Thesis Proposal. Executive Summary:

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1 Executive Summary: Thesis Proposal Contained in this report are the following items: Building background related to proposal topics Investigation topics with their proposed solutions Solutions methods and needed tasks A task completion schedule Oak Brook Pointe, approximately 250,000 square feet in total area, is an office building located in a suburb of Chicago,. Its 9 two-way concrete, L-shaped floor slabs, separated by 12-1 typically, are longitudinally divided into 30 wide bay strips, each with a 30 center span and two 35 side spans. The typical 26 diameter exterior circular columns and 24 x 24 square interior columns, both which extend to the ground with individual column footings, are poured monolithically with the slab to provide lateral stability. Six large mechanical, roof air-handling units support a main supply duct loop and one large return vent on each wing of each floor. The roof, with a slight aesthetic upslope towards the wing ends, is constructed with a typical flat roof membrane covered with rock ballast. Another feasible option for the superstructure is composite steel construction, which is lighter while being faster and easier to construct with much less site labor. Steel does have some disadvantages compared to reinforced concrete, most noteworthy being an increase in floor system depth. To help account for this plenum growth, vierendeel trusses allow mechanical ducts to pass through them, integrating the structural and mechanical systems. Beyond the structural design implications of this change, several construction management issues will need to be looked at, as well as any minor changes to the mechanical system that are required for effective coordination between the ductwork and vierendeel trusses. Including a green roof in the building s design provides several ecological, technical, and other benefits to the owner. Since the intent is to have this roof garden be a public use space, the landscaping and access requirements will need investigation, as will the structural, mechanical, and construction implications. Because of these effects on other building systems, research and design of the green roof system will be done first and will include an investigation of its environmental benefits and building system changes, which should be complete by mid February After determining the controlling structural loads the building must resist, most members will be sized using a RAMSteel model whereas the vierendeel trusses will be designed using RISA 3D. The lateral load resisting system will then be established and combined with the previously mentioned model to create a final design, which can then be used to determine its construction implications. This is scheduled to be completed by mid March 2003, allowing about four weeks to compile the results into a report and presentation

2 Relative Building Background: Oak Brook Pointe, located in a commercial-heavy area of a suburb of Chicago, Oak Brook, Illinois, is clad in award-wining, pre-cast panels and reflective glass and is generally L-shaped. It features a curved, all glass, center hinge and stepped wing ends creating single axis symmetry. The basement is below grade in front and at grade in back and contains 515 executive parking spots, a café, and small workout facility. Above, five rented floors of office space, approximately 45,000 square feet each, step out slight from the floor below with a small, two-story entry atrium at the hinge. This provides 250,000 square feet of total area and Figure 1: Typical Floor Plan 214,000 square feet of rentable office space. The structural system was originally designed as a 9 two-way concrete slab assisted by drop panels at columns and shallow beams at frame openings and areas of high load. 24 by 24 square interior columns and 26 diameter circular exterior columns poured continuously with the floor diaphragms resist lateral forces and transfer all loads to individual column footing foundations. Each wing comprised of 30-0 wide typical bay strips which are divided into 35-0 side spans and a 30-0 center span. 9-0 of its typical floor to floor height of 12-1 is used as the finished floor to finished ceiling height. Concrete shrinkage is accounted for by 5 10 pour strips on the first and second floor because no expansion joints are present. The mechanical system consists of four 130-ton roof air handling units, complete with exhaust fan, that support the first through forth floors, and two 70-ton similar units supporting the fifth floor. Each wing of a typical office floor has a 12 deep main supply duct loop that supports five individual fan-powered terminal units and main 144 x 18 return vent is located near the center hinge. A flat roof system with a rock ballast covered rubber membrane slopes up slight from the center hinge to the wing ends for aesthetic purposes. This slight slope does help water runoff reach two main storm drains at the base of the elevation difference. At the center hinge, this roof supports the six large mechanical units, which are surrounded by vertical screen wall

3 Topics & Proposed Solutions: 1) Structural System Alternative As is the case with any building project, it is important to investigate alternate structural systems to provide the owner with the most economical, practical and beneficial solution. After some very approximate calculations, it becomes apparent that the original design consisting of a two-way slab with drop panels is, in fact, the best reinforced concrete option. However, buildings can be built using alternative materials beyond reinforced concrete. Due to the building s height, spans, and loads, wood and light gauge steel construction can quickly be determined as inappropriate options, leaving a rolled steel shape system as the only viable alternative to reinforced concrete. A steel system is accompanied by a few main advantages including fast and easy construction with much less site work and lighter dead loads. Additionally, composite design uses the concrete floor slab to reduce beam sizes, which can result in a less expensive building. On the other hand, steel requires long lead and more preparation expected of the CM, a crane for construction (which may or may not be needed for placing the formwork of the two-way concrete system), and fireproofing, which can be expensive and time consuming to install. All of these advantages and disadvantages will be compared as part of the final thesis report. Another main disadvantage of a steel system is that much more of the plenum space will be taken up by the building s structure. In order to combat this, the proposed system will investigate the feasibility of using vierendeel trusses in place of beams where the structure and mechanical systems intersect. These trusses, which will work compositely with the concrete slab in final load conditions, will be fabricated of WT4x* top and bottom chords connected by welded LL3x2x* web members, and will include a rectangular panel sized to fit mechanical ductwork. Web nodes will be spaced approximately 54 apart. Figure 2: Truss Section Figure 3: Approximate Truss Model Figure 4: Typical Bay Strip Structural Plan A composite 2 Lok-Floor deck with 3 of lightweight concrete cover make up the floor slab which supplies the required one and a half hour fire rating required of the floor. This is supported by beams or trusses spaced 10-0 on center that span perpendicular to the wing s length. Girders spanning parallel to the wing s - 3 -

4 length transfer the load carried by the beams/trusses to the columns, which are laid out with the same column grid spacings as the two-way concrete system. As a general guideline, composite action is limited by a maximum of one shear stud per foot to keep construction costs and complications at a minimum. All loading will be determined using ASCE 7-98 with the inclusion of any owner specified load adjustments. Steel members will be designed using the code and design aides listed in the third edition of the American Institute of Steel Construction s Manual of Steel Construction Load and Resistance Factor Design. A preliminary approximation of the gravity system results in W21x62 (30) girders, W14x22 (30) center span beams, W16x26 (34) side span beams, and vierendeel trusses comprised of WT4x17.5 chords and LL3x2x¼ web members (also having 34 shear studs). Lateral loads will be carried by one of two options: 1) Concrete shear walls surrounding the stairwells and elevator core 2) Longitudinal moment frames along the exterior and transverse moment frames located where vierendeel trusses are not needed Possible Shear Walls Possible Moment Frames Figure 5: Locations of possible lateral load resisting elements Each lateral resisting system will be investigated as part of the final thesis. It is also important to note that in the second option, uplift forces may overcome the now lighter dead loads at the column s spread footing and, therefore, an alternate foundation system may be needed. Converting the building s design from a concrete superstructure to a composite steel system also affects other aspects of the building. There are a number of construction management issues that will need to be investigated including: 1) The construction schedule with longer lead times and truss fabrication time but less site work 2) Total building cost including a comparison between costs associated with truss fabrication versus an increase in plenum height associated with using just wideflange beams 3) Construction site layout noting steel layout/storage space and crane location(s) Additionally, the mechanical system may need slight adjustments in order to effectively integrate and coordinate the ductwork with efficient vierendeel trusses

5 2) Addition of a Green Roof System All buildings can and often do have a large environmental impact on their surrounding ecology. Although this is a very contemporary concern, designers as well as government bureaucrats are becoming more and more aware of this issue and are increasingly incorporating preventative measures in the building design process. Urban concentrations, especially large ones like Chicago, only amplify the negative impact on the natural surroundings, making Oak Brook Pointe a perfect candidate for such environmental aides. One solution to these problems, which is actually in the process of being made mandatory in the Chicagoland area, is the incorporation of a green roof. Extremely popular (and in some areas legally mandated) in Europe, a green roof is a system of filtering layers and growth layers, characterized by soils, grasses, shrubs, even trees, that substitutes for conventional flat roof water-proofing. Although such systems are often more costly and labor intensive Figure 5: Example of a green roof than conventional roofs, they provide several ecological as well as assorted other benefits to the building s owner including: 1) Cleansing of air toxins and reoxigenation of the air, particularly functional in this case since Oak Brook Pointe is locate directly next to an interstate tollbooth 2) Reduced Urban Heat Island effect, or heat reflected back into the atmosphere by standard roofing membranes that not only makes the entire city warmer but can magnify negative impacts of other pollutants 3) Reduced thermal and noise translation though the building s roof, making the building more energy efficient 4) Effective management and utilization of stormwater run-off 5) Creation of additional usable space and property value for the building tenants The specific advantages Oak Brook Pointe will benefit from with the addition of a green roof will be researched and quantified as part of the final thesis project. Beyond determining a landscaping plan for the roof and investigating additional public access requirements, adding a green roof to the building s design will influence its other building systems, the effects of which will be investigated the final thesis project including: 1) Additional structural roof loading and required framing 2) Additional structural column loads 3) Modified mechanical loads of the building, especially the fifth floor 4) Redesign of the roof s stormwater management system 5) Additional construction costs and complications - 5 -

6 Methods of Solutions: Because the addition of a green roof will have structural, mechanical, and construction implications of its own, altering the roof accordingly will be investigated first. After researching and choosing specific green roof products of major manufacturers, Hydrotech being the most used in Chicago, the roof landscape plan and access points will be designed attempting to minimize major changes to the existing building. This includes keeping stair tower locations the same and concentrating any heavy growth loads near column locations. An exact landscaping plan for the roof will be designed with the aide of a consulting landscape architecture student. Once designed, the green roof s structural and mechanical load properties will be determined from product information and calculation. After a consultation with a contractor with green roof experience, the systems material cost, labor, and schedule implications will be calculated and converted to owner costs for comparison to the original design. Task 1: Determine new architectural/landscaping plan for roof o Research green roof products and determine their relevant benefits o Determine public access points o Determine non-public versus public break areas of the roof o Work with landscape architect consultant to determine an aesthetic design Task 2: Determine structural implications o Research and/or calculate green roof system weights o Compare these loads to calculated roof dead and live loads to determine the required additional roof framing and column strength Task 3: Determine mechanical implications o Calculate thermal transfer through the green roof system o Compare the effects the green roof has on the mechanical system to those of the conventional flat roof system, include any solar gains/absorption Task 4: Determine construction implications o Research material cost, labor costs, installation processes o Determine the construction schedule adjustments o Compare the costs of a green roof versus the conventional system used in the original design, include labor, construction time, and any structural and mechanical system adjustments Final loads will be determined by combining ASCE 7-98 calculated loads with originally specified loads. These will then be applied to a RAMSteel model created using the same layout specified above to establish member sizes. After coming up with a logical integration geometry of the vierendeel trusses and the mechanical ducts, a RISA 3D model of each truss carrying loads from the RAMSteel model will be used to determine truss member sizes and connection requirements, which will then need to be designed. A design of each lateral force resisting system earlier specified will then be determined using the appropriate material codes and compared to the other to establish the most economical choice. Once this is determined the lateral system will be combined with the gravity system to create a final structural steel design. All effects on the construction - 6 -

7 management this change creates will then be investigated by creating a new construction cost estimate, schedule, and site layout. Task 1: Determine the loads on the building o Calculate all gravity loads using the superimposed dead loads and live loads specified in the original design o Calculate wind and seismic loading using ASCE 7-98 and determine which controls Task 2: Create a RAMSteel model of the building and get member sizes o Create building frame model of all floors in AutoCAD and import it into RAMSteel o Apply calculated loads to the model o Run design to establish approximate member sizes and column loads o Design columns o Spot check various members Task 3: Design the vierendeel trusses and their integration with the mechanical system o Determine truss geometry including size and location of the vierendeel panel o Create model of the truss in RISA 3D o Acquire loads from RAMSteel model, organize them into appropriate load cases including final ultimate load, unbalanced final ultimate load, final service load (for deflection check), non-composite ultimate dead load, non-composite service dead load (for determining camber), construction load, and unbalanced construction load, and apply them to the RISA 3D model o Run load envelope checks to determine member adequacy, and maximum connection forces o Determine weld gusset plate size at each truss node based on the maximum connection forces o Repeat for any trusses with changes in geometry or loading o Investigate if structural design affects mechanical system and make appropriate changes Task 4: Determine the lateral load resistance system o Determine lateral load distribution for a shear wall system including torsional effects o Establish shear wall sizes and reinforcement by ACI o Determine lateral load distribution for moment frames including torsional effects o Create STAAD models of the moment frames and apply gravity and distributed lateral loads to determine member sizes and connection requirements o Design moment connections o Compare advantages and disadvantages of each lateral system and determine which system has more economical benefit to the building project - 7 -

8 Task 5: Put all results together in a final design o Combine new lateral elements with RAMSteel model and investigate differences o Redesign all members of question o Summarize results Task 6: Determine the construction implications o Contact truss fabricator and receive approximate fabrication costs and times o Create a modified building cost estimate o Create a modified construction schedule o Create a new construction site layout In order to have a finish product including a written report and oral presentation, there are a few project management tasks that need to be completed as well. After completing the necessary designs of the green roof and steel superstructure and their effects on various other aspects of the building project, all research and calculation results will be compiled into supplementary information binder, and a summary of their findings will be included in a final written report. This report will be further summarized into an oral presentation that will be accompanied by a computerized slide show to help with the visualization of its topics. Task 1: Complete the roof redesign and determine its effects on other building systems o Compare new green roof system to the original ballasted membrane design o Determine which has greater benefit to the owner Task 2: Complete the structure redesign and determine its effects on the mechanical system and the building s construction o Compare new vierendeel truss system to a conventional beam design o Determine which has greater benefit to the owner o Compare new composite steel system to the original reinforced concrete design o Determine which has greater benefit to the owner Task 3: Organize all research and calculations into a supplementary reference binder Task 4: Compile relevant findings into the final thesis report booklet o Find, organize, and include appropriate graphical figures o Proofread document Task 5: Summarize report into an oral presentation o Create an visually interesting Microsoft Power Point slide show to help illustrate major points o Practice presenting and prepare for faculty questions - 8 -

9 Completion Schedule: For the project s completion: ACTIVITY Complete the roof redesign and determine its effects on other building systems Complete the structure redesign and determine its effects on the mechanical system and the building s construction Organize all research and calculations into a supplementary reference binder Compile relevant findings into the final thesis report booklet Summarize report into an oral presentation SCHEDULED COMPLETION DATE 14-Feb Mar Mar-03 4-Apr Apr-03 For the addition of a green roof into the final design: ACTIVITY Determine new architectural/landscaping plan for roof Research green roof products and determine their relevant benefits Determine public access points Determine non-public versus public break areas of the roof Work with landscape architect consultant to determine an aesthetic design Determine structural implications of the green roof Research and/or calculate green roof system weights Compare these loads to calculated roof dead and live loads to determine the required additional roof framing and column strength Determine mechanical implications Calculate thermal transfer through the green roof system Compare the effects the green roof has on the mechanical system to those of the conventional flat roof system, include any solar gains/absorption Determine construction implications Research material cost, labor costs, installation processes Determine the construction schedule adjustments Compare the costs of a green roof versus the conventional system used in the original design, include labor, construction time, and any structural and mechanical system adjustments SCHEDULED COMPLETION DATE 24-Jan Jan Jan Jan-03 7-Feb-03 7-Feb-03 7-Feb-03 7-Feb Feb Feb Feb

10 For altering the superstructure to composite steel design with vierendeel trusses: ACTIVITY SCHEDULED COMPLETION DATE Determine the loads on the building Calculate all gravity loads using the superimposed dead loads and live loads specified in the original design Calculate wind and seismic loading using ASCE 7-98 and determine which controls Create a RAMSteel model of the building and get member sizes Create building frame model of all floors in AutoCAD and import it into RAMSteel Apply calculated loads to the model Run design to establish approximate member sizes and column loads Design columns Spot check various members Design the vierendeel trusses and their integration with the mechanical system Determine truss geometry including size and location of the vierendeel panel Create model of the truss in RISA 3D Acquire loads from RAMSteel model, organize them into appropriate load cases and apply them to the RISA 3D model Run load envelope checks to determine member adequacy, and maximum connection forces Determine weld gusset plate size at each truss node based on the maximum connection forces Repeat for any trusses with changes in geometry or loading Investigate if structural design affects mechanical system and make appropriate changes Determine the lateral load resistance system Determine lateral load distribution for a shear wall system including torsional effects Establish shear wall sizes and reinforcement by ACI Determine lateral load distribution for moment frames including torsional effects Create STAAD models of the moment frames and apply gravity and distributed lateral loads to determine member sizes and connection requirements Design moment connections Compare advantages and disadvantages of each lateral system and determine which system has more economical benefit to the building project Put all results together in a final design Combine new lateral elements with RAMSteel model and investigate differences Redesign all members of question Summarize results Determine construction implications Contact truss fabricator and receive approximate fabrication costs and times Create a modified building cost estimate Create a modified construction schedule Create a new construction site layout 14-Mar Mar Mar Mar

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