MDG-7 Masonry Designers' Guide - 7th Edition?

[Archie264]

Has anyone here used this book or one of it's preceding editions? If so, do you recommend it? Or are there better resources to consider? I particularly like books with a lot of example problems. Thanks.

 

[KootK]

I've heard good things about th MDG but I don't own a copy myself. I do however, have this book which is excellent and chock full of details and extensive examples: Link.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[concretemasonry]

The best references for masonry are the MDG and the ACI 530 Code and Specifications that is an industry standard written by the ACI, TMS (The Masonry Society), BIA (Brick Insitute of America) and the NCMA (National Concrete Masonry Association) and distributed by the ACI since they had the mechanism and desire for publishing and selling documents. ACI 530 covers all types of masonry (brick, block, stone) and the design methods beginning with empirical and through working stress and more specific methods with examples and explanations for unreinforced, partially reinforced and reinforced masonry structures that are grouted as needed.

The ACI 530 is commonly adopted as written in many national and local codes in the U.S. and many other countries. It was an outgrowth of a NCMA document from the early 1960's that was used extensively and then was morphed into the current document by various association engineering groups that also are active in the ASTM specifications for materials standards, test methods and and sampling methods. - It is based on wall performance (by testing) and not just individual materials that make up the wall.

These references also give some reasons for the recommendations in ASTM 270 (mortar) to use the weakest mortar possible and why many engineers specify a maximum allowable compressive strength for masonry grout or how you can get a 2 block high hollow concrete masonry prism with a 4800 psi using 2500 psi mortar.

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[Archie264]

Kootk, thanks for the recommendation; I might get that one instead.

Concretemasonry, thanks also. I have ACI 530 but I am looking for a companion piece.

 

[KootK]

These references also give some reasons for the recommendations in ASTM 270 (mortar) to use the weakest mortar possible and why many engineers specify a maximum allowable compressive strength for masonry grout or how you can get a 2 block high hollow concrete masonry prism with a 4800 psi using 2500 psi mortar.

I don't know this story CM. Could you elaborate a bit?

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[concretemasonry]

Kook -

ASTM 270 has a note(#1?) in the appendix that suggests to use the weakest mortar possible to carry the structural load, since the higher compressive strength mortars do not have many of the benefits as lower strength mortar. - You have more workable mortar that is not as critical to use and maintain usability and quality on a job site situation.

As far as the strength of a 2 block high CMU hollow prism, the failure mode is typically a diagonal shear failure through the assembly and correlates to the individual unit compressive strengths. - The strength measurement for mortar is a cube in a non-absorptive mold that typically has a diagonal failure, while a mortar joint bonded to the masonry units essentially is a 3/8" thick layer that is in confined compression.

Just a part of looking at masonry design criteria and performance as based on results of historic performance of assemblies and walls (composite results) rather than individual material properties.

I had some block and prisms made with various strengths of units and mortar. The most difficult was using 8500 psi CMUs (net strength) and 2200 psi mortar (mortar cubes). The CMU were difficult to test because a typical lab compression testing machine did not have a thick enough platen to prevent unequal loading because of deflection. The the load was concentrated on the center portion as the platen deflected. A new, thick platen had to be fabricated to convert a 6" diameter concrete cylinder set up to handle the wider and higher prism test samples. Fortunately, the lab had photos of samples showing the failure to provide insight. The strength of the units tested were beyond the norm, but were conducted in able the production of design tables for 4500 psi to give the option/confidence for the designer to use or go to a 2000 or 3000 psi net f'm that was more common.

Fortunately, the ASTM standards for masonry testing and materials have not changed significantly for decades, so the results of the vast number of older results could be correlated.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.