7) Conclusion

The findings from each preceding task discussed should be summarized in this section of the report. The findings should include a discussion of the condition of the structure and the feasibility of the rehabilitation. The
recommendations must address the following topics:

1. Action plan: The recommendation should clearly point out an appropriate course of action
2. Cost estimates: Project costs often influence every aspect of a recommended rehabilitation plan and while not necessarily controlling the final recommendations, can have a major influence on them.
3. Scheduling :  Project schedule may be determined by the urgency of the rehabilitation needs, the availability of funds, the effects on ongoing operations, and the optimal construction conditions.
4. Determining constraints and feasibility:  Rehabilitation often involves the constraints associated with working around existing operations. Special considerations are warranted for construction operations that produce dust, noise, odor, vibrations, or involve hazardous materials. Site access and materials handling problems should also be considered. Special project planning meetings are often helpful in determining the most appropriate way of handling these constraints. It is of critical importance to insure that any constraints mandated by the owner be considered and incorporated into the rehabilitation plan.

Reference:Tony C. Liu(1999):Guide for Evaluation of Concrete Structures

Prior to Rehabilitation

6b) Detail in evaluate step in concrete structure

Review of Engineering Data

• A thorough review of all of the pertinent data relating to a structure should be accomplished early in the evaluation process. To understand the current condition of the concrete in a structure, it is imperative to consider how design, construction, operation, and maintenance have interacted over the years since the structure was designed and constructed. Sources of engineering data which can yield useful information of this nature include project design memoranda, plans and specifications, construction history reports, as-built drawings, concrete report or concrete records (including materials used, batch plant and field inspection records, and laboratory test data), instrumentation data, operation and maintenance records, and periodic inspection reports. Instrumentation data and monument survey data to detect movement of the structure should be examined.

Condition Survey

• A condition survey involves visual examination of exposed concrete for the purpose of identifying and defining areas of distress. A condition survey will usually include a mapping of the various types of concrete deficiencies that may be found, such as cracking, surface problems (disintegration and spalling), and joint deterioration. Cracks are usually mapped on fold-out sketches of the monolith surfaces. Mapping must include inspection and delineating of pipe and electrical galleries, filling and emptying culverts (if possible), and other similar openings. Additionally, a condition survey will frequently include core drilling to obtain specimens for laboratory testing and analysis. 

Reference:Stowe and Thornton (1984), American Concrete Institute (ACI) 207.3R, and ACI 364.

Condition Survey Report:

The results of the entire investigation should be summarized in a final report. This report generally includes

a brief description of the following basic areas addressed during the evaluation process:

a) Purpose and scope of investigation

b) Existing construction and documentation

c) Field observations and condition survey

d) Sampling and material testing

e) Evaluation

f) Findings and recommendations

The report should summarize the results of the strength evaluation of the structure. All assumptions made and methods used in the evaluation process should be clearly documented. A brief description of each repair

alternate (Corps of Engineers 1986) or strengthening method studied, along with sketches showing typical

details, cost estimates, and the impact of the repair method, should be included.

6a) Detail in evaluate step in concrete structure

1) VISUAL INSPECTION
a) Introduction:

• Visual testing is probably the most important of all non-destructive tests. Visual features may be related to workmanship, structural serviceability, and material deterioration and it is particularly important that the engineer is able to differentiate between the various signs of distress which may be encountered. These include for instance, cracks, pop-outs, spalling, disintegration, colour change, weathering, staining, surface blemishes and lack of uniformity. 
• Extensive information can be gathered from visual inspection to give a preliminary indication of the condition of the structure and allow formulation of a subsequent testing programme. The visual inspection however should not be confined only to the structure being investigated. It should also include neighbouring structures, the surrounding environment and the climatic condition. This is probably the most difficult aspect of the whole structural investigation or any diagnostic works since what appears obvious to one may not be so to another. The importance and benefits of a visual survey should not be underrated. Often the omission of what appears to be insignificant evidence can lead to a wrong conclusion being made. 

b) Before any visual test can be made, the engineer must peruse all relevant structural drawings, plans and elevations to become familiar with the structure. Available documents must also be examined and these include technical specification, past reports of tests or inspection made, construction records, details of materials used, methods and dates of construction, etc.

c) Visual inspection is not confined to the surface but may also include examination of bearings, expansion joints, drainage channels and similar features of a structure. Any misuse of the structure can be identified when compared to the original designed purpose of the structure.

d) For existing structures, presence of some feature requiring further investigation is generally indicated by visual inspection, and it must be considered the single most important component of routine maintenance. It will also provide the basis for judgements relating to access and safety requirements when selecting test methods and test locations.

e) A careful and detailed record of all observations should be made as the inspection proceeds. Drawings can be marked, coloured or shaded to indicate the local severity of each feature. Defects that commonly need recording include:

•  cracking which can vary widely in nature and style depending on the causative mechanism
•  surface pitting and spalling
•  surface staining
•  differential movements or displacements
•  variation in algal or vegetative growths
•  surface voids
•  honeycombing
•  bleed marks
•  constructional and lift joints
•  exudation of efflorescence.

example sketches of typical defect of typical defect found by visual inspection:

Cracks due to differential settlement of central column.

Cracking in columns and beams due to an earthquake.

Reference:GUIDEBOOK ON NON-DESTRUCTIVE TESTING OF

CONCRETE STRUCTURES

5) Sample picture of structural defect that need to investigate

(A). Relative movement of a concrete pier caused by the expansive forces generated by the adjacent retaining wall

B) Expansion of concrete causing extrusion of sealing material and spalling at the edge of

 sections of a five-year-old concrete pavement

C) Relative movement and associated spalling between a pier block showing  cracking 

and an adjacent deck slab causing spalling of concrete and extrusion of sealing material along the joint.

D) Cracking and spalling of concrete due to ASR in a 20-year-old median highway barrier; 

freeze-thaw action has greatly influenced the extent of deterioration.

4) Flow diagram of progressive screening

Reference: REHABCON, 2004

3. Steps in a typical evaluation of a concrete structure

The more precise steps in a typical evaluation of a concrete structure are given by Peter Emmons (1993):

1. Visual inspection (walk-through)

2. Review of engineering data
     i. Design and construction document
    ii. Operation and maintenance record
    iii. Concrete (including materials used) records
    iv. Periodic inspection report

3. Condition survey
    i. Mapping of the various deficiencies
   ii. Monitoring
  iii. Joints survey
  iv. Sampling and testing
   v. Nondestructive testing
  vi. Structural analysis


4. Final evaluation

5. Condition survey report

2. Monitoring Concept and Performance

klik on the chart to enlarge the picture

1. Structural evaluation/investigation process by proposing the steps in a typical of a concrete structure.

Concrete


Concrete is a construction material with many attributes and disadvantages that should be carefully designed for good construction and rehabilitation work. Some defective concrete can be attributed to the addition of reinforcement steel since corrosion of imbedded steel is one of the most frequent causes of concrete damage. Concrete is highly alkaline with electrical resistant, which gives imbedded steel some corrosion protection. However it is a porous material and over time is not very resistant to acidic chemicals. Deicer chlorides and also chemical reactions within the concrete destroy the protection. In addition to other means there are two types of corrosion inhibitors attracting interest for concrete repairs. One, calcium nitrate, an admix for fresh concrete that has been used for several years with good results. Other inhibitors are applied externally on hardened concrete. They function by migrating through the concrete covering the reinforcement steel. Their effectiveness however is uncertain for the long term.


Evaluation

A thorough and logical evaluation of the current condition of the concrete in a structure is the first step of any repair or rehabilitation project. It mean,when the condition of a structure indicates that major repair or rehabilitation is probably necessary, a comprehensive evaluation of the structure should be conducted to determine the scope of the work required. Such an evaluation could include the following: 

a) a review of the available design and construction documentation; 

b) a review of the operation and maintenance records; 

c) a review of the instrumentation data; 

d)a visual examination of the condition of the concrete in the structure; 

e) an evaluation of the structure by nondestructive testing means; 

f) a laboratory evaluation of the condition of concrete specimens recovered from the structure; 

g) a stress analysis; and a stability analysis of the entire structure. 

Investigation

Collection and evaluation of information through inspection, document search, load testing and other testing.

Introduction

This blog is for the first assignment for "BFP4043 Structure Repair & Rehabilition" subject under Puan Noorli Ismail.

I got the assigmnet no 14 which title:

Structural evaluation/investigation process by proposing the steps in a typical of a concrete structure.

Name:Siti Noraisah Bt Md Shfie

Matrik: Af070106

Section: 4

Submit:28/1/2011