土木工程毕业设计外文翻译原文

EngineeringStructures, Vol.

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0141-0296(95)00038-0

18, No. 4, pp. 311-320, 1996 Copyright© 1996 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0141~)296/96$15.00+ 0.00

Cyclic load tests on prestressed concrete m o d e l flames Y. L. Mo and R. H. Han Department of Civil Engineering, National Cheng Kung University, Tainan 701, Taiwan (Received September 1994; revised version accepted December 1994)

Prestressed concrete frames are commonly used in bridge design. However, very little is known about their behaviour under reversed cyclic loads, particularly when subjected to severe earthquakes, and most bridge codes do not provide the required design guidelines. Results from small-scale models of eight prestressed concrete frames, tested under various load histories simulating earthquake forces are presented. The experimental primary curves (horizontal force-displacement relationships) are compared with the theoretical results, and the experimental hysteretic loops are compared with those calculated from Tadeka's rules. The concrete strength is approximately 40 MPa, and the effective prestress varied between 36% and 51% of the ultimate strength of the prestressing steel. It was found that the ductility and energy dissipation increased with decreasing effective prestress. The effect of the load history on the reversed cyclic behaviour is also significant.

Keywords: prestressed concrete frames, bridge design, cyclic load testing

1.

Introduction

The rigid frame bridge is one of the most widely used highway bridges worldwide I. Engineers treat the super- and substructures as one unit by constructing a continuous prestressed concrete rigid frame with supporting legs. This type of construction does not need concrete piers and positions the supports away from the lower roadway, thus giving a more economical structure. Generally, this type of bridge can reduce the depth of the main girder and save materials in the superstructure. In seismic regions the investigation of the response of the prestressed concrete frame bridges to cyclic loads is very important and practically significant. Unfortunately, most previous research work on prestressed concrete bridges concentrated on the inelastic static behaviour~-7. On the other hand, it is generally known that prestressed concrete displays more brittle behaviour than reinforced concrete. For use in earthquake-resistant structures and to take advantage of economic savings through prestress, it is imperative that the various structural components behave in a ductile manner. Depending on the state of stress at a particular section, the concrete may also be required to display large ductility and energy-absorption capacity. Results from several experimental studies have been reported 8-13 dealing with reinforced concrete structures subjected to reversed cyclic loads. Data from tests on prestressed concrete structures are, however, very limited 14, particularly

under different reve

rsed cyclic load histories. Since the dissipation of seismic energy through the inelastic behaviour of flexural members is preferable, hinging of beams or columns during a severe earthquake may be expected in many cases. Appropriate detailing of critical regions in beams or columns is therefore needed to prevent brittle structural failure. To apply the reversed cyclic load test data for practical seismic design of prestressed concrete frames, it is necessary to study the effect of various cyclic load histories. This paper presents a series of reversed cyclic load test results from small-scale models of eight prestressed concrete frames and examines the effects of prestress and reversed cyclic load history on prestressed concrete frames.

2.

Test programme

The frames were divided into two groups. The tests study the effects of the effective prestress and the reversed cyclic load history on the behaviour of the prestressed concrete frames.

2.1.

Concrete

The target compressive strength for the ready-mix concrete was 5000 psi (35 MPa) in all the specimens. 24 standard cylinders were cast with each pour and tested frequently to

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