Foundation, Concrete and Earthquake Engineering

Factors Controlling Tolerances in Concrete Construction

We were discussing about tolerances in concrete construction. In the previous post, we have listed factors that influence tolerances; now we will discuss each factor:

a. Structural function and strength requirements

The structure should be strong and sufficient safety is provided which reflect design assumptions. The shape and size should be accurate enough for the job to satisfy design and construction requirements.

b. Esthetics:

The structure should satisfy expectation of owner and designer as well satisfying all requirements of appearance.

c. Economic feasibility:
Misalignment of ducts provided in concrete for post-tensioning

The cost of construction or any precast/prestressed products depends largely on tolerance limit. Construction method is also equally important. It is obvious that tight tolerance associated with higher cost involvement.

d. Relationship of components

The tolerances provided in construction may be for individual part or for global structure. In case of individual tolerance, it depends on following terms of adjacent parts:

1. Materials of adjacent units

2. Connection and joint details

3. Applicability of tolerances into critical dimensions

e. Construction techniques

The feasibility and practicability of specific tolerance, in this regard, depends on

-available craftsmanship

-available technology

-available materials

f. Material properties

In prestress member, camber is a well know term and shrinkage is a global term in concrete members. In determining deflection in design stage difficulties arisen by these two term and should be considered while determining tolerances.

g. Compatibility

Compatibility between architectural details and expectation of finish should be fixed based on expected construction method. The relation between two should include in the tolerances in concrete construction.

h. Job conditions

This factor includes job conditions and situations. Clear specifications should be provided from design office where sensitive tolerances are required that represents requirements of project site.

i. Measurements

Some bench marks and control points are provided as a reference to verify tolerances of different parameters. This are achieved by mutual understanding and they are maintained undisturbed until final acceptance and completion of project.

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