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The present study was conducted to clarify the flexural behaviors of the Composite Girders of a Prestressed Segmental Ultra-High-Performance Concrete (UHPC) Channel and a Reinforced Conventional Concrete Deck (PSUC-RCCD). The girders can be used as bridge superstructures with the advantages of structural efficiency, cost-effectiveness, and easy construction. A total of five specimens were tested. Three of them were PSUC-RCCD specimens, including two semi-segmental girders (the channel beams were composed of five segments with dry-joints) and one integral girder (the channel beams were integral ones without dry-joints). The two other specimens were P-UHPC girders composed of PSUC and UHPC deck slabs; one was semi-segmental and the other was integral. The flexural behaviors of the specimens were investigated, including the load-displacement curves, crack distribution, cracking moments, and ultimate flexural capacity. The study compared the influence of the segment number and deck material on the flexural behaviors of semi-segmental girders and introduced and validated methods for calculating the cracking moment and flexural capacity of both semi-segmental and integral sections in PSUC-RCCD and P-UHPC girders. The results show that the entire loading process of all the specimens can be classified into the elastic phase, the cracks development phase, and the failure phase. Compared to the integral girders, the number of segments has little effect on the flexural behavior of the semi-segmental girders, but it has a significant effect on the cracking moments. The cracking moments of the semi-segmental girders is only 0.58~0.60 of the integral girders. Reducing the strength of the deck slab by changing the material from UHPC to CC does not significantly affect their flexural behaviors. Based on the test results, this work proposes a method for predicting the cracking moment and flexural capacity of the semi-segmental girders, the results of which fit well with the test results, and it is applicable in the structural design of such members.

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.

Abstract Objective To explore the clinical outcomes and effect on intraoperative blood loss and postoperative pain of patients undergoing the retroperitoneal laparoscopic partial nephrectomy (RLPN) for complex renal tumors. Methods Fifty patients with complex renal tumor admitted to our hospital from February 2017 to February 2019 were selected as the research object and divided into the RLPN group (given the retroperitoneal laparoscopic partial nephrectomy, n = 24) and the OPN group (given the open partial nephrectomy, n = 26) by number table method to compare their various perioperative indicators and serum stress response and analyze the clinical effect of different surgical methods on the complex renal tumor. Results The clinical information of patients in both groups were not significantly different (P > 0.05); in addition to the operative time, the intraoperative blood loss, hospital stay, warm ischemia time, and numerical rating scale (NRS) scores of the RLPN group were clearly lower than those of the OPN group (P < 0.05); after treatment, patients in the RLPN group obtained significantly lower white blood cell (WBC) count, cortisol, and c-reactive protein (CRP) levels than the OPN group (P < 0.05); the renal glomerular filtration rate (GFR) of the affected side, quality of life scores, and 3-year overall survival rate of treated patients in the RLPN group were obviously higher than those in the OPN group (P < 0.05); and patients in the RPLN group had significantly lower incidence rate (P < 0.05). Conclusion Compared with OPN, RLPN is more worthy of promotion and application, because it has better treatment outcomes, significantly reduces intraoperative blood loss, alleviates the body stress response and postoperative pain, and improves the quality of life.

Flexural testing on two prestressed segmental ultra–high–performance concrete channels and reinforced conventional concrete deck composite girders (PSUC–RCCD) was carried out. One was made up of four segments with dry joints, and the other was formed of one channel beam without a dry joint. Both of them poured a conventional concrete deck slab on site. The mechanical behaviors of the girders, including the whole loading process, the crack pattern, and the failure mode were investigated and compared. The effect of the number of segments and the steel fiber volume fraction of UHPC on the bending behavior of the PSUC–RCCD girder was explored using the finite element method. This study showed that the loading process of semi-segmental and integral girders is similar; the whole loading process of the girders can be divided into the elastic phase, crack development, and the failure phase. The only notable difference between the two girders was the stage of crack development; specifically, after cracking, the stiffness of the semi-segmental girder reduced rapidly, while the “bridging effect” of the steel fibers in the integrated girder caused a slow reduction in rigidity. The flexural cracks in the semi-segmental girder were significantly less than those in the integral girder in terms of the number of cracks, and were present only at the joints. The finite element analysis showed that the number of segments had little influence on the flexural capacity of the girders, but the girders with even numbers of segments cracked earlier than those with odd segments. Increasing the steel fiber volume fraction in UHPC (ultra–high–performance concrete) had a small effect on the cracking load of the semi-segmental girders but enhanced its ultimate flexural capacity. Based on this experiment, a calculated method for estimating the flexural capacity of semi-sectional girders was proposed. The calculated values were in good agreement with the experimental and finite element values. In the preliminary design, the flexural capacity of the semi-segmental section could be estimated by multiplying the flexural capacity of the integral section by a resistance factor of 0.95.

An experimental and analytical investigation of ultrahigh-performance concrete (UHPC) plate-concrete-filled steel tubular (CFST) laced composite columns are presented in this study. A total of 11 stub specimens under axial compression are conducted to quantify the column failure mechanism. Experimental results indicate that the compressive behavior in the UHPC plate dominated the failure mechanism of the UHPC composite columns, and the failure mode is dependent on the peak strain of the UHPC plate and CFST limb. The two main parameters in the tests are the thickness of the steel tube (t) and UHPC plates (tp), which significantly enhance the bearing capacity of UHPC composite columns. Herein, the finite element standard model is established to investigate the influence of various parameters on the compressive behavior of UHPC composite columns. The diameter of the steel tube D is the most sensitive parameter affecting the structural compressive performance, while the ratio of steel reinforcing bars has an ignorable influence on the compressive strength. Based on the ultimate limit states and parametric analysis, a unified formula for predicting the strength of UHPC composite columns is proposed, which is generally in good agreement with the experimental results.

A jointless bridge could fundamentally eliminate vulnerable deck joints, thereby meeting the need for sustainable development of bridges, especially for an expressway with high-speed 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 deck-extension 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. Keywords: Jointless bridge, Deck-extension bridge, Small box girder, Longitudinal thermal movement, Temperature distribution, Average temperature

The semi-fixed dowel joint studied in this paper consists of a steel dowel with rubber sleeves and a rubber pad to connect the superstructure and the substructure and to support the main beam. This type of joint is suitably used in retrofitting a jointed bridge with high-stiffness substructure into a semi-integral bridge. This study aimed to investigate the nonlinear stiffness of the joint, which is the key parameter in the retrofitting design. Taking the real joint in a retrofitted semi-integral bridge as a prototype, tests on full-scale models were carried out, in which the wall thickness of the rubber sleeve and the thickness of the rubber pad were taken as parameters. The test results show that the wall thickness of the rubber sleeve is the main factor affecting the radial stiffness and the flexural stiffness of the semi-fixed dowel joint. With the decrease of the wall thickness of the rubber sleeve, the radial stiffness decreases while the flexural stiffness increases. However, the thickness of the rubber pad has little influence on both the radial and flexural stiffness of the joint, and its main role is only vertical loading-bearing. If the longitudinal deformation of the main beam of a bridge under maximum temperature variation is 10 mm as the allowance value of engineering design, the wall thickness of the rubber sleeve for this joint should not be less than 40 mm. At last, on the basis of experimental research and theoretical analysis, the formulas of radial stiffness and flexural stiffness are fitted; it can be used as reference for practical engineering application, or for formulation of relevant specifications.

The dynamic testing of large-scale structures continues to play a significant role in earthquake engineering research. The pseudo-dynamic test (PDT) is an experimental technique for simulating the earthquake response of structures and structural components in time domain. A Concrete Filled Steel Tube (CFST) built-up pier is a modified form of CFST laced column in which CFST members are connected with RC web in longitudinal direction and with steel tube in transverse direction. For this study, a CFST built-up pier is tested under seven different earthquake time histories having scaled PGA of 0.05g. From the experiment acceleration, velocity, displacement and load time histories are observed. The pier experienced maximum acceleration due to Imperial Valley earthquake and minimum due to Wenchuan earthquake. For the Imperial Valley earthquake the acceleration is magnified by 17 times while for the Wenchuan earthquake the acceleration is magnified by 10 times. The frequency of the pier is found to be 1.41 Hz. The result shows that this type of pier has excellent static and earthquake resistant properties.

The flexural pile foundation is used in integral abutment jointless bridges (IAJBs) in practical engineering to effectively dissipate the horizontal reciprocating deformation induced by the ambient temperature or earthquake loadings. Various types of flexural piles including the H-shaped steel pile (HP), prestressed concrete pile (PC), prestressed high-strength concrete pile (PHC) as well as the reinforcement concrete pile (RC) have been implemented in IAJBs. However, there is a lack of comprehensive studies on the flexural deformation and seismic performances of these piles. In order to investigate and compare their mechanical behaviors and seismic performances, a low-cycle pseudo-static test on several different types of piles was carried out. The test results indicated that the plastic hinge location of piles moved to a deeper pile depth with the increase of reinforcement ratio, buried pile depth and prestressing level, which led to better pile–soil interaction. The crack resistance of a concrete pile was improved as the reinforcement ratio and prestressing level increased. Moreover, the rectangular pile had a better soil–pile interaction and energy dissipation capacity than the circular pile. The inflection point of the pile deformation shifted deeper as reinforcement ratio, buried pile depth and prestressing level increased, which improved the effective length and horizontal deformation capacity of piles. The H-shaped steel pile showed a better elastic-plastic deformation capacity, ductility and energy dissipation capacity as compared to the concrete pile. Moreover, the pile having a higher bearing ratio sustained larger lateral loads whereas the surrounding soil was subjected to higher loads. Finally, new seismic design criteria of three-stage seismic fortification and five damage level for the concrete piles of IAJBs were proposed.

The accuracy of the finite element model (FEM) for concrete closed girder cross-sections is significantly influenced by thermal boundary conditions. The internal thermal boundary conditions can be simulated by inputting the convection heat transfer coefficient and the temperatures inside the cavities or by establishing air elements in the FEM. In order to analyze the influence of different simulation methods for the internal thermal boundary conditions on temperature distributions for concrete closed girder cross-sections, the temperature distributions on the cross-sections of a box girder, small box girders, and adjacent box girders were monitored, and the corresponding FEMs were implemented. By comparing the temperature data obtained from the field test and FEMs, the numerical hourly temperature curves calculated by using the measured temperatures inside the cavities provide the closest agreement with the measured results; however, the measurements of the temperatures on site are cost- and time-prohibitive. When there is a lack of measured temperatures inside the cavities, the numerical hourly temperature curves calculated by establishing air elements in the FEM provide the closest agreement. The influences of different simulation methods for the internal thermal boundary conditions on the highest hourly average effective temperatures and the trends of the vertical temperature gradients for concrete closed girder cross-sections were small. The FEM with air elements can be adopted to analyze the temperature distributions on concrete closed girder cross-sections under historically extreme temperature conditions. It can be predicted that the longitudinal thermal movement of concrete closed girders would be underestimated by considering variations in the one-year measured average effective temperature of the cross-sections or the Chinese-code-specified design effective temperature for the highway bridge structures, which are thus unconservative for engineering applications. The Chinese-code-specified design vertical temperature gradients are conservative for the bridge deck surface and unconservative for the bottom flange.

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.