Infrastructure Sustainability

2011 ◽  
pp. 202-211
Author(s):  
Praveen Moragaspitiya ◽  
David Thambiratnam ◽  
Nimal Perera ◽  
Tommy Chan
Keyword(s):  
Numerical Procedure ◽  
Time Dependent ◽  
Test Procedures ◽  
High Rise ◽  
Secondary Systems ◽  
Content Variable ◽  
True Time ◽  
And Performance ◽  
Concrete Elements ◽  
Axial Shortening

High density development has been seen as a contribution to sustainable development. However, a number of engineering issues play a crucial role in the sustainable construction of high rise buildings. Non linear deformation of concrete has an adverse impact on high-rise buildings with complex geometries, due to differential axial shortening. These adverse effects are caused by time dependent behaviour resulting in volume change known as ‘shrinkage’, ‘creep’ and ‘elastic’ deformation. These three phenomena govern the behaviour and performance of all concrete elements, during and after construction. Reinforcement content, variable concrete modulus, volume to surface area ratio of the elements, environmental conditions, and construction quality and sequence influence on the performance of concrete elements and differential axial shortening will occur in all structural systems. Its detrimental effects escalate with increasing height and non vertical load paths resulting from geometric complexity. The magnitude of these effects has a significant impact on building envelopes, building services, secondary systems, and lifetime serviceability and performance. Analytical and test procedures available to quantify the magnitude of these effects are limited to a very few parameters and are not adequately rigorous to capture the complexity of true time dependent material response. With this in mind, a research project has been undertaken to develop an accurate numerical procedure to quantify the differential axial shortening of structural elements. The procedure has been successfully applied to quantify the differential axial shortening of a high rise building, and the important capabilities available in the procedure have been discussed. A new practical concept, based on the variation of vibration characteristic of structure during and after construction and used to quantify the axial shortening and assess the performance of structure, is presented.

Time-dependent deformations of concrete columns under different construction load histories

2019 ◽  
Vol 22 (8) ◽  
pp. 1845-1854 ◽  
Author(s):  
Dujian Zou ◽  
Chengcheng Du ◽  
Tiejun Liu ◽  
Jun Teng ◽  
Hanbin Cheng
Keyword(s):  
Prediction Models ◽  
Plain Concrete ◽  
Concrete Columns ◽  
In Situ Monitoring ◽  
Time Dependent ◽  
Construction Stage ◽  
Inappropriate Use ◽  
High Rise ◽  
Multi Stage ◽  
Axial Shortening

The adverse effects caused by differential axial shortening in high-rise buildings have received increasing attention with growing building height. However, the axial shortening analysis still lacks accuracy compared to the in-situ monitoring results of practical high-rise buildings during construction stage. It is imperative to identify the error sources, and the applicability of the current shortening prediction models should be test verified. In this study, 14 plain concrete columns were cast, and the multi-stage load method was applied to approximately simulate the loading history of axial concrete members during construction stage. The time-dependent deformations of loaded concrete specimens were measured, and a comparative analysis was conducted between test results and numerical prediction values. It is found that the measured deformations of multi-stage loading cases are all underestimated compared with predicted results, and this underestimation may be mainly caused by the inappropriate use of elastic modulus. It further indicates that the axial shortening analysis of high-rise buildings tends to underestimate the actual shortening value when the traditional calculation method is used. This study provides a reference for explaining the mismatch between the analytical results and the actual shortening values.

scholarly journals Thermal Performance Analysis of Heat Collection Wall in High-Rise Building Based on the Measurement of Near-Wall Microclimate

Energies ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 2023
Author(s):  
Ruixin Li ◽  
Yiwan Zhao ◽  
Gaochong Lv ◽  
Weilin Li ◽  
Jiayin Zhu ◽  
...  
Keyword(s):  
Wind Speed ◽  
Structural Design ◽  
Theoretical Basis ◽  
Thermal Process ◽  
Measured Data ◽  
Passive Heating ◽  
High Rise ◽  
And Performance ◽  
Wall Components ◽  
Near Wall

Near-wall microenvironment of a building refers to parameters such as wind speed, temperature, relative humidity, solar radiation near the building’s façade, etc. The distribution of these parameters on the building façade shows a certain variation based on changes in height. As a technology of passive heating and ventilation, the effectiveness of this application on heat collection wall is significantly affected by the near-wall microclimate, which is manifested by the differences, and rules of the thermal process of the components present at different elevations. To explore the feasibility and specificity of this application of heat collection wall in high-rise buildings, this study uses three typical high-rise buildings from Zhengzhou, China, as research buildings. Periodic measurements of the near-wall microclimate during winter and summer were carried out, and the changing rules of vertical and horizontal microclimate were discussed in detail. Later, by combining these measured data with numerical method, thermal process and performance of heat collection wall based on increasing altitude were quantitatively analyzed through numerical calculations, and the optimum scheme for heat collection wall components was summarized to provide a theoretical basis for the structural design of heat-collecting wall in high-rise buildings.

A multi-octave microwave 6-bit true time delay with low amplitude and delay variation in 65 nm CMOS

2021 ◽  
pp. 1-10
Author(s):  
Yakov Gutkin ◽  
Asher Madjar ◽  
Emanuel Cohen
Keyword(s):  
Time Delay ◽  
Insertion Loss ◽  
Impedance Matching ◽  
Least Significant Bit ◽  
Delay Cell ◽  
True Time Delay ◽  
Unit Cells ◽  
True Time ◽  
And Performance ◽  
Low Amplitude

Abstract In this paper, we describe the design, layout, and performance of a 6-bit TTD (true time delay) chip operating over the entire band of 2–18 GHz. The 1.15 mm2 chip is implemented using TSMC foundry 65 nm technology. The least significant bit is 1 ps. The design is based on the concept of all-pass network with some modifications intended to reduce the number of unit cells. Thus, the first three bits are implemented in a single delay cell. A peaking buffer amplifier between bit 4 and bit 5 is used for impedance matching and partial compensation of the insertion loss slope. The rms delay error of the TTD is <1 ps over most of the frequency band and insertion loss is between 2.5 and 6.3 dB for all 64 states.

The Seismic Hazard Implications of Declustering and Poisson Assumptions Inferred from a Fully Time-Dependent Model

2021 ◽  
Author(s):  
Edward H. Field ◽  
Kevin R. Milner ◽  
Nicolas Luco
Keyword(s):  
Seismic Hazard ◽  
Poisson Process ◽  
Seismic Hazard Assessment ◽  
Aftershock Sequence ◽  
Time Dependent ◽  
Probabilistic Seismic Hazard Assessment ◽  
Full Time ◽  
Quiet Time ◽  
Epidemic Type Aftershock Sequence ◽  
True Time

ABSTRACT We use the Third Uniform California Earthquake Rupture Forecast (UCERF3) epidemic-type aftershock sequence (ETAS) model (UCERF3-ETAS) to evaluate the effects of declustering and Poisson assumptions on seismic hazard estimates. Although declustering is necessary to infer the long-term spatial distribution of earthquake rates, the question is whether it is also necessary to honor the Poisson assumption in classic probabilistic seismic hazard assessment. We use 500,000 yr, M ≥ 2.5 synthetic catalogs to address this question, for which UCERF3-ETAS exhibits realistic spatiotemporal clustering effects (e.g., aftershocks). We find that Gardner and Knopoff (1974) declustering, used in the U.S. Geological Survey seismic hazard models, lowers 2% in 50 yr and risk-targeted ground-motion hazard metrics by about 4% on average (compared with the full time-dependent [TD] model), with the reduction being 5% at 40% in 50 yr ground motions. Keeping all earthquakes and treating them as a Poisson process increases these same hazard metrics by about 3%–12%, on average, due to the removal of relatively quiet time periods in the full TD model. In the interest of model simplification, bias minimization, and consideration of the probabilities of multiple exceedances, we agree with others (Marzocchi and Taroni, 2014) that we are better off keeping aftershocks and treating them as a Poisson process rather than removing them from hazard consideration via declustering. Honoring the true time dependence, however, will likely be important for other hazard and risk metrics, and this study further exemplifies how this can now be evaluated more extensively.

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