Buildings require great designs and sound construction practices to be able to withstand the disastrous forces of an earthquake. There are several common designs and construction mistakes one can avoid to keep a building intact and minimize the impact of an earthquake on it.
For instance, flaws like storey, short columns, inadequate reinforcement detailing, non-structural damage, discontinuous force resisting system, poor quality concrete, inadequate detailing, and inferior materials act as a trigger for earthquake to take down a building.
These designs and construction mistakes have been observed and noticed repeatedly in the majority of earthquake-hit areas. Therefore, it is necessary to take these errors into consideration during the design and construction phase of structures.
10 Construction Mistakes to Avoid
1. Soft Storey
Formation of storey in a structure is a common mistake that causes heavy damages to buildings in the event of an earthquake. Generally, building irregularities are divided into two major classes namely plan and vertical irregularities.
The latter is further categorized into three types which include discontinuity of vertical structural system, strength irregularities, and rigidity irregularities. When the ratio of relative displacement of a floor to the above floor is different by 1.5, the rigidity irregularities occur (soft storey).
It is observed that soft storey with masonry infills suffers fewer damages compared to storey without masonry walls between columns of that particular storey. So, the possibility of damages increases when there are masonry infills on the upper storey but not on the soft storey.
2. Short Columns
The design and construction of short columns or formation of short columns due to several reasons in structures, especially in seismic prone regions, have been a major cause of building damages. This claim is proved through inspections and investigation of structural damages in various earthquake-hit areas around the world such as in 2011-Van Earthquake in Turkey.
Short columns are formed due to non-load bearing brick walls. This wall restricts lateral displacement of the frame and increases its rigidity. Differences in column lengths of the same storey create a brittle fracture in the columns. Also, the voids left between the columns in infilled walls is another cause of short column formation, Fig. 3.
3. Inadequate Reinforcement Detailing
Several reinforcement-detailing mistakes have been observed to be the cause of damages in earthquake-prone areas. For instance, beam-column joint with inadequate detailing (Fig. 5 and 6), inadequate lap splice (Fig. 7), and inadequate tie reinforcement (spacing and bars sizes), Fig. 8. These issues can be prevented by the strict adherence to the code provisions and by proper monitoring of construction works.
4. Non-structural Damage
By and large, non-structural damages do not endanger the stability of a structure. However, they can be a source of falling hazards, for instance, cracking and overturning of partition walls and parapets, falling of plaster and ceilings. A structure needs to have adequate rigidity to minimize the second-degree moments as much as possible and to reduce the non-structural damage.
5. Discontinuous Force Resisting System
All vertical elements in the lateral-force-resisting system shall be continuous to the foundation otherwise catastrophic damages such as shown in Fig. 10 can happen. It can be seen that the ground floor has completely collapsed under the load of the floor just above it due to the disproportionate transfer of loads by the resisting system.
6. Strong Beam-weak Column
Strong beam-weak column is another common mistake that leads to the failure of structures in various earthquake-hit areas. In the case of weak column-strong beam, the column fails prior to the beam and progressive collapse would be highly possible.
However, when columns are stronger, the beams fail first and the entire safety of the structure would not be in danger. The repair of the beams in these circumstances would be feasible.
7. Inadequate Detailing
There are certain detailing mistakes which may lead to damages to a building during earthquakes, for instance, inadequate provisions for drainage, abrupt changes in section, inadequate expansion joints, and inadequate provision for deflection. Fig.12 exemplifies the influence of inadequate detailing.
8. Poor Quality Concrete
The application of poor-quality concrete is yet another mistake that could lead to structural damages during earthquakes. Low-strength material which has no or very less tensile and shear strength is more prone to damage.
9. Inferior Materials
Unreinforced masonry made of stones, adobe or hand-made clay bricks, is the type of housing construction system that has exhibited the largest damage. Inferior materials are inherently weak and suffer damages greatly under earthquake attack. The use of some type of reinforcement is probably responsible for the single most effective change in reducing earthquake damage of masonry constructions made with distinctly different materials.
10. Densely Populated Area
Construction in already very densely populated areas leads to a massive loss of lives and property in the event of an earthquake.