CHAPTER IX. 103. Lateral Wind Pressure on Trusses 122 104. Upper and Lower Lateral Bracing 124 105. Bridge Plans and Shopwork 125 106. Erection of Bridges 126 107. Statically Determinate Trusses 126 108. Continuous Beams and Trusses—Theorem of Three Moments 128 109. Application to Draw- or Swing-bridges 130 110. Special Method for Deflection of Trusses 130 111. Application of Method for Deflection of Triangular Frame 133 112. Application of Method for Deflection to Truss 134 113. Method of Least Work 137 114. Application of Method of Least Work to General Problem 138 115. Application of Method of Least Work to Trussed Beam 139 116. Removal of Indetermination by Methods of Least Work and Deflection 141 CHAPTER X. 117. The Arched Rib, of both Steel and Masonry 142 118. Arched Rib with Ends Fixed 144 119. Arched Rib with Ends Jointed 144 120. Arched Rib with Crown and Ends Jointed 145 121. Relative Stiffness of Arched Ribs 145 122. General Conditions of Analysis of Arched Ribs 146 CHAPTER XI. 123. Beams of Combined Steel and Concrete 149 CHAPTER XII. 124. The Masonry Arch 154 125. Old and New Theories of the Arch 155 126. Stress Conditions in the Arch-ring 158 127. Applications to an Actual Arch 158 128. Intensities of Pressure in the Arch-ring 162 129. Permissible Working Pressures 163 130. Largest Arch Spans 163