Guide for Seismic Strengthening of Buildings
- The guide's premise is that the surviving building stock is not safe stock. Buildings that withstood 12 January 2010 were weakened by it and may not withstand another earthquake in their present state, so strengthening has to be treated as a separate task from repair and reconstruction.
- It treats two hazards in one document because Haiti faces both, and the second half is about roofs: seismic strengthening occupies the bulk of the guide, and cyclone strengthening is handled through the behaviour of a building in a cyclone and the solutions for strengthening a roof covering.
- Diagnosis is split into qualitative and quantitative, with the objectives of a pre-strengthening diagnosis set out first. That ordering matters in practice: it tells an engineer what the diagnosis is for before it tells him how to do it.
- Non-structural elements get their own section rather than being left to the end, which is where much of the injury risk in a moderate earthquake actually sits.
- Cost is treated as part of the engineering rather than as an afterthought, with a dedicated section on evaluating the cost of strengthening work, followed by technical annexes.
- The institutional anchor is named: the MTPTC's Public Works Directorate, through the Technical Building Evaluation Office (BTEB), sits at the centre of repair and reconstruction activity, which makes strengthening and risk mitigation part of the ministry's remit.
- The displacement figures it works from are worth recording: the earthquake left 1.3 million people homeless, and 766,000 people took refuge in towns that had not been hit.
- The production consortium is unusual and worth noting for provenance: the World Bank, UNOPS, Build Change, Miyamoto International and Swiss Cooperation contributed financially and technically.
MTPTC's guide to seismic strengthening of buildings, built around one governing quantity: the Wall Area Percentage. The evaluation calculates the existing wall area percentage for a building, compares it with the required percentage for its level, and the strengthening options follow arithmetically, either raise the existing percentage or reduce the area that has to be resisted.
That framing is what makes the guide usable by an engineer without a full dynamic analysis. Measures to raise the wall area percentage include adding new walls, and the transverse wall area percentage must exceed the required value. The guide is explicit that lowering the chosen performance level from 90 to 60 percent minimizes rehabilitation needs for structures with minor defects, which is a stated proportionality rule rather than a hidden assumption.
The remaining criteria are geometric and checkable on site. On torsion, walls must cover all exterior faces of the building or at least 25 percent of the plan dimension, and the distance between the centre of mass and the centre of rigidity must be less than 20 percent of the building's maximum width in both directions; openings smaller than 25 percent of a wall's length are treated differently from larger ones. On foundations, soft or sloping sites above 10 percent require continuity between foundation elements, including under stairs, and masonry units must have no less than 40 percent net solid area.
How to cite
Ministry of Public Works, Transport and Communications (MTPTC), 2011, Guide for Seismic Strengthening of Buildings, https://www.mtptc.gouv.ht/media/upload/doc/publications/GUIDE-RENFORCEMENT.pdf