A Practical Compensation Method for Differential Column Shortenings in High-rise Reinforced Concrete Buildings

High-rise reinforced concrete buildings have technical, economic and environmental advantages for high density development and they have become a distinctive feature for densely populated urban areas around the world. For this purpose, structural design of high-rise reinforced concrete buildings have become forward and particularly serviceability requirements gained more interest. Differential shortening of vertical members is one of the serviceability requirements; however, only a limited number of studies exist. In this study, a practical compensation method was proposed for the differential shortening of columns and shear walls in high-rise reinforced concrete buildings. In the proposed compensation method, vertical members were grouped and the total error was aimed to be minimized by penalizing the higher shortening differences in the groups to simplify the process of building construction. In order to validate the proposed method, a 32-storey high-rise building that was built in Izmir Turkey was investigated considering both the construction sequence and time-dependent effects as shrinkage and creep. Vertical shortening of columns and shear walls in the tower part of the building were calculated. Uniform-grouped compensation method and the proposed penalized errors compensation method with using L1-norm and L2-norm were applied for differential shortenings of columns and shear walls with considering different numbers of member groups. The magnitude of errors for each compensation method was presented and evaluated. Results of the numerical study reveal that the proposed penalized errors compensation method was capable of determining the compensation errors by minimizing the maximum errors efficiently

Monitoring the axial displacement of a high-rise building under construction using embedded distributed fibre optic sensors

The floor-to-floor axial shortening of vertical load-bearing elements is an important factor in the design and construction of high-rise buildings. Contractors need to allow for the expected final compression of columns and walls due to superimposed load, concrete creep and shrinkage, particularly when installing finishes and partitions in lower floors, while the building has not yet been completed. An added complication arises from the differential shortening between elements of different stiffness. This axial shortening is predicted by designers using empirical models, in advance of construction. However, in practice, the shortening at every level cannot be measured continuously using traditional surveying measurement techniques during construction. Therefore, a monitoring system using distributed fibre optic sensors (DFOS) measuring strain and temperature, is being installed during the construction of Principal Tower, a 50-storey reinforced concrete building in London. DFOS sensors are being embedded inside two columns and two walls as the construction progresses. Using the strain and temperature data acquired from this system, the axial deformation relative to the ground level can be calculated along the whole height of the completed elements, at any time during the construction. Thus, the engineers and contractors are able to verify their predictions and adjust their assumptions if necessary. A selection of the data acquired during the construction of the first 17 levels of the building is presented. These data have shown that the amount of shortening experienced by a member is influenced by the member’s stiffness and size. The monitoring data have also revealed that thermal movement has a significant effect on the overall axial displacement of the building

Distributed fibre optic sensor system to measure the progressive axial shortening of a high-rise building during construction

A novel approach is being used to measure the progressive axial shortening of key structural elements of Principal Tower, a 50-storey reinforced concrete building in London, as it is being built. Distributed fibre optic sensor (DFOS) cables are embedded inside two columns and two core walls, from which the axial strain profile can be measured along the whole height of the constructed elements. Measurements are being taken regularly throughout the construction process, making it possible to observe the change in strain, and thus the axial shortening, within these elements, at any stage of the construction. This helps the design engineers and contractor verify the predicted differential shortening and adjust the column height presets if necessary. The purpose of this paper is to describe the monitoring system and to present initial data recorded from the first five levels of the building.This research has been made possible through funding under EPSRC grant EP/N021614/1 and Innovate UK grant 920035, as well as funding by WSP, Multiplex Construction and Careys

Advancements in geospatial monitoring of structures

The need for advancements in geospatial monitoring of structures has evolved naturally as structures have become larger, more complex, and technology has continued to rapidly develop. Greater building heights generally lead to greater challenges for surveyors, limiting the practical use of traditional measurement methods. For this reason, a new complimentary method was developed and implemented to support elevation monitoring activities during construction of the Salesforce Tower in San Francisco, California. While some studies have explored the use of strain gauges to monitor strain development within individual members, the primary contribution of this work is that it presents a practical and proven to be implementable approach to estimating elevation changes throughout a multi-story reinforced concrete core wall tower during construction while utilizing strain measurements acquired at intermittent levels. Construction in urban landscapes has the potential to impact existing infrastructure. Identifying and mitigating any associated construction impacts is critical to public safety and construction progress. The development of Automated Motorized Total Stations (AMTS) has provided an effective means to monitor deformations in structures adjacent to construction activity. AMTS provides real time results so that movements may be immediately identified and addressed. However, the design, implementation, management, and analysis of these systems has frequently been problematic. Inadequate monitoring specifications have led to systems that fail to perform as intended even when project requirements were satisfied. A collection of monitoring specifications and AMTS projects have been reviewed to identify why certain problems have occurred and recommendations have been made to increase the probability of success on monitoring projects. A deformation monitoring approach that defines location specific threshold values based on a statistical analysis of baseline measurements is also presented in this dissertation. Identifying potential causes for monitoring specifications to fail to perform as intended and a deformation monitoring approach that defines location specific threshold values are secondary contributions of this dissertation

Deflection of concrete slabs: current performance & design deflection limits

Deflection is usually controlled by limiting the span/depth ratio. One aspect of this research is to document the deflection of a concrete slab in a large residential block. The other part of the research is to look at current design limits. Limits on deformation were set many decades ago, when the forms of construction, partitions, finishing, cladding and service were very different from what they are now. Part of that is to review the span-to-depth method of design. Site investigation and testing theory through observation and data collection was the main deductive approach of this research. A quantitative method was used to calculate and determine the deflection on concrete slabs, the research is attempted to identify target companies and projects to participate in the research. The data indicate that the slab has not sagged significantly due to the back propping for 30 days. However, it does seem that the slab was sloping down from the corner by 6 mm diagonally across the 12m bay. A margin of deflection around 2mm occurred especially in the mid-span of the slab 12 x 7 m corner bay. The 2 mm deflection occurred at the beginning of the investigation after back propping reinforced concrete corner bay slab. The back propping applied after 7 days of pouring sla

Experimental behavior, Analysis and Design of Energy Piles

The dissertation deals with the study of pile-soil interaction under coupled thermo-mechanical loadings focusing on the application of energy piles in a specific geographic area and particular subsoil conditions. In service condition energy piles are subjected to combined thermomechanical loads therefore, with respect to pile foundations the effect of the additional thermal loadings have to be considered. Different aspects about this topic are investigated through Finite Element analyses, small scale and in situ tests. A calculation procedure based on the mechanical calibration of soils parameters is presented. Back analyses of three case-histories from literature allowed the validation of the procedure. Then, the results of short term thermo-mechanical coupled analyses along with a sensitivity analysis provide insight about the effect of different parameters on the mechanical response. Dynamic energetic simulations carried out with dedicated software allowed estimating real thermal loadings to be applied to the pile. Additional investigations dealing with the time scaling of thermal variations, the influence of constraint at pile's head and toe and the thermal interaction with the upper structure along with long-term previsions are reported. To investigate about the cyclic behaviour observed in long term conditions two small scale models are designed (Model A and Model B). The experimental setup of the two laboratory models is described. The results of thermal and thermomechanical short-term tests carried on Model A and longer cyclic thermo-mechanical tests performed on Model B are presented. The physical modelling allowed investigating pile's response under thermal and mechanical controlled conditions and performing cyclic long-term tests. The interpretation of in situ investigations carried out on one bored energy pile equipped with spiral heat exchanger and vibrating wire gauges are also presented. Temperature of soil and thermal performance of the pile measured during in situ tests are reported. The results obtained, both through FEM modelling and laboratory and in situ tests, appear to be important for the optimal use of these systems, which are expected to be widely used in the future. The dissertation provides experimental data dealing with the application of energy piles in pyroclastic soils in the urban area of Napoli (IT) and thermal cycles calibrated on the basis of thermal demand of the upper structure

Lateral thermal buckling of pipelines on the sea bed

Subsea oil and gas exploration is increasingly moving into deeper water, where trenching of a pipeline for protection and to mitigate against upheaval buckling becomes increasingly impractical. In addition, the exploration of new reservoirs at higher temperatures and pressures than before leaves a submarine pipeline on the seabed more susceptible to lateral thermal buckling. A novel small-scale compressible base model, with an expanded polystyrene base compressed beneath a silicone rubber strip, has been developed to represent the constrained thermal loading of a pipeline lying on the seabed. This physical model is used, in addition to a nonlinear finite-element analysis, for a case study of a real buckled pipeline. Dimensional analysis is used to provide a means of comparing the post-buckled behaviour of the model strip with that of the fullsize pipeline. There is good agreement between the results of the post-buckled behaviour for the physical and finite-element models, and these results compare well with the survey data for the buckled real pipeline. General results from the physical model are also presented for strips with differing geometric and material properties, laid both straight and on a scaled lay-away curve. A useful measure of the evolution of a buckle, the free end displacement, is introduced. This is the axial displacement of the free end of a cut pipe, constrained to remain straight while undergoing thermal loading. This measure used in a study of the parameters which affect the far-post-buckling behaviour of a beam on a frictional foundation. The phenomenon of buckle lobe extinction, when a buckle lobe stops growing, is discovered for certain combinations of beam bending stiffness, axial friction coefficient and lateral friction coefficient. When the buckle length, buckle amplitude and free end displacement are formed into non-dimensional groups with these three parameters, curves for many parameter combinations are found to fall onto a single curve. The conditions for buckle lobe extinction, in terms of these dimensionless groups, may be determined directly from this universal curve. Finally, the closely-related problem of the stability of a pipeline being built up a slope is investigated. A case study is made of a real pipeline, incorporating numerical and physical models and also a simplified analytical modeL These models correlate well with each other, and enable the conditions for collapse of the real pipeline to be predicted

Enhancement of strain sensor sensitivity by combination of polarization maintaining fiber and single mode fiber in sagnac loop

Optical fiber-based sensing. techniques provide a unique set. of sensors which are small, easy to fabricate, lightweight, immune to electromagnetic interference (EMI), high sensitivity, large scale multiplexing, and in most cases inexpensive to manufacture. These advantages are the motivation behind continued researches and development in the field. The introduction, objectives, and the scope of work are presented in the first chapter. A review of the most popular of the optical and non-optical methods that is used to measure the strain is presented in chapter two. The methodology of work, analysis, and the results are presented in chapter three and chapter four, and the conclusion of this project in chapter five. This project investigates the fiber optic sensor. technologies that focus on the development. of fiber strain sensing element based on a combination of polarization maintaining fiber (PMF) and single mode fiber (SMF) in a Sagnac loop. Four cases are investigated in this work. The first, second, third and fourth cases involve 10 cm PMF, 20 cm PMF, 36 cm PMF + 4 cm SMF and 36 cm PMF + 14 cm SMF respectively as the strain element. Based on the experimental result, strain elements of 10 cm PMF, 20 cm PMF, 36 cm PMF + 4 cm SMF and 36 cm PMF + 14 cm SMF records sensitivities of 6.4 pm/μɛ, 14.7 pm/μɛ, 22.8 pm/μɛ and 25.3 pm/μɛ correspondingly for a range 0-1000 μɛ at 25 Cº temperature. It shows that the strain element of 36 cm PMF + 14 cm SMF possesses the highest sensitivity. In addition to the experimental results, simulation work is also done for comparison. The Sagnac loop model developed with Jones matrices agrees well with the experimental results

Topics of the nationwide phone-ins with Vladimir Putin and their role for public support and Russian economy

Acord transformatiu CRUE-CSICHere we consider several macroeconomic indicators taken from the Federal State Statistics Service (2019). First, there is the inflation rate calculated for each month as the sum of the inflation coefficients for the previous 12 months. Second, the unemployment rate is defined as the proportion of the unemployed in the economically active population. Further, the real wage index is calculated by dividing the nominal wage index by the consumer price index of the same period. Finally, budget expenditures are the funds of the federal and consolidated regional budgets directed to financial support of the tasks and functions of the federal and regional governments.Altres ajuts: This research has been supported by the Russian Science Foundation, project No. 19-18-00262 "Modelling a balanced technological and socio-economic development of the Russian regions".The addresses of national leaders can affect their public support and spur changes in the country's economy. To date, very few studies exist establishing these relationships, and no research has been done on the addresses from Vladimir Putin. In this paper we fill this knowledge gap by analysing the nationwide phone-ins of Putin, a special annual format where he addresses the public, and using structural topic modelling studying their topics over time. Furthermore, we relate these topics to public approval of the president and the government as well as to some Russian macroeconomic indicators such as inflation and budget expenditures. Based on our data containing 1938 responses and almost 250 thousand words, we identify 16 main topics covering areas from healthcare and education through economics to elections and legislation. We find that the topic of foreign affairs has gained in popularity over time the most (from around 4.5% at the beginning to more than 10% starting from 2014). Another topic, consistently gaining weight in the president's statements, is related to solving particular problems of the general public (from 8% to 12.5%) and is significantly correlated with subsequent decrease in the country's unemployment (Pearson's correlation coefficient -0.502). We also find that when the government's support is decreasing, Putin tends to discuss more socially significant topics (e.g., inflation, healthcare, Pearson's coef. around -0.5), while when the support is rising, he speaks more about foreign affairs (Pearson's coef. 0.773). Our study provides first evidence that Vladimir Putin may adapt the content of his phone-in meetings to gather public support and influence the country's economy