In this paper, an experimental and analytical investigation of concrete-filled steel tubular (CFST) laced columns is presented. These columns consist of four concrete-filled steel tubes that are laced together. A total of 27 experimental tests were conducted to quantify the column failure mechanism at ultimate loads. The experiments were designed to obtain the load-deflection curves. These curves were subsequently used to quantify the structural behavior for each element of the hybrid column. Experimental results indicate that the compression force in the longitudinal members dominated the failure mechanism in the CFST columns. In-plane bending occurred when member segments reached the compression failure load. The forces in the lacing members (diagonal and horizontal bracing) were found to be small and remained in the elastic range through failure. The experimental study was used to validate an analytical parametric study. The analytical study showed that increasing slenderness ratios and eccentricities ...

Concrete-filled steel tube (CFT)–RC composite members consist of multiple CFT columns connected by RC plates or webs. CFT-RC composite members have been used in different types of structures, for example, as ribs in long-span arch bridges and as tall piers supporting long-span bridges. However, there is limited knowledge regarding their fundamental axial load-displacement behavior, and a general lack of behavior-based design equations for estimating their axial compressive strength. This paper addresses these knowledge gaps by presenting experimental results from axial loading tests conducted on 14 short (stub) column specimens. These include seven CFT-RC columns, four CFT columns, and three RC plates. The parameters included in the tests are the thickness of the steel tube wall ($t_s$ ) and RC plates ($t_p$ ). An experimental database of 104 CFT column tests conducted around the world is also compiled. The experimental results from the tests conducted in this research are combined with those from the compiled database and used together to develop behavior-based design equations for estimating the axial compressive strength of short CFT-RC columns.

Several concrete-filled steel tube (CFT) arch bridges have been built over the past few years around the world. Current design codes do not address the design of CFT arch bridges, particularly with consideration of concrete creep effects, which can be very important. This paper presents experimental results from tests conducted on 13 specimens to evaluate the creep behavior of CFT members. An experimental database was compiled using results from this paper and 35 additional tests from the literature. The comprehensive database was used to evaluate four commonly used creep models for predicting short-term (up to 730 days) creep strains of the concrete infill in CFT members. The selected models are the Comité Euro International du Béton–Fédération Internationale de la Précontrainte (CEB-FIP) MC90 model, fédération internationale du béton (fib) MC2010 model, American Concrete Institute (ACI) 209 R-92 model, and the B4 model. The evaluations indicate that the prediction quality varies by cases. Therefore, it is not possible to recommend a most-suitable model based on this study. Further investigations are required to evaluate the effects of factors such as the steel ratio. To evaluate the effects of creep on the time-dependent behavior of CFT arch bridges, creep analyses on 11 such bridges were conducted with the implemented ACI 209 R-92 creep model. Analytical results indicate that creep results in increases in the steel tube stresses and bridge deflections and relaxation of concrete stresses.

Solar radiation is one of the most important factors influencing the temperature distribution on bridge girder cross-sections. The bridge temperature distribution can be estimated using estimation models that incorporate solar radiation data; however, such data could be cost- or time-prohibitive to obtain. A review of literature was carried out on estimation models for solar radiation parameters, including the global solar radiation, beam solar radiation and diffuse solar radiation. Solar radiation data from eight cities in Fujian Province in southeastern China were obtained on site. Solar radiation models applicable to Fujian, China were proposed and verified using the measured data. The linear Ångström–Page model (based on sunshine duration) can be used to estimate the daily global solar radiation. The Collares-Pereira and Rabl model and the Hottel model can be used to estimate the hourly global solar radiation and the beam solar radiation, respectively. Three bridges were chosen as case study, for which the temperature distribution on girder cross-sections were monitored on site. Finite element models (FEM) of cross-sections of bridge girders were implemented using the Midas program. The temperature–time curves obtained from FEM showed very close agreement with the measured values for summertime. Ignoring the solar radiation effect would result in lower and delayed temperature peaks. However, the influence of solar radiation on the temperature distribution in winter is negligible.

Recently, China has made good progress in the construction of concrete arch bridges, which can provide development and experience for bridge engineers worldwide. Data from 313 concrete arch bridges with span lengths of no less than 100 m are studied. The investigation and analysis results indicate that both the number and the span lengths of these concrete arch bridges increased after 2007. Railway bridge applications have been increasing rapidly, while lightweight concrete arch bridges were not built anymore. The material strength of main arches has continuously improved. Ultra-high performance concrete (UHPC) is a cementitious composite material composed of an optimized gradation of granular constituents, a water-to-cementitious materials ratio less than 0.25, and a high percentage of discontinuous internal fiber reinforcement. Some UHPC arch bridges with small span lengths have been built. The cantilever method continues to be the main erection method used. The innovation-involving introduction of the Concrete-Filled Steel Tube (CFST) trussed arch into the Melan method enables construction economically, and it significantly reduces the required steps in casting of the main concrete arch. This approach has been used for all arch bridges with span lengths greater than 250 m after 2007. The core concrete is generally of higher strength grade than that of the concrete encasing the CFST. Finally, two concrete arch bridges are introduced as case studies, one has the current span record and the other would have the new span record when completed.