Resistance of Multi-Wythe Insulated Masonry Walls Subjected to Impulse Loads

Abstract

The overall objective of this project was to define the dynamic flexural resistance of multi-wythe insulated masonry walls with specific emphasis placed on determining the potential application of foam insulation as a blast-resistant material. The project was closely coordinated with full-scale explosive testing conducted by personnel at the Airbase Technologies Division of the Air Force Research Laboratory (AFRL) at Tyndall Air Force Base Florida. The project involved the following tasks: (1) use of finite element (FE) and single-degree-of-freedom (SDOF) analytical models for test analysis and prediction of results, (2) identification of the necessary constitutive relationships of insulating foam(s) for implementation in FE models, (3) synthesis of full-scale test methodology and results, (4) utilization of the data gathered from the full-scale tests to calibrate and validate the FE models, (5) implementation of input parameter studies using the advanced FE models to thoroughly characterize the mechanical behavior of the systems tested, and (6) development of engineering-level resistance definitions and multi-degree-of-freedom models of multi-wythe insulated masonry walls that were compared with FE models.

Four standard wall section designs were recommended by the National Concrete Masonry Association (NCMA). Of these designs, two were selected for full-scale testing: a conventional foam-insulated block wall with a brick veneer and a foam-insulated A-block wall with a brick veneer. Both walls were fully grouted. A single-wythe control wall with equivalent mass and flexural capacity was also included in the tests. Differences in the peak deflection of the conventional wall and of the A-block wall were noticed during post-test analysis. FE models showed that foam is capable of reducing the peak deflection of a wall subjected to impulse loads. However, full-scale testing showed that current construction methodology does not allow the foam to play an active role in the overall resistance of the system.