浅谈我国多层混凝土框架结构设计

浅谈我国多层混凝土框架结构设计

一、 前言

随着社会的发展,钢筋混凝土框架结构的建筑物越来越普遍.由于钢筋混凝土结构与砌体结构相比较具有承载力大、结构自重轻、抗震性能好、建造的工业化程度高等优点；与钢结构相比又具有造价低、材料来源广泛、耐火性好、结构刚度大、使用维修费用低等优点。因此，在我国钢筋混凝土结构是多层框架最常用的结构型式。近年来，世界各地的钢筋混凝土多层框架结构的发展很快，应用很多。

一般框架结构是由楼板、梁、柱及基础4种承重构件组成的，由主梁、柱与基础构成平面框架，各平面框架再由连续梁连接起来而形成的空间结构体系。在合理的高度和层数的情况下，框架结构能够提供较大的建筑空间，其平面布置比较的灵活，可适合多种工艺与使用功能的要求。

多层钢筋混凝土框架结构设计可以分为四个阶段：一是方案设计，二是结构分析，三是构件设计，四是绘施工图。结构分析和构件设计是结构设计中的计算阶段，在现代，已由电子计算机承担这一工作，常采用PKPM建模计算。但是，结构的计算并不能代替结构的设计。良好的结构设计的重要前提，应该是合理组织与综合解决结构的传力系统、传力方式，良好的结构方案是良好结构设计的重要前提。

二、 关于框架结构设计文献回顾

2.1框架结构的优缺点

框架结构体系是由横梁与柱子连接而成.梁柱连接处(称为节点)一般为刚性连接,有时为便于施工和其他构造要求,也可以将部分节点做成铰接或者半铰接.柱支座一般为固定支座,必要时也可以设计成铰支座.框架结构可以分为现浇整体式,装配式,现浇装配式.

文献[3]中提到:框架结构的布置灵活,容易满足建筑功能和生工艺的多种要求.同时,经过合理设计,框架结构可以具有较好的延性和抗震性能.但是,框架结构承受水平力(如风荷载和水平地震作用)的能力较小.当层树较多或水平力较大时,水平位移较大,在强烈地震作用下往往由于变形过大而引起非结构构件(如填充墙)的破坏.因此,为了满足承载力和侧向刚度的要求,柱子的截面往往较大,既耗费建筑材料,又减少使用面积.这就使框架结构的建筑高度受到一定的限制.目前,框架结构一般用于多层建筑和不考虑抗震设防,层数较少的的高层建筑(比如,层数为10层或高度为30米以下)

2.3框架结构的布置

多层框架结构的平面布置形式非常的灵活，将框架结构按照承重方式的不同分为以下三类：

(1)横向框架承重方案 以框架横梁作为楼盖的主梁,楼面荷载主要由横向框架承担.由于横向框架数往往较少,主梁沿横向布置有利于增强房屋的横向刚度.同时,主梁沿横向布置

还有利于建筑物的通风和采光.但由于主梁截面尺寸较大,当房屋需要大空间时,净空较小,且不利于布置纵向管道.

(2)纵向框架承重方案 以框架纵梁作为楼盖的主梁,楼面荷载由框架纵梁承担.由于横梁截面尺寸较小,有利于设备管线的穿行,可获得较高的室内净空.但房屋横向刚度较差,同时进深尺度受到预制板长度的限制.

(3)纵横向框架混合承重方案 纵横向框架混合承重方案是沿纵横两个方向上均布置有框架梁作为楼盖的主梁,楼面荷载由纵,横向框架梁共同承担.它具有较好的整体工作性能.

2.4双向板的截面设计构造及配筋

对于周边与梁整浇的双向板，由于在两个方向受到支撑构件的变形约束，整块板内存在穹顶作用，使板内的弯矩大大减小。为了利用这一有利的因素，规范允许对四边与梁整结板，起弯矩的设计值根据一定的条件进行折减。双向板的厚度不宜小于80mm.由于挠度不另作验算，双向板的板厚与短跨跨长的比值应满足：简支板、连续板 。双向板按照弹性理论方法设计时，所求得的跨中正弯矩钢筋数量是指板的中央处的数量，靠近板的两边，其数量可以逐渐减小。考虑到施工方面，将板的两个边方向上各分为3个板带。两个方向的边缘板带宽度军为均为短边长度的1/4，其余则为中间板带。在中间板带上，按跨中最大正弯矩求得的单位板宽内的钢筋数量均匀布置；而在边缘板带上，按中间板带单位板宽内的钢筋数量一半均匀布置。

2.5框架梁和柱的电算结果的人工调整

框架梁配筋的人工调整，其目的是解决梁的裂缝宽度超限和“强剪弱弯”问题。文献[5]中提到当裂缝宽度超限时，首先应考虑将大直径的钢筋改用小直径的钢筋验算，如裂缝宽度仍然超限，就应增大梁的配筋和混凝土的强度等级，或加大梁的截面尺寸，调整至满足规范的要求。为了保证“强剪弱弯”，可进行以下几项调整：一是适当增大梁端截面；二是适当增大梁端箍筋直径，加密箍筋间距；三是梁端负弯矩钢筋不放大，梁跨中受拉钢筋适当放大1．1～1．2倍；四是按构造要求对跨度>7m的框架梁增加弯起钢筋。

在地震力作用下，框架柱尤其是角柱和大开间、大进深的边柱，一般均处于双向偏心受压状态，而电算程序是按两个方向分别为单向偏心受压的平面框架计算配筋。因此，框架柱配筋应进行如下调整：一是选择最不利的方向进行框架计算，也可对两个方向均进行计算后取较大值方向的配筋，并采用对称配筋；二是控制柱单边方向钢筋的最少根数。四是选择井字形或菱形的框架柱箍筋形式，以增强箍筋对混凝土的约束；五是由于多层框架电算一般不考虑温度应力和基础不均匀沉降问题，当多层框架水平尺寸较大以及地基为软弱土层或地基土层不均匀时，可适当再稍放大框架柱的配筋。

2.6周期折减系数的取用

进行框架结构的周期和刚度计算时。往往忽略框架填充墙的影响。但实际情况中填充墙(砖砌体)在早期弹性工作阶段参与工作的能力是较大的。使结构实际的刚度大于计算刚度，实际的周期小于计算周期，地震作用计算偏小。结构设计偏于不安全。为了避免较大

误差，在设计过程中应该对计算周期应该进行折减。一般情况．周期折减系数的取值： 当填充墙为砌体时，取0．6～0．7； 为轻质砌块或砌体填充墙较少时， 取0．7～0．8； 当填充墙为轻质墙体板材时，取0．9；无填充墙的纯框架取1．0。可以看出，填充墙的刚度越小对框架的周期影响越小，吸收地震作用的能力也越弱.

三、 结语

由于框架结构具有空间大、平面布局灵活多样的特点，满足了人们不断追求使用个性化的要求。随着社会的不断发展和人们物质生活水平的提高，框架结构(住宅、公共建筑)将会得到较大发展。设计多层框架结构，设计人应首先判断结构方案的可行性，对可能碰到的问题，提前采取措施予以解决，并对所有计算结果认真分析、判断，准确无误后方可应用于实际工程。

综上所述,对于我来说,在做毕业设计(某高校教学楼)时,要根据规范以及实际的环境,选取构件参数和设计参数.此外,还要多了解一些结构细部构造等设计.通过查看规范,杂志等文献资料,对建筑结构的设计有一个具体的认识,争取将毕业设计作好.

Report of a framework of our multi-storey concrete

structure literature review

I Introduction

With the development of society, reinforced concrete frame structure building more and more common. As the reinforced concrete structures and masonry structures , compared with large carrying capacity, structure, light weight, good seismic performance, construction of the advantages of higher level of industrialization ; and steel structure as compared with the low cost, wide range of sources, fire, good structural rigidity, use and maintenance cost is low. Therefore, in our reinforced concrete structure is the most commonly used multi-frame structure type. In recent years, the world multi-storey reinforced concrete frame structure is developing very rapidly, application of many.

General framework of the structure is a floor, beams, columns and foundation composed of four kinds of bearing components, the main beams, columns and form the basis of plane frame, the plane frame connected by the beam of the space structure system. at a reasonable height and number of layers of the case下, frame Jiegou able to provide larger building space, Allocation Comparison of Linghuo may be suitable for Duozhonggongyi and Shiyong the functions.

Multistory reinforced concrete frame structure design can be divided into four stages: First, program design, and second, structural analysis, third, component design, the four are drawn drawings. Structural analysis and component design is structural design calculation stage, in the modern, from computer to the job, often calculated by PKPM modeling. However, the structure calculation and not a substitute for structural design. A good structure, an important prerequisite for the design, organization and should be reasonably comprehensive solution structure of the force transmission system, transfer method, a good structure of the program is a good structure, an important prerequisite for the design.

II On the frame structure design literature review

2.1 Frame structure of the advantages and disadvantages

Frame structure system is connected by the beams and columns made of. column joints (called nodes) is generally rigid, and sometimes for the ease of construction and other construction requirements, but also can be hinged or made part of the node semi-articulated. column bearing generally fixed support, when necessary, can also be designed to hinge bearings. frame structure can be divided into integral cast, fabricated, cast assembled.

Frame structure of the layout flexibility and easy process to meet the architectural features and a variety of health requirements. At the same time, through rational design, the frame

structure can have good ductility and seismic performance. However, the frame structure to withstand the level of forces (wind loads and horizontal seismic action) capacity less. When the layer of the tree more or larger horizontal force, horizontal displacement of large, often under strong earthquake in as deformation caused by excessive non- structural elements (such as filling wall) damage. Therefore, in order to meet the requirements of the bearing capacity and lateral stiffness, the column sections are higher, both cost building materials, but also reduce the use of space. This makes the framework structure of the building height subject to certain restrictions. At present, frame structure generally used for multi-storey building and not considered earthquake-proof, low-rise high-rise buildings (for example, layers for the 10-story height of 30 meters or less)

2.3 Frame structure of the layout

Multi-storey frame structure of the plane layout is flexible, frame structure in accordance with the loading of the different ways into the following three categories:

(1) Horizontal load-bearing framework of the program to the framework of the main beams as floor beams, floor load borne mainly by the horizontal framework. As the number of horizontal frame less often, the main beam along the crosswise arrangement is conducive to enhance the lateral rigidity of housing. Meanwhile, the main beam along the crosswise arrangement is also beneficial to building ventilation and lighting. However, the main beam section size larger, as the housing needs of a large space, low headroom, and not conducive to vertical pipe layout.

(2) The vertical load-bearing framework of the program to the main frame rails as floor beams, floor load borne by the frame rails. As the beam cross-section small size is conducive to walking through the pipeline facilities, access to higher indoor clearance. However, poor housing lateral rigidity, while the depth scale by the limited length of precast panels.

(3) vertical and horizontal program to the framework of the mixed-load bearing vertical and horizontal program to the framework of the mixed two directions along the vertical and horizontal layout of a framework for both the main beam as the floor beams, floor load from the vertical and horizontal frame beams shared. It is well overall performance.

2.4 The way board section design and construction and reinforcement

Beam around the entire cast for the two-way board, because in both directions by the support component of deformation constraints, block board the role of memory in the dome, so that the moment plate greatly reduced. Referred to in order to take advantage of this favorable factor, standard allows the entire end plate edges and the beam, from the moment the design value reduction under certain conditions. Thickness of not less than two-way plate 80mm. As the deflection is not a separate checking, two-way plate thickness and the ratio of short-span is long

should be satisfied: simply supported plate, continuous sheet. Two-way plate method in accordance with the design theory of elasticity, the calculated number of cross-Chung Cheng moment is reinforced plate number of the central office, close to the board on both sides, their number can be decreased. Considering the construction, the board of both the direction of the edge strip into three. Edge of board in both directions are short for the width of the military side of length 1 / 4, the rest are middle strip. Plate in the middle belt, according to the maximum positive moment across the width obtained within the unit volume with homogeneous steel; in the edge of plate belt, press the middle plate with flat steel plate number within the half width of uniform layout.

2.5 beam and column computing results of manual adjustments to manually adjust

The frame beam reinforcement, which aims to solve the beam crack width gauge and the "strong shear weak bending" problem. mentioned that when the crack width gauge, the first consideration should be given to use large diameter steel reinforced checking of small diameter, such as the crack width is still overloaded, it should increase the beam reinforcement and concrete strength grade, or increase the beam section size, adjusted to meet the code requirements. In order to ensure "strong shear weak bending" can be the following adjustments: First, increase the appropriate end of the beam cross section; second is the appropriate end of the beam stirrups increase the diameter of the spacing encryption; third end of the beam negative moment reinforcement does not enlarge tensile steel beam under the appropriate 1.1 to 1.2 times magnification; Fourth, according to construction requirements of the span> 7m increase in the framework of bent steel beams.

Earthquake Forces, especially the prism columns and large bay, large depth of the side columns, generally in a two-way eccentric compression, while the computer program is under way in two different orientations for the calculation of eccentric compression of plane frame reinforcement. Therefore, in that the reinforcement columns should be adjusted as follows: First, choose the most unfavorable direction of the framework of the calculation can also be calculated in two directions are the direction of the reinforcement value whichever is greater, and symmetrical reinforcement; Second, unilateral control of the direction of reinforcement of at least column number of roots. Fourth, select the well shaped or diamond-shaped stirrup form columns to enhance the stirrups on the concrete constraints; 5 is due to multi-frame Computer generally not considered the basis of thermal stress and differential settlement of the problem, when the level of multi-frame size than the large and the foundation soil for the soft soil or uneven ground, it can then slightly enlarge the framework of the appropriate column reinforcement.

2.6 cycle reduction factor for access

To the framework structure of the cycle and stiffness calculations often ignored the impact of infilled frame. But the actual situation in the infill wall (brick) in the early stages of the involvement of flexible working capability is greater. So that the structure stiffness is greater than the actual calculation of stiffness, the actual cycle less than the calculated period, calculated too small earthquake. Structural design is unsafe. Held that in order to avoid large errors in the design process should be carried out on computing cycles reduction. General, cycle reduction factor of value: When the wall is filled with masonry, the take 0.6 to 0.7; the light block or masonry wall filled with less time, take 0.7 to 0.8; when filling wall for the lightweight wall boards, the take 0.9; no net framework infilled take 1.0. Can be seen that the stiffness of infilled smaller impact on the framework of the cycle of smaller earthquakes in the ability to absorb the weaker.

III Conclusion

As the frame structure with a large space, flexible layout features, meet the people are constantly seeking to use individual requirements. With the continuous development of society and people's material living standards, the framework structure (residential, public buildings) will be greater development. Design of multi-frame structure , the designer should first determine structural feasibility, potential problems encountered in advance to take measures to resolve, and a careful analysis of all results to determine, accurately be applied to engineering after.

In summary, for me, in the final project (a university building), the specification and according to the actual environment, select the component parameters and design parameters. In addition, we understand more about the structure, construction and other design details. by looking at the specifications, magazines and other literature on the building structure, the design of a concrete understanding of the design for the school well.

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