A Survey of Steel Arch Bridges in China

A review of the current status and progress of steel arch bridges in China is presented in this paper. The existing steel arch bridges in China were analyzed in terms of steel material, span, structure type, main arch rib form and construction method. The comparison with CFST arch bridges and RC arch bridges is also conducted. It is shown that steel arch bridge has gain rapid development in China since 2000, characterized by long main spans. As for the span, most of the steel arch bridges have a span less than 250 m, while when the span exceeds 350 m, steel arch bridges are strongly competitive against CFST or RC arch bridges. Over 80% of the bridges are through and half-through bridge types, and the arch ribs are hingeless structures. The rise-to-span ratios of the arches are mainly between 1：4 and 1： 5. Most of the arches use solid box ribs, and a small portion of arches use truss ribs in which box sections are mostly adopted for the truss members. The cantilever method and scaffolding method are the two main construction methods used, but some other construction methods have also been developed.

A New Method for Predicting the UL of Circular CFST Columns

Concrete filled steel tube structures have gained booming development in recent decades, especially in China. Simplified methods have been proposed in design codes, such as the Eurocode 4 (EC4) and the China engineering and construction specification (CECS). In EC4, the confinement effect is reasonably related to slenderness and load eccentricity. The CECS method is much straight forward in that the slenderness ratio and load eccentricity are treated as independent reduction factors. To make use of the advantages of both the CECS and the EC4 methods, the CECS method is modified to consider the confinement effect associated with slenderness and load eccentricity. It is shown that the proposed method can predict well the ultimate load capacity of circular section concrete filled steel tube columns.

Effects of fibers on the mechanical properties of UHPC:A review

Ultra-high performance concrete(UHPC) developed rapidly in research and commercial use during the recent decade. Significant progress has been achieved in its material science and technology, including why and how to add discontinuous fiber reinforcement in it.This paper reviews the researches on understanding the effects of various fibers on the mechanical properties of UHPC, focus on the straight steel fibers but involving also deformed steel fibers, non-steel fibers as well as hybrid fibers. It also discusses the research methodology, prediction of mechanical properties by fiber factors, and the classification of UHPC mechanical properties related to this topic. It shows that(1) the experimental research is the main methodology for investigating the effect of the fibers on the mechanical properties of UHPC;the tensile performance of UHPC should be studied by uniaxial tensile tests and its representative indicators should include tensile strength, initial cracking strength, and peak tensile strain;(2) fiber plays an essential role in the reinforcement of the tensile strength, compressive strength, modulus of elasticity, and other material properties of UHPC, but in weakening the flowability of fresh UHPC. The positive and negative effects of fibers on the mechanical properties of UHPC should be considered,and the technology should be developed to maintain the flowability when high volume fraction of fibers is added in the UHPC;(3) the parameters of steel fibers affecting the mechanical properties of UHPC include volume fraction, size, shape, orientation and distribution, average bonding strength and minimum tensile strength, etc., which are mainly studied independently in the existing research. The studies on the combined effect of these parameters are limited but worthy of further investigation;(4) hybrid fibers could efficiently produce reinforcement effects for UHPC. It has great practical and research significance to conduct in-depth studies though the theoretical analysis and quantitative prediction are complex.

Design and field tests of a deck-extension bridge with small box girder

A jointless bridge could fundamentally eliminate vulnerable deck joints, thereby meeting the need for sustainable development of bridges, especially for an expressway with highspeed traffic. In this paper, one jointless bridge(deck-extension bridge) with a small box girder in an expressway was chosen as a case study to examine the structural design,construction and field test. The field tests of the bridge indicated that the designed and constructed structures can satisfy the requirement for service performance of the deckextension bridge. Some key technologies, such as the position of longitudinal reinforcements in the superstructure-approach slab connections and the arrangement of the sliding material layers, were introduced. The longitudinal thermal movement of the superstructure in the deck-extension bridge with a small box girder could be predicted accurately by using the average temperature of the cross section of a small box girder. The finite element model, built by using the MIDAS program, was used to analyze the temperature distribution on the cross section of a small box girder, the accuracy of which could be verified by comparing with the measured values. The maximum longitudinal thermal movement of the superstructure in deck-extension bridges with a small box girder under historically extreme temperature conditions was predicted.

Trial design of arch bridge of composite box section with steel web-concrete flange

The concrete arch bridge is a natural and appropriate structural solution,aesthetically pleasing and easily integrated into the environment,especially in mountainous and island areas.However,construction difficulty and cost will increase with heavy self-weight when the span enlarges.A potential solution is to use a composite box arch ring with steel web-concrete flange.Taking Wanzhou Yangtze River Bridge(the longest concrete arch bridge in the world with a main span of 420 m)as a prototype,trial designs of a composite box arch with steel webs(including corrugated steel webs and plain steel webs)and concrete flanges were carried out.Comparison of quantities and structural behaviors of the prototype concrete arch with the two trial designed composite arch was presented.It is shown that the selfweight of the composite arch can reduce about 28%and the structures can meet the design requirements,therefore it is possible to use the two composite arches in long span arch bridges.