P R O B A B I L I S T I C FA I L U R E

A S S E S S M E N T O F A S E M I -D E T A C H E D R E I N F O R C E D

B U I L D I N G U N D E R G R O S S - E R R O R

OKOLI OBINNA CHARLES CVE/06/7973

SUPERVISOR- PROF. J. O. AFOLAYAN DATE-

NOVEMBER 2014

INTRODUCTION• STRUCTURAL DESIGN INVOLVES PROVIDING RESISTANCE AGAINST

MOMENTS, FORCES AND OTHER EFFECTS ON THE MEMBERS. • IN THE INDUSTRY, A STRUCTURAL ENGINEER CAN BE ASKED TO VET A

DESIGN DONE BY ANOTHER DESIGN ENGINEER JUST AS A FORM OF GOOD PRACTISE, BUT MOST OFTEN WHEN THIS IS DONE TRUE FACTS ARE NOT GIVEN BECAUSE NO TWO DESIGNS WOULD EVER BE THE SAME.• IT IS IN THIS REGARD THAT RESEARCHERS IN STRUCTURAL ENGINEERING

DECIDED TO THINK TOWARDS PROBABILISTIC ASSESSMENT TO SHOW HOW RELIABLE A STRUCTURE IS USING PROBABILITY AS A TOOL.

AIM • The Aim of this research is to determine the level of risk associated with a

reinforced concrete building under gross error.

OBJECTIVE• ANALYSE THE REINFORCED CONCRETE BUILDING AS BUILT• ESTIMATE THE LEVEL OF PROBABILITY OF FAILURE OF ALL STRUCTURAL

ELEMENTS IN THE BUILDING• PERFORM A REDESIGN OF THE BUILDING USING A FINITE ELEMENT

TECHNIQUE.• COMPARE THE IMPLIED RISKS FOR THE AS BUILT AND THE PROPOSED DESIGN• MAKE RECOMMENDATIONS AS APPROPRIATE

JUSTIFICATIONGROSS ERRORS IN CONCEPT, PLANNING, DESIGN AND DETAILING OF STRUCTURES UNDOUBTEDLY ACCOUNT FOR SOME CALAMITIES, BUT BY FAR, THE GREATER NUMBER OF COLLAPSES OF CAST-IN-PLACE CONCRETE STRUCTURES ARE DUE TO CONSTRUCTION ERRORS IN THE FIELD. GROSS ERRORS MUST BE ADDED DEFICIENCIES IN EXECUTION OF CONSTRUCTION TECHNIQUES AND THE PRECAUTIONS TO BE TAKEN TO AVOID, REDUCE, OR AT LEAST RECOGNISE THE FACTORS THAT COULD AND DO CAUSE CONSTRUCTION FAILURES IN THE FIELD OF CAST-IN PLACE CONCRETE.

THE COLLAPSE OF A STRUCTURE IS ALWAYS A TRAGEDY, ALL THE MORE SO WHEN WE LOOK BACK AND REALISE IT WAS PREVENTABLE. GROSS ERRORS IN CONCEPT, PLANNING, DESIGN AND DETAILING OF STRUCTURES UNDOUBTEDLY ACCOUNT FOR SOME CALAMITIES, BUT BY FAR, THE GREATER NUMBER OF COLLAPSE OF CAST- IN PLACE CONCRETE STRUCTURES ARE DUE TO CONSTRUCTION DEFICIENCIES IN THE FIELD. PLANS AND SPECIFICATIONS ARE ONLY THE INITIAL STAGES IN THE CONSTRUCTION OF A PROJECT. THE IMPLEMENTATION OF THESE PLANS WHEN CARRIED OUT IN FULL ACCORD WITH THE SPECIFICATIONS CAN BE EXPECTED TO DECREASE THE DANGER OF A FAILURE. (CLIFFORD ET AL, 1975)

SURVEYS HAVE INDICATED THAT HUMAN ERROR IS CONSIDERED AS THE MAJOR CAUSE OF STRUCTURAL FAILURES. ERROR IS DEFINED AS A DEPARTURE FROM ACCEPTABLE PRACTISE SUCH AS NUMERICAL ERRORS, OMISSION OF SOME LOAD COMPONENTS AND OF LIMIT STATE, LEAVING IMPORTANT DETAILS TO UNQUALIFIED PERSONS, INSUFFICIENT CHECKING AND INSPECTION UNDER TIME PRESSURE (NOWAK ET AL, 1986).LOTS OF BUILDINGS COLLAPSE ON A DAILY BASIS IN OUR COUNTRY DUE TO GROSS ERROR AND LITTLE OR NO EFFORT IS DONE TO PREVENT THIS MENACE. AS RESEARCHERS, THERE IS THEREFORE AN URGENT NEED TO SEE HOW WE CAN CURB THIS MENACE IN OUR SOCIETY.

SCOPE OF STUDY

• THIS STUDY INTENDS TO CARRY OUT THE FAILURE ASSESSMENT OF A DISTRESSED SEMI-DETACHED REINFORCED CONCRETE BUILDING UNDER GROSS ERROR.

EXPECTED CONTRIBUTION TO KNOWLEDGE• THIS RESEARCH IS EXPECTED TO INCREASE KNOWLEDGE IN THE AREA OF

FAILURE ASSESSMENT OF REINFORCED BUILDING CONCRETE UNDER GROSS ERROR. KNOWLEDGE IN THE AREA OF THIS RESEARCH WOULD NOT STOP AT TELLING US IF CONCRETE OR STEEL IS SAFE FOR USE, IT WOULD FURTHER GIVE MATHEMATICAL FIGURES STATING THE PROBABILITY THAT A BUILDING WILL FAIL OR SURVIVE. THIS CAN FURTHER HELP ENGINEERS TO PREDICT THE LIFE SPAN STRUCTURES.

MATERIALS• CONCRETE

• CUBE COMPRESSIVE STRENGTH, FCU 20N/MM2

• COVER (COLUMN) 50MM• COVER (SLAB) 25MM• COVER (BEAM) 25MM• REINFORCEMENT

• TENSILE STRENGTH, HIGH YIELD, FY 460 N/MM2

METHODOLOGY• THIS RESEARCH WORK WILL BE CARRIED OUT BY MODELLING THE

STRUCTURE AS BUILT USING A SOFTWARE CALLED ORION FOR REINFORCED CONCRETE BUILDING ANALYSIS AND DESIGN.• COMPONENTS OF THE BUILDINGS SUCH AS BEAMS, COLUMNS AND SLABS

WOULD BE ANALYSED AND THE REASONS OF FAILURE WOULD BE DETERMINED.• THE DESIGN EQUATIONS BASED ON BS8110 (1997) WILL BE TRANSFERRED

TO THE CALREL (CALCULATIONS OF RELIABILITY) PLATFORM, A CODED ALGORITHM FOR THE COMPUTATION OF RELIABILITY.