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KARACHI:
The intense El Centro earthquake that shook the Imperial Valley in Southern California on May 18, 1940, was recreated at the NED University of Engineering and Technology on Friday.
All eyes, as well as cellphone cameras, were fixated at a structure similar to stone masonry buildings that exist in large numbers in the Northern Areas of Pakistan. The structure was placed at the Shake Table testing facility available at the universitys civil engineering department to check the stability of buildings in this part of the world.
The facility is used to simulate real-time earthquake ground motion to record the dynamic response of a given structure placed on the table, explained Dr Sarosh Hashmat Lodhi, the universitys civil engineering dean. With his safety helmet firmly in place, Dr Lodhi became busy again as he issued instructions on a walkie-talkie to his team that was present in the control room. They were about to recreate similar ground motions as the earthquake in California.
The El Centro was a typical moderate-sized destructive event and its ground acceleration record is available to be replicated through the control software at a computer system, he told The Express Tribune, adding that the records are connected to the Shake Table.
The test project, which is being carried out in collaboration with Aga Khan Development Network, will help experts gain a better understanding of earthquake resistance and collapse mechanisms of a large number of similar buildings that exist in the Gilgit-Baltistan province, which is located on a highly seismic belt. We will be able to spot the weaknesses in traditional construction methods and suggest low-cost improvements for a majority of underprivileged residents to strengthen these buildings against future earthquakes said Dr Lodhi.
Given the abundant availability of stones and the low construction cost, most residents use stone masonry in cement or mud mortar with earthen flooring to build single and double-storey residential buildings, he pointed out. While the region is seismically very active due to its position near the Indian and Asiatic tectonic plates, the uniqueness of this type of construction brings more challenges in the prediction and understanding of its seismic behaviour.
The organiser transported craftsmen from Hunza Valley along with all the material to make sure the model-structure is as similar as possible to the actual buildings in Hunza. The model was designed to be one-third the scale of the actual stone-masonry houses.
The experiment
The model structure placed on the Shake Table sustained the peak ground acceleration of the El Centro earthquake when the experiment began. It was not until the acceleration was raised to around 150 per cent of the recorded data that the entire structure collapsed.
The structures rear part, which is colloquially referred to as chikish and designated to store the edibles, took the major impact and turned into debris. While the internal configuration of columns in the traditional construction method helped survive the front part of the building from collapsing completely.
We will undertake another experiment in the next two months after carrying out strengthening measures in the structure, based on this experiment, said Dr Lodhi. Subsequently, the AKDN will be able to implement the findings of these experiments in the region.
Opportunity of a lifetime
An NED engineering student, who witnessed the collapse, was in awe. This is an opportunity of a lifetime to witness such an experiment, he said. For now, the experiment and its findings have been restricted to the Gilgit-Baltistan region but Dr Lodhi hoped to carry on the success of this experiment across the nation in the future.
We hope to establish a technology transfer mechanism to bridge the gap between research and development to improve predominant traditional habitats, said Prof. Muhammad Masood Rafi, a co-investigator on the project with Dr Lodhi.
