HW_2_Solutions - CE 227 Homework #2 Solutions Adpated from:...

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CE 227 Homework #2 Solutions Adpated from: Troy Morgan Problem 4 – Conceptual Design In this problem, we investigate various structural configurations for our building. I’ve presented a sketch of possible solutions here, but obviously yours may (and likely will) differ. What is important is to recognize how various structural systems/configurations are evaluated, since this process is done early in a project to narrow down the range of possible structural solutions. Option 1 – Concrete Core Shear Wall Conc. shear wall Conc. gravity framing Elevation Plan Advantages : Concrete is an inexpensive and effective building material, especially for wall construction. Concrete walls can be detailed with boundary elements and field steel for reliable, ductile cyclic response. Since concrete shear walls are generally quite stiff, the expected inelastic drifts should be very low. Disadvantages : Walls would probably be clustered around elevator cores, which are often located toward the center of the floor plate. This leads to torsional flexibility of the building, and large drifts from accidental mass eccentricity. Also, shear walls located just at the core would develop very large overturning moments in a relatively narrow element, leading to significant uplift forces, and hence expensive foundations. 1
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CE 227 Homework #2 Solutions Adpated from: Troy Morgan Option 2 – Steel Brace Frame Steel gravity framing Steel brace frame Elevation Plan Advantages : Steel braces combine strength and stiffness with versatility and ease of construction. Properly detailed, steel brace frames require very little field welding (which is very expensive compared to shop welding) and fast, efficient construction. In addition to being stiff, certain classes of steel brace frames provide significant ductility capacity and stable hysteresis. Such ductile brace frames include eccentrically braced frames (EBF’s) and buckling-restrained braced frames (BRBF’s.) These will be discussed further in class. Disadvantages : While some brace frames are ductile, others are not. Specifically, concentric brace frames are designed to buckle in compression and yield in tension. Even under the best detailing conditions, these frames to not dissipate significant energy per cycle of displacement, and are susceptible to low-cycle fatigue (that relates to several cycles of large plastic strain in the buckled region of the brace.) In addition to their questionable seismic performance, braces can be obstructive in terms of openings and windows. While considered by some as an aesthetic structural expression, most mainstream architects have been hesitant to embrace this rather utilitarian design paradigm. Also, gusset plates can shorten the effective length of the column, causing yielding.
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HW_2_Solutions - CE 227 Homework #2 Solutions Adpated from:...

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