tailieunhanh - Ebook Masonry design and detailing (5/E): Part 2

Part 2 book "Masonry design and detailing" includes content: Lintels and arches, structural masonry, foundation and retaining walls, masonry paving and fireplaces, installation and workmanship, masonry cleaning and restoration, quality assurance and quality control, specifications and field observation. | 11 LINTELS AND ARCHES There are two ways to span openings in masonry walls. Beams and lintels are horizontal elements which carry loads as flexural members. Masonry arches may be flat or curved but carry loads in compression because of the shape or orientation of the individual units. Large wood or stone lintels were used in ancient Egypt and the Middle East to provide small window and door openings in massive loadbearing masonry walls. The strength of individual stones or timbers however limit- ed the size of such openings. Early corbeled arches were constructed by pro- gressively projecting the masonry units themselves across the top of an open- ing until they met at the apex carrying the load essentially by cantilever action. True compressive arches were developed as early as 1400 . in Babylonia and later perfected by the Romans along with barrel vaults and domes. In more recent history brick arches have been used for long spans with heavy loading as in the railway bridge at Maidenhead England built in 1835 which spans 128 ft with a rise of ft. A railway bridge construct- ed in Baltimore in 1895 spans 130 ft with a rise of 26 ft. This chapter discusses the design of steel concrete and masonry lintels and masonry arches. Structural masonry beams for large openings or heavy loads are discussed in Chapter 12. LINTELS Lintels of steel reinforced masonry stone concrete precast concrete and cast stone and wood are still used today to span small openings in masonry walls. Lintels must resist compressive bending and shear stresses see Fig. 11-1 . Lintels must be analyzed to determine the actual loads which must be carried and the resulting stresses which will be created in the member. Many of the cracks that appear over door and window openings result from excessive deflection of lintels which have been improperly or inadequately designed. Load Determination Regardless of the material used to form or fabricate a lintel one of the most important .