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墙面开裂?部件脱落?你知道这些裂缝的形成原因吗?第1张图片

混凝土结构建筑裂缝意味着什么?
What Do The Cracks in Concrete Structures Mean?

由专筑网李韧,曹逸希编译

裂缝可以根据其开裂程度划分为结构性裂缝和非结构性裂缝,是建筑行业严重的问题,严重影响美观、耐久性以及建筑结构特性。任何地方都有可能产生裂缝,但主要产生的地点一般为墙体、梁、柱子以及楼板,而且引发裂缝的原因通常是由于设计中没有考虑到的压力而造成的。非结构性裂缝程度较轻,一般来说,它们通常位于结构表面。这些开口较为细长,一般不会超过0.5毫米,甚至有时人的肉眼都不一定能观察到它们。因此,这些裂缝并不意味着结构有问题,但如果处理不当同样也会导致严重的后果。重要的是,使用者应当注意到随着时间的变化,这些裂缝程度是否加剧,因为结构性裂缝的最初状态也是呈现这样的形式。

在裂缝的初期如果不予以重视,那么也许会造成深度达到0.5毫米至1.5毫米深度的开口,此时的裂缝则十分清晰,这已经是一个非常危险的状态,因为已经损伤到结构部件,甚至可能影响到建筑的安全。

然而,开口大于1.5毫米的裂缝,此时的深度已经足够让空气和水蒸气渗透到结构内部,此时使用者应当立即重视,因为这很可能会腐蚀材料中的电枢或者造成更深层次的化学反应。使用者应当在了解原因之后,做出相应的对策。

以下是一些容易造成裂缝的原因:
  • 非预期的结构损坏:由于设计计算不当和荷载过重所引起;
  • 非人为因素引起的结构变化:建筑一旦建成,就要面临着许多问题,例如由地心引力引起的地基沉降,另外,建筑不同部分的地基也不同,因此某个部分的地基沉降程度也许会多于另一部分,这样便会产生裂缝,在建筑中,我们通常称它为“沉降缝”;
  • 支撑构件的过早拆除:在建筑的施工阶段,如果要拆除支撑部件,必须等待结构部件具有相应的沉重能力。例如,梁板的支撑部分至少应该保持28天;
  • 部件受热热膨胀:建筑的不同部分或多或少都要经过太阳的直射,因此有的部件也许会更快地形成热收缩,从而引起裂缝,例如由于太阳的照射所产生的楼板开裂;
  • 材料的收缩:在结构部件的涂层和混凝土层中,由于化学反应或蒸发的原因会造成水分流失。例如,在干燥期的油漆、灌浆砂浆,在接收到过多的阳光抑或是不同的材料之间发生的化学反应,造成一定的水分流失,就会形成部件的收缩,造成尺寸的轻微变小,最终产生裂缝;
  • 渗水:当结构表面的构造层的防水步骤做得不够充分时,就会造成水蒸气进入结构部件中,形成一定的化学反应,从而增加钢筋的直径,这将导致混凝土具有压力,最终形成裂缝。这样会导致混凝土的脱落,将金属构件暴露在空气当中,快速被腐蚀;
  • 轻微震动和连续震动:地基的抗震设计相对欠缺,由于街道、电梯、周边建筑、地铁等大型交通的影响,会造成不同程度的震动,从而造成结构开裂;
  • 钢筋混凝土配方的失误和不当的应用方式:混凝土构成材料的比例不同,也会影响结构的抗压强度,因此混凝土各项原料的配比应当尽量精确,因为这是建筑具有强大荷载能力的基础。过多或过少的砂浆以及其他不同的使用方式,都有可能造成墙面的裂缝。

让我们来了解一下以下开裂现象的原因:

Cracks, which could be classified according to their thickness as fissures or fractures, are serious problems in the construction industry that can negatively affect aesthetics, durability and, most importantly, the structural characteristics of a project. They can happen anywhere, but occur especially in walls, beams, columns, and slabs, and usually, are caused by strains not considered in the design.
Fractures are usually of lesser severity. In general, they appear more on the surface of the structure. They are narrow and elongated, with openings less than 0.5mm. Sometimes they are not even visible to the naked eye. Generally, they do not imply structural problems but can lead to more serious consequences. It is important to note if the fracture grows over time or remains stable, because it may be the first stage of a fissure.
If not looked after, the next stage or a fracture could lead to deeper openings of 0.5 to 1.5mm. They can be seen without difficulty and are much more dangerous than the fractures because the rupture of the structural element has already occurred and can affect the safety of the part.
Fissures are slits with openings greater than 1.5mm, deep and well highlighted. With this magnitude, it allows air and water to penetrate the interior of the part, which requires immediate attention. They may cause corrosion of the armature or undesired chemical reactions in the material. One should not simply close them without researching the causes and provide the solution to the problem that caused it.

The main reasons that may be related to the occurrence of these cracks are the following:

  • Unplanned structural impairment: due to poorly designed calculations and inadequately overload predictions;
  • Unforeseen accommodation of constructive elements: Whenever a building is built, there is a settlement of the ground, a settlement to a greater or lesser degree. Thus, depending on how the foundation was made, one part of the construction can yield more than the other and with that displacement, it could cause cracks, known in the technical area as differential repression;
  • Early removal of shoring elements: during the construction phase it is necessary to wait for the structural parts to acquire a minimum resistance before the shoring is removed. For example, slabs and beams should remain supported for at least 28 days;
  • Thermal expansion: some parts of the building are more or less exposed to the sun during periods of the day, thus dilate or retract more than others, which can cause cracks, such as a slab that dilates with the sun causing the cracks;
  • Material retraction: it is the loss of water by chemical reactions or evaporation in the coating layers and in concrete pieces such as slabs, pillars, and beams. For example, paint in the drying period, grout mortar, slab upon receiving too much sun and chemical reactions of the cement, these occur when there is the loss of moisture and thus the parts retract, their size is reduced and can arise cracks;
  • Infiltration: when there is a leak or poor waterproofing of the slab or reservoirs of water enter the part, in the case of concrete the water will penetrate and will gradually reach the iron armature causing oxidation and, consequently, increasing the diameter of the bars, which will result in the pressure of the concrete and hence the beginning of the cracks. The consequence of this will be the fall of parts of the concrete, leaving the ironwork exposed, accelerating the process of corrosion;
  • Vibrations and tremors: poorly designed foundations along with excess traffic on the street, elevators, nearby buildings, and subway are some reasons for continuous vibration to cause cracks;
  • Defects in the formulation of the product and errors in the application: The concrete traces, represented by the proportion of the different materials that compose it, must be very well dimensioned, as it is fundamental to obtain the resistance to withstand the expected loads. A mortar with a lot of or little water, or being used after its period of handle, can cause numerous cracks in the coating of a wall.


See below some of the causes for cracking:


正向箍筋数量不足导致梁开裂|Cracks on beam due to insufficient positive reinforcement

墙面开裂?部件脱落?你知道这些裂缝的形成原因吗?第2张图片
© Matheus Pereira

可能的原因:
  • 纵向箍筋数量不足;
  • 正向箍筋锚固不足;
  • 结构荷载超过预期。

Probable causes:
  • Insufficiency of longitudinal reinforcement;
  • Insufficient anchorage of positive reinforcement;
  • Overloads than predicted in structural calculation.


负筋数量不足导致梁开裂|Cracks on beam due to insufficient negative reinforcement

墙面开裂?部件脱落?你知道这些裂缝的形成原因吗?第3张图片
© Matheus Pereira

可能的原因:
  • 纵向负筋数量不足;
  • 负筋锚固不足;
  • 结构荷载超过预期。

Probable causes:
  • Insufficiency of longitudinal reinforcement (negative);
  • Insufficient anchorage of negative reinforcement;
  • Overloads than predicted in the strucutral calculation.


由于剪力导致的梁裂缝|Cracks on beam due to shear

墙面开裂?部件脱落?你知道这些裂缝的形成原因吗?第4张图片
© Matheus Pereira

可能的原因:
  • 横向钢筋数量不足;
  • 混凝土阻抗力不足;
  • 结构荷载超过预期;
  • 箍筋错位。

Probable causes:
  • Insufficiency of transverse reinforcement (stirrups);
  • Low resistance concrete;
  • Overloads than predicted in the structural calculation;
  • Misaligned stirrups.


混凝土收缩引起的梁裂缝|Cracks on beam due to retraction of concrete

墙面开裂?部件脱落?你知道这些裂缝的形成原因吗?第5张图片
© Matheus Pereira

可能的原因:
  • 混凝土过于干燥(不恰当地操作导致水分过早蒸发);
  • 由于温差引起的收缩;
  • 水泥连接不足;
  • 混凝土密度不足。

Probable causes:
  • Premature concrete drying (improper curing causing water evaporation);
  • Thermal contraction due to differences in temperature;
  • Inadequate water-cement connection;
  • Inadequate densification or badly vibrated concrete.


由于地基压力导致柱体开裂|Cracks on the pillar due to repression at the foundation

墙面开裂?部件脱落?你知道这些裂缝的形成原因吗?第6张图片
© Matheus Pereira

可能的原因:
  • 地基压力过大;
  • 地基荷载高于预期;
  • 混凝土阻抗力不足。

Probable causes:
  • Foundations stress;
  • Load higher than expected;
  • Inadequate resistance concrete.


由于箍筋不足而导致柱体开裂|Cracks on the pillar due to insufficiency of stirrups

墙面开裂?部件脱落?你知道这些裂缝的形成原因吗?第7张图片
© Matheus Pereira

可能的原因:
  • 箍筋数量不足;
  • 纵向箍筋超过荷载;
  • 纵向箍筋弯曲。

Probable causes:
  • Stirrups insufficiency;
  • Overload of the longitudinal reinforcement;
  • Buckling of the longitudinal reinforcement.


由于支撑强度不足而导致的楼板开裂|Cracks on slabs due to insufficient positive reinforcement

墙面开裂?部件脱落?你知道这些裂缝的形成原因吗?第8张图片
© Matheus Pereira

可能的原因:
  • 有效支撑力不足;
  • 荷载强度超过预期估算;
  • 钢筋锚固不足。

Probable causes:
  • Insufficiency of positive reinforcement;
  • Overload than predicted in structural calculation;
  • Insufficient anchorage of the reinforcement.


由于荷载过大从而导致楼板开裂|Cracks on slabs due to excessive overload

墙面开裂?部件脱落?你知道这些裂缝的形成原因吗?第9张图片
© Matheus Pereira

可能的原因:
  • 混凝土厚度不足;
  • 结构承重超过预期估算。


Probable causes:
  • Insufficient concrete thickness;
  • Overload than predicted in structural calculation.


门窗角上的裂缝|Cracks on the corner of windows and doors

墙面开裂?部件脱落?你知道这些裂缝的形成原因吗?第10张图片
© Matheus Pereira

可能的原因:
  • 荷载过大;
  • 过梁或窗台搭接不当导致无法承重。

Probable causes:
  • Unplanned overloads;
  • Nonexistent or poorly executed lintel and sill.


外墙砌体开裂|Cracks on masonry of facades

墙面开裂?部件脱落?你知道这些裂缝的形成原因吗?第11张图片
© Matheus Pereira

可能的原因:
  • 砌体连接时间过早;
  • 连接方法不当;
  • 支撑墙体的梁板弯曲变形。

Probable causes:

  • Premature connection of masonry
  • Deficiency of the connection method;
  • Bending deformations of slabs and beams that support the walls.


立面斜裂缝|Inclined cracks in facades

墙面开裂?部件脱落?你知道这些裂缝的形成原因吗?第12张图片
© Matheus Pereira

可能的原因:
  • 剪应力

当我们如果观察到,例如梁、楼板或墙壁等结构构件出现裂缝时,我们需要与专业的工程师沟通商量,如果条件不允许,我们也应该尽可能与其他专业人士联系,从而才能正确地了解到问题所在,并且进行后期的维修与配件更换。

Probable causes:
  • Shear stress

It can be said that when observing the appearance of cracks in structural elements such as pillars, beams or slabs or even in walls, it is necessary to communicate the problem to the calculating engineer or, if it is not possible, to call another qualified professional, in order to establish an accurate diagnosis and to determine the alternatives for correcting the defect in order to provide the necessary repairs.

        
出处:本文译自www.archdaily.com/,转载请注明出处。

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