This report analyzes cracks found in the weir box walls of structures 104, 04, and 05. Hairline cracks were observed and determined to likely be caused by thermal contraction/expansion or subgrade settlement. Applied stresses from structural loads and hydrostatic pressure could also be contributing factors. The vertical cracks are consistent with shrinkage and temperature effects. The contractor is advised to monitor the cracks for changes and use an approved repair procedure if the cracks remain stable and under 1/4" wide. Reinforcement and concrete mix design revisions may be needed if cracks widen over 1/4" with vertical displacement.

1. Concrete Crack Analysis Report
Over view
Weir Box Wall-104” Pipe Penetration Section under puddle flange section has crack. As it is
repeated in Weir Box #04 and #05 so CHEC Construction referred engineering for detailed
Analysis for cause finding study.
Evaluation is based on site pictures and drawing #VB-985885-001 provided us for analysis, the
subject crack can be classified as dormant hair line crack. This crack remains unchanged i.e. no
change in depth and width both.
Causes:
(1)Thermal Contraction/Expansion:
Due to temperature changes in inner and outside of wall.
(2)SubgradeSettlement:
Changes in soil moisture contents
(3)Differential Bearing Capacity:
Harder soils under partof the foundation can causestresses as the weir box
wall “settles in”
(4) Applied Stresses:
Forces caused by structureload, hydrostatic pressureof Puddlesection
operated on subjectwall section. Tremendous forces can build up inside the wall
due to applied stresses. When the forces exceed the strength of material, crack
will develop. This causenormally leave a “signature” in the type of crack it
creates. These cracks are of little concern by themselves in nature until concrete
maintain its full strength.
Type and location of crack itself define its nature. The vertical type of crack shown
in pictures attached are caused by shrinkageand temperature. These are mostly
typically fromcorner of structurecausing stress to down side or any other
opening.

2. These reentrant cracks arevery common for the above described situation un less
it shows significantlateral displacement.
Suggestions for Correction:
Contractor can employ severalmethods of reducing the occurrence. The subject
crack is to keep under observation for any lateral displacement for certain period.
If there is no significantdevelopment and width of crack is not exceeded by ¼” in
width, then useapproved crack repairing procedure#CHEC-JIGCC61K-30-GE-MST-
0032 is acceptable and recommended for implementation.
In second scenario if contractor finds width of crack is exceeding ¼” in width along
with lateral displacement in vertical direction, then contractor is recommended to
reviseconcrete mix design and rebar reinforcement details for reconsiderations.