压型钢板-混凝土组合楼板的承载能力受楼板叠合面的纵向抗剪能力控制。本文通过3组组合楼板的荷载试验，研 究了单跨简支组合楼板和两跨连续组合楼板的极限抗剪和抗弯性能。试验结果表明：组合楼板的极限承载能力受叠合面的纵向抗剪能力控制；与简支组合楼板相比，连续组合楼板承载能力有明显提高，跨中挠度显著减小，端部支座剪力出现滑移时与简支板端部剪力值相近，显示了连续组合板的端部滑移与剪力的关系与简支板的情况相似。但与简支组合板不同的是，连续组合板端部出现滑移后，其极限承载能力明显高于相同跨度简支板极限承载力。根据试验结果，得到了组合楼板叠合面纵向抗剪能力的计算公式。在组合楼板的承载力设计中，应对支座端部的竖向剪力进行叠合面的纵向抗剪能力验算，文中提出了连续组合楼板的承载力计算方法。

通过四组混凝土板（共10块）的荷载试验, 评定钢纤维混凝土的韧性。试验结果表明：在混凝土中采用低掺量的DRAMIX钢纤维（冷拔型），混凝土土板的能量吸收性能达到欧洲喷射混凝土规程根据隧洞衬砌变形工况制定的优级韧性指标。根据混凝土中控制掺入钢纤维的最小间距来分析，冷拔型钢纤维具有长径比大，抗拉强度高的优点，采用较低掺量的冷拔型钢纤维即可有效改善和提高混凝土的韧性与抗裂性能。

本文提出截面曲率延性K1、K2和K3的概念，来描述二类截面局部失稳对连续组合梁内力重分布的影响，采用非线性增量迭代法，分析了36组二跨连续组合梁承受均布荷载时弯矩重分布的情况。研究表明：二类截面连续组合梁的局部失稳，可采用对中间支承处弯矩调幅30%来等效。本文提出的设计方法，可避免复杂的弹塑性稳定计算。

The discusser appreciates the authors' comprehensive work to develop a potential method to repair or upgrade the existing damaged prestressed concrete (PC) girders using externally bonded carbon fiber-reinforced polymer (CFRP) laminates. A simplified theoretical prediction of the moment capacity for the girders based on ACI 440.2R appears in good agreement between the test results and the design method, as shown in Table 3. Some test findings are interesting to the discusser; however, they were not well clarified when the test results were compared with the predictions based on the design method.

In many cases, the load carrying capacity of composite slabs depends on the shear-bond resistance at the sheet-concrete interface. At the ultimate state, the tension forces in the hogging region of a continuous composite slab are mainly transferred by the negative bending reinforcement and the shear-bond resistance in the region do not significantly influence the load carrying capacity of the slab. To identify the shear-bond action in composite slabs, seven simply supported one-span composite slabs and two continuous composite slabs were tested. Different end restraints had been used in the simply supported slabs. The slabs with end anchorage of steel shear connectors were found to bear a higher shear-bond strength than that of slabs without end anchorage. The shear-bond strength was calibrated based on a linear regression of the test results of the one-span composite slabs with end anchorage. The prediction of the shear-bond resistance was also found in close agreement with the vertical shear force at the onset of the initial shear-bond slip in the two-span continuous composite slabs. It is suggested that the shear-bond slip model be reasonable to predict the shear-bond resistance of a continuous composite slab. However, the shear span of the continuous composite slabs must be related to the sagging region, which could be derived on an elastic analysis base, or simply taken as 0.8 L for the side span and 0.6 L for the interior span. At the onset of the initial shear-bond slip, the mean ratios of the vertical shear force to shear-bond resistance (Ve/Vu) are 1.065 for the one-span slabs and 1.165 for the two-span continuous composite slabs, which are on the safe side. Because of the shear-bond failure at the sheet-concrete interface, composite slabs would not be capable of developing full plastic moments in the spans.

Tests have been carried out to study the ultimate moment and incremental tendon stress of steel-concrete composite beams prestressed with external tendons under positive moment. It appears that adding prestressing by external tendons of the composite beams can significantly increase the yield load and the ultimate resistance of the beams. The deflection at the serviceability state is also reduced. However, a substantial incremental stress will develop in the tendons at the ultimate state. On the basis of the compatibility of the tendons and the composite beam at the anchorage section, and equilibrium of the internal force, the neutral axis equation of the composite beam section at the ultimate state is derived. The simplified expressions for the ultimate incremental tendon stress related to the ultimate span/deflection value for four typical external tendon cases are developed. The results compare well with the test results and the finite element analysis. A simplified method for predicting the ultimate incremental tendon force and the load carrying capacity of the composite beams prestressed with external tendons is proposed.

Initial imperfection in bolted end-plate connections is mainly induced by residual deformation of welding. Three typical initial imperfections, namely V-shape, C-shape and W-shape are identified in terms of the geometrical imperfection shapes for extended bolted end-plate connections based on a field study. Seven specimens of extended bolted end-plate connection, among which six specimens with V-shape initial imperfection and one without imperfection in the end-plates were tested, and the influence of the initial imperfection of the end-plate on the behaviour of the connections was investigated. Test results show that initial rotation stiffness of extended bolted end-plate joints decreases with increase of initial imperfection in the end-plate, however, the strength of the end-plate joints is only affected slightly by the imperfection. Besides, the thicker the end-plate is, the more reduction in the initial rotation stiffness relatively. Further parametric study on 14 extended bolted end-plate connections with three typical shapes of imperfections were conducted based on the finite element analysis. Among the three types of initial imperfection, the V-shape has the least influence, and the C-shape has the biggest influence on the initial rotation stiffness of the extended bolted end-plate joints. For initial geometrical imperfection in a V-shape, its influence on behaviour of extended bolted end-plate connections is negligible as far as the imperfection is limited to the criterion, giving H/300. The influence of initial imperfection in a W-shape on rotation stiffness should be acceptable if the initial imperfection is limited to the criterion. In the case of a C-shape initial imperfection in the end-plate, its influence on the rotation stiffness would be substantial; even it satisfies the requirement of the imperfection limit. The results of the study should be applicable to the bolted end-plate connections, whether flushed or extended end-plate beam to column joints in structural frames.

Four groups of prestressed steel-concrete composite beams with external tendons in negative moment regions were tested, and the cracking behaviours and the ultimate negative moment resistances of the composite beams were investigated experimentally. It is found that in hogging moment regions, on adding prestressing to the composite beams with external tendons, the cracking resistance of the beams can be effectively increased; however, the incremental internal tendon forces of the prestressed composite beams are rather small, and therefore can be neglected in the evaluation of the negative moment resistance of the beams. In hogging moment regions, the ultimate resistance of a composite beam prestressed with external tendons is governed by either distortional lateral buckling or local buckling, or an interactive mode composed of the two bucklings. For a beam with a compact section, the negative bending moment can reach the plastic moment when the steel section is fully plastic, and for a non-compact section, the negative bending moment is limited to the yield moment at which the compression steel flange initiates yield. The method for evaluating the buckling resistance of the composite beams is discussed, and a tentative design method based on BS5400: Part 3 is proposed to assess the buckling resistances of the prestressed composite beams.

The finite element method is applied to evaluate the effective width of a concrete slab in composite beams prestressed with external tendons. The beams studied are simply supported, with external prestressed strands straightly and draped arranged. The effective width for the prestressed composite beams evaluated based on the finite element parametric study is compared with that of plain composite beams without prestressing, and code provisions. The influence of the shear connections on the effective width and the shear slips along the beam span, as well as the incremental stresses developed in the prestressed strands, are analyzed. The behaviors of the external prestressed composite beams subject to the shrinkage and creep in the concrete slab are also discussed.

The discusser appreciates the authors' comprehensive work to develop the finite element model to evaluate behaviors of externally prestressed composite beams with deformable connections. It provides a potential approach for analyzing steel-concrete continuous composite beams up to ultimate failure.