Author: Van Dam, Tom Taylor, Peter Fick, Gary VanGeem, Martha Lorenz, Emily | Size: 22.34 MB | Format:PDF | Quality:Original preprint | Publisher: Iowa State University, Ames | Year: 2012 | pages: 114
Developed as a more detailed follow-up to a 2009 briefing document, Building Sustainable Pavement with Concrete, this guide provides a clear, concise, and cohesive discussion of pavement sustainability concepts and recommended practices for maximizing the sustainability of concrete pavements. The intended audience includes decision makers and practitioners in both owner-agencies and supply, manufacturing, consulting and contractor businesses. Readers will find individual chapters with the most recent technical information and best practices related to concrete pavement design, materials, construction, use/operations, renewal and recycling. In addition readers will find chapters addressing issues specific to pavement sustainability in the urban environment and the evaluation of pavement sustainability.
Code:
***************************************
Content of this section is hidden, You must be registered and activate your account to see this content. See this link to read how you can remove this limitation:
An unbonded concrete overlay (UBCO) system is a Portland cement concrete (PCC) overlay that is separated from an existing PCC pavement by an asphalt concrete (AC) interlayer. Current UBCO design procedures are based on empirical equations or highly simplified mechanistic models. To overcome the limitations, fracture mechanics concepts, specifically the finite element method-based cohesive zone model (CZM), are introduced in this research as a new paradigm for analyzing UBCOs with the ultimate goal of establishing a more rational design procedure. To illustrate the advantages of a fracture mechanics-based approach to design, specific attention is paid to but one type of failure associated with pavement structures: reflection cracking. The design against reflection cracking approach relies on a load-carrying capacity equivalency between the designed UBCO and a reference newly designed single layer PCC pavement. An illustrative fracture mechanics-based design procedure for UBCOs is developed and proposed by a large number of crack propagation simulations of both the UBCO composite and the reference single layer pavement. Preliminary comparisons of the results with field observations suggest that the fracture mechanics paradigm offers promise for improved design of UBCOs against reflection cracking and other potential loading conditions that could be analyzed using nonlinear fracture mechanics models. It is recommended that an experimental program be established to assess the accuracy of the model predictions, and additional experiments and three-dimensional fracture mechanics simulations be considered to provide additional insights as to whether UBCOs can be “thinned-up”.
Code:
***************************************
Content of this section is hidden, You must be registered and activate your account to see this content. See this link to read how you can remove this limitation:
This research investigated the effects of changing the cementitious content required at a given water-to-cement ratio (w/c) on workability, strength, and durability of a concrete mixture. An experimental program was conducted in which 64 concrete mixtures with w/c ranging between 0.35 and 0.50, cementitious content ranging from 400 to 700 per cubic yard (pcy), and containing four different supplementary cementitious material (SCM) combinations were tested. The fine-aggregate to total-aggregate ratio was fixed at 0.42 and the void content of combined aggregates was held constant for all the mixtures. Fresh (i.e., slump, unit weight, air content, and setting time) and hardened properties (i.e., compressive strength, chloride penetrability, and air permeability) were determined. The hypothesis behind this study is that when other parameters are kept constant, concrete properties such as strength, chloride penetration, and air permeability will not be improved significantly by increasing the cement after a minimum cement content is used. The study found that about 1.5 times more paste is required than voids between the aggregates to obtain a minimum workability. Below this value, water-reducing admixtures are of no benefit. Increasing paste thereafter increased workability. In addition, for a given w/c, increasing cementitious content does not significantly improve compressive strength once the critical minimum has been provided. The critical value is about twice the voids content of the aggregate system. Finally, for a given w/c, increasing paste content increases chloride penetrability and air permeability.
Code:
***************************************
Content of this section is hidden, You must be registered and activate your account to see this content. See this link to read how you can remove this limitation:
The focus of this project was on identifying critical properties that control long‐term performance of repair concrete, especially rapid-setting materials extended using pea gravel (maximum size aggregate 9.5 mm). In the first phase of this project, four commercial rapid‐setting materials (CRSMs) were selected and development of mixture proportions in terms of optimum pea gravel content and water content was performed. Optimized mixtures were further evaluated at three different initial temperature conditions. The properties evaluated included workability, setting time, rate of compressive strength developed, slant shear bond strength, freeze‐thaw resistance, air‐void system characteristics of hardened concrete, drying shrinkage and cracking potential. It was observed that some of the CRSMs evaluated did not meet requirements of ASTM C 928. All, except one, CRSMs tested exhibited low resistance to freezing and thawing but all had high resistance to cracking. In the second phase of the project, rapid‐setting self‐consolidating concrete (RSSCC) was developed using ternary blend of cementitious materials, high‐range water reducer (HRWR) and accelerators. Slump flow, visual stability index (VSI), compressive strength at various ages and the power consumption values for the mortar mixer indicated that a five minutes mixing sequence involving a 2‐Step addition of HRWR produces stable RSSCC mixture. The results of various tests carried out indicate that it is possible to develop a small aggregate size‐based self‐consolidating repair concrete that achieves a compressive strength of 19 MPa at the end of 6 hrs, has good bond characteristics and excellent freezing and thawing durability (DF>90%). The sensitivity of RSSCC to aggregate characteristics and production variables was also evaluated. Specifically, the influence of aggregate gradation and aggregate moisture content using different types of mixers and re‐mixing after a period of rest was evaluated. It was observed that variation in aggregate moisture content and aggregate gradation resulted in noticeable changes in fresh concrete properties such as the slump flow, stability and V‐funnel flow values. While changes in moisture content and gradation of aggregates had an impact on the early (6 h) compressive strength, the compressive strength at the end of 24 hours was not significantly affected.
Code:
***************************************
Content of this section is hidden, You must be registered and activate your account to see this content. See this link to read how you can remove this limitation:
The main issue associated with this research is if cheaper alternatives can be configured for subbase construction. Subbase layers have certain functions that need to be fulfilled in order to assure adequate pavement performance. One key aspect is resistance to erosion, and assessment of each of these functions relative to different alternatives is key to understanding the capability of different alternatives to perform adequately. In this respect, this project was poised to examine the design assumptions associated with each alternative and provide design recommendations accordingly to include test methods and material specifications. This report describes some of the work accomplished by summarizing data on subbase performance and testing relative to concrete pavement subbase and subgrade erosion but mainly addresses guidelines for concrete pavement subbase design. Findings from field investigations are discussed to identify factors associated with erosion. An approach to mechanistically consider the erosion process was introduced and review of current design procedures was conducted to reveal how they address erosion. This review was extended to include erosion models described in the literature as a means to shed light on the relationship between measurable material properties and performance. Additionally, past and current design procedures relative to erosion were reviewed in terms of test methods, erosion models, and their utility to characterize subbase materials with respect to erosion resistance. With this information, a new test configuration was devised that uses a rapid tri-axial test and a Hamburg wheel-tracking device for evaluating erodibility with respect to the subbase type and degree of stabilization (cement content). Test devices, procedures, and results are explained and summarized for application in mechanistic design processes. A proposed erosion model was validated by comparing erosion predictions to erosion results. Several computer program analyses were conducted to assess the design and performance implications of different subbases alternatives. Guidelines are provided to promote economical and sustainable design of concrete pavement subbases.
Code:
***************************************
Content of this section is hidden, You must be registered and activate your account to see this content. See this link to read how you can remove this limitation:
WhiteSmoke is an all-in-one English writing tool that provides grammar, spelling, punctuation and style checks. Integrated into WhiteSmoke are world-renowned word and text translation and document templates. WhiteSmoke is activated in a single click from any text application and browser. It is an added-value product that ensures a higher standard of English writing. Corporations, governments, academic institutions and individuals throughout the world use WhiteSmoke to enhance their daily communication. WhiteSmoke encourages the writing process, calls out potential errors for consideration, and offers suggestions for improvement. WhiteSmoke is suitable for everyone, including native and non-native speakers. It is the most versatile and powerful program of its kind, catching more errors than any other program, including the most popular word processing programs. At home, in the office or on the go--WhiteSmoke guarantees all your daily correspondence is error free.
Private Note:
***************************************
Content of this section is hidden, You must be registered and activate your account to see this content. See this link to read how you can remove this limitation:
***************************************
Content of this section is hidden, You must be registered and activate your account to see this content. See this link to read how you can remove this limitation:
***************************************
Content of this section is hidden, You must be registered and activate your account to see this content. See this link to read how you can remove this limitation:
***************************************
Content of this section is hidden, You must be registered and activate your account to see this content. See this link to read how you can remove this limitation:
***************************************
Content of this section is hidden, You must be registered and activate your account to see this content. See this link to read how you can remove this limitation:
***************************************
Content of this section is hidden, You must be registered and activate your account to see this content. See this link to read how you can remove this limitation:
Abstract: This report focuses on improved physical techniques for small-scale reinforced concrete structures subjected to seismic loadings. Particular emphasis is placed on the development of a model concrete mix to accurately model the important strength and stiffness properties of full-scale prototype concrete. The gradation of aggregate used in the mix, along with the aggregate to cement ratio, are shown to be critical in achieving sufficiently low tensile strength while still maintaining acceptable critical strain levels at compressive failure of the model concrete. Four types of model reinforcement with different bond characteristics are also studied. Using these model materials, the adequacy of bond between model concrete and model reinforcement is then examined with experiments on a series of 1/6 scale model assemblages of a prototype beam subjected to reversing loads. It is concluded that small scale elements fabricated with annealed, threaded rod reinforcement best meet the similitude requirements for strength, stiffness, cyclic degradation of stiffness, energy absorption during fully reversing loads, and failure mode after severe cycling.
Code:
***************************************
Content of this section is hidden, You must be registered and activate your account to see this content. See this link to read how you can remove this limitation:
Requesting from anyone who have this paper Ground movements due to pile driving in an excavation in soft soil by
I H Wong, T S Chua and published by Canadian Geotechnical Journal, 1999, Vol. 36, No. 1 : pp. 152-160
Hybrid Control of Seismic-Excited Nonlinear and Inelastic Structural Systems
Author: J. N. Yang, Z. Li and A. Danielians . | Size: 40 MB | Format:PDF | Quality:Scanner | Publisher: NCEER | Year: 1991 | pages: 110 | ISBN: Technical Report NCEER-91-0020
PART I
TABLE OF CONTENTS
SECTION TITLE PAGE
1. INTRODUCTION I-I
2. FORMULATION 1-4
2.1 General Nonlinear or Hysteretic Structures 1-4
2.2 Instantaneous Optimal Control 1-7
2.3 Time-Variant Linear Systems 1-9
2.4 Instantaneous Optimal Control with 1-11
Acceleration and Velocity Feedback
2.5 Simulation of Controlled Response for 1-12
Hysteretic Structural System
3. NUMERICAL EXAMPLE 1-16
4. CONCLUSION I-54
5. REFERENCES I-55
APPENDIX A FOURTH-ORDER RUNGE-KUTTA METHOD I-59
APPENDIX B INSTANTANEOUS OPTIMAL 1-61
CONTROL ALGORITHMS
PART II
TABLE OF CONTENTS
SECTION TITLE PAGE
1. INTRODUCTION II-I
2. OPTIMAL CONTROL OF INELASTIC 11-3
STRUCTURAL SYSTEMS
2.1 Nonlinear Hysteretic Model for Inelastic Systems 11-3
2.2 Equations of Motion 11-3
2.3 Instantaneous Optimal Control 11-8
2.4 Sufficient Condition for Optimal Control 11-10
2.5 Estimation of Hysteretic Component Vector V 11-10
3. NUMERICAL EXAMPLE 11-12
4. CONCLUSIONS 11-28
5. REFERENCES 11-29
Code:
***************************************
Content of this section is hidden, You must be registered and activate your account to see this content. See this link to read how you can remove this limitation:
***************************************
Content of this section is hidden, You must be registered and activate your account to see this content. See this link to read how you can remove this limitation:
![[Image: 78194125800516091143.png]](https://pic.civilea.com/images/78194125800516091143.png)
![[Image: info.png]](http://postgen.civilea.com/icon/info.png){kind=icon}
![[Image: download.png]](http://postgen.civilea.com/icon/download.png){kind=icon}
![[Image: 19774858914211577707.png]](https://pic.civilea.com/images/19774858914211577707.png)
![[Image: 29162443856690287760.png]](https://pic.civilea.com/images/29162443856690287760.png)
![[Image: 15695281517430808554.png]](https://pic.civilea.com/images/15695281517430808554.png)
![[Image: 09348643675112889392.png]](https://pic.civilea.com/images/09348643675112889392.png)
![[Image: screen.png]](http://postgen.civilea.com/icon/screen.png){kind=icon}
![[Image: 26545129078433883602.jpg]](https://pic.civilea.com/images/26545129078433883602.jpg)
![[Image: tips.png]](http://postgen.civilea.com/icon/tips.png){kind=icon}
![[Image: homepage.png]](http://postgen.civilea.com/icon/homepage.png){kind=icon}
![[Image: mirror.png]](http://postgen.civilea.com/icon/mirror.png){kind=icon}
![[Image: crack.png]](http://postgen.civilea.com/icon/crack.png){kind=icon}
![[Image: password.png]](http://postgen.civilea.com/icon/password.png){kind=icon}
![[Image: 23579521963513338017.png]](https://pic.civilea.com/images/23579521963513338017.png)
![[Image: comments.png]](http://postgen.civilea.com/icon/comments.png){kind=icon}
![[Image: 71361252897160230775.jpg]](https://pic.civilea.com/images/71361252897160230775.jpg)
![[Image: 67193765559872464184.jpg]](https://pic.civilea.com/images/67193765559872464184.jpg)