Experimental study on the progressive collapse mechanism in the braced and tied-back retaining systems of deep excavations

Collapses of braced or tied-back excavations have frequently occurred. However, the influence of the failure of some retaining structure members on the overall safety performance of a retaining system has not been studied. Model tests of failures of retaining piles, struts or anchors were conducted in this study, and the load transfer mechanisms underlying these conditions were analysed. When failures or large deformations occurred in certain piles, the increasing ratios of the bending moments in adjacent piles were much larger in the braced retaining system than in the cantilever system and more easily triggered progressive failure. When the strut elevation was lower or the excavation depth was greater, the degree of influence and range of pile failures became larger. When certain struts/anchors failed, their loads transferred to a few adjacent struts/anchors, possibly leading to further strut/anchor failure. The influence mechanisms of strut or anchor failure on piles were different from those of pile failure. As the number of failed struts or anchors increases, the bending moments of the piles in the failure zone first decrease and then increase to very high values. Therefore, the progressive failure path extends from struts/anchors to piles and will lead to large-scale collapse.

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Experimental study of the progressive collapse mechanism of excavations retained by cantilever piles

Canadian Geotechnical Journal ◽

10.1139/cgj-2016-0284 ◽

2017 ◽

Vol 54 (4) ◽

pp. 574-587 ◽

Cited By ~ 7

Author(s):

X.S. Cheng ◽

G. Zheng ◽

Y. Diao ◽

T.M. Huang ◽

C.H. Deng ◽

...

Keyword(s):

Load Transfer ◽

Progressive Collapse ◽

Maximum Load ◽

Influential Factors ◽

Collapse Mechanism ◽

Sudden Increase ◽

Bending Moments ◽

Transfer Coefficients ◽

Collapse Mechanisms ◽

Peak Increase

An increasing number of catastrophic progressive collapses of deep excavations have occurred throughout the world. However, the research on progressive collapse mechanisms is limited. In this paper, two categories of model tests were conducted to investigate the mechanism of partial collapse (sudden failures of certain retaining piles) and progressive collapse. The model test results show that partial collapse can cause a sudden increase in the bending moments of adjacent piles via an arching effect. The load-transfer coefficients are defined to be equal to the peak increase ratios of the maximum bending moments in adjacent piles (peak moments caused by collapse over the values before the collapse). When the maximum load-transfer coefficient is larger than the bearing capacity safety factor of the piles, the partial failure will lead to progressive collapse. The influential factors of the progressive collapse mechanism, such as the partial collapse extent, excavation depth, and capping beam, were also investigated. During progressive collapse, the previous failed pile could cause new stress arching; simultaneously, the soil behind certain nearest intact piles could become loosened and destroy the arch springing of the stress arching, causing the progressive collapse to cease gradually.

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Shell-crossing in a ΛCDM Universe

Monthly Notices of the Royal Astronomical Society Letters ◽

10.1093/mnrasl/slaa198 ◽

2020 ◽

Vol 501 (1) ◽

pp. L71-L75

Author(s):

Cornelius Rampf ◽

Oliver Hahn

Keyword(s):

Dark Matter ◽

Perturbation Theory ◽

Large Scale ◽

Cold Dark Matter ◽

Three Dimensional ◽

Random Initial Data ◽

Recursion Relations ◽

Indispensable Tool ◽

First Time ◽

Very High

ABSTRACT Perturbation theory is an indispensable tool for studying the cosmic large-scale structure, and establishing its limits is therefore of utmost importance. One crucial limitation of perturbation theory is shell-crossing, which is the instance when cold-dark-matter trajectories intersect for the first time. We investigate Lagrangian perturbation theory (LPT) at very high orders in the vicinity of the first shell-crossing for random initial data in a realistic three-dimensional Universe. For this, we have numerically implemented the all-order recursion relations for the matter trajectories, from which the convergence of the LPT series at shell-crossing is established. Convergence studies performed at large orders reveal the nature of the convergence-limiting singularities. These singularities are not the well-known density singularities at shell-crossing but occur at later times when LPT already ceased to provide physically meaningful results.

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Assessing Annual Actual Evapotranspiration Based on Climate, Topography and Soil in Natural and Agricultural Ecosystems

Climate ◽

10.3390/cli9020020 ◽

2021 ◽

Vol 9 (2) ◽

pp. 20

Author(s):

Kleoniki Demertzi ◽

Vassilios Pisinaras ◽

Emanuel Lekakis ◽

Evangelos Tziritis ◽

Konstantinos Babakos ◽

...

Keyword(s):

Water Balance ◽

Large Scale ◽

Hydrological Model ◽

Actual Evapotranspiration ◽

Irrigated Agriculture ◽

Climate Data ◽

Natural Ecosystems ◽

Loading Effects ◽

Very High ◽

Of Greece

Simple formulas for estimating annual actual evapotranspiration (AET) based on annual climate data are widely used in large scale applications. Such formulas do not have distinct compartments related to topography, soil and irrigation, and for this reason may be limited in basins with high slopes, where runoff is the dominant water balance component, and in basins where irrigated agriculture is dominant. Thus, a simplistic method for assessing AET in both natural ecosystems and agricultural systems considering the aforementioned elements is proposed in this study. The method solves AET through water balance based on a set of formulas that estimate runoff and percolation. These formulas are calibrated by the results of the deterministic hydrological model GLEAMS (Groundwater Loading Effects of Agricultural Management Systems) for a reference surface. The proposed methodology is applied to the country of Greece and compared with the widely used climate-based methods of Oldekop, Coutagne and Turk. The results show that the proposed methodology agrees very well with the method of Turk for the lowland regions but presents significant differences in places where runoff is expected to be very high (sloppy areas and areas of high rainfall, especially during December–February), suggesting that the proposed method performs better due to its runoff compartment. The method can also be applied in a single application considering irrigation only for the irrigated lands to more accurately estimate AET in basins with a high percentage of irrigated agriculture.

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Development of Efficient and Selective Processes for the Synthesis of Commercially Important Chlorinated Phenols

Organics ◽

10.3390/org2030012 ◽

2021 ◽

Vol 2 (3) ◽

pp. 142-160

Author(s):

Keith Smith ◽

Gamal A. El-Hiti

Keyword(s):

Lewis Acid ◽

Large Scale ◽

Commercial Application ◽

Chlorinated Phenols ◽

Sulphur Compounds ◽

Inorganic Solids ◽

Solvent Free Conditions ◽

Commercially Important ◽

Ortho Cresol ◽

Very High

para-Selective processes for the chlorination of phenols using sulphuryl chloride in the presence of various sulphur-containing catalysts have been successfully developed. Several chlorinated phenols, especially those derived by para-chlorination of phenol, ortho-cresol, meta-cresol, and meta-xylenol, are of significant commercial importance, but chlorination reactions of such phenols are not always as regioselective as would be desirable. We, therefore, undertook the challenge of developing suitable catalysts that might promote greater regioselectivity under conditions that might still be applicable for the commercial manufacture of products on a large scale. In this review, we chart our progress in this endeavour from early studies involving inorganic solids as potential catalysts, through the use of simple dialkyl sulphides, which were effective but unsuitable for commercial application, and through a variety of other types of sulphur compounds, to the eventual identification of particular poly(alkylene sulphide)s as very useful catalysts. When used in conjunction with a Lewis acid such as aluminium or ferric chloride as an activator, and with sulphuryl chloride as the reagent, quantitative yields of chlorophenols can be obtained with very high regioselectivity in the presence of tiny amounts of the polymeric sulphides, usually in solvent-free conditions (unless the phenol starting material is solid at temperatures even above about 50 °C). Notably, poly(alkylene sulphide)s containing longer spacer groups are particularly para-selective in the chlorination of m-cresol and m-xylenol, while, ones with shorter spacers are particularly para-selective in the chlorination of phenol, 2-chlorophenol, and o-cresol. Such chlorination processes result in some of the highest para/ortho ratios reported for the chlorination of phenols.

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Effect of blast loading and resulting progressive failure of a cable-stayed bridge

SN Applied Sciences ◽

10.1007/s42452-021-04145-y ◽

2021 ◽

Vol 3 (3) ◽

Author(s):

Ravi Mudragada ◽

S. S. Mishra

Keyword(s):

Progressive Failure ◽

Blast Resistance ◽

Progressive Collapse ◽

Building Structures ◽

Structural Elements ◽

Blast Loads ◽

Cable Stayed Bridge ◽

Bridge Performance ◽

Cable Stayed Bridges

AbstractMany researchers have carried out experimental and numerical investigations to examine building structures’ response to explosive loads. Studies of bridges subjected to blast loads are limited. Hence, in this study, we present a case study on a cable-stayed bridge, namely, Charles River Cable-Stayed Bridge-Boston, to assess its robustness and resistance against the progressive collapse resulting from localized failure due to blast loads. Three different blast scenarios are considered to interpret the bridge performance to blast loads. To monitor the progressive failure mechanisms of the structural elements due to blast, pre-defined plastic hinges are assigned to the bridge deck. The results conclude that the bridge is too weak to sustain the blast loads near the tower location, and the progressive collapse is inevitable. Hence, to preserve this cable-stayed bridge from local and global failure, structural components should be more reinforced near the tower location. This case study helps the designer better understand the need for blast resistance design of cable-stayed bridges.

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Truck Appointment System for Cooperation between the Transport Companies and the Terminal Operator at Container Terminals

Applied Sciences ◽

10.3390/app11010168 ◽

2020 ◽

Vol 11 (1) ◽

pp. 168

Author(s):

Hyeonu Im ◽

Jiwon Yu ◽

Chulung Lee

Keyword(s):

Large Scale ◽

Container Terminal ◽

Container Terminals ◽

The Past ◽

Cooperation Model ◽

Appointment System ◽

New Form ◽

Truck Appointment System ◽

Import Container ◽

Very High

Despite the number of sailings canceled in the past few months, as demand has increased, the utilization of ships has become very high, resulting in sudden peaks of activity at the import container terminals. Ship-to-ship operations and yard activity at the container terminals are at their peak and starting to affect land operations on truck arrivals and departures. In response, a Truck Appointment System (TAS) has been developed to mitigate truck congestion that occurs between the gate and the yard of the container terminal. The vehicle booking system is developed and operated in-house at large-scale container terminals, but efficiency is low due to frequent truck schedule changes by the transport companies (forwarders). In this paper, we propose a new form of TAS in which the transport companies and the terminal operator cooperate. Numerical experiments show that the efficiency of the cooperation model is better by comparing the case where the transport company (forwarder) and the terminal operator make their own decision and the case where they cooperate. The cooperation model shows higher efficiency as there are more competing transport companies (forwarders) and more segmented tasks a truck can reserve.

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