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Third Avenue, New York
Third Avenue is a north-south thoroughfare on the East Side of the New York City borough of Manhattan, running from Cooper Square north for over 120 blocks. The street leaves Manhattan and continues into The Bronx across the Harlem River over the Third Avenue Bridge north of East 129th Street to East Fordham Road at Fordham Center. It is one of the four streets that form The Hub, a site of both maximum traffic and architectural density, in the South Bronx.
Third Avenue is two-way from Cooper Square to 24th Street, but since July 17, 1960 (Spiegel, 1960). It has carried only northbound (uptown) traffic while in Manhattan; in the Bronx, it is again two-way. However, the Third Avenue Bridge carries vehicular traffic in the opposite direction, allowing only southbound vehicular traffic, rendering the avenue essentially non-continuous to motor vehicles between the boroughs.
The street was not always paved. In May 1861, according to a letter to the editor of The New York Times, the street was the scene of practice marching for the poorly equipped troops in the 7th New York Volunteer Infantry Regiment: "The men were not in uniform, but very poorly dressed, — in many cases with flip-flap shoes. The business-like air with which they marched rapidly through the deep mud of the Third-avenue was the more remarkable (New York Times, 1861)."
While single-glazed curtain walls were considered innovative at the time, these enclosures generally do not meet current wind code requirements and are at high risk of failure in a serious hurricane. Mid-century code required meeting wind loads of 20 lb/ft2 (and only for floors above 100 feet), whereas today façades in the region can experience loads above 70 lb/ft2. Curtain walls from this era were intended to be as thin as possible; they utilized non-load-bearing systems hung on the exterior of a building’s structural frame. Consequently, most of these buildings make poor candidates for straightforward façade retrofits, as their structures cannot bear the weight of a modern, double- or triple-glazed curtain wall or a double-wall system.
As these buildings have aged and architectural standards have changed, many cannot attract Class “A” tenancy. In particular, low ceiling heights seriously limit daylight and views in interior spaces. Also, a desirable density of workspaces is difficult to achieve with 20-foot column bay spacing. While control strategies can help increase vertical transportation, adding elevators is almost impossible. There are at least 107 office buildings from the 1958 to 1973 era in Midtown Manhattan alone, many of which have become Class “B” or “C” properties (Permasteelisa 2012).
Why have these outdated buildings not been replaced? The reason in many cases is that they are “overbuilt,” containing more floor area than current zoning code permits. Many were built with FARs of 15 or greater; current zoning allows only 15 FAR in C5-3 and 12 FAR in most commercial zones (generally located along major avenues in Midtown). Demolishing these buildings and replacing them with less rentable square footage would be difficult or impossible to finance.
Low ceiling heights seriously limit daylight and views in interior spaces. Also, a desirable density of workspaces is difficult to achieve with 20-foot column bay spacing. While control strategies can help increase vertical transportation, adding elevators is almost impossible. Both the retrofit and replacement designs were intended to exemplify current best practices and prototypical performance-focused solutions to improve these sites using modern building technologies. The significant expertise on hand in the design charrette established a level of confidence that the design solutions considered reflect current best practices. While no specific economic analyses are included in the report, many rough financial calculations helped shape the design decisions of these scenarios. Long-time practitioners in the New York real estate development market were consulted or included in the charrette to ensure the solutions reflected realistic incentives and market-viable options
Outside air is provided by the central air distribution system. Although the building’s curtain wall contains operable window sections, these are solely for the purpose of allowing window washing, and have become a constant source of air-balancing problems, as leaks around the aluminum awning increasingly occur and add to ventilation imbalance. Tenants occasionally open windows for more outside air when cooling is insufficient in a space. The building has a minimal amount of exterior insulation: one inch of rigid insulation in the form of mineral wool board, mounted inboard of the anodized aluminum spandrels. V-shaped column covers that run the height of the tower are somewhat insulated by honeycomb aluminum backing, which also serves to defeat “oil-canning” of the surfaces.
Through these measures, including retrofitting window films, caulking the façade, installing variable speed drives on mechanical systems and maintaining rigorous maintenance standards, this building consumes significantly less energy than many of its cohort. The team energy-modeled the building’s existing condition and occupancy, coming within 6% of the actual historic energy records of the building – a highly accurate figure. The model resulted in a site Energy Use Intensity (EUI) of 101 kBTU/ft2, a total site energy use of 28,221,013 kBTU, a source EUI of 209.7 kBTU/ft2, and a total source energy use of 58,538,084 kBTU. This weather-normalized result was almost identical to data reported by the City’s energy benchmarking initiative. This set of numbers was used as the baseline for comparing options for retrofit and replacement. For another point of comparison, the baseline model was modified to simulate the building’s performance at 100% occupancy (its actual occupancy rate is about 80%), at the use density that would be expected with Class “A” office tenants. As expected, the current occupancy pattern requires considerably less energy than it would if the building were 100% filled with Class “A” tenants. For purposes of this study, all comparisons were done against the current use case.
The tallest building in the world is currently the Taipei 101 measuring 509 m (1,670 ft). This office block houses fifty elevators of which thirty-four are double-deckers and two are the fastest elevators in the world. Total investment in elevator technology for this building totaled approximately US$85 million. The tower has two shuttle elevators for public access to the observation deck on the 89th floor. These elevators have been officially recognized by the Guinness Book of Records as the fastest elevators in the world. With full loads, the ascent speed reaches a maximum of 16.8 m/s (55 ft/sec) or nearly 60 km/h (37 mph). Descent speeds measure 10.0 m/s (33 ft/sec) or 37 km/h (23 mph). In comparison, the fastest elevators in the Netherlands travel at 6.0 m/s (19.5 ft/sec). These are located in the Delftse Poort (Rotterdam), the Rembrandttoren (Amsterdam), the Hoftoren (The Hague) and the WTC (Amsterdam).Elevator cars in these shuttles are fitted out as airtight pressure cabins and equipped with pressure regulation systems similar to those used in aircraft. This allows for a gradual change in pressure over the elevator’s height to alleviate the pain that can be caused to passengers’ ears. Pressurization on descent is also the reason why the elevators descend more slowly than they ascend. (Pressurization is more painful for the ears than the depressurization that occurs on ascent).
Elevator cars are fitted with upper and lower capsule-shaped spoilers to provide aerodynamic streamlining. These ensure that the air stream flows smoothly around the moving elevator car saving energy and reducing interior shaft airflow-induced noise levels. Vibration within the car has virtually been eliminated by implementing a tri-axial, active-control roller guidance system for suspending cars in their tracks. Active mass damping has also been fitted to each elevator to minimize lateral movement. Car movement experienced as two elevators pass one another in opposite directions at full speed has virtually been eliminated. Thanks to these measures, comfort levels can only be described as phenomenal, certainly given their exceptional speeds. The safety braking system, that operates in the event that the car exceeds nominal speeds by more than 10% for whatever reason (e.g. a broken cable or driveshaft, or traction failure), is fitted with brake pads made of a silicon nitrite ceramic compound that brings the car to a standstill swiftly and safely. The office block (floors 9 through 84) is accessed as though it were made up of three individual building segments each of 112 m (367 ft) stacked one on top of the other. Transportation to and from the sky lobbies on the 35th and 59th floors is provided by ten high-speed, double-deck elevators (weighing 4,080 kg (8,995 lb) and holding up to twenty-seven passengers per car) that shuttle their passengers non-stop to their transfer levels (Ngá»c, 2013).
The direction of the evolution of tall building structural systems, based on new structural concepts with newly adopted high-strength materials and construction methods, has been towards augmented efficiency. Consequently, tall building structural systems have become much lighter than earlier ones. This direction of the structural evolution toward lightness, however, often causes serious structural motion problems –primarily due to wind-induced motion. From the viewpoint of structural material’s properties, due to the lag in material stiffness compared with material strength, the serviceability of the structure potentially becomes a governing factor in tall building design when high strength material is used. For instance, today, structural steel is available from 170 to 690 MPa (24 to 100 ksi). However, its modulus of elasticity remains nearly the same without regard to the change in its strength. The change of production process or heat treatment influences its strength but not the modulus of elasticity. Regarding concrete, increase in its strength results in increase in its modulus of elasticity, albeit increasing its brittleness. However, this increase in the modulus of elasticity is relatively small compared with the increase in strength. Thus, the lighter structures produced by high-strength materials can cause motion problems. The control of this structural motion should be considered with regard to static loads as well as dynamic loads. Against the static effect of wind loads, stiffer structures produce less lateral displacement. With regard to the dynamic effect of wind loads, not only the windward response but also the across-wind response of the structure should be considered. Generally, in tall buildings, the lateral vibration in the across-wind direction induced by vortex shedding is more critical than that in the windward direction.
Regarding both directions, structures with more damping reduce the magnitude of vibration and dissipate the vibration more quickly. With regard to the vibration in the across-wind direction, a stiffer structure reduces the probability of lock-in condition because as a structure’s fundamental frequency increases, wind velocity that causes the lock-in condition also increases. Since the direction of structural evolution towards lightness is not likely to be reversed in the future, more stiffness and damping characteristics should be achieved with a minimum amount of material (Moon, 2005).
2014. Taipei 101 - Wikipedia, the free encyclopedia. [ONLINE] Available at: http://en.wikipedia.org/wiki/Taipei_101. [Accessed 05 May 2014].
"A Word in Season on an Important Subject", letter to the editor, New York Times, May 16, 1861. [Accessed 03 May 2014].
Copy of Advantages and Disadvantages of Skyscrapers by Äào Ngá»c on Prezi. [ONLINE] Available at: http://prezi.com/l2jyi1kfzq3u/copy-of-advantages-and-disadvantages-of-skyscrapers/. [Accessed 05 May 2014].
Moon, K. (2005).Dynamic Interrelationship between Technology and Architecture in Tall Buildings. Unpublished PhD Dissertation, Massachusetts Institute of Technology. [Accessed 02 April 2014].
Spiegel, Irving (July 18, 1960). "2 One-Way Shifts Go Smoothly". The New York Times. [Accessed 03 May 2014].