Tie Beams per Florida Building Code - Section 2121

[STR04]

In accordance with FBC Chapter 21‚ Section 2121 there is no allowance for masonry tie beam construction ("U"-block) for commercial construction. How is this handled if the architect wants to use split face cmu and doesn't like to see a concrete banding (conc. tie beam) around his perimeter?

TIA

 

[concretemasonry]

I would suggest contacting the Florida Concrete Products Associated (or similar). They would have good current information on the code on this point.

A masonry bond beam ("U" block) is far superior to pouring an old fashined cast in place plain concrete beam from a standpoint of constructability, reliability and continuity.

Dick

 

[Ron]

As Dick suggested, check with the Florida Concrete and Products Association in Orlando. Unit Masonry style T081 as produced by Rinker Materials and others, allows better tie to the filled cells and creates a more contiguous cast-in-place beam than a U-block. It is essentially a knock-out block that I believe is produced in split-face and split-rib styles, but check with Rinker or other suppliers.

I disagree that a U-block provides for a better installation than cast-in-place. It is cleaner and faster, but it has an inherent discontinuity of low strength material (mortar), and to the filled cells, particularly in uplift conditions.

 

[ron9876]

Are you refering to the High Velocity Hurricane Zone? I am not familiar with any requirements for tie beams in the Florida Building Code except in the HVHZ with references to concrete tie beams/tie columns. I use masonry tie beams regularly for all types of projects.

Concrete tie beams are much stronger, especially as Ron said, for uplift. If uplift or lateral loads are large there are limited options for either epoxy/expansion anchors or embedded anchors. But the cost difference is such that you normally have to come up with a solution.

 

[Ron]

ron9876...yes, he's referring to HVHZ. It limits the use of U-block to R3, one story.

 

[ron9876]

I think this is referring to the tie beam/tie column perscriptive method. I don't think it applies to reinforced masonry per ACI 530. 2122.2.1 says that the tie beam/tie column requirements don't apply to reinforced masonry.

 

[haynewp]

No, the high velocity requires concrete tie columns and tie beams within masonry walls. My only ideas: Is there a way to bond only split face shells to the concrete beam behind them? Or, can you use narrower matching split face veneer units in from of the beam locations and push the concrete tie beam over to allow these to be set in line with the typical face of wall and still maintain reinforcing continuity?

 

[Ron]

haynewp...I wondered about that as well, except that the code gives a minimum size for the tie beam. It makes sense to form and cast, then put a face shell on with mortar.

...or, pending the architect's approval, provide a relief in the wall using a bonded face shell.

 

[ron9876]

It is an either/or type of thing. The tie beam/tie column requirements is a holdover from previous South Florida Building Codes and my understanding is that some jurisdictioms don't accept it anymore because you can't make the numbers work for the masonry panels. At the end of the masonry section it basically says that if you don't want to do all of that use reinforced masonry per ACI 530 with a couple of limitations. You can use masonry tie beams.

The section that STR04 referred to is the requirements if you want to use a bond beam with the perscriptive requirements.

I am referencing the 04 edition. The 07 will go into effect soon but I haven't used it yet so it could be different. But the tie beam/tie column approach is hardly ever used anymore due to cost. It did work very well in Hurricane Andrew.

 

[haynewp]

You're right if you meet all the requirements of the end section. It looks like a 20ft max height can be used for 8" block if you are not using concrete ties.

 

[haynewp]

20 ft "unsupported" height

 

[STR04]

ron9876,

Chapter 21‚ Section 2122‚ (1) 2122.1 Standards state:

The provisions of ACI 530/ASCE 5, Building Code Requirements For Masonry Structures, and the commentary on Building Code Requirements for Masonry Structures, are hereby adopted as a minimum; however, the requirement of the standard shall not supersede the specific requirements of this chapter.

How is there an exception?

 

[STR04]

haynewp,

Chapter 21‚ Section 2121‚ (2)(3)(1)2121.2.3.1 states:

A tie beam of reinforced concrete shall be placed in all walls of unit masonry, at each floor or roof level, and at such intermediate levels as may be required to limit the vertical heights of the masonry units to 16 feet (4.9 m). Well-compacted and confined soil below grade may be considered lateral restraint but only above a point 1 foot (305 mm) below the grade where such restraint begins.

Where do you come up withe the 20 ft unsupported height?

 

[haynewp]

Look at the last section in chapter 21.

 

[STR04]

haynewp, I'm a little slow and don't see this. I looking at the online version so maybe you see something I do not. Can you tell me the specific section? Thanks in advance.

 

[haynewp]

Here I will just paste it

SECTION 2122 HIGH-VELOCITY HURRICANE ZONES-REINFORCED UNIT MASONRY

2122.1 Standards. The provisions of ACI 530/ASCE 5, Building Code Requirements For Masonry Structures, and the commentary on Building Code Requirements for Masonry Structures, are hereby adopted as a minimum; however, the requirement of the standard shall not supersede the specific requirements of this chapter.

2122.2 General.


2122.2.1 Tie columns and tie beams as set forth in Section 2121.2 SHALL NOT BE REQUIRED required where design and construction are in accordance with the provisions of this section.
2122.2.2 Reinforced unit masonry shall be steel reinforced solid-unit masonry or steel reinforced grouted hollow-unit masonry as set forth herein.
2122.3 The design of buildings and structures of reinforced unit masonry shall be by a professional engineer or registered architect.

2122.4 Special inspector. A Florida-registered architect or professional engineer shall furnish inspection of all reinforced masonry structures.

2122.5 Concrete masonry strength.


2122.5.1 In each test of three prisms, the average of the three may be used as the assumed value of f'm.
2122.5.2 In no case shall the value of f'm exceed the lowest break multiplied by 1.25 in any test.
2122.6 Reinforced masonry columns and walls.


2122.6.1 The minimum length of lap for deformed bars in grout, in tension or compression, shall be 48 bar diameters, but not less than 12 inches (305 mm).
2122.6.2 Concentrated loads shall not be assumed distributed across continuous vertical joints, including stack bond joints, unless reinforcing elements are designed and provided to distribute such loads.
2122.6.3 Reinforced masonry bearing walls shall have a nominal thickness of at least 1/30 of the unsupported height or width, whichever is the shorter, but not less than 8 inches (203 mm).
2122.6.4 Anchorage requirements.
2122.6.4.1 Reinforced masonry walls shall be securely anchored to adjacent structural members such as roofs, floors, columns, pilasters, buttresses and intersection walls.
2122.6.4.2 Masonry walls shall be anchored to all floors and roofs that provide lateral support to such walls.
2122.6.4.3 Such anchorage shall provide a positive direct connection capable of resisting the horizontal forces as required in Chapter 16 (High-Velocity Hurricane Zones), or a minimum force of 200 pounds per lineal foot (2919 N/m) of wall, whichever is greater.
2122.6.4.4 Required anchors shall be embedded in reinforced grouted cells.
2122.6.4.5 Wood framing connected by nails shall not be considered as acceptable anchorage.
2122.6.5 Mortar and grout.
2122.6.5.1 Vertical cells to be grouted shall provided vertical alignment sufficient to maintain clear, unobstructed, continuous, vertical cores measuring not less than 2 inches by 3 inches (51 mm by 76 mm).
2122.6.5.2 Vertical grout barriers or dams of solid masonry spaced not more than 25 feet (7.6 mm) apart shall be provided across the grout space in the entire height of the wall to control the flow of grout horizontally.
2122.6.5.3 Grout shall be a plastic mix having a maximum slump of 9 inches 1 inch (229 25 mm).
2122.6.5.4 Grout shall be placed before any initial set has occurred, but in no case more than 11/2 hours after the mix-designed water has been added.
2122.6.5.5 Grouting shall be a continuous operation in lifts not exceeding 4 feet (1.2 m) and a maximum pour of 12 feet (23.7 m).
2122.6.5.6 Grouting shall be consolidated between lifts by puddling, rodding or mechanical vibration.
2122.6.5.7 The grouting of any section of wall between control barriers shall be completed in one operation with no interruptions exceeding 1 hour.
2122.6.6 Bearing. Precast floor and roof units supported on masonry walls shall provide minimum bearing of 3 inches (76 mm) and anchorage in accordance with Section 2122.6.4.
2122.6.7 Protection of masonry. Unfinished work shall be stopped back for joining with new work; toothing being permitted only with the approval of the special inspector.

 

[ron9876]

This section of the code isn't written very well. There are also allowable stresses in the beginning of the section and they also only apply to the tie beam/tie column requirements. What really happened was the people that ran the old South Florida Building Code didn't really trust reinforced masonry. They finally had to give in because it is used in the rest of the country so they added a small section at the end that says ok you can use ACI 530 if you want to and kept the old tie beam/tie column requirements. There are politcs in code writing also.

The HVHZ requirements in the FBC are really the old South Florida Building Code with a new name. It doesn't have many people or resources involved to keep it current. So you get stuff like this. You should have seen the original HVHZ version of the FBC. It had all kinds of nonsense including you couldn't use a non filled steel deck as a diaphragm.

But the requirements are ACI 530 with th limited provisions at the end of the section.

 

[STR04]

heynewp,

Can you have a situation where your facility doesn't fall under a threshold building and some local building inspector will be doing the masonry inspection and therefore the masonry inspection is not conducted by a special inspector who is:

2122.4 Special inspector. A Florida-registered architect or professional engineer shall furnish inspection of all reinforced masonry structures.

 

[ron9876]

I'm not sure about the entire state but Dade and Broward Counties require reinforced masonry to be inspected by a special inspector which is different from the building department.

 

[STR04]

Since high velocity on pertaines for Broward and Dade I guess that answers that.

Chapter 2‚ Section 202‚ (HIGH_VELOCITY_HURRICAN)
<<HIGH-VELOCITY>> HURRICANE ZONE. This zone consists of Broward and Dade counties.

Thanks for your help.