Reinforced Hollow Concrete Block Masonry (RHCBM) System for Seismic Resistant Construction

• In this construction system, structurally, each wall and slab behaves as a shear wall and a diaphragm respectively, reducing the vulnerability of disastrous damage to the structure/building, during the natural hazards.
• Due to the uniform distribution of reinforcement in both vertical and horizontal directions, through each masonry element, increased tensile resistance and ductile behaviour of elements could be achieved. Hence, this construction system can safely resist lateral or cyclic loading, when compared to other conventional masonry construction systems. This construction system has also been proved to offer better resistance under dynamic loading, when compared to other conventional systems of construction.

• No additional formwork or any special construction machinery is required for reinforcing the hollow block masonry.
• Only semi-skilled labour is required for this type of construction.
• It is a faster and easier construction system, when compared to the other conventional construction systems.
• It is also found to be a cost-effective disaster resistant construction system, as explained in the next section.

• This construction system provides better acoustic and thermal insulation for the building.
• This system is durable and maintenance free.

Studies on the Comparative Cost Economics of RHCBM

There is a general apprehension that the RHCBM would be a costlier system, as it advocates reinforcing and use of concrete grout in the hollow spaces within the masonry. To dispel this apprehension, the relative cost-economics of RHCBM structure are worked out in comparison with the conventional construction systems.

Structural Schemes                                                Cost(1997) per sq. m, in Rs.

Reinforced Hollow Concrete Block Masonry                          1822 /-

                RC Framed Structure with Brick Masonry infill                     1845 /-

                Load Bearing Masonry                                                             1782 /-

As per the figures of the above table, it reveals that RHCBM is not a costlier construction system. Rather, it has additional advantages of lighter dead weight and increased floor area. These advantages are quantitatively worked out from the fact that, RHCBM is built of 20cm (8") thick hollow block wall, when compared to the 23cm (9") thick one brick wall of RCC framed structure and 34cm (13.5") thick one and half brick wall (for the ground and first floor) of load bearing structure.

Experimental Programme

One of the national R&D laboratories, took up detailed and extensive experimental investigation on the materials, assemblages and full scale wall panels of different kinds of masonry. The testing programme included ten full-scale masonry panels of blocks and bricks with ungrouted, partially grouted, fully grouted and reinforced / unreinforced systems. From these experimental studies, very useful data was obtained to assess the relative performance of each masonry construction system in resisting the in-plane lateral loads under a constant superimposed vertical load.

Full Scale Wall Panel Testing

To give brief account of summary on the experimental programme, the experimental results on the comparison of the ultimate load capacity and ductility of the full scale models of RHCBM panel and reinforced brick masonry panel are presented in the table.

The specifications of the specimens are also listed below:

Specifications of full scale wall panels (with openings)

Size of wall panel : 2.2m(width) X 2.5m(height)

Size of opening : 1.0m(width) X 1.8m(height)

Designed for seismic zone : IV as per IS 1893-1984

Construction method : IS 13828-1993 & IS 4326-1993

Constant superimposed vertical load : Ten tonnes

• Reinforced Hollow Concrete Block Masonry (RHCBM) is a feasible disaster resistant building construction system.
• The studies on comparative cost economics reveal that RHCBM is a cost effective construction system.
• It has additional advantages of increased floor area and lighter dead weight (i.e. it attracts lesser seismic forces).
• The extensive experimental programme has revealed that RHCBM construction technique is structurally more efficient, not only because of its higher ultimate load capacity, but also due to its improved ductility when compared to the conventional reinforced or unreinforced brick masonry. Hence, RHCBM can be adopted as a disaster resistant construction system for low-rise buildings.