Curved bridges live load bending moment distribution using straight and curved girders

abstract: The present study focuses on comparative parametric analysis of curved precast concrete bridges using straight and curved I-girders. The live load bending moment distribution for girders was studied using the bridge curvature and its relationship with the results obtained for a straight bridge. FEM 3D models were developed with restrictions on the transverse live load positions and with two different load models types: HL-93 (AASHTO) and TB-450 (NBR 7188, 2013). The parametric analysis results were calculated using the Modification Factor (MF) and the Bending Moment Distribution Factor (BMDF), calculated from the structural analysis of each model at the midspan. Globally, an increase was found in the total bending moment for the curved bridge models in relation to the straight bridge. In the examples herein studied, the larger the bending radius, the larger the maximal bending moment in the bridge center. For the external girders, the MF increases with the increase of the L/R. For the internal ones, the MF decreases with the increase of the L/R. In addition, the occurrence of “Load Shift” was different from the rigid body behavior, for there was demonstrated a different bending moment variation between external girder (G1) in relation to its adjacent (G2). Therefore, the structural behavior of straight (SG) and curved girders (CG) was analyzed, revealing that, in the SG, a significant gap occurred in the BMDF between G1 and G2 girders for all curvatures. For L/R = 0.6, it caused a difference of 17.8% in the BMDF between the G1 and G2 girders, while on the curved girders, a difference of only 6.6% was found.

Finite Element Analysis of Glass Fiber-Reinforced Polymer-(GFRP) Reinforced Continuous Concrete Beams

Fiber-reinforced concrete (FRC) is a competitive solution for the durability of reinforced structures. This paper aims to observe the moment redistribution behavior occurring due to flexural and shear loading in Glass Fiber-Reinforced Polymer- (GFRP) reinforced continuous concrete beams. A rectangular cross-section was adopted in this study with dimensions of 200 mm in width and 300 mm in depth with a constant shear span-to-depth ratio of 3. The reinforcement ratio for the top and bottom were equal at sagging and hogging moment regions. A finite element model was created using Analysis System (ANSYS) and validated with the existing experimental results in the literature review. Based on the literature review, the parametric study was conducted on twelve beam specimens to evaluate the influence of concrete compressive strength, transversal GFRP stirrups ratio, and longitudinal reinforcement ratio on the redistribution of the moment in beams. Several codes and guidelines adopted different analytical models. The Canadian Standards Association (CSA) S806 adopted the modified compression field theory in predicting the shear capacity of the simply supported beams. Recently, various researchers encountered several factors and modifications to account for concrete contribution, longitudinal, and transverse reinforcement. A comparison between the predicting shear capacity of the generated finite element model, the analytical model, and the existing data from the literature was performed. The generated finite element model showed a good agreement with the experimental results, while the beam specimens failed in shear after undergoing significant moment redistribution from hogging to sagging moment region. The moment distribution observed about 21.5% from FEM of beam specimen GN-1.2-0.48-d, while the experimental results achieved 24% at failure load. For high strength concrete presented in beam specimen GH-1.2-0.63-d, the result showed about 20.2% moment distribution, compared to that achieved experimentally of 23% at failure load.

Finite Element Analysis of Overlapped Z-Purlins Restrained by Sheeting

Cold-formed steel Z-purlins with overlapping at the intermediate supports ensures the continuity of the bending moment. A continuous beam with two equal spans of 6 m is investigated under gravity loading using the finite element method. The numerical model includes the beneficial interaction between the Z-purlins and the trapezoidal sheeting. Finite element results show that the screw spacing and sheeting thickness has a limited influence on the resistance of the member. The effect of the overlapping length and detailing of the connection is studied through a parametric study. Six overlaps varying from 100mm to 1200mm (1.6% to 20% of one span) capture the change of the failure mode from the overlap edge to the support region of the purlin. The connection detailing is studied considering multiple bolt/screw patterns. The detailing and length of the overlap connection has a major influence on the moment distribution and consequently on the failure mode. The detailed finite element analysis shows that assuming the beam connection as continuous in 1D beam models lead to an unrealistic bending moment distribution and failure mode. Connecting the bottom flange using screws improves the overall load carrying capacity of the beam especially for short overlap lengths. The increase in resistance is attributed to the restraining effect on the free flange which fails due to distortional buckling.

A Study of Support Characteristics of Collaborative Reinforce System of U-Steel Support and Anchored Cable for Roadway under High Dynamic Stress

This paper presents a comprehensive study of the support effect and characteristics of a collaborative reinforce system of U-steel support and anchored cable (USS-AC) for roadway under high dynamic stress in a coal mine in China. The deformational behavior of the roadway and the load characteristics of reinforcing elements were measured in real time and analyzed. A numerical simulation study has also been conducted to identify the interaction of the reinforcing elements to the surrounding rock under dynamic load. The research results suggest that the stress distribution of roadway surrounding rock could be changed and that residual strength of the surrounding rock near opening could be increased by using USS-AC. Based on the action of anchored cable, the moment distribution of U-steel support is optimized. The load capacity and nondeformability of the U-steel support are promoted. And the global stability of U-steel support is enhanced so as to achieve the goal of high supporting resistance. When the deformation stress of the surrounding rock is higher, the U-steel support deforms as the surrounding rock. The two side beams and the overlapping parts of U-steel support suffer the highest deformation stress. As a result, the anchored cable provides higher reaction force for the previous locations of the U-steel support in order to prevent deformation of support towards to excavation. As an integral structure, the U-steel support is confined to a limited deformation space under the action of anchored cable. The larger deformation is released through sliding motion of the overlapping parts so as to reach the ultimate of high supporting resistance of USS-AC.

A New Macromodel of Beam-Column Joints for Progressive Collapse Analysis of Reinforced Concrete Structures Under Blast Loading

The macromodel, by which the beam and column are simulated by fiber beam elements, has been extensively used in the progressive collapse analysis of reinforced concrete (RC) frames due to its high computing efficiency as compared to the solid element model. However, there exist some problems that need to be solved to improve the accuracy of the macromodel. One typical issue is to develop an accurate beam-column joint model. In current practice, the beam-column joint is as part of the rectangular frame with rigid elements, neglecting the shear damage and bending moment distribution in the core region of the joint, although they are crucial to progressive collapse analysis. In this paper, a new macromodel that considers the shear damage and bending moment distribution in the core region of the beam-column joint is developed for the progressive collapse analysis of RC frame structures under blast loads. Nonlinear springs are used in the joint connection interfaces to consider the force transfers from the beams or columns to the joint. Also, nonlinear shear springs are used in the core region of the joint, whose characteristics are derived based on the actual force-deformation relationship of the sub-assemblage due to joint shear distortion, to model the shear damage of the joint under blast loading. The proposed beam-column joint macromodel is validated with the available test data in the literature. The results indicated that the proposed macromodel for beam-column joints is more accurate than the traditional beam-column joint macromodel, while the computing efficiency remains almost unchanged in progressive collapse analysis of RC structures, especially when the RC frame structures are seriously damaged or collapse under blast loadings.

Model Test Study on Bearing Capacity and Deformation Characteristics of Symmetric Pile–Bucket Foundation Subjected to Cyclic Horizontal Load

The pile–bucket foundation that features a bucket slipped onto a monopile is a new type of symmetric offshore foundation supporting the wind turbine. Its load bearing and deformation resistance capacity are unclear, especially when subjected to cyclic horizontal loadings. In this paper, a model test has been designed and carried out for investigating the cyclic behavior of the pile–bucket foundation embedded in soft marine clay. Cyclic horizontal loads are applied in a displacement-controlled manner with different amplitudes and frequencies. The influences of cyclic loading parameters, including the amplitude, the frequency and the cycle number, have been studied from the perspectives of stiffness-degradation and damping effect that are evaluated from the recorded horizontal force–displacement relationships at the loading point. In addition, the influences of cyclic horizontal loading on the bending moment distribution and on the p–y curve have been presented and discussed. The results show that significant reductions in the foundation stiffness and in the soil resistance may be observed during the first few cycles when the loading displacement is relatively high.