STRUCTURAL FAILURES - CASE STUDIES

Through Forensic Civil Engineering Investigations

Dr. R. Jagadish

Abstract

To satisfy the requirements in modern fast track construction, several noticeable mistakes are committed by planners, designers, executing agencies and supervision consultants and these are overlooked until and unless these deficiencies are converted into the sign of distress in structural members. This involves additional resources, time and money. In this context, out of many structural failures investigated and rehabilitated, only three case studies are presented in this paper.

Introduction

In most of the modern constructions of high rise buildings, bridges, flyovers, etc., fast track construction methodology is followed. The basic requirement of fast track construction is time, cost and quality.  The construction management team has to adhere to the given time for completion of construction and see that the overall cost of construction does not exceed the estimated value. At the same time, it has to follow all quality assurance and quality system as per requirement in the specification. If these targets are not reached, heavy penalty will be levied on the concerned parties. Hence, all efforts will be made to see that the project is completed on time, minimize the excess cost and satisfy QA/QC systems to the best possible extent.

In the race to satisfy all the above requirements in fast track construction many mistakes / errors / blunders will be committed by all the parties knowingly or unknowingly, which will be overlooked until the deficiencies are expressed by the structural members of the building in one way or the other.  To make up these identified deficiencies considerable amount of time will be elapsed and money will be spent, which will definitely overshoot the estimated cost, time and quality.

In the present paper three such example are presented. The first is a large multistoried building which was under construction, following fast track construction methodologies that had to be investigated after some deficiencies were observed and later on rectified, thus, overshooting the target time and money.

The second is the investigation of the failure of a cast-in-situ post tensioned prestressed concrete bridge girder of a bridge under construction on a National Highway in North Karnataka. During post tensioning the HT cables, the girder hogged considerably and collapsed. An enquiry was conducted; detailed investigation was done to assess the reasons for the failure. 

The third case study is the total failure of a new simple L-type cantilever retaining wall. On a rainy day it collapsed totally. An investigation was conducted to assess the possible reasons for failure. Finally, it was strengthened and restored.