HYBRID MASONRY STRUCTURES
Hybrid masonry refers to reinforced masonry used as infill within a structural frame. The combined action of the bracing with the frame acts compositely to brace the system in-plane (shear) and also resist out-of-plane loadings (flexure). Initial efforts have included using reinforced concrete masonry in combination with structural steel frames. The concept was first introduced in 2007 and has been used in low seismic regions in the Midwest and eastern United States. This research is tasked with assessing the performance of hybrid masonry without openings in moderate to high seismic regions.
Hybrid masonry can apply to exterior and interior walls. Exterior walls are usually constructed with a cavity wall veneer (Fig. 1) while interior walls are of single wythe construction (Fig. 2).
|Figure 1: Cavity Wall Construction||Figure 2: Single Wythe Wall Construction|
There are three types of hybrid masonry bracing to resist shear loads. The connectivity of the masonry to the frame determines performance. Conceptually, type I is a non-loadbearing shear wall incorporated within the frame and type II is a loadbearing shear wall. Type III is a reinforced infill that is load-bearing. A more in-depth explanation can be found here.
|Figure 3: Type II Hybrid Masonry||Figure 4: Type III Hybrid Masonry|
Hybrid masonry is currently being designed and used in the Midwest and eastern United States for lateral force resistance. An example of hybrid masonry construction is the completed Garden Hills Elementary School in Champaign, IL. A/E firm BLDD designed the building and called out hybrid masonry walls on their drawings after attending an IMI seminar and consulting IMI and Bentley RAM.
The system has been documented by the International Masonry Institute (IMI) and the National Concrete Masonry Association (NCMA) in several of their technical publications. Publications include:
|Design||IMI Technology Brief Section 2.13.01 and NCMA TEK 14-09A|
|Construction||IMI Technology Brief Section 02.13.02 and NCMA TEK 3-3B|
Further documentation can be found in Select Publications.
Bentley Systems, through a partnership with the IMI and NCMA, has incorporated hybrid masonry into its masonry software, RAM Elements.
An overview of the current research project funded by the National Science Foundation through NEES that is investigating seismic performance of hybrid masonry structural systems can be found here and the accompanying pages. The project includes parametric design studies, experiments on connector plates and large-scale multi-story hybrid test structures, computational simulation studies, dynamic response simulations, trial designs, and education and outreach activities. The research is a partnership with active sub-projects on-going at the University of Illinois at Urbana-Champaign, the University of Hawaii at Manoa and Rice University, with continuous guidance from Biggs Consulting Engineering.[[FootNote(Abrams, Daniel P. “NSF NEESR Research on Hybrid Masonry Seismic Structural Systems.” In Proceedings of the 11th North American Masonry Conference. Vol. 1. Minneapolis, MN: The Masonry Society, 2011.)]]