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7 Pleasant Street Engineer report 4-8-11 ! RYAN S. HELLWIG, PE ! STRUCTURAL ENGINEER ! April 8, 2011 Jordi Herold 1 Short Street Northampton, MA 01060 Re: 7 Pleasant Street Northampton, MA The following is a summary of my inspection of the above-mentioned building. Per the order from the Building Commissioner (April 1, 2011), I personally went to the site on April 6, 2011 in order to view one item that was identified as being a potentially dangerous structural condition. Timber Beams at 4th Floor Stair The existing header at the stair opening is a full-dimension 6x8 timber, which appears to be Eastern Hemlock. The existing floor joists were not visible, but judging from old pockets in the brick wall they appear to span perpendicular to the header, and therefore would be loading the header directly. The timber which supports one end of this header is termed a “trimmer” in this application and is a similar 6x8 timber. Because the joists parallel the trimmer they would only load it indirectly, by way of the connection to the header. The header span is 11 feet, and the trimmer span is 16'-4". The header has wide checks visible on one face. The checks extend almost to the center of the timber, and have a slope of approximately 1 vertical to 13 horizontal. The trimmer has a through shake that is greatest near mid-span, which at its widest extends from the mid-point of one side to the mid-point of the bottom face. There is a crack emanating from a small knot at the corner of the beam which does not seem to extend into the body of the timber, but stops at the shake. Because the beams are painted, the knot sizes are difficult to measure, but they all appear to be 1½" or less. Therefore they would qualify for Select Structural grade, were it not for the shake, which force a downgrade to #2. The allowable bending stress for #2 Eastern Hemlock Posts & Timbers is 600 psi. Back-calculating the allowable load on the header gives a safe floor live load rating of about 17 pounds per square foot (psf). See the attached calculation sheet. The calculation sheets show information about loads, span, reactions, and the material. In the loads section there are additional loads to account for the stair stringer and the platform at the street end. The section is a full-dimension 6x8, which is larger than the standard 5½" x 7½". In the case of this header, the #2 rating is conservative, as the lumber grading rules for Select Structural grade even allow for checks up to half of the thickness and 1:12 slope of grain. Such checking is common in timber beams, and is not a significant reduction in bending strength. The section in the middle of the calculation page, titled “Analysis vs. Allowable Stress and Deflection” indicates that the governing criterion is bending, and the “analysis value fb” is 598 ! 28 ALDRICH STREET ! NORTHAMPTON, MA 01060 ! ! VOICE 413-584-HLWG (4594) ! FAX 413-584-HLWFax (4593) ! 7 Pleasant Street Northampton, MA April 8, 2011 pounds per square inch (psi), which is the stress in the beam caused by the combined dead load of 10 psf and a live load of 17 psf. The section also states the “design value” F’b is 600 psi, which is the maximum allowable stress for #2 E. Hemlock Timber, as mentioned above. The design value contains various safety factors, including consideration of checks, shake, knots etc., and is not the stress level that would induce failure. If the “Analysis/Design” ratio exceeds 1.0, the beam does not pass the Code check. See the attached calculation sheet. This live load on the header results in a concentrated force on the trimmer of almost 1100 pounds. A half-bay of floor load from the side of the beam opposite the stair is also included in the analysis. The stress level in the trimmer due to these loads is less than 600 psi. See the attached calculation sheet. The shake results in a corner essentially splitting off from the timber, equivalent to roughly c of the overall section. Shake as well as checking, is typically a limitation on shear strength, and in the calculation sheets the shear is low. Another approach to the stress analysis is to ignore the shake, and consider the beam section to be 6" x 8" with a 4" high by 3" wide triangle missing from the bottom corner, which is also termed wane. In this case, the remaining section would be rated as Select Structural grade, since the knots are small. In this approach the load rating would actually be higher than 17 psf, since the allowable stress for Select Structural is 1250 psi, or more than double that for #2 grade (600 psi), while the reduced Section Modulus is roughly 70% of a solid square 6" x 8" beam. This approach is also conservative, as the Select Structural grade allows for checking, shake and wane, as well as knots up to 1e". Using a stringline, I measured the deflection in the beam at a little more than 1¼", which was in the condition of dead load only. This is considerably greater than the short-term deflection calculated. My assumption is that these beams were installed in the “green”, unseasoned condition, which results in a lower Elastic Modulus, and therefore higher deflections, particularly over long time periods. There is some flex in the floors, as is common in old buildings. In new construction, a beam supporting a residential floor in a sleeping area such as this would be designed for 30 psf. However, because this is an existing building, it is not required by the Building Code to meet the load requirements for new construction. The building predates the creation of a Building Code in Massachusetts, which first was adopted in 1975, and is considered to be grandfathered. Respectfully Submitted, Ryan S. Hellwig Massachusetts Professional Engineer #37300 -STRUCTURAL cc: Louis Hasbrouck, Northampton Building Commissioner attached: (3) Calculation Sheets (WoodWorks Sizer) Page 2 of 2 COMPANY Ryan S. Hellwig PE Structural Engineer Northampton, MA 413 -584 -4594 Apr. 11, 2011 08:02 PROJECT 6x8 Header 4th Floor Framing @Stair 7 Pleasant Street Northampton, MA Header2.wwb Design Check Calculation Sheet Sizer 8.3 LOADS: Load Type Distribution Pat-Location [ft] Magnitude Unit tern Start End Start End Load1 Dead Partial Area 0.00 7.00 10.00 (6.50)* psf Load2 Live Partial Area 0.00 7.00 17.00 (6.50)* psf Load3 Dead Partial Area 7.00 11.00 10.00 (8.17)* psf Load4 Live Partial Area 7.00 11.00 17.00 (8.17)* psf Load5 Dead Point 7.00 60 lbs Load6 Live Point 7.00 100 lbs *Tributary Width (ft) MAXIMUM REACTIONS (lbs) and BEARING LENGTHS (in) : 0' 11' Unfactored: Dead 391 450 Other 665 764 Factored: Total 1056 1214 Bearing: Load Comb #2 #2 Length 0.50* 0.50* Cb 1.00 1.00 *Min. bearing length for beams is 1/2" for exterior supports Timber-other, E. Hem, No.2, 6x8" Lateral support: top= full, bottom= at supports; WARNING: this CUSTOM SIZE is not in the database. Refer to online help. Analysis vs. Allowable Stress (psi) and Deflection (in) using NDS 2005 : Criterion Analysis Value Design Value Analysis/Design Shear fv = 33 Fv' = 155 fv/Fv' = 0.22 Bending(+) fb = 598 Fb' = 600 fb/Fb' = 1.00 Live Defl'n 0.19 = L/696 0.37 = L/360 0.52 Total Defl'n 0.36 = L/369 0.55 = L/240 0.65 ADDITIONAL DATA: FACTORS: F/E CD CM Ct CL CF Cfu Cr Cfrt Ci Cn LC# Fv' 155 1.00 1.00 1.00 ----1.00 1.00 1.00 2 Fb'+ 600 1.00 1.00 1.00 1.000 1.000 1.00 1.00 1.00 1.00 -2 Fcp' 550 -1.00 1.00 ----1.00 1.00 --E' 0.9 million 1.00 1.00 ----1.00 1.00 -2 Emin' 0.00 million 1.00 1.00 ----1.00 1.00 -2 Shear : LC #2 = D+L, V = 1214, V design = 1068 lbs Bending(+): LC #2 = D+L, M = 3178 lbs-ft Deflection: LC #2 = D+L (live) LC #2 = D+L (total) EI = 229e06 lb-in2 Total Deflection = 1.50(Dead Load Deflection) + Live Load Deflection. D=dead L=live S=snow W=wind I=impact Lr=roof live Lc=concentrated All LC's are listed in the Analysis output Load combinations: ASCE 7-05 DESIGN NOTES: 1. Please verify that the default deflection limits are appropriate for your application. 2. Sawn lumber bending members shall be laterally supported according to the provisions of NDS Clause 4.4.1. COMPANY Ryan S. Hellwig PE Structural Engineer Northampton, MA 413 -584 -4594 Apr. 11, 2011 08:04 PROJECT 6x8 Header w/18 psf LL 4th Floor Framing @Stair 7 Pleasant Street Northampton, MA Header3.wwb Design Check Calculation Sheet Sizer 8.3 LOADS: Load Type Distribution Pat-Location [ft] Magnitude Unit tern Start End Start End Load1 Dead Partial Area 0.00 7.00 10.00 (6.50)* psf Load2 Live Partial Area 0.00 7.00 18.00 (6.50)* psf Load3 Dead Partial Area 7.00 11.00 10.00 (8.17)* psf Load4 Live Partial Area 7.00 11.00 18.00 (8.17)* psf Load5 Dead Point 7.00 60 lbs Load6 Live Point 7.00 110 lbs *Tributary Width (ft) MAXIMUM REACTIONS (lbs) and BEARING LENGTHS (in) : 0' 11' Unfactored: Dead 391 450 Other 705 812 Factored: Total 1097 1262 Bearing: Load Comb #2 #2 Length 0.50* 0.50* Cb 1.00 1.00 *Min. bearing length for beams is 1/2" for exterior supports Timber-other, E. Hem, No.2, 6x8" Lateral support: top= full, bottom= at supports; This section FAILS the design check WARNING: This section violates the following design criteria: Bending WARNING: this CUSTOM SIZE is not in the database. Refer to online help. Analysis vs. Allowable Stress (psi) and Deflection (in) using NDS 2005 : Criterion Analysis Value Design Value Analysis/Design Shear fv = 35 Fv' = 155 fv/Fv' = 0.22 Bending(+) fb = 622 Fb' = 600 fb/Fb' = 1.04 Live Defl'n 0.20 = L/655 0.37 = L/360 0.55 Total Defl'n 0.37 = L/357 0.55 = L/240 0.67 ADDITIONAL DATA: FACTORS: F/E CD CM Ct CL CF Cfu Cr Cfrt Ci Cn LC# Fv' 155 1.00 1.00 1.00 ----1.00 1.00 1.00 2 Fb'+ 600 1.00 1.00 1.00 1.000 1.000 1.00 1.00 1.00 1.00 -2 Fcp' 550 -1.00 1.00 ----1.00 1.00 --E' 0.9 million 1.00 1.00 ----1.00 1.00 -2 Emin' 0.00 million 1.00 1.00 ----1.00 1.00 -2 Shear : LC #2 = D+L, V = 1262, V design = 1111 lbs Bending(+): LC #2 = D+L, M = 3305 lbs-ft Deflection: LC #2 = D+L (live) LC #2 = D+L (total) EI = 229e06 lb-in2 Total Deflection = 1.50(Dead Load Deflection) + Live Load Deflection. D=dead L=live S=snow W=wind I=impact Lr=roof live Lc=concentrated All LC's are listed in the Analysis output Load combinations: ASCE 7-05 DESIGN NOTES: 1. Please verify that the default deflection limits are appropriate for your application. 2. Sawn lumber bending members shall be laterally supported according to the provisions of NDS Clause 4.4.1. COMPANY Ryan S. Hellwig PE Structural Engineer Northampton, MA 413 -584 -4594 Apr. 11, 2011 08:05 PROJECT Trimmer w/17 psf LL 4th Floor Framing @Stair 7 Pleasant Street Northampton, MA Trimmer2a.wwb Design Check Calculation Sheet Sizer 8.3 LOADS: Load Type Distribution Pat-Location [ft] Magnitude Unit tern Start End Start End Load1 Dead Point 13.33 400 lbs Load2 Live Point 13.33 700 lbs Load3 Dead Full Area 10.00 (0.67)* psf Load4 Live Full Area 17.00 (0.67)* psf *Tributary Width (ft) MAXIMUM REACTIONS (lbs) and BEARING LENGTHS (in) : 0' 16'-4" Unfactored: Dead 128 381 Other 221 664 Factored: Total 349 1045 Bearing: Load Comb #2 #2 Length 0.50* 0.50* Cb 1.00 1.00 *Min. bearing length for beams is 1/2" for exterior supports Timber-other, E. Hem, No.2, 6x8" Lateral support: top= full, bottom= at supports; WARNING: this CUSTOM SIZE is not in the database. Refer to online help. Analysis vs. Allowable Stress (psi) and Deflection (in) using NDS 2005 : Criterion Analysis Value Design Value Analysis/Design Shear fv fv = 32 Fv' = 155 fv/Fv' = 0.21 Bending(+) fb = 575 Fb' = 600 fb/Fb' = 0.96 Live Defl'n 0.33 = L/591 0.54 = L/360 0.61 Total Defl'n 0.62 = L/317 0.82 = L/240 0.76 ADDITIONAL DATA: FACTORS: F/E CD CM Ct CL CF Cfu Cr Cfrt Ci Cn LC# Fv' 155 1.00 1.00 1.00 ----1.00 1.00 1.00 2 Fb'+ 600 1.00 1.00 1.00 1.000 1.000 1.00 1.00 1.00 1.00 -2 Fcp' 550 -1.00 1.00 ----1.00 1.00 --E' 0.9 million 1.00 1.00 ----1.00 1.00 -2 Emin' 0.00 million 1.00 1.00 ----1.00 1.00 -2 Shear : LC #2 = D+L, V = 1045, V design = 1033 lbs Bending(+): LC #2 = D+L, M = 3054 lbs-ft Deflection: LC #2 = D+L (live) LC #2 = D+L (total) EI = 229e06 lb-in2 Total Deflection = 1.50(Dead Load Deflection) + Live Load Deflection. D=dead L=live S=snow W=wind I=impact Lr=roof live Lc=concentrated All LC's are listed in the Analysis output Load combinations: ASCE 7-05 DESIGN NOTES: 1. Please verify that the default deflection limits are appropriate for your application. 2. Sawn lumber bending members shall be laterally supported according to the provisions of NDS Clause 4.4.1.