Prediction Models of Shrinkage and Creep for Concrete Columns

2011 ◽  
Vol 243-249 ◽  
pp. 1583-1588
Author(s):  
Yi Gang Lv ◽  
Jian Ren Zhang ◽  
Kang Xu
Keyword(s):  
Prediction Models ◽  
Plain Concrete ◽  
Least Square Method ◽  
Concrete Columns ◽  
Shrinkage Strain ◽  
Least Square ◽  
Creep Effect ◽  
Shrinkage And Creep ◽  
Term Performance

In constant temperature and humidity environment, the properties of shrinkage and creep for a group of plain concrete and reinforced concrete columns were observed in long-term and experimental method. The curves of concrete shrinkage and creep effect with time were obtained. Checking coefficient and type coefficient of shrinkage and creep effect were put forward in order to predict models of shrinkage and creep. Using the least square method, functions of checking coefficient and type coefficient were acquired and the prediction models of shrinkage strain and creep coefficient of concrete were obtained based on the modification of the formula of JTG D62-2004. The foundation is laid for the application of the long-term performance research in bridge structure.

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.

The Application of Cubic Spline Interpolation Function in Determining Rock Rheological Long-Term Strength

2014 ◽  
Vol 580-583 ◽  
pp. 205-208
Author(s):  
Mo Li Zhao ◽  
Qiang Yong Zhang
Keyword(s):  
Spline Interpolation ◽  
Least Square Method ◽  
Cubic Spline ◽  
Least Square ◽  
Maximum Deviation ◽  
Interpolation Function ◽  
Term Strength ◽  
Cubic Spline Interpolation ◽  
Dagangshan Hydropower Station

The rheological long-term strength is determined according to the triaxial rheological test data of diabase at the dam area of Dagangshan Hydropower Station. Firstly, based on the stress-strain isochronous curve method and connected the test points with cubic spline interpolation function, the maximum deviation point in the long-term interval is determined as the turning point and established the long-term strength by nonlinear least square method. The results show that this method is consistent with the other methods. Finally, the advantage and disadvantage of this method is analyzed. This method can overcome the randomness of artificial selecting the turning points. Therefore, maximum deviation point method is relatively a reasonable and effective method to determine the rheological long-term strength of rock.

Long-Term Performance of Jointed Plain Concrete Pavement with Rapid Strength Concrete On California Highways

2021 ◽  
Author(s):  
Michael Darter
Keyword(s):  
Fatigue Cracks ◽  
Plain Concrete ◽  
Concrete Pavement ◽  
Highway Projects ◽  
Strength Concrete ◽  
Heavy Truck ◽  
Overall Performance ◽  
Long Term Performance ◽  
Term Performance

Rapid Strength Concrete (RSC) slabs on six California jointed plain concrete pavement (JPCP) highway projects were surveyed. These projects had been previously surveyed in 2008 at 3-years of age and by 2018 had reached a service life of 13-years. Of the initial 5430 slabs examined in 2008, a total of 1493 RSC slabs, located on 12 traffic lanes, were observed and distress types recorded again in 2018. These slabs included both CTS and 4x4 RSC located in both inner and outer lanes. Only a small percentage (1.4%) of the 5,430 RSC slabs exhibited any distress in 2008 after 3-years' service and the increases were small over the next 10 years of service with the exception of transverse fatigue cracks. The transverse (top down fatigue) type of cracking had the highest percentage and largest increase of any distress type. The heavy truck outside lanes exhibited 21% transversely cracked RSC slabs and the inner passing lanes 3%. The outer truck lanes carried over 3 times more trucks than inner lanes. The RSC slabs were mostly 200-223 mm thick and thus susceptible to fatigue damage. The overall performance of the RSC slabs (both CTS and 4x4 RSC materials) were similar and considered to be outstanding over 13 years with a large majority expected to survive many more years.

Concrete Shrinkage and Creep Effect Prediction Model and the Influence Factors Analysis

2013 ◽  
Vol 756-759 ◽  
pp. 2051-2054 ◽  
Author(s):  
Rui Fang Duan ◽  
Xiu Fen Huang ◽  
He Zhang
Keyword(s):  
Relative Humidity ◽  
Influence Factors ◽  
Shrinkage Strain ◽  
Complex Problem ◽  
Concrete Creep ◽  
Concrete Shrinkage ◽  
Creep Coefficient ◽  
Creep Effect ◽  
Shrinkage And Creep ◽  
Average Relative Humidity

It is a complex problem that forecast and control the shrinkage and creep of concrete and influence on the performance of the structures.Through the conmparion of all kinds of common model,the article have also analysed the main influence factors about the concrete shrinkage and creep effect . The results showed that JTJ 85 model for shrinkage and creep effect tends to conservative calculation; the creep coefficient and shrinkage strain of JTG D62 model and the CEB-FIP model were basically consistent; and ACI 209 model underestimated the concrete shrinkage and creep effect. Theoretical depth of components was more sensitive to concrete shrinkage strain, and creep coefficient was smaller sensitivity; The effect of concrete creep increases with the decreasing of age at loading, when age of loading percentage increased from three to 28 days, the concrete creep effect of the terminal value reduced about 80%; The influence of environment average relative humidity on shrinkage and creep effect is more sensitive, when environment average relative humidity increased from 50% to 80%, creep coefficient nearly reduced about 30%,and shrinkage strain decreased 50%, in comparison, the influence of environment relative humidity chance on the concrete shrinkage effect is greater than that on creep effect.

Experimental Investigation on the Shrinkage and Creep Performance of Self-Compacting Lightweight Concrete

2013 ◽  
Vol 860-863 ◽  
pp. 1346-1353 ◽  
Author(s):  
Yun Guo Zhang ◽  
Zhi Min Wu ◽  
Xi Wu
Keyword(s):  
Lightweight Concrete ◽  
Autogenous Shrinkage ◽  
Experimental Investigations ◽  
Aggregate Concrete ◽  
Creep Coefficient ◽  
Shrinkage And Creep ◽  
The Difference ◽  
Term Creep ◽  
Term Performance

Several experimental investigations were conducted on the autogenous shrinkage and creep performances of two types of designed self-compacting lightweight concrete (SCLC). In order to explore the difference in long-term performance between SCLC and normal aggregate concrete, normal aggregate self-compacting concrete (SCC) and normal concrete (NC) are also designed in this study. The results indicate that the designed SCLC exhibits lower autogenous shrinkage at early age, even slight expansion during the first 10 days. After 6 months, the autogenous shrinkage of SCLC increases nearly equal to those of normal aggregate concrete. Compared with the reference concretes NC and SCC, the 360-day creep coefficient of SCLC is lower, but the specific creep is higher. It is also found that long-term creep coefficient and specific creep decrease with the increase of compressive strength of SCLC.

scholarly journals Laju Deoksigenasi Sungai Bedadung Hilir Akibat Pencemar Organik

2020 ◽  
Vol 21 (1) ◽  
pp. 109-117
Author(s):  
Agus Dharmawan ◽  
Sri Wahyuningsih ◽  
Elida Novita
Keyword(s):  
Water Quality ◽  
Organic Waste ◽  
Reduction Rate ◽  
Least Square Method ◽  
Quality Parameters ◽  
Organic Wastes ◽  
Least Square ◽  
Coefficient Of Determination ◽  
Stream Flows

ABSTRACTBedadung stream, located at Rambipuji, Balung, Wuluhan, and Puger, is downstream where dilution of organic wastes occurred and affects its water quality. Microorganisms decompose organic wastes and lead to depletion of dissolved oxygen in the water. The aim of this research was to analyze the deoxygenation rate of Bedadung downstream. The raw data was obtained by measuring stream flows and its water quality parameters (Temperature, DO and BOD) at 5 observed stations. The laboratory analysis consisted of BOD5 and long-term BOD2,4,6,8,10. Increasing the value of BOD for 10 days had a tendency of polynomial pattern order 3 with a coefficient of determination R 0.8987 – 0.9781. The 10 days BOD reactions were used to determine deoxygenation constant K (using least square method) with the result of ranged value 0.043 – 0.372 /day and Ultimate BOD 1.487 – 8.683mg/L. The values of deoxygenation rate at 5 stations were 0.182, 7.997, 7.236, 2.192, and 1.083 mg/L.day. The deoxygenation values were had a similar tendency with the amount of organic waste in the water column and its reduction rate due to the decomposition process.Keywords: Bedadung, BOD, Deoxygenation Rate, DOABSTRAKSungai Bedadung yang terletak di Kecamatan Rambipuji, Balung, Wuluhan dan Puger, merupakan sungai bagian hilir dimana zat pencemar organik bercampur, sehingga mempengaruhi kualitas perairan. Pencemar organik tersebut didekomposisi oleh mikroorganisme perairan sehingga menurunkan DO perairan. Tujuan penelitian ini adalah untuk mengkaji deoksigenasi Sungai Bedadung hilir. Data primer diperoleh dari pegukuran debit dan kualitas air (Temperatur, DO, dan BOD) di 5 (lima) titik pantau. Pengamatan BOD5 dan BOD2,4,6,8,10 dilakukan secara laboratorium. Peluruhan nilai BOD selama 10 hari cenderung memiliki tren polinomial dengan koefisien determinan berada pada nilai 0,8987 – 0,9781. Nilai peluruhan digunakan untuk menentukan nilai K (menggunakan metode least square) dan BOD ultimat. Nilai K di lima titik pantau menunjukkan rentang nilai 0,043 – 0,372 /hari dan BOD ultimat 1,487 – 8,683 mg/L. Sedangkan laju deoksigenasi di lima titik pantau menunjukkan nilai berturut-turut 0,182; 7,997; 7,236; 2,192; dan 1,083 mg/L./hari. Besar nilai deoksigenasi sangat ditentukan oleh banyaknya kandungan pencemar organik dalam air dan kecepatan reaksinya saat proses dekomposisi.Kata Kunci: Bedadung, BOD, Laju Deoksigenasi, DO

scholarly journals The Roles of Foreign Ownership and Growth Opportunity amid the Trade War: Evidence from an Emerging Country

2021 ◽  
Author(s):  
鬼谷 子
Keyword(s):  
Foreign Ownership ◽  
Least Square ◽  
Short Term ◽  
Moderator Variable ◽  
Growth Opportunity ◽  
Before And After ◽  
Trade War ◽  
Long Term Performance ◽  
Term Performance

In recent years investors tend to divert their investment to emerging economies in the Association of Southeast Asian Nations (ASEAN), especially during the U.S.-China trade war. The present study adopts the Weighted Least Square (WLS) and PROCESS macro tool to examine the effects of foreign ownership and growth opportunity on financial performance of Vietnamese listed firms over the period 2011-2018. Our findings show that foreign ownership plays as moderator variable in the relationship between short-term and long-term performance of firms. Empirical results also reveal that mediating effects of growth opportunity on short-term and long-term performance are different before and after the trade war. These findings have important implications for investors and managers in the ASEAN countries.

Analysis on Creep Characteristics of PC and RC Cylinders with Different Loading Ages

2014 ◽  
Vol 578-579 ◽  
pp. 631-636
Author(s):  
Guo Hui Cao ◽  
Yong Ming Chen ◽  
Jia Xing Hu
Keyword(s):  
Plain Concrete ◽  
Least Square ◽  
Correction Coefficient ◽  
Concrete Creep ◽  
Building Model ◽  
Creep Coefficient ◽  
Concrete Cylinders ◽  
Age Correction ◽  
Term Creep

Through a long time test for creep of 9 PC (plain concrete) and RC cylinders, obtained the long-term creep rule of PC and RC cylinders, the results show that the different loading ages of PC have a greater influence on the creep coefficient, the larger loading age of concrete cylinders, the smaller of concrete creep coefficient. The experiment indicates that the measured creep rule of creep coefficient is basically the same under different loading ages with the same reinforcement ratio of concrete cylinders, the loading age have smaller influence on long-term creep of reinforced concrete cylinders. Based on the measured long-term rule of concrete creep, using the least square method to nonlinear fitting of experimental data, obtained the final value of creep coefficient of the PC under different loading ages, compared the applicability of loading age correction coefficient in the China Institute of building model and CEB-FIP (1990) model for low intensity concrete (≤C40), the results show that the predicted results of loading age correction coefficient in the China Institute of building model are agree well with the measured values, and calculated values of loading age correction coefficient in CEB-FIP (1990) model is large, for low strong concrete (≤C40), the prediction values of loading age correction coefficient in the China Institute of building model should be adopted to linear interpolation.

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