Yatay yüklü kazık, palplanş perde ve ahşap ıska hesabı
Design of laterally loaded piles, sheet pile wals,flanking strutting and supporting trenches
- Tez No: 39557
- Danışmanlar: Y.DOÇ.DR. M. TUĞRUL ÖZKAN
- Tez Türü: Yüksek Lisans
- Konular: İnşaat Mühendisliği, Civil Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1994
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 185
Özet
ÖZET Bu çalışmada, yatay yüklü kazık, palplanş perde ve ahşap iksa problemleri çeşitli bilgisayar programları yardımıyla incelenmeye çalışılmıştır. Bunun için daha önceden elde bulunan ve sonlu elemanlar yöntemi kullanılarak geliştirilmiş olan, yatay yüklü kazık ve palplanş programlarına çeşitli alt programlar eklenerek modifiye edilmiştir. Çalışmada bilgisayar programlarının yanında teorik bilgiler de verilmeye çalışılmıştır. 2 ve 3. bölümlerde kazıklı temeller ve kazıklı temellerin taşıma gücü hakkında bilgiler verilmiş, 4. bölümde yatay yüklü kazıklar incelenmiştir. 5. bölümde palplanşlar ele alınmış, 6. bölümde ise yanal toprak basınçları hakkında bilgiler verilmiştir. 7. bölümde temel çukuru kaplama yapıları hakkında bilgi verilmiş, ayrıca ahşap iksalar için, geliştirilen bilgisayar program! kullanılarak çeşitli sonuç dosyaları elde edilmiş ve bunlar tablo ve grafikler yardımıyla gösterilmiştir. Burada çeşitli araştırmacılar tarafından (Terzaghi, Tschebotarioff, Klenner, Lehman) önerilen toprak basıncı dağılımları ele alınmış ve birbirleriyle karşılaştırılarak eğilme momenti, kesme kuvveti ve yatay deplasman bakımından değişimleri incelenmiştir. 8. bölümde bilgisayar programlarında kullanılan sonlu elemanlar yöntemi anlatılmıştır. 9. bölümde ise bilgisayar programları hakkında genel bilgiler verilmiş, veri giriş dosyalarının ne şekilde hazırlanacağı anlatılmıştır. Programların fortran dilindeki kodları, örnek giriş ve çıkış dosyaları ise ekler bölümünde gösterilmiştir. VI
Özet (Çeviri)
DESIGN OF LATERALLY LOADED PILES, SHEET PILE WALLS, FLANKING STRUTTING AND SUPPORTING TRENCHES SUMMARY Computer technology has developed more than anything in recent years. This is a good news for engineers who have to solve problems more efficiently. Today's engineers are spending more time on computers than before. Consequently solutions are getting more economical and safer. In this study, three computer programs have been developed. Using these programs, it is possible to solve some geotechnical problems. These problems are: 1) Laterally loaded piles 2) Lateral earth pressure (using Coulomb equations) 3) Sheet pile walls 4) Braced wall excavations Piles in groups are often subject to both axial and lateral loads. Early designers assumed piles could carry only axial loads with graphical methods being used to find the individual pile loads in a group. In this case a force polygon containing horizontal forces required battered piles, to carry the horizontal load a3 a component of the axial load. Sign posts, power poles, and many marine pilings represented a large class of partially embedded piles subject to lateral loads that tended to be designed as“laterally loaded poles. ”Current practice treats the full range of slender vertical (or battered) structural members, fully or partially embedded in the ground, as lateral piles. A large number of load tests have fully validated the concept of vertical piles being capable of carrying lateral loads via shear and bending rather than as“axial”loaded members. It is also common to us superposition to compute pile stresses when both axial and lateral loads are present. VIIEarly attempts to analyze a laterally loaded pile used the finite-difference method. This was used to obtain a series of nondimensional curves so that a user could enter the appropriate curve with the given lateral load and estimate the ground line deflection and maximum bending moment in the pile shaft. For obvious reasons/ only selected variations of soil modulus with depth could be input into this type of solution. The finite-difference method is not easy to program since the end and interior difference equations are not the same. The equations will also depend on whether the head is free or either translation and/or rotation is restrained. Other difficulties are encountered if the pile section is not constant, and soil stratification or other considerations require use of variable length segments. Of course, all these factors can be accounted for, but it is not very straightforward. The finite element method probably models the pile more realistically than finite difference method 3İnce both node displacement and rotation are used. This should better define the elastic curve of the pile than displacements alone as in the finite difference method. Boundary conditions are substantially easier to model both for zero displacement and/or rotation or for known values of node displacements. In the finite element method solution for lateral piles we should use the more general form of ks as ks m Ag + Bs Zn Or where there is concern that the ks profile does not increase without bound a form as ks = Ag + Bs tan x - can be used where Z= depth and B^pile width or diameter. This latter equation is not currently in computer program but can be easily added. One of these equations for ka together with the means in the program to reduce the ground line node VII!spring and to input selected soil node springs to account for lenses, voids, etc., and use of Xmax to model nonlinear effects is about as accurate a soil-pile model as can be justified by both pile loads and soil data. Even when we have a lateral pile load test to back compute the parameters As,Ba (and n) all we have are the parameters for that pile load test at that particular location on the 3ite. Substantial load test data shows that different values of ks can be obtained if several piles are tested at the same site. The site variability justifies the using of a single value of ka to Xmax rather than trying to move along a nonlinear q vs. 8 curve to obtain ks based on the current value of node displacement. Since most lateral piles are usually designed for lateral displacements on the order of 6 to 10 mm at the soil line and the pile being very much stiffer than the soil the pile flexural resistance EI dominates so that bending moments in the pile are little affected over a very large range of ks. The ground line deflections are heavily dependent on ks; however, if they are tolerable over a fairly wide range of values the use of a simple expression for k3 can be justified. On the other hand the lateral earth pressure is a significant design parameter in a number of foundation engineering problems. Retaining and sheet-pile walls, both braced and unbraced excavations, grain pressure on silo walls and bins, and earth or rock pressure on tunnel walls and other underground structures require a quantitative estimate of lateral pressure on a structural member for either a design or stability analysis. The method of plastic equilibrium as defined by the Mohr rupture envelope is most generally used for estimating the lateral pressure from earth and other materials such as grain, coal, and ore. On occasion one may use the finite-element (of the elastic continuum) method but this has several distinct disadvantages for most routine design. Pressures on tunnel liners and large buried conduits are more suitable for the finite element method than most other analyses. Earth pressures are developed during soil displacements (or strains) but until the soil is on the verge of failure, as defined by the Mohr' s rupture envelope, the stresses are indeterminate. They are also somewhat indeterminate at rupture since it is difficult to produce simultaneously everywhere a plastic IXequilibrium state in a soil mass-most times it is a progressive event. Nevertheless it is common practice to analyze this as an ideal state occurrence, both for convenience and from limitations on obtaining the necessary soil parameters with a high degree of reliability. It is a legal necessity when new construction is begun in a developed area to provide protection to the adjacent existing buildings when excavation in the new site is to any depth which may cause loss of bearing capacity, settlements, or lateral movements to existing property. New construction may include cut-and-cover work when public transportation or public utility systems are installed below ground and the depth is not sufficient to utilize tunneling operations. The new construction may include excavation from depths of 1 to perhaps 15 m or more below existing ground surface for placing of one to three or more basements and subbasements. This type of work requires installation of some kind of systems of retaining structure termed a cofferdam, braced sheeting, or slurry wall together with a means of holding the retaining structure in position. The retainina structure mav be constructed of one of the 1) Sheet piling (steel, concrete, or wood) 2) Soldier beams (or piles) with or without lagging 3) Drilled- in-place concrete piles (or piers) 4) Concrete poured in a cavity retained with slurry (a dense liquid) producing a slurry wall System to hold the retaining wall in place include: 1) Wales and struts or rakers 2) Compression rings (when excavation is relatively small in plan) 3) Tieback anchorages Sheet piling is commonly used for retaining excavations because it has the highest-strength/weight ratio, and much of the piling is reusable and can generally be easily installed either with sheet pile hammers or with vibratory driving devices.Sheet pile walls are widely used for both large and small waterfront structures ranging from small pleasure- boat launching facilities to large dock structures for ocean going ships. Piers jutting into the harbor consisting of two rows of sheet piling are widely used. Sheet piling is also used for beach erosion protection, to assist in stabilizing ground slopes, for shoring walls of trenches and other excavations, and for cofferdams. When the wall is under about 3 m in height it may be cantilevered; however, for larger wall heights it is usually anchored. There are no exact methods to analyze/design sheet pile type walls. Both field observations and laboratory model tests show that there is a complex interaction of excavation depth, wall material stiffness, and passive pressure resistance. With anchored wall there is also the anchor geometry and initial anchor prestress (or load) to further complicate the analysis. Current analysis methods may be divided into two groups : 1) Discrete element methods-in this category are finite difference and finite element approaches. 2) Classical methods-procedures which involve extremely simplifying assumptions and rigid body statics. The finite element method using beam elements is used in this study as providing the best solution since there is more realistic modeling of the wall and including wall and anchor rod flexibility as well as reasonably incorporating the soil in an interaction process with the wall. The finite difference method is not further considered as it offers no advantage over the finite element method and in fact is more difficult to use. It has the disadvantage of requiring constant length elements over the full pile length and the stiffness matrix cannot be banded. Also it is difficult to model boundary conditions of zero displacement and rotation. XI
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