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Floor systems constructed from slabs and beams are critical structural elements of reinforced concrete (RC) frame structures, allowing them to resist progressive collapse. To elucidate the complex effects of the slab and its thickness on the progressive-collapse resistance of RC spatial frame structures, three 1/3-scale 2 × 2 span substructure specimens, including one three-dimensional (3D) skeletal frame substructure and two 3D frame–slab substructures with different slab thicknesses, were tested in a middle-column-removal scenario. The test results indicated that the frame–slab substructure exhibited two resisting progressive-collapse stages: a primary mechanism stage, with small deformations, and a secondary mechanism stage, with large deformations. The slab contributions were separated from the floor system and quantified by comparing the results for the skeletal frame substructure and frame–slab substructure. Although there were no in-plane confinements, the slab also significantly improved the resistance against progressive collapse, owing to the compressive and tensile membrane action in the primary and secondary mechanism stages, respectively. Increasing the slab thickness increased the compressive membrane action of the slab, which significantly enhanced the progressive-collapse resistance under small deformations. However, under large deformations, the beam and slab did not work synergistically, which limited the development of secondary mechanisms against progressive collapse.

Previous quasi-static cyclic tests of shear walls, which routinely used an incremental lateral displacement test protocol with a constant axial load, failed to reflect the character of moment-shear force interaction of prototype buildings. To study the effect of the moment-shear force interaction on the seismic performance of shear walls, three identical 2-story shear wall specimens with different loading patterns were constructed at 1/2 scale, to represent the lower portion of an 11-story high-rise building, and were tested under reversed cyclic loads. The axial force, shear force and bending moment were simultaneously applied to simulate the effects of gravity loads and earthquake excitations on the prototype. The axial force and bending moment delivered from the upper structure were applied to the top of the specimens by two vertical actuators, and the shear force was applied to the specimens by two horizontal actuators. A mixed force-displacement control test program was adopted to ensure that the bending moment and the lateral shear were increased proportionally. The experimental results show that the moment-shear force interaction had a significant effect on the failure pattern, hysteretic characteristics, ductility and energy dissipation of the specimens. It is recommended that moment-shear force interaction should be considered in the loading condition of RC shear wall substructures cyclic tests.

Biocompatible polymeric materials that can degrade in response to external irradiation with high spatial and temporal control show enormous potential in the field of biomedical applications. Herein, two six-membered cyclic carbonate monomers with a light-cleavable bromocoumarin functional pendent moiety attached via a carbamate linkage were prepared from 2-amino-1,3-propanediol (serinol) and 2-(aminomethyl)-2-methylpropane-1,3-diol, respectively. A series of light-degradable polycarbonates were synthesized by organo-catalyzed ring opening polymerization (ROP) of both monomers, and meanwhile their polymerization kinetics were investigated. Upon light-induced deprotection, both types of polycarbonates degraded rapidly into low molecular-weight compounds. The results of size exclusion chromatography (SEC), nuclear magnetic resonance (NMR) spectroscopy and ultraviolet/visible (UV/VIS) spectroscopy confirmed the polymer structures and the light-induced degradation behavior. The photo-cleavage rates of bromocoumarin pendent groups and the degradation rates of the polymers were strongly dependent on polymer structures and used solvents.

Nanoparticles (NP) have gained importance as drug delivery systems for pharmaceutical challenging drugs. Their size properties allow passive targeting of cancer tissue by exploiting the enhanced permeability and retention (EPR) effect. Furthermore, surface modifications enable an active drug targeting for diseased regions in the human body. Besides the advantages, the drug release from commonly used biodegradable NP is mostly depending on physiological circumstances. Hence, there is a need for a more controllable drug release. The use of light-responsive polymers is an innovative conception enabling a more distinct drug release by an external light stimulus. The idea provides potential for an increase in efficiency and safety of local therapies. In this study, innovative light-sensitive NP were investigated for a photodynamic therapy (PDT) of gastrointestinal tumors. Nanoparticles based on a newly developed light-responsive polycarbonate (LrPC) and poly(lactic-co-glycolic-acid) (PLGA) were loaded with the approved photosensitizer 5,10,15,20-tetrakis(m-hydroxyphenyl)chlorin (mTHPC). Mucus penetrating properties were obtained by surface PEGylation of the nanoparticles either by using LrPC in combination with a PEGylated PLA (PEG-PLA) or by a combination with PEGylated LrPC (LrPC-PEG). Cytotoxic potential in dependency of a light-induced drug release was investigated in different cytotoxicity assays. Intracellular accumulation in mucus producing colon-carcinoma cell line HT-29-MTX was analysed by HPLC and confocal laser microscopy.

Nanoparticles based on biodegradable polymers are well-known as approved carrier systems for a diversity of drugs. Despite their advantages, such as the option of an active drug targeting or the physicochemical protection of instable payloads, the controlled drug release often underlies intra- and interindividual influences and is therefore difficult to predict. To circumvent this limitation, the release behavior can be optimized using light-responsive materials for the nanoparticle preparation. The resulting light-responsive nanoparticles are able to release the embedded drug after an external light-stimulus, thereby increasing efficacy and safety of the therapy. In the present study light-responsive self-immolative polymers were used for the nanoparticle manufacturing. Light-responsive polycarbonates (LrPC) as well as PEGylated LrPC (LrPC-PEG) were synthesized via ring-opening polymerization of trimethylene carbonate-based monomers and fully physico-chemically characterized. Light-responsive nano formulations were obtained by blending LrPC or (LrPC-PEG) with the FDA-approved polymer poly(DL-lactide-co-glycolide) (PLGA). The nanoparticles were loaded with the photosensitizer 5,10,15,20-tetrakis(m-hydroxyphenyl)chlorin (mTHPC). The light-induced nanoparticle degradation was analyzed as well as the drug release behavior with and without illumination. Furthermore, biological safety of the degradation products was investigated in an in vitro cell culture study.

In this work, poly(dimethylacrylamide)-b-poly(trimethylene carbonate) (PDMAAm-b-PTMC) block copolymers containing a pH-sensitive imine linkage were successfully synthesized by combination of ring-opening polymerization (ROP) and reversible addition–fragmentation chain transfer (RAFT) polymerization. A variety of vanillin terminated PTMC block copolymers were prepared by ROP of trimethylene carbonate (TMC) initiated by modified vanillin in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as an organo-catalyst. The analysis of the resultant homopolymers by 1H NMR spectroscopy, size exclusion chromatography (SEC) and ESI-ToF masspectrometry (ESI-ToF-MS) revealed the excellent control of molar masses (Mn up to 14 000 g mol−1), dispersities (ĐM < 1.15) and end groups. The PTMC homopolymer was subsequently end-capped with an amino functionalized RAFT-agent leading to a macroinitiator containing imine group. Using this macroinitiator, PDMAAm-b-PTMC block copolymers with various molar masses were successfully prepared. In aqueous solution at pH 7.4, micelles could be formed by self-assembly of the amphiphilic block copolymer using a dialysis method. The hydrodynamic diameter (Dh) of the micelles was 76.3 ± 2.4 nm with a polydispersity index (PDI) of 0.179 ± 0.002. Under weak acidic conditions (pH 6.0), the hydrophilic PDMAAm block could be cleaved from micelles by hydrolysis of the imine linkage, while PTMC nanoparticles formed in situ with an average size of 149.8 ± 4.5 nm (PDI = 0.287 ± 0.007). Based on our strategy, these pH-cleavable PTMC-based amphiphilic block copolymers will expand the range of biodegradable synthetic polymers available for potential biomedical applications, such as controlled drug and gene delivery.

In this work, a variety of hyperbranched polymers (HBPs), such as hyperbranched polycarbonates, polyesters, polyurethanes and polyacetals, was successfully synthesized from castor oil and soybean oil based monomers via a A2 + B3 polycondensation. First, B3 monomer triols (TriOL), trialdehydes (TriAD), and tricarboxylic acids (TriAC) were obtained by ozonolysis of castor oil and soybean oil with following reductive or oxidative treatment. Their structures were characterized by 1H NMR and ATR-FTIR spectroscopy as well as electrospray ionization-Time of Flight-mass spectrometry. These trifunctional B3 monomers were applied in the preparation of HBPs. The resulting HBPs had number averaged molar mass (Mn) up to 9400 g/mol and weight averaged molar mass (Mw) up to 40,000 g/mol. Through adjusting the initial molar ratio of A2 to B3 monomers, hydroxyl terminated (from TriOL monomers) or carboxylic acid (from TriAC monomers) terminated HBPs could be obtained. All the HBPs were characterized by 1H NMR, size exclusion chromatography, and DSC. These HBPs are potential candidates for the synthesis of cross-linked polymeric materials or in biomedical applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 2104–2114

A new eco-friendly strategy for the preparation of linear and hyperbranched polycarbonates was developed. Our work referred to a one-pot condensation polymerization of various alcohols (diols and triols) with equivalent amounts of eco-friendly dimethyl carbonate (DMC) at 120 °C, atmospheric pressure and in 1,4-dioxane solution using 4-dimethylaminopyridine (DMAP) or lithium acetylacetonate (LiAcac) as a catalyst. Polymer chains were built by pure transesterification of hydroxyl and methyl carbonate chain ends, and the single byproduct (methanol) was removed using a pressure-equalized addition funnel filled with 4 A molecular sieves as the crucial equipment in this work. Using this strategy, hyperbranched polycarbonates with high molar masses (Mn up to 10 000 g mol−1 and Mw up to 64 000 g mol−1) and high hydroxyl end group contents (up to 94%) were successfully prepared using dimethyl carbonate instead of toxic phosgene or phosgene-based monomers for the first time. In addition, linear aliphatic polycarbonates of various diols were also synthesized with Mn up to 16 000 g mol−1 and low molar mass distributions (ĐM < 1.70). Another eco-friendly aspect of this work was the use of equimolar amounts of DMC to avoid waste and the disposal of excess DMC; in a classic 2-step polycondensation for polycarbonate synthesis excess DMC is a prerequisite in order to obtain high molar masses.

Masonry-infilled timber frames are widely used for residential houses in underdeveloped rural and mountainous areas in southwestern China. As suggested by the identified dynamic properties of three typical timber houses of this type, the structure can be taken as a dual system in which the masonry infills provide the most lateral resistance, while the timber frame withstands the vertical loads. The seismic damage to the houses, either of masonry or of masonry-infilled timber structures, in a small town near the epicenter of the 2013 M7.0 Lushan earthquake in southwestern China was inspected and compared, in order to show that the masonry-infilled timber houses exhibited much better seismic performance than the unreinforced masonry ones during the earthquake.

On April 14, 2010, a devastating Ms 7.1 earthquake occurred in Yushu, China. In the most severely struck area of Jiegu Town, approximately 94 % of the structures were damaged. A seismic intensity map was obtained based on field investigation data of structural damage in 63 residential areas, and the differences in structural damage in four intensity regions were quantitatively compared using a seismic capacity index and a damage index. The typical damage for five types of structures in the epicentral area of Jiegu Town was described and summarized in detail. Some recommendations for improving seismic capacity of buildings are provided; they include avoiding mountainous topography, non-uniform materials, and irregular layouts, as well as considering an appropriate arrangement of structural columns and belt courses for hollow concrete block and brick masonry structures. This paper provides valuable information for structural seismic design, post-earthquake reconstruction, and related work.

A new structural system called a stepped wall-frame structure is proposed in this study to solve the bottom yielding problem of RC frames, which widely occurred during previous earthquakes such as the Wenchuan and Yushu earthquakes in China. A 1/5 scale ordinary RC frame model and a stepped wall-frame model were subjected to shake table motions together to study the seismic behavior of the new structural system. This paper presents the dynamic characteristics, the seismic responses and the failure and collapse mechanism of the two models under low, moderate and high intensity shaking. The test results and further analysis demonstrate that the seismic performance of stepped wall-frame structures is superior to ordinary RC frames in terms of the well-controlled deformation pattern and more uniformly distributed damage. The stepped wall can effectively suppress the bottom yielding mechanism, and is simple, economical and practical for engineering practice.

In the present work, a new and facile strategy for the synthesis of light-responsive polyurethanes (LrPUs) based on serinol with o-nitrobenzyl pendent groups is developed. Stable monodisperse nanoparticles from these LrPUs can be formulated reproducibly in a simple manner, which is shown by dynamic light scattering (DLS) measurements. Upon irradiation with UV light, both polymers and nanoparticles undergo rapid degradation, which is investigated by DLS, scanning electron microscopy, size exclusion chromatography, and UV-vis spectroscopy. The nanoparticles are also employed for the encapsulation of the model drug Nile Red, and by exposure to UV light, a burst release of the payload is detected via fluorescence spectroscopy. This strategy can be easily applied to the straightforward synthesis of various new serinol-based monomers with different stimuli-responsive properties and therefore expand the family of biodegradable polymers.

The outline and typical characteristics of damages to building in Jiangyou city and Anxian county (intensity VIII), Mianyang city and Deyang city (intensity VII) are introduced in the paper. The damage ratios, based on the sample statistics of multi-story brick buildings together with multi-story brick buildings with RC frame at first story (BBF), are presented. Then some typical damages, such as horizontal cricks of brick masonry buildings, X-shaped cricks on the walls under windows, the damages to columns, beams and infill walls of frame buildings and the damage to half circle-shaped masonry walls, are discussed.