17.34.070 Material requirements.
A. Existing Materials. All existing materials utilized as part of the lateral force resisting system shall be in sound condition or shall be removed and replaced with new materials.
B. Existing Unreinforced Masonry.
1. General. Unreinforced masonry parapets that exceed the maximum height in Section 17.34.100(C) shall be tested as specified in this subsection. Masonry that does not meet or exceed the minimum standards established by this chapter shall be removed and replaced by new materials or shall have its structural functions replaced by new materials and anchored to supporting elements.
2. Lay-up of parapets. The facing and backing shall be bonded so that not less than four percent of the wall surface of each face is composed of solid headers extending not less than four inches into the backing. The distance between adjacent full-length headers shall not exceed twenty-four inches either vertically or horizontally. In walls in which a single header does not extend through the wall; headers from opposite sides shall overlap at least four inches; or headers from opposite sides shall be covered with another header course overlapping the header below at least four inches. Wythes of walls not bonded as described above shall be considered as veneer. The veneer wythe shall not be included in the effective thickness used in calculating the height to thickness ratio of the wall unless it is bonded and anchored to the backing in a manner acceptable to the building official.
3. Mortar.
a. Tests. The quality of mortar in unreinforced masonry wall shall be determined by performing in-place shear tests in accordance with UBC Standard 24-40. Alternate methods of testing may be approved by the building official.
b. Location of tests. Shear tests shall be taken at locations representative of the mortar conditions throughout the entire building. The exact test location shall be determined at the building site by the engineer or architect in responsible charge of the structural design work. An accurate record of such tests and their location in the building shall be recorded and these results shall be submitted to the building official for approval as part of the structural analysis.
c. Number of tests. The minimum number of tests per wall or line of wall elements providing a common line of resistance to lateral forces shall be as follows: Two tests per wall with a minimum total number of eight tests or one test per one thousand five hundred square feet of wall area; whichever results in the greater number of tests.
d. Minimum quality mortar.
(1) Mortar shear test values; vto; shall be obtained for each in-place shear test in accordance with the following equation:
vto = vtest - PD+L/AW
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WHERE: |
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|---|---|---|
|
Vto |
= |
Mortar shear test value; in psi. |
|
vtest |
= |
Shear stress at incipient cracking for each in-place test per UBC Standard No. 24-7. |
|
PD+L |
= |
Actual dead plus live load in place at the time of testing, in pounds. |
|
AW |
= |
Area of the wall supporting PD+L at each in-place shear test. |
(2) Individual unreinforced masonry walls with vto less than 30 psi shall be pointed prior to retesting.
(3) The mortar shear strength; vto; is the value in psi that is exceeded by eighty percent of all of the mortar shear test values, vto.
(4) Unreinforced masonry with mortar shear strength; vto; less than 30 psi shall be removed or pointed and retested or treated as veneer.
e. Pointing. All deteriorated mortar joints in unreinforced masonry walls shall be pointed according to UBC Standard No. 24-42. Nothing shall prevent pointing with mortar of all masonry wall joints before the tests are made.
(Ord. 1882 NCS §1 (part), 1992.)