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The following are collection reviews from the MCS team members for your reference. Shall there be any query in regards to the review(s), kindly contact the team member(s) for clarification.

Is Site Investigation sufficient to tell you stories about a construction site?

posted Jul 28, 2022, 6:15 AM by jeffery jim


No! Site Investigation (SI) which includes field testing, instrumentation and boreholes where soils are extracted is not sufficient to tell you the complete story of a construction site. There is a need for a geophysics study for a construction site which is extremely sensitive to geotechnical and geological changes.
In one of my latest work in integrity study involving three dams in Sabah requires geophysics. What information which are not conveniently available in SI and instrumentation? First of all, water table and/flow net are not available in SI except for possible correlation and extension. None of these are deterministic by nature and hence, electrical resistivity tomography (ERT) will indicate the actual profile which usually are heuristic in nature. Soil packing and floaters can be determined in ERT which involves probes in a setup which runs in actual section.
My recommendation would be having all four tests conducted. These are complimentary to each other and more data can be interpreted with less assumptions. It is essential to have more data in order to assist in proper literature and design philosophy so that information can be use in determining the optimum design within project cost limit. Ground probe radar can be use but it is not as accurate as ERT and much suitable for utility detection works.
If you need any geophysics work in Sabah for construction work, kindly message me for more information and proforma.
Remark: The photo below indicates a section of ERT which me and my associate worked on for slope construction. A professional engineer and a professional geologist is a must when interpreting result and experimental test simulation through modelling. The other one is a photo of ERT setup for risk assessment studies on 3 dams.

No photo description available.

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Trial Mix and Designed Mix

posted Jul 28, 2022, 6:12 AM by jeffery jim


Trial mix and designed mix are two of the most important essence in quality assurance (QA) for concrete which I have spoken many times previously. The gist to this exercise is to acquire statistical understanding of the concrete that shall be used for the construction in the sense of its physical properties and the narrative it provides during test which can be use during quality control (QC) during construction and/or execution. Among the important and essential information which can be use to overrule the standard specification (SP) is the concrete setting time. It takes precedence when determining the slump of concrete after 45 minutes or one hour as stipulated in the SP as well the allowed extension of time for the concrete to show its behaviour during stiffening and curing period.
2. The concrete usually will not start to cure after four hours and this can be determine based on time recorded during trial mix and temperature change aside from slump change. For the first four hours, the concrete will start to stiffen and it is a good practice to limit of time where additives can be applied to prolong the workability before stiffening which further reduce workability indicated by slump test. At this period of time, the concrete will gradually increase in temperature from room temperature to 40 up to 60⁰C, depending on other admixtures added (such as silica fumes and etc.) The increase of temperature above 40⁰C means that the concrete start to stiffen and hot joins are no longer allowed. Here, we can establish the relationship of workability and stiffening and time to prolonged the allowable hot joins for concreting work apart from dosing the plasticizer of the concrete as long as it does not increase to the limit of water/cement (W/C) ratio as indicated in normative references.
3. Trial mix and the approval of design mix also cover another QC issues which many have not taken into consideration, which is the phenomena of plastic shrinkage. After three to four hours into concrete pouring, concrete in a trial box, pushcart or wheelbarrow should be observed. This is an important stage of the QA works when conducting trial mix which many have not anticipate and most time, leftover concrete are discarded. The observation made on these samples will provide further information about the bleeding formation, expansion and evaporation rates. Capillary pressure can be monitored to understand the occurrence of plastic shrinkage where both are growing exponentially in a similar rate. Here, this observation will indicate the exact time when concrete curing via hessian method can be determine especially for structure member's with large surface exposed to element.
4. When another sample box which can be done to increase understanding of cracks developed by plastic shrinkage, reinforcement bars can be introduced to replicate the actual event at site when heat, wind, humidity are interacting with concrete and steel reinforcement bars' thermal expansion. Bleeding occurs very close to reinforcement bars and the outcome is usually crazing cracks which is almost parallel to reinforcement bars location.
5. I hope this brief write-up will provide you greenhorns a new perspective on increasing the QA Plan during the trial mix. Although the concrete may achieved target mean strength on the 28th day, it may need to revamp and redo to suit if plastic shrinkage is an issue. For most JKR contract, the typical requirement for W/C ratio will be under 0.50 and most time with the advances of admixtures, W/C ratio can further reduced to 0.40. Nevertheless, this does not mean lower W/C ratio provides durable concrete. It is commonly known lower W/C means less air voids and concrete will be robust against ingression of detrimental agents and elements. The formation of plastic shrinkage is a dire concern when compare to air voids as cracks are located very close if not provide direct access to the reinforcement bars. As a QAQC manager or engineer, you have to move along the limits or boundaries set in the literature to have a better concrete for construction purposes.

May be an image of text that says "Concrete surface Rebars Water channels Evaporation rate Bleeding water (a) Bleeding water Tensile forces F. (b) Plastic Shrinkage Cracks Dry Surface FF Wet Surface Tensile strength S. (c)"

Value Engineering in QAQC: Let's Talk about Overruling Standard Specifications

posted Jul 28, 2022, 6:11 AM by jeffery jim


Overruling the specification? How dare you overrule a standard specification (SP) set by the Client and binded as part of the Contract? You are not the Superintending Officer and how can you take charge of overruling?
2. These are typical questions by many engineers who failed to see beyond their responsibilities. The question is not about overruling but what can be done during quality assurance (QA) stage which will assist decision when it comes to quality control (QC) stage. What miscellaneous information can be use as parameters, determinants, and/or constants when analyses are conducted when issues arise during construction stage? Here is the trade-off for an engineer to plan from the early stage of any construction based on previous projects and lessons learned.
3. Updates: The SP is a reference point which comes with many narratives and usually backed with other normative references. In this case, most of national level specification allows clauses in the SP to be overruled by latest national and international normative references when these are in-place. This can be seen in JKR's Standard Specification for Building Works.
4. Discretion: Apart from latest normative references, the SP allows the Consulting Engineer to apply his professional decision in making proper call when it comes to executing work. This is the case which creates a lot of confusion for engineer. Some will take it with pride and distinction and allow for good practices. On the other hand, this usually causes many engineers to be uneasy to decide and refrain from making changes for fear of noncompliance.
Overruling part(s) of the SP could be something which is benefiting for QAQC and part of the concept in establishing value engineering. The adoption of new specification(s) may reduce one of the three elements in construction; cost, time and quality. This creates value! It allows for robust and durable structures to be built and comply with latest standard requirements. It is also a compelling method of increasing initial testing for more data part of validating one's moves and discretion on certain issue based on statistical analyses.
6. Have you overruled any standard specification in a project?

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Concrete Slump Test

posted Jul 28, 2022, 6:09 AM by jeffery jim   [ updated Jul 28, 2022, 6:09 AM ]


As Civil Engineer, this is one of the most common tests that one will have to go through. Nevertheless, it is dumbfounded that some engineers could not understand what the reading from this test renders.
The Concrete Slump Test is one of the in-situ concrete tests which will be done before concrete is discharged in-situ. This test is governed by BS EN 12350 Part 2 and the older reference would be BS 1881 Part 102. There are less than 10 pages and it would make many wonders why some cannot comprehend such a simple test.
Question: What is the difference between S5 slump and collapse? (This question was posed by a consulting engineer from either Malaysia or Myanmar working in Singapore; a developed nation.)
Before we go into details about this test, it is good to read the normative references and the literature behind this test. The standard specification mentioned clearly that this test is to be conducted at the site to indicate the workability of the concrete based on trial mix.
If the concrete is designed to have a high slump and designed as a tremie concrete, then it supposes to achieve the desired slump assisted by admixture(s). In this case, it supposes to be under the category of S4 or S5 which is categorized as concrete and indicates collapsed shape when the test was conducted. The design mix was done in such a manner so that high workability will allow concrete to flow easily when using a pump.
Slump range are as follows;
S1 (10-40mm)
S2 (50-90mm)
S3 (100-150mm)
S4 (160mm-210mm)
S5 (>210mm)
The importance of design mix and trial mix procedure will assist the engineer at the site to check compliance of delivered concrete. With a high slump range, it highlights the potential that the concrete can be tempered with water (usually) to ensure it is not hardened or stiff before being discharged.
None of the literature rejects the condition of total collapse or S5 as a fail or rejects or non-compliance. It is up to the discretion of the engineer to interpret the condition of the slump. It is mind-blowing to hear a consultant insisting on a true slump shape when it is designed as a tremie concrete. There is no way that a slump intended to be at 210mm to have true slump shape with a balance of 90mm (when the cone bucket is 300mm).
Nevertheless, the trick here is for engineers to exploit when it comes to shearing of the slump. If the slump collapses in a uniform shape, there will be no problem unless there is a sign of potential shearing based on displacement and spread of the concrete.
It is like trying to find a true slump for grout when testing for its workability. It is futile if one obstinate engineer tries to conduct such tests with high workability. For that reason, Flow Cone and Flow Trough tests are introduced for highly fluid kinds of cementitious products. In this case, it is similar to the concrete slump test. It does not mean the product failed to comply with standard specification which stipulates the required characteristic strength. Workability only indicates the suitability for concrete application and compliance to the design mix and trial mix.
I hope this will help young and fresh engineers from making unnecessary blunders at construction site.

May be an image of text that says "TRUE ZERO COLLAPSED SHEAR"

The Fundamental of Design Philosophy

posted Jul 28, 2022, 6:08 AM by jeffery jim


When talking about design in construction, most engineers only recognize models based on structural analysis. In this case, graduates are usually exposed to deterministic type of design with proper design calculation and all sort of parameters which are proven to be acceptable for cases considered as ultimate limit state (ULS) as well as serviceable limit state (ULS).
2. Nevertheless, what most engineers are not exposed to is the second type of design derivation which is design assisted by test. The former was deterministic and the latter is probabilistic or heuristic by nature as stipulated and acknowledged by the Eurocode in BS EN 1990. In this particular code of practice, there is no definite way to simulate an outcome which can be deemed as structurally sound, safe and economically viable. Hence, it is the task of great engineers to determine it as so.
3. Deterministic approach with all parameters and equations is essentially the day to day basis where engineers confidently produce a design knowingly that all parameters satisfied and complied with high safety factor. It is so robust, all steps in the design is governed by specifications, guidelines, code of practices and other relevant dossiers which are endorsed by institutions locally and globally.
4. Heuristic approach using models involves probabilistic approach(es) with set of criteria of concern. Where will this approach be utilized in construction field? It is vastly used in non-conventional constructions as well as during the maintenance phase of structures and infrastructures. When heuristic approach is in use, it usually renders possibilities of favoring outcome(s). This does not mean deterministic approach or methodologies do not involve statistics. The deterministic method embedded statistics with set criteria which is statistically favoring based on normal distribution.
5. In conventional design method, equations are preset with values which involve with significant values of one-tailed or two-tailed borders. In most cases, it allows for value to cover defects as low as five percent which means the characteristic values for a safe design covered until the ninety-fifth percentile of the distribution. Elaborate coverage of partial factors is another way to waive these preset values through favoring outcome based on design brief, material safety, reliability and other factors. This are involved in value engineering and reinstatement of structures that may lapse its SLS but not ULS.
6. In non-conventional design such as dam design, use of new and unproven materials, and structural strengthening or rehabilitation; heuristic design are assisted by testing, other comprehensive prior studies, and data sets. Scale models are used to derive certain parameters and/or indicative to what finite element simulation will produce. It involves prediction, correlation-regression and correction of information. It has to be conclusive through statistical analysis which sees a limit of favorable outcome(s).
7. Engineers have new horizons to explore when it comes to design and the foundation for academia to find and close gaps through their research. There is no one or single approach that is correct in proving a design is safe, sound and economical.

Schedule Basis Memorandum - Inclusion of Statistics

posted Jul 28, 2022, 6:07 AM by jeffery jim


I am preparing a few abstracts for conventions this year. Among these papers are related to project management apart from engineering and geology. One of the key papers I am going to present would be in regards to risk distribution which was never entailed and annexed previously in preparation of Schedule Basis Memorandum (SBM) as essential submission when deriving a work program for projects by NGCs like PETRONAS. Unlike JKR PWD203 variants contract which require a conventional project contractor to submit a work program in just fourteen days, NGCs or mega projects of national interest require and allow for a longer period of time to prepare a work program. Often, the work program will be scrutinized and SBM is one of the many bases a planner or project control engineer will be based on.
2. For many years, contractor will have to prepare a work program using software like MS Project and Primavera to compute a decent work program which capitalized on Gantt Chart and PERT features which are related to Monte Carlo simulation. Here, the longest route is called critical path and this method is called Critical Path Method (CPM). This path shows the ultimate time required by the project in order to complete based on project brief, contract, cost, time and statutes.
3. Although these software and tools have been dominant in establishing basic requirement to establish a manifested contract where time is always of the essence, it lacks in robustness during the project control phase. Most of the time, the CPM established may not be the crux to delay. The inability to foresee other risks within the network and nexus of a series of works has hindered many stakeholders from tracking delays during the earlier part of project implementation stage. This is also a reason why S-curve for typical projects are always flattened at the 30% of the project duration before start to climb in linear or exponential shape toward the 90% of the total contract time.
4. In order to tackle this problem, many kind of risk analysis tools have been introduced and adopted. It can be Fishbone method, Tripod Beta method and so on; where all are then included into a risk register. The problem with risk register is a statistic subset and known as ordinal data. It is a grouping and then arithmetically summed to have a register with categorization. Less robust risk register only categorize risks as ordinal and nominal dataset. This is how data are segregated and analyzed. It is over simplified and traditional as conventional approach is much easier to understand, control and dictate but these have zero value when it comes to implementation with bigdata.
5. SBM usually incorporate these kind of oversimplified registers which often bring zero value when it comes to forecasting. These kind of registers cannot be use for further statistical analysis when associating a work program with risk assessment tools such as Primavera Risk Analysis or Safran Risk Manager. There is no way for a client to injunct a remedial or recovery plan especially when it comes to micromanagement. A specific approach is required and hence, a statistical approach for analysis is required when it comes to thorough contractual documentation and determination.
7. One of the many features in a risk management software is the allocation of risk and uncertainty distribution. This is essential where the distribution of risks are divided into many types, typically; beta pert, lognormal, triangulation and others. Unlike a typical scheduling software with uniform distribution, the inclusion of these graphs is essential when running Bayesian Belief Network and Monte Carlo simulations up to 1,000 iterations. Nevertheless, the basis to establish each task and its risk distribution should be determined based on past project bigdata. Without a prior and typical population, a posterior cannot be established nor conclusive in depicting or rendering a possibility.
8. For this reason, a call to establish specific type of distribution is indispensable and inevitable. The only variable in this kind of distribution shall be regional or internal issues when it comes to kurtosis of the graph as the eccentricity of the graph is fixed based on bigdata. Hence, this will give project control department more power to interject a possible delay before resorting to mitigation works which is too late and time consuming.
9. Another advantage of statistical and scientific approach would be great for client or top management to establish their project timeline during the initial stage of a project lifecycle as it will provide assurance that the contract brief is realistic and have at least achieved at a range between the seventy-fifth percentile to the eighty-fifth percentile which fits Pareto Rule instead of picking a number from the sky or making references from past projects with different set of risks, quantum and magnitude.

May be an image of text that says "70 60 50 Original completion date 40 risk of 30 Jaqunn 20 10 Frequency of risk encounters during project schedule Beginning contract date 2តល 30 40% 5 260% Percentage of the original project schedule Fig. 1. Distribution of risk encounters"

Particle Size Distribution (PSD) - Understanding and Troubleshooting

posted Jul 28, 2022, 6:06 AM by jeffery jim


Recently, there has been an issue in regards to aggregate size which did not fit into the envelope and failed to comply with the standard specification. The issue have serious implication as it affect the wearing course of the road and this can run as high as tens of million of Ringgit. Non-compliance mean the contractor will have to scrap the existing asphaltic course, delaying their work and borne the additional cost to reconstruct another layer of wearing course in order to complete the work satisfactorily.
2. Here, an engineer have to understand the two elements of supervision, which are; quality control (QC) and quality assurance (QA). QA is the a field of supervision where all issues are thoroughly reviewed to avoid failure or at least reduce the failure frequency to expected minimum. QC on the other hand is a scope of work to check work-in-progress or completed work based on samples in allowed sampling frame. QA will come into the picture once more when QC indicates there are continuous failures which need to be controlled and will cease from reoccur.
Therefore, I was tasked to probe into this issue as the contractor could not trace the crux to this problem. During initial discussion, I specifically reckon that the issue is due to human error that may occur at the laboratory. Their QAQC manager however opined that it was not a big issue due to sampling frame and sample size. A non-compliance is a non-compliance. Open up of works and investigation have to be conducted in order to conclude and resolve the root of cause.
3. Based on limits of allowance for particle size distribution non-compliance is relative low (via IRI test requirement) which is 0.5%, unlike concrete which allows 5% of the population to be defective or remain under the characteristic strength. Here, we have a highly stringent allowance to abide by. The magnitude of this issue is significantly high due to cost or weightage of the project and the high standard requirement(s).
4. After checking the hot bin and the batching processes, I found out that there is no problem with the system as all processes are automated. All systems are good and fully calibrated and no sign of disintegration after putting it to test. All gauges are functional, proper computation and no latency to the system.
Marshall Stability Test indicates acceptable result and complied to the design and trial mix. Therefore, viscosity is not the issue here and such test is redundant and futile. I do not regard the Bitumen Extraction Test to be indicative as hydrocarbon such as asphaltic concrete will lost its bitumen content (due to disintegration) when exposed to heat. It will be relatively lower by percentage when compare to the approved design mix.
5. I have proven that the issue of hot bin and batching to be non-existent. I came back to my initial thought and the only thing that may affect the sampling which is human error which is related to the duty of care and/or degree of care in executing PSD test. Although PSD test is considered as one of the most fundamental tests in geotechnical and road laboratory, there are high chances that sampling and processes may not be as adequately conducted as per BS 1377 Part 1. This means and reflect on the additional processes taken place as impartial and missing on elements which were not specifically mentioned or reflected in the standard specification.
6. Sample of particles was made available and I started to divide samples into two categories. QA sample conducted by the consultant and QC conducted by in-house laboratory with one exception; I will do the quartering instead of others. Samples are prepared into a tray and then poured into Riffle Sample Divider. This acts as a traceable action and as controlled samples versus samples (that were done traditionally by the in-house laboratory). Here, the crux of the issue shall be determined when PSD tests were completed and concluded.
7. After completing sieving for both QA samples, samples remain at the mean of the envelope perfectly which concludes that the sample I have taken randomly and the design mix is acceptable. QC samples complied with the requirement but leaning at the edge of the envelope for coarser grains and then normalized after 5mm aperture sieve.
8. From this particular exercise, the outcome is the exact prediction which I have projected initially before conducting investigation and traceability tests. It is human error and deterministic by nature. The failure is due to the way sample quartering were performed previously. It is not reckless but the lack of attention taken when handling dust or mineral fillers as well as the method of sampling. It took an engineer with statistics knowledge into call out such small predicament in sample handling and to refine the proper method when engaging in normal distribution sampling.
9. This exercise renders the importance of engineer to be very articulate when it comes to QAQC and additional knowledge would substantially help in troubleshooting issues. Lesson learned!

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How to Read British Standards (BS)

posted May 10, 2022, 6:23 PM by jeffery jim   [ updated May 10, 2022, 6:27 PM ]

I spent the whole afternoon drilling my proteges about all parts of BS1377. It is hard to read BS continuously and during my varsity years, I can hardly read more than 2 to 3 pages in one seating. Most of the time, I will doze off and that made it almost impossible to understand things and pass design subjects.

2. The thing about BS is its nature which goes in point format and dull, unlike American codes which usually in paragraphs and narratives for clearer understanding. Eurocodes are much easier to read as they are in paragraphs with better narrative(s). Nevertheless, every engineer needs to understand the fundamental concepts and rely on these in order to perform their duties or to utilize exploits that are available in it.

 3. The right way of understanding the concept in BS or parts of BS is to understand the normative references and assigned parts. Second, read through the table of content and comprehend the coverage of the standard and core concept on each main item.

4. Mind mapping is essential unless you have a good photographic memory that links each part and concept to another. Understand the similarities, alternatives, and differences.

5. Start with a general concept or the primary standard before moving to other normative references. One have to read in the light of another documents in order to render the actual concept and approaches. Without normative references, one can be handicap and have their mind mapping links truncated. This is not a good process when working around BS.

6. Read one main item or one specific proceeding (can be a test or key concept) in each sitting. Do not push yourself to read more than what you can take. It is much easier to understand things within the above-mentioned limit nowadays. Finish each sitting by watching two to three Youtube videos that are related to your reading. This will reinforce the concept with audiovisual aid. At the same time, this will assist you in comprehension if English is not your first language.

7. Revisit your reading in a week or a month's time. Try to read and visualize what is/are mentioned in each passage. Reading buddy would be great where a pair can go for a spar by asking related questions based on videos or relevant BS. Jolt back everything you missed in your mind map(s). Now you have a comprehensive note on the subject(s) that matters.

 I hope you can benefit from this tip when you are trying to learn via BS independently. One day, you could duplicate what I am able to do, which is to make references to standards without stuttering and in a convincing manner

Pile Integrity Test

posted May 8, 2022, 6:07 PM by jeffery jim   [ updated May 8, 2022, 6:08 PM ]

This is a very informative video about Low Strain Impact Integrity Test although there are several (5 types to be exact based on ASTM). Out of these five, most time we will utilize two specific types of test which are High Strain Impact or PDA and Crosshole Sonic Logging. I prefer both of these tests than the rest. The followings are addendum about this video which one can benefit when monitoring bored pile or casted pile at site.

Pile Driving Analyzer (PDA) displays the same wave as per low strain in the graph in order to check pile's integrity and/or impedance. For starters, impedance of a pile can be defined as follows. "Change in impedance is related to change in pile cross-sectional area A, as well as pile material quality. Increase in pile impedance or soil resistance forces results in a decrease in measured pile top velocity. Conversely, decrease in pile impedance, results in increased velocity. By observing changes in impedance, pile quality."

In the same manner, we can check necking or bulging/bulb that may occur during boring and casting thru PDA. It is important to check CAPWAP graphs and not rely heavily on summary of the Integrity Class and Acceptability as well as the CAPWAP capacity which is the estimation for both end bearing and skin friction. Nevertheless, it is usually the case when specialist review the classification based on graphs but with some common knowledge about wave(s) propagation, one can crosscheck the work of the specialist signing off that particular test record. I encountered a few cases where the graph is not satisfactorily conform with high integrity rating which I will not discuss here.

The benefit of using low strain compare to high strain is the accessibility and mobility of conducting test on completed sections. Second, it is the only way to have some initial assessments on the shape without the need of tubular pipes for Sonic Logging Test and when Bi-directional Static Load Test (BDSLT) or Static Load Test (SLT) failed the three criteria or a single criterium for working load settlement, twice working load settlement or residual settlement.

The second test would be Sonic Logging (USPIT). This particular test compliment what was discovered in in PDA test. This test is conducted prior to the execution of PDA test where the shape and integrity of the pile is examined through cross sections. The larger the pile, the more sections are required, similar to low strain PIT using echo and receiver. Based on this waterfall wave and spectrum, one can determine the existence of honeycomb and other irregularities such as necking and bulging of pile.

The importance of the shape not only crucial in ensuring the integrity of pile especially when there are possibility of necking. Bulging or bulb is not really crucial as it increases skin friction and overall pile capacity; however additional load may be substantially dangerous for the total load at the bearing and/or skin friction. Additional load from bulging of the casted pile can be detected when conducting BDSLT and not in Static Load Test. The reading of the top side of the O-cell or jack will indicate that when compared to bottom side of the jack. This is one of many ways to vindicate or justify when BDSLT reading may deviate aside from soil strata/stratum change(s). This serves as complimentary observation(s) when checking/diagnosing pile or piles' performance holistically.

There are so many variables when estimating pile's capacity and performance. I reckon that sound regional or local geological understanding plays a very high significance for a site engineer or resident engineer to plan for total depth and the inclusion of proper socketing length. In most cases, I rarely follow recommendations made in the drawing if the soil at the boring point have low performance despite the depth set by the designer. With sound and clear estimation, we rarely find issues with working load settlement and residual settlement. In most cases, the issue will only occur with twice working load. Why? The base of the bored pile was not cleaned totally, hence it requires certain degree of depth to mobilize the end bearing.



Low Strain Pile Integrity Test


What triggered such cracks?

posted May 8, 2022, 6:05 PM by jeffery jim


I saw this article and it is quite intriguing where some comments which were made by readers are controversial. Whose fault is it when there are such cracks grazing around the end of the beam? Is it the contractor, consultant or client?

2. Most of the comment made directed such structural failure to consultant. It is definitely convenient as it renders a perspective where cracks triggered when there is lack of reinforcement bar (stirrup or nominal links) at the said area. This led to the reaction of beam(s) under duress and sheared under loads (sic). This is most probable scenario for most structural engineers when they look at this particular photo in the first place. Is it really the case?

3. Typically, such crack patterns are related to shearing but it is hard to establish it is the outcome solely due to the reinforcement issue. There are other issues that one must consider before ultimately putting such failure as design failure.

4. Causal and outcome should be listed as possible mechanisms which trigger such crack. In this case there are several.

4A. Post Tensioning. The construction of such bridge utilizes a lot construction methodologies in post tensioning fabrication in comparison to typical in-situ short span bridge. In this case, usually tendons take precedence when talking about beam performance before the reinforcements. In this type of construction, tendon profile is essential and depends on the end of both tendons. If both ends are live end, then that is not an issue. Nevertheless, if one dead end, this should be visible when stressing is conducted. Failure during stressing where displacement exceed 6% should indicate the failure of tendon or the anchorage bulb (spiral).

4B. Another factor one should consider is the concrete characteristic strength and reaction during the curing period. Low concrete strength will have very low performance for most engineering properties. Second, the hydration and formation of ettringite which may trigger cracking when Delayed Ettringite Formation (DEF) occurs due to exposure of concrete under high heat and inappropriate curing procedure.

4C. The third possibility is the formation of alkali-silica reaction (ASR) or alkali-carbonate reaction (ACR). The low maturity aggregates maybe susceptible to chemical reaction and lead to crack formation. This incident is the initial mechanism which leads to cracks propagation and not the main reason for such failure to occur.

5. There are several other reasons which may propagate or trigger such crack but degradation in the long run. If we put all of these into a desktop study, it pointed all three parties; consultant, contractor and client as defaulting parties. Contractor might have failed to diligently check their work before commencing to another stage. The consultant have failed to supervised the job with low workmanship or failed to interpret test records and reports. Client? Yes. In this case, the client can be blamed if they failed to stipulate or mentioned about the suitability of materials in their specification and allows recommended material (in this case, aggregate) which is highly reactive to be used as construction material.


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