Design of Masonry Structures
Design of Masonry StructuresA.W. Hendry, B.P. Sinha and S.R. DaviesE& FH SponLondon1997xiii + 271 pp.Keywords Buildings, Design,Structural defects
The comment made when this book was handed over with a request for review that it is more for structural engineers than for structural surveyors is only partially true. Design of Masonry Structures, which the title page tells us is the third edition of Load Bearing Brickwork Design, is a sandwich. The meat in the middle dealing with the numerical aspects of the design of masonry structures is very much for structural engineers, but surveyors could benefit from studying the bread at the beginning and the end setting out the properties and characteristics of the individual materials and their consideration in walling.
The three authors are in the Department of Civil Engineering at the University of Edinburgh, where their experimental and theoretical work on masonry has contributed in no small measure to the design methods set out in parts 1 and 2 of BS 5628 the UK Code of Practice for Use of Masonry, and in the equivalent European document EC6(ENV 1996-1-1, 1995). It is therefore not surprising to find that the book provides an introduction to and a commentary on those codes which all practising structural engineers will find invaluable. The inclusion of worked examples of the design of plain, reinforced and prestressed masonry, and of a seven storey dormitory building make the explanations easier to understand. It is particularly useful to have explanations for and examples of clauses relating to resistance to horizontal forces, such as wind, and of the accidental collapse clauses included in all codes following the Roman Point collapse.
The first three chapters cover the advantages and development of loadbearing masonry, and properties and characteristics of the materials, with particularly interesting paragraphs covering the effects of workmanship on strength which can result in a wall being only half as strong in compression as it should be, but with the consoling conclusion that "such a wall, however, would be obviously badly built and would be so far outside any reasonable specification as to be quite unacceptable". It is useful to have gathered together in one place an idea of the potential percentage effects on compressive strength of failure to fill bed joints, bed joints of excessive thickness, deviation from plumb, adverse weather when green,failure to adjust suction and incorrect preparations of mortar.
The chapter at the end on movements, which the preface tells us is new to this edition would benefit from proof reading, for instance to correct the minus sign which tells us that clay brickwork has an irreversible moisture shrinkage of 0.7 per cent (nearly twice as much as calcium silicate brickwork!) (readers will all know that it is this irreversible moisture expansion of clay brickwork which causes a substantial proportion of the cracking we are called to look at in recent buildings). The calculations of the amount of movement to be expected in this chapter would be easier to understand if the materials being considered were clearly described. It is nevertheless useful to have these simplified calculations as a reference. Cracking and distortion seen in new buildings demonstrate that many buildings designers would find the amount of relative movement of different materials surprising.
A place should be found for this book on the shelves of practising structural engineers, and structural surveyors would benefit from a study of the descriptive chapters at the beginning and end.
Lawrie Hurst
