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Jonathan Hill Structural AE Faculty Consultant – Dr. Hanagan Lynde and Harry Bradley School of Technology & Trade Milwaukee, Wisconsin ____________________________________________________________________________________

Structural Concepts / Structural Existing Conditions Report

October 6, 2004 ____________________________________________________________________________________

Executive Summary

The following report discuses the existing design conditions of the Lynde and Bradley Tech high school. It provides an overview of the structural components of the building. The following report is organized into four parts:

Introduction and Summary

This section explains the function and design concepts behind the building. Comments regarding the architecture and construction of the building are also provided.

Design Codes and Criteria

Codes and design criteria are summarized and certain criteria are established for required fire resistance. Minimum thicknesses and cover distances are given and the geotechnical report provides essential information on the foundation depths and strength of surrounding bearing soil.

Structural System

Typical framing plans, framing elevations and sections are used to describe the layout of typical areas. The material properties are introduced as they apply to the systems of the building. Two different systems are discussed in detail. One, being the main structural system, a cast-in-place pan and joist system is broken down in terms of its foundation, columns, and typical framing. The other system is the roof system which is quite complicated. Steel joists are used to support a barrel vault roof as well as a flat roof and smaller canopies. The vault roof is comprised of many components, but it simply connects to the main structural system through embed and bent plates. This detail seems to simplify the lateral system which comprises of several steel members and most of the concrete frames.

Calculations

All details relating to design loads and how they relate to the described structural systems are calculated and explained. Wind and seismic forces are analyzed and their affect on the building is diagramed. Shear forces of the mentioned loads are summed and shown acting on the building frames. Finally, spot checks regarding a simple pan and joist as well as a single concrete column are calculated. The joist design tends to concur with the engineers decision, whereas the column design seems to be lacking information and will be looked at in more detail at a later time.

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Building Summary

Introduction The Lynde and Harry Bradley School of Technology & Trade is a high school owned by the Milwaukee Public School District. The high school rests on the near south side of Milwaukee and is bounded by West National Avenue on the south, South Third Street on the east, South Fourth Street on the west and West Virginia Street on the north. The existing Milwaukee Tech High School was demolished and the new building along with an athletic practice field, asphalt playing courts, and playground for an adjacent elementary school now fills the space. The 280,000 square foot building contains five stories, one occurring below grade, the others above grade.

Architecture The architecture of the Bradley Tech high school expresses the state-of-the-art teaching equipment that is used within. The school consists of two attached buildings; the North Building housing administration, athletic and support spaces; and the South Building housing academic classrooms and technical lab spaces. The structure is a flexible design aimed to facilitate current and future technologies and consists of a concrete frame and steel roof structure. The engineering and design of the facility makes extensive use of “green-build” principles including natural day lighting, recycled building materials, and an energy-efficient steam heating and cooling system.

Building Envelope The building consists of a cast-in-place concrete frame which supports a façade of masonry, metal panel, and glazed curtain wall. The roof utilizes curved metal panel and flat built-up asphalt roofing systems.

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Codes and Criteria Design Codes and Standards

The design code used is the Wisconsin Administrative Code along with the State of Wisconsin Department of Commerce-Safety & Buildings Chapters Comm 50-64 and the City of Milwaukee Code of Ordinances Chapter 257-Schools. General ACI, ASCE 7, and AISC codes have been followed and interpreted by the engineers and designs fully comply with nationally accepted standards. Load combinations and safety factors were fully analyzed and included in the final design of the building.

Design Criteria

Fire Resistance

Concrete designed for 2 HR rating (worst case) COMM 51.045 FIRE RESISTIVE STRCT COMPONENTS

Columns – min cover 1 1/2” Girders & Bms – min cover 1 1/2” Joists – min cover 1 1/2” min web 4” top slab 5” Walls – min cover 3/4” Slabs – min cover 3/4” min thickness 5”

Geotechnical Report Report prepared by Professional Service Industries, Inc. PSI Project # 052-05032 July 11, 2000 ALLOWABLE BEARING CAPACITY 5000 PSF Min wall footing = 2’-0” Min column footing = 3’-0” Footing bearing depth = 4’-0” min below exterior grade Typical spread and strip footings are recommended Max Settlement = 1” Max differential settlement = 3/4” Below Grade Walls: γ= 135 pcf Friction factor (worst case) Design Pressure

Ka = 0.42 57 PCF Kp = 2.66 359 PCF Ko = 0.59 80 PCF

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Structural System Materials

Cast-in-Place Concrete

F’c = 4000 PSI at 28 days F’c = 5000 PSI at 28 days Concrete Masonry Units ASTM C90 Type “N-1” Masonry Core Fill F’c = 3000 PSI at 28 days Reinforcing Bars ASTM A615 (Grade 60) Welded Bars and Anchors ASTM A706 (Grade 60) Welded Wire Fabric ASTM A185 Keydeck Mesh, No. 2160-2-1619 ASTM A82 Steel Fibers 1 1/2” ASTM A820

Structural Steel WF Beams and Columns ASTM A572 (Grade 50 - Fy = 50 ksi) Cellular Beams ASTM A572 (Grade 50 - Fy = 50 ksi) Other Shapes and Plates ASTM A36 (Fy = 36 ksi) Square or Rectangular Tubes ASTM A500 (Grade B - Fy = 46 ksi) Round Tubes ASTM A500 (Grade B - Fy = 42 ksi) Bolts ASTM A325N Anchor Bolts ASTM A307 or ASTM A36 Expansion Bolts KWICK-Bolts, WEJ-IT Bolts, or

Red-Head Anchors Headed Shear Connector Studs ASTM A108 Epoxy Anchors Hilti HIT HY150

Cast-in-Place Concrete Pan and Joist System

The majority of the building is designed using a cast-in-place concrete pan and joist system. Due to the need of a large floor-to-floor height and the possibility of exposed structure, the concrete system was the best choice for the main structural system. The code used for reinforced concrete design and construction was ACI 318-89. Foundation

The foundation system consists of a combination of stepped, continuous and spread footings. The basement foundation, which occurs only in Area C, resembles the on-grade foundation only differing with the height of its load-bearing walls. Footings have been designed for a maximum soil bearing pressure of 5000 PSF. Continuous footings typically have thicknesses between 2’-0” and 2’-6” and foundation walls are typically 1’-4” thick and centered on the footings.

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Columns Concrete columns carry most of the building load, with only a few scattered steel pieces to support the flat roof and canopies. They are supported by spread footings and are evenly distributed throughout the floors. Column sizes range from 16 to 24 inch squares.

Framing

The pan and joist system typically consists of a 20” pan depth and a 5” slab for a total depth of 25”. Joists have a common width of 5”. This system is used consistently throughout the building and adjustments in pan width occur where necessary. A typical bay is generally around 32’-0” x 30’-0” in size and joists are called out, as well as the pan width for each individual bay.

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Open Web Steel Joist System With the majority of the building loads being taken by the concrete system, steel was used for specialized cases. These cases include elaborate canopies, a standard steel joist supported roof, and a long-spanning barrel roof, which is what makes this building so unique. The designs of these steel systems follow the latest AISC manual and specifications. Canopies

Along the exterior of the building steel tubes and channels make up several canopies that are supported by the arching roof trusses. These framing members are cantilevered off the concrete columns and secured by a tension rod that connects to a main roof support. The canopies are finished off with a steel roof deck.

Steel Joist Roof

The roof frame consists of w-shape girders and evenly spaced Smartbeams. The original design called out for standard open web steel joists; however, Smartbeams were used to provide the same architectural features for a fraction of the price. The webs of standard w-shape beams were cut in a zigzag fashion and then offset and welded back together, providing even greater strength due to the increase in web depth.

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Barrel Vault Roof This is a complex system that integrates steel columns and joists to create an impressing arching roof. The main spanning members are steel purlins that reach over 100 feet. They extend from one exterior steel column to a concrete pier on the other side of the building. The purlins are attached to steel tubes that are supported by perpendicular spanning trusses. Steel wire is used for additional stability for the long spanning members.

Lateral System

As mentioned before, the main supporting system of this building is a cast-in-place concrete frame. This being so, nearly all columns and intersecting beams take part in the lateral system and the simply laid out concrete frames carry the loads. However, when analyzing the barrel vault roof, the lateral system becomes a bit more complicated. Along gridline E the steel roof members transfer the lateral loads directly to the concrete beams using a bent plate which is embedded in the beams using expansion bolts. At the other end of the vault roof, along gridline H, the steel joists transfer their lateral load into a steel tube column, again using a bent plate, which then distributes the load to its supporting concrete beam.

The concrete frames cantilever up to the steel roof joists eliminating any need for moment frames or cross bracing within the steel members; therefore, all steel connections are kept simple and transfer only minimal lateral forces. Once the lateral loads are absorbed by the concrete framing system they are transferred to the CMU bearing walls and into the foundations.

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Calculations Floor Loads

The following is a summary of the floor loads acting on the structure. The building is divided into many areas each with a different purpose and therefore different loading conditions occur. The Wisconsin Administrative Code was referred to and used as a guideline for many of the live load calculations. Dead loads were calculated using material self-weight and standards used by Hammel, Green & Abrahamson, Inc. Detailed calculations, load combinations, and live load reductions have been analyzed and are available in Appendix A.

First Floor Laboratory

Live Load: 150 PSF (floor load) 50 PSF (mech below) Total 200 PSF Dead Load 140 PSF (30” pan & joist)

Typical Laboratory Floor

Live Load 125 PSF (floor load) 20 PSF (misc partition) 5 PSF (ceiling/misc/mech) Total 150 PSF Dead Load 105 PSF (53” pan & joist)

Typical Classroom Floor

Live Load 80 PSF (floor load) 20 PSF (misc partition) 5 PSF (ceiling/misc/mech) Total 105 PSF Dead Load 105 PSF (53” pan & joist)

Administration Floor

Live Loads 80 PSF (floor load) 20 PSF (misc partition) 5 PSF (ceiling/misc/mech) Total 105 PSF

150 PSF (library) 20 PSF (misc partition) 5 PSF (ceiling/misc/mech) Total 175 PSF 170 PSF (bookstore/vault) 20 PSF (misc partition) 5 PSF (ceiling/misc/mech) Total 195 PSF

125 PSF (main corridor) 20 PSF (misc partition) 5 PSF (ceiling/misc/mech) Total 150 PSF Dead Load 105 PSF (53” pan & joist)

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Bar Joist w/ Flat Roof Live Load 30 PSF with applicable drift Dead Load 4 PSF (bar joists) 6 PSF (4” rigid insulation) 3 PSF (metal roof deck) 12 PSF (roofing & ballast) 5 PSF (ceiling/misc/mech) Total 30 PSF

Curved Roof over Laboratories

Live Load 30 PSF with applicable drift Dead Load 8 PSF (beams & girders) 3 PSF (metal roof deck) 8 PSF (roofing & insulation) 6 PSF (ceiling/misc/mech) Total 25 PSF

Wall Loads

All wall loads are taken as industry or company standards and reflect the self-weight of the material and or systems.

Interior Partitions

20 PSF (min)

Exterior CMU w/ Brick Veneer 4” Brick 50 PSF 8” CMU 50 PSF Total 100 PSF

Curtainwall / Metal Panel System

20 PSF

Snow Loads Based on the Wisconsin Building Code snow loads were calculated and compared to company standards. Several areas of drift will occur along the building, mainly on canopies, roof projections and along the two story section of the building where it meets the four story section. The snow drift along the two different roof levels has been calculated in detail and summarized below.

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Wind Loads The wind loads on this building are taken from the engineer’s analysis and follow the Wisconsin Building Code as to how they are determined. The windward pressures are as follows:

20 PSF (up to 50 ft) 25 PSF (> 50 ft to 100 ft)

Shear calculations for windward and leeward sides of the building have been calculated from the known pressures and heights. Diagrams summarizing the pressures and shear forces acting on the building for each direction of wind appear below. Detailed calculations are available, please see Appendix B. For the East / West Direction:

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For the North / South Direction:

Seismic Loads

In the original design no seismic loads were accounted for. The analysis took place before any standards or codes were issued that dealt with seismic forces in areas where seismic activity is unlikely. To adhere to modern code, the seismic shear forces have been calculated per modern code and shown below. For calculations, please refer to Appendix C

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Spot Checks - (refer to Appendix D for more information) Concrete Joist

A concrete joist in the library section of the building was analyzed. Assumptions:

Joist - 2J187 53” Width f’c = 4 ksi fy = 60 ksi Span = 32’-0” Slab = 7 1/2” Pan Depth = 20” Pan Width = 11 1/4” Loads: Dead Load: 105 PSF Live Load: 175 PSF Required Moment = 229.5 k-ft

Results:

Required Area of Steel = 2.83 in2 Moment Capacity = 229.57 k-ft

Conclusions: The design calls for the use of 3 - #9 bars on top and 2 - #7 bars on the bottom giving a total area of steel, As = 4.20 in2. Using this area of steel the joist would have a capacity of 336 k-ft, which exceeds that found in the check. In the detail of the typical joists the engineer calls for an addition bar to be placed on top. If this additional bar was ignored the moment capacity would be 258 k-ft which is much more reasonable when looking at the spot check. The placement of this additional bar could be a standard practice for the engineers. Seeing how it is not required to pass code, it is an acceptable safety precaution. This matter will be further investigated.

Concrete Column

An exterior concrete column was analyzed. Assumptions:

Column - E-11 20” x 20” f’c = 4 ksi fy = 60 ksi Length = 16’-0” 4 - #9 verts Loads: Pmax = 353 k MxDL = 40 k-ft MyDL = 52 k-ft MxLL = 61 k-ft MyLL = 37 k-ft MxWind = 40.7 k-ft MyWind = 16.5 k-ft

Results:

Pmax = 630 k Mmax = 281 k-ft

Conclusions: The calculated capacity of this column greatly exceeds that for which was needed according to load calculations used by the engineer. This item is in further review for the loads on the column that were calculated seem too small. A better look at the affect of the lateral loads might be an answer to this problem.

Appendix Contents: A - 1: Design Dead Loads A - 2: Design Live Loads A - 3: Wind, Snow, Other Design Criteria A - 4: Snow Drift B - 1: E/W Windward Wind Pressures and Shears B - 2: N/S Windward Wind Pressures and Shears B - 3: Leeward Wind Pressures and Shears B - 4: Wind Calculation Spreadsheet B - 5: Seismic Design Criteria B - 6: Seismic Base Loads B - 7: Seismic Calculation Spreadsheet C - 1: Concrete Beam Spot Check C - 2: Concrete Beam Spot Check cont. C - 3: Concrete Column Spot Check C - 4: Column Load Spreadsheet

Wind Analysis

E / W Windward Shear Forces

Level Height Pressure Tributary Height Length Fx Overturning Moment(ft) (psf) (ft) (ft) (k) (ft - k)

Roof 64 25 7.500 186.333 34.9 22364 48 25/20 13.833 186.333 47.6 22853 32 20 14.333 186.333 53.4 17092 16 20 16.000 186.333 59.6 9541 0 20 8.000 186.333 29.8 0

Sum 225.4 7184

E / W Leeward Shear Forces

Level Height Pressure Tributary Height Length Fx Total Fx Overturning Moment(ft) (psf) (ft) (ft) (k) (k) (ft - k)

Roof 64 10 7.500 186.333 14.0 48.9 8944 48 10 13.833 186.333 25.8 73.4 12383 32 10 14.333 186.333 26.7 80.1 8552 16 10 16.000 186.333 29.8 89.4 4771 0 10 8.000 186.333 14.9 44.7 0

Sum 111.2 336.6 3464

N / S Windward Shear Forces

Level Height Pressure Tributary Height Length Fx Overturning Moment(ft) (psf) (ft) (ft) (k) (ft - k)

Roof 64 25 7.500 318.000 59.6 38164 48 25/20 13.833 318.000 91.3 43823 32 20 14.333 542.000 127.0 40642 16 20 16.000 542.000 173.4 27751 0 20 8.000 542.000 86.7 0

Sum 538.1 15037

N / S Leeward Shear Forces

Level Height Pressure Tributary Height Length Fx Total Fx Overturning Moment(ft) (psf) (ft) (ft) (k) (k) (ft - k)

Roof 64 10 7.500 318.000 23.9 83.5 15264 48 10 13.833 542.000 44.0 135.3 21123 32 10 14.333 542.000 63.5 190.5 20322 16 10 16.000 542.000 86.7 260.2 13881 0 10 8.000 542.000 43.4 130.1 0

Sum 261.4 799.5 7058

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Seismic Analysis

Seismic Shear Forces

Level wx hx (wx)(hx)^1.088 Cvx Fx Overturning Moment(k) (ft) (k) (ft - k)

Roof 3111 64 287094 0.148304 252 161204 10699 48 721994 0.372961 633 304053 12877 32 559008 0.288767 490 156942 18008 16 367746 0.189967 323 5162

Sum 1935842 1 1698 67382

B - 7

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