Mt. San Jacinto College Catalog. Effective Summer Summer San Jacinto Campus. N. State Street. San Jacinto, CA Building Code Requirements and Specification for Masonry Structures – MSJC (Masonry Standards Joint Committee) (TMS /ACI /ASCE 5 and TMS. by reference the editions of the MSJC code and MSJC specification (refs. 3, 5). The MSJC code covers the design of concrete masonry, clay masonry.
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Named for Professor Paul Haller, the Haller Award recognizes an individual engineer or engineering firm that has enhanced ,sjc knowledge of masonry in practice. Ed has an mzjc background in masonry design, research, and teaching that has resulted in advancements in masonry design practice and code development.
He continues to advance masonry knowledge through his ongoing design and investigation practice, as well as disseminate that knowledge through his teaching activities. The Haller Award committee congratulates him on his achievements and selection. Masonry structures have been built to endure; noteworthy masonry structures constructed hundreds, even thousands, of years ago, still exist. Masonry design and construction produces architecturally award-winning structures which are safe and durable.
The main masonry materials in use today are brick, concrete masonry and glass block masonry. The primary masonry design methods in use today are allowable stress design ASDstrength design SD and prestressed masonry design. These two documents, along with their respective commentaries are jointly known as the Masonry Standards Joint Committee documents, or the MSJC documents. These three organizations formed the Masonry Standards Joint Committee.
The process of harmonization of design provisions in mxjc MSJC documents dates back to the edition of the Code and Specification. The edition of the Code was comprised of twelve discrete chapters, which had almost no overlap. The edition of the Code and Specification reformatted the material into five chapters. Material common to different design methods, seismic design requirement, and quality assurance requirements were placed together in Chapter One.
Building Code Requirements and Specification for Masonry Structures, 2008
The edition of the Code and Specification had separate chapters for ASD and prestressed masonry design. There was a place holder for a future Limit States Design.
Section was for the Strength Design of Masonry. Many MSJC members had serious concerns about the requirements in this section, and set aside the work on a Limit States Design procedure to revise these strength provisions.
This allowed them to include a SD chapter for masonry in the MSJC, so that they could begin shaping a workable set of strength design provisions. The major mwjc effort in the MSJC was to change the design equations for anchor bolts, so that a designer would get approximately the same bolt spacing using either the ASD procedures or the SD procedures. The masonry modulus of rupture is used for the design of unreinforced masonry. It is also used in reinforced masonry to determine the cracking strength and the deflection of masonry elements just prior to cracking.
The MSJC harmonized the modulus of rupture between the various design methods. Since ancient times, masonry corbels have been used to help translate a wall out-of-plane. There is a saying that success begets success. Encouraged by the positive mjc results of the and editions of the MSJC, the MSJC committee harmonized bearing requirements; effective compression width and provisions for concentrated loads, and moved all of these provisions to Chapter One.
The committee also gathered most of the provisions for beams and columns and moved them to Chapter One. Many of the requirements for anchor bolts, such as placement, effective area and embedment length, were consolidated and moved to Chapter One.
The anchor bolt provisions related to the design equations were left in the respective design chapters. The MSJC, and its industry msnc also began the process of moving requirements out of the IBC and placing them in the masonry standard.
Much effort had been spent in previous code cycles, trying to maintain provisions in the IBC and the MSJC which were exactly the same in the two documents.
For example, both documents had hot and cold weather requirements.
If the provisions were not exactly aligned, users were left to wonder why and whether one provision was deliberately different from the other. For several decades, the IBC, and one of the predecessor legacy codes, required a 1.
The MSJC added a set of design assumptions at the beginning of the reinforced masonry portion of the ASD chapter to mirror the design assumptions which previously existed at the beginning of the reinforced masonry portion of the SD chapter. With the availability of robust SD provisions, which have been substantiated by many laboratory test programs, the MSJC continued the harmonization process by reviewing these research results and by performing numerous trial designs comparing the results of the reinforcement requirements of elements designed by both the ASD and the SD procedures.
We also reviewed historical code design provisions. The trial designs included both brick and concrete masonry; walls with a large variation of aspect ratio, walls with both very low and moderately high axial loads and a wide range of strengths.
The goal was to encompass the gamut of designs that structural engineers encounter. The trial designs indicated a very poor correlation between the flexural capacity of elements designed using SD and the same element designed using ASD and the 0.
Masonry Designers’ Guide, 6th Edition
The increase in the allowable flexural stress limit applies to all load combinations. Senior structural engineers will remember that the old working stress concrete design flexural limit was 0. The trial designs confirmed that this could lead to unconservative designs. So masonry has now joined the other materials and eliminated this stress increase.
Other stresses were also increased, although not all allowable stresses have been increased in the edition of the code.
STRUCTURE magazine | Harmonization of Allowable Stress Design and Strength Design of Masonry
The composite action shear stress limit has been increased in ASD. The allowable steel reinforcement stress for flexure, direct tension and shear has been increased to 32 ksi. The allowable axial stress limit was not increased, because there was concern 22008 between members of various subcommittees as to what effect msjd could have.
For example, the prestress committee was unsure of the ramifications of this change on the design of prestress elements. This has been set aside as ongoing work for a future cycle. This is because masonry is a non-homogeneous anisotropic material.
In ASD, the safety factor for reinforcement is 2. Because of 20008 inconsistencies, ASD will still be slightly more conservative in almost all cases. In the past, shear analysis in ASD of reinforced masonry has been treated very differently than in Mejc.
In ASD, the shear stress on an element was calculated and compared to a lower level allowable stress which could be resisted by the masonry alone. If the msic stress on the element was less than the lower level allowable stress, the design was adequate, although reinforcement to meet prescriptive detailing requirements would still be required.
If the shear stress on the element exceeded the lower mscj allowable stress, but was less than a higher level allowable limit stress, an amount of reinforcement was determined which could carry the entire shear. If the shear stress on the element exceeded the higher level allowable limit stress, the section was inadequate and had to be made stronger, thicker or longer. In SD, the shear demand on an element was compared to the shear capacity of the masonry and the reinforcement working together.
In both design methods, the shear capacity was adjusted for the shear span of the element to promote ductility.
The shear capacity of such members was reduced to promote a ductile failure mode. Long squat elements are typically shear dominated, but generally have excess shear capacity. No reduction of the shear capacity of such members is required.
Recent research compared eight different design methodologies, used, or recommended for use, around the world, with the results of laboratory testing. This research concluded that, of the eight methodologies, the TMS SD for shear was the best predictor of shear capacity and that the TMS ASD for shear in reinforced masonry was the worst predictor of shear capacity.
Based on this research, the MSJC modified the SD methodology for shear capacity and converted it to an ASD methodology for shear stress, based on the stresses in both the masonry and the reinforcement.
The modification kept the same terms in both methodologies, but modified reduced the constants which were applied to these terms. Particular attention was given to Special Reinforced Masonry Shear Walls, and these trial designs indicated that further reduction of the constants in the equations was required to achieve approximately the same results, regardless of the design method.
While much progress has been made, there is still room for additional harmonization efforts. As noted above, some allowable stresses have not yet been harmonized and additional harmonization between ASD, SD and prestressed design has been held over as the work of future code cycles.
May, By Edwin T. In ArticlesCodes and Standards Comments 0. Medieval tower with masonry corbels.
Building Code Requirements and Specification for Masonry Structures, – The Masonry Society
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