Foundation, Concrete and Earthquake Engineering

Critical Construction Process Requiring Good Workmanship

In reinforced concrete frame construction, it is very important to have qualified work crews with appropriate experience and competent workmanship. It is also very important to have a feasible and well-thought construction sequence to let the crews perform their tasks in a proper and timely manner. The construction crews are the last, but vital link, in the construction process.

The design engineer and the architect play important roles in ensuring that the design is feasible and can be understood by construction crews.

The design engineer should keep the structural configuration and detailing of the structural system and its sub-elements as simple and straightforward as possible. It is good practice to use standard or typical detailing as much as possible. Of course, it is the responsibility of the whole building team --from the architect and the design engineer to the field crews-- to build a good quality building.

The key processes where workmanship is critical in construction are:
1) Steelwork: the steelwork has to result in reinforcement layouts per the specifications given in the structural drawings. Reinforcing elements should be clean and
should not have any dirt or oil on them (see Figure 1).

2) Formwork: to be able to cast reinforced concrete elements properly, good quality forms need to be built. This requires use of clean, leak-proof and tightly constructed formwork systems, characterized by adequate stiffness and strength. Where necessary, proper falsework may need to be incorporated into the formwork construction to support the forms.

3) Proper placement of steelwork into the forms: reinforcing steel assemblies need to be placed and secured within the forms in such a way that the design specifications (such as minimum concrete cover thickness) have been met. This would prevent future corrosion of the reinforcement and spalling of the concrete. The steelwork should not be displaced or distorted when fresh concrete is placed into the forms.

4) Concrete work: transportation, handling, placement and consolidation of fresh concreteshould be done properly. Accumulation or loss of water, or segregation of aggregate in the concrete mix should be avoided as much as possible. If such alterations of the concrete matrix take place, the concrete mix should be reconstituted before placing the fresh concrete into forms. Fresh concrete should be poured into the forms and properly distributed (consolidated) within and around the steel reinforcing elements. Use of vibrators or other instruments that enhance consolidation of the concrete within forms is recommended. It is extremely important to have good bond

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