4201 RUCKER AVE COMMUNITY HEALTH CENTER 2019-04-10

CHCSC Rucker Ave July 12,2017 (2/3 original 1973 drawings for the building,the masonry is not detailed to take lateral loads from the building structure and are not detailed to have masonry lateral loads transferred to the building's steel moment frame system. The current upgrade design is based on new braced frames taking diaphragm loads, including tributary masonry wall seismic forces. Since the braced frames are inset from the exterior wall lines,the goal is to limit forces reaching the exterior masonry by collecting diaphragm forces before the exterior wall line. The braced frame drift,with deflection amplification,is 0.58%and does not take into account stiffness added by the existing building frame. See the attached comparison of wall pier shear stresses,without and with braced frames. The masonry maximum shear stress is roughly 151 psi. Per ASCE 41-13,table 11-2(b)the default lower bound shear strength of reinforced masonry can be taken as those determined from TMS Section 3.3.4.1.2 which would be 4 sqrt( m)or roughly 155 psi. The walls are modelled as concrete in the ETABS model using the effective thickness of 8"masonry grouted at 48"oc(effective thickness 4.6") Item 8. See supplemental calculations for calculations relating to the out-of-plane strength and anchorage of existing reinforced masonry walls. Item 9. Please see revised footing details. The anchor bolt details have changed to use steel plates at the base end to engage the concrete rather than using anchor rod pullout. Item 10. See added detail showing protected zones of the braced frames. Item 11. The brace reinforcing requirements of AISC 341-10 Sec. F2.5b are to account for lost section due to over-slotting of the brace at the gusset connection leaving a hole or gap. In detail 6/S3.1 where the brace is continuously welded,there are no holes or gaps,thus reinforcing is only required at the gusset plate edges where over-slotting is possible. Item 12. See general structural notes revised note 44 identifying demand critical welds. Item 13. See supplemental calculations for brace reinforcing and welding per AISC 341-10 Sec. F2.6. Reinforcing plate length revised for welds to develop plates. Item 14. See supplemental calculations for beam verification. Beams as shown are adequate. Item 15. Please see pages 10-15 of the submitted structural calculations in which the requirements of ASCE 341- 10 Table D.1.1 are checked and verified. Item 16. The column splice shown meets the requirements of ASCE 341-10. The columns are spliced using complete penetration welds which will develop the full flexural strength of the column as well as the full shear strength of the column.