The challenge

Introducing a new masonry category

While unreinforced rubble stone masonry (URM) is officially banned in most parts of the world due to its poor performance in earthquakes, the technique is still widely used in many countries. When properly designed and reinforced, these heavy buildings can withstand high seismic impacts. A key feature for improving their structural integrity is the use of horizontal seismic bands.

Smart Shelter Foundation built their schools with horizontal concrete bands, and all withstood the 2015 earthquakes in Nepal without significant damage. However, more in-depth scientific proof is needed regarding the exact behavior, placement, and number of bands in seismic design.

The aim of our research is to assess, validate, and optimize horizontal seismic bands in stone masonry. And to officially recognize HRM as a distinct masonry typology, as a crucial step toward reinstating the technique into seismic codes worldwide.

State of the art

Currently, three main categories of masonry are recognized:
Unreinforced masonry (URM)
Reinforced masonry (RM)
Confined masonry (CM)

The specific typology with horizontal reinforcing bands behaves structurally differently from these three categories. This technique is currently classified as "unreinforced masonry with reinforcements," which is highly confusing and problematic because it still classifies the technique as "unreinforced," and therefore unsafe, even though it is known to resist large seismic impacts.

To gain international recognition for this distinct technique, Smart Shelter Foundation advocates for the addition of a fourth category of masonry: Horizontally Reinforced Masonry (HRM).

Our research approach

The 4HRM project aims to develop a holistic, novel, and simplified methodology to fully understand the role of horizontal seismic reinforcements and determine the optimal arrangement of bands (number, dimensions, and positions) in rubble stone masonry buildings. A generally accepted methodology for this is currently non-existent.

Our research is divided into three key strategies:

1. Material strategy: We will test the mechanical properties of rubble stone samples, cement mortar mixtures, and their combination into rubble stone masonry. This data will complement international databases and is necessary for calculating and modeling stone masonry buildings. Read more here.

2. Technical strategy: This will involve both in-plane and out-of-plane numerical analyses of various case study buildings.

• A benchmark exercise will be performed to compare and calibrate different software packages and modeling approaches before we begin on the case study buildings. Read more here.
  
  

• Out-of-plane analyses aim to prove that horizontal bands make this type of collapse a non-critical failure mechanism. Read more here.
  
  

• In-plane analyses of various case study buildings by using current state-of-the-art calculation and modeling approaches. This work will include parametric studies and sensitivity analyses, and the results will be compared with simplified hand calculations.

3. Dissemination strategy: All of our outputs and findings will be peer-reviewed and published for free through open-source journals and our website. We have also launched an international call to action to formally recognize HRM as a distinct masonry category in seismic building codes. Read more here.

Get involved

Parts of this research are open to students and experts with an interest and expertise in material testing, the development of test standards, and masonry modeling. By following our research methodologies, you can help multiply our impact by replicating and cross-checking our findings. If you are interested in exchanging knowledge or joining the research, please get in touch.