DOCSLIB.ORG

COMPRESSION WOOD DOES NOT FORM in the ROOTS of PINUS RADIATA Linda C.Y. Hsu1*, John C.F. Walker1, Brian G. Butterfield2 and Sand

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
COMPRESSION WOOD DOES NOT FORM in the ROOTS of PINUS RADIATA Linda C.Y. Hsu1*, John C.F. Walker1, Brian G. Butterfield2 and Sand IAWA Journal, Vol. 27 (1), 2006: 45–54 COMPRESSION WOOD DOES NOT FORM IN THE ROOTS OF PINUS RADIATA Linda C.Y. Hsu1*, John C.F. Walker1, Brian G. Butterfield2 and Sandra L. Jackson2 SUMMARY We investigated the potential for the roots of Pinus radiata D. Don to form compression wood. Compression wood was not observed in either the tap or any lateral roots further than 300 mm from the base of the stem. This suggests that either the roots do not experience the stresses required to induce compression wood formation, or that they lack the ability to form it. Roots artificially subjected to mechanical stress also failed to develop compression wood. It is therefore unlikely that an absence of a compressive load on buried roots can account for the lack of compression wood. Application of auxin to the cambia of lateral roots was similarly ineffective at inducing the formation of compression wood. These ob- servations suggest that the buried roots of radiata pine lack the ability to develop compression wood. We also report the formation of an atypical S3 wall layer in the mechanically-stressed and auxin-treated tracheids and suggest that a reaction wood that is different to compression wood may well form in roots. Key words: Auxin, compression wood, mechanical stress, radiata pine, roots. INTRODUCTION Woody roots function to transmit the load of the stem to the soil as well as to transport water and nutrients to the canopy. In gymnosperms, tracheids, that make up the bulk of the xylem, carry out both of these tasks. Although the xylem of roots and stems undertake similar functions, root xylem appears to be exposed to less mechanical stress as the longitudinal maturation strains measured in roots are consistently smaller than those for stems (Gartner 1997; Stokes et al. 1998). Nonetheless, root xylem, like stem xylem, was responsive to differences in load as both eccentric radial growth (Fayle 1968; Timell 1986; Stokes et al. 1998; Niklas 1999) and changes in mechanical properties of the wood occurred (Stokes & Mattheck 1996; Niklas 1999). The measured alterations 1) School of Forestry, University of Canterbury, Private Bag 4800, Christchurch, New Zealand. 2) School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand. *) Current address: Crop & Food Research, Private Bag 4704, Christchurch, New Zealand [E-mail: [email protected]]. Associate Editor: Barbara Gartner Downloaded from Brill.com10/03/2021 09:42:39PM via free access 46 IAWA Journal, Vol. 27 (1), 2006 Hsu, Walker, Butterfield & Jackson — Compression wood absence in roots 47 in compressive strength and stiffness imply that tracheid morphology and/or cell wall composition/thickness have changed. In gymnosperm stems such changes occur on the compression side of an unbalanc- ed load caused by leaning of the stem or branching (Westing 1965, 1968; Boyd 1973; Wilson & Archer 1977; Siripatanadilok & Leney 1985; Yoshizawa et al. 1985; Yoshi- zawa & Idei 1987; Lee & Eom 1988). In extreme cases this compression wood was red- dish brown in colour and contained shorter tracheids that were rounded in cross section. The cylindrical shape of these cells disrupted the interlocked packing of the xylem and resulted in air spaces. In addition, the secondary cell wall was thickened even though the S3 and warty layers were absent. Cellulose microfibril distribution in the S2 layer was altered with a larger microfibril angle and larger variance in microfibril angle. Deep helical checking was also present in this layer. Finally, lignin distribution in the S2 layer was also different with more lignin in the outer portion. It is important to note that compression wood is not an all or nothing biological response. Rather it is a continuum ranging from severe (described above) to mild. Mild forms are reported to lack red coloration, have typical interlocked tracheids without air spaces with slightly perturbed cellulose microfibrils, an intact 3S layer and slightly modified lignin deposi- tion in the S2 layer. The occurrence of compression wood in gymnosperm roots is controversial. Most re- ports claim that buried roots do not form compression wood (Westing 1965; Fayle 1968; Timell 1986) except when close to the base of the stem (Hartman 1942; Fayle 1968). Nor was it possible to induce the formation of compression wood in buried roots with applied mechanical force (Westing 1965; Fayle 1968; Timell 1986) or the plant growth regulator auxin (Fayle 1968). Since these approaches successfully induced compression wood to form in stems the implication was that stems and roots were different. As a result of these observations it was concluded that roots are not capable of forming compres- sion wood (Fayle 1968). Unfortunately, the bulk of these studies used red coloration as the defining feature for the presence of compression wood. We now realise that mild forms of compression wood lack red coloration. Furthermore, there are reasons to expect milder compression wood in roots. Firstly, roots seem to experience less mechanical stress than shoots (Gartner 1997; Stokes et al. 1998) and one would expect reduced stress to cause a milder reaction. Secondly, the changes in tracheid structure that occur during compression wood formation inhibit water transport (Spicer & Gartner 1998). Given that severe compression wood is likely to inhibit water transport milder forms of compression wood may well be the only type to occur in roots. The fact that the mechanical properties of root wood respond to differential loading (Niklas 1999) shows that roots do indeed experience the biophysical stresses required to induce changes in xylem structure. Since compression wood can be present in mild forms that would have escaped detection in previous studies, we have looked at pine roots using techniques that are capable of perceiving subtle changes in this tissue. Scan- ning electron microscopy, ultraviolet (UV) epifluorescence microscopy and X-ray dif- fraction were used to distinguish differences in morphology, lignification and cellulose microfibril angle that may occur in the mild forms of compression wood. We examined several lateral and tap roots of radiata pine and also attempted to induce compression Downloaded from Brill.com10/03/2021 09:42:39PM via free access 46 IAWA Journal, Vol. 27 (1), 2006 Hsu, Walker, Butterfield & Jackson — Compression wood absence in roots 47 wood formation with both mechanical stress and the exogenous application of auxin. Radiata pine was chosen for this study because of its economic significance to many Southern Hemisphere economies. MATERIALS AND METHODS Root anatomy Roots from 8 ramets of four different clones (two trees from each clone) of 3-year- old radiata pine (Pinus radiata D. Don) were used. The trees were grown and provided by Trees and Technology Ltd, Te Teko, New Zealand. The unexposed large main tap and lateral roots were harvested from each tree. In total, 48 roots were examined. Each root was dissected at three positions, the transition zone (point where the tap root and shoot meet or the point where the lateral root met the tap root), the middle portion of the root and close to the root tip. All samples were stored in 30% ethanol. Applying mechanical stress or auxin in roots Six straight 7-year-old Pinus radiata trees from a single clone in Burnham experi- mental forest, c. 30 km south of Christchurch, New Zealand were used. The stony soil at Burnham resulted in shallow lateral roots, which were excavated in an annulus some 0.5–0.7 metres from the stem, permitting the selection of the five largest and straightest portions of rootwood. This was sufficiently distant from the stem to avoid the pos- sibility of the stem influencing the development of compression wood. The five roots of each tree were subjected to 1% α-napthalene acetic acid (NAA, Sigma Australia), 0.1% NAA, mechanical bending, and the controls for the biochemical and mechanical treatments. For NAA applications, the NAA was mixed with lanoline to make NAA con- centrations of 1% and 0.1%. A small hole (5 mm in both diameter and depth) was drilled on the upper side of each root. The holes were filled with the lanoline /NAA mixture and then bandaged with a plastic bag before the root was re-covered with soil. The drill hole of the control root was filled with pure lanoline. For the mechanical bending treatment, a saw-horse was adapted to apply a vertical tensile load to the root. Using a pulley system, one side was attached to the root while the other side carried a 28–30 kg weight in the form of four concrete blocks. One root per tree provided a control sample, which was first exposed and then re-covered with soil without applying any load. During the four-month treatment period between September and December 2001 (spring season in the Southern Hemisphere), when the speed of cambium division in- creases in plants, tree number 5 displayed the largest diameter increment for both 1% and 0.1% NAA applications. Hence, the five roots from this tree were selected for in- vestigating the formation of compression wood under SEM. The other roots were cut in disks and observed by eye for discoloration associated with compression wood. Compression wood determination To look for potential compression wood we examined tracheid anatomy, lignin distribution and cellulose microfibril angle on both the upper and lower or the auxin- treated and untreated sides of the roots. Anatomy was observed using scanning electron Downloaded from Brill.com10/03/2021 09:42:39PM via free access 48 IAWA Journal, Vol. 27 (1), 2006 Hsu, Walker, Butterfield & Jackson — Compression wood absence in roots 49 microscopy (Leica 440i; Meylan & Butterfield 1978). Adjacent samples were section- ed at 10 μm thickness with a sledge microtome and UV epifluorescence microscopy (Olympus IX 70) was used to detect differences in lignin autofluorescence.
Load more

Recommended publications
  • The MODIFIED COMPRESSION FIELD THEORY: THEN and NOW
    SP-328—3 The MODIFIED COMPRESSION FIELD THEORY: THEN AND NOW Vahid Sadeghian and Frank Vecchio Abstract: The Modified Compression Field Theory (MCFT) was introduced almost 40 years ago as a simple and effective model for calculating the response of reinforced concrete elements under general loading conditions with particular focus on shear. The model was based on a smeared rotating crack concept, and treated cracked reinforced concrete as a new orthotropic material with unique constitutive relationships. An extension of MCFT, known as the Disturbed Stress Field Model (DSFM), was later developed which removed some restrictions and increased the accuracy of the method. The MCFT has been adapted to various types of finite element analysis programs as well as structural design codes. In recent years, the application of the method has been extended to more advanced research areas including extreme loading conditions, stochastic analysis, fiber-reinforced concrete, repaired structures, multi- scale analysis, and hybrid simulation. This paper presents a brief overview of the original formulation and its evolvement over the last three decades. In addition, the adaptation of the method to advanced research areas are discussed. It is concluded that the MCFT remains a viable and effective model, whose value lies in its simple yet versatile formulation which enables it to serve as a foundation for accurately solving many diverse and complex problems pertaining to reinforced concrete structures. Keywords: nonlinear analysis; reinforced concrete; shear behavior 3.1 Vahid Sadeghian and Frank Vecchio Biography: Vahid Sadeghian is a PhD graduate at the Department of Civil Engineering at the University of Toronto. His research interests include hybrid (experimental-numerical) simulation, multi-platform analysis of reinforced concrete structures, and performance assessment of repaired structures.
    [Show full text]
  • Design of Compression Members
    CE 405: Design of Steel Structures – Prof. Dr. A. Varma CHAPTER 3. COMPRESSION MEMBER DESIGN 3.1 INTRODUCTORY CONCEPTS • Compression Members: Structural elements that are subjected to axial compressive forces only are called columns. Columns are subjected to axial loads thru the centroid. • Stress: The stress in the column cross-section can be calculated as P f = (2.1) A where, f is assumed to be uniform over the entire cross-section. • This ideal state is never reached. The stress-state will be non-uniform due to: - Accidental eccentricity of loading with respect to the centroid - Member out-of –straightness (crookedness), or - Residual stresses in the member cross-section due to fabrication processes. • Accidental eccentricity and member out-of-straightness can cause bending moments in the member. However, these are secondary and are usually ignored. • Bending moments cannot be neglected if they are acting on the member. Members with axial compression and bending moment are called beam-columns. 3.2 COLUMN BUCKLING • Consider a long slender compression member. If an axial load P is applied and increased slowly, it will ultimately reach a value Pcr that will cause buckling of the column. Pcr is called the critical buckling load of the column. 1 CE 405: Design of Steel Structures – Prof. Dr. A. Varma P (a) Pcr (b) What is buckling? Buckling occurs when a straight column subjected to axial compression suddenly undergoes bending as shown in the Figure 1(b). Buckling is identified as a failure limit-state for columns. P P cr Figure 1. Buckling of axially loaded compression members • The critical buckling load Pcr for columns is theoretically given by Equation (3.1) π2 E I Pcr = (3.1) ()K L 2 where, I = moment of inertia about axis of buckling K = effective length factor based on end boundary conditions • Effective length factors are given on page 16.1-189 of the AISC manual.
    [Show full text]
  • Structural Design
    115 Chapter 7 Structural design INTRODUCTION thrust, shear, bending moments and twisting moments), Structural design is the methodical investigation of the as well as stress intensities, strain, deflection and stability, strength and rigidity of structures. The basic reactions produced by loads, changes in temperature, objective in structural analysis and design is to produce shrinkage, creep and other design conditions. Finally a structure capable of resisting all applied loads without comes the proportioning and selection of materials for failure during its intended life. The primary purpose the members and connections to respond adequately to of a structure is to transmit or support loads. If the the effects produced by the design conditions. structure is improperly designed or fabricated, or if the The criteria used to judge whether particular actual applied loads exceed the design specifications, proportions will result in the desired behavior reflect the device will probably fail to perform its intended accumulated knowledge based on field and model tests, function, with possible serious consequences. A well- and practical experience. Intuition and judgment are engineered structure greatly minimizes the possibility also important to this process. of costly failures. The traditional basis of design called elastic design is based on allowable stress intensities which are chosen Structural design process in accordance with the concept that stress or strain A structural design project may be divided into three corresponds to the yield point of the material and should phases, i.e. planning, design and construction. not be exceeded at the most highly stressed points of Planning: This phase involves consideration of the the structure, the selection of failure due to fatigue, various requirements and factors affecting the general buckling or brittle fracture or by consideration of the layout and dimensions of the structure and results in permissible deflection of the structure.
    [Show full text]
  • 3. BEAMS: STRAIN, STRESS, DEFLECTIONS the Beam, Or
    3. BEAMS: STRAIN, STRESS, DEFLECTIONS The beam, or flexural member, is frequently encountered in structures and machines, and its elementary stress analysis constitutes one of the more interesting facets of mechanics of materials. A beam is a member subjected to loads applied transverse to the long dimension, causing the member to bend. For example, a simply-supported beam loaded at its third-points will deform into the exaggerated bent shape shown in Fig. 3.1 Before proceeding with a more detailed discussion of the stress analysis of beams, it is useful to classify some of the various types of beams and loadings encountered in practice. Beams are frequently classified on the basis of supports or reactions. A beam supported by pins, rollers, or smooth surfaces at the ends is called a simple beam. A simple support will develop a reaction normal to the beam, but will not produce a moment at the reaction. If either, or both ends of a beam projects beyond the supports, it is called a simple beam with overhang. A beam with more than simple supports is a continuous beam. Figures 3.2a, 3.2b, and 3.2c show respectively, a simple beam, a beam with overhang, and a continuous beam. A cantilever beam is one in which one end is built into a wall or other support so that the built-in end cannot move transversely or rotate. The built-in end is said to be fixed if no rotation occurs and restrained if a limited amount of rotation occurs. The supports shown in Fig.
    [Show full text]
  • A Comprehensive Explanation of Compression Strength Differences Between Various CFRP Materials: Micro-Meso Model, Predictions, Parameter Studies
    Composites: Part A 40 (2009) 376–387 Contents lists available at ScienceDirect Composites: Part A journal homepage: www.elsevier.com/locate/compositesa A comprehensive explanation of compression strength differences between various CFRP materials: Micro-meso model, predictions, parameter studies S. Pansart a,*,1, M. Sinapius a,b, U. Gabbert b a German Aerospace Center, Institute of Composite Structures and Adaptive Systems, Lilienthalplatz 7, 38108 Braunschweig, Germany b University of Magdeburg, Department of Mechanical Engineering, Computational Mechanics, Universitätsplatz 2, 39106 Magdeburg, Germany article info abstract Article history: The present work proposes a model to predict the compression strength of CFRP as a function of various Received 26 August 2008 material characteristics: fiber properties and volume content, non-linear matrix properties, interface Received in revised form 7 December 2008 properties, residual strains, fiber misalignment, ply waviness, and interlaminar properties. For this, a Accepted 2 January 2009 three-step FE-based approach is developed considering (i) fiber microbuckling, (ii) wavy ply mesobuck- ling, and (iii) the mutual influence of these two. This approach is then applied to investigate the relative contribution of the mentioned material characteristics on compression strength deficits of NCF (Non- Keywords: crimp Fabric) CFRP with respect to prepreg, in order to identify ways to improve NCF performance. A. Fabrics/textiles Ó 2009 Elsevier Ltd. All rights reserved. B. Mechanical properties C. Finite Element Analysis (FEA) 1. Introduction microbuckling, forming the basis for a large variety of models introducing the aspects of matrix non-linearity, misalignment, Compared to classical prepreg technology, liquid composite and others. Theories describing compression failure in terms of molding technologies, in combination with non-crimp fabric kink band formation were developed in parallel (as e.g., in (NCF) dry fiber semi-finished products, offer the opportunity of [10,11]).
    [Show full text]
  • How They Work
    GANG-NAIL Truss System TRUSSES - HOW THEY WORK In the evolution of building there have been two great developments since man first used timber or stone to provide himself with shelter. These materials were first used as simple beams. The Romans are credited with the invention of the arch, and the truss was developed in Europe during the middle ages. A beam supports loads due to its bending strength. This is the way simple members such as rafters, battens, purlins, lintels and bressummers work. The top edge of a beam is normally in compression and the bottom edge in tension. These stresses reach a maximum near the middle of the beam’s span and for every doubling of span the strength of the beam must increase four Timber Arch times. Beams also tend to sag when loaded and sag is even more sensitive to increases in span Gang-Nail trusses are based on these simple than the requirement for increased strength. structures. All the truss members are timber, and the joints between the members are formed using The Romans found that if they leant stones Gang-Nail connector plates. against one-another in the shape of an arch, they could span greater distances than by using the stone as simple lintels or beams. In an arch the stones are in compression. The arch will perform as long as the supports or buttresses at each end of the arch provide restraint, and do not spread apart. Timber beams can also be propped against one-another to form arches. The timber members will be in compression and will also act as simple beams.
    [Show full text]
  • Mechanics of Materials Chapter 5 Stresses in Beams
    Mechanics of Materials Chapter 5 Stresses In Beams 5.1 Introduction In previous chapters, the stresses in bars caused by axial loading and torsion. Here consider the third fundamental loading : bending. Make certain simplifying assumptions. the resulting equations have served well in the design of straight, elastic beams 5.2 Bending Stress a. Simplifying assumptions The stresses caused by the bending moment are known as bending stress, or flexure stresses. The relationship between these stresses and the bending moment is called the flexure formula. In deriving the flexure formula, make the following assumptions: The beam has an axial plane of symmetry, which we take to be the xy- Figure 5.1 Symmetrical beam with loads plane (see Fig. 5.1). lying in the plane of symmetry. The applied loads (such as F1,F2 and F3 in Fig.5.1) lie in the plane of the symmetry and are perpendicular to the axis of the beam (the x-axis).The axis of the beam bends but does not stretch ( the axis lies some where in the plane of symmetry; its location will be determined later). Plane sections of the beam remain plane (do not warp ) and perpendicular to the deformed axis of the beam. Change in the cross-sectional dimensions of the beam are Figure 5.1 Symmetrical beam negligible. Because the shear stresses caused by the vertical shear force will distort (warp) an originally plane section, we are limiting our discussion here to the deformations caused by the bending moment alone. the deformations due to the vertical shear force are negligible in the slender beams compared to the deformations caused by bending .
    [Show full text]
  • Columns and Other Compression Members
    Chapter 12 Columns and Other Compression Members 12.1 Columns; Common Case The formulas and discussion of this section are based on the following assumptions: (1) The column is nominally straight and is subjected only to nominally concentric and axial end loads, and such crooked- ness and eccentricity as may occur are accidental and not greater than is consistent with standard methods of fabrication and ordinary conditions of service; (2) the column is homogeneous and of uniform cross section; (3) if the column is made up of several longitudinal elements, these elements are so connected as to act integrally; (4) there are no parts so thin as to fail by local buckling before the column as a whole has developed its full strength. End conditions. The strength of a column is in part dependent on the end conditions, that is, the degree of end fixity or constraint. A column with ends that are supported and fixed, so that there can be neither lateral displacement nor change in slope at either end, is called fixed- ended. A column with ends that are supported against lateral dis- placement but not constrained against change in slope is called round-ended. A column with one end fixed and the other end neither laterally supported nor otherwise constrained is called free-ended. A column with both end surfaces that are flat and normal to the axis and that bear evenly against rigid loading surfaces is called flat-ended. A column with ends that bear against transverse pins is called pin-ended. Truly fixed-ended and truly round-ended columns practically never occur in practice; the actual conditions are almost always interme- diate.
    [Show full text]
  • Uniaxial Tension and Compression Testing of Materials
    Uniaxial Tension and Compression Testing of Materials Nikita Khlystov Daniel Lizardo Keisuke Matsushita Jennie Zheng 3.032 Lab Report September 25, 2013 I. Introduction Understanding material mechanics is critical for engineering. The uniaxial tension and compression tests provide a simple and effective way to characterize a material's response to loading. By subjecting a sample to a controlled tensile or compressive displacement along a single axis, the change in dimensions and resulting load can be recorded to calculate a stress- strain profile. From the obtained curve, elastic and plastic material properties can then be determined. Therefore, to investigate material mechanics and gain experience in uniaxial testing, we performed compressive and tensile tests on alloys, pure metals, and ceramics, and calculated their Young’s modulus, yield stress, ultimate tensile strength, and elastic strain energy density. 1.1 Uniaxial testing For uniaxial tests, the displacement is typically held at a constant rate, and displacement and resulting load are recorded. The load is measured by a series of strain gages, or “load cell,” while the displacement can be recorded as displacement of the crosshead, or the beam on which the specimen load frame is mounted. For more precise load measurements, strain gages or an extensometer can be directly fixed to the specimen. To make direct comparisons between materials, loading responses must be normalized against sample geometry. Therefore, the dimensions of each sample are noted to compute stress and strain from load and displacement, respectively. Engineering strain can be calculated as: εe = ΔL/Lo (1) Where ΔL is the measured displacement and Lo is initial sample length along a single axis.
    [Show full text]
  • Stresses in Beams
    STRESSES IN BEAMS David Roylance Department of Materials Science and Engineering Massachusetts Institute of Technology Cambridge, MA 02139 November 21, 2000 Introduction Understanding of the stresses induced in beams by bending loads took many years to develop. Galileo worked on this problem, but the theory as we use it today is usually credited principally to the great mathematician Leonard Euler (1707–1783). As will be developed below, beams develop normal stresses in the lengthwise direction that vary from a maximum in tension at one surface, to zero at the beam’s midplane, to a maximum in compression at the opposite surface. Shear stresses are also induced, although these are often negligible in comparision with the normal stresses when the length-to-height ratio of the beam is large. The procedures for calculating these stresses for various loading conditions and beam cross-section shapes are perhaps the most important methods to be found in introductory Mechanics of Materials, and will be developed in the sections to follow. This theory requires that the user be able to construct shear and bending moment diagrams for the beam, as developed for instance in Module 12. Normal Stresses A beam subjected to a positive bending moment will tend to develop a concave-upward curva- ture. Intuitively, this means the material near the top of the beam is placed in compression along the x direction, with the lower region in tension. At the transition between the compressive and tensile regions, the stress becomes zero; this is the neutral axis of the beam. If the material tends to fail in tension, like chalk or glass, it will do so by crack initiation and growth from the lower tensile surface.
    [Show full text]
  • Tension and Compression
    Learn Civil Engineering.com/Structure Engineer Section Review/AM Section Mechanics of Materials-Tension and Compression Tension and Compression Forces Two key types of forces involved in building any structure are tension and compression. Every material has the ability to hold up to a certain amount of tension and a certain amount of compression. A tension force is one that pulls materials apart. A compression force is one that squeezes material together. (Body compressed) (Body stretched, tensioned) Some materials are better able to withstand compression, some are better able to resist tension, and others are good to use when both compression and tension are present. For example, if you pull on a strong rope, it can support a large amount of tension. If you push on a rope, it cannot resist compression very well, and just bends. Marshmallows are an example of a material that is easily compressible, but pulls apart under a great amount of tension. From these examples, it is clear that materials may bend or stretch when under a compressive or tensile force. 1 Learn Civil Engineering.com/Structure Engineer Section Review/AM Section Bending Stress When two people sit on a seesaw, is the metal bar between the two seats experiencing compressive or tensile stress? This is a trick question! A "bar in bending" experiences both compressive and tensile stresses! To visualize this, grab a phone book and bend it down (see Figure 1). When you do this, the phone book materials "want" to return to their normal state of rest, so it feels like the top pages try to pull your fingers together because they are in tension and the bottom pages push your fingers apart because they are in compression.
    [Show full text]
  • Chapter 4 – Table of Contents
    Bridge Maintenance Course Series Reference Manual Chapter 4 – Table of Contents Chapter 4 - Bridge Mechanics .................................................................................................... 4-1 4.1 Introduction ........................................................................................................................... 4-1 4.2 Basic Structural Mechanics .................................................................................................... 4-2 4.2.1 Axial Tension ................................................................................................................ 4-2 4.2.2 Axial Compression ....................................................................................................... 4-3 4.2.3 Shear ............................................................................................................................ 4-5 4.2.4 Flexure ......................................................................................................................... 4-6 4.2.5 Torsion ......................................................................................................................... 4-7 4.2.6 Stress............................................................................................................................ 4-8 4.3 Bridge Deck ............................................................................................................................ 4-8 4.3.1 Load Path ....................................................................................................................
    [Show full text]