Nonconventional and Vernacular Construction Materials

Characterisation, Properties and Applications

Kent A. Harries, Bhavna Sharma

• Publisher: Woodhead Publishing
• Year: 2016
• ISBN:
  9780081000557
• Topic: Tecnologia e ingegneria
• Subtopic: Ingegneria civile

Nonconventional and Vernacular Construction Materials: Characterisation, Properties and Applications provides a comprehensive repository of information on materials science and the modern structural engineering application of ancient, vernacular, and nonconventional building materials, with leading experts contributing chapters that focus on current applications and the engineering of these construction materials.

Opening with a historic retrospective of nonconventional materials, Part One includes a review of vernacular construction and a discussion of the future directions for nonconventional and vernacular materials research and applications. Chapters in Part Two focus on natural fibers, including their application in cementitious composites, non-cementitious composites, and strawbale construction. In Part Three, chapters cover the use of industrial by-products and natural ashes in cement mortar and concrete, and construction using soil-cement blocks, clay-based materials, adobe and earthen materials, and ancient stone masonry. Timber, bamboo, and paper construction materials are investigated in the final section of the book.

• Provides a state-of-the-art review of the modern use and engineering of nonconventional building materials
• Contains chapters that focus on individual construction materials and address both material characterization and structural applications
• Covers sustainable engineering and the trend towards engineering for humanity

Part One

Nonconventional materials and vernacularconstruction

Outline

1. What we learn from vernacular construction

2. Introduction to nonconventional materials and an historic retrospective of the field

3. Future directions for nonconventional and vernacular material research and applications

1

What we learn from vernacular construction

Randolph Langenbach Conservationtech Consulting Oakland, California, United States

Photographs by © Randolph Langenbach, except as marked.

Abstract

A variety of examples of vernacular architecture are used to illustrate the shift from an empirically based traditional knowledge handed down over centuries, to our own era in which that knowledge has been lost. The loss is due to the introduction of new materials and construction systems, changes in education, and increasingly disused construction systems and technologies forgotten through neglect. This time-honored empirically based knowledge has been replaced by some very sophisticated scientific research in the fields of materials science and structural engineering, but this is not often communicated or accessible to those who need it most: those on the construction site. While modern science has often confirmed the time-honored empirical knowledge, it has not and cannot entirely replace the kind of knowledge passed from generation to generation based on trial and error experiences over centuries and even millennia. This chapter investigates this shift from, and return to, the vernacular through a range of examples from Arg-e-Bam in Iran and Srinagar in Kashmir, India, to 19th-century industrial works and the impacts of the 1906 San Francisco earthquake.

Keywords

Afghanistan; Bhatar; Bhutan; Chicago; Dhajji dewari; Earthquake; Hımıs; India; Iran; Kashmir; Masonry; Mud construction; Pakistan; Rubble stone; San Francisco; Skeleton frame; Skyscraper; Taq; Timber construction; Turkey; Vernacular construction

1.1. Bam

On December 26, 2003, while people were still sleeping, an earthquake with a magnitude of 6.6 (USGS 2004) struck the ancient city of Bam in Iran. Despite the relatively modest magnitude, the surface shaking was intense enough to devastate the city, killing approximately 30,000 people, one-third of the population. Many of the news photographs that circled the globe were of the devastated ruins of the city’s most iconic heritage site, the ancient citadel recognized as the largest earthen structure in the world, the “Arg-e-Bam” (Fig. 1.1). Because of these dramatic views of the pulverized parts of the Arg in the news, many people assumed that most of the 30,000 people who were killed died in the ancient earthen buildings of the Arg. In fact, they did not. The death toll was almost exclusively caused by the collapse of buildings in the modern city, almost all of which had been constructed during the past 30 years.

The “Arg” was an ancient walled city that became an archeological site and museum of the history of the city. After being continuously occupied from as early as the 6th century BCE, it had fallen into disuse in the early 19th century, when people felt safe enough to abandon their houses the walls and move into their date palm orchards that were planted around the Arg. By the middle of the 20th century, well after the Arg buildings had fallen into roofless ruins, a major restoration project was begun to turn the Arg into a tourist attraction. Over the course of the half-century preceding the 2003 earthquake, a wide swath of buildings from the main gate to the Governor’s House on the hill were restored (Figs. 1.2 and 1.3). These included the main market street, two caravanserais, the main mosque, the Governor’s House, and a large part of the fortifications. By the time of the earthquake the restored site, with its undulating earthen walls, had successfully become a world-famous attraction.

Figure 1.1 The Arg-e-Bam archeological site in Bam, Iran, before and after the 2003 Bam earthquake.

Figure 1.2 Earthquake destruction of the restored parts of the Arg-e-Bam photographed four months after the earthquake.

The 2003 earthquake rendered the Arg almost unrecognizable. Many of the formless rubble piles actually stood higher than the walls that were left still standing. The site quickly became a symbol for the earthquake in the same way as did the National Palace in Port-au-Prince, following the 2010 Haiti Earthquake. When I arrived to inspect the site as a delegate in a UNESCO-organized international reconnaissance and conference held four months after the earthquake, the conventional wisdom was that the damage could be explained by the simple fact that the Arg was constructed of unfired clay.

Figure 1.3 View of an archeological site in Bam with high walls that came through the 2003 earthquake with very little damage.

For those of us who arrived in Bam shortly after the earthquake, the argument that the Arg collapsed simply because it was unfired clay did not immediately seem to be unreasonable. This impression was reinforced by what could be witnessed in the surrounding settlement, where many modern steel-frame buildings had also collapsed. In fact, prior to my arrival in Bam I had been told by a seismic engineer in Tehran that earthen construction should be banned, despite its continued use and practicality in the desert climate and a shortage of timber in Iran and the rest of the Middle East.

At first glance, after entering the Arg-e-Bam there was little to be seen to disabuse one of such an opinion. The devastation was vast. However, on traversing the site more than one time, there were increasing visual signals that being made of unfired clay could not alone explain the nature and extent of the damage. First, there was almost no evidence of diagonal tension cracks in the collapsed or still-standing walls. Instead, almost everywhere the walls looked as if they collapsed vertically – like a slump test with too much water in a concrete mix [1].

Looking further, it became evident that some walls and structures had appeared to survive almost entirely intact, while others were only a pile of rubble. As I continued to look a pattern began to emerge. This was particularly evident when I came upon an area that had not been restored. The standing walls of unrestored structures, abandoned for more than a century and a half, had survived with little damage, while those that collapsed were almost always the ones that had been restored in recent decades. In addition, when examining the military fortifications, counterintuitively, the thicker the wall the more likely it was to have been collapsed by the earthquake.

As I continued to look, I also discovered that in a random sampling of the cracked open sections of the collapsed or broken walls, there was frass (insect excrement) in practically every single one. The Iranian archeologists told me this was from a local species of termites. Termites? In an archeological site with walls dating back 2000 to 8000 years? This comment launched me on a study that in the end had more to do with materials science than with structural engineering (Fig. 1.4).

The first question was: Why did the unrestored roofless buildings survive the earthquake better than the restored structures? And did the termites have somethin...

Table of contents

• Cover image
• Title page
• Table of Contents
• Related titles
• Copyright
• List of contributors
• Woodhead Publishing Series in Civil and Structural Engineering
• Preface
• Part One. Nonconventional materials and vernacularconstruction
• Part Two. Natural fibres
• Part Three. Concrete and masonry
• Part Four. Timber, bamboo and paper
• Index