THE SECULAR HOUSE a Manual for Preserv a Tion and Seismic Impro V Ement of V Ernacular Stone Dw Ellings in Bhutan
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THE SECULAR HOUSE A manual for preservation and seismic improvement of vernacular stone dwellings in Bhutan POLITECNICO DI TORINO Corso di Laurea Magistrale in ARCHITETTURA PER IL PROGETTO SOSTENIBILE A.A. 2019-2020 Tesi di Laurea Magistrale THE SECULAR HOUSE A manual for preservation and seismic improvement of vernacular stone dwellings in Bhutan Manuela Reitsma RELATORI Francesca De Filippi Roberto Pennacchio Takayoshi Aoki Settembre 2020 Abstract 6 Introduction 8 Glossary 10 Bhutan through the eyes of a bhutanese person 12 1 | BHUTAN 15 1.1 THE LAND OF THE THUNDER DRAGON 17 1.2 THE BUTHANESE POPULATION 19 1.3 THE MODERNIZATION PROCESS 21 2 | RISK 25 2.1 A FRAGILE LAND 27 2.2 WHAT IS AN EARTHQUAKE? 33 2.3 WHAT IS THE RISK? 36 3 | ARCHITECTURE 41 3.1 A SECULAR TREASURE 43 3.2 TRADITIONAL HOUSES 46 3.3 STRENGTH AND VULNERABILITY 56 4 | MATERIALS 59 4.1 AVAILABILITY 61 4.2 MINES AND QUARRIES 62 4.3 FOREST PRODUCTS 66 4.4 CONCLUSIONS 74 5 | PLAN OF ACTION 77 5.1 DAMAGE PATTERNS 79 5.2 COMMON SEISMIC PRACTICES 93 5.3 SELECTION OF SEISMIC PRACTICES 108 6 | MANUAL 113 6.1 PRIOR KNOWLEDGE 115 6.2 ACTIONS 120 Conclusion 155 Bibliography 156 Abstract ITA Abstract ENG La tesi mira alla ricerca di soluzioni tecnologiche volte al recu- The thesis aims to find technological solutions for the recovery pero di case rurali in pietra in Bhutan, con l’obiettivo di garantire of rural stone houses in Bhutan, with the purpose of ensuring sicurezza ai loro abitanti contro i terremoti che scuotono l’intera the safety of their inhabitants against earthquakes, that shake regione. the entire region. Il Bhutan è un piccolo paese, situato nella catena himalayana, Bhutan is a small country, located in the Himalayas, advancing che avanza in un mondo ormai globalizzato, in bilico tra la spinta in a globalized world, poised between the push of moderniza- modernizzatrice che ha invaso il territorio e l’anima tradizionali- tion that has invaded the territory and the traditionalist soul that sta che tiene a galla l’unicità di questa cultura. La grande sfida keeps the uniqueness of this culture afloat. The great challenge di questa ricerca, quindi, sta nel trovare soluzioni tecnologiche of this research, therefore, lies in finding innovative technolog- innovative, rispettando allo stesso tempo la cultura vernacolare ical solutions, while respecting the architectural and social ver- architettonica e sociale del contesto rurale bhutanese, così ca- nacular culture of the Bhutanese rural context, so characteristic ratteristico da connotare un panorama unico a scala mondiale. to connote a unique landscape on a global scale. La tesi si svolge nell’ambito un progetto di ricerca internaziona- The thesis is part of an international research project SATREPS le SATREPS “for Evaluation and Mitigation of Seismic Risk for “for Evaluation and Mitigation of Seismic Risk for Composite Ma- Composite Masonry Buildings in Bhutan”. Questo studio si rivol- sonry Buildings in Bhutan”. This study is aimed, therefore, to all ge, quindi, a tutti coloro che si troveranno ad affrontare queste those who will face these issues, but above all it is addressed to tematiche, ma soprattutto si rivolge ai tecnici e agli artigiani lo- local technicians and craftsmen, that are often called to intervene cali, ovvero coloro che sono spesso chiamati ad intervenire sul on the recovery and maintenance of the housing heritage. The recupero e manutenzione del patrimonio abitativo. Il linguaggio graphic language chosen must be understandable even to those grafico scelto deve essere comprensibile anche a chi non ha par- who have no particular technical knowledge, involving every sin- ticolari conoscenze tecniche, coinvolgendo nella causa ogni sin- gle inhabitant of the country. The work is developed through the golo abitante del paese. Il lavoro si sviluppa attraverso l’analisi analysis of the seismic risk that threatens the territory and then del rischio sismico che minaccia il territorio e successivamente through the study of the characteristic features of traditional attraverso lo studio dei tratti caratteristici dell’architettura, delle architecture, construction technologies and traditional building tecnologie costruttive e dei materiali da costruzione tradiziona- materials available locally. After the study and re-elaboration of li disponibili localmente. In seguito allo studio e alla rielabora- common techniques and the hypothesis of new approaches, we zione di tecniche di intervento consolidate e all’ipotesi di nuovi finally reach the realization of a manual of intervention, that help approcci, si giunge infine alla realizzazione di un manuale di in- in achieving the safety of Bhutanese rural houses. tervento che possa essere d’aiuto nella messa in sicurezza delle case rurali bhutanesi. 6 7 Introduction The thesis is part of a collaboration between the CRD-PVS Re- exposure represents the value of human lives, goods and herit- search Centre and an international research project SATREPS age. Vulnerability concerns the strength of the building. Hazard “for Evaluation and Mitigation of Seismic Risk for Composite Ma- and exposure are represented with the help of maps, leading sonry Buildings in Bhutan”, involving the Bhutanese government, to the risky zonation of Bhutan. The vulnerability is the factor a group of Japanese research institutes (Nagoya City University, which can be prevented by the retrofitting manual application, National Research Institute for Earth Science and Disaster Resil- so it is better analysed in the following chapter. The THIRD part ience (NIED), Kyoto University, Kagawa University, Tohoku Uni- is about traditional architecture. Advantages and weaknesses of versity, Nihon University) and the Department of Architecture typical Bhutanese architecture are bought out in order to define and Design of the Politecnico di Torino. the vulnerability. Firstly, the chapter starts with the design de- scription that brings out historical, religious and social issues, as Bhutan is a small country in the Himalayan mountains. The in- well as constructive ones. The richness and uniqueness of the credible biodiversity and the rugged morphology have made traditional buildings are pointed out. The use of local materials, the country inaccessible: Bhutan was hidden to the world for in particular, represents both a vernacular value and a weakness centuries and the isolation has made the region a unique place. during the earthquakes. So, the issue is better developed in the The traditional architecture was preserved for a long time and fourth chapter. The FOURTH part is about construction materi- nowadays is threatened by the modernization process, which is als. Traditional and modern materials are analysed, pointing out spreading in the country since the opening to the modern world the local availability and the environmental and social impact, in in the ‘50s. Moreover, the region is subjected to strong earth- order to find a compromise between vernacular materials and quakes and rural vernacular architecture is even more vulnerable useful available materials which can be used for the develop- due to the impoverishment of the constructive knowhow. This ment of the retrofitting actions. After the analysis of the seismic thesis aims to develop a retrofitting manual for enhancing stone risk of Bhutan, with a specific focus on vulnerability, the thesis rural houses’ seismic behaviour. Three steps have brought me to moves on drafting the common practices in seismic retrofit. It is the aim: the personal discovery of Bhutan, through readings and the FIFTH part. This chapter is divided into three subchapters: conversations with a bhutanese girl, the study of the seismic risk the damages analysis, the common practices list and the selec- of the country, with reference to architecture, and the research tion of these practices, according to the issues developed in the of retrofitting practices. Each step has allowed me to learn more previous chapters (the modernization incursion, the architectur- and more about this complex country and about the seismic al heritage, the seismic risk, the available materials). The SIXTH retrofit issue: the drafting of the manual reflects the several chal- part is the manual, which is divided in several procedure cards: lenges. To simplify the reading, the tesis is divided intro six parts. each card proposes a different action which prevents several damages. The actions proposed comply with the workmanship The FIRST part gives a brief geographical, historical and social skills and the tools and materials availability. overview of Bhutan, in order to bring out the complexity of the land and society. Bhutan is a rugged region with a mountainous For having a better overview on Bhutanese scenario, the thesis morphology that make movements in the country hard, both must be read entirely. Despite this, each chapter is written so for people and ideas. In this scenario, the modernization pro- that it can be read separately, according to the reader’s interest. cess brings other urban and social critical aspects. The tension Moreover, the bibliography is organized according to three lev- between “modern” and “traditional” is crucial for retrofitting ac- els, so that it is easy to find the origin of any information: refer- tions. The SECOND part develops a specific feature which brings ences or numerical data in the text are followed by [author, year] out even more the complexity of the scenario: the disaster risk. of the original document; each paragraph has a numerical link to The