Chapter I: Preface

In offering this little book to the reader interested in Bridgework, the author desires to express his acknowledgments to the proprietors of “Engineering,” in which journal the papers first appeared, for their courtesy in facilitating the production in book form.

It may possibly happen that the scanning of these pages will induce others to observe and collect information extending our knowledge of this subject--information which, while familiar to maintenance engineers of experience, has not been so readily available as is desirable.

No theory which fails to stand the test of practical working can maintain its claims to regard; the study of the behaviour of old work has, therefore, a high educational value, and tends to the occasional correction of views which might otherwise be complacently retained.

60 WINSHAM STREET,
CLAPHAM COMMON, LONDON, S.W.
_October_, 1906.

CONTENTS

CHAPTER I.

INTRODUCTION--GIRDER BEARINGS.

PAGE

Pressure distribution--Square and skew bearings--Fixed bearings--
Knuckles--Rollers--Yield of supports 1

CHAPTER II.

MAIN GIRDERS.

_Plate webs_: Improper loading of flanges--Twisting of girders--
Remedial measures--Cracks in webs--Stiffening of webs--[T]
stiffeners 9

_Open webs_: Common faults--Top booms--Buckling of bottom booms--
Counterbracing--Flat members 17

CHAPTER III.

BRIDGE FLOORS.

Liability to defects--Impact--Ends of cross and longitudinal
girders--Awkward riveting--Fixed ends to cross girders--Plated
floor--Liberal depths desirable--Type connections--Effect of “skew”
on floor--Water-tightness--Drainage--Timber floors--Jack arches--
Corrugated sheeting--Ballast--Rail joints--Effect of main girders
on floors 20

CHAPTER IV.

BRACING.

Effect of bracing on girders--Influence of skew on bracing--Flat
bars--Overhead girders--Main girders stiffened from floor--
Stiffening of light girders--Incomplete bracing--Tall piers--Sea
piers 34

CHAPTER V.

RIVETED CONNECTIONS.

Latitude in practice--Laboratory experiments--Care in considering
practical instances--Main girder web rivets--Lattice girders
investigated--Rivets in small girders--Faulty bridge floor--
Stresses in rivets--Cross girder connections--Tension in rivets--
Defective rivets--Loose rivets--Table of actual rivet stresses--
Bearing pressure--Permissible stresses--Proposed table--Immunity of
road bridges from loose rivets--Rivet spacing 45

CHAPTER VI.

HIGH STRESS.

Elastic limit--Care in calculation--Impact--Examples of high stress
--Early examples of high stress in steel girders--Tabulated
examples--General remarks 61

CHAPTER VII.

DEFORMATIONS.

Various kinds--Flexing of girder flanges--Examples--Settlement
deformations--Creeping--Temperature changes--Local distortions--
Imperfect workmanship--Deformation of cast-iron arches 73

CHAPTER VIII.

DEFLECTIONS.

Differences as between new work and old--Influence of booms and web
structure on deflection--Yield of rivets and stiffness of
connections--Working formulæ--Set--Effect of floor system--
Deflection diagrams--Loads quickly applied--“Drop” loads--Flexible
girders--Measuring deflections--New method of observing deflections
--Effect of running load 85

CHAPTER IX.

DECAY AND PAINTING.

Examples of rusting of wrought-iron girders--Girder over sea-water
--Rate of rusting--Steelwork--Precautions--Red-lead--Repainting--
Scraping--Girders built into masonry--Cast iron--Effect of sea-
water on cast iron--Examples--Tabulated observations--Percentage of
submersion--Quality of metal 96

CHAPTER X.

EXAMINATION, REPAIR, AND STRENGTHENING OF RIVETED BRIDGES.

Purpose--Methods of examination--Calculations--Stress in old work--
Methods of reducing stress--Repair--Loose rivets--Replacing wasted
flange plates--Adding new to old sections--Principles governing
additions--Example--Strengthening lattice girder bracings--Bracing
between girders--Strengthening floors--Distributing girders 107

CHAPTER XI.

STRENGTHENING OF RIVETED BRIDGES BY CENTRE GIRDERS.

Principal methods in use--Method of calculation--Adjustments--
Connections--Method of execution--Checks--Effect of skew on method
considered--Results of calculation for a typical case--Probable
error--Practical examples--Special case--Method of determining
flexure curves 122

CHAPTER XII.

CAST-IRON BRIDGES.

Limitations of cast iron--Stress examples--Advantages and
disadvantages--Foundry stresses--Examples--Want of ductility of
cast iron--Repairs--Restricted possibilities 141

CHAPTER XIII.

TIMBER BRIDGES.

Perishable nature--Causes of decay--Sag--Lateral bracing--Piles--
Uncertainty respecting decay--Examples--Conditions and practice
favourable to durability--Bracing--Protection--Repair--Piles--Cost 149

CHAPTER XIV.

MASONRY BRIDGES.

Definition--Cause of defects or failure--Spreading of abutments--
Closing in--Example--Stop piers--Example of failure--Strength of
rubble arch--Equilibrium of arches--Effect of vibration on masonry
--Safety centring--Methods of repair--Pointing--Rough dressed
stonework 157

CHAPTER XV.

LIFE OF BRIDGES--RELATIVE MERITS.

Previous history--Causes of limited life--Tabulated examples of
short-lived metallic bridges--Timber and masonry bridges--
Durability--Maintenance charges--First cost--Comparative merits--
Choice of material 165

CHAPTER XVI.

RECONSTRUCTION AND WIDENING OF BRIDGES.

CONCLUSION.

Measuring up--Railway under-bridges--Methods of reconstruction in
common use--Reconstruction of bridges of many openings--Timber
staging--Traffic arrangements--Sunday work--Railway over-bridges--
Widenings--Junction of new and old work--Concluding remarks--Study
of old bridgework 172

INDEX 187

THE
ANATOMY OF BRIDGEWORK.