Compared with simply supported beams, continuous steel-concrete composite beams have many advantages such as higher span/depth ratio, less deflection, and higher fundamental frequency of vibration due to its higher stiffness. However, in negative bending regions near interior supports, tension in concrete is unfavorable and a complicated issue, which deserves a special study. In this paper, a mechanics model based on elastic theory was established to investigate the stiffness of composite beams in negative bending regions by considering slips at the steel beam-concrete slab interface and concrete-reinforcement interface. In order to validate this approach, a test of three composite beams with profiled sheeting under negative bending was conducted. Meanwhile, a three-dimensional nonlinear finite element (FE) analysis was conducted to investigate the general behavior of the tested specimens. In addition, a comparative analysis between results derived from the analytical model, laboratory test, and FE analysis was performed. The results show that slip always exists for composite beams under negative bending even with complete shear connection (full composite action) between the steel and concrete components. The slip effect results in an additional curvature of beam bending and reduces the section stiffness by 10-20% compared with that of a beam without any slip in serviceability condition. This reduction should be considered in designing process especially for cantilever beams. Formulae under other loading cases and boundary conditions were also proposed. The results can serve as a basis for further study on stiffness of continuous steel-concrete composite beams and can directly be used for the deflection calculation of cantilever beams.

The present study investigated the effects of shear slip on the deformation of steel-concrete composite beams. The equivalent rigidity of composite beams considering three different loading types was first derived based on equilibrium and curvature compatibility, from which a general formula to account for slip effects was then developed. The predicted results were compared with measurements of six specimens tested in the present study and other available test results for both simply supported and continuous beams. It was found that including slip effects has significantly improved the accuracy of prediction. For typical beams used in practice, shear slip in partial composite beams has a significant contribution to beam deformation. Even for full composite beams, slip effects may result in stiffness reduction up to 17% for short span beams. However, slip effects are ignored in many design specifications that use transformed section method except that American Institute of Steel Construction (AISC) specifications recommend a calculation procedure in the commentary. In the AISC procedure, stress and deflection calculations of partially composite girders are based on effective section modulus and moment of inertia to account for slip, while ignoring slip effects in full composite sections. For full composite sections, the effective section modulus and moment of inertia calculated with the AISC specifications are larger than that of present study, meaning that the specifications are not on the conservative side. For partial composite sections, the AISC predictions are more conservative than the present study.

This paper describes an experimental study on behavior of steel and high-strengrth concrete (HSC) composite beams. Seven model HSC composite beams and one normal. strength concrete (NSC) beam were tested under monotonic loading. All beams were designed for a full shear connection between the steel beam and the concrete flange USing shear studs. It was identified that the HSC composite beams had higher initial stiffness and very distinct post. yielding characteristics compared wim the NSC beam. Test results of the HSC specimens also showed several favorabte design aspects such as a larger margin beyond the steel yielding and greater ultimate deformability. Analysis based on the current design codes can providea reasonable estimation to the flerural bzitial stiffness andul timate flexural capaci of the HSC composite beams.

An analytical model that incorporates time-dependent effects (creep and shrinkage) was developed to predict the long-term deflection of cracked reinforced concrete beams under sustained loading. The deflection model includes both bending and shear effects. Correspondingly, experimental studies were conducted to verify the analytical model. Eight specimens were precracked with a diagonal crack width of 0.2-0.3mm and tested under sustained loading for three months. It was found that the contribution of shear effect to long-term deflection is significant. The predicted deflections including both bending and shear deformations agree very well with experimental measurements. In addition, formulas for calculating creep coefficients from strain increments were derived that provide an approach to calibrating the code specifications. The effects of different creep coefficients on the prediction of time-dependent deformations were discussed.

有端横梁约束的简支单向组合梁-板体系在横向荷载作用下，由于剪力连接件的约束，翼缘板中存在剪力滞后现象。结构体系中，端横梁对剪力滞后程度有很大影响。本文采用有限元方法，对翼缘有效宽度的主要影响因素进行参数分析，其中包括宽跨比、荷载类型、滑移刚度、端横梁约束程度等，并拟合出了各种情况下有效宽度的简化计算公式，通过与有限元方法及其它计算方法的对比，说明了本文公式的准确性。