Page 57 - EQTips_Eng

IITK-BMTPC Earthquake Tip 28

What is a Confined Masonry Construction? page 2
(b) Different Construction Sequence: economical for the same functional use. For these
Construction sequence is distinctly different for reasons, confined masonry construction is more suitable

the two construction types, namely CM and MRF for low- and medium-rise housing in earthquake prone
with masonry infills. In CM construction, masonry areas than for RC MRF construction.
walls are built simultaneously with reinforcement in
vertical and horizontal RC confining elements, and
concrete is poured in these elements at the end 1.2m
(Figure 3a). In RC MRF construction with masonry
infills, first the RC frame is built (i.e., footings,
1.2m
columns, beams, and slabs) and then the masonry
wall panels are infilled in open bays between RC
columns and beams (Figure 3b).

Figure 4: Advantage of Construction Sequence –

Plain masonry walls built first, are held snugly

by adjoining RC elements cast later

1 st : Masonry walls
nd Construction of
2 : RC verticals and
horizontal elements Buildings with Confined Masonry
poured cast in-situ
rd Design Codes for CM houses have been in place
3 : RC tie-beams and
for more than 50 years in several countries, like Chile,
slab
(a) Mexico and Argentina. But, CM construction has not
been practiced in many countries, including India;
hence, code provisions were not available in these
countries for many years, but now some are being
developed (See Brzev, 2008; Schacher, 2009). Most
design codes lay down prescriptive guidelines for
st architectural, structural and constructional aspects of
1 : RC elements
nd
2 : URM infill walls low-rise CM buildings, and provide requirements for
engineered design of tall CM buildings. These design
(b)
codes are based on experimental verification in

Figure 3: Construction Sequence – (a) CM; and laboratories, analytical research as well as earthquake

(b) RC frame with URM infills performance of such constructions in past earthquakes.

Related - Earthquake Tips
(c) Different Design Complexity:
Tip 12: How do brick masonry buildings behave during earthquakes?
In CM houses, RC elements act primarily in Tip 13: Why should masonry buildings have simple structural
compression and tension (similar to posts in wood configuration?
construction), and the connections between these Tip 17: How do earthquakes affect reinforced concrete buildings?
Tip 29: What are the essential features of confined masonry houses?
elements are pinned (there is no flexure); hence, RC
tie-beams and tie-columns are smaller in size and Resource Material
require less reinforcement compared to RC frame Brzev,S.N., (2008), Earthquake-Resistant Confined Masonry
members. In RC MRF houses, RC members largely Construction, National Information Center of Earthquake
Engineering, IIT Kanpur, www.nicee.org
undergo bending and shearing, and therefore they
Meli,R., et al (2011), Seismic Design Guide for Low-Rise Confined
need to be larger in terms of size and amount of Masonry Buildings, Earthquake Engineering Research Institute,
reinforcement. Prescriptive approach may be adequate and International Association for Earthquake Engineering
for design of low-rise CM houses with typical room Schacher,T., (2009), Confined Masonry for one and two storey buildings
in low-tech environments, A guidebook for technicians and artisans,
sizes and floor heights (See Meli et al, 2011; Brzev,
National Information Center of Earthquake Engineering, IIT
2008), but engineered design approach is required for Kanpur, www.nicee.org
RC MRF houses. Thus, design effort may be

considerably smaller for CM houses than for RC Authored by:

MRF houses. C.V.R.Murty
RC confining elements in CM construction (Figure Indian Institute of Technology Jodhpur, India
4) enhance stability and strength of brittle masonry Sponsored by:

walls, e.g., interaction between masonry walls, Building Materials and Technology Promotion
structural integrity, and containment of earthquake Council, New Delhi, India
damage within the masonry walls. These advantages

lead to superior (more ductile) earthquake performance This release is a property of IIT Kanpur and BMTPC. It may
of CM houses over those of alternative concrete and be reproduced without changing its contents with due
acknowledgement. Suggestions or comments may be sent
masonry building technologies, with relatively lower to: nicee@iitk.ac.in. To see all IITK-BMTPC Earthquake Tips, visit
level of technical effort. Also, CM houses are more www.nicee.org or www.bmtpc.org.