Earthquake Resistant Features in Buildings Dr. K. S. Nanjunda Rao Shock Table Test Facility for Evaluating Earthquake Resistant Features in Buildings Research & Development Indigenous design and fabrication of test facility Novel earthquake resistant features for masonry buildings
Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.
Dr. K. S. Nanjunda Rao
Earthquake Resistant Features in Buildings
Peak table acceleration 1.1g
(1.8m length & 600kg mass
Max. swing 400)
Table acceleration response for a swing angle of 300
Fund. Freq. 90Hz
with triangular link
Behavior of building models after 13 shocks
One fourth scale models
Response at top of cross wall
(ERF as per
(ERF as per
R C band at
Sill level and
Response at top of cross wall
Shock table test facility for evaluating seismic performance of buildings was designed and constructed. The table is of size 3.5m by 2.5m and is supported on 4 wheels with ability to move horizontally in one direction on rails. The table can be subjected to shocks through a swinging pendulum of 600kg mass with provision to increase the mass up to 1000kg. On the side of the table opposite to the pendulum, provision is made to generate a reverse shock through a reaction beam. The impulse force that can be given to the table can be varied by changing the swing angle of the pendulum, mass of the pendulum, the material to which the pendulum impacts. The reverse force to the table can also be varied by changing the gap between the table and the reaction beam before the start of the test. The photograph shows two brick masonry building models with different earthquake resistant features on the shock table with instrumentation to measure the table motion and the response of the building models.
It is well known that most of the structures tend to undergo large deformations in the event of a strong earthquake. If the stresses caused due to lateral forces experienced by the structures exceed its strength, the structure yields, if it is ductile. If the structure is brittle, as in the case of un-reinforced masonry, it will suffer brittle failure. The pattern of failure of masonry buildings during an earthquake makes it clear that the prevention of sudden flexural failure of masonry wall is critical to ensure an earthquake resistant masonry structure. Again, since flexural tension can occur on both faces of the wall due to reversal of stresses during an earthquake, there is a need to provide ductile reinforcement on both faces. This can be accomplished by placing vertical reinforcement either on the surface or close to the surface and surrounding the wall, which is termed as “containment reinforcement”. For the containment reinforcement to be effective, it is essential for it to remain hugged to the wall at all times during an earthquake and to deform along with the masonry. In order to meet this objective the vertical reinforcements on either face of the wall have to be connected to each other, by horizontal ties/links passing through the bed joints of masonry. These horizontal ties along with the mortar in the bed joints will ensure strain compatibility between vertical reinforcement and the masonry. Earlier study on the flexure of masonry beams with longitudinal reinforcement wrapped round the beam with links through the bed joints connecting the top and bottom reinforcement has shown substantial ductility with multiple cracks before failure. Containment reinforcement is not primarily intended to increase the lateral strength of the wall, but to permit large ductile deformation and to avoid total collapse. In other words, containment reinforcement will act as main energy absorbing element of the wall which otherwise
has poor energy absorption capacity.
Masonry with containment reinforcement and links/ties connecting them
through bed joints.