋；否则在梁柱节点处钢筋太密，混凝土浇筑困难。异型柱结构，梁纵筋一排根数不宜过多，柱端部纵筋不宜过密，否则节点混凝土浇筑困难。当有部分矩形柱部分异型柱时，应注意异型柱的刚度要和矩形柱相接近，不要相差太大。        

2.5柱应尽量采用高强度混凝土来满足轴压比的限制，减小断面尺寸。       

    2.6尽量避免短柱，短柱箍筋应全高加密，短柱纵筋不宜过大。       

    2.7考虑到竖向地震作用，柱子的轴压比及配筋宜留有余地。        

2.8独立柱上或柱的中部（半层处）有挑梁时，挑梁长度应有限制。       

 3.梁部分       

    3.1梁上有次梁处(包括挑梁端部)应附加箍筋和吊筋，宜优先采用附加箍筋。附加筋一般要有，但不应绝对。规范说的清楚，位于梁下部或梁截面高度范围内的集中荷载，应全部由附加横向钢筋承担。也就是说，位于梁上的集中力如梁上柱、梁上后做的梁如水箱下的垫梁不必加附加筋。位于梁下部的集中力应加附加筋。但梁截面高度范围内的集中荷载可根据具体情况而定。当主次梁截面相差不大，次梁荷载较大时，应加附加筋。当主梁高度很高，次梁截面很小、荷载很小时，如快接近板上附加暗梁，主梁可不加附加筋。还有当主次梁截面均很大，如工艺要求形成的主次深梁，而荷载相对不大，主梁也可不加附加筋。       

    3.2当外部梁跨度相差不大时，梁高宜等高，尤其是外部的框架梁。当梁底距外窗顶尺寸较小时，宜加大梁高做至窗顶。外部框架梁尽量做成外皮与柱外皮平齐。梁也可偏出柱边一较小尺寸。梁与柱的偏心可大于1/4柱宽，并宜小于1/3柱宽。        

3.3梁上有次梁时，应避免次梁搭接在主梁的支座附近，否则应考虑由次梁引起的主梁抗扭，或增加构造抗扭纵筋和箍筋。当采用现浇板时，抗扭问题并不严重。       

    3.4原则上梁纵筋宜小直径小间距，有利于抗裂，但应注意钢筋间距要满足要求，并与梁的断面相应。箍筋按规定在梁端头加密。布筋时应将纵筋等距，箍筋肢距可不等。小断面的连续梁或框架梁，上、下纵筋均应采用同直径的，尽量不在支座搭接。        

3.5端部与框架梁相交或弹性支承在墙体上的次梁，梁端支座可按简支考虑，但梁端箍筋应加密。        

3.6上反梁的板吊在梁底下，板荷载宜由箍筋承受，或适当增大箍筋。梁支承偏心布置的墙时宜做下挑沿。        

3.7挑梁宜作成等截面(大挑梁外露者除外)。与挑板不同，挑梁的自重占总荷载的比例很小，作成变截面不能有效减轻自重。变截面挑梁的箍筋，每个都不一样，难以施工。变截面梁的挠度也大于等截面梁。挑梁端部有次梁时，注意要附加箍筋或吊筋。一般挑梁根部不必附加斜筋，除非受剪承载力不足。对于大挑梁，梁的下部宜配置受压钢筋以减小挠度。挑梁配筋应留有余地。 免费论文下载中心         

3.8梁上开洞时，不但要计算洞口加筋，更应验算梁洞口下偏拉部分的裂缝宽度。梁从构造上能保证不发生冲切破坏和斜截面受弯破坏。        

3.9挑梁出挑长度小于梁高时，应按牛腿计算或按深梁构造配筋。        

3.10扁梁宽度不必过大，只要钢筋能正常摆下及受剪满足即可。因为在挠度计算时，梁宽对刚度影响不大，加宽一倍，挠度减小20%左右。相对来讲，增大钢筋更经济，钢筋加大一倍，挠度减小60%左右，同时梁的上筋应大部分通长布置，以减小混凝土徐变对挠度的增大，如果上筋不小于下筋，挠度减小20%。       

    3.11当一宽框架梁托两排间距较小的柱时，可加一刚性挑梁，两个柱支承在刚性挑梁的端头。       

    3.12梁宽大于350时，应采用四肢箍。        

4.现浇板部分        

4.1板的钢筋宜采用大直径大间距，但间距不大于200，间距尽量用200。(一般跨度小于6.6米的板的裂缝均可满足要求)。板上下钢筋间距宜相等，直径可不同，但钢筋直径类型也不宜过多。        

4.2相连几个房间的同型号同间距板底钢筋宜连通。        

4.3配筋计算时，可考虑塑性内力重分布，将板上筋乘以0.8~0.9的折减系数，将板下筋乘以1.1~1.2的放大系数。        

——出处：《中国经济与管理科学》20##年第7期

Structure design of reinforced concrete frame

Zhang Yongtao  Ji Guangdong

(Shandong Province Metallurgical Design Institute Co., Ltd. Laiwu 271104)

Abstract: In the reinforced concrete structure design, each designer's experience is different, different understanding of norms, so in dealing with a certain design issues, it would take a different approach. For the design of reinforced concrete frame structure, foundations, beams, columns, boards should pay attention to the issue of four parts, respectively, made a few observations.

Keywords: Structural design of foundation beam plate

More and more buildings to use reinforced concrete structure, reinforced concrete structure and therefore the entire construction market play an increasingly important role. In the reinforced concrete structural design, each designer's experience is different, different understanding of norms, so in dealing with a certain design issues, it would take a different approach. In this decade, the structural design work, I have accumulated some experience, the following on the design of reinforced concrete frame structure, the foundation, beams, columns, panels of four parts in the design should pay attention to the problem, elaborate personal views.

1.The fundamental elements of

The expansion of the basis for the column width under a wide (greater than 4 meters) or the uneven ground and foundation should be adopted when compared with the soft base of the next column. And should consider the basis of node size at the end of a two-way repeated use of unfavorable factors, appropriate widening base.

    1.2 Building lot better basis for depth greater than 3 meters, should recommend to the Party to do the basement. Bearing capacity of the local base to meet the design requirements, the basement floor can be no overhang to facilitate water. Every 30 ~ 40 meters is located one after the pouring zone, and indicate the two months after the pouring of concrete with micro-expansion. Setting the foundation of the basement can reduce the additional stress, improve the bearing capacity of foundations (especially in the construction around when useful) to reduce the role of the upper structure of the earthquake impact. Should not be any partial basement, and the basement should have the same depth.

     1.3 for the concrete basement wall, the corresponding floor beams and foundation beams at cancel.        

1.4 earthquake seam, expansion joints on the ground below may from time to set up, connections should be strengthened. However, the basis of settlement joint on both sides of the wall must be separated.        

The basis of

1.5 new buildings should not be darker than the surrounding existing basis. As deeply as the original foundation, based on the basis of inter-spacing of not less than 2 times the height difference, or to fight anti-sliding pile should be to prevent the destruction of the original building. Larger difference between the construction layers should be the basis of the lower layers within the region grid center ballast to adjust the base pad coke additional stress.        

1.6 Independence-based bias can not be too large, if necessary, the foundation made with similar articles under column base. Column strip foundation under the floor can not be too eccentric, if necessary, could be made on three sides, supporting one side of free (similar to the Raft-based intermediate open hole). Column 2 column article under the base load center of gravity and centroid-based bottom plate should overlap the foundation floor or stairs can be made into trapezoidal shape, or adjusting the length of cantilever beam at both ends of Chutiao.        

1.7 Independence-based pull-Liang Yi-length reinforcement, under which should focus ballast mat. Top elevation should pull high beam, or the bottom of the wall is too high.        

1.8 in the bottom wall generally do not have to do based on the concrete floor cushion can be partially thickened.        

1.9 Taking into account the general settlement of the bottom of the pot-shaped building, the structure of the overall bending and the upper structure and the basis of synergies, top and bottom reinforcement should be raton (multi-layer of negative reinforcement can be cut off 1 / 2 or 1 / 3), and the foundation beam bottom longitudinal reinforcement should also be raton.        

1.10 foundation slab of concrete should not be larger than C3O, one useless the second is prone to cracks.        

1.11 The foundation area should not unduly increase the earthquake additional force, otherwise the next earthquake safety, rather the contrary, the settlement, under normal circumstances are quite different cart before the horse. Reposted elsewhere in the paper for free download     

2. Column part of the        

     2.1 on the ground for the cylinder, the underground portion should be replaced by square columns, to facilitate construction. Column longitudinal reinforcement root number at least 8, stirrup with spiral bands, and indicate the end of the horizontal segment should have a lap and a half. Square columns Tic-Tac-hoop stirrups should be used, in accordance with standard encryption. Corner column, stair column longitudinal reinforcement should be increased, and the whole column stirrups high encryption. Kindergarten should not use the square column.        

2.2 In principle, the vertical column reinforcement should large-diameter large spacing, but the pitch should not be larger than 200.        

2.3 Column pipe, due to the beam longitudinal reinforcement anchored into the column, the general only in the column under the conditions laid four corners have thick tube. Tube-sectional area of column cross section accounted for less than 4%, it can not checking. Column shall not clothing trachea.        

    2.4 column cross-section should not be less than 450 ??450, concrete should not be less than the C25, otherwise the beam longitudinal reinforcement anchored into the column level within the segment is not easy to satisfy the requirements of 0.45La, does not meet the horizontal bars should be added; otherwise reinforced beam-column nodes are too dense, concrete placement difficult. Special-shaped column structure, and beam longitudinal reinforcement should not be too much root number in a row and column longitudinal reinforcement ends should not be too dense, otherwise the node concrete placement difficult. When there is some part of the rectangular column-shaped columns, they should pay attention to special-shaped columns and rectangular column stiffness was similar and not that much difference.        

2.5 column should be using high-strength concrete to meet the axial load ratio limits, reduce the section size.        

2.6 try to avoid short columns, short columns stirrup should be full of high encryption, short column longitudinal reinforcement should not be too large.        

2.7 Taking into account the role of vertical earthquake, columns under axial compression ratio and reinforcement should leave some leeway.        

2.8 independent of the central column or columns (semi-floor office) are cantilever beam, the cantilever beam length should be limited.        

 3. LIANG part of the        

3.1 beam with sub-beam Department (including the cantilever beam ends) should be attached stirrups and hanging bars, should give priority to adopt additional stirrups. Additional tendons in general should be, but not absolute. A clear specification that is located in the lower beam or high beam within the scope of the concentrated load shall be borne entirely by additional transverse reinforcement. In other words, the concentration of power in the beam, such as beam columns, beams after the beam to do under the pad-like water tanks do not have to add additional muscle. Is located in the lower beam of concentration should be added additional reinforcement. However, a high beam within the concentrated load can be determined according to specific circumstances. When the primary and secondary beam cross-section more or less, sub-beam load is large, additional reinforcement should be added. When the main beam at very high altitudes, sub-beam cross-section is very small, load is very small, such as the approach the board added the dark beam, main beam may from time to add additional muscle. There were significant when the primary and secondary beam, such as the process requires the formation of the primary and secondary deep beam, while the load is relatively small, the main beam or not to add additional muscle.        

3.2 when the external beam span or less, Liang Gao Yi high, especially outside the frame beam. When the beam away from the outer windows of the top end of small size, it is desirable to do to increase the beam window of a high top. As far as possible outside the framework of beams and columns made of skin skin flush. Liang-chu, may also be missed while a smaller size. Eccentric beam-column may be greater than 1 / 4 columns wide and appropriate less than 1 / 3 of column width.        

There are times when the beam

    3.3 beam should avoid secondary beam overlap in the vicinity of the main beam of the bearing, otherwise, consideration should be given by the second torsion beam caused by the main beam, or increasing the longitudinal reinforcement and stirrup torsional structure. When using in-situ plate, the torsion problem is not serious.        

3.4 In principle, small-diameter beam longitudinal reinforcement should a small spacing is conducive to cracking, but it should be noted that reinforcement spacing to meet the requirements, and with the corresponding cross-section of beam. Stirrups at the end of the beam according to the provisions of the first encryption. Fabric reinforcement should be equidistant longitudinal reinforcement, stirrups, etc. from time away from the limb. Small cross-section of a continuous beam or frame beams, the upper and lower longitudinal reinforcement should be using the same diameter as much as possible not to overlap bearings.        

3.5 end with the frame beams intersect, or elastic support at the wall on the sub-beams, simply supported beam end bearing may be considered, but the end of the beam stirrups should be encrypted.        

3.6 The panel of anti-beam suspended beneath the beam, plate load appropriate for the stirrups to bear, or an appropriate increase in stirrup. Eccentric arrangement of beams supporting the walls along the opportune time to do the next pick.        

3.7 pick Liang Yiross-section (large cantilever beam except those exposed). And pick a different panel to pick the beam weight ratio of the total load is small, ariable cross-section can not effectively reduce weight. Variable cross-section cantilever beam of the stirrups, each is different and difficult construction. Variable cross-section beam deflection is also greater than the other beam. Cantilever beam with secondary beam end, attention should be attached stirrups or hanging bars. Generally do not have to add the root of cantilever beam oblique muscle, unless the lack of shear strength. For large cantilever beam, the beam bottom reinforcement should configure the compression to reduce the deflection. Cantilever beam reinforcement should leave room for the. Reposted elsewhere in the paper for free download       

3.8 beam openings, not only to calculate the hole reinforcement, hole should be checking under the partial pull-beam part of the crack width. Beams from the structure does not occur on the punching can guarantee the damage and oblique cross-section flexural damage.        

3.9 Chutiao cantilever beam is less than the length of beam is high, should be calculated or bracket structure reinforced by deep beams.        

3.10 flat-beam width not too large, as long as the steel can be placed under the normal and shear can be met. Because the deflection calculation, the beam width on the stiffness had little impact broadening doubled, the deflection reduced about 20%. Relatively speaking, increasing the steel more economical, steel increased to double the deflection reduced about 60%, while the majority of the beam on the tendon to be a long-pass arrangement to reduce the deflection of concrete creep on the increase, if the tendon not less than under the ribs, deflection reduced by 20%.        

3.11 As a broad framework of the Beam smaller distance between two rows of columns, it can add a stiff cantilever beam, the two columns supported on rigid cantilever beam of the end of the first.        

3.12 beam large at the 350 should be used limbs hoop.        

4. Part Slab        

4.1 The board should adopt the large-diameter steel big pitch, but the spacing is not greater than 200, the pitch as far as possible with the 200. (Usually span of less than 6.6 meters cracks in the board can meet requirements). Under the steel plate spacing should equal diameter can be different, but the bar diameter type is also not too much.        

4.2 connected to a few rooms at the end of the same model reinforced with the pitch plate should connect.        

4.3 reinforcement calculations, may consider plastic redistribution of internal force will be multiplied by 0.8 to 0.9 bars on-board the discount factor will be multiplied by the plate under the tendons of the amplification factor of 1.1 ~ 1.2.        

——From: Chinese Economy Management Science Magazine,2009.7