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.
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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.
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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.
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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.
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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
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Modeling and Seismic Evaluation of nonstructural components Testing Frame for Experimental Evaluation of Suspended Ceiling Systems
Author: Andrei M. Reinhorn, Ki-Pung Ryu and Giuseppe Maddaloni | Size: 10.5 MB | Format:PDF | Quality:Original preprint | Publisher: MCEER , University at Buffalo, State University of New York | Year: 2010 | pages: 184 | ISBN: Technical Report MCEER-10-0004
This report describes the development of a new testing facility for the evaluation of suspended ceilings and
other nonstructural components that can be used with single or tandem shake tables. The 20 × 50 ft test
frame was designed to simulate realistic ceiling performance correlated with the response observed during
real earthquakes. The frame has dynamic characteristics with variable frequencies to match those typicallyfound in fl oors (or roofs) with suspended ceilings. It was also designed to accommodate various structural
materials and different framing layouts. Analytical models were developed using SAP2000 to estimate the
dynamic properties and complete the design of the test frame. The combined designs of the physical frame
and the shake table motion allow for testing a variety of suspended systems while simulating realistic fl oor
motions and eliminating side effects due to wall distortions. Finally, procedures for motion design that can
be implemented in other experimental facilities are introduced.
--------------------
General TABLE OF CONTENTS
INTRODUCTION
TEST FRAME DESIGN
ANALYTICAL MODELING
DESIGN AND EVALUATION OF FRAME’S ROOF TESTING MOTION
COMPENSATION PROCEDURE FOR SHAKE TABLE SIMULATION
SUMMARY, CONCLUDING REMARKS AND RECOMMENDATIONS
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evaluation of seismic retrofit of reinfirced concrete structures , Part II - Experimental Performance and Analytical Study of a Retrofitted Structural Model
ABSTRACT
This report is Part II of a two part series on the evaluation ofseismic retrofit methods for concrete
frame structures. It deals with the behavior of the entire structural system when several retrofit
techniques are applied to individual components. An analytical and an experimental study was
done on a scaled model of a structure and several retrofit techniques were evaluated. Part I
describes the evaluation of individual components retrofitted and tested with cyclic loading,
thar provided the base for modeling of the entire structure presented in this report.
In this report the evaluation of three retrofit techniques, i.e., concrete jacketing method, masonry
jacketing method, and partial frame masonry inf1ll, is presented based on an analytical study of
retrofitting a typical lightly reinforced frame designed according to ACI 318-89 only for gravity
loads (I.4D + L7L).
The jacketing technique is further evaluated based on an experimental and analytical study using
a 1:3 scale structural model subjected to simulated earthquake motion supplied by the seismic
simulator (shaking table) at SUNY/Buffalo.
The (jacketing) technique was applied only to selective portions of the structure, and it achieved
the limited improvement of strength and damage control as required in moderate seismicity
areas and as anticipated. This selected retrofit required only minimal structural interference
and may prove to be economically attractive.
The analytical modeling, based on component infonnation (obtained from the study presented
in Part I of this report series), shows that the overall response of retrofitted structures can be
adequately estimated, if good infonnation is available for the components.
---------------------------
General TABLE OF CONTENTS
INTRODUCTION.
RETROFIT OF GLD RIC FRAME STRUCTURES.
EXPERIMENTAL STUDY OF RETROFITTED R/C MODEL.
PERFORMANCE OF RETROFITTED R/C MODEL DURING
EARTHQUAKES.
CONCLUDING REMARKS.
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Posted by: mary - 11-15-2012, 01:16 PM - Forum: Archive
- No Replies
Hi
Soil stress field around driven piles
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Centrifugal model testing of foundation piles in axial loading
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