Engineering as a Prerequisite for Growth: New York and its Infrastructure

<p>As a world city, New York is famous for many reasons; as a large city located primarily on islands at a complex of rivers, bays, and tidal straits, it has long depended on structural engineering for viability. Prominent structures include underwater vehicular and rail tunnels, bridges of every structural type, and aqueducts. Ten different buildings have held the world record for height, two arch bridges have held the world record for span, and four different suspension bridges have held the world record for their main span. With a multitude of successful businesses and the physical constraints of the geography, the motivation for technical innovation were present, and engineers were ready for the challenges.</p><p>These structures have generally not been built because they would break records, but rather because they served a purpose. For example, the Brooklyn Bridge, with a center span fiIy percent longer than the second- longest at the time of its construction, was built because ferries were the only transportation between New York and Brooklyn, then the first and third largest cities in the country. There is a close correlation, decade by decade and beginning in the 1880s, between what was feasible in terms of structural engineering and what has been built to enable the city to grow and prosper. This paper will examine that correlation and engineers’ role in the city’s evolution.</p>

Optimizing Skyscrapers' Spatial Integrated DSF-MTMD System Under Wind Loads

<p>From a structural engineering point of view, wind effects pose one of the major challenges to tall buildings. From a performance/architectural point of view, climatologic aspects pose a major challenge. Remedies for each challenge separately have been proposed. One of the remedies for wind effects is the Tunes-Mass-Damper (TMD) or multiple TMD's. To mitigate climatological issues, the Double-Skin-Façade (DSF) has been developed. Recently it has been suggested to take advantage of the space between the two skins of the DSF system to allocate TMD's.</p><p>In this work, another step is taken towards a single remedy for both challenges. A modified version of the TMD-DSF system proposed by Moon (2016) is presented. That is, parts of the mass of the DSF envelope itself are used as part of a multiple TMD (MTMD) system. This is obtained by connecting these parts to the building using springs and dampers while allowing the DSF to move parallel to the floor edges. Furthermore, the DSF-MTMD system is optimized using a formal optimization approach. The optimization indicates which parts of the envelope should be connected to the building rigidly and which should be used as TMD's. Furthermore, the properties of the springs and the dampers are determined by minimizing the cost associated with transforming the DSF system to a DSF-MTMD system and limiting wind responses to desired values.</p>

Seismic Resilience of Deteriorating RC Bridges and Road Networks under Climate Change

<p>This paper investigates the life-cycle seismic resilience of aging road networks with reinforced concrete (RC) bridges under the effects of climate change. The physical damage suffered by the exposed bridges is related to traffic limitations implemented over the network. A probabilistic framework is proposed to aggregate the time-variant seismic capacity assessment of RC structures exposed to chloride-induced corrosion with the traffic response of the transportation network. The life-cycle seismic resilience of a simple road network is evaluated based on the restoration of the network functionality guaranteed by the post-event recovery of the damaged bridge. The results highlight the detrimental effects of the progressive increase in the deterioration rate induced by climate change, impairing the seismic capacity of single bridges and, in turn, the seismic resilience of the overall transportation system.</p>

Structural safety and design under climate change

<p>The impact of climate change on climatic actions could significantly affect, in the mid-term future, the design of new structures as well as the reliability of existing ones designed in accordance to the provisions of present and past codes. Indeed, current climatic loads are defined under the assumption of stationary climate conditions but climate is not stationary and the current accelerated rate of changes imposes to consider its effects.</p><p>Increase of greenhouse gas emissions generally induces a global increase of the average temperature, but at local scale, the consequences of this phenomenon could be much more complex and even apparently not coherent with the global trend of main climatic parameters, like for example, temperature, rainfalls, snowfalls and wind velocity.</p><p>In the paper, a general methodology is presented, aiming to evaluate the impact of climate change on structural design, as the result of variations of characteristic values of the most relevant climatic actions over time. The proposed procedure is based on the analysis of an ensemble of climate projections provided according a medium and a high greenhouse gas emission scenario. Factor of change for extreme value distribution’s parameters and return values are thus estimated in subsequent time windows providing guidance for adaptation of the current definition of structural loads.</p><p>The methodology is illustrated together with the outcomes obtained for snow, wind and thermal actions in Italy. Finally, starting from the estimated changes in extreme value parameters, the influence on the long-term structural reliability can be investigated comparing the resulting time dependent reliability with the reference reliability levels adopted in modern Structural codes.</p>

Influence of changing environment conditions on the development of shrinkage strain and the expansion coefficient of large concrete specimens

<p>The standard creep and shrinkage strain measurements of concrete are usually conducted in a laboratory with constant temperature and humidity with a low variation. The creep and shrinkage measurements are conducted over a few months with the expectation that small concrete specimens can sufficiently describe the evolution of the rheology effects on a large multi-span bridge in the course of its operating life.</p><p>The monitoring of real bridge structures shows the actual progression of the deflections and concrete strains. Unfortunately the evaluation and interpretation of the measured values is complicated. The idea of the scientific Creep &amp; Shrinkage project was to combine the two described situations (laboratory experiments and monitoring of real bridge structures) creating an experimental setup which would benefit from the advantages of both approaches.</p><p>In order to achieve conformity of the measured test results with those of theoretical models (MC 2010, EC) it was necessary to upgrade the current models to include the effects of changing temperature and humidity. Within this paper the upgrade of the current standard models to include changing environment conditions will be elaborated, in addition to an explanation of the method used to separate shrinkage strains from the temperature strains from the measured data. The measured concrete expansion coefficients will also be discussed.</p>

Seismic Behavior of Curved Bridge in Mountain Area

<p>The 2016 Kumamoto Earthquake occurred in central Kyushu, Japan, on April 14th with Mw 6.2 followed by the Mw 7.0 mainshock on April 16th. These earthquakes were mainly caused by the Futagawa fault and Hinagu fault where surface ruptures extended about 34 km long. Some of the bridges located in mountain area and close to the fault were damaged due to these near‐field earthquakes. Oginosaka Bridge is one of them and is a horizontally curved bridge with longitudinal and transverse slope, which is a feature of the bridges located in mountain area. The superstructure was rotated on plan and displaced transversely at both abutments to the opposite side, and there was an evidence of the deck‐abutment pounding in longitudinal direction. In order to investigate the seismic behavior of the curved bridge, nonlinear time‐history analyses including a deck‐abutment pounding interaction were carried out. The deck‐abutment pounding interaction considered in the analyses could capture the post‐impact response of the superstructure. The near‐field ground motions were used for the analyses. The analytical results showed that the curved bridge is susceptible to the deck rotation caused by pounding in longitudinal direction at the deck end under earthquake loading.</p>

Experimental Study on Shear Behavior of Perfobond Connector with Boot Shaped Slots

<p>In order to solve the construction problem of perforating rebars’ precise location and it’s getting through the circular holes for the the conventional perfobond connector, a new type of perfobond connector with boot shaped slots was proposed. This new type perfobond connector has the advantage of convenient construction and pricise location. Three groups of push-out tests with nine specimens were carried out to study the shear capacity of the new type perfobond connector. The effect of the number and the spacing of boot shaped slots on failure modes, shear capacity, peak slip and shear stiffness were mainly studied. The test results show that the new type of perfobond connector with boot shaped slots has a high shear capacity and a good ductility, it could be widely applied on the connection between the steel and the concrete structures.</p>

Terra Cotta Flat Arches: A Historic Modern-Day Challenge

<p>At the turn of the 20th century, terra cotta flat arches (TCFA’s) were a popular floor system in steel framed buildings for industrial and office construction in the United States. These arches were lighter but just as fireproof as standard brick arches, and were designed empirically using proprietary allowable load tables, which were based mostly on load testing.</p><p>In the 21st century, the proprietary nature of the TCFA makes evaluating these systems problematic for the modern engineer, architect, and contractor. Renovations of buildings with TCFA floor assemblies typically will have new penetrations as well as altered loading conditions from its original construction.</p><p>It is important for all parties involved in the design and construction process of a renovation to understand the history, mechanisms, and limitations of TCFAs in order to have a successful renovation from both a design and a cost perspective. Conversely, renovating a building without the proper knowledge or experience with the existing materials can lead to change orders, time overruns, and most importantly life safety risks.</p><p>This paper is a summary of a presentation given by the same author to the Association for Preservation Technology (APT) conference in September, 2018. A more in-depth paper by the same author and colleagues Derek Trelstad and Rebecca Buntrock will appear as an article in the APT Bulletin in 2019.</p>

A practical approach for supporting decisions in bridge condition assessment and monitoring

<p>In this contribution a practical and rational decision-making approach is presented to be applied for common bridges typically managed by public authorities. The authors have developed a model with the intention to be applicable for practical cases for common bridges in the daily work of bride operators responsible for a large number of assets, yet still maintain the principles of more generic frameworks based on probabilistic decision-theory.</p><p>Three main attributes of the verification of sufficiency of structural performance are considered, namely: 1) the level of sophistication of modelling performance, 2) the degree of verification and acceptance criteria in terms of dealing with uncertainties and consequences, 3) the extent of information is obtained and incorporated in the verification.</p><p>The simplicity of the approach is demonstrated through an illustrative case study inspired by practical condition assessment decision problems. It is argued that in practical cases it may be desirable to utilize less advanced methods owing to constraints in resources or lack of reliable data (e.g. based on structural health monitoring or other on-site measurement techniques).</p>

The Third Bosporus Bridge — the Aerodynamic Stability of the Steel Segments During the Lifting

<p>The Third Bosporus Bridge is a suspendion bridge with a main span length of 1 408 m and a total length of 2 408 m located at the north of Istanbul near the Black Sea.</p><p>The main span is partially suspended at the pylons by stiffening cables and at the main cables with vertical hangers (Fig.1‐2). The deck is 58.8 m wide. But contrary to a classical arrangement, the transversal distance between the vertical hangers, in the suspended zone, is only 13.50 m. Due to this geometrical configuration of the vertical hangers, it was necessary to verify the risk of aeroelastic instabilities of steel segments of the deck during its lifting: risk of a torsional instability around the longitudinal axis but also around the vertical axis. Countermeasures have been proposed and adopted to suppress these risks.</p>