Concrete construction practices: construction joints are generally provided at which of the following positions or conditions?

Introduction / Context:
Construction joints are planned discontinuities in concrete work to accommodate interruptions. Proper placement avoids structural weakness and ensures load transfer.

Given Data / Assumptions:

• Monolithic construction is ideal but often impractical.
• Joint positions are chosen to minimize adverse effects.

Concept / Approach:
Joints should be at locations of minimum stress (low BM and SF), at support points, or at natural breaks (like window sills). In large continuous structures, spacing rules like 18 m apply.

Step-by-Step Solution:
(a) Walls: sill level joints are convenient and aesthetic.(b) Structural members: joints at low stress regions are safe.(c) Supports: natural cut-off point.(d) Long structures: spacing provides control.Thus, all apply.

Verification / Alternative check:
IS 456 provides guidance for joint placement at low stress zones and architectural breaks.

Why Other Options Are Wrong:

• No option is wrong; all are valid placement criteria.

Common Pitfalls:

• Providing joints at high stress regions, leading to cracks or leakage.

Final Answer:
all the above