الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 119 |  |  |
| | | from | 119 | | |
Abstract
CONCLUSIONS
5.1 Summary:
Latest studies investigated the out-of-plane response of reinforced masonry shear walls (RMW) with boundary elements (BEs). These results showed that adding BEs on the edges of the walls enhances their blast resistance. Therefore, the influence of alternative configurations and different design paramaters of RMW with BEs were investigated on the out-of-plane performance of RMW under far-field blast loads. In this study, six different configurations were selected by changing the location and number of BEs within one wall, while wall design parametes included BEs sizes, horizontal reinforcement ratio, vertical reinforcement ratio, boundary conditions, aspect ratios of RMW, axial load as well as the blast load scenario in terms of impluse.
5.2 Conclusions:
The results from the numerical analysis carried by Opensees, reported in this thesis explores and points out the improvements that boundary elements add to RMWs out-of-plane performance under blast load scenarios. The following conclusions are based on the research results discussed in the preceding chapters:
• The static push-over out-of-plane analysis confirmed as expected that increasing the number of BEs enhances RMWs elastic sitffness, resistance, as well as the post peak behavior. The resistance was enhanced up to 170% when 3 BEs were added. While the rectangular wall has the lowest stiffness and resistance among other RMWs with BEs but the highest ductility. This was attributed to the higher overall reinforcemnt ratio as as the dual reinforcement layers in BEs.
• The static support rotation (i.e. displacment response) of RMWs decreases on average by 25% when 2 BEs are added to the rectangular wall. This may result in lower ductility performance for such configurations, yet considering the levels of damage according to ASCE 59-11, will result in enhanced performance under blast load scenarios. This was clearly recorded when configuration were analyzed under blast wave scenario, Wall 3B showed lower support rotation by approximatley 50% than traditional rectangular wall.
• The effective width of BEs can be calculated as per the empirical equations of codes based on the system of the wall, number and locations of BEs. Also the thickness of BEs is not affecting the effective width which conforms with the empirical equations that depend only on the width beams not the thickness.
• The less the difference between the ratio of deformations at mid-span and edges for RMW with 3 BEs and RMW with 2 BEs, the less need for using 3 BEs.
• For walls with aspect ratio “H/L” 1 or more, RMWs with 2 BEs at edges are more optimized than RMWs with 3 BEs at edges and centre. This is because – in case of using 3 BEs – the spacings between the BEs are not much more than the effective width of BE so there is no need to use 3 BEs. This is also confirmed by the low difference between the ratio of deformations at mid-span and edges for Wall 3B and Wall 2B-E. The percentage of damage for Wall 2B-E is less than that of Wall 3B by 0.8%, due to the higher portion of load carried by the middle BE which increased slightly the strains and so the damage for RMW with 3 BEs.
• For walls aspect ratio 0.5 “increasing width to double the height”, RMW with 3 BEs becomes more effective as the spacing between the BEs are greater than the effective width. RMW with 2 BEs at edges exhibited support rotations higher than RMW with 3 BEs by 58% at mid-span, and higher damage by 4.7%. This is also confirmed by the high difference between the ratio of deformations at mid-span and edges for Wall 3B and Wall 2B-E.
• Regarding the location of BEs for RMWs with 2 BEs, it is concluded that for aspect ratio 1 or more, the BEs are more effective to be at edges. This is confirmed by the small difference between the ratios of deformations at mid-span and edges. While for aspect ratio 0.5, the difference was very big so it is better to use the 2 BEs at 0.2 the length of the wall, which enhance the deformations and the damage, as the damage decreased by 2.1%.
• The thickness of the BEs is a very effective parameter in decreasing the deformations, support rotations and damaged areas of the RMW. It is concluded that the use of 2 BEs at edges with four-block-thickness gives almost the same behavior as the RMWs with transverse walls in the opposite direction. Comparing between the percentage of damages, RMW with 2 BE at edges with two-block-thickness got damage less than the rectangular wall with 19.1% and higher than the RMW with 2 BE at edges with four-block-thickness by 4.7%. While RMW with 2 BE at edges with four-block-thickness exhibited damage higher than that of RMW with hinged supports at edges by only 0.8%.
• One BE at middle is not recommended solution if another configuration of two BEs can be valid, which confirms with ASCE 59-11 that recommends to use minimum of two boundary elements at edges with gives more redundency to the wall in case of failure.
• Axial load and horizontal reinforcement slightly enhance the behavior of RMW under blast loading.
• Vertical reinforcement somehow affects the damage and deformations to decrease rather than the horizontal reinforcement.
• Fixed boundary conditions at top and bottom sides increase the stiffnesses of RMW walls effectively and in turn decreases the deformations and support rotations greatly, but this is hard to achieve in real life.
5.3 Recommendations for Future Research:
On the base of the analytical study developed and the investigations carried out throughout this research, a few recommendations for future work are presented as follows:
• Generate pressure – impulse curves to quantify the blast resistance of RMWs with different BEs configurations relative to various levels of damage defined by ASCE 59-11.
• Assess the different RMWs configurations relative to their response limits “ductility ratios and support rotations” according to the detected levels of damage defined in codes.
• Study the different BEs configurations and different walls parameters under blast loading for walls with different materials as reinforced concrete walls and infill walls.
• Study the effect of horizontal and vertical reinforcement on the out-of-plane behavior of RMWs under higher blast waves