BY: SAMUEL NJAGI CHARAGU, HSC, P.E .FIEK

 

The 20th Engineers International conference at Tom Mboya labour college, Kisumu

  The collapse of buildings under construction has

exposed the ills that bedevil the building sector. The frequent collapse of structures in Kenya

leading to injuries and deaths in the past is a matter of great concern.

These construction site accidents which are avoidable have claimed lives of innocent Kenyans robbing families of their breadwinners and loved ones; causing irreparable damage to the injured workers and people who eke out a living trading around the construction site.

Kenya has experienced frequent collapse of buildings. The most vivid are the collapse of a building in Nairobi Ronald Ngala in 2006, collapse of a building in Kiambu town in 2009, another building in Kiambu in 2010 and at pipeline, Embakasi in June 2011.

Over the last six years, a number of buildings some under construction and others completed have collapsed in Nairobi and other major towns in Kenya as indicated by table below.

Description Date Casualties Reported causes of failure

Ronald Ngala Junction bldg

23/9/2006 14 deadSeveral injured

Causes of failure were poor design and supervision, poor materials and workmanship.

Kisii Collapsed Building at Kisii district

6/06/09 1 dead11 hospitalized

Concrete not meeting minimum strength for structural elements (Core strength= 14.7N/mm2<25N/mm2)Construction exceeded by 3 floors shows lack of proper monitoring and supervision.

Description Date Casualties Reported causes of failure

Comcraft House in Nairobi City

16/09/2008 None Corroded supporting RHS which lowered its strength. Major cause-Lack of regular maintenance.

Kiambu Town Buildings

19/10/09 Dead – 16Survived with injuries – 16

-Strength concrete ( 7.3N/mm2 -7.7 N/mm2

<25 N/mm2 Design strength)-Design issues-No records of approval of works at every stage of construction

Building in Pipeline Estate, Embakasi

14/06/11 4– dead14-Unaccounted Many injured & hospitalized

-Strength concrete ( 7.7N/mm2 -9.4 N/mm2

<25 N/mm2 Design strength)-Poor workmanship-Inadequate designs

An article by Eng. Mambo mentioned ten reasons which can lead to collapse of structures. These include; inadequate geotechnical and materials investigations, use of inappropriate specifications and manuals, incompetent design, poor workmanship, lack of ethics, poor supervision, close relationship between parties to the contract, use of inappropriate materials, weak laws and corruption.(April 2010 IEK Journal Vol.31)

Analyzing reports from Ministry of public works on collapsed structures, the Structural Engineers’ concluded that most buildings failed due to lack of proper supervision and poor construction procedures. In this case the blame can be apportioned to the designers or contractors’ supervisory staff as well as the council’s inspection staff. Actually all stakeholders can be blamed (MOPW Report 2006).

To identify the challenges facing the Kenyan construction industry in respect to collapsing structures, a study to determine the major cause of collapse of buildings in Kenya and to establish the major challenges to quality control in building projects was carried out by Eng. S.N. Charagu when under taking a MSc course at Jomo Kenyatta University of Agriculture and Technology.

The research was carried out through Surveys, Questionnaires, analysis of data from Ministry of public works, analysis of experimental data obtained from non destructive and material tests for ongoing works.

Questions were formulated and given to different stake holders involved in construction works. Observations were conducted from randomly chosen construction sites and supervising team. This helped to supplement the questionnaires. Care was taken to avoid suspicion and the research was conducted in a way that prevented errors from false information.

The results showed that lack of quality control on construction materials and workmanship contributed to the collapse of building structures.

Execution of work without approval, unskilled workers, batching methods, lack of supervision and deficient designs were among the factors leading to collapse of building structures. It was also found that the designers do not follow their designs leading to poor construction.

Reasons for increase in collapsing buildings %Increase in number of constructions works

45.0

Too many unqualified contractors30.0

Various upcoming projects with no professional engagement 25.0

Total 100.0

Tools %Frequent material testing 36.0The integrity of both the engineer on site, contractor and client 14.0Regular testing of work at every stage 16.0Ensure that all concrete works are tested before undertaken 4.0Approval of materials before use. 7.0Impromptu site visits 6.0Competent contractors 4.0The contract conditions 2.0Encouragement of staff 2.0Regular reports 2.0Advising through client 2.0Templates 2.0Cube strength tests 3.0Total 100.0

Suggestions for improving quality %More quality control information from consultants 21.0Engagement of competent and experienced persons with integrity

22.0

More supervision of the works by the Supervising Engineer

18.0

More cooperation from Employer, Engineers, and Contractor

8.0

Materials are tested for compliance with specifications 15.0Assigning more time for training on importance of Quality

9.0

More cooperation from the government supervisors 2.0Transparency in tendering 5.0Total 100.0

It was also noted that some foremen do not follow the specifications and are not keen on procedures in construction.

During construction, a drawing is issued to the foremen who are required to study and ensure the drawing conforms to the building dimensions. But most of the sites use unskilled labour who are unable to read the drawings and it was noted that the Engineers are unavailable to intepret and check the works.

Confirmation that the designs and drawings dimensions conform to the proposed structure.

Testing of the materials to conform to specifications in designs. This includes carrying out a mix design for the concrete works.

Engagement of a qualified person for daily supervision of the works. He should ensure approval of works at various stages of construction.

Proper construction equipment which are well maintained by the contractor are on site.

The causes of collapse of buildings structures can be concluded as follows:Most Engineers did not carry out the designs by

themselves. Some structures collapsed because of deficiency of the designs.

Site agents and foremen are not keen on quality control on construction materials and construction processes leading to poor workmanship.

Some contractors execute work with sub standard materials. Data collected established the problem of lack of tested materials.

Problems with execution of work by contractor without approval. This was also due to lack of supervision by designers who are not available to give advise to the contractor.

Unskilled workers, who assume they know, prepared concrete mix leading to low concrete strength which led to collapse of structures.

The Engineers and site agents are not keen on batching methods, lack of proper equipment and tools was an hindrance to proper concrete mix.

Experiments established that poor concrete grade was used for reinforced concrete structure which could not carry the intended loading leading to collapse of structure.

The study also concluded that cases of poor designs and poor workmanship had not decreased even after hearing and seeing the collapse of buildings in Kenya; the cases being reported were higher than previous ones.

There is need for Engineers to be keen on their designs and check the drawings. This will eliminate deficiency in designs.

There should be more supervision of the works by the Supervising Engineer, making sure that materials are tested for compliance with specifications and assigning more time for training on importance of quality.

Since the major cause of collapse of buildings is concrete works, mix designs be done before any concrete works are carried out and the supervising Engineer to ensure that adopted mix design are followed during construction.

The need for government supervisors (Local authorities) to ensure by-laws are followed and making sure that there is an efficient system of reporting poor work.

The Government has enacted two laws, The Engineers Act, 2011, No.43 giving mandate to Engineers Board of Kenya to enter site and check what the professionals have designed (section 7(1) (g). The EBK to take their position.

The National Construction Authority Act, 2011 established the National Construction Authority, with the mandate to register and regulate all contractors in the country. The MOPW under whose docket this authority falls should exercise their mandate.

Eng. Sam Mambo. (2010). Why Engineering Structures Fail. Journal of the institution of Engineers of Kenya, Vol. 31, Issue 2 , pg 28-29.

Kenya Standard KS 2183:2009 (KEBS 2009): General Concrete works – Code of practice

Eng. Charagu S.N. (2013) MSc Thesis on Collapsing building structures in Kenya, JKUAT.

Ministry of Public Works MOPW 1976, General Specifications for Building Works.

Ministry of Public works (MOPW) http://www.publicworks.go.ke. Engineers Reports on projects.

THANK YOU