دانلود رایگان مقاله ترکیب طراحی کامپوزیت فولاد نورد گرم و فولاد و بتن و سخت شدن کرنش

Abstract

Current design codes for steel and steel-concrete composite structures are based on elastic, perfectly plastic material behaviour and can lead to overly conservative strength predictions due to the neglect of the beneficial influence of strain hardening, particularly in the case of stocky, bare steel cross-sections and composite beams under sagging bending moments. The Continuous Strength Method (CSM) is a deformation based design method that enables material strain hardening properties to be exploited, thus resulting in more accurate capacity predictions. In this paper, a strain hardening material model, which can closely represent the stress-strain response of hot-rolled steel, is introduced and incorporated into the CSM design framework. The CSM cross-section resistance functions, incorporating strain hardening, are derived for hot-rolled steel sections in compression and bending, as well as hot-rolled steel-concrete composite sections where their neutral axes lie within the concrete slab in bending. Comparisons of the capacity predictions with a range of experimental data from the literature and finite element data generated herein demonstrate the applicability and benefits of the proposed approach.

4. Conclusions

Developments to the Continuous Strength Method (CSM) for hotrolled carbon steel, covering recent refinements, have been described. A quad-linear material model, enabling representation of both the yield plateau and strain hardening, has been proposed and used for the derivation of CSM resistance equations for the compression and bending of hot-rolled carbon steel members. Test data on hot-rolled carbon steel stub columns and beams were used to make comparisons with the CSM and EN 1993-1-1 design provisions. It was shown that the CSM offers improved mean resistance predictions and lower scatter compared with EN 1993-1-1. The method was then extended to composite beams under sagging bending moment, where the influence of strain hardening has been found previously to be significant. For composite beams with full shear connection, a new analytical model has been developed accounting for strain hardening through the proposed material model, and explicit resistance functions have been derived. Comparison of the predictions with 14 test results on composite beams from the literature showed that the proposed analytical equations may be more accurate than the current codified approaches. A two-dimensional FE model was then developed and validated against test results reported in existing studies. Based on subsequently generated numerical parametric results, a new design approach was outlined for composite beams with partial shear connection. Additional analyses considering various geometric properties and different reinforcement ratios for composite beams are needed to confirm the wider applicability of the proposed design method to steel-concrete composite beams.