ASCE GSP 267-2016 NEW FRONTIERS IN CIVIL INFRASTRUCTURE.pdf

1、GEOTECHNICAL SPECIAL PUBLICATION NO. 267 GEO-CHINA 2016 NEW FRONTIERS IN CIVIL INFRASTRUCTURE SELECTED PAPERS FROM THE PROCEEDINGS OF THE FOURTHGEO-CHINA INTERNATIONAL CONFERENCE July 2527, 2016 Shandong, China SPONSORED BY Shandong University Shandong Department of Transportation University of Okla

2、homa Chinese National Science Foundation Geo-Institute of the American Society of Civil Engineers EDITED BY Hany Farouk Shehata, Ph.D. David Yanez Santillan Mohamed F. Shehata, Ph.D. Published by the American Society of Civil Engineers Published by American Society of Civil Engineers 1801 Alexander

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9、l Rights Reserved. ISBN 978-0-7844-8010-6 (PDF) Manufactured in the United States of America. Preface Toward building sustainable and longer civil infrastructures, the civil engineering community around the globe continues undertaking research and development to improve existing design, modeling, an

10、d analytical capability. Such initiatives are also enhanced by the on-going research toward new frontiers in civil infrastructures. This Geotechnical Special Publication (GSP) “New Frontiers in Civil Infrastructures“ is one of the several official proceedings of the GeoChina 2016 Conference and cont

11、ains technical papers that address several of these issues. It includes the full-length, peer-reviewed papers accepted for this conference. More than six hundred abstracts were received for this conference in response to the Call for Papers. The abstracts were reviewed by the Organizing and Scientif

12、ic Committees. All papers were reviewed following the same procedure and at the same technical standards of practice of the Geo-Institute of the American Society of Civil Engineers. All papers received a minimum of two full reviews coordinated by various track chairs and supervised by the GSP editor

13、s. Standard editorial review forms and checklists were applied to maintain uniform technical standards of the papers. As a result, 23 papers were accepted and published in this GSP designated for the new frontiers in civil infrastructures track. The authors of the accepted papers have addressed all

14、the comments of the reviewers to the satisfaction of the session chairs. It is hoped that readers of this GSP will be stimulated and inspired by the wide range of papers written by a distinguished group of national and international authors. The papers (like all GSPs papers) are eligible for discuss

15、ion in the Journal of Geotechnical and Geo-environmental Engineering and for ASCE award nominations. Publication of this quality of technical papers would not have been possible without the dedication and professionalism of the paper reviewers. The names of these reviewers appear in the acknowledgme

16、nt that follows. For any additional reviewers whose names were inadvertently missed, we offer our sincere apologies. We are thankful to Professor Shucai Li, Chair and Professor Dar Hao Chen, Co-chair of the organizing committee of the GeoChina 2016 Conference. Appreciation is extended to the authors

17、 and track chairs for their significant contributions. Thanks are also extended to ASCE Geo-Institute staff, Board and meeting Specialist, for their coordination and enthusiastic support to this conference. All of the submission activities of the papers for this conference were managed online by Con

18、ference Manager and we thank Professor Khalid El-Zahaby and Professor Hesham K. Amin of the Housing and Building National Research Center, Egypt for their help with additional reviews and help with the final preparations of GSP. The editors also acknowledge the assistance of Ms. Donna Dickert at ASC

19、E Geo-Institute in the final production of this Geotechnical Special Publication. *HR VP and Partner, EHE Consulting Group, Dubai, UAE. E-mail: H 2Professor and President, Housing and Building National Research Center (HBRC), Egypt. Abstract: This paper presents an advanced analysis of shallow found

20、ations using both strip and isolated footings. Taylor (1948) assumed uniform distributions for the contact stresses under the concentrically loaded footings, and most references and standards have followed this assumption. They have also used this distribution in the calculation of the bending momen

21、t acting on footings that are resting on sand and clay. In the literature, many researchers have presented distributions that depart from the Taylor assumption. Approximately equal distributions of contact stress in sand and clay are presented here. The distribution is of higher stress near the edge

22、s and lower stress under the column. This paper also examines the problem of contact stress distribution under strip and isolated footings using PLAXIS 2D-AE and 3D-AE, respectively. Linear elastic and Mohr-Coulomb models are adopted to simulate the soils. The results showed that the Mohr-Coulomb so

23、il model is more appropriate in the study of the contact stress distribution than the linear elastic model. The resulting contact stress distributions under the concentrically loaded strip and isolated footings are in good agreement with the previous research results. The contact stresses is highly

24、concentrated near edges and lower under the column. These concentrations of stresses near edges have long arms in the calculation of the maximum bending moment under the footings. Therefore, the maximum bending moment estimated by this modern analysis is higher than the one calculated using the Tayl

25、or (1948) assumption. Accordingly, references and standards should be updated to include the real distributions of contact stress. Large scale models should be established to determine the real distributions of the contact stress under footings. INTRODUCTION In modern design, designers usually assum

26、e that there is uniform contact stress under the footings. Taylor (1948) wrote the seminal paper for this assumption and has been widely cited. He assumed that the distribution of contact stress under a footing on sand is high under the columns and low or zero at the edges. He also assumed that the

27、distribution of contact stress under a footing on clay is high at the edges and slightly lower under the column. He stated that the general shape that combines sand and clay soils is a uniform distribution of the contact stress. This assumption was a reasonable *HR (a) flexible footing on clay, (b)

28、flexible footing on sand, (c) rigid footing on clay, (d) rigid footing on sand. P. 155, Donald P. Coduto, Foundation Design Principles and Practices 2ndEd. (a) (b) FIG. 2. Contact pressures distribution and settlement profiles; (a) clay, (b) sand. Page 144, Braja M. Das, Advanced Soil Mechanics 3rdE

29、d. The Committee of ACI 336 (1966) suggested an analysis and design procedure for combined footings and mats. In their report, they presented a suggested distribution of contact stress, as shown in Fig. 4. They stated that the assumption of a linear distribution is satisfactory. *HR (a) clay, (b) sa

30、nd. P. 406, Joseph E. Bowels, Handbook of Foundation Analysis and Design 5thEd. (a) Saturated Clay (b) Cohesion less Soil FIG. 4. Contact stress distribution under rigid footing; (a) Saturated clay, (b) sand. Page 6, ACI 336.2R 1966, reapproved 1980. Several researchers, starting from the 18thcentur

31、y, have studied the problem of the distribution of the contact stress under footings. They have used the elastic soil model, the Boussinesq model, a subgrade model, and the Winkler model, to represent the soil. The exact representation of the footing with an accurate simulation of the surrounding so

32、il is a very complex problem. These early researchers, working without the benefit of modern software, made great efforts to find a solution to this complex problem. They generally used models that did not take the type of soil into consideration. Some studies have used more advanced soil models, bu

33、t the objective of these studies was not to investigate the shape of the contact stress under footings in sandy and clayey soils. Therefore, there is still need for more realistic soil models and full-scale measurements. The prediction of contact stress and settlement under foundations depends on th

34、e modelling superstructure, the foundation, the soil, and their simultaneous interaction. This complex problem can be addressed through various methods of calculating contact stress under foundations. Subgrade Reaction Theory “Winkler Model” This model assumes that the soil acts as a bed of evenly s

35、paced, independent, linear springs. It also assumes that each spring deforms in response to the vertical stress applied directly to that spring and does not transmit any shear stress to the adjacent springs. However, in real soils the displacement distribution is continuous. The deflection under a l

36、oad can occur beyond the edge of the footing, and the deflection diminishes at some finite distance. This is not considered to be a realistic model because it cannot take into account the effect of the shear transmission of stresses to the adjacent support elements. Consequently, the distributions o

37、f displacements are continuous. The deflection of a point in the soil occurs not just because of the stress *HR VP and Partner of EHE Consulting Group, Dubai, UAE. E-mail: H 2Board Chairman, EHE-Consulting Group in Middle East, Egypt, UAE, SA. Abstract: This paper presents the effect of the soil str

38、ucture interaction on the modulus of subgrade reaction. Many of structural designers represent the footings as hinged support in the structural models, while the other de-signers represent the footings as a group of springs with spring coefficient K (kN/m). Designers assumed this modulus by differen

39、t equations that are not considering the soil structure interaction. This paper showed that, the soil structure interaction has a significant effect on the modulus of subgrade reaction. ksis not uniformly distributed under the footings. Using of soil structure interaction in the calculation of the n

40、ormal forces in columns is resulting a relatively change. Plane two-bay frames and two-bay by two-bay frames were studied using geotechnical and structural 2D and 3D finite element programs, respectively. It is investigated for the plane frames that, the normal force in the inner wall decreased and

41、it is increased for the outer walls. For the three dimensional frames, the inner columns normal force is decreased and the edge columns normal force is increased with the same normal force in the corner walls. For the complex structural systems, the distribution cannot be estimated, so the use of ge

42、otechnical finite element programs that can consider the soil, foundation, and superstructure effect is highly recommended for the practical and researcher engineers. INTRODUCTION The development of modern cities within large urban areas with limited surface space, has led to an increase in the rate

43、 of construction of high rise buildings with complex architectural design. The foundation of such complex buildings presents a geotechnical challenge where the soil structure interaction plays an important role to achieve the most economical design that satisfies all safety and serviceability requir

44、ements. The cooperation be-tween both geotechnical and structural engineers is necessary to reach a successful design. The sub-grade reaction modulus “ks“ can be considered as an appropriate interface between the geotechnical and structural engineers. It is well known that the sub-grade reaction mod

45、ulus is not a soil constant, but it depends on many factors such as the dimensions of footings, soil conditions, *HR tie beams that connect the footings. We can say that, the soil structure interaction is affecting the super-structure and the geotechnical analyses. The distributions of the subgrade

46、modulus are shown in Figure (6- a, b). *HR 0.35, 0.5, 0.75, 1.0, 1.5, 2.0 meters. These thick-nesses were modeled to represent different structural rigidities coefficients. The properties for all members of the concrete frame were as follows: unit weight of 25.0 kN/m3, Youngs modulus is 2.1107kN/m2,

47、 and Poissons ratio is 0.15. Own weight of slab was neglected. Each thickness of the slab was loaded by different distributed loads; 10, 30, and 60 kN/m2. Different loading levels were to provide the effect of increasing loads on the maximum settlement, average contact stresses, and the correspondin

48、g average subgrade modulus. Columns dimensions were 0.400.40 m2with 7-meter height. All footings have the same thickness of 1-meter. The dimensions of the inner footing were 44 m2, and the edge and corner footings were 33 m2and 22 m2, respectively. The 1-meter soil depth around the footings was deac

49、tivated during the calculation phase. The columns were permitted to rotate at the foundation level. The slab permitted to transfer bending moments to the columns in the two *HR&KLQD*63 $6&(directions. There are no tie beams connecting the foundations, because the long span between footings and to study the structural effects only. After performing the analysis, we found that the superstructure has a significant effect on the subgrade