Pendekatan teoritis dengan prosedur analitis dan numerik untuk penentuan perpindahan awal dari komponen struktur beton bertulang dan prategang, balok sederhana dan kantilever, dibebani oleh gaya aksial dan momen lentur diusulkan. Ini didasarkan pada prinsip energi potensial Beton Bertulang minimum dengan kesetaraan kekuatan internal dan eksternal. Persamaan untuk energi internal regangan telah diturunkan, termasuk beton dan tulangan tekan dan tarik. Persamaan energi gaya eksternal dengan efek perpindahan lentur aksial telah diturunkan dari kurva sinusoidal yang diasumsikan. Aturan trapesium diterapkan untuk mengintegrasikan energi regangan segmen. Metode yang diusulkan menggunakan kurva tegangan-regangan non-linier untuk beton dan hubungan elastik-plastik bilinear untuk tulangan; kondisi kesetimbangan pada tingkat penampang untuk menghasilkan energi regangan sepanjang balok. Pada akhir artikel ini ditampilkan tiga contoh numerik spesifik dengan hasil komparatif, eksperimental (dua tes) dengan sangat setuju dan satu hasil perhitungan dengan sangat tidak setuju, dengan memperoleh hasil metode prinsip virtual. Dengan metode ini adalah menghindari adopsi suatu ketidakpastian (EJ), seperti dalam kasus meremehkan atau melebih-lebihkan kekakuan lentur awal.

The mechanics of continuous environments in dealing with the stress and strain distribution under the influence of external forces start from the assumption that the substance is continuous and therefore deformations are treated as continuous transformations of the space in which the stressed body exists.

Some changes occur immediately after a change in stress condition and thus are called initial deformations. The equilibrium process of deformation of elastic bodies under linear interconnection between stress and deformation is the subject of the study of classical elastic theory and falls into reversible processes. A more complete theoretical treatment of the occurrence of increasing material deformation was carried out by the Austrian physicist L. Boltzman, who formulated a theory of subsequent elastic action and laid foundations for a linear theory of flow. The deflection [1] (Branson, D.F. and Shaikh, A.F., 1985) of the prestressed concrete beams is calculated with simple equations by modifying some of the existing methods. The comparison between the experimental and theoretical results shows good agreement. Many reinforced and prestressed concrete bridges throughout the world are either deteriorated or distressed to such a degree that structural strengthening of the bridge or reducing the allowable is necessary to extend the service life of the bridge.

While several methods are available in the literature for evaluation of deflections, this chapter concentrates on the effective moment of inertia method in [2] Building Code Requirements for Reinforced Concrete (ACI 318) and modifications introduced by ACI Committee. These reports include [3] ACI 435.2R, “Deflection of Reinforced Concrete Flexural Members”, and [4] ACI 435.1R, “Deflection of Prestressed Concrete Members”. The report replaces several reports of this committee (ACI 318) in order to reflect the more recent state of the art in design. The recommendations of current codes show that most of them underestimate or overestimate the initial flexural rigidity.